Squashed 'third_party/protobuf/' content from commit e35e248

Change-Id: I6cbe123d09fe50fdcad0e51466665daeee7433c7
git-subtree-dir: third_party/protobuf
git-subtree-split: e35e24800fb8d694bdeea5fd63dc7d1b14d68723
diff --git a/src/google/protobuf/util/field_comparator.cc b/src/google/protobuf/util/field_comparator.cc
new file mode 100644
index 0000000..9f61326
--- /dev/null
+++ b/src/google/protobuf/util/field_comparator.cc
@@ -0,0 +1,188 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: ksroka@google.com (Krzysztof Sroka)
+
+#include <google/protobuf/util/field_comparator.h>
+
+#include <string>
+
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/message.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/mathlimits.h>
+#include <google/protobuf/stubs/mathutil.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+FieldComparator::FieldComparator() {}
+FieldComparator::~FieldComparator() {}
+
+DefaultFieldComparator::DefaultFieldComparator()
+    : float_comparison_(EXACT),
+      treat_nan_as_equal_(false),
+      has_default_tolerance_(false) {
+}
+
+DefaultFieldComparator::~DefaultFieldComparator() {}
+
+FieldComparator::ComparisonResult DefaultFieldComparator::Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context) {
+  const Reflection* reflection_1 = message_1.GetReflection();
+  const Reflection* reflection_2 = message_2.GetReflection();
+
+  switch (field->cpp_type()) {
+#define COMPARE_FIELD(METHOD)                                              \
+    if (field->is_repeated()) {                                            \
+      return ResultFromBoolean(Compare##METHOD(                            \
+          *field,                                                          \
+          reflection_1->GetRepeated##METHOD(message_1, field, index_1),    \
+          reflection_2->GetRepeated##METHOD(message_2, field, index_2)));  \
+    } else {                                                               \
+      return ResultFromBoolean(Compare##METHOD(                            \
+          *field,                                                          \
+          reflection_1->Get##METHOD(message_1, field),                     \
+          reflection_2->Get##METHOD(message_2, field)));                   \
+    }                                                                      \
+    break;  // Make sure no fall-through is introduced.
+
+    case FieldDescriptor::CPPTYPE_BOOL:
+      COMPARE_FIELD(Bool);
+    case FieldDescriptor::CPPTYPE_DOUBLE:
+      COMPARE_FIELD(Double);
+    case FieldDescriptor::CPPTYPE_ENUM:
+      COMPARE_FIELD(Enum);
+    case FieldDescriptor::CPPTYPE_FLOAT:
+      COMPARE_FIELD(Float);
+    case FieldDescriptor::CPPTYPE_INT32:
+      COMPARE_FIELD(Int32);
+    case FieldDescriptor::CPPTYPE_INT64:
+      COMPARE_FIELD(Int64);
+    case FieldDescriptor::CPPTYPE_STRING:
+      COMPARE_FIELD(String);
+    case FieldDescriptor::CPPTYPE_UINT32:
+      COMPARE_FIELD(UInt32);
+    case FieldDescriptor::CPPTYPE_UINT64:
+      COMPARE_FIELD(UInt64);
+
+#undef COMPARE_FIELD
+
+    case FieldDescriptor::CPPTYPE_MESSAGE:
+      return RECURSE;
+
+    default:
+      GOOGLE_LOG(FATAL) << "No comparison code for field " << field->full_name()
+                 << " of CppType = " << field->cpp_type();
+      return DIFFERENT;
+  }
+}
+
+void DefaultFieldComparator::SetDefaultFractionAndMargin(double fraction,
+                                                         double margin) {
+  default_tolerance_ = Tolerance(fraction, margin);
+  has_default_tolerance_ = true;
+}
+
+void DefaultFieldComparator::SetFractionAndMargin(const FieldDescriptor* field,
+                                                  double fraction,
+                                                  double margin) {
+  GOOGLE_CHECK(FieldDescriptor::CPPTYPE_FLOAT == field->cpp_type() ||
+        FieldDescriptor::CPPTYPE_DOUBLE == field->cpp_type())
+      << "Field has to be float or double type. Field name is: "
+      << field->full_name();
+  map_tolerance_[field] = Tolerance(fraction, margin);
+}
+
+bool DefaultFieldComparator::CompareDouble(const FieldDescriptor& field,
+                                           double value_1, double value_2) {
+  return CompareDoubleOrFloat(field, value_1, value_2);
+}
+
+bool DefaultFieldComparator::CompareEnum(const FieldDescriptor& field,
+                                         const EnumValueDescriptor* value_1,
+                                         const EnumValueDescriptor* value_2) {
+  return value_1->number() == value_2->number();
+}
+
+bool DefaultFieldComparator::CompareFloat(const FieldDescriptor& field,
+                                          float value_1, float value_2) {
+  return CompareDoubleOrFloat(field, value_1, value_2);
+}
+
+template<typename T>
+bool DefaultFieldComparator::CompareDoubleOrFloat(const FieldDescriptor& field,
+                                                  T value_1, T value_2) {
+  if (value_1 == value_2) {
+    // Covers +inf and -inf (which are not within margin or fraction of
+    // themselves), and is a shortcut for finite values.
+    return true;
+  } else if (float_comparison_ == EXACT) {
+    if (treat_nan_as_equal_ &&
+        MathLimits<T>::IsNaN(value_1) && MathLimits<T>::IsNaN(value_2)) {
+      return true;
+    }
+    return false;
+  } else {
+    if (treat_nan_as_equal_ &&
+        MathLimits<T>::IsNaN(value_1) && MathLimits<T>::IsNaN(value_2)) {
+      return true;
+    }
+    // float_comparison_ == APPROXIMATE covers two use cases.
+    Tolerance* tolerance = FindOrNull(map_tolerance_, &field);
+    if (tolerance == NULL && has_default_tolerance_) {
+      tolerance = &default_tolerance_;
+    }
+    if (tolerance == NULL) {
+      return MathUtil::AlmostEquals(value_1, value_2);
+    } else {
+      // Use user-provided fraction and margin. Since they are stored as
+      // doubles, we explicitely cast them to types of values provided. This
+      // is very likely to fail if provided values are not numeric.
+      return MathUtil::WithinFractionOrMargin(
+          value_1, value_2, static_cast<T>(tolerance->fraction),
+          static_cast<T>(tolerance->margin));
+    }
+  }
+}
+
+FieldComparator::ComparisonResult DefaultFieldComparator::ResultFromBoolean(
+    bool boolean_result) const {
+  return boolean_result ? FieldComparator::SAME : FieldComparator::DIFFERENT;
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/field_comparator.h b/src/google/protobuf/util/field_comparator.h
new file mode 100644
index 0000000..8b83c69
--- /dev/null
+++ b/src/google/protobuf/util/field_comparator.h
@@ -0,0 +1,259 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: ksroka@google.com (Krzysztof Sroka)
+
+#ifndef GOOGLE_PROTOBUF_UTIL_FIELD_COMPARATOR_H__
+#define GOOGLE_PROTOBUF_UTIL_FIELD_COMPARATOR_H__
+
+#include <map>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+
+class Message;
+class EnumValueDescriptor;
+class FieldDescriptor;
+
+namespace util {
+
+class FieldContext;
+
+// Base class specifying the interface for comparing protocol buffer fields.
+// Regular users should consider using or subclassing DefaultFieldComparator
+// rather than this interface.
+// Currently, this does not support comparing unknown fields.
+class LIBPROTOBUF_EXPORT FieldComparator {
+ public:
+  FieldComparator();
+  virtual ~FieldComparator();
+
+  enum ComparisonResult {
+    SAME,       // Compared fields are equal. In case of comparing submessages,
+                // user should not recursively compare their contents.
+    DIFFERENT,  // Compared fields are different. In case of comparing
+                // submessages, user should not recursively compare their
+                // contents.
+    RECURSE,    // Compared submessages need to be compared recursively.
+                // FieldComparator does not specify the semantics of recursive
+                // comparison. This value should not be returned for simple
+                // values.
+  };
+
+  // Compares the values of a field in two protocol buffer messages.
+  // Returns SAME or DIFFERENT for simple values, and SAME, DIFFERENT or RECURSE
+  // for submessages. Returning RECURSE for fields not being submessages is
+  // illegal.
+  // In case the given FieldDescriptor points to a repeated field, the indices
+  // need to be valid. Otherwise they should be ignored.
+  //
+  // FieldContext contains information about the specific instances of the
+  // fields being compared, versus FieldDescriptor which only contains general
+  // type information about the fields.
+  virtual ComparisonResult Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FieldComparator);
+};
+
+// Basic implementation of FieldComparator.  Supports four modes of floating
+// point value comparison: exact, approximate using MathUtil::AlmostEqual
+// method, and arbitrarilly precise using MathUtil::WithinFractionOrMargin.
+class LIBPROTOBUF_EXPORT DefaultFieldComparator : public FieldComparator {
+ public:
+  enum FloatComparison {
+     EXACT,               // Floats and doubles are compared exactly.
+     APPROXIMATE,         // Floats and doubles are compared using the
+                          // MathUtil::AlmostEqual method or
+                          // MathUtil::WithinFractionOrMargin method.
+     // TODO(ksroka): Introduce third value to differenciate uses of AlmostEqual
+     //               and WithinFractionOrMargin.
+  };
+
+  // Creates new comparator with float comparison set to EXACT.
+  DefaultFieldComparator();
+
+  virtual ~DefaultFieldComparator();
+
+  virtual ComparisonResult Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context);
+
+  void set_float_comparison(FloatComparison float_comparison) {
+    float_comparison_ = float_comparison;
+  }
+
+  FloatComparison float_comparison() const {
+    return float_comparison_;
+  }
+
+  // Set whether the FieldComparator shall treat floats or doubles that are both
+  // NaN as equal (treat_nan_as_equal = true) or as different
+  // (treat_nan_as_equal = false). Default is treating NaNs always as different.
+  void set_treat_nan_as_equal(bool treat_nan_as_equal) {
+    treat_nan_as_equal_ = treat_nan_as_equal;
+  }
+
+  bool treat_nan_as_equal() const {
+    return treat_nan_as_equal_;
+  }
+
+  // Sets the fraction and margin for the float comparison of a given field.
+  // Uses MathUtil::WithinFractionOrMargin to compare the values.
+  //
+  // REQUIRES: field->cpp_type == FieldDescriptor::CPPTYPE_DOUBLE or
+  //           field->cpp_type == FieldDescriptor::CPPTYPE_FLOAT
+  // REQUIRES: float_comparison_ == APPROXIMATE
+  void SetFractionAndMargin(const FieldDescriptor* field, double fraction,
+                            double margin);
+
+  // Sets the fraction and margin for the float comparison of all float and
+  // double fields, unless a field has been given a specific setting via
+  // SetFractionAndMargin() above.
+  // Uses MathUtil::WithinFractionOrMargin to compare the values.
+  //
+  // REQUIRES: float_comparison_ == APPROXIMATE
+  void SetDefaultFractionAndMargin(double fraction, double margin);
+
+ private:
+  // Defines the tolerance for floating point comparison (fraction and margin).
+  struct Tolerance {
+    double fraction;
+    double margin;
+    Tolerance()
+        : fraction(0.0),
+          margin(0.0) {}
+    Tolerance(double f, double m)
+        : fraction(f),
+          margin(m) {}
+  };
+
+  // Defines the map to store the tolerances for floating point comparison.
+  typedef map<const FieldDescriptor*, Tolerance> ToleranceMap;
+
+  // The following methods get executed when CompareFields is called for the
+  // basic types (instead of submessages). They return true on success. One
+  // can use ResultFromBoolean() to convert that boolean to a ComparisonResult
+  // value.
+  bool CompareBool(const google::protobuf::FieldDescriptor& field,
+                   bool value_1, bool value_2) {
+    return value_1 == value_2;
+  }
+
+  // Uses CompareDoubleOrFloat, a helper function used by both CompareDouble and
+  // CompareFloat.
+  bool CompareDouble(const google::protobuf::FieldDescriptor& field,
+                     double value_1, double value_2);
+
+  bool CompareEnum(const google::protobuf::FieldDescriptor& field,
+                   const EnumValueDescriptor* value_1,
+                   const EnumValueDescriptor* value_2);
+
+  // Uses CompareDoubleOrFloat, a helper function used by both CompareDouble and
+  // CompareFloat.
+  bool CompareFloat(const google::protobuf::FieldDescriptor& field,
+                    float value_1, float value_2);
+
+  bool CompareInt32(const google::protobuf::FieldDescriptor& field,
+                    int32 value_1, int32 value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareInt64(const google::protobuf::FieldDescriptor& field,
+                    int64 value_1, int64 value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareString(const google::protobuf::FieldDescriptor& field,
+                     const string& value_1, const string& value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareUInt32(const google::protobuf::FieldDescriptor& field,
+                     uint32 value_1, uint32 value_2) {
+    return value_1 == value_2;
+  }
+
+  bool CompareUInt64(const google::protobuf::FieldDescriptor& field,
+                     uint64 value_1, uint64 value_2) {
+    return value_1 == value_2;
+  }
+
+  // This function is used by CompareDouble and CompareFloat to avoid code
+  // duplication. There are no checks done against types of the values passed,
+  // but it's likely to fail if passed non-numeric arguments.
+  template<typename T>
+  bool CompareDoubleOrFloat(const google::protobuf::FieldDescriptor& field,
+                            T value_1, T value_2);
+
+  // Returns FieldComparator::SAME if boolean_result is true and
+  // FieldComparator::DIFFERENT otherwise.
+  ComparisonResult ResultFromBoolean(bool boolean_result) const;
+
+  FloatComparison float_comparison_;
+
+  // If true, floats and doubles that are both NaN are considered to be
+  // equal. Otherwise, two floats or doubles that are NaN are considered to be
+  // different.
+  bool treat_nan_as_equal_;
+
+  // True iff default_tolerance_ has been explicitly set.
+  //
+  // If false, then the default tolerance for flaots and doubles is that which
+  // is used by MathUtil::AlmostEquals().
+  bool has_default_tolerance_;
+
+  // Default float/double tolerance. Only meaningful if
+  // has_default_tolerance_ == true.
+  Tolerance default_tolerance_;
+
+  // Field-specific float/double tolerances, which override any default for
+  // those particular fields.
+  ToleranceMap map_tolerance_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DefaultFieldComparator);
+};
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_FIELD_COMPARATOR_H__
diff --git a/src/google/protobuf/util/field_comparator_test.cc b/src/google/protobuf/util/field_comparator_test.cc
new file mode 100644
index 0000000..23f7d51
--- /dev/null
+++ b/src/google/protobuf/util/field_comparator_test.cc
@@ -0,0 +1,489 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: ksroka@google.com (Krzysztof Sroka)
+
+#include <google/protobuf/util/field_comparator.h>
+
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/stubs/mathutil.h>
+// This gtest header is put after mathutil.h intentionally. We have to do
+// this because mathutil.h includes mathlimits.h which requires cmath not
+// being included to compile on some versions of gcc:
+//   https://github.com/google/protobuf/blob/818c5eee08840355d70d2f3bdf1a2f17986a5e70/src/google/protobuf/stubs/mathlimits.h#L48
+// and the opensource version gtest.h header includes cmath transitively
+// somehow.
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+
+using protobuf_unittest::TestAllTypes;
+
+class DefaultFieldComparatorTest : public ::testing::Test {
+ protected:
+  void SetUp() {
+    descriptor_ = TestAllTypes::descriptor();
+  }
+
+  const Descriptor* descriptor_;
+  DefaultFieldComparator comparator_;
+  TestAllTypes message_1_;
+  TestAllTypes message_2_;
+};
+
+TEST_F(DefaultFieldComparatorTest, RecursesIntoGroup) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optionalgroup");
+  EXPECT_EQ(FieldComparator::RECURSE,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, RecursesIntoNestedMessage) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_nested_message");
+  EXPECT_EQ(FieldComparator::RECURSE,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, RecursesIntoForeignMessage) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_foreign_message");
+  EXPECT_EQ(FieldComparator::RECURSE,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, Int32Comparison) {
+  const FieldDescriptor* field = descriptor_->FindFieldByName("optional_int32");
+  message_1_.set_optional_int32(1);
+  message_2_.set_optional_int32(1);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_int32(-1);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, Int64Comparison) {
+  const FieldDescriptor* field = descriptor_->FindFieldByName("optional_int64");
+  message_1_.set_optional_int64(1L);
+  message_2_.set_optional_int64(1L);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_int64(-1L);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, UInt32Comparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_uint32");
+  message_1_.set_optional_uint32(1);
+  message_2_.set_optional_uint32(1);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_uint32(2);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, UInt64Comparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_uint64");
+  message_1_.set_optional_uint64(1L);
+  message_2_.set_optional_uint64(1L);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_uint64(2L);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, BooleanComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_bool");
+  message_1_.set_optional_bool(true);
+  message_2_.set_optional_bool(true);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_bool(false);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, EnumComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_nested_enum");
+  message_1_.set_optional_nested_enum(TestAllTypes::BAR);
+  message_2_.set_optional_nested_enum(TestAllTypes::BAR);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_nested_enum(TestAllTypes::BAZ);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, StringComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("optional_string");
+  message_1_.set_optional_string("foo");
+  message_2_.set_optional_string("foo");
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+
+  message_2_.set_optional_string("bar");
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, FloatingPointComparisonExact) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(0.1f);
+  message_2_.set_optional_float(0.1f);
+  message_1_.set_optional_double(0.1);
+  message_2_.set_optional_double(0.1);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  message_2_.set_optional_float(0.2f);
+  message_2_.set_optional_double(0.2);
+
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, FloatingPointComparisonApproximate) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(2.300005f);
+  message_2_.set_optional_float(2.300006f);
+  message_1_.set_optional_double(2.3000000000000003);
+  message_2_.set_optional_double(2.3000000000000007);
+
+  // Approximate comparison depends on MathUtil, so we assert on MathUtil
+  // results first to check if that's where the failure was introduced.
+  ASSERT_NE(message_1_.optional_float(), message_2_.optional_float());
+  ASSERT_NE(message_1_.optional_double(), message_2_.optional_double());
+  ASSERT_TRUE(MathUtil::AlmostEquals(message_1_.optional_float(),
+                                     message_2_.optional_float()));
+  ASSERT_TRUE(MathUtil::AlmostEquals(message_1_.optional_double(),
+                                     message_2_.optional_double()));
+
+  // DefaultFieldComparator's default float comparison mode is EXACT.
+  ASSERT_EQ(DefaultFieldComparator::EXACT, comparator_.float_comparison());
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest, FloatingPointComparisonTreatNaNsAsEqual) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(MathLimits<float>::kNaN);
+  message_2_.set_optional_float(MathLimits<float>::kNaN);
+  message_1_.set_optional_double(MathLimits<double>::kNaN);
+  message_2_.set_optional_double(MathLimits<double>::kNaN);
+
+  // DefaultFieldComparator's default float comparison mode is EXACT with
+  // treating NaNs as different.
+  ASSERT_EQ(DefaultFieldComparator::EXACT, comparator_.float_comparison());
+  ASSERT_EQ(false, comparator_.treat_nan_as_equal());
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  comparator_.set_treat_nan_as_equal(true);
+  ASSERT_EQ(true, comparator_.treat_nan_as_equal());
+  comparator_.set_float_comparison(DefaultFieldComparator::EXACT);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest,
+       FloatingPointComparisonWithinFractionOrMargin) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(100.0f);
+  message_2_.set_optional_float(109.9f);
+  message_1_.set_optional_double(100.0);
+  message_2_.set_optional_double(109.9);
+
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should fail since the fraction is too low.
+  comparator_.SetFractionAndMargin(field_float, 0.01, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.01, 0.0);
+
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should fail since the margin is too low.
+  comparator_.SetFractionAndMargin(field_float, 0.0, 9.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 9.0);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should succeed since the fraction is high enough.
+  comparator_.SetFractionAndMargin(field_float, 0.2, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.2, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Should succeed since the margin is high enough.
+  comparator_.SetFractionAndMargin(field_float, 0.0, 10.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 10.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Setting values for one of the fields should not affect the other.
+  comparator_.SetFractionAndMargin(field_double, 0.0, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // +inf should be equal even though they are not technically within margin or
+  // fraction.
+  message_1_.set_optional_float(numeric_limits<float>::infinity());
+  message_2_.set_optional_float(numeric_limits<float>::infinity());
+  message_1_.set_optional_double(numeric_limits<double>::infinity());
+  message_2_.set_optional_double(numeric_limits<double>::infinity());
+  comparator_.SetFractionAndMargin(field_float, 0.0, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // -inf should be equal even though they are not technically within margin or
+  // fraction.
+  message_1_.set_optional_float(-numeric_limits<float>::infinity());
+  message_2_.set_optional_float(-numeric_limits<float>::infinity());
+  message_1_.set_optional_double(-numeric_limits<double>::infinity());
+  message_2_.set_optional_double(-numeric_limits<double>::infinity());
+  comparator_.SetFractionAndMargin(field_float, 0.0, 0.0);
+  comparator_.SetFractionAndMargin(field_double, 0.0, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+TEST_F(DefaultFieldComparatorTest,
+       FloatingPointComparisonWithinDefaultFractionOrMargin) {
+  const FieldDescriptor* field_float =
+      descriptor_->FindFieldByName("optional_float");
+  const FieldDescriptor* field_double =
+      descriptor_->FindFieldByName("optional_double");
+
+  message_1_.set_optional_float(100.0f);
+  message_2_.set_optional_float(109.9f);
+  message_1_.set_optional_double(100.0);
+  message_2_.set_optional_double(109.9);
+
+  comparator_.set_float_comparison(DefaultFieldComparator::APPROXIMATE);
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Set default fraction and margin.
+  comparator_.SetDefaultFractionAndMargin(0.01, 0.0);
+
+  // Float comparisons should fail since the fraction is too low.
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Set field-specific fraction and margin for one field (field_float) but not
+  // the other (field_double)
+  comparator_.SetFractionAndMargin(field_float, 0.2, 0.0);
+
+  // The field with the override should succeed, since its field-specific
+  // fraction is high enough.
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  // The field with no override should fail, since the default fraction is too
+  // low
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // Set the default fraction and margin high enough so that fields that use
+  // the default should succeed
+  comparator_.SetDefaultFractionAndMargin(0.2, 0.0);
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+
+  // The field with an override should still be OK
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+
+  // Set fraction and margin for the field with an override to be too low
+  comparator_.SetFractionAndMargin(field_float, 0.01, 0.0);
+
+  // Now our default is high enough but field_float's override is too low.
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_,
+                                field_float, -1, -1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_,
+                                field_double, -1, -1, NULL));
+}
+
+// Simple test checking whether we compare values at correct indices.
+TEST_F(DefaultFieldComparatorTest, RepeatedFieldComparison) {
+  const FieldDescriptor* field =
+      descriptor_->FindFieldByName("repeated_string");
+
+  message_1_.add_repeated_string("foo");
+  message_1_.add_repeated_string("bar");
+  message_2_.add_repeated_string("bar");
+  message_2_.add_repeated_string("baz");
+
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, 0, 0, NULL));
+  EXPECT_EQ(FieldComparator::DIFFERENT,
+            comparator_.Compare(message_1_, message_2_, field, 1, 1, NULL));
+  EXPECT_EQ(FieldComparator::SAME,
+            comparator_.Compare(message_1_, message_2_, field, 1, 0, NULL));
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace
+}  // namespace google
diff --git a/src/google/protobuf/util/field_mask_util.cc b/src/google/protobuf/util/field_mask_util.cc
new file mode 100644
index 0000000..c59f43aa
--- /dev/null
+++ b/src/google/protobuf/util/field_mask_util.cc
@@ -0,0 +1,418 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/field_mask_util.h>
+
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+using google::protobuf::FieldMask;
+
+string FieldMaskUtil::ToString(const FieldMask& mask) {
+  return Join(mask.paths(), ",");
+}
+
+void FieldMaskUtil::FromString(StringPiece str, FieldMask* out) {
+  out->Clear();
+  vector<string> paths = Split(str, ",");
+  for (int i = 0; i < paths.size(); ++i) {
+    if (paths[i].empty()) continue;
+    out->add_paths(paths[i]);
+  }
+}
+
+bool FieldMaskUtil::InternalIsValidPath(const Descriptor* descriptor,
+                                        StringPiece path) {
+  vector<string> parts = Split(path, ".");
+  for (int i = 0; i < parts.size(); ++i) {
+    const string& field_name = parts[i];
+    if (descriptor == NULL) {
+      return false;
+    }
+    const FieldDescriptor* field = descriptor->FindFieldByName(field_name);
+    if (field == NULL) {
+      return false;
+    }
+    if (!field->is_repeated() &&
+        field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      descriptor = field->message_type();
+    } else {
+      descriptor = NULL;
+    }
+  }
+  return true;
+}
+
+void FieldMaskUtil::InternalGetFieldMaskForAllFields(
+    const Descriptor* descriptor, FieldMask* out) {
+  for (int i = 0; i < descriptor->field_count(); ++i) {
+    out->add_paths(descriptor->field(i)->name());
+  }
+}
+
+namespace {
+// A FieldMaskTree represents a FieldMask in a tree structure. For example,
+// given a FieldMask "foo.bar,foo.baz,bar.baz", the FieldMaskTree will be:
+//
+//   [root] -+- foo -+- bar
+//           |       |
+//           |       +- baz
+//           |
+//           +- bar --- baz
+//
+// In the tree, each leaf node represents a field path.
+class FieldMaskTree {
+ public:
+  FieldMaskTree();
+  ~FieldMaskTree();
+
+  void MergeFromFieldMask(const FieldMask& mask);
+  void MergeToFieldMask(FieldMask* mask);
+
+  // Add a field path into the tree. In a FieldMask, each field path matches
+  // the specified field and also all its sub-fields. If the field path to
+  // add is a sub-path of an existing field path in the tree (i.e., a leaf
+  // node), it means the tree already matches the given path so nothing will
+  // be added to the tree. If the path matches an existing non-leaf node in the
+  // tree, that non-leaf node will be turned into a leaf node with all its
+  // children removed because the path matches all the node's children.
+  void AddPath(const string& path);
+
+  // Calculate the intersection part of a field path with this tree and add
+  // the intersection field path into out.
+  void IntersectPath(const string& path, FieldMaskTree* out);
+
+  // Merge all fields specified by this tree from one message to another.
+  void MergeMessage(const Message& source,
+                    const FieldMaskUtil::MergeOptions& options,
+                    Message* destination) {
+    // Do nothing if the tree is empty.
+    if (root_.children.empty()) {
+      return;
+    }
+    MergeMessage(&root_, source, options, destination);
+  }
+
+ private:
+  struct Node {
+    Node() {}
+
+    ~Node() { ClearChildren(); }
+
+    void ClearChildren() {
+      for (map<string, Node*>::iterator it = children.begin();
+           it != children.end(); ++it) {
+        delete it->second;
+      }
+      children.clear();
+    }
+
+    map<string, Node*> children;
+
+   private:
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Node);
+  };
+
+  // Merge a sub-tree to mask. This method adds the field paths represented
+  // by all leaf nodes descended from "node" to mask.
+  void MergeToFieldMask(const string& prefix, const Node* node, FieldMask* out);
+
+  // Merge all leaf nodes of a sub-tree to another tree.
+  void MergeLeafNodesToTree(const string& prefix, const Node* node,
+                            FieldMaskTree* out);
+
+  // Merge all fields specified by a sub-tree from one message to another.
+  void MergeMessage(const Node* node, const Message& source,
+                    const FieldMaskUtil::MergeOptions& options,
+                    Message* destination);
+
+  Node root_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(FieldMaskTree);
+};
+
+FieldMaskTree::FieldMaskTree() {}
+
+FieldMaskTree::~FieldMaskTree() {}
+
+void FieldMaskTree::MergeFromFieldMask(const FieldMask& mask) {
+  for (int i = 0; i < mask.paths_size(); ++i) {
+    AddPath(mask.paths(i));
+  }
+}
+
+void FieldMaskTree::MergeToFieldMask(FieldMask* mask) {
+  MergeToFieldMask("", &root_, mask);
+}
+
+void FieldMaskTree::MergeToFieldMask(const string& prefix, const Node* node,
+                                     FieldMask* out) {
+  if (node->children.empty()) {
+    if (prefix.empty()) {
+      // This is the root node.
+      return;
+    }
+    out->add_paths(prefix);
+    return;
+  }
+  for (map<string, Node*>::const_iterator it = node->children.begin();
+       it != node->children.end(); ++it) {
+    string current_path = prefix.empty() ? it->first : prefix + "." + it->first;
+    MergeToFieldMask(current_path, it->second, out);
+  }
+}
+
+void FieldMaskTree::AddPath(const string& path) {
+  vector<string> parts = Split(path, ".");
+  if (parts.empty()) {
+    return;
+  }
+  bool new_branch = false;
+  Node* node = &root_;
+  for (int i = 0; i < parts.size(); ++i) {
+    if (!new_branch && node != &root_ && node->children.empty()) {
+      // Path matches an existing leaf node. This means the path is already
+      // coverred by this tree (for example, adding "foo.bar.baz" to a tree
+      // which already contains "foo.bar").
+      return;
+    }
+    const string& node_name = parts[i];
+    Node*& child = node->children[node_name];
+    if (child == NULL) {
+      new_branch = true;
+      child = new Node();
+    }
+    node = child;
+  }
+  if (!node->children.empty()) {
+    node->ClearChildren();
+  }
+}
+
+void FieldMaskTree::IntersectPath(const string& path, FieldMaskTree* out) {
+  vector<string> parts = Split(path, ".");
+  if (parts.empty()) {
+    return;
+  }
+  const Node* node = &root_;
+  for (int i = 0; i < parts.size(); ++i) {
+    if (node->children.empty()) {
+      if (node != &root_) {
+        out->AddPath(path);
+      }
+      return;
+    }
+    const string& node_name = parts[i];
+    const Node* result = FindPtrOrNull(node->children, node_name);
+    if (result == NULL) {
+      // No intersection found.
+      return;
+    }
+    node = result;
+  }
+  // Now we found a matching node with the given path. Add all leaf nodes
+  // to out.
+  MergeLeafNodesToTree(path, node, out);
+}
+
+void FieldMaskTree::MergeLeafNodesToTree(const string& prefix, const Node* node,
+                                         FieldMaskTree* out) {
+  if (node->children.empty()) {
+    out->AddPath(prefix);
+  }
+  for (map<string, Node*>::const_iterator it = node->children.begin();
+       it != node->children.end(); ++it) {
+    string current_path = prefix.empty() ? it->first : prefix + "." + it->first;
+    MergeLeafNodesToTree(current_path, it->second, out);
+  }
+}
+
+void FieldMaskTree::MergeMessage(const Node* node, const Message& source,
+                                 const FieldMaskUtil::MergeOptions& options,
+                                 Message* destination) {
+  GOOGLE_DCHECK(!node->children.empty());
+  const Reflection* source_reflection = source.GetReflection();
+  const Reflection* destination_reflection = destination->GetReflection();
+  const Descriptor* descriptor = source.GetDescriptor();
+  for (map<string, Node*>::const_iterator it = node->children.begin();
+       it != node->children.end(); ++it) {
+    const string& field_name = it->first;
+    const Node* child = it->second;
+    const FieldDescriptor* field = descriptor->FindFieldByName(field_name);
+    if (field == NULL) {
+      GOOGLE_LOG(ERROR) << "Cannot find field \"" << field_name << "\" in message "
+                 << descriptor->full_name();
+      continue;
+    }
+    if (!child->children.empty()) {
+      // Sub-paths are only allowed for singular message fields.
+      if (field->is_repeated() ||
+          field->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
+        GOOGLE_LOG(ERROR) << "Field \"" << field_name << "\" in message "
+                   << descriptor->full_name()
+                   << " is not a singular message field and cannot "
+                   << "have sub-fields.";
+        continue;
+      }
+      MergeMessage(child, source_reflection->GetMessage(source, field), options,
+                   destination_reflection->MutableMessage(destination, field));
+      continue;
+    }
+    if (!field->is_repeated()) {
+      switch (field->cpp_type()) {
+#define COPY_VALUE(TYPE, Name)                                            \
+  case FieldDescriptor::CPPTYPE_##TYPE: {                                 \
+    destination_reflection->Set##Name(                                    \
+        destination, field, source_reflection->Get##Name(source, field)); \
+    break;                                                                \
+  }
+        COPY_VALUE(BOOL, Bool)
+        COPY_VALUE(INT32, Int32)
+        COPY_VALUE(INT64, Int64)
+        COPY_VALUE(UINT32, UInt32)
+        COPY_VALUE(UINT64, UInt64)
+        COPY_VALUE(FLOAT, Float)
+        COPY_VALUE(DOUBLE, Double)
+        COPY_VALUE(ENUM, Enum)
+        COPY_VALUE(STRING, String)
+#undef COPY_VALUE
+        case FieldDescriptor::CPPTYPE_MESSAGE: {
+          if (options.replace_message_fields()) {
+            destination_reflection->ClearField(destination, field);
+          }
+          if (source_reflection->HasField(source, field)) {
+            destination_reflection->MutableMessage(destination, field)
+                ->MergeFrom(source_reflection->GetMessage(source, field));
+          }
+          break;
+        }
+      }
+    } else {
+      if (options.replace_repeated_fields()) {
+        destination_reflection->ClearField(destination, field);
+      }
+      switch (field->cpp_type()) {
+#define COPY_REPEATED_VALUE(TYPE, Name)                            \
+  case FieldDescriptor::CPPTYPE_##TYPE: {                          \
+    int size = source_reflection->FieldSize(source, field);        \
+    for (int i = 0; i < size; ++i) {                               \
+      destination_reflection->Add##Name(                           \
+          destination, field,                                      \
+          source_reflection->GetRepeated##Name(source, field, i)); \
+    }                                                              \
+    break;                                                         \
+  }
+        COPY_REPEATED_VALUE(BOOL, Bool)
+        COPY_REPEATED_VALUE(INT32, Int32)
+        COPY_REPEATED_VALUE(INT64, Int64)
+        COPY_REPEATED_VALUE(UINT32, UInt32)
+        COPY_REPEATED_VALUE(UINT64, UInt64)
+        COPY_REPEATED_VALUE(FLOAT, Float)
+        COPY_REPEATED_VALUE(DOUBLE, Double)
+        COPY_REPEATED_VALUE(ENUM, Enum)
+        COPY_REPEATED_VALUE(STRING, String)
+#undef COPY_REPEATED_VALUE
+        case FieldDescriptor::CPPTYPE_MESSAGE: {
+          int size = source_reflection->FieldSize(source, field);
+          for (int i = 0; i < size; ++i) {
+            destination_reflection->AddMessage(destination, field)
+                ->MergeFrom(
+                    source_reflection->GetRepeatedMessage(source, field, i));
+          }
+          break;
+        }
+      }
+    }
+  }
+}
+
+}  // namespace
+
+void FieldMaskUtil::ToCanonicalForm(const FieldMask& mask, FieldMask* out) {
+  FieldMaskTree tree;
+  tree.MergeFromFieldMask(mask);
+  out->Clear();
+  tree.MergeToFieldMask(out);
+}
+
+void FieldMaskUtil::Union(const FieldMask& mask1, const FieldMask& mask2,
+                          FieldMask* out) {
+  FieldMaskTree tree;
+  tree.MergeFromFieldMask(mask1);
+  tree.MergeFromFieldMask(mask2);
+  out->Clear();
+  tree.MergeToFieldMask(out);
+}
+
+void FieldMaskUtil::Intersect(const FieldMask& mask1, const FieldMask& mask2,
+                              FieldMask* out) {
+  FieldMaskTree tree, intersection;
+  tree.MergeFromFieldMask(mask1);
+  for (int i = 0; i < mask2.paths_size(); ++i) {
+    tree.IntersectPath(mask2.paths(i), &intersection);
+  }
+  out->Clear();
+  intersection.MergeToFieldMask(out);
+}
+
+bool FieldMaskUtil::IsPathInFieldMask(StringPiece path, const FieldMask& mask) {
+  for (int i = 0; i < mask.paths_size(); ++i) {
+    const string& mask_path = mask.paths(i);
+    if (path == mask_path) {
+      return true;
+    } else if (mask_path.length() < path.length()) {
+      // Also check whether mask.paths(i) is a prefix of path.
+      if (path.substr(0, mask_path.length() + 1).compare(mask_path + ".") ==
+          0) {
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+void FieldMaskUtil::MergeMessageTo(const Message& source, const FieldMask& mask,
+                                   const MergeOptions& options,
+                                   Message* destination) {
+  GOOGLE_CHECK(source.GetDescriptor() == destination->GetDescriptor());
+  // Build a FieldMaskTree and walk through the tree to merge all specified
+  // fields.
+  FieldMaskTree tree;
+  tree.MergeFromFieldMask(mask);
+  tree.MergeMessage(source, options, destination);
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/field_mask_util.h b/src/google/protobuf/util/field_mask_util.h
new file mode 100644
index 0000000..92f6989
--- /dev/null
+++ b/src/google/protobuf/util/field_mask_util.h
@@ -0,0 +1,147 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_FIELD_MASK_UTIL_H__
+#define GOOGLE_PROTOBUF_UTIL_FIELD_MASK_UTIL_H__
+
+#include <string>
+
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/field_mask.pb.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+class LIBPROTOBUF_EXPORT FieldMaskUtil {
+  typedef google::protobuf::FieldMask FieldMask;
+
+ public:
+  // Converts FieldMask to/from string, formatted according to proto3 JSON
+  // spec for FieldMask (e.g., "foo,bar,baz.quz").
+  static string ToString(const FieldMask& mask);
+  static void FromString(StringPiece str, FieldMask* out);
+
+  // Checks whether the given path is valid for type T.
+  template <typename T>
+  static bool IsValidPath(StringPiece path) {
+    return InternalIsValidPath(T::descriptor(), path);
+  }
+
+  // Checks whether the given FieldMask is valid for type T.
+  template <typename T>
+  static bool IsValidFieldMask(const FieldMask& mask) {
+    for (int i = 0; i < mask.paths_size(); ++i) {
+      if (!InternalIsValidPath(T::descriptor(), mask.paths(i))) return false;
+    }
+    return true;
+  }
+
+  // Adds a path to FieldMask after checking whether the given path is valid.
+  // This method check-fails if the path is not a valid path for type T.
+  template <typename T>
+  static void AddPathToFieldMask(StringPiece path, FieldMask* mask) {
+    GOOGLE_CHECK(IsValidPath<T>(path));
+    mask->add_paths(path);
+  }
+
+  // Creates a FieldMask with all fields of type T. This FieldMask only
+  // contains fields of T but not any sub-message fields.
+  template <typename T>
+  static void GetFieldMaskForAllFields(FieldMask* out) {
+    InternalGetFieldMaskForAllFields(T::descriptor(), out);
+  }
+
+  // Converts a FieldMask to the canonical form. It will:
+  //   1. Remove paths that are covered by another path. For example,
+  //      "foo.bar" is covered by "foo" and will be removed if "foo"
+  //      is also in the FieldMask.
+  //   2. Sort all paths in alphabetical order.
+  static void ToCanonicalForm(const FieldMask& mask, FieldMask* out);
+
+  // Creates an union of two FieldMasks.
+  static void Union(const FieldMask& mask1, const FieldMask& mask2,
+                    FieldMask* out);
+
+  // Creates an intersection of two FieldMasks.
+  static void Intersect(const FieldMask& mask1, const FieldMask& mask2,
+                        FieldMask* out);
+
+  // Returns true if path is covered by the given FieldMask. Note that path
+  // "foo.bar" covers all paths like "foo.bar.baz", "foo.bar.quz.x", etc.
+  static bool IsPathInFieldMask(StringPiece path, const FieldMask& mask);
+
+  class MergeOptions;
+  // Merges fields specified in a FieldMask into another message.
+  static void MergeMessageTo(const Message& source, const FieldMask& mask,
+                             const MergeOptions& options, Message* destination);
+
+ private:
+  static bool InternalIsValidPath(const Descriptor* descriptor,
+                                  StringPiece path);
+
+  static void InternalGetFieldMaskForAllFields(const Descriptor* descriptor,
+                                               FieldMask* out);
+};
+
+class LIBPROTOBUF_EXPORT FieldMaskUtil::MergeOptions {
+ public:
+  MergeOptions()
+      : replace_message_fields_(false), replace_repeated_fields_(false) {}
+  // When merging message fields, the default behavior is to merge the
+  // content of two message fields together. If you instead want to use
+  // the field from the source message to replace the corresponding field
+  // in the destination message, set this flag to true. When this flag is set,
+  // specified submessage fields that are missing in source will be cleared in
+  // destination.
+  void set_replace_message_fields(bool value) {
+    replace_message_fields_ = value;
+  }
+  bool replace_message_fields() const { return replace_message_fields_; }
+  // The default merging behavior will append entries from the source
+  // repeated field to the destination repeated field. If you only want
+  // to keep the entries from the source repeated field, set this flag
+  // to true.
+  void set_replace_repeated_fields(bool value) {
+    replace_repeated_fields_ = value;
+  }
+  bool replace_repeated_fields() const { return replace_repeated_fields_; }
+
+ private:
+  bool replace_message_fields_;
+  bool replace_repeated_fields_;
+};
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_FIELD_MASK_UTIL_H__
diff --git a/src/google/protobuf/util/field_mask_util_test.cc b/src/google/protobuf/util/field_mask_util_test.cc
new file mode 100644
index 0000000..a952325
--- /dev/null
+++ b/src/google/protobuf/util/field_mask_util_test.cc
@@ -0,0 +1,395 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/field_mask_util.h>
+
+#include <google/protobuf/field_mask.pb.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/test_util.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+
+using protobuf_unittest::TestAllTypes;
+using protobuf_unittest::NestedTestAllTypes;
+using google::protobuf::FieldMask;
+
+TEST(FieldMaskUtilTest, StringFormat) {
+  FieldMask mask;
+  EXPECT_EQ("", FieldMaskUtil::ToString(mask));
+  mask.add_paths("foo");
+  EXPECT_EQ("foo", FieldMaskUtil::ToString(mask));
+  mask.add_paths("bar");
+  EXPECT_EQ("foo,bar", FieldMaskUtil::ToString(mask));
+
+  FieldMaskUtil::FromString("", &mask);
+  EXPECT_EQ(0, mask.paths_size());
+  FieldMaskUtil::FromString("foo", &mask);
+  EXPECT_EQ(1, mask.paths_size());
+  EXPECT_EQ("foo", mask.paths(0));
+  FieldMaskUtil::FromString("foo,bar", &mask);
+  EXPECT_EQ(2, mask.paths_size());
+  EXPECT_EQ("foo", mask.paths(0));
+  EXPECT_EQ("bar", mask.paths(1));
+}
+
+TEST(FieldMaskUtilTest, TestIsVaildPath) {
+  EXPECT_TRUE(FieldMaskUtil::IsValidPath<TestAllTypes>("optional_int32"));
+  EXPECT_FALSE(FieldMaskUtil::IsValidPath<TestAllTypes>("optional_nonexist"));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsValidPath<TestAllTypes>("optional_nested_message.bb"));
+  EXPECT_FALSE(FieldMaskUtil::IsValidPath<TestAllTypes>(
+      "optional_nested_message.nonexist"));
+  // FieldMask cannot be used to specify sub-fields of a repeated message.
+  EXPECT_FALSE(
+      FieldMaskUtil::IsValidPath<TestAllTypes>("repeated_nested_message.bb"));
+}
+
+TEST(FieldMaskUtilTest, TestIsValidFieldMask) {
+  FieldMask mask;
+  FieldMaskUtil::FromString("optional_int32,optional_nested_message.bb", &mask);
+  EXPECT_TRUE(FieldMaskUtil::IsValidFieldMask<TestAllTypes>(mask));
+
+  FieldMaskUtil::FromString(
+      "optional_int32,optional_nested_message.bb,optional_nonexist", &mask);
+  EXPECT_FALSE(FieldMaskUtil::IsValidFieldMask<TestAllTypes>(mask));
+}
+
+TEST(FieldMaskUtilTest, TestGetFieldMaskForAllFields) {
+  FieldMask mask;
+  FieldMaskUtil::GetFieldMaskForAllFields<TestAllTypes::NestedMessage>(&mask);
+  EXPECT_EQ(1, mask.paths_size());
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("bb", mask));
+
+  FieldMaskUtil::GetFieldMaskForAllFields<TestAllTypes>(&mask);
+  EXPECT_EQ(76, mask.paths_size());
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_int32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_int64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_uint32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_uint64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_sint32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_sint64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_fixed32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_fixed64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_sfixed32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_sfixed64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_float", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_double", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_bool", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_string", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_bytes", mask));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsPathInFieldMask("optional_nested_message", mask));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsPathInFieldMask("optional_foreign_message", mask));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsPathInFieldMask("optional_import_message", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_nested_enum", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_foreign_enum", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("optional_import_enum", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_int32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_int64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_uint32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_uint64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_sint32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_sint64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_fixed32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_fixed64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_sfixed32", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_sfixed64", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_float", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_double", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_bool", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_string", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_bytes", mask));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsPathInFieldMask("repeated_nested_message", mask));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsPathInFieldMask("repeated_foreign_message", mask));
+  EXPECT_TRUE(
+      FieldMaskUtil::IsPathInFieldMask("repeated_import_message", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_nested_enum", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_foreign_enum", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("repeated_import_enum", mask));
+}
+
+TEST(FieldMaskUtilTest, TestToCanonicalForm) {
+  FieldMask in, out;
+  // Paths will be sorted.
+  FieldMaskUtil::FromString("baz.quz,bar,foo", &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("bar,baz.quz,foo", FieldMaskUtil::ToString(out));
+  // Duplicated paths will be removed.
+  FieldMaskUtil::FromString("foo,bar,foo", &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("bar,foo", FieldMaskUtil::ToString(out));
+  // Sub-paths of other paths will be removed.
+  FieldMaskUtil::FromString("foo.b1,bar.b1,foo.b2,bar", &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("bar,foo.b1,foo.b2", FieldMaskUtil::ToString(out));
+
+  // Test more deeply nested cases.
+  FieldMaskUtil::FromString(
+      "foo.bar.baz1,"
+      "foo.bar.baz2.quz,"
+      "foo.bar.baz2",
+      &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("foo.bar.baz1,foo.bar.baz2", FieldMaskUtil::ToString(out));
+  FieldMaskUtil::FromString(
+      "foo.bar.baz1,"
+      "foo.bar.baz2,"
+      "foo.bar.baz2.quz",
+      &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("foo.bar.baz1,foo.bar.baz2", FieldMaskUtil::ToString(out));
+  FieldMaskUtil::FromString(
+      "foo.bar.baz1,"
+      "foo.bar.baz2,"
+      "foo.bar.baz2.quz,"
+      "foo.bar",
+      &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("foo.bar", FieldMaskUtil::ToString(out));
+  FieldMaskUtil::FromString(
+      "foo.bar.baz1,"
+      "foo.bar.baz2,"
+      "foo.bar.baz2.quz,"
+      "foo",
+      &in);
+  FieldMaskUtil::ToCanonicalForm(in, &out);
+  EXPECT_EQ("foo", FieldMaskUtil::ToString(out));
+}
+
+TEST(FieldMaskUtilTest, TestUnion) {
+  FieldMask mask1, mask2, out;
+  // Test cases without overlapping.
+  FieldMaskUtil::FromString("foo,baz", &mask1);
+  FieldMaskUtil::FromString("bar,quz", &mask2);
+  FieldMaskUtil::Union(mask1, mask2, &out);
+  EXPECT_EQ("bar,baz,foo,quz", FieldMaskUtil::ToString(out));
+  // Overlap with duplicated paths.
+  FieldMaskUtil::FromString("foo,baz.bb", &mask1);
+  FieldMaskUtil::FromString("baz.bb,quz", &mask2);
+  FieldMaskUtil::Union(mask1, mask2, &out);
+  EXPECT_EQ("baz.bb,foo,quz", FieldMaskUtil::ToString(out));
+  // Overlap with paths covering some other paths.
+  FieldMaskUtil::FromString("foo.bar.baz,quz", &mask1);
+  FieldMaskUtil::FromString("foo.bar,bar", &mask2);
+  FieldMaskUtil::Union(mask1, mask2, &out);
+  EXPECT_EQ("bar,foo.bar,quz", FieldMaskUtil::ToString(out));
+}
+
+TEST(FieldMaskUtilTest, TestIntersect) {
+  FieldMask mask1, mask2, out;
+  // Test cases without overlapping.
+  FieldMaskUtil::FromString("foo,baz", &mask1);
+  FieldMaskUtil::FromString("bar,quz", &mask2);
+  FieldMaskUtil::Intersect(mask1, mask2, &out);
+  EXPECT_EQ("", FieldMaskUtil::ToString(out));
+  // Overlap with duplicated paths.
+  FieldMaskUtil::FromString("foo,baz.bb", &mask1);
+  FieldMaskUtil::FromString("baz.bb,quz", &mask2);
+  FieldMaskUtil::Intersect(mask1, mask2, &out);
+  EXPECT_EQ("baz.bb", FieldMaskUtil::ToString(out));
+  // Overlap with paths covering some other paths.
+  FieldMaskUtil::FromString("foo.bar.baz,quz", &mask1);
+  FieldMaskUtil::FromString("foo.bar,bar", &mask2);
+  FieldMaskUtil::Intersect(mask1, mask2, &out);
+  EXPECT_EQ("foo.bar.baz", FieldMaskUtil::ToString(out));
+}
+
+TEST(FieldMaskUtilTest, TestIspathInFieldMask) {
+  FieldMask mask;
+  FieldMaskUtil::FromString("foo.bar", &mask);
+  EXPECT_FALSE(FieldMaskUtil::IsPathInFieldMask("", mask));
+  EXPECT_FALSE(FieldMaskUtil::IsPathInFieldMask("foo", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("foo.bar", mask));
+  EXPECT_TRUE(FieldMaskUtil::IsPathInFieldMask("foo.bar.baz", mask));
+  EXPECT_FALSE(FieldMaskUtil::IsPathInFieldMask("foo.bar0.baz", mask));
+}
+
+TEST(FieldMaskUtilTest, MergeMessage) {
+  TestAllTypes src, dst;
+  TestUtil::SetAllFields(&src);
+  FieldMaskUtil::MergeOptions options;
+
+#define TEST_MERGE_ONE_PRIMITIVE_FIELD(field_name)           \
+  {                                                          \
+    TestAllTypes tmp;                                        \
+    tmp.set_##field_name(src.field_name());                  \
+    FieldMask mask;                                          \
+    mask.add_paths(#field_name);                             \
+    dst.Clear();                                             \
+    FieldMaskUtil::MergeMessageTo(src, mask, options, &dst); \
+    EXPECT_EQ(tmp.DebugString(), dst.DebugString());         \
+  }
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_int32)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_int64)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_uint32)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_uint64)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_sint32)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_sint64)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_fixed32)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_fixed64)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_sfixed32)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_sfixed64)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_float)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_double)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_bool)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_string)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_bytes)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_nested_enum)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_foreign_enum)
+  TEST_MERGE_ONE_PRIMITIVE_FIELD(optional_import_enum)
+#undef TEST_MERGE_ONE_PRIMITIVE_FIELD
+
+#define TEST_MERGE_ONE_FIELD(field_name)                     \
+  {                                                          \
+    TestAllTypes tmp;                                        \
+    *tmp.mutable_##field_name() = src.field_name();          \
+    FieldMask mask;                                          \
+    mask.add_paths(#field_name);                             \
+    dst.Clear();                                             \
+    FieldMaskUtil::MergeMessageTo(src, mask, options, &dst); \
+    EXPECT_EQ(tmp.DebugString(), dst.DebugString());         \
+  }
+  TEST_MERGE_ONE_FIELD(optional_nested_message)
+  TEST_MERGE_ONE_FIELD(optional_foreign_message)
+  TEST_MERGE_ONE_FIELD(optional_import_message)
+
+  TEST_MERGE_ONE_FIELD(repeated_int32)
+  TEST_MERGE_ONE_FIELD(repeated_int64)
+  TEST_MERGE_ONE_FIELD(repeated_uint32)
+  TEST_MERGE_ONE_FIELD(repeated_uint64)
+  TEST_MERGE_ONE_FIELD(repeated_sint32)
+  TEST_MERGE_ONE_FIELD(repeated_sint64)
+  TEST_MERGE_ONE_FIELD(repeated_fixed32)
+  TEST_MERGE_ONE_FIELD(repeated_fixed64)
+  TEST_MERGE_ONE_FIELD(repeated_sfixed32)
+  TEST_MERGE_ONE_FIELD(repeated_sfixed64)
+  TEST_MERGE_ONE_FIELD(repeated_float)
+  TEST_MERGE_ONE_FIELD(repeated_double)
+  TEST_MERGE_ONE_FIELD(repeated_bool)
+  TEST_MERGE_ONE_FIELD(repeated_string)
+  TEST_MERGE_ONE_FIELD(repeated_bytes)
+  TEST_MERGE_ONE_FIELD(repeated_nested_message)
+  TEST_MERGE_ONE_FIELD(repeated_foreign_message)
+  TEST_MERGE_ONE_FIELD(repeated_import_message)
+  TEST_MERGE_ONE_FIELD(repeated_nested_enum)
+  TEST_MERGE_ONE_FIELD(repeated_foreign_enum)
+  TEST_MERGE_ONE_FIELD(repeated_import_enum)
+#undef TEST_MERGE_ONE_FIELD
+
+  // Test merge nested fields.
+  NestedTestAllTypes nested_src, nested_dst;
+  nested_src.mutable_child()->mutable_payload()->set_optional_int32(1234);
+  nested_src.mutable_child()
+      ->mutable_child()
+      ->mutable_payload()
+      ->set_optional_int32(5678);
+  FieldMask mask;
+  FieldMaskUtil::FromString("child.payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_EQ(1234, nested_dst.child().payload().optional_int32());
+  EXPECT_EQ(0, nested_dst.child().child().payload().optional_int32());
+
+  FieldMaskUtil::FromString("child.child.payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_EQ(1234, nested_dst.child().payload().optional_int32());
+  EXPECT_EQ(5678, nested_dst.child().child().payload().optional_int32());
+
+  nested_dst.Clear();
+  FieldMaskUtil::FromString("child.child.payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_EQ(0, nested_dst.child().payload().optional_int32());
+  EXPECT_EQ(5678, nested_dst.child().child().payload().optional_int32());
+
+  nested_dst.Clear();
+  FieldMaskUtil::FromString("child", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_EQ(1234, nested_dst.child().payload().optional_int32());
+  EXPECT_EQ(5678, nested_dst.child().child().payload().optional_int32());
+
+  // Test MergeOptions.
+
+  nested_dst.Clear();
+  nested_dst.mutable_child()->mutable_payload()->set_optional_int64(4321);
+  // Message fields will be merged by default.
+  FieldMaskUtil::FromString("child.payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_EQ(1234, nested_dst.child().payload().optional_int32());
+  EXPECT_EQ(4321, nested_dst.child().payload().optional_int64());
+  // Change the behavior to replace message fields.
+  options.set_replace_message_fields(true);
+  FieldMaskUtil::FromString("child.payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_EQ(1234, nested_dst.child().payload().optional_int32());
+  EXPECT_EQ(0, nested_dst.child().payload().optional_int64());
+
+  // By default, fields missing in source are not cleared in destination.
+  options.set_replace_message_fields(false);
+  nested_dst.mutable_payload();
+  EXPECT_TRUE(nested_dst.has_payload());
+  FieldMaskUtil::FromString("payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_TRUE(nested_dst.has_payload());
+  // But they are cleared when replacing message fields.
+  options.set_replace_message_fields(true);
+  nested_dst.Clear();
+  nested_dst.mutable_payload();
+  FieldMaskUtil::FromString("payload", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  EXPECT_FALSE(nested_dst.has_payload());
+
+  nested_src.mutable_payload()->add_repeated_int32(1234);
+  nested_dst.mutable_payload()->add_repeated_int32(5678);
+  // Repeated fields will be appended by default.
+  FieldMaskUtil::FromString("payload.repeated_int32", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  ASSERT_EQ(2, nested_dst.payload().repeated_int32_size());
+  EXPECT_EQ(5678, nested_dst.payload().repeated_int32(0));
+  EXPECT_EQ(1234, nested_dst.payload().repeated_int32(1));
+  // Change the behavior to replace repeated fields.
+  options.set_replace_repeated_fields(true);
+  FieldMaskUtil::FromString("payload.repeated_int32", &mask);
+  FieldMaskUtil::MergeMessageTo(nested_src, mask, options, &nested_dst);
+  ASSERT_EQ(1, nested_dst.payload().repeated_int32_size());
+  EXPECT_EQ(1234, nested_dst.payload().repeated_int32(0));
+}
+
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/constants.h b/src/google/protobuf/util/internal/constants.h
new file mode 100644
index 0000000..0cb8f6e
--- /dev/null
+++ b/src/google/protobuf/util/internal/constants.h
@@ -0,0 +1,93 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_CONSTANTS_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_CONSTANTS_H__
+
+#include <google/protobuf/stubs/common.h>
+
+// This file contains constants used by //net/proto2/util/converter.
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+// Prefix for type URLs.
+const char kTypeServiceBaseUrl[] = "type.googleapis.com";
+
+// Format string for RFC3339 timestamp formatting.
+const char kRfc3339TimeFormat[] = "%Y-%m-%dT%H:%M:%S";
+
+// Minimum seconds allowed in a google.protobuf.TimeStamp or Duration value.
+const int64 kMinSeconds = -315576000000;
+
+// Maximum seconds allowed in a google.protobuf.TimeStamp or Duration value.
+const int64 kMaxSeconds = 315576000000;
+
+// Nano seconds in a second.
+const int32 kNanosPerSecond = 1000000000;
+
+// Type url representing NULL values in google.protobuf.Struct type.
+const char kStructNullValueTypeUrl[] =
+    "type.googleapis.com/google.protobuf.NullValue";
+
+// Type string for google.protobuf.Struct
+const char kStructType[] = "google.protobuf.Struct";
+
+// Type string for struct.proto's google.protobuf.Value value type.
+const char kStructValueType[] = "google.protobuf.Value";
+
+// Type string for struct.proto's google.protobuf.ListValue value type.
+const char kStructListValueType[] = "google.protobuf.ListValue";
+
+// Type string for google.protobuf.Timestamp
+const char kTimestampType[] = "google.protobuf.Timestamp";
+
+// Type string for google.protobuf.Duration
+const char kDurationType[] = "google.protobuf.Duration";
+
+// Type URL for struct value type google.protobuf.Value
+const char kStructValueTypeUrl[] = "type.googleapis.com/google.protobuf.Value";
+
+// Type URL for struct value type google.protobuf.Value
+const char kStructTypeUrl[] = "type.googleapis.com/google.protobuf.Struct";
+
+// Type string for google.protobuf.Any
+const char kAnyType[] = "google.protobuf.Any";
+
+// The type URL of google.protobuf.FieldMask;
+const char kFieldMaskTypeUrl[] =
+    "type.googleapis.com/google.protobuf.FieldMask";
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_CONSTANTS_H__
diff --git a/src/google/protobuf/util/internal/datapiece.cc b/src/google/protobuf/util/internal/datapiece.cc
new file mode 100644
index 0000000..b557429
--- /dev/null
+++ b/src/google/protobuf/util/internal/datapiece.cc
@@ -0,0 +1,324 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/datapiece.h>
+
+#include <google/protobuf/struct.pb.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/mathlimits.h>
+#include <google/protobuf/stubs/mathutil.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::EnumDescriptor;
+using google::protobuf::EnumValueDescriptor;
+;
+;
+using util::error::Code;
+using util::Status;
+using util::StatusOr;
+
+namespace {
+
+inline Status InvalidArgument(StringPiece value_str) {
+  return Status(util::error::INVALID_ARGUMENT, value_str);
+}
+
+template <typename To, typename From>
+StatusOr<To> ValidateNumberConversion(To after, From before) {
+  if (after == before &&
+      MathUtil::Sign<From>(before) == MathUtil::Sign<To>(after)) {
+    return after;
+  } else {
+    return InvalidArgument(::google::protobuf::internal::is_integral<From>::value
+                               ? ValueAsString(before)
+                               : ::google::protobuf::internal::is_same<From, double>::value
+                                     ? DoubleAsString(before)
+                                     : FloatAsString(before));
+  }
+}
+
+// For general conversion between
+//     int32, int64, uint32, uint64, double and float
+// except conversion between double and float.
+template <typename To, typename From>
+StatusOr<To> NumberConvertAndCheck(From before) {
+  if (::google::protobuf::internal::is_same<From, To>::value) return before;
+
+  To after = static_cast<To>(before);
+  return ValidateNumberConversion(after, before);
+}
+
+// For conversion to integer types (int32, int64, uint32, uint64) from floating
+// point types (double, float) only.
+template <typename To, typename From>
+StatusOr<To> FloatingPointToIntConvertAndCheck(From before) {
+  if (::google::protobuf::internal::is_same<From, To>::value) return before;
+
+  To after = static_cast<To>(before);
+  return ValidateNumberConversion(after, before);
+}
+
+// For conversion between double and float only.
+template <typename To, typename From>
+StatusOr<To> FloatingPointConvertAndCheck(From before) {
+  if (MathLimits<From>::IsNaN(before)) {
+    return std::numeric_limits<To>::quiet_NaN();
+  }
+
+  To after = static_cast<To>(before);
+  if (MathUtil::AlmostEquals<To>(after, before)) {
+    return after;
+  } else {
+    return InvalidArgument(::google::protobuf::internal::is_same<From, double>::value
+                               ? DoubleAsString(before)
+                               : FloatAsString(before));
+  }
+}
+
+}  // namespace
+
+StatusOr<int32> DataPiece::ToInt32() const {
+  if (type_ == TYPE_STRING) return StringToNumber<int32>(safe_strto32);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<int32, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<int32, float>(float_);
+
+  return GenericConvert<int32>();
+}
+
+StatusOr<uint32> DataPiece::ToUint32() const {
+  if (type_ == TYPE_STRING) return StringToNumber<uint32>(safe_strtou32);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<uint32, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<uint32, float>(float_);
+
+  return GenericConvert<uint32>();
+}
+
+StatusOr<int64> DataPiece::ToInt64() const {
+  if (type_ == TYPE_STRING) return StringToNumber<int64>(safe_strto64);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<int64, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<int64, float>(float_);
+
+  return GenericConvert<int64>();
+}
+
+StatusOr<uint64> DataPiece::ToUint64() const {
+  if (type_ == TYPE_STRING) return StringToNumber<uint64>(safe_strtou64);
+
+  if (type_ == TYPE_DOUBLE)
+    return FloatingPointToIntConvertAndCheck<uint64, double>(double_);
+
+  if (type_ == TYPE_FLOAT)
+    return FloatingPointToIntConvertAndCheck<uint64, float>(float_);
+
+  return GenericConvert<uint64>();
+}
+
+StatusOr<double> DataPiece::ToDouble() const {
+  if (type_ == TYPE_FLOAT) {
+    return FloatingPointConvertAndCheck<double, float>(float_);
+  }
+  if (type_ == TYPE_STRING) {
+    if (str_ == "Infinity") return std::numeric_limits<double>::infinity();
+    if (str_ == "-Infinity") return -std::numeric_limits<double>::infinity();
+    if (str_ == "NaN") return std::numeric_limits<double>::quiet_NaN();
+    return StringToNumber<double>(safe_strtod);
+  }
+  return GenericConvert<double>();
+}
+
+StatusOr<float> DataPiece::ToFloat() const {
+  if (type_ == TYPE_DOUBLE) {
+    return FloatingPointConvertAndCheck<float, double>(double_);
+  }
+  if (type_ == TYPE_STRING) {
+    if (str_ == "Infinity") return std::numeric_limits<float>::infinity();
+    if (str_ == "-Infinity") return -std::numeric_limits<float>::infinity();
+    if (str_ == "NaN") return std::numeric_limits<float>::quiet_NaN();
+    // SafeStrToFloat() is used instead of safe_strtof() because the later
+    // does not fail on inputs like SimpleDtoa(DBL_MAX).
+    return StringToNumber<float>(SafeStrToFloat);
+  }
+  return GenericConvert<float>();
+}
+
+StatusOr<bool> DataPiece::ToBool() const {
+  switch (type_) {
+    case TYPE_BOOL:
+      return bool_;
+    case TYPE_STRING:
+      return StringToNumber<bool>(safe_strtob);
+    default:
+      return InvalidArgument(
+          ValueAsStringOrDefault("Wrong type. Cannot convert to Bool."));
+  }
+}
+
+StatusOr<string> DataPiece::ToString() const {
+  switch (type_) {
+    case TYPE_STRING:
+      return str_.ToString();
+    case TYPE_BYTES: {
+      string base64;
+      Base64Escape(str_, &base64);
+      return base64;
+    }
+    default:
+      return InvalidArgument(
+          ValueAsStringOrDefault("Cannot convert to string."));
+  }
+}
+
+string DataPiece::ValueAsStringOrDefault(StringPiece default_string) const {
+  switch (type_) {
+    case TYPE_INT32:
+      return SimpleItoa(i32_);
+    case TYPE_INT64:
+      return SimpleItoa(i64_);
+    case TYPE_UINT32:
+      return SimpleItoa(u32_);
+    case TYPE_UINT64:
+      return SimpleItoa(u64_);
+    case TYPE_DOUBLE:
+      return DoubleAsString(double_);
+    case TYPE_FLOAT:
+      return FloatAsString(float_);
+    case TYPE_BOOL:
+      return SimpleBtoa(bool_);
+    case TYPE_STRING:
+      return StrCat("\"", str_.ToString(), "\"");
+    case TYPE_BYTES: {
+      string base64;
+      WebSafeBase64Escape(str_, &base64);
+      return StrCat("\"", base64, "\"");
+    }
+    case TYPE_NULL:
+      return "null";
+    default:
+      return default_string.ToString();
+  }
+}
+
+StatusOr<string> DataPiece::ToBytes() const {
+  if (type_ == TYPE_BYTES) return str_.ToString();
+  if (type_ == TYPE_STRING) {
+    string decoded;
+    if (!WebSafeBase64Unescape(str_, &decoded)) {
+      if (!Base64Unescape(str_, &decoded)) {
+        return InvalidArgument(
+            ValueAsStringOrDefault("Invalid data in input."));
+      }
+    }
+    return decoded;
+  } else {
+    return InvalidArgument(ValueAsStringOrDefault(
+        "Wrong type. Only String or Bytes can be converted to Bytes."));
+  }
+}
+
+StatusOr<int> DataPiece::ToEnum(const google::protobuf::Enum* enum_type) const {
+  if (type_ == TYPE_NULL) return google::protobuf::NULL_VALUE;
+
+  if (type_ == TYPE_STRING) {
+    // First try the given value as a name.
+    string enum_name = str_.ToString();
+    const google::protobuf::EnumValue* value =
+        FindEnumValueByNameOrNull(enum_type, enum_name);
+    if (value != NULL) return value->number();
+    // Next try a normalized name.
+    for (string::iterator it = enum_name.begin(); it != enum_name.end(); ++it) {
+      *it = *it == '-' ? '_' : ascii_toupper(*it);
+    }
+    value = FindEnumValueByNameOrNull(enum_type, enum_name);
+    if (value != NULL) return value->number();
+  } else {
+    StatusOr<int32> value = ToInt32();
+    if (value.ok()) {
+      if (const google::protobuf::EnumValue* enum_value =
+              FindEnumValueByNumberOrNull(enum_type, value.ValueOrDie())) {
+        return enum_value->number();
+      }
+    }
+  }
+  return InvalidArgument(
+      ValueAsStringOrDefault("Cannot find enum with given value."));
+}
+
+template <typename To>
+StatusOr<To> DataPiece::GenericConvert() const {
+  switch (type_) {
+    case TYPE_INT32:
+      return NumberConvertAndCheck<To, int32>(i32_);
+    case TYPE_INT64:
+      return NumberConvertAndCheck<To, int64>(i64_);
+    case TYPE_UINT32:
+      return NumberConvertAndCheck<To, uint32>(u32_);
+    case TYPE_UINT64:
+      return NumberConvertAndCheck<To, uint64>(u64_);
+    case TYPE_DOUBLE:
+      return NumberConvertAndCheck<To, double>(double_);
+    case TYPE_FLOAT:
+      return NumberConvertAndCheck<To, float>(float_);
+    default:  // TYPE_ENUM, TYPE_STRING, TYPE_CORD, TYPE_BOOL
+      return InvalidArgument(ValueAsStringOrDefault(
+          "Wrong type. Bool, Enum, String and Cord not supported in "
+          "GenericConvert."));
+  }
+}
+
+template <typename To>
+StatusOr<To> DataPiece::StringToNumber(bool (*func)(StringPiece, To*)) const {
+  To result;
+  if (func(str_, &result)) return result;
+  return InvalidArgument(StrCat("\"", str_.ToString(), "\""));
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/datapiece.h b/src/google/protobuf/util/internal/datapiece.h
new file mode 100644
index 0000000..f22bfe7
--- /dev/null
+++ b/src/google/protobuf/util/internal/datapiece.h
@@ -0,0 +1,213 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+class Enum;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// Container for a single piece of data together with its data type.
+//
+// For primitive types (int32, int64, uint32, uint64, double, float, bool),
+// the data is stored by value.
+//
+// For string, a StringPiece is stored. For Cord, a pointer to Cord is stored.
+// Just like StringPiece, the DataPiece class does not own the storage for
+// the actual string or Cord, so it is the user's responsiblity to guarantee
+// that the underlying storage is still valid when the DataPiece is accessed.
+class LIBPROTOBUF_EXPORT DataPiece {
+ public:
+  // Identifies data type of the value.
+  // These are the types supported by DataPiece.
+  enum Type {
+    TYPE_INT32 = 1,
+    TYPE_INT64 = 2,
+    TYPE_UINT32 = 3,
+    TYPE_UINT64 = 4,
+    TYPE_DOUBLE = 5,
+    TYPE_FLOAT = 6,
+    TYPE_BOOL = 7,
+    TYPE_ENUM = 8,
+    TYPE_STRING = 9,
+    TYPE_BYTES = 10,
+    TYPE_NULL = 11,  // explicit NULL type
+  };
+
+  // Constructors and Destructor
+  explicit DataPiece(const int32 value) : type_(TYPE_INT32), i32_(value) {}
+  explicit DataPiece(const int64 value) : type_(TYPE_INT64), i64_(value) {}
+  explicit DataPiece(const uint32 value) : type_(TYPE_UINT32), u32_(value) {}
+  explicit DataPiece(const uint64 value) : type_(TYPE_UINT64), u64_(value) {}
+  explicit DataPiece(const double value) : type_(TYPE_DOUBLE), double_(value) {}
+  explicit DataPiece(const float value) : type_(TYPE_FLOAT), float_(value) {}
+  explicit DataPiece(const bool value) : type_(TYPE_BOOL), bool_(value) {}
+  explicit DataPiece(StringPiece value)
+      : type_(TYPE_STRING),
+        str_(StringPiecePod::CreateFromStringPiece(value)) {}
+  // Constructor for bytes. The second parameter is not used.
+  explicit DataPiece(StringPiece value, bool dummy)
+      : type_(TYPE_BYTES), str_(StringPiecePod::CreateFromStringPiece(value)) {}
+  DataPiece(const DataPiece& r) : type_(r.type_), str_(r.str_) {}
+  DataPiece& operator=(const DataPiece& x) {
+    type_ = x.type_;
+    str_ = x.str_;
+    return *this;
+  }
+
+  static DataPiece NullData() { return DataPiece(TYPE_NULL, 0); }
+
+  virtual ~DataPiece() {
+  }
+
+  // Accessors
+  Type type() const { return type_; }
+
+  StringPiece str() const {
+    GOOGLE_LOG_IF(DFATAL, type_ != TYPE_STRING) << "Not a string type.";
+    return str_;
+  }
+
+
+  // Parses, casts or converts the value stored in the DataPiece into an int32.
+  util::StatusOr<int32> ToInt32() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a uint32.
+  util::StatusOr<uint32> ToUint32() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into an int64.
+  util::StatusOr<int64> ToInt64() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a uint64.
+  util::StatusOr<uint64> ToUint64() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a double.
+  util::StatusOr<double> ToDouble() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a float.
+  util::StatusOr<float> ToFloat() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a bool.
+  util::StatusOr<bool> ToBool() const;
+
+  // Parses, casts or converts the value stored in the DataPiece into a string.
+  util::StatusOr<string> ToString() const;
+
+  // Tries to convert the value contained in this datapiece to string. If the
+  // conversion fails, it returns the default_string.
+  string ValueAsStringOrDefault(StringPiece default_string) const;
+
+  util::StatusOr<string> ToBytes() const;
+
+  // Converts a value into protocol buffer enum number. If the value is a
+  // string, first attempts conversion by name, trying names as follows:
+  //   1) the directly provided string value.
+  //   2) the value upper-cased and replacing '-' by '_'
+  // If the value is not a string, attempts to convert to a 32-bit integer.
+  // If none of these succeeds, returns a conversion error status.
+  util::StatusOr<int> ToEnum(const google::protobuf::Enum* enum_type) const;
+
+ private:
+  // Disallow implicit constructor.
+  DataPiece();
+
+  // Helper to create NULL or ENUM types.
+  DataPiece(Type type, int32 val) : type_(type), i32_(val) {}
+
+  // For numeric conversion between
+  //     int32, int64, uint32, uint64, double, float and bool
+  template <typename To>
+  util::StatusOr<To> GenericConvert() const;
+
+  // For conversion from string to
+  //     int32, int64, uint32, uint64, double, float and bool
+  template <typename To>
+  util::StatusOr<To> StringToNumber(bool (*func)(StringPiece, To*)) const;
+
+  // Data type for this piece of data.
+  Type type_;
+
+  // StringPiece is not a POD and can not be used in an union (pre C++11). We
+  // need a POD version of it.
+  struct StringPiecePod {
+    const char* data;
+    int size;
+
+    // Create from a StringPiece.
+    static StringPiecePod CreateFromStringPiece(StringPiece str) {
+      StringPiecePod pod;
+      pod.data = str.data();
+      pod.size = str.size();
+      return pod;
+    }
+
+    // Cast to StringPiece.
+    operator StringPiece() const { return StringPiece(data, size); }
+
+    bool operator==(const char* value) const {
+      return StringPiece(data, size) == StringPiece(value);
+    }
+
+    string ToString() const { return string(data, size); }
+  };
+
+  // Stored piece of data.
+  union {
+    int32 i32_;
+    int64 i64_;
+    uint32 u32_;
+    uint64 u64_;
+    double double_;
+    float float_;
+    bool bool_;
+    StringPiecePod str_;
+  };
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_DATAPIECE_H__
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter.cc b/src/google/protobuf/util/internal/default_value_objectwriter.cc
new file mode 100644
index 0000000..a63e560
--- /dev/null
+++ b/src/google/protobuf/util/internal/default_value_objectwriter.cc
@@ -0,0 +1,559 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+
+#include <google/protobuf/stubs/hash.h>
+
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/map_util.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+using util::Status;
+using util::StatusOr;
+namespace converter {
+
+namespace {
+// Helper function to convert string value to given data type by calling the
+// passed converter function on the DataPiece created from "value" argument.
+// If value is empty or if conversion fails, the default_value is returned.
+template <typename T>
+T ConvertTo(StringPiece value, StatusOr<T> (DataPiece::*converter_fn)() const,
+            T default_value) {
+  if (value.empty()) return default_value;
+  StatusOr<T> result = (DataPiece(value).*converter_fn)();
+  return result.ok() ? result.ValueOrDie() : default_value;
+}
+}  // namespace
+
+DefaultValueObjectWriter::DefaultValueObjectWriter(
+    TypeResolver* type_resolver, const google::protobuf::Type& type,
+    ObjectWriter* ow)
+    : typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      own_typeinfo_(true),
+      type_(type),
+      current_(NULL),
+      root_(NULL),
+      ow_(ow) {}
+
+DefaultValueObjectWriter::~DefaultValueObjectWriter() {
+  for (int i = 0; i < string_values_.size(); ++i) {
+    delete string_values_[i];
+  }
+  if (own_typeinfo_) {
+    delete typeinfo_;
+  }
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderBool(StringPiece name,
+                                                               bool value) {
+  if (current_ == NULL) {
+    ow_->RenderBool(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderInt32(
+    StringPiece name, int32 value) {
+  if (current_ == NULL) {
+    ow_->RenderInt32(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderUint32(
+    StringPiece name, uint32 value) {
+  if (current_ == NULL) {
+    ow_->RenderUint32(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderInt64(
+    StringPiece name, int64 value) {
+  if (current_ == NULL) {
+    ow_->RenderInt64(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderUint64(
+    StringPiece name, uint64 value) {
+  if (current_ == NULL) {
+    ow_->RenderUint64(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderDouble(
+    StringPiece name, double value) {
+  if (current_ == NULL) {
+    ow_->RenderDouble(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderFloat(
+    StringPiece name, float value) {
+  if (current_ == NULL) {
+    ow_->RenderBool(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderString(
+    StringPiece name, StringPiece value) {
+  if (current_ == NULL) {
+    ow_->RenderString(name, value);
+  } else {
+    // Since StringPiece is essentially a pointer, takes a copy of "value" to
+    // avoid ownership issues.
+    string_values_.push_back(new string(value.ToString()));
+    RenderDataPiece(name, DataPiece(*string_values_.back()));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderBytes(
+    StringPiece name, StringPiece value) {
+  if (current_ == NULL) {
+    ow_->RenderBytes(name, value);
+  } else {
+    RenderDataPiece(name, DataPiece(value));
+  }
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::RenderNull(
+    StringPiece name) {
+  if (current_ == NULL) {
+    ow_->RenderNull(name);
+  } else {
+    RenderDataPiece(name, DataPiece::NullData());
+  }
+  return this;
+}
+
+DefaultValueObjectWriter::Node::Node(const string& name,
+                                     const google::protobuf::Type* type,
+                                     NodeKind kind, const DataPiece& data,
+                                     bool is_placeholder)
+    : name_(name),
+      type_(type),
+      kind_(kind),
+      is_any_(false),
+      data_(data),
+      is_placeholder_(is_placeholder) {}
+
+DefaultValueObjectWriter::Node* DefaultValueObjectWriter::Node::FindChild(
+    StringPiece name) {
+  if (name.empty() || kind_ != OBJECT) {
+    return NULL;
+  }
+  for (int i = 0; i < children_.size(); ++i) {
+    Node* child = children_[i];
+    if (child->name() == name) {
+      return child;
+    }
+  }
+  return NULL;
+}
+
+void DefaultValueObjectWriter::Node::WriteTo(ObjectWriter* ow) {
+  if (kind_ == PRIMITIVE) {
+    ObjectWriter::RenderDataPieceTo(data_, name_, ow);
+    return;
+  }
+
+  // Render maps. Empty maps are rendered as "{}".
+  if (kind_ == MAP) {
+    ow->StartObject(name_);
+    WriteChildren(ow);
+    ow->EndObject();
+    return;
+  }
+
+  // Write out lists. If we didn't have any list in response, write out empty
+  // list.
+  if (kind_ == LIST) {
+    ow->StartList(name_);
+    WriteChildren(ow);
+    ow->EndList();
+    return;
+  }
+
+  // If is_placeholder_ = true, we didn't see this node in the response, so
+  // skip output.
+  if (is_placeholder_) return;
+
+  ow->StartObject(name_);
+  WriteChildren(ow);
+  ow->EndObject();
+}
+
+void DefaultValueObjectWriter::Node::WriteChildren(ObjectWriter* ow) {
+  for (int i = 0; i < children_.size(); ++i) {
+    Node* child = children_[i];
+    child->WriteTo(ow);
+  }
+}
+
+const google::protobuf::Type* DefaultValueObjectWriter::Node::GetMapValueType(
+    const google::protobuf::Type& found_type, const TypeInfo* typeinfo) {
+  // If this field is a map, we should use the type of its "Value" as
+  // the type of the child node.
+  for (int i = 0; i < found_type.fields_size(); ++i) {
+    const google::protobuf::Field& sub_field = found_type.fields(i);
+    if (sub_field.number() != 2) {
+      continue;
+    }
+    if (sub_field.kind() != google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      // This map's value type is not a message type. We don't need to
+      // get the field_type in this case.
+      break;
+    }
+    util::StatusOr<const google::protobuf::Type*> sub_type =
+        typeinfo->ResolveTypeUrl(sub_field.type_url());
+    if (!sub_type.ok()) {
+      GOOGLE_LOG(WARNING) << "Cannot resolve type '" << sub_field.type_url() << "'.";
+    } else {
+      return sub_type.ValueOrDie();
+    }
+    break;
+  }
+  return NULL;
+}
+
+void DefaultValueObjectWriter::Node::PopulateChildren(
+    const TypeInfo* typeinfo) {
+  // Ignores well known types that don't require automatically populating their
+  // primitive children. For type "Any", we only populate its children when the
+  // "@type" field is set.
+  // TODO(tsun): remove "kStructValueType" from the list. It's being checked
+  //     now because of a bug in the tool-chain that causes the "oneof_index"
+  //     of kStructValueType to not be set correctly.
+  if (type_ == NULL || type_->name() == kAnyType ||
+      type_->name() == kStructType || type_->name() == kTimestampType ||
+      type_->name() == kDurationType || type_->name() == kStructValueType) {
+    return;
+  }
+  std::vector<Node*> new_children;
+  hash_map<string, int> orig_children_map;
+
+  // Creates a map of child nodes to speed up lookup.
+  for (int i = 0; i < children_.size(); ++i) {
+    InsertIfNotPresent(&orig_children_map, children_[i]->name_, i);
+  }
+
+  for (int i = 0; i < type_->fields_size(); ++i) {
+    const google::protobuf::Field& field = type_->fields(i);
+    hash_map<string, int>::iterator found =
+        orig_children_map.find(field.name());
+    // If the child field has already been set, we just add it to the new list
+    // of children.
+    if (found != orig_children_map.end()) {
+      new_children.push_back(children_[found->second]);
+      children_[found->second] = NULL;
+      continue;
+    }
+
+    const google::protobuf::Type* field_type = NULL;
+    bool is_map = false;
+    NodeKind kind = PRIMITIVE;
+
+    if (field.kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      kind = OBJECT;
+      util::StatusOr<const google::protobuf::Type*> found_result =
+          typeinfo->ResolveTypeUrl(field.type_url());
+      if (!found_result.ok()) {
+        // "field" is of an unknown type.
+        GOOGLE_LOG(WARNING) << "Cannot resolve type '" << field.type_url() << "'.";
+      } else {
+        const google::protobuf::Type* found_type = found_result.ValueOrDie();
+        is_map = IsMap(field, *found_type);
+
+        if (!is_map) {
+          field_type = found_type;
+        } else {
+          // If this field is a map, we should use the type of its "Value" as
+          // the type of the child node.
+          field_type = GetMapValueType(*found_type, typeinfo);
+          kind = MAP;
+        }
+      }
+    }
+
+    if (!is_map &&
+        field.cardinality() ==
+            google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+      kind = LIST;
+    }
+
+    // If oneof_index() != 0, the child field is part of a "oneof", which means
+    // the child field is optional and we shouldn't populate its default value.
+    if (field.oneof_index() != 0) continue;
+
+    // If the child field is of primitive type, sets its data to the default
+    // value of its type.
+    google::protobuf::scoped_ptr<Node> child(new Node(
+        field.json_name(), field_type, kind,
+        kind == PRIMITIVE ? CreateDefaultDataPieceForField(field, typeinfo)
+                          : DataPiece::NullData(),
+        true));
+    new_children.push_back(child.release());
+  }
+  // Adds all leftover nodes in children_ to the beginning of new_child.
+  for (int i = 0; i < children_.size(); ++i) {
+    if (children_[i] == NULL) {
+      continue;
+    }
+    new_children.insert(new_children.begin(), children_[i]);
+    children_[i] = NULL;
+  }
+  children_.swap(new_children);
+}
+
+void DefaultValueObjectWriter::MaybePopulateChildrenOfAny(Node* node) {
+  // If this is an "Any" node with "@type" already given and no other children
+  // have been added, populates its children.
+  if (node != NULL && node->is_any() && node->type() != NULL &&
+      node->type()->name() != kAnyType && node->number_of_children() == 1) {
+    node->PopulateChildren(typeinfo_);
+  }
+}
+
+DataPiece DefaultValueObjectWriter::FindEnumDefault(
+    const google::protobuf::Field& field, const TypeInfo* typeinfo) {
+  if (!field.default_value().empty()) return DataPiece(field.default_value());
+
+  const google::protobuf::Enum* enum_type =
+      typeinfo->GetEnumByTypeUrl(field.type_url());
+  if (!enum_type) {
+    GOOGLE_LOG(WARNING) << "Could not find enum with type '" << field.type_url()
+                 << "'";
+    return DataPiece::NullData();
+  }
+  // We treat the first value as the default if none is specified.
+  return enum_type->enumvalue_size() > 0
+             ? DataPiece(enum_type->enumvalue(0).name())
+             : DataPiece::NullData();
+}
+
+DataPiece DefaultValueObjectWriter::CreateDefaultDataPieceForField(
+    const google::protobuf::Field& field, const TypeInfo* typeinfo) {
+  switch (field.kind()) {
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      return DataPiece(ConvertTo<double>(
+          field.default_value(), &DataPiece::ToDouble, static_cast<double>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      return DataPiece(ConvertTo<float>(
+          field.default_value(), &DataPiece::ToFloat, static_cast<float>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64:
+    case google::protobuf::Field_Kind_TYPE_SINT64:
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      return DataPiece(ConvertTo<int64>(
+          field.default_value(), &DataPiece::ToInt64, static_cast<int64>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64:
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      return DataPiece(ConvertTo<uint64>(
+          field.default_value(), &DataPiece::ToUint64, static_cast<uint64>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_INT32:
+    case google::protobuf::Field_Kind_TYPE_SINT32:
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      return DataPiece(ConvertTo<int32>(
+          field.default_value(), &DataPiece::ToInt32, static_cast<int32>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      return DataPiece(
+          ConvertTo<bool>(field.default_value(), &DataPiece::ToBool, false));
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      return DataPiece(field.default_value());
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      return DataPiece(field.default_value(), false);
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32:
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      return DataPiece(ConvertTo<uint32>(
+          field.default_value(), &DataPiece::ToUint32, static_cast<uint32>(0)));
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      return FindEnumDefault(field, typeinfo);
+    }
+    default: { return DataPiece::NullData(); }
+  }
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::StartObject(
+    StringPiece name) {
+  if (current_ == NULL) {
+    root_.reset(new Node(name.ToString(), &type_, OBJECT, DataPiece::NullData(),
+                         false));
+    root_->PopulateChildren(typeinfo_);
+    current_ = root_.get();
+    return this;
+  }
+  MaybePopulateChildrenOfAny(current_);
+  Node* child = current_->FindChild(name);
+  if (current_->kind() == LIST || current_->kind() == MAP || child == NULL) {
+    // If current_ is a list or a map node, we should create a new child and use
+    // the type of current_ as the type of the new child.
+    google::protobuf::scoped_ptr<Node> node(new Node(
+        name.ToString(), ((current_->kind() == LIST || current_->kind() == MAP)
+                              ? current_->type()
+                              : NULL),
+        OBJECT, DataPiece::NullData(), false));
+    child = node.get();
+    current_->AddChild(node.release());
+  }
+
+  child->set_is_placeholder(false);
+  if (child->kind() == OBJECT && child->number_of_children() == 0) {
+    child->PopulateChildren(typeinfo_);
+  }
+
+  stack_.push(current_);
+  current_ = child;
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::EndObject() {
+  if (stack_.empty()) {
+    // The root object ends here. Writes out the tree.
+    WriteRoot();
+    return this;
+  }
+  current_ = stack_.top();
+  stack_.pop();
+  return this;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::StartList(
+    StringPiece name) {
+  if (current_ == NULL) {
+    root_.reset(
+        new Node(name.ToString(), &type_, LIST, DataPiece::NullData(), false));
+    current_ = root_.get();
+    return this;
+  }
+  MaybePopulateChildrenOfAny(current_);
+  Node* child = current_->FindChild(name);
+  if (child == NULL || child->kind() != LIST) {
+    google::protobuf::scoped_ptr<Node> node(
+        new Node(name.ToString(), NULL, LIST, DataPiece::NullData(), false));
+    child = node.get();
+    current_->AddChild(node.release());
+  }
+  child->set_is_placeholder(false);
+
+  stack_.push(current_);
+  current_ = child;
+  return this;
+}
+
+void DefaultValueObjectWriter::WriteRoot() {
+  root_->WriteTo(ow_);
+  root_.reset(NULL);
+  current_ = NULL;
+}
+
+DefaultValueObjectWriter* DefaultValueObjectWriter::EndList() {
+  if (stack_.empty()) {
+    WriteRoot();
+    return this;
+  }
+  current_ = stack_.top();
+  stack_.pop();
+  return this;
+}
+
+void DefaultValueObjectWriter::RenderDataPiece(StringPiece name,
+                                               const DataPiece& data) {
+  MaybePopulateChildrenOfAny(current_);
+  util::StatusOr<string> data_string = data.ToString();
+  if (current_->type() != NULL && current_->type()->name() == kAnyType &&
+      name == "@type" && data_string.ok()) {
+    const string& string_value = data_string.ValueOrDie();
+    // If the type of current_ is "Any" and its "@type" field is being set here,
+    // sets the type of current_ to be the type specified by the "@type".
+    util::StatusOr<const google::protobuf::Type*> found_type =
+        typeinfo_->ResolveTypeUrl(string_value);
+    if (!found_type.ok()) {
+      GOOGLE_LOG(WARNING) << "Failed to resolve type '" << string_value << "'.";
+    } else {
+      current_->set_type(found_type.ValueOrDie());
+    }
+    current_->set_is_any(true);
+    // If the "@type" field is placed after other fields, we should populate
+    // other children of primitive type now. Otherwise, we should wait until the
+    // first value field is rendered before we populate the children, because
+    // the "value" field of a Any message could be omitted.
+    if (current_->number_of_children() > 1 && current_->type() != NULL) {
+      current_->PopulateChildren(typeinfo_);
+    }
+  }
+  Node* child = current_->FindChild(name);
+  if (child == NULL || child->kind() != PRIMITIVE) {
+    // No children are found, creates a new child.
+    google::protobuf::scoped_ptr<Node> node(
+        new Node(name.ToString(), NULL, PRIMITIVE, data, false));
+    child = node.get();
+    current_->AddChild(node.release());
+  } else {
+    child->set_data(data);
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter.h b/src/google/protobuf/util/internal/default_value_objectwriter.h
new file mode 100644
index 0000000..695b9dd
--- /dev/null
+++ b/src/google/protobuf/util/internal/default_value_objectwriter.h
@@ -0,0 +1,234 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_DEFAULT_VALUE_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_DEFAULT_VALUE_OBJECTWRITER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <stack>
+#include <vector>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/datapiece.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An ObjectWriter that renders non-repeated primitive fields of proto messages
+// with their default values. DefaultValueObjectWriter holds objects, lists and
+// fields it receives in a tree structure and writes them out to another
+// ObjectWriter when EndObject() is called on the root object. It also writes
+// out all non-repeated primitive fields that haven't been explicitly rendered
+// with their default values (0 for numbers, "" for strings, etc).
+class LIBPROTOBUF_EXPORT DefaultValueObjectWriter : public ObjectWriter {
+ public:
+  DefaultValueObjectWriter(TypeResolver* type_resolver,
+                           const google::protobuf::Type& type,
+                           ObjectWriter* ow);
+
+  virtual ~DefaultValueObjectWriter();
+
+  // ObjectWriter methods.
+  virtual DefaultValueObjectWriter* StartObject(StringPiece name);
+
+  virtual DefaultValueObjectWriter* EndObject();
+
+  virtual DefaultValueObjectWriter* StartList(StringPiece name);
+
+  virtual DefaultValueObjectWriter* EndList();
+
+  virtual DefaultValueObjectWriter* RenderBool(StringPiece name, bool value);
+
+  virtual DefaultValueObjectWriter* RenderInt32(StringPiece name, int32 value);
+
+  virtual DefaultValueObjectWriter* RenderUint32(StringPiece name,
+                                                 uint32 value);
+
+  virtual DefaultValueObjectWriter* RenderInt64(StringPiece name, int64 value);
+
+  virtual DefaultValueObjectWriter* RenderUint64(StringPiece name,
+                                                 uint64 value);
+
+  virtual DefaultValueObjectWriter* RenderDouble(StringPiece name,
+                                                 double value);
+
+  virtual DefaultValueObjectWriter* RenderFloat(StringPiece name, float value);
+
+  virtual DefaultValueObjectWriter* RenderString(StringPiece name,
+                                                 StringPiece value);
+  virtual DefaultValueObjectWriter* RenderBytes(StringPiece name,
+                                                StringPiece value);
+
+  virtual DefaultValueObjectWriter* RenderNull(StringPiece name);
+
+ private:
+  enum NodeKind {
+    PRIMITIVE = 0,
+    OBJECT = 1,
+    LIST = 2,
+    MAP = 3,
+  };
+
+  // "Node" represents a node in the tree that holds the input of
+  // DefaultValueObjectWriter.
+  class LIBPROTOBUF_EXPORT Node {
+   public:
+    Node(const string& name, const google::protobuf::Type* type, NodeKind kind,
+         const DataPiece& data, bool is_placeholder);
+    virtual ~Node() {
+      for (int i = 0; i < children_.size(); ++i) {
+        delete children_[i];
+      }
+    }
+
+    // Adds a child to this node. Takes ownership of this child.
+    void AddChild(Node* child) { children_.push_back(child); }
+
+    // Finds the child given its name.
+    Node* FindChild(StringPiece name);
+
+    // Populates children of this Node based on its type. If there are already
+    // children created, they will be merged to the result. Caller should pass
+    // in TypeInfo for looking up types of the children.
+    void PopulateChildren(const TypeInfo* typeinfo);
+
+    // If this node is a leaf (has data), writes the current node to the
+    // ObjectWriter; if not, then recursively writes the children to the
+    // ObjectWriter.
+    void WriteTo(ObjectWriter* ow);
+
+    // Accessors
+    const string& name() const { return name_; }
+
+    const google::protobuf::Type* type() { return type_; }
+
+    void set_type(const google::protobuf::Type* type) { type_ = type; }
+
+    NodeKind kind() { return kind_; }
+
+    int number_of_children() { return children_.size(); }
+
+    void set_data(const DataPiece& data) { data_ = data; }
+
+    bool is_any() { return is_any_; }
+
+    void set_is_any(bool is_any) { is_any_ = is_any; }
+
+    void set_is_placeholder(bool is_placeholder) {
+      is_placeholder_ = is_placeholder;
+    }
+
+   private:
+    // Returns the Value Type of a map given the Type of the map entry and a
+    // TypeInfo instance.
+    const google::protobuf::Type* GetMapValueType(
+        const google::protobuf::Type& entry_type, const TypeInfo* typeinfo);
+
+    // Calls WriteTo() on every child in children_.
+    void WriteChildren(ObjectWriter* ow);
+
+    // The name of this node.
+    string name_;
+    // google::protobuf::Type of this node. Owned by TypeInfo.
+    const google::protobuf::Type* type_;
+    // The kind of this node.
+    NodeKind kind_;
+    // Whether this is a node for "Any".
+    bool is_any_;
+    // The data of this node when it is a leaf node.
+    DataPiece data_;
+    // Children of this node.
+    std::vector<Node*> children_;
+    // Whether this node is a placeholder for an object or list automatically
+    // generated when creating the parent node. Should be set to false after
+    // the parent node's StartObject()/StartList() method is called with this
+    // node's name.
+    bool is_placeholder_;
+  };
+
+  // Populates children of "node" if it is an "any" Node and its real type has
+  // been given.
+  void MaybePopulateChildrenOfAny(Node* node);
+
+  // Writes the root_ node to ow_ and resets the root_ and current_ pointer to
+  // NULL.
+  void WriteRoot();
+
+  // Creates a DataPiece containing the default value of the type of the field.
+  static DataPiece CreateDefaultDataPieceForField(
+      const google::protobuf::Field& field, const TypeInfo* typeinfo);
+
+  // Adds or replaces the data_ of a primitive child node.
+  void RenderDataPiece(StringPiece name, const DataPiece& data);
+
+  // Returns the default enum value as a DataPiece, or the first enum value if
+  // there is no default. For proto3, where we cannot specify an explicit
+  // default, a zero value will always be returned.
+  static DataPiece FindEnumDefault(const google::protobuf::Field& field,
+                                   const TypeInfo* typeinfo);
+
+  // Type information for all the types used in the descriptor. Used to find
+  // google::protobuf::Type of nested messages/enums.
+  const TypeInfo* typeinfo_;
+  // Whether the TypeInfo object is owned by this class.
+  bool own_typeinfo_;
+  // google::protobuf::Type of the root message type.
+  const google::protobuf::Type& type_;
+  // Holds copies of strings passed to RenderString.
+  vector<string*> string_values_;
+
+  // The current Node. Owned by its parents.
+  Node* current_;
+  // The root Node.
+  google::protobuf::scoped_ptr<Node> root_;
+  // The stack to hold the path of Nodes from current_ to root_;
+  std::stack<Node*> stack_;
+
+  ObjectWriter* ow_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(DefaultValueObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_DEFAULT_VALUE_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/default_value_objectwriter_test.cc b/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
new file mode 100644
index 0000000..8254c0f
--- /dev/null
+++ b/src/google/protobuf/util/internal/default_value_objectwriter_test.cc
@@ -0,0 +1,156 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <google/protobuf/util/internal/testdata/default_value_test.pb.h>
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+namespace testing {
+
+using google::protobuf::testing::DefaultValueTest;
+
+// Base class for setting up required state for running default values tests on
+// different descriptors.
+class BaseDefaultValueObjectWriterTest
+    : public ::testing::TestWithParam<testing::TypeInfoSource> {
+ protected:
+  explicit BaseDefaultValueObjectWriterTest(const Descriptor* descriptor)
+      : helper_(GetParam()), mock_(), expects_(&mock_) {
+    helper_.ResetTypeInfo(descriptor);
+    testing_.reset(helper_.NewDefaultValueWriter(
+        string(kTypeServiceBaseUrl) + "/" + descriptor->full_name(), &mock_));
+  }
+
+  virtual ~BaseDefaultValueObjectWriterTest() {}
+
+  TypeInfoTestHelper helper_;
+  MockObjectWriter mock_;
+  ExpectingObjectWriter expects_;
+  google::protobuf::scoped_ptr<DefaultValueObjectWriter> testing_;
+};
+
+// Tests to cover some basic DefaultValueObjectWriter use cases. More tests are
+// in the marshalling_test.cc and translator_integration_test.cc.
+class DefaultValueObjectWriterTest : public BaseDefaultValueObjectWriterTest {
+ protected:
+  DefaultValueObjectWriterTest()
+      : BaseDefaultValueObjectWriterTest(DefaultValueTest::descriptor()) {}
+  virtual ~DefaultValueObjectWriterTest() {}
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        DefaultValueObjectWriterTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(DefaultValueObjectWriterTest, Empty) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderDouble("doubleValue", 0.0)
+      ->StartList("repeatedDouble")
+      ->EndList()
+      ->RenderFloat("floatValue", 0.0)
+      ->RenderInt64("int64Value", 0)
+      ->RenderUint64("uint64Value", 0)
+      ->RenderInt32("int32Value", 0)
+      ->RenderUint32("uint32Value", 0)
+      ->RenderBool("boolValue", false)
+      ->RenderString("stringValue", "")
+      ->RenderBytes("bytesValue", "")
+      ->RenderString("enumValue", "ENUM_FIRST")
+      ->EndObject();
+
+  // Actual testing
+  testing_->StartObject("")->EndObject();
+}
+
+TEST_P(DefaultValueObjectWriterTest, NonDefaultDouble) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderDouble("doubleValue", 1.0)
+      ->StartList("repeatedDouble")
+      ->EndList()
+      ->RenderFloat("floatValue", 0.0)
+      ->RenderInt64("int64Value", 0)
+      ->RenderUint64("uint64Value", 0)
+      ->RenderInt32("int32Value", 0)
+      ->RenderUint32("uint32Value", 0)
+      ->RenderBool("boolValue", false)
+      ->RenderString("stringValue", "")
+      ->RenderString("enumValue", "ENUM_FIRST")
+      ->EndObject();
+
+  // Actual testing
+  testing_->StartObject("")->RenderDouble("doubleValue", 1.0)->EndObject();
+}
+
+TEST_P(DefaultValueObjectWriterTest, ShouldRetainUnknownField) {
+  // Set expectation
+  expects_.StartObject("")
+      ->RenderDouble("doubleValue", 1.0)
+      ->StartList("repeatedDouble")
+      ->EndList()
+      ->RenderFloat("floatValue", 0.0)
+      ->RenderInt64("int64Value", 0)
+      ->RenderUint64("uint64Value", 0)
+      ->RenderInt32("int32Value", 0)
+      ->RenderUint32("uint32Value", 0)
+      ->RenderBool("boolValue", false)
+      ->RenderString("stringValue", "")
+      ->RenderString("unknown", "abc")
+      ->StartObject("unknownObject")
+      ->RenderString("unknown", "def")
+      ->EndObject()
+      ->RenderString("enumValue", "ENUM_FIRST")
+      ->EndObject();
+
+  // Actual testing
+  testing_->StartObject("")
+      ->RenderDouble("doubleValue", 1.0)
+      ->RenderString("unknown", "abc")
+      ->StartObject("unknownObject")
+      ->RenderString("unknown", "def")
+      ->EndObject()
+      ->EndObject();
+}
+
+
+}  // namespace testing
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/error_listener.cc b/src/google/protobuf/util/internal/error_listener.cc
new file mode 100644
index 0000000..538307b
--- /dev/null
+++ b/src/google/protobuf/util/internal/error_listener.cc
@@ -0,0 +1,42 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/error_listener.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/error_listener.h b/src/google/protobuf/util/internal/error_listener.h
new file mode 100644
index 0000000..3f06393
--- /dev/null
+++ b/src/google/protobuf/util/internal/error_listener.h
@@ -0,0 +1,103 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
+
+#include <algorithm>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+#include <vector>
+
+#include <google/protobuf/stubs/callback.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/util/internal/location_tracker.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// Interface for error listener.
+class LIBPROTOBUF_EXPORT ErrorListener {
+ public:
+  virtual ~ErrorListener() {}
+
+  // Reports an invalid name at the given location.
+  virtual void InvalidName(const LocationTrackerInterface& loc,
+                           StringPiece unknown_name, StringPiece message) = 0;
+
+  // Reports an invalid value for a field.
+  virtual void InvalidValue(const LocationTrackerInterface& loc,
+                            StringPiece type_name, StringPiece value) = 0;
+
+  // Reports a missing required field.
+  virtual void MissingField(const LocationTrackerInterface& loc,
+                            StringPiece missing_name) = 0;
+
+ protected:
+  ErrorListener() {}
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ErrorListener);
+};
+
+// An error listener that ignores all errors.
+class LIBPROTOBUF_EXPORT NoopErrorListener : public ErrorListener {
+ public:
+  NoopErrorListener() {}
+  virtual ~NoopErrorListener() {}
+
+  virtual void InvalidName(const LocationTrackerInterface& loc,
+                           StringPiece unknown_name, StringPiece message) {}
+
+  virtual void InvalidValue(const LocationTrackerInterface& loc,
+                            StringPiece type_name, StringPiece value) {}
+
+  virtual void MissingField(const LocationTrackerInterface& loc,
+                            StringPiece missing_name) {}
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(NoopErrorListener);
+};
+
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_ERROR_LISTENER_H__
diff --git a/src/google/protobuf/util/internal/expecting_objectwriter.h b/src/google/protobuf/util/internal/expecting_objectwriter.h
new file mode 100644
index 0000000..ae98ddd
--- /dev/null
+++ b/src/google/protobuf/util/internal/expecting_objectwriter.h
@@ -0,0 +1,238 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_EXPECTING_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_EXPECTING_OBJECTWRITER_H__
+
+// An implementation of ObjectWriter that automatically sets the
+// gmock expectations for the response to a method. Every method
+// returns the object itself for chaining.
+//
+// Usage:
+//   // Setup
+//   MockObjectWriter mock;
+//   ExpectingObjectWriter ow(&mock);
+//
+//   // Set expectation
+//   ow.StartObject("")
+//       ->RenderString("key", "value")
+//     ->EndObject();
+//
+//   // Actual testing
+//   mock.StartObject(StringPiece())
+//         ->RenderString("key", "value")
+//       ->EndObject();
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <gmock/gmock.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using testing::IsEmpty;
+using testing::NanSensitiveDoubleEq;
+using testing::NanSensitiveFloatEq;
+using testing::Return;
+using testing::StrEq;
+using testing::TypedEq;
+
+class MockObjectWriter : public ObjectWriter {
+ public:
+  MockObjectWriter() {}
+
+  MOCK_METHOD1(StartObject, ObjectWriter*(StringPiece));
+  MOCK_METHOD0(EndObject, ObjectWriter*());
+  MOCK_METHOD1(StartList, ObjectWriter*(StringPiece));
+  MOCK_METHOD0(EndList, ObjectWriter*());
+  MOCK_METHOD2(RenderBool, ObjectWriter*(StringPiece, bool));
+  MOCK_METHOD2(RenderInt32, ObjectWriter*(StringPiece, int32));
+  MOCK_METHOD2(RenderUint32, ObjectWriter*(StringPiece, uint32));
+  MOCK_METHOD2(RenderInt64, ObjectWriter*(StringPiece, int64));
+  MOCK_METHOD2(RenderUint64, ObjectWriter*(StringPiece, uint64));
+  MOCK_METHOD2(RenderDouble, ObjectWriter*(StringPiece, double));
+  MOCK_METHOD2(RenderFloat, ObjectWriter*(StringPiece, float));
+  MOCK_METHOD2(RenderString, ObjectWriter*(StringPiece, StringPiece));
+  MOCK_METHOD2(RenderBytes, ObjectWriter*(StringPiece, StringPiece));
+  MOCK_METHOD1(RenderNull, ObjectWriter*(StringPiece));
+};
+
+class ExpectingObjectWriter : public ObjectWriter {
+ public:
+  explicit ExpectingObjectWriter(MockObjectWriter* mock) : mock_(mock) {}
+
+  virtual ObjectWriter* StartObject(StringPiece name) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, StartObject(IsEmpty()))
+         : EXPECT_CALL(*mock_, StartObject(StrEq(name.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* EndObject() {
+    EXPECT_CALL(*mock_, EndObject())
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* StartList(StringPiece name) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, StartList(IsEmpty()))
+         : EXPECT_CALL(*mock_, StartList(StrEq(name.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* EndList() {
+    EXPECT_CALL(*mock_, EndList())
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderBool(StringPiece name, bool value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderBool(IsEmpty(), TypedEq<bool>(value)))
+         : EXPECT_CALL(*mock_, RenderBool(StrEq(name.ToString()),
+                                          TypedEq<bool>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderInt32(StringPiece name, int32 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderInt32(IsEmpty(), TypedEq<int32>(value)))
+         : EXPECT_CALL(*mock_, RenderInt32(StrEq(name.ToString()),
+                                           TypedEq<int32>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderUint32(StringPiece name, uint32 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderUint32(IsEmpty(), TypedEq<uint32>(value)))
+         : EXPECT_CALL(*mock_, RenderUint32(StrEq(name.ToString()),
+                                            TypedEq<uint32>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderInt64(StringPiece name, int64 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderInt64(IsEmpty(), TypedEq<int64>(value)))
+         : EXPECT_CALL(*mock_, RenderInt64(StrEq(name.ToString()),
+                                           TypedEq<int64>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderUint64(StringPiece name, uint64 value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderUint64(IsEmpty(), TypedEq<uint64>(value)))
+         : EXPECT_CALL(*mock_, RenderUint64(StrEq(name.ToString()),
+                                            TypedEq<uint64>(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderDouble(StringPiece name, double value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderDouble(IsEmpty(),
+                                            NanSensitiveDoubleEq(value)))
+         : EXPECT_CALL(*mock_, RenderDouble(StrEq(name.ToString()),
+                                            NanSensitiveDoubleEq(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderFloat(StringPiece name, float value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderFloat(IsEmpty(),
+                                           NanSensitiveFloatEq(value)))
+         : EXPECT_CALL(*mock_, RenderFloat(StrEq(name.ToString()),
+                                           NanSensitiveFloatEq(value))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderString(StringPiece name, StringPiece value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderString(IsEmpty(),
+               TypedEq<StringPiece>(value.ToString())))
+         : EXPECT_CALL(*mock_, RenderString(StrEq(name.ToString()),
+               TypedEq<StringPiece>(value.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+  virtual ObjectWriter* RenderBytes(StringPiece name, StringPiece value) {
+    (name.empty()
+         ? EXPECT_CALL(*mock_, RenderBytes(IsEmpty(), TypedEq<StringPiece>(
+                                                          value.ToString())))
+         : EXPECT_CALL(*mock_,
+                       RenderBytes(StrEq(name.ToString()),
+                                   TypedEq<StringPiece>(value.ToString()))))
+        .WillOnce(Return(mock_))
+        .RetiresOnSaturation();
+    return this;
+  }
+
+  virtual ObjectWriter* RenderNull(StringPiece name) {
+    (name.empty() ? EXPECT_CALL(*mock_, RenderNull(IsEmpty()))
+                  : EXPECT_CALL(*mock_, RenderNull(StrEq(name.ToString())))
+                        .WillOnce(Return(mock_))
+                        .RetiresOnSaturation());
+    return this;
+  }
+
+ private:
+  MockObjectWriter* mock_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ExpectingObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_EXPECTING_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/field_mask_utility.cc b/src/google/protobuf/util/internal/field_mask_utility.cc
new file mode 100644
index 0000000..f0e8fc8
--- /dev/null
+++ b/src/google/protobuf/util/internal/field_mask_utility.cc
@@ -0,0 +1,225 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/field_mask_utility.h>
+
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/status_macros.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+inline util::Status CallPathSink(PathSinkCallback path_sink,
+                                   StringPiece arg) {
+  return path_sink->Run(arg);
+}
+
+util::Status CreatePublicError(util::error::Code code,
+                                 const string& message) {
+  return util::Status(code, message);
+}
+
+// Appends a FieldMask path segment to a prefix.
+string AppendPathSegmentToPrefix(StringPiece prefix, StringPiece segment) {
+  if (prefix.empty()) {
+    return segment.ToString();
+  }
+  if (segment.empty()) {
+    return prefix.ToString();
+  }
+  // If the segment is a map key, appends it to the prefix without the ".".
+  if (segment.starts_with("[\"")) {
+    return StrCat(prefix, segment);
+  }
+  return StrCat(prefix, ".", segment);
+}
+
+}  // namespace
+
+string ConvertFieldMaskPath(const StringPiece path,
+                            ConverterCallback converter) {
+  string result;
+  result.reserve(path.size() << 1);
+
+  bool is_quoted = false;
+  bool is_escaping = false;
+  int current_segment_start = 0;
+
+  // Loops until 1 passed the end of the input to make handling the last
+  // segment easier.
+  for (size_t i = 0; i <= path.size(); ++i) {
+    // Outputs quoted string as-is.
+    if (is_quoted) {
+      if (i == path.size()) {
+        break;
+      }
+      result.push_back(path[i]);
+      if (is_escaping) {
+        is_escaping = false;
+      } else if (path[i] == '\\') {
+        is_escaping = true;
+      } else if (path[i] == '\"') {
+        current_segment_start = i + 1;
+        is_quoted = false;
+      }
+      continue;
+    }
+    if (i == path.size() || path[i] == '.' || path[i] == '(' ||
+        path[i] == ')' || path[i] == '\"') {
+      result += converter(
+          path.substr(current_segment_start, i - current_segment_start));
+      if (i < path.size()) {
+        result.push_back(path[i]);
+      }
+      current_segment_start = i + 1;
+    }
+    if (i < path.size() && path[i] == '\"') {
+      is_quoted = true;
+    }
+  }
+  return result;
+}
+
+util::Status DecodeCompactFieldMaskPaths(StringPiece paths,
+                                           PathSinkCallback path_sink) {
+  stack<string> prefix;
+  int length = paths.length();
+  int previous_position = 0;
+  bool in_map_key = false;
+  bool is_escaping = false;
+  // Loops until 1 passed the end of the input to make the handle of the last
+  // segment easier.
+  for (int i = 0; i <= length; ++i) {
+    if (i != length) {
+      // Skips everything in a map key until we hit the end of it, which is
+      // marked by an un-escaped '"' immediately followed by a ']'.
+      if (in_map_key) {
+        if (is_escaping) {
+          is_escaping = false;
+          continue;
+        }
+        if (paths[i] == '\\') {
+          is_escaping = true;
+          continue;
+        }
+        if (paths[i] != '\"') {
+          continue;
+        }
+        // Un-escaped '"' must be followed with a ']'.
+        if (i >= length - 1 || paths[i + 1] != ']') {
+          return util::Status(
+              util::error::INVALID_ARGUMENT,
+              StrCat("Invalid FieldMask '", paths,
+                     "'. Map keys should be represented as [\"some_key\"]."));
+        }
+        // The end of the map key ("\"]") has been found.
+        in_map_key = false;
+        // Skips ']'.
+        i++;
+        // Checks whether the key ends at the end of a path segment.
+        if (i < length - 1 && paths[i + 1] != '.' && paths[i + 1] != ',' &&
+            paths[i + 1] != ')' && paths[i + 1] != '(') {
+          return util::Status(
+              util::error::INVALID_ARGUMENT,
+              StrCat("Invalid FieldMask '", paths,
+                     "'. Map keys should be at the end of a path segment."));
+        }
+        is_escaping = false;
+        continue;
+      }
+
+      // We are not in a map key, look for the start of one.
+      if (paths[i] == '[') {
+        if (i >= length - 1 || paths[i + 1] != '\"') {
+          return util::Status(
+              util::error::INVALID_ARGUMENT,
+              StrCat("Invalid FieldMask '", paths,
+                     "'. Map keys should be represented as [\"some_key\"]."));
+        }
+        // "[\"" starts a map key.
+        in_map_key = true;
+        i++;  // Skips the '\"'.
+        continue;
+      }
+      // If the current character is not a special character (',', '(' or ')'),
+      // continue to the next.
+      if (paths[i] != ',' && paths[i] != ')' && paths[i] != '(') {
+        continue;
+      }
+    }
+    // Gets the current segment - sub-string between previous position (after
+    // '(', ')', ',', or the beginning of the input) and the current position.
+    StringPiece segment =
+        paths.substr(previous_position, i - previous_position);
+    string current_prefix = prefix.empty() ? "" : prefix.top();
+
+    if (i < length && paths[i] == '(') {
+      // Builds a prefix and save it into the stack.
+      prefix.push(AppendPathSegmentToPrefix(current_prefix, segment));
+    } else if (!segment.empty()) {
+      // When the current charactor is ')', ',' or the current position has
+      // passed the end of the input, builds and outputs a new paths by
+      // concatenating the last prefix with the current segment.
+      RETURN_IF_ERROR(CallPathSink(
+          path_sink, AppendPathSegmentToPrefix(current_prefix, segment)));
+    }
+
+    // Removes the last prefix after seeing a ')'.
+    if (i < length && paths[i] == ')') {
+      if (prefix.empty()) {
+        return util::Status(
+            util::error::INVALID_ARGUMENT,
+            StrCat("Invalid FieldMask '", paths,
+                   "'. Cannot find matching '(' for all ')'."));
+      }
+      prefix.pop();
+    }
+    previous_position = i + 1;
+  }
+  if (in_map_key) {
+    return util::Status(util::error::INVALID_ARGUMENT,
+                          StrCat("Invalid FieldMask '", paths,
+                                 "'. Cannot find matching ']' for all '['."));
+  }
+  if (!prefix.empty()) {
+    return util::Status(util::error::INVALID_ARGUMENT,
+                          StrCat("Invalid FieldMask '", paths,
+                                 "'. Cannot find matching ')' for all '('."));
+  }
+  return util::Status::OK;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/field_mask_utility.h b/src/google/protobuf/util/internal/field_mask_utility.h
new file mode 100644
index 0000000..59f36f7
--- /dev/null
+++ b/src/google/protobuf/util/internal/field_mask_utility.h
@@ -0,0 +1,72 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// FieldMask related utility methods.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_FIELD_MASK_UTILITY_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_FIELD_MASK_UTILITY_H__
+
+#include <functional>
+#include <stack>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+typedef string (*ConverterCallback)(StringPiece);
+typedef ResultCallback1<util::Status, StringPiece>* PathSinkCallback;
+
+// Applies a 'converter' to each segment of a FieldMask path and returns the
+// result. Quoted strings in the 'path' are copied to the output as-is without
+// converting their content. Escaping is supported within quoted strings.
+// For example, "ab\"_c" will be returned as "ab\"_c" without any changes.
+string ConvertFieldMaskPath(const StringPiece path,
+                            ConverterCallback converter);
+
+// Decodes a compact list of FieldMasks. For example, "a.b,a.c.d,a.c.e" will be
+// decoded into a list of field paths - "a.b", "a.c.d", "a.c.e". And the results
+// will be sent to 'path_sink', i.e. 'path_sink' will be called once per
+// resulting path.
+// Note that we also support Apiary style FieldMask form. The above example in
+// the Apiary style will look like "a.b,a.c(d,e)".
+util::Status DecodeCompactFieldMaskPaths(StringPiece paths,
+                                           PathSinkCallback path_sink);
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_FIELD_MASK_UTILITY_H__
diff --git a/src/google/protobuf/util/internal/json_escaping.cc b/src/google/protobuf/util/internal/json_escaping.cc
new file mode 100644
index 0000000..24bd554
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_escaping.cc
@@ -0,0 +1,404 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_escaping.h>
+
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+
+// Array of hex characters for conversion to hex.
+static const char kHex[] = "0123456789abcdef";
+
+// Characters 0x00 to 0x9f are very commonly used, so we provide a special
+// table lookup.
+//
+// For unicode code point ch < 0xa0:
+// kCommonEscapes[ch] is the escaped string of ch, if escaping is needed;
+//                    or an empty string, if escaping is not needed.
+static const char kCommonEscapes[160][7] = {
+  // C0 (ASCII and derivatives) control characters
+  "\\u0000", "\\u0001", "\\u0002", "\\u0003",  // 0x00
+  "\\u0004", "\\u0005", "\\u0006", "\\u0007",
+  "\\b",     "\\t",     "\\n",     "\\u000b",
+  "\\f",     "\\r",     "\\u000e", "\\u000f",
+  "\\u0010", "\\u0011", "\\u0012", "\\u0013",  // 0x10
+  "\\u0014", "\\u0015", "\\u0016", "\\u0017",
+  "\\u0018", "\\u0019", "\\u001a", "\\u001b",
+  "\\u001c", "\\u001d", "\\u001e", "\\u001f",
+  // Escaping of " and \ are required by www.json.org string definition.
+  // Escaping of < and > are required for HTML security.
+  "", "", "\\\"", "", "",        "", "",        "",  // 0x20
+  "", "", "",     "", "",        "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x30
+  "", "", "",     "", "\\u003c", "", "\\u003e", "",
+  "", "", "",     "", "",        "", "",        "",  // 0x40
+  "", "", "",     "", "",        "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x50
+  "", "", "",     "", "\\\\",    "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x60
+  "", "", "",     "", "",        "", "",        "",
+  "", "", "",     "", "",        "", "",        "",  // 0x70
+  "", "", "",     "", "",        "", "",        "\\u007f",
+  // C1 (ISO 8859 and Unicode) extended control characters
+  "\\u0080", "\\u0081", "\\u0082", "\\u0083",  // 0x80
+  "\\u0084", "\\u0085", "\\u0086", "\\u0087",
+  "\\u0088", "\\u0089", "\\u008a", "\\u008b",
+  "\\u008c", "\\u008d", "\\u008e", "\\u008f",
+  "\\u0090", "\\u0091", "\\u0092", "\\u0093",  // 0x90
+  "\\u0094", "\\u0095", "\\u0096", "\\u0097",
+  "\\u0098", "\\u0099", "\\u009a", "\\u009b",
+  "\\u009c", "\\u009d", "\\u009e", "\\u009f"
+};
+
+// Determines if the given char value is a unicode high-surrogate code unit.
+// Such values do not represent characters by themselves, but are used in the
+// representation of supplementary characters in the utf-16 encoding.
+inline bool IsHighSurrogate(uint16 c) {
+  // Optimized form of:
+  // return c >= kMinHighSurrogate && c <= kMaxHighSurrogate;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (c & ~(JsonEscaping::kMaxHighSurrogate -
+                JsonEscaping::kMinHighSurrogate))
+      == JsonEscaping::kMinHighSurrogate;
+}
+
+// Determines if the given char value is a unicode low-surrogate code unit.
+// Such values do not represent characters by themselves, but are used in the
+// representation of supplementary characters in the utf-16 encoding.
+inline bool IsLowSurrogate(uint16 c) {
+  // Optimized form of:
+  // return c >= kMinLowSurrogate && c <= kMaxLowSurrogate;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (c & ~(JsonEscaping::kMaxLowSurrogate -
+                JsonEscaping::kMinLowSurrogate))
+      == JsonEscaping::kMinLowSurrogate;
+}
+
+// Determines if the given char value is a unicode surrogate code unit (either
+// high-surrogate or low-surrogate).
+inline bool IsSurrogate(uint32 c) {
+  // Optimized form of:
+  // return c >= kMinHighSurrogate && c <= kMaxLowSurrogate;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (c & 0xfffff800) == JsonEscaping::kMinHighSurrogate;
+}
+
+// Returns true if the given unicode code point cp is
+// in the supplementary character range.
+inline bool IsSupplementalCodePoint(uint32 cp) {
+  // Optimized form of:
+  // return kMinSupplementaryCodePoint <= cp && cp <= kMaxCodePoint;
+  // (Reduced from 3 ALU instructions to 2 ALU instructions)
+  return (cp & ~(JsonEscaping::kMinSupplementaryCodePoint - 1))
+      < JsonEscaping::kMaxCodePoint;
+}
+
+// Returns true if the given unicode code point cp is a valid
+// unicode code point (i.e. in the range 0 <= cp <= kMaxCodePoint).
+inline bool IsValidCodePoint(uint32 cp) {
+  return cp <= JsonEscaping::kMaxCodePoint;
+}
+
+// Converts the specified surrogate pair to its supplementary code point value.
+// It is the callers' responsibility to validate the specified surrogate pair.
+inline uint32 ToCodePoint(uint16 high, uint16 low) {
+  // Optimized form of:
+  // return ((high - kMinHighSurrogate) << 10)
+  //     + (low - kMinLowSurrogate)
+  //     + kMinSupplementaryCodePoint;
+  // (Reduced from 5 ALU instructions to 3 ALU instructions)
+  return (high << 10) + low +
+      (JsonEscaping::kMinSupplementaryCodePoint
+       - (static_cast<unsigned>(JsonEscaping::kMinHighSurrogate) << 10)
+       - JsonEscaping::kMinLowSurrogate);
+}
+
+// Returns the low surrogate for the given unicode code point. The result is
+// meaningless if the given code point is not a supplementary character.
+inline uint16 ToLowSurrogate(uint32 cp) {
+  return (cp & (JsonEscaping::kMaxLowSurrogate
+                - JsonEscaping::kMinLowSurrogate))
+      + JsonEscaping::kMinLowSurrogate;
+}
+
+// Returns the high surrogate for the given unicode code point. The result is
+// meaningless if the given code point is not a supplementary character.
+inline uint16 ToHighSurrogate(uint32 cp) {
+  return (cp >> 10) + (JsonEscaping::kMinHighSurrogate -
+                       (JsonEscaping::kMinSupplementaryCodePoint >> 10));
+}
+
+// Input str is encoded in UTF-8. A unicode code point could be encoded in
+// UTF-8 using anywhere from 1 to 4 characters, and it could span multiple
+// reads of the ByteSource.
+//
+// This function reads the next unicode code point from the input (str) at
+// the given position (index), taking into account any left-over partial
+// code point from the previous iteration (cp), together with the number
+// of characters left to read to complete this code point (num_left).
+//
+// This function assumes that the input (str) is valid at the given position
+// (index). In order words, at least one character could be read successfully.
+//
+// The code point read (partial or complete) is stored in (cp). Upon return,
+// (num_left) stores the number of characters that has yet to be read in
+// order to complete the current unicode code point. If the read is complete,
+// then (num_left) is 0. Also, (num_read) is the number of characters read.
+//
+// Returns false if we encounter an invalid UTF-8 string. Returns true
+// otherwise, including the case when we reach the end of the input (str)
+// before a complete unicode code point is read.
+bool ReadCodePoint(StringPiece str, int index,
+                   uint32 *cp, int* num_left, int *num_read) {
+  if (*num_left == 0) {
+    // Last read was complete. Start reading a new unicode code point.
+    *cp = static_cast<uint8>(str[index++]);
+    *num_read = 1;
+    // The length of the code point is determined from reading the first byte.
+    //
+    // If the first byte is between:
+    //    0..0x7f: that's the value of the code point.
+    // 0x80..0xbf: <invalid>
+    // 0xc0..0xdf: 11-bit code point encoded in 2 bytes.
+    //                                   bit 10-6, bit 5-0
+    // 0xe0..0xef: 16-bit code point encoded in 3 bytes.
+    //                        bit 15-12, bit 11-6, bit 5-0
+    // 0xf0..0xf7: 21-bit code point encoded in 4 bytes.
+    //             bit 20-18, bit 17-12, bit 11-6, bit 5-0
+    // 0xf8..0xff: <invalid>
+    //
+    // Meaning of each bit:
+    // <msb> bit 7: 0 - single byte code point: bits 6-0 are values.
+    //              1 - multibyte code point
+    //       bit 6: 0 - subsequent bytes of multibyte code point:
+    //                  bits 5-0 are values.
+    //              1 - first byte of multibyte code point
+    //       bit 5: 0 - first byte of 2-byte code point: bits 4-0 are values.
+    //              1 - first byte of code point with >= 3 bytes.
+    //       bit 4: 0 - first byte of 3-byte code point: bits 3-0 are values.
+    //              1 - first byte of code point with >= 4 bytes.
+    //       bit 3: 0 - first byte of 4-byte code point: bits 2-0 are values.
+    //              1 - reserved for future expansion.
+    if (*cp <= 0x7f) {
+      return true;
+    } else if (*cp <= 0xbf) {
+      return false;
+    } else if (*cp <= 0xdf) {
+      *cp &= 0x1f;
+      *num_left = 1;
+    } else if (*cp <= 0xef) {
+      *cp &= 0x0f;
+      *num_left = 2;
+    } else if (*cp <= 0xf7) {
+      *cp &= 0x07;
+      *num_left = 3;
+    } else {
+      return false;
+    }
+  } else {
+    // Last read was partial. Initialize num_read to 0 and continue reading
+    // the last unicode code point.
+    *num_read = 0;
+  }
+  while (*num_left > 0 && index < str.size()) {
+    uint32 ch = static_cast<uint8>(str[index++]);
+    --(*num_left);
+    ++(*num_read);
+    *cp = (*cp << 6) | (ch & 0x3f);
+    if (ch < 0x80 || ch > 0xbf) return false;
+  }
+  return *num_left > 0 || (!IsSurrogate(*cp) && IsValidCodePoint(*cp));
+}
+
+// Stores the 16-bit unicode code point as its hexadecimal digits in buffer
+// and returns a StringPiece that points to this buffer. The input buffer needs
+// to be at least 6 bytes long.
+StringPiece ToHex(uint16 cp, char* buffer) {
+  buffer[5] = kHex[cp & 0x0f];
+  cp >>= 4;
+  buffer[4] = kHex[cp & 0x0f];
+  cp >>= 4;
+  buffer[3] = kHex[cp & 0x0f];
+  cp >>= 4;
+  buffer[2] = kHex[cp & 0x0f];
+  return StringPiece(buffer, 0, 6);
+}
+
+// Stores the 32-bit unicode code point as its hexadecimal digits in buffer
+// and returns a StringPiece that points to this buffer. The input buffer needs
+// to be at least 12 bytes long.
+StringPiece ToSurrogateHex(uint32 cp, char* buffer) {
+  uint16 low = ToLowSurrogate(cp);
+  uint16 high = ToHighSurrogate(cp);
+
+  buffer[11] = kHex[low & 0x0f];
+  low >>= 4;
+  buffer[10] = kHex[low & 0x0f];
+  low >>= 4;
+  buffer[9] = kHex[low & 0x0f];
+  low >>= 4;
+  buffer[8] = kHex[low & 0x0f];
+
+  buffer[5] = kHex[high & 0x0f];
+  high >>= 4;
+  buffer[4] = kHex[high & 0x0f];
+  high >>= 4;
+  buffer[3] = kHex[high & 0x0f];
+  high >>= 4;
+  buffer[2] = kHex[high & 0x0f];
+
+  return StringPiece(buffer, 12);
+}
+
+// If the given unicode code point needs escaping, then returns the
+// escaped form. The returned StringPiece either points to statically
+// pre-allocated char[] or to the given buffer. The input buffer needs
+// to be at least 12 bytes long.
+//
+// If the given unicode code point does not need escaping, an empty
+// StringPiece is returned.
+StringPiece EscapeCodePoint(uint32 cp, char* buffer) {
+  if (cp < 0xa0) return kCommonEscapes[cp];
+  switch (cp) {
+    // These are not required by json spec
+    // but used to prevent security bugs in javascript.
+    case 0xfeff:  // Zero width no-break space
+    case 0xfff9:  // Interlinear annotation anchor
+    case 0xfffa:  // Interlinear annotation separator
+    case 0xfffb:  // Interlinear annotation terminator
+
+    case 0x00ad:  // Soft-hyphen
+    case 0x06dd:  // Arabic end of ayah
+    case 0x070f:  // Syriac abbreviation mark
+    case 0x17b4:  // Khmer vowel inherent Aq
+    case 0x17b5:  // Khmer vowel inherent Aa
+      return ToHex(cp, buffer);
+
+    default:
+      if ((cp >= 0x0600 && cp <= 0x0603) ||  // Arabic signs
+          (cp >= 0x200b && cp <= 0x200f) ||  // Zero width etc.
+          (cp >= 0x2028 && cp <= 0x202e) ||  // Separators etc.
+          (cp >= 0x2060 && cp <= 0x2064) ||  // Invisible etc.
+          (cp >= 0x206a && cp <= 0x206f)) {  // Shaping etc.
+        return ToHex(cp, buffer);
+      }
+
+      if (cp == 0x000e0001 ||                        // Language tag
+          (cp >= 0x0001d173 && cp <= 0x0001d17a) ||  // Music formatting
+          (cp >= 0x000e0020 && cp <= 0x000e007f)) {  // TAG symbols
+        return ToSurrogateHex(cp, buffer);
+      }
+  }
+  return StringPiece();
+}
+
+// Tries to escape the given code point first. If the given code point
+// does not need to be escaped, but force_output is true, then render
+// the given multi-byte code point in UTF8 in the buffer and returns it.
+StringPiece EscapeCodePoint(uint32 cp, char* buffer, bool force_output) {
+  StringPiece sp = EscapeCodePoint(cp, buffer);
+  if (force_output && sp.empty()) {
+    buffer[5] = (cp & 0x3f) | 0x80;
+    cp >>= 6;
+    if (cp <= 0x1f) {
+      buffer[4] = cp | 0xc0;
+      sp.set(buffer + 4, 2);
+      return sp;
+    }
+    buffer[4] = (cp & 0x3f) | 0x80;
+    cp >>= 6;
+    if (cp <= 0x0f) {
+      buffer[3] = cp | 0xe0;
+      sp.set(buffer + 3, 3);
+      return sp;
+    }
+    buffer[3] = (cp & 0x3f) | 0x80;
+    buffer[2] = ((cp >> 6) & 0x07) | 0xf0;
+    sp.set(buffer + 2, 4);
+  }
+  return sp;
+}
+
+}  // namespace
+
+void JsonEscaping::Escape(strings::ByteSource* input,
+                          strings::ByteSink* output) {
+  char buffer[12] = "\\udead\\ubee";
+  uint32 cp = 0;     // Current unicode code point.
+  int num_left = 0;  // Num of chars to read to complete the code point.
+  while (input->Available() > 0) {
+    StringPiece str = input->Peek();
+    StringPiece escaped;
+    int i = 0;
+    int num_read;
+    bool ok;
+    bool cp_was_split = num_left > 0;
+    // Loop until we encounter either
+    //   i) a code point that needs to be escaped; or
+    //  ii) a split code point is completely read; or
+    // iii) a character that is not a valid utf8; or
+    //  iv) end of the StringPiece str is reached.
+    do {
+      ok = ReadCodePoint(str, i, &cp, &num_left, &num_read);
+      if (num_left > 0 || !ok) break;  // case iii or iv
+      escaped = EscapeCodePoint(cp, buffer, cp_was_split);
+      if (!escaped.empty()) break;     // case i or ii
+      i += num_read;
+      num_read = 0;
+    } while (i < str.length());        // case iv
+    // First copy the un-escaped prefix, if any, to the output ByteSink.
+    if (i > 0) input->CopyTo(output, i);
+    if (num_read > 0) input->Skip(num_read);
+    if (!ok) {
+      // Case iii: Report error.
+      // TODO(wpoon): Add error reporting.
+      num_left = 0;
+    } else if (num_left == 0 && !escaped.empty()) {
+      // Case i or ii: Append the escaped code point to the output ByteSink.
+      output->Append(escaped.data(), escaped.size());
+    }
+  }
+  if (num_left > 0) {
+    // Treat as case iii: report error.
+    // TODO(wpoon): Add error reporting.
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_escaping.h b/src/google/protobuf/util/internal/json_escaping.h
new file mode 100644
index 0000000..e3e329f
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_escaping.h
@@ -0,0 +1,91 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef NET_PROTO2_UTIL_CONVERTER_STRINGS_JSON_ESCAPING_H_
+#define NET_PROTO2_UTIL_CONVERTER_STRINGS_JSON_ESCAPING_H_
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class JsonEscaping {
+ public:
+  // The minimum value of a unicode high-surrogate code unit in the utf-16
+  // encoding. A high-surrogate is also known as a leading-surrogate.
+  // See http://www.unicode.org/glossary/#high_surrogate_code_unit
+  static const uint16 kMinHighSurrogate = 0xd800;
+
+  // The maximum value of a unicide high-surrogate code unit in the utf-16
+  // encoding. A high-surrogate is also known as a leading-surrogate.
+  // See http://www.unicode.org/glossary/#high_surrogate_code_unit
+  static const uint16 kMaxHighSurrogate = 0xdbff;
+
+  // The minimum value of a unicode low-surrogate code unit in the utf-16
+  // encoding. A low-surrogate is also known as a trailing-surrogate.
+  // See http://www.unicode.org/glossary/#low_surrogate_code_unit
+  static const uint16 kMinLowSurrogate = 0xdc00;
+
+  // The maximum value of a unicode low-surrogate code unit in the utf-16
+  // encoding. A low-surrogate is also known as a trailing surrogate.
+  // See http://www.unicode.org/glossary/#low_surrogate_code_unit
+  static const uint16 kMaxLowSurrogate = 0xdfff;
+
+  // The minimum value of a unicode supplementary code point.
+  // See http://www.unicode.org/glossary/#supplementary_code_point
+  static const uint32 kMinSupplementaryCodePoint = 0x010000;
+
+  // The minimum value of a unicode code point.
+  // See http://www.unicode.org/glossary/#code_point
+  static const uint32 kMinCodePoint = 0x000000;
+
+  // The maximum value of a unicode code point.
+  // See http://www.unicode.org/glossary/#code_point
+  static const uint32 kMaxCodePoint = 0x10ffff;
+
+  JsonEscaping() {}
+  virtual ~JsonEscaping() {}
+
+  // Escape the given ByteSource to the given ByteSink.
+  static void Escape(strings::ByteSource* input, strings::ByteSink* output);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(JsonEscaping);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+#endif  // NET_PROTO2_UTIL_CONVERTER_STRINGS_JSON_ESCAPING_H_
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_objectwriter.cc b/src/google/protobuf/util/internal/json_objectwriter.cc
new file mode 100644
index 0000000..94d2ab7
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_objectwriter.cc
@@ -0,0 +1,181 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_objectwriter.h>
+
+#include <math.h>
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/util/internal/json_escaping.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/mathlimits.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using strings::ArrayByteSource;
+
+JsonObjectWriter::~JsonObjectWriter() {
+  if (!element_->is_root()) {
+    GOOGLE_LOG(WARNING) << "JsonObjectWriter was not fully closed.";
+  }
+}
+
+JsonObjectWriter* JsonObjectWriter::StartObject(StringPiece name) {
+  WritePrefix(name);
+  WriteChar('{');
+  Push();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::EndObject() {
+  Pop();
+  WriteChar('}');
+  if (element()->is_root()) NewLine();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::StartList(StringPiece name) {
+  WritePrefix(name);
+  WriteChar('[');
+  Push();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::EndList() {
+  Pop();
+  WriteChar(']');
+  if (element()->is_root()) NewLine();
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderBool(StringPiece name,
+                                               bool value) {
+  return RenderSimple(name, value ? "true" : "false");
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderInt32(StringPiece name,
+                                                int32 value) {
+  return RenderSimple(name, SimpleItoa(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderUint32(StringPiece name,
+                                                 uint32 value) {
+  return RenderSimple(name, SimpleItoa(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderInt64(StringPiece name,
+                                                int64 value) {
+  WritePrefix(name);
+  WriteChar('"');
+  stream_->WriteString(SimpleItoa(value));
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderUint64(StringPiece name,
+                                                 uint64 value) {
+  WritePrefix(name);
+  WriteChar('"');
+  stream_->WriteString(SimpleItoa(value));
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderDouble(StringPiece name,
+                                                 double value) {
+  if (MathLimits<double>::IsFinite(value)) {
+    return RenderSimple(name, SimpleDtoa(value));
+  }
+
+  // Render quoted with NaN/Infinity-aware DoubleAsString.
+  return RenderString(name, DoubleAsString(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderFloat(StringPiece name,
+                                                float value) {
+  if (MathLimits<float>::IsFinite(value)) {
+    return RenderSimple(name, SimpleFtoa(value));
+  }
+
+  // Render quoted with NaN/Infinity-aware FloatAsString.
+  return RenderString(name, FloatAsString(value));
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderString(StringPiece name,
+                                                 StringPiece value) {
+  WritePrefix(name);
+  WriteChar('"');
+  ArrayByteSource source(value);
+  JsonEscaping::Escape(&source, &sink_);
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderBytes(StringPiece name,
+                                                StringPiece value) {
+  WritePrefix(name);
+  string base64;
+  Base64Escape(value, &base64);
+  WriteChar('"');
+  // TODO(wpoon): Consider a ByteSink solution that writes the base64 bytes
+  //              directly to the stream, rather than first putting them
+  //              into a string and then writing them to the stream.
+  stream_->WriteRaw(base64.data(), base64.size());
+  WriteChar('"');
+  return this;
+}
+
+JsonObjectWriter* JsonObjectWriter::RenderNull(StringPiece name) {
+  return RenderSimple(name, "null");
+}
+
+void JsonObjectWriter::WritePrefix(StringPiece name) {
+  bool not_first = !element()->is_first();
+  if (not_first) WriteChar(',');
+  if (not_first || !element()->is_root()) NewLine();
+  if (!name.empty()) {
+    WriteChar('"');
+    ArrayByteSource source(name);
+    JsonEscaping::Escape(&source, &sink_);
+    stream_->WriteString("\":");
+    if (!indent_string_.empty()) WriteChar(' ');
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_objectwriter.h b/src/google/protobuf/util/internal/json_objectwriter.h
new file mode 100644
index 0000000..761a0a1
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_objectwriter.h
@@ -0,0 +1,206 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_OBJECTWRITER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/util/internal/structured_objectwriter.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An ObjectWriter implementation that outputs JSON. This ObjectWriter
+// supports writing a compact form or a pretty printed form.
+//
+// Sample usage:
+//   string output;
+//   StringOutputStream* str_stream = new StringOutputStream(&output);
+//   CodedOutputStream* out_stream = new CodedOutputStream(str_stream);
+//   JsonObjectWriter* ow = new JsonObjectWriter("  ", out_stream);
+//   ow->StartObject("")
+//       ->RenderString("name", "value")
+//       ->RenderString("emptystring", string())
+//       ->StartObject("nested")
+//         ->RenderInt64("light", 299792458);
+//         ->RenderDouble("pi", 3.141592653589793);
+//       ->EndObject()
+//       ->StartList("empty")
+//       ->EndList()
+//     ->EndObject();
+//
+// And then the output string would become:
+// {
+//   "name": "value",
+//   "emptystring": "",
+//   "nested": {
+//     "light": "299792458",
+//     "pi": 3.141592653589793
+//   },
+//   "empty": []
+// }
+//
+// JsonObjectWriter does not validate if calls actually result in valid JSON.
+// For example, passing an empty name when one would be required won't result
+// in an error, just an invalid output.
+//
+// Note that all int64 and uint64 are rendered as strings instead of numbers.
+// This is because JavaScript parses numbers as 64-bit float thus int64 and
+// uint64 would lose precision if rendered as numbers.
+//
+// JsonObjectWriter is thread-unsafe.
+class LIBPROTOBUF_EXPORT JsonObjectWriter : public StructuredObjectWriter {
+ public:
+  JsonObjectWriter(StringPiece indent_string,
+                   google::protobuf::io::CodedOutputStream* out)
+      : element_(new Element(NULL)),
+        stream_(out), sink_(out),
+        indent_string_(indent_string.ToString()) {
+  }
+  virtual ~JsonObjectWriter();
+
+  // ObjectWriter methods.
+  virtual JsonObjectWriter* StartObject(StringPiece name);
+  virtual JsonObjectWriter* EndObject();
+  virtual JsonObjectWriter* StartList(StringPiece name);
+  virtual JsonObjectWriter* EndList();
+  virtual JsonObjectWriter* RenderBool(StringPiece name, bool value);
+  virtual JsonObjectWriter* RenderInt32(StringPiece name, int32 value);
+  virtual JsonObjectWriter* RenderUint32(StringPiece name, uint32 value);
+  virtual JsonObjectWriter* RenderInt64(StringPiece name, int64 value);
+  virtual JsonObjectWriter* RenderUint64(StringPiece name, uint64 value);
+  virtual JsonObjectWriter* RenderDouble(StringPiece name, double value);
+  virtual JsonObjectWriter* RenderFloat(StringPiece name, float value);
+  virtual JsonObjectWriter* RenderString(StringPiece name, StringPiece value);
+  virtual JsonObjectWriter* RenderBytes(StringPiece name, StringPiece value);
+  virtual JsonObjectWriter* RenderNull(StringPiece name);
+
+ protected:
+  class LIBPROTOBUF_EXPORT Element : public BaseElement {
+   public:
+    explicit Element(Element* parent) : BaseElement(parent), is_first_(true) {}
+
+    // Called before each field of the Element is to be processed.
+    // Returns true if this is the first call (processing the first field).
+    bool is_first() {
+      if (is_first_) {
+        is_first_ = false;
+        return true;
+      }
+      return false;
+    }
+
+   private:
+    bool is_first_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(Element);
+  };
+
+  virtual Element* element() { return element_.get(); }
+
+ private:
+  class LIBPROTOBUF_EXPORT ByteSinkWrapper : public strings::ByteSink {
+   public:
+    explicit ByteSinkWrapper(google::protobuf::io::CodedOutputStream* stream)
+        : stream_(stream) {}
+    virtual ~ByteSinkWrapper() {}
+
+    // ByteSink methods.
+    virtual void Append(const char* bytes, size_t n) {
+      stream_->WriteRaw(bytes, n);
+    }
+
+   private:
+    google::protobuf::io::CodedOutputStream* stream_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ByteSinkWrapper);
+  };
+
+  // Renders a simple value as a string. By default all non-string Render
+  // methods convert their argument to a string and call this method. This
+  // method can then be used to render the simple value without escaping it.
+  JsonObjectWriter* RenderSimple(StringPiece name, const string& value) {
+    WritePrefix(name);
+    stream_->WriteString(value);
+    return this;
+  }
+
+  // Pushes a new element to the stack.
+  void Push() { element_.reset(new Element(element_.release())); }
+
+  // Pops an element off of the stack and deletes the popped element.
+  void Pop() {
+    bool needs_newline = !element_->is_first();
+    element_.reset(element_->pop<Element>());
+    if (needs_newline) NewLine();
+  }
+
+  // If pretty printing is enabled, this will write a newline to the output,
+  // followed by optional indentation. Otherwise this method is a noop.
+  void NewLine() {
+    if (!indent_string_.empty()) {
+      WriteChar('\n');
+      for (int i = 0; i < element()->level(); i++) {
+        stream_->WriteString(indent_string_);
+      }
+    }
+  }
+
+  // Writes a prefix. This will write out any pretty printing and
+  // commas that are required, followed by the name and a ':' if
+  // the name is not null.
+  void WritePrefix(StringPiece name);
+
+  // Writes an individual character to the output.
+  void WriteChar(const char c) { stream_->WriteRaw(&c, sizeof(c)); }
+
+  google::protobuf::scoped_ptr<Element> element_;
+  google::protobuf::io::CodedOutputStream* stream_;
+  ByteSinkWrapper sink_;
+  const string indent_string_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(JsonObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/json_objectwriter_test.cc b/src/google/protobuf/util/internal/json_objectwriter_test.cc
new file mode 100644
index 0000000..9d82016
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_objectwriter_test.cc
@@ -0,0 +1,289 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_objectwriter.h>
+
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::io::CodedOutputStream;
+using google::protobuf::io::StringOutputStream;
+
+class JsonObjectWriterTest : public ::testing::Test {
+ protected:
+  JsonObjectWriterTest()
+      : str_stream_(new StringOutputStream(&output_)),
+        out_stream_(new CodedOutputStream(str_stream_)),
+        ow_(NULL) {}
+
+  virtual ~JsonObjectWriterTest() {
+    delete ow_;
+    delete out_stream_;
+    delete str_stream_;
+  }
+
+  string output_;
+  StringOutputStream* const str_stream_;
+  CodedOutputStream* const out_stream_;
+  ObjectWriter* ow_;
+};
+
+TEST_F(JsonObjectWriterTest, EmptyRootObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")->EndObject();
+  EXPECT_EQ("{}", output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, EmptyObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderString("test", "value")
+      ->StartObject("empty")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ("{\"test\":\"value\",\"empty\":{}}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, EmptyRootList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartList("")->EndList();
+  EXPECT_EQ("[]", output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, EmptyList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderString("test", "value")
+      ->StartList("empty")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ("{\"test\":\"value\",\"empty\":[]}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ObjectInObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->StartObject("nested")
+      ->RenderString("field", "value")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ("{\"nested\":{\"field\":\"value\"}}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ListInObject) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->StartList("nested")
+      ->RenderString("", "value")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ("{\"nested\":[\"value\"]}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ObjectInList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartList("")
+      ->StartObject("")
+      ->RenderString("field", "value")
+      ->EndObject()
+      ->EndList();
+  EXPECT_EQ("[{\"field\":\"value\"}]",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, ListInList) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartList("")
+      ->StartList("")
+      ->RenderString("", "value")
+      ->EndList()
+      ->EndList();
+  EXPECT_EQ("[[\"value\"]]", output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, RenderPrimitives) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderBool("bool", true)
+      ->RenderDouble("double", std::numeric_limits<double>::max())
+      ->RenderFloat("float", std::numeric_limits<float>::max())
+      ->RenderInt32("int", std::numeric_limits<int32>::min())
+      ->RenderInt64("long", std::numeric_limits<int64>::min())
+      ->RenderBytes("bytes", "abracadabra")
+      ->RenderString("string", "string")
+      ->RenderBytes("emptybytes", "")
+      ->RenderString("emptystring", string())
+      ->EndObject();
+  EXPECT_EQ(
+      "{\"bool\":true,"
+      "\"double\":" +
+          ValueAsString<double>(std::numeric_limits<double>::max()) +
+          ","
+          "\"float\":" +
+          ValueAsString<float>(std::numeric_limits<float>::max()) +
+          ","
+          "\"int\":-2147483648,"
+          "\"long\":\"-9223372036854775808\","
+          "\"bytes\":\"YWJyYWNhZGFicmE=\","
+          "\"string\":\"string\","
+          "\"emptybytes\":\"\","
+          "\"emptystring\":\"\"}",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, BytesEncodesAsNonWebSafeBase64) {
+  string s;
+  s.push_back('\377');
+  s.push_back('\357');
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")->RenderBytes("bytes", s)->EndObject();
+  // Non-web-safe would encode this as "/+8="
+  EXPECT_EQ("{\"bytes\":\"/+8=\"}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintList) {
+  ow_ = new JsonObjectWriter(" ", out_stream_);
+  ow_->StartObject("")
+      ->StartList("items")
+      ->RenderString("", "item1")
+      ->RenderString("", "item2")
+      ->RenderString("", "item3")
+      ->EndList()
+      ->StartList("empty")
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"items\": [\n"
+      "  \"item1\",\n"
+      "  \"item2\",\n"
+      "  \"item3\"\n"
+      " ],\n"
+      " \"empty\": []\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintObject) {
+  ow_ = new JsonObjectWriter(" ", out_stream_);
+  ow_->StartObject("")
+      ->StartObject("items")
+      ->RenderString("key1", "item1")
+      ->RenderString("key2", "item2")
+      ->RenderString("key3", "item3")
+      ->EndObject()
+      ->StartObject("empty")
+      ->EndObject()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"items\": {\n"
+      "  \"key1\": \"item1\",\n"
+      "  \"key2\": \"item2\",\n"
+      "  \"key3\": \"item3\"\n"
+      " },\n"
+      " \"empty\": {}\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintEmptyObjectInEmptyList) {
+  ow_ = new JsonObjectWriter(" ", out_stream_);
+  ow_->StartObject("")
+      ->StartList("list")
+      ->StartObject("")
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      " \"list\": [\n"
+      "  {}\n"
+      " ]\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, PrettyPrintDoubleIndent) {
+  ow_ = new JsonObjectWriter("  ", out_stream_);
+  ow_->StartObject("")
+      ->RenderBool("bool", true)
+      ->RenderInt32("int", 42)
+      ->EndObject();
+  EXPECT_EQ(
+      "{\n"
+      "  \"bool\": true,\n"
+      "  \"int\": 42\n"
+      "}\n",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, StringsEscapedAndEnclosedInDoubleQuotes) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")->RenderString("string", "'<>&amp;\\\"\r\n")->EndObject();
+  EXPECT_EQ("{\"string\":\"'\\u003c\\u003e&amp;\\\\\\\"\\r\\n\"}",
+            output_.substr(0, out_stream_->ByteCount()));
+}
+
+TEST_F(JsonObjectWriterTest, Stringification) {
+  ow_ = new JsonObjectWriter("", out_stream_);
+  ow_->StartObject("")
+      ->RenderDouble("double_nan", std::numeric_limits<double>::quiet_NaN())
+      ->RenderFloat("float_nan", std::numeric_limits<float>::quiet_NaN())
+      ->RenderDouble("double_pos", std::numeric_limits<double>::infinity())
+      ->RenderFloat("float_pos", std::numeric_limits<float>::infinity())
+      ->RenderDouble("double_neg", -std::numeric_limits<double>::infinity())
+      ->RenderFloat("float_neg", -std::numeric_limits<float>::infinity())
+      ->EndObject();
+  EXPECT_EQ(
+      "{\"double_nan\":\"NaN\","
+      "\"float_nan\":\"NaN\","
+      "\"double_pos\":\"Infinity\","
+      "\"float_pos\":\"Infinity\","
+      "\"double_neg\":\"-Infinity\","
+      "\"float_neg\":\"-Infinity\"}",
+      output_.substr(0, out_stream_->ByteCount()));
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_stream_parser.cc b/src/google/protobuf/util/internal/json_stream_parser.cc
new file mode 100644
index 0000000..df91675
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_stream_parser.cc
@@ -0,0 +1,774 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_stream_parser.h>
+
+#include <algorithm>
+#include <cctype>
+#include <cerrno>
+#include <cstdlib>
+#include <cstring>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/util/internal/object_writer.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+// Allow these symbols to be referenced as util::Status, util::error::* in
+// this file.
+using util::Status;
+namespace error {
+using util::error::INTERNAL;
+using util::error::INVALID_ARGUMENT;
+}  // namespace error
+
+namespace converter {
+
+// Number of digits in a unicode escape sequence (/uXXXX)
+static const int kUnicodeEscapedLength = 6;
+
+// Length of the true, false, and null literals.
+static const int true_len = strlen("true");
+static const int false_len = strlen("false");
+static const int null_len = strlen("null");
+
+inline bool IsLetter(char c) {
+  return ('a' <= c && c <= 'z') || ('A' <= c && c <= 'Z') || (c == '_') ||
+         (c == '$');
+}
+
+inline bool IsAlphanumeric(char c) {
+  return IsLetter(c) || ('0' <= c && c <= '9');
+}
+
+static bool ConsumeKey(StringPiece* input, StringPiece* key) {
+  if (input->empty() || !IsLetter((*input)[0])) return false;
+  int len = 1;
+  for (; len < input->size(); ++len) {
+    if (!IsAlphanumeric((*input)[len])) {
+      break;
+    }
+  }
+  *key = StringPiece(input->data(), len);
+  *input = StringPiece(input->data() + len, input->size() - len);
+  return true;
+}
+
+static bool MatchKey(StringPiece input) {
+  return !input.empty() && IsLetter(input[0]);
+}
+
+JsonStreamParser::JsonStreamParser(ObjectWriter* ow)
+    : ow_(ow),
+      stack_(),
+      leftover_(),
+      json_(),
+      p_(),
+      key_(),
+      key_storage_(),
+      finishing_(false),
+      parsed_(),
+      parsed_storage_(),
+      string_open_(0),
+      chunk_storage_(),
+      coerce_to_utf8_(false) {
+  // Initialize the stack with a single value to be parsed.
+  stack_.push(VALUE);
+}
+
+JsonStreamParser::~JsonStreamParser() {}
+
+
+util::Status JsonStreamParser::Parse(StringPiece json) {
+  StringPiece chunk = json;
+  // If we have leftovers from a previous chunk, append the new chunk to it
+  // and create a new StringPiece pointing at the string's data. This could
+  // be large but we rely on the chunks to be small, assuming they are
+  // fragments of a Cord.
+  if (!leftover_.empty()) {
+    // Don't point chunk to leftover_ because leftover_ will be updated in
+    // ParseChunk(chunk).
+    chunk_storage_.swap(leftover_);
+    json.AppendToString(&chunk_storage_);
+    chunk = StringPiece(chunk_storage_);
+  }
+
+  // Find the structurally valid UTF8 prefix and parse only that.
+  int n = internal::UTF8SpnStructurallyValid(chunk);
+  if (n > 0) {
+    util::Status status = ParseChunk(chunk.substr(0, n));
+
+    // Any leftover characters are stashed in leftover_ for later parsing when
+    // there is more data available.
+    chunk.substr(n).AppendToString(&leftover_);
+    return status;
+  } else {
+    chunk.CopyToString(&leftover_);
+    return util::Status::OK;
+  }
+}
+
+util::Status JsonStreamParser::FinishParse() {
+  // If we do not expect anything and there is nothing left to parse we're all
+  // done.
+  if (stack_.empty() && leftover_.empty()) {
+    return util::Status::OK;
+  }
+
+  // Storage for UTF8-coerced string.
+  google::protobuf::scoped_array<char> utf8;
+  if (coerce_to_utf8_) {
+    utf8.reset(new char[leftover_.size()]);
+    char* coerced = internal::UTF8CoerceToStructurallyValid(leftover_, utf8.get(), ' ');
+    p_ = json_ = StringPiece(coerced, leftover_.size());
+  } else {
+    p_ = json_ = leftover_;
+    if (!internal::IsStructurallyValidUTF8(leftover_)) {
+      return ReportFailure("Encountered non UTF-8 code points.");
+    }
+  }
+
+  // Parse the remainder in finishing mode, which reports errors for things like
+  // unterminated strings or unknown tokens that would normally be retried.
+  finishing_ = true;
+  util::Status result = RunParser();
+  if (result.ok()) {
+    SkipWhitespace();
+    if (!p_.empty()) {
+      result = ReportFailure("Parsing terminated before end of input.");
+    }
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseChunk(StringPiece chunk) {
+  // Do not do any work if the chunk is empty.
+  if (chunk.empty()) return util::Status::OK;
+
+  p_ = json_ = chunk;
+
+  finishing_ = false;
+  util::Status result = RunParser();
+  if (!result.ok()) return result;
+
+  SkipWhitespace();
+  if (p_.empty()) {
+    // If we parsed everything we had, clear the leftover.
+    leftover_.clear();
+  } else {
+    // If we do not expect anything i.e. stack is empty, and we have non-empty
+    // string left to parse, we report an error.
+    if (stack_.empty()) {
+      return ReportFailure("Parsing terminated before end of input.");
+    }
+    // If we expect future data i.e. stack is non-empty, and we have some
+    // unparsed data left, we save it for later parse.
+    leftover_ = p_.ToString();
+  }
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::RunParser() {
+  while (!stack_.empty()) {
+    ParseType type = stack_.top();
+    TokenType t = (string_open_ == 0) ? GetNextTokenType() : BEGIN_STRING;
+    stack_.pop();
+    util::Status result;
+    switch (type) {
+      case VALUE:
+        result = ParseValue(t);
+        break;
+
+      case OBJ_MID:
+        result = ParseObjectMid(t);
+        break;
+
+      case ENTRY:
+        result = ParseEntry(t);
+        break;
+
+      case ENTRY_MID:
+        result = ParseEntryMid(t);
+        break;
+
+      case ARRAY_VALUE:
+        result = ParseArrayValue(t);
+        break;
+
+      case ARRAY_MID:
+        result = ParseArrayMid(t);
+        break;
+
+      default:
+        result = util::Status(util::error::INTERNAL,
+                              StrCat("Unknown parse type: ", type));
+        break;
+    }
+    if (!result.ok()) {
+      // If we were cancelled, save our state and try again later.
+      if (!finishing_ && result == util::Status::CANCELLED) {
+        stack_.push(type);
+        // If we have a key we still need to render, make sure to save off the
+        // contents in our own storage.
+        if (!key_.empty() && key_storage_.empty()) {
+          key_.AppendToString(&key_storage_);
+          key_ = StringPiece(key_storage_);
+        }
+        result = util::Status::OK;
+      }
+      return result;
+    }
+  }
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseValue(TokenType type) {
+  switch (type) {
+    case BEGIN_OBJECT:
+      return HandleBeginObject();
+    case BEGIN_ARRAY:
+      return HandleBeginArray();
+    case BEGIN_STRING:
+      return ParseString();
+    case BEGIN_NUMBER:
+      return ParseNumber();
+    case BEGIN_TRUE:
+      return ParseTrue();
+    case BEGIN_FALSE:
+      return ParseFalse();
+    case BEGIN_NULL:
+      return ParseNull();
+    case UNKNOWN:
+      return ReportUnknown("Expected a value.");
+    default: {
+      // Special case for having been cut off while parsing, wait for more data.
+      // This handles things like 'fals' being at the end of the string, we
+      // don't know if the next char would be e, completing it, or something
+      // else, making it invalid.
+      if (!finishing_ && p_.length() < false_len) {
+        return util::Status::CANCELLED;
+      }
+      return ReportFailure("Unexpected token.");
+    }
+  }
+}
+
+util::Status JsonStreamParser::ParseString() {
+  util::Status result = ParseStringHelper();
+  if (result.ok()) {
+    ow_->RenderString(key_, parsed_);
+    key_.clear();
+    parsed_.clear();
+    parsed_storage_.clear();
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseStringHelper() {
+  // If we haven't seen the start quote, grab it and remember it for later.
+  if (string_open_ == 0) {
+    string_open_ = *p_.data();
+    GOOGLE_DCHECK(string_open_ == '\"' || string_open_ == '\'');
+    Advance();
+  }
+  // Track where we last copied data from so we can minimize copying.
+  const char* last = p_.data();
+  while (!p_.empty()) {
+    const char* data = p_.data();
+    if (*data == '\\') {
+      // We're about to handle an escape, copy all bytes from last to data.
+      if (last < data) {
+        parsed_storage_.append(last, data - last);
+        last = data;
+      }
+      // If we ran out of string after the \, cancel or report an error
+      // depending on if we expect more data later.
+      if (p_.length() == 1) {
+        if (!finishing_) {
+          return util::Status::CANCELLED;
+        }
+        return ReportFailure("Closing quote expected in string.");
+      }
+      // Parse a unicode escape if we found \u in the string.
+      if (data[1] == 'u') {
+        util::Status result = ParseUnicodeEscape();
+        if (!result.ok()) {
+          return result;
+        }
+        // Move last pointer past the unicode escape and continue.
+        last = p_.data();
+        continue;
+      }
+      // Handle the standard set of backslash-escaped characters.
+      switch (data[1]) {
+        case 'b':
+          parsed_storage_.push_back('\b');
+          break;
+        case 'f':
+          parsed_storage_.push_back('\f');
+          break;
+        case 'n':
+          parsed_storage_.push_back('\n');
+          break;
+        case 'r':
+          parsed_storage_.push_back('\r');
+          break;
+        case 't':
+          parsed_storage_.push_back('\t');
+          break;
+        case 'v':
+          parsed_storage_.push_back('\v');
+          break;
+        default:
+          parsed_storage_.push_back(data[1]);
+      }
+      // We handled two characters, so advance past them and continue.
+      p_.remove_prefix(2);
+      last = p_.data();
+      continue;
+    }
+    // If we found the closing quote note it, advance past it, and return.
+    if (*data == string_open_) {
+      // If we didn't copy anything, reuse the input buffer.
+      if (parsed_storage_.empty()) {
+        parsed_ = StringPiece(last, data - last);
+      } else {
+        if (last < data) {
+          parsed_storage_.append(last, data - last);
+          last = data;
+        }
+        parsed_ = StringPiece(parsed_storage_);
+      }
+      // Clear the quote char so next time we try to parse a string we'll
+      // start fresh.
+      string_open_ = 0;
+      Advance();
+      return util::Status::OK;
+    }
+    // Normal character, just advance past it.
+    Advance();
+  }
+  // If we ran out of characters, copy over what we have so far.
+  if (last < p_.data()) {
+    parsed_storage_.append(last, p_.data() - last);
+  }
+  // If we didn't find the closing quote but we expect more data, cancel for now
+  if (!finishing_) {
+    return util::Status::CANCELLED;
+  }
+  // End of string reached without a closing quote, report an error.
+  string_open_ = 0;
+  return ReportFailure("Closing quote expected in string.");
+}
+
+// Converts a unicode escaped character to a decimal value stored in a char32
+// for use in UTF8 encoding utility.  We assume that str begins with \uhhhh and
+// convert that from the hex number to a decimal value.
+//
+// There are some security exploits with UTF-8 that we should be careful of:
+//   - http://www.unicode.org/reports/tr36/#UTF-8_Exploit
+//   - http://sites/intl-eng/design-guide/core-application
+util::Status JsonStreamParser::ParseUnicodeEscape() {
+  if (p_.length() < kUnicodeEscapedLength) {
+    if (!finishing_) {
+      return util::Status::CANCELLED;
+    }
+    return ReportFailure("Illegal hex string.");
+  }
+  GOOGLE_DCHECK_EQ('\\', p_.data()[0]);
+  GOOGLE_DCHECK_EQ('u', p_.data()[1]);
+  uint32 code = 0;
+  for (int i = 2; i < kUnicodeEscapedLength; ++i) {
+    if (!isxdigit(p_.data()[i])) {
+      return ReportFailure("Invalid escape sequence.");
+    }
+    code = (code << 4) + hex_digit_to_int(p_.data()[i]);
+  }
+  char buf[UTFmax];
+  int len = EncodeAsUTF8Char(code, buf);
+  // Advance past the unicode escape.
+  p_.remove_prefix(kUnicodeEscapedLength);
+  parsed_storage_.append(buf, len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseNumber() {
+  NumberResult number;
+  util::Status result = ParseNumberHelper(&number);
+  if (result.ok()) {
+    switch (number.type) {
+      case NumberResult::DOUBLE:
+        ow_->RenderDouble(key_, number.double_val);
+        key_.clear();
+        break;
+
+      case NumberResult::INT:
+        ow_->RenderInt64(key_, number.int_val);
+        key_.clear();
+        break;
+
+      case NumberResult::UINT:
+        ow_->RenderUint64(key_, number.uint_val);
+        key_.clear();
+        break;
+
+      default:
+        return ReportFailure("Unable to parse number.");
+    }
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseNumberHelper(NumberResult* result) {
+  const char* data = p_.data();
+  int length = p_.length();
+
+  // Look for the first non-numeric character, or the end of the string.
+  int index = 0;
+  bool floating = false;
+  bool negative = data[index] == '-';
+  // Find the first character that cannot be part of the number. Along the way
+  // detect if the number needs to be parsed as a double.
+  // Note that this restricts numbers to the JSON specification, so for example
+  // we do not support hex or octal notations.
+  for (; index < length; ++index) {
+    char c = data[index];
+    if (isdigit(c)) continue;
+    if (c == '.' || c == 'e' || c == 'E') {
+      floating = true;
+      continue;
+    }
+    if (c == '+' || c == '-') continue;
+    // Not a valid number character, break out.
+    break;
+  }
+
+  // If the entire input is a valid number, and we may have more content in the
+  // future, we abort for now and resume when we know more.
+  if (index == length && !finishing_) {
+    return util::Status::CANCELLED;
+  }
+
+  // Create a string containing just the number, so we can use safe_strtoX
+  string number = p_.substr(0, index).ToString();
+
+  // Floating point number, parse as a double.
+  if (floating) {
+    if (!safe_strtod(number, &result->double_val)) {
+      return ReportFailure("Unable to parse number.");
+    }
+    result->type = NumberResult::DOUBLE;
+    p_.remove_prefix(index);
+    return util::Status::OK;
+  }
+
+  // Positive non-floating point number, parse as a uint64.
+  if (!negative) {
+    if (!safe_strtou64(number, &result->uint_val)) {
+      return ReportFailure("Unable to parse number.");
+    }
+    result->type = NumberResult::UINT;
+    p_.remove_prefix(index);
+    return util::Status::OK;
+  }
+
+  // Negative non-floating point number, parse as an int64.
+  if (!safe_strto64(number, &result->int_val)) {
+    return ReportFailure("Unable to parse number.");
+  }
+  result->type = NumberResult::INT;
+  p_.remove_prefix(index);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::HandleBeginObject() {
+  GOOGLE_DCHECK_EQ('{', *p_.data());
+  Advance();
+  ow_->StartObject(key_);
+  key_.clear();
+  stack_.push(ENTRY);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseObjectMid(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected , or } after key:value pair.");
+  }
+
+  // Object is complete, advance past the comma and render the EndObject.
+  if (type == END_OBJECT) {
+    Advance();
+    ow_->EndObject();
+    return util::Status::OK;
+  }
+  // Found a comma, advance past it and get ready for an entry.
+  if (type == VALUE_SEPARATOR) {
+    Advance();
+    stack_.push(ENTRY);
+    return util::Status::OK;
+  }
+  // Illegal token after key:value pair.
+  return ReportFailure("Expected , or } after key:value pair.");
+}
+
+util::Status JsonStreamParser::ParseEntry(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected an object key or }.");
+  }
+
+  // Close the object and return. This allows for trailing commas.
+  if (type == END_OBJECT) {
+    ow_->EndObject();
+    Advance();
+    return util::Status::OK;
+  }
+
+  util::Status result;
+  if (type == BEGIN_STRING) {
+    // Key is a string (standard JSON), parse it and store the string.
+    result = ParseStringHelper();
+    if (result.ok()) {
+      key_storage_.clear();
+      if (!parsed_storage_.empty()) {
+        parsed_storage_.swap(key_storage_);
+        key_ = StringPiece(key_storage_);
+      } else {
+        key_ = parsed_;
+      }
+      parsed_.clear();
+    }
+  } else if (type == BEGIN_KEY) {
+    // Key is a bare key (back compat), create a StringPiece pointing to it.
+    result = ParseKey();
+  } else {
+    // Unknown key type, report an error.
+    result = ReportFailure("Expected an object key or }.");
+  }
+  // On success we next expect an entry mid ':' then an object mid ',' or '}'
+  if (result.ok()) {
+    stack_.push(OBJ_MID);
+    stack_.push(ENTRY_MID);
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseEntryMid(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected : between key:value pair.");
+  }
+  if (type == ENTRY_SEPARATOR) {
+    Advance();
+    stack_.push(VALUE);
+    return util::Status::OK;
+  }
+  return ReportFailure("Expected : between key:value pair.");
+}
+
+util::Status JsonStreamParser::HandleBeginArray() {
+  GOOGLE_DCHECK_EQ('[', *p_.data());
+  Advance();
+  ow_->StartList(key_);
+  key_.clear();
+  stack_.push(ARRAY_VALUE);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseArrayValue(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected a value or ] within an array.");
+  }
+
+  if (type == END_ARRAY) {
+    ow_->EndList();
+    Advance();
+    return util::Status::OK;
+  }
+
+  // The ParseValue call may push something onto the stack so we need to make
+  // sure an ARRAY_MID is after it, so we push it on now.
+  stack_.push(ARRAY_MID);
+  util::Status result = ParseValue(type);
+  if (result == util::Status::CANCELLED) {
+    // If we were cancelled, pop back off the ARRAY_MID so we don't try to
+    // push it on again when we try over.
+    stack_.pop();
+  }
+  return result;
+}
+
+util::Status JsonStreamParser::ParseArrayMid(TokenType type) {
+  if (type == UNKNOWN) {
+    return ReportUnknown("Expected , or ] after array value.");
+  }
+
+  if (type == END_ARRAY) {
+    ow_->EndList();
+    Advance();
+    return util::Status::OK;
+  }
+
+  // Found a comma, advance past it and expect an array value next.
+  if (type == VALUE_SEPARATOR) {
+    Advance();
+    stack_.push(ARRAY_VALUE);
+    return util::Status::OK;
+  }
+  // Illegal token after array value.
+  return ReportFailure("Expected , or ] after array value.");
+}
+
+util::Status JsonStreamParser::ParseTrue() {
+  ow_->RenderBool(key_, true);
+  key_.clear();
+  p_.remove_prefix(true_len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseFalse() {
+  ow_->RenderBool(key_, false);
+  key_.clear();
+  p_.remove_prefix(false_len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ParseNull() {
+  ow_->RenderNull(key_);
+  key_.clear();
+  p_.remove_prefix(null_len);
+  return util::Status::OK;
+}
+
+util::Status JsonStreamParser::ReportFailure(StringPiece message) {
+  static const int kContextLength = 20;
+  const char* p_start = p_.data();
+  const char* json_start = json_.data();
+  const char* begin = max(p_start - kContextLength, json_start);
+  const char* end = min(p_start + kContextLength, json_start + json_.size());
+  StringPiece segment(begin, end - begin);
+  string location(p_start - begin, ' ');
+  location.push_back('^');
+  return util::Status(util::error::INVALID_ARGUMENT,
+                      StrCat(message, "\n", segment, "\n", location));
+}
+
+util::Status JsonStreamParser::ReportUnknown(StringPiece message) {
+  // If we aren't finishing the parse, cancel parsing and try later.
+  if (!finishing_) {
+    return util::Status::CANCELLED;
+  }
+  if (p_.empty()) {
+    return ReportFailure(StrCat("Unexpected end of string. ", message));
+  }
+  return ReportFailure(message);
+}
+
+void JsonStreamParser::SkipWhitespace() {
+  while (!p_.empty() && ascii_isspace(*p_.data())) {
+    Advance();
+  }
+}
+
+void JsonStreamParser::Advance() {
+  // Advance by moving one UTF8 character while making sure we don't go beyond
+  // the length of StringPiece.
+  p_.remove_prefix(
+      min<int>(p_.length(), UTF8FirstLetterNumBytes(p_.data(), p_.length())));
+}
+
+util::Status JsonStreamParser::ParseKey() {
+  StringPiece original = p_;
+  if (!ConsumeKey(&p_, &key_)) {
+    return ReportFailure("Invalid key or variable name.");
+  }
+  // If we consumed everything but expect more data, reset p_ and cancel since
+  // we can't know if the key was complete or not.
+  if (!finishing_ && p_.empty()) {
+    p_ = original;
+    return util::Status::CANCELLED;
+  }
+  // Since we aren't using the key storage, clear it out.
+  key_storage_.clear();
+  return util::Status::OK;
+}
+
+JsonStreamParser::TokenType JsonStreamParser::GetNextTokenType() {
+  SkipWhitespace();
+
+  int size = p_.size();
+  if (size == 0) {
+    // If we ran out of data, report unknown and we'll place the previous parse
+    // type onto the stack and try again when we have more data.
+    return UNKNOWN;
+  }
+  // TODO(sven): Split this method based on context since different contexts
+  // support different tokens. Would slightly speed up processing?
+  const char* data = p_.data();
+  if (*data == '\"' || *data == '\'') return BEGIN_STRING;
+  if (*data == '-' || ('0' <= *data && *data <= '9')) {
+    return BEGIN_NUMBER;
+  }
+  if (size >= true_len && !strncmp(data, "true", true_len)) {
+    return BEGIN_TRUE;
+  }
+  if (size >= false_len && !strncmp(data, "false", false_len)) {
+    return BEGIN_FALSE;
+  }
+  if (size >= null_len && !strncmp(data, "null", null_len)) {
+    return BEGIN_NULL;
+  }
+  if (*data == '{') return BEGIN_OBJECT;
+  if (*data == '}') return END_OBJECT;
+  if (*data == '[') return BEGIN_ARRAY;
+  if (*data == ']') return END_ARRAY;
+  if (*data == ':') return ENTRY_SEPARATOR;
+  if (*data == ',') return VALUE_SEPARATOR;
+  if (MatchKey(p_)) {
+    return BEGIN_KEY;
+  }
+
+  // We don't know that we necessarily have an invalid token here, just that we
+  // can't parse what we have so far. So we don't report an error and just
+  // return UNKNOWN so we can try again later when we have more data, or if we
+  // finish and we have leftovers.
+  return UNKNOWN;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/json_stream_parser.h b/src/google/protobuf/util/internal/json_stream_parser.h
new file mode 100644
index 0000000..0278c28
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_stream_parser.h
@@ -0,0 +1,258 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_STREAM_PARSER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_STREAM_PARSER_H__
+
+#include <stack>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace util {
+class Status;
+}  // namespace util
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectWriter;
+
+// A JSON parser that can parse a stream of JSON chunks rather than needing the
+// entire JSON string up front. It is a modified version of the parser in
+// //net/proto/json/json-parser.h that has been changed in the following ways:
+// - Changed from recursion to an explicit stack to allow resumption
+// - Added support for int64 and uint64 numbers
+// - Removed support for octal and decimal escapes
+// - Removed support for numeric keys
+// - Removed support for functions (javascript)
+// - Removed some lax-comma support (but kept trailing comma support)
+// - Writes directly to an ObjectWriter rather than using subclassing
+//
+// Here is an example usage:
+// JsonStreamParser parser(ow_.get());
+// util::Status result = parser.Parse(chunk1);
+// result.Update(parser.Parse(chunk2));
+// result.Update(parser.FinishParse());
+// GOOGLE_DCHECK(result.ok()) << "Failed to parse JSON";
+//
+// This parser is thread-compatible as long as only one thread is calling a
+// Parse() method at a time.
+class LIBPROTOBUF_EXPORT JsonStreamParser {
+ public:
+  // Creates a JsonStreamParser that will write to the given ObjectWriter.
+  explicit JsonStreamParser(ObjectWriter* ow);
+  virtual ~JsonStreamParser();
+
+  // Parses a UTF-8 encoded JSON string from a StringPiece.
+  util::Status Parse(StringPiece json);
+
+
+  // Finish parsing the JSON string.
+  util::Status FinishParse();
+
+
+ private:
+  enum TokenType {
+    BEGIN_STRING,     // " or '
+    BEGIN_NUMBER,     // - or digit
+    BEGIN_TRUE,       // true
+    BEGIN_FALSE,      // false
+    BEGIN_NULL,       // null
+    BEGIN_OBJECT,     // {
+    END_OBJECT,       // }
+    BEGIN_ARRAY,      // [
+    END_ARRAY,        // ]
+    ENTRY_SEPARATOR,  // :
+    VALUE_SEPARATOR,  // ,
+    BEGIN_KEY,        // letter, _, $ or digit.  Must begin with non-digit
+    UNKNOWN           // Unknown token or we ran out of the stream.
+  };
+
+  enum ParseType {
+    VALUE,        // Expects a {, [, true, false, null, string or number
+    OBJ_MID,      // Expects a ',' or }
+    ENTRY,        // Expects a key or }
+    ENTRY_MID,    // Expects a :
+    ARRAY_VALUE,  // Expects a value or ]
+    ARRAY_MID     // Expects a ',' or ]
+  };
+
+  // Holds the result of parsing a number
+  struct NumberResult {
+    enum Type { DOUBLE, INT, UINT };
+    Type type;
+    union {
+      double double_val;
+      int64 int_val;
+      uint64 uint_val;
+    };
+  };
+
+  // Parses a single chunk of JSON, returning an error if the JSON was invalid.
+  util::Status ParseChunk(StringPiece json);
+
+  // Runs the parser based on stack_ and p_, until the stack is empty or p_ runs
+  // out of data. If we unexpectedly run out of p_ we push the latest back onto
+  // the stack and return.
+  util::Status RunParser();
+
+  // Parses a value from p_ and writes it to ow_.
+  // A value may be an object, array, true, false, null, string or number.
+  util::Status ParseValue(TokenType type);
+
+  // Parses a string and writes it out to the ow_.
+  util::Status ParseString();
+
+  // Parses a string, storing the result in parsed_.
+  util::Status ParseStringHelper();
+
+  // This function parses unicode escape sequences in strings. It returns an
+  // error when there's a parsing error, either the size is not the expected
+  // size or a character is not a hex digit.  When it returns str will contain
+  // what has been successfully parsed so far.
+  util::Status ParseUnicodeEscape();
+
+  // Expects p_ to point to a JSON number, writes the number to the writer using
+  // the appropriate Render method based on the type of number.
+  util::Status ParseNumber();
+
+  // Parse a number into a NumberResult, reporting an error if no number could
+  // be parsed. This method will try to parse into a uint64, int64, or double
+  // based on whether the number was positive or negative or had a decimal
+  // component.
+  util::Status ParseNumberHelper(NumberResult* result);
+
+  // Handles a { during parsing of a value.
+  util::Status HandleBeginObject();
+
+  // Parses from the ENTRY state.
+  util::Status ParseEntry(TokenType type);
+
+  // Parses from the ENTRY_MID state.
+  util::Status ParseEntryMid(TokenType type);
+
+  // Parses from the OBJ_MID state.
+  util::Status ParseObjectMid(TokenType type);
+
+  // Handles a [ during parsing of a value.
+  util::Status HandleBeginArray();
+
+  // Parses from the ARRAY_VALUE state.
+  util::Status ParseArrayValue(TokenType type);
+
+  // Parses from the ARRAY_MID state.
+  util::Status ParseArrayMid(TokenType type);
+
+  // Expects p_ to point to an unquoted literal
+  util::Status ParseTrue();
+  util::Status ParseFalse();
+  util::Status ParseNull();
+
+  // Report a failure as a util::Status.
+  util::Status ReportFailure(StringPiece message);
+
+  // Report a failure due to an UNKNOWN token type. We check if we hit the
+  // end of the stream and if we're finishing or not to detect what type of
+  // status to return in this case.
+  util::Status ReportUnknown(StringPiece message);
+
+  // Advance p_ past all whitespace or until the end of the string.
+  void SkipWhitespace();
+
+  // Advance p_ one UTF-8 character
+  void Advance();
+
+  // Expects p_ to point to the beginning of a key.
+  util::Status ParseKey();
+
+  // Return the type of the next token at p_.
+  TokenType GetNextTokenType();
+
+  // The object writer to write parse events to.
+  ObjectWriter* ow_;
+
+  // The stack of parsing we still need to do. When the stack runs empty we will
+  // have parsed a single value from the root (e.g. an object or list).
+  std::stack<ParseType> stack_;
+
+  // Contains any leftover text from a previous chunk that we weren't able to
+  // fully parse, for example the start of a key or number.
+  string leftover_;
+
+  // The current chunk of JSON being parsed. Primarily used for providing
+  // context during error reporting.
+  StringPiece json_;
+
+  // A pointer within the current JSON being parsed, used to track location.
+  StringPiece p_;
+
+  // Stores the last key read, as we separate parsing of keys and values.
+  StringPiece key_;
+
+  // Storage for key_ if we need to keep ownership, for example between chunks
+  // or if the key was unescaped from a JSON string.
+  string key_storage_;
+
+  // True during the FinishParse() call, so we know that any errors are fatal.
+  // For example an unterminated string will normally result in cancelling and
+  // trying during the next chunk, but during FinishParse() it is an error.
+  bool finishing_;
+
+  // String we parsed during a call to ParseStringHelper().
+  StringPiece parsed_;
+
+  // Storage for the string we parsed. This may be empty if the string was able
+  // to be parsed directly from the input.
+  string parsed_storage_;
+
+  // The character that opened the string, either ' or ".
+  // A value of 0 indicates that string parsing is not in process.
+  char string_open_;
+
+  // Storage for the chunk that are being parsed in ParseChunk().
+  string chunk_storage_;
+
+  // Whether to allow non UTF-8 encoded input and replace invalid code points.
+  bool coerce_to_utf8_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(JsonStreamParser);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_JSON_STREAM_PARSER_H__
diff --git a/src/google/protobuf/util/internal/json_stream_parser_test.cc b/src/google/protobuf/util/internal/json_stream_parser_test.cc
new file mode 100644
index 0000000..3414826
--- /dev/null
+++ b/src/google/protobuf/util/internal/json_stream_parser_test.cc
@@ -0,0 +1,716 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/json_stream_parser.h>
+
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <gtest/gtest.h>
+#include <google/protobuf/stubs/status.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+using util::Status;
+namespace error {
+using util::error::INVALID_ARGUMENT;
+}  // namespace error
+namespace converter {
+
+using util::Status;
+
+// Tests for the JSON Stream Parser. These tests are intended to be
+// comprehensive and cover the following:
+//
+// Positive tests:
+// - true, false, null
+// - empty object or array.
+// - negative and positive double and int, unsigned int
+// - single and double quoted strings
+// - string key, unquoted key, numeric key
+// - array containing array, object, value
+// - object containing array, object, value
+// - unicode handling in strings
+// - ascii escaping (\b, \f, \n, \r, \t, \v)
+// - trailing commas
+//
+// Negative tests:
+// - illegal literals
+// - mismatched quotes failure on strings
+// - unterminated string failure
+// - unexpected end of string failure
+// - mismatched object and array closing
+// - Failure to close array or object
+// - numbers too large
+// - invalid unicode escapes.
+// - invalid unicode sequences.
+// - numbers as keys
+//
+// For each test we split the input string on every possible character to ensure
+// the parser is able to handle arbitrarily split input for all cases. We also
+// do a final test of the entire test case one character at a time.
+class JsonStreamParserTest : public ::testing::Test {
+ protected:
+  JsonStreamParserTest() : mock_(), ow_(&mock_) {}
+  virtual ~JsonStreamParserTest() {}
+
+  util::Status RunTest(StringPiece json, int split, bool coerce_utf8 = false) {
+    JsonStreamParser parser(&mock_);
+
+    // Special case for split == length, test parsing one character at a time.
+    if (split == json.length()) {
+      GOOGLE_LOG(INFO) << "Testing split every char: " << json;
+      for (int i = 0; i < json.length(); ++i) {
+        StringPiece single = json.substr(i, 1);
+        util::Status result = parser.Parse(single);
+        if (!result.ok()) {
+          return result;
+        }
+      }
+      return parser.FinishParse();
+    }
+
+    // Normal case, split at the split point and parse two substrings.
+    StringPiece first = json.substr(0, split);
+    StringPiece rest = json.substr(split);
+    GOOGLE_LOG(INFO) << "Testing split: " << first << "><" << rest;
+    util::Status result = parser.Parse(first);
+    if (result.ok()) {
+      result = parser.Parse(rest);
+      if (result.ok()) {
+        result = parser.FinishParse();
+      }
+    }
+    return result;
+  }
+
+  void DoTest(StringPiece json, int split, bool coerce_utf8 = false) {
+    util::Status result = RunTest(json, split, coerce_utf8);
+    if (!result.ok()) {
+      GOOGLE_LOG(WARNING) << result;
+    }
+    EXPECT_OK(result);
+  }
+
+  void DoErrorTest(StringPiece json, int split, StringPiece error_prefix) {
+    util::Status result = RunTest(json, split);
+    EXPECT_EQ(util::error::INVALID_ARGUMENT, result.error_code());
+    StringPiece error_message(result.error_message());
+    EXPECT_EQ(error_prefix, error_message.substr(0, error_prefix.size()));
+  }
+
+
+  MockObjectWriter mock_;
+  ExpectingObjectWriter ow_;
+};
+
+
+// Positive tests
+
+// - true, false, null
+TEST_F(JsonStreamParserTest, SimpleTrue) {
+  StringPiece str = "true";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderBool("", true);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleFalse) {
+  StringPiece str = "false";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderBool("", false);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleNull) {
+  StringPiece str = "null";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderNull("");
+    DoTest(str, i);
+  }
+}
+
+// - empty object and array.
+TEST_F(JsonStreamParserTest, EmptyObject) {
+  StringPiece str = "{}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->EndObject();
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, EmptyList) {
+  StringPiece str = "[]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - negative and positive double and int, unsigned int
+TEST_F(JsonStreamParserTest, SimpleDouble) {
+  StringPiece str = "42.5";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderDouble("", 42.5);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, ScientificDouble) {
+  StringPiece str = "1.2345e-10";
+  for (int i = 0; i < str.length(); ++i) {
+    ow_.RenderDouble("", 1.2345e-10);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleNegativeDouble) {
+  StringPiece str = "-1045.235";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderDouble("", -1045.235);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleInt) {
+  StringPiece str = "123456";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderUint64("", 123456);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleNegativeInt) {
+  StringPiece str = "-79497823553162765";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderInt64("", -79497823553162765LL);
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleUnsignedInt) {
+  StringPiece str = "11779497823553162765";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderUint64("", 11779497823553162765ULL);
+    DoTest(str, i);
+  }
+}
+
+// - single and double quoted strings
+TEST_F(JsonStreamParserTest, EmptyDoubleQuotedString) {
+  StringPiece str = "\"\"";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "");
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, EmptySingleQuotedString) {
+  StringPiece str = "''";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "");
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleDoubleQuotedString) {
+  StringPiece str = "\"Some String\"";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "Some String");
+    DoTest(str, i);
+  }
+}
+
+TEST_F(JsonStreamParserTest, SimpleSingleQuotedString) {
+  StringPiece str = "'Another String'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "Another String");
+    DoTest(str, i);
+  }
+}
+
+// - string key, unquoted key, numeric key
+TEST_F(JsonStreamParserTest, ObjectKeyTypes) {
+  StringPiece str =
+      "{'s': true, \"d\": false, key: null, snake_key: [], camelKey: {}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")
+        ->RenderBool("s", true)
+        ->RenderBool("d", false)
+        ->RenderNull("key")
+        ->StartList("snake_key")
+        ->EndList()
+        ->StartObject("camelKey")
+        ->EndObject()
+        ->EndObject();
+    DoTest(str, i);
+  }
+}
+
+// - array containing array, object, values (true, false, null, num, string)
+TEST_F(JsonStreamParserTest, ArrayValues) {
+  StringPiece str =
+      "[true, false, null, 'a string', \"another string\", [22, -127, 45.3, "
+      "-1056.4, 11779497823553162765], {'key': true}]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")
+        ->RenderBool("", true)
+        ->RenderBool("", false)
+        ->RenderNull("")
+        ->RenderString("", "a string")
+        ->RenderString("", "another string")
+        ->StartList("")
+        ->RenderUint64("", 22)
+        ->RenderInt64("", -127)
+        ->RenderDouble("", 45.3)
+        ->RenderDouble("", -1056.4)
+        ->RenderUint64("", 11779497823553162765ULL)
+        ->EndList()
+        ->StartObject("")
+        ->RenderBool("key", true)
+        ->EndObject()
+        ->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - object containing array, object, value (true, false, null, num, string)
+TEST_F(JsonStreamParserTest, ObjectValues) {
+  StringPiece str =
+      "{t: true, f: false, n: null, s: 'a string', d: \"another string\", pi: "
+      "22, ni: -127, pd: 45.3, nd: -1056.4, pl: 11779497823553162765, l: [[]], "
+      "o: {'key': true}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")
+        ->RenderBool("t", true)
+        ->RenderBool("f", false)
+        ->RenderNull("n")
+        ->RenderString("s", "a string")
+        ->RenderString("d", "another string")
+        ->RenderUint64("pi", 22)
+        ->RenderInt64("ni", -127)
+        ->RenderDouble("pd", 45.3)
+        ->RenderDouble("nd", -1056.4)
+        ->RenderUint64("pl", 11779497823553162765ULL)
+        ->StartList("l")
+        ->StartList("")
+        ->EndList()
+        ->EndList()
+        ->StartObject("o")
+        ->RenderBool("key", true)
+        ->EndObject()
+        ->EndObject();
+    DoTest(str, i);
+  }
+}
+
+
+TEST_F(JsonStreamParserTest, RejectNonUtf8WhenNotCoerced) {
+  StringPiece json = "{\"address\":\xFF\"חרושת 23, רעננה, ישראל\"}";
+  for (int i = 0; i <= json.length(); ++i) {
+    DoErrorTest(json, i, "Encountered non UTF-8 code points.");
+  }
+  json = "{\"address\": \"חרושת 23,\xFFרעננה, ישראל\"}";
+  for (int i = 0; i <= json.length(); ++i) {
+    DoErrorTest(json, i, "Encountered non UTF-8 code points.");
+  }
+  DoErrorTest("\xFF{}", 0, "Encountered non UTF-8 code points.");
+}
+
+#ifndef _MSC_VER
+// - unicode handling in strings
+TEST_F(JsonStreamParserTest, UnicodeEscaping) {
+  StringPiece str = "[\"\\u0639\\u0631\\u0628\\u0649\"]";
+  for (int i = 0; i <= str.length(); ++i) {
+    // TODO(xiaofeng): Figure out what default encoding to use for JSON strings.
+    // In protobuf we use UTF-8 for strings, but for JSON we probably should
+    // allow different encodings?
+    ow_.StartList("")->RenderString("", "\u0639\u0631\u0628\u0649")->EndList();
+    DoTest(str, i);
+  }
+}
+#endif
+
+// - ascii escaping (\b, \f, \n, \r, \t, \v)
+TEST_F(JsonStreamParserTest, AsciiEscaping) {
+  StringPiece str =
+      "[\"\\b\", \"\\ning\", \"test\\f\", \"\\r\\t\", \"test\\\\\\ving\"]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")
+        ->RenderString("", "\b")
+        ->RenderString("", "\ning")
+        ->RenderString("", "test\f")
+        ->RenderString("", "\r\t")
+        ->RenderString("", "test\\\ving")
+        ->EndList();
+    DoTest(str, i);
+  }
+}
+
+// - trailing commas, we support a single trailing comma but no internal commas.
+TEST_F(JsonStreamParserTest, TrailingCommas) {
+  StringPiece str = "[['a',true,], {b: null,},]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")
+        ->StartList("")
+        ->RenderString("", "a")
+        ->RenderBool("", true)
+        ->EndList()
+        ->StartObject("")
+        ->RenderNull("b")
+        ->EndObject()
+        ->EndList();
+    DoTest(str, i);
+  }
+}
+
+// Negative tests
+
+// illegal literals
+TEST_F(JsonStreamParserTest, ExtraTextAfterTrue) {
+  StringPiece str = "truee";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderBool("", true);
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidNumberDashOnly) {
+  StringPiece str = "-";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidNumberDashName) {
+  StringPiece str = "-foo";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralInArray) {
+  StringPiece str = "[nule]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unexpected token.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralInObject) {
+  StringPiece str = "{123false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+// mismatched quotes failure on strings
+TEST_F(JsonStreamParserTest, MismatchedSingleQuotedLiteral) {
+  StringPiece str = "'Some str\"";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MismatchedDoubleQuotedLiteral) {
+  StringPiece str = "\"Another string that ends poorly!'";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+// unterminated strings
+TEST_F(JsonStreamParserTest, UnterminatedLiteralString) {
+  StringPiece str = "\"Forgot the rest of i";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedStringEscape) {
+  StringPiece str = "\"Forgot the rest of \\";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedStringInArray) {
+  StringPiece str = "[\"Forgot to close the string]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedStringInObject) {
+  StringPiece str = "{f: \"Forgot to close the string}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Closing quote expected in string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnterminatedObject) {
+  StringPiece str = "{";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Unexpected end of string.");
+  }
+}
+
+
+// mismatched object and array closing
+TEST_F(JsonStreamParserTest, MismatchedCloseObject) {
+  StringPiece str = "{'key': true]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderBool("key", true);
+    DoErrorTest(str, i, "Expected , or } after key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MismatchedCloseArray) {
+  StringPiece str = "[true, null}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderBool("", true)->RenderNull("");
+    DoErrorTest(str, i, "Expected , or ] after array value.");
+  }
+}
+
+// Invalid object keys.
+TEST_F(JsonStreamParserTest, InvalidNumericObjectKey) {
+  StringPiece str = "{42: true}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralObjectInObject) {
+  StringPiece str = "{{bob: true}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralArrayInObject) {
+  StringPiece str = "{[null]}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralValueInObject) {
+  StringPiece str = "{false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingColonAfterStringInObject) {
+  StringPiece str = "{\"key\"}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected : between key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingColonAfterKeyInObject) {
+  StringPiece str = "{key}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected : between key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, EndOfTextAfterKeyInObject) {
+  StringPiece str = "{key";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Unexpected end of string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingValueAfterColonInObject) {
+  StringPiece str = "{key:}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Unexpected token.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, MissingCommaBetweenObjectEntries) {
+  StringPiece str = "{key:20 'hello': true}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderUint64("key", 20);
+    DoErrorTest(str, i, "Expected , or } after key:value pair.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, InvalidLiteralAsObjectKey) {
+  StringPiece str = "{false: 20}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraCharactersAfterObject) {
+  StringPiece str = "{}}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->EndObject();
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+// numbers too large
+TEST_F(JsonStreamParserTest, PositiveNumberTooBig) {
+  StringPiece str = "[18446744073709551616]";  // 2^64
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, NegativeNumberTooBig) {
+  StringPiece str = "[-18446744073709551616]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unable to parse number.");
+  }
+}
+
+/*
+TODO(sven): Fail parsing when parsing a double that is too large.
+
+TEST_F(JsonStreamParserTest, DoubleTooBig) {
+  StringPiece str = "[184464073709551232321616.45]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Unable to parse number");
+  }
+}
+*/
+
+// invalid unicode sequence.
+TEST_F(JsonStreamParserTest, UnicodeEscapeCutOff) {
+  StringPiece str = "\"\\u12";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Illegal hex string.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnicodeEscapeInvalidCharacters) {
+  StringPiece str = "\"\\u12$4hello";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Invalid escape sequence.");
+  }
+}
+
+// Extra commas with an object or array.
+TEST_F(JsonStreamParserTest, ExtraCommaInObject) {
+  StringPiece str = "{'k1': true,,'k2': false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderBool("k1", true);
+    DoErrorTest(str, i, "Expected an object key or }.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraCommaInArray) {
+  StringPiece str = "[true,,false}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderBool("", true);
+    DoErrorTest(str, i, "Unexpected token.");
+  }
+}
+
+// Extra text beyond end of value.
+TEST_F(JsonStreamParserTest, ExtraTextAfterLiteral) {
+  StringPiece str = "'hello', 'world'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.RenderString("", "hello");
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraTextAfterObject) {
+  StringPiece str = "{'key': true} 'oops'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("")->RenderBool("key", true)->EndObject();
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, ExtraTextAfterArray) {
+  StringPiece str = "[null] 'oops'";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("")->RenderNull("")->EndList();
+    DoErrorTest(str, i, "Parsing terminated before end of input.");
+  }
+}
+
+// Random unknown text in the value.
+TEST_F(JsonStreamParserTest, UnknownCharactersAsValue) {
+  StringPiece str = "*&#25";
+  for (int i = 0; i <= str.length(); ++i) {
+    DoErrorTest(str, i, "Expected a value.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnknownCharactersInArray) {
+  StringPiece str = "[*&#25]";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartList("");
+    DoErrorTest(str, i, "Expected a value or ] within an array.");
+  }
+}
+
+TEST_F(JsonStreamParserTest, UnknownCharactersInObject) {
+  StringPiece str = "{'key': *&#25}";
+  for (int i = 0; i <= str.length(); ++i) {
+    ow_.StartObject("");
+    DoErrorTest(str, i, "Expected a value.");
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/location_tracker.h b/src/google/protobuf/util/internal/location_tracker.h
new file mode 100644
index 0000000..0864b05
--- /dev/null
+++ b/src/google/protobuf/util/internal/location_tracker.h
@@ -0,0 +1,65 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_LOCATION_TRACKER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_LOCATION_TRACKER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// LocationTrackerInterface is an interface for classes that track
+// the location information for the purpose of error reporting.
+class LIBPROTOBUF_EXPORT LocationTrackerInterface {
+ public:
+  virtual ~LocationTrackerInterface() {}
+
+  // Returns the object location as human readable string.
+  virtual string ToString() const = 0;
+
+ protected:
+  LocationTrackerInterface() {}
+
+ private:
+  // Please do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(LocationTrackerInterface);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_LOCATION_TRACKER_H__
diff --git a/src/google/protobuf/util/internal/mock_error_listener.h b/src/google/protobuf/util/internal/mock_error_listener.h
new file mode 100644
index 0000000..591c35d
--- /dev/null
+++ b/src/google/protobuf/util/internal/mock_error_listener.h
@@ -0,0 +1,63 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_MOCK_ERROR_LISTENER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_MOCK_ERROR_LISTENER_H__
+
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/location_tracker.h>
+#include <gmock/gmock.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class MockErrorListener : public ErrorListener {
+ public:
+  MockErrorListener() {}
+  virtual ~MockErrorListener() {}
+
+  MOCK_METHOD3(InvalidName, void(const LocationTrackerInterface& loc,
+                                 StringPiece unknown_name,
+                                 StringPiece message));
+  MOCK_METHOD3(InvalidValue, void(const LocationTrackerInterface& loc,
+                                  StringPiece type_name, StringPiece value));
+  MOCK_METHOD2(MissingField, void(const LocationTrackerInterface& loc,
+                                  StringPiece missing_name));
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_MOCK_ERROR_LISTENER_H__
diff --git a/src/google/protobuf/util/internal/object_location_tracker.h b/src/google/protobuf/util/internal/object_location_tracker.h
new file mode 100644
index 0000000..8586cec
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_location_tracker.h
@@ -0,0 +1,64 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_LOCATION_TRACKER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_LOCATION_TRACKER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/location_tracker.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An empty concrete implementation of LocationTrackerInterface.
+class ObjectLocationTracker : public LocationTrackerInterface {
+ public:
+  // Creates an empty location tracker.
+  ObjectLocationTracker() {}
+
+  virtual ~ObjectLocationTracker() {}
+
+  // Returns empty because nothing is tracked.
+  virtual string ToString() const { return ""; }
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ObjectLocationTracker);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_LOCATION_TRACKER_H__
diff --git a/src/google/protobuf/util/internal/object_source.h b/src/google/protobuf/util/internal/object_source.h
new file mode 100644
index 0000000..2c31cfb
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_source.h
@@ -0,0 +1,79 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_SOURCE_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_SOURCE_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectWriter;
+
+// An ObjectSource is anything that can write to an ObjectWriter.
+// Implementation of this interface typically provide constructors or
+// factory methods to create an instance based on some source data, for
+// example, a character stream, or protobuf.
+//
+// Derived classes could be thread-unsafe.
+class LIBPROTOBUF_EXPORT ObjectSource {
+ public:
+  virtual ~ObjectSource() {}
+
+  // Writes to the ObjectWriter
+  virtual util::Status WriteTo(ObjectWriter* ow) const {
+    return NamedWriteTo("", ow);
+  }
+
+  // Writes to the ObjectWriter with a custom name for the message.
+  // This is useful when you chain ObjectSource together by embedding one
+  // within another.
+  virtual util::Status NamedWriteTo(StringPiece name,
+                                      ObjectWriter* ow) const = 0;
+
+ protected:
+  ObjectSource() {}
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ObjectSource);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_SOURCE_H__
diff --git a/src/google/protobuf/util/internal/object_writer.cc b/src/google/protobuf/util/internal/object_writer.cc
new file mode 100644
index 0000000..57cc08a
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_writer.cc
@@ -0,0 +1,92 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/object_writer.h>
+
+#include <google/protobuf/util/internal/datapiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// static
+void ObjectWriter::RenderDataPieceTo(const DataPiece& data, StringPiece name,
+                                     ObjectWriter* ow) {
+  switch (data.type()) {
+    case DataPiece::TYPE_INT32: {
+      ow->RenderInt32(name, data.ToInt32().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_INT64: {
+      ow->RenderInt64(name, data.ToInt64().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_UINT32: {
+      ow->RenderUint32(name, data.ToUint32().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_UINT64: {
+      ow->RenderUint64(name, data.ToUint64().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_DOUBLE: {
+      ow->RenderDouble(name, data.ToDouble().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_FLOAT: {
+      ow->RenderFloat(name, data.ToFloat().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_BOOL: {
+      ow->RenderBool(name, data.ToBool().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_STRING: {
+      ow->RenderString(name, data.ToString().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_BYTES: {
+      ow->RenderBytes(name, data.ToBytes().ValueOrDie());
+      break;
+    }
+    case DataPiece::TYPE_NULL: {
+      ow->RenderNull(name);
+      break;
+    }
+    default:
+      break;
+  }
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/object_writer.h b/src/google/protobuf/util/internal/object_writer.h
new file mode 100644
index 0000000..e695f45
--- /dev/null
+++ b/src/google/protobuf/util/internal/object_writer.h
@@ -0,0 +1,121 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_WRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_WRITER_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringpiece.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class DataPiece;
+
+// An ObjectWriter is an interface for writing a stream of events
+// representing objects and collections. Implementation of this
+// interface can be used to write an object stream to an in-memory
+// structure, protobufs, JSON, XML, or any other output format
+// desired. The ObjectSource interface is typically used as the
+// source of an object stream.
+//
+// See JsonObjectWriter for a sample implementation of ObjectWriter
+// and its use.
+//
+// Derived classes could be thread-unsafe.
+//
+// TODO(xinb): seems like a prime candidate to apply the RAII paradigm
+// and get rid the need to call EndXXX().
+class LIBPROTOBUF_EXPORT ObjectWriter {
+ public:
+  virtual ~ObjectWriter() {}
+
+  // Starts an object. If the name is empty, the object will not be named.
+  virtual ObjectWriter* StartObject(StringPiece name) = 0;
+
+  // Ends an object.
+  virtual ObjectWriter* EndObject() = 0;
+
+  // Starts a list. If the name is empty, the list will not be named.
+  virtual ObjectWriter* StartList(StringPiece name) = 0;
+
+  // Ends a list.
+  virtual ObjectWriter* EndList() = 0;
+
+  // Renders a boolean value.
+  virtual ObjectWriter* RenderBool(StringPiece name, bool value) = 0;
+
+  // Renders an 32-bit integer value.
+  virtual ObjectWriter* RenderInt32(StringPiece name, int32 value) = 0;
+
+  // Renders an 32-bit unsigned integer value.
+  virtual ObjectWriter* RenderUint32(StringPiece name, uint32 value) = 0;
+
+  // Renders a 64-bit integer value.
+  virtual ObjectWriter* RenderInt64(StringPiece name, int64 value) = 0;
+
+  // Renders an 64-bit unsigned integer value.
+  virtual ObjectWriter* RenderUint64(StringPiece name, uint64 value) = 0;
+
+  // Renders a double value.
+  virtual ObjectWriter* RenderDouble(StringPiece name, double value) = 0;
+
+  // Renders a float value.
+  virtual ObjectWriter* RenderFloat(StringPiece name, float value) = 0;
+
+  // Renders a StringPiece value. This is for rendering strings.
+  virtual ObjectWriter* RenderString(StringPiece name, StringPiece value) = 0;
+
+  // Renders a bytes value.
+  virtual ObjectWriter* RenderBytes(StringPiece name, StringPiece value) = 0;
+
+  // Renders a Null value.
+  virtual ObjectWriter* RenderNull(StringPiece name) = 0;
+
+  // Renders a DataPiece object to a ObjectWriter.
+  static void RenderDataPieceTo(const DataPiece& data, StringPiece name,
+                                ObjectWriter* ow);
+
+ protected:
+  ObjectWriter() {}
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_OBJECT_WRITER_H__
diff --git a/src/google/protobuf/util/internal/proto_writer.cc b/src/google/protobuf/util/internal/proto_writer.cc
new file mode 100644
index 0000000..47e0009
--- /dev/null
+++ b/src/google/protobuf/util/internal/proto_writer.cc
@@ -0,0 +1,744 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/proto_writer.h>
+
+#include <functional>
+#include <stack>
+
+#include <google/protobuf/stubs/once.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/wire_format_lite.h>
+#include <google/protobuf/util/internal/field_mask_utility.h>
+#include <google/protobuf/util/internal/object_location_tracker.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::internal::WireFormatLite;
+using google::protobuf::io::CodedOutputStream;
+using util::error::INVALID_ARGUMENT;
+using util::Status;
+using util::StatusOr;
+
+
+ProtoWriter::ProtoWriter(TypeResolver* type_resolver,
+                         const google::protobuf::Type& type,
+                         strings::ByteSink* output, ErrorListener* listener)
+    : master_type_(type),
+      typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      own_typeinfo_(true),
+      done_(false),
+      element_(NULL),
+      size_insert_(),
+      output_(output),
+      buffer_(),
+      adapter_(&buffer_),
+      stream_(new CodedOutputStream(&adapter_)),
+      listener_(listener),
+      invalid_depth_(0),
+      tracker_(new ObjectLocationTracker()) {}
+
+ProtoWriter::ProtoWriter(const TypeInfo* typeinfo,
+                         const google::protobuf::Type& type,
+                         strings::ByteSink* output, ErrorListener* listener)
+    : master_type_(type),
+      typeinfo_(typeinfo),
+      own_typeinfo_(false),
+      done_(false),
+      element_(NULL),
+      size_insert_(),
+      output_(output),
+      buffer_(),
+      adapter_(&buffer_),
+      stream_(new CodedOutputStream(&adapter_)),
+      listener_(listener),
+      invalid_depth_(0),
+      tracker_(new ObjectLocationTracker()) {}
+
+ProtoWriter::~ProtoWriter() {
+  if (own_typeinfo_) {
+    delete typeinfo_;
+  }
+  if (element_ == NULL) return;
+  // Cleanup explicitly in order to avoid destructor stack overflow when input
+  // is deeply nested.
+  // Cast to BaseElement to avoid doing additional checks (like missing fields)
+  // during pop().
+  google::protobuf::scoped_ptr<BaseElement> element(
+      static_cast<BaseElement*>(element_.get())->pop<BaseElement>());
+  while (element != NULL) {
+    element.reset(element->pop<BaseElement>());
+  }
+}
+
+namespace {
+
+// Writes an INT32 field, including tag to the stream.
+inline Status WriteInt32(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteInt32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// writes an SFIXED32 field, including tag, to the stream.
+inline Status WriteSFixed32(int field_number, const DataPiece& data,
+                            CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteSFixed32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// Writes an SINT32 field, including tag, to the stream.
+inline Status WriteSInt32(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<int32> i32 = data.ToInt32();
+  if (i32.ok()) {
+    WireFormatLite::WriteSInt32(field_number, i32.ValueOrDie(), stream);
+  }
+  return i32.status();
+}
+
+// Writes a FIXED32 field, including tag, to the stream.
+inline Status WriteFixed32(int field_number, const DataPiece& data,
+                           CodedOutputStream* stream) {
+  StatusOr<uint32> u32 = data.ToUint32();
+  if (u32.ok()) {
+    WireFormatLite::WriteFixed32(field_number, u32.ValueOrDie(), stream);
+  }
+  return u32.status();
+}
+
+// Writes a UINT32 field, including tag, to the stream.
+inline Status WriteUInt32(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<uint32> u32 = data.ToUint32();
+  if (u32.ok()) {
+    WireFormatLite::WriteUInt32(field_number, u32.ValueOrDie(), stream);
+  }
+  return u32.status();
+}
+
+// Writes an INT64 field, including tag, to the stream.
+inline Status WriteInt64(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteInt64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes an SFIXED64 field, including tag, to the stream.
+inline Status WriteSFixed64(int field_number, const DataPiece& data,
+                            CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteSFixed64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes an SINT64 field, including tag, to the stream.
+inline Status WriteSInt64(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<int64> i64 = data.ToInt64();
+  if (i64.ok()) {
+    WireFormatLite::WriteSInt64(field_number, i64.ValueOrDie(), stream);
+  }
+  return i64.status();
+}
+
+// Writes a FIXED64 field, including tag, to the stream.
+inline Status WriteFixed64(int field_number, const DataPiece& data,
+                           CodedOutputStream* stream) {
+  StatusOr<uint64> u64 = data.ToUint64();
+  if (u64.ok()) {
+    WireFormatLite::WriteFixed64(field_number, u64.ValueOrDie(), stream);
+  }
+  return u64.status();
+}
+
+// Writes a UINT64 field, including tag, to the stream.
+inline Status WriteUInt64(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<uint64> u64 = data.ToUint64();
+  if (u64.ok()) {
+    WireFormatLite::WriteUInt64(field_number, u64.ValueOrDie(), stream);
+  }
+  return u64.status();
+}
+
+// Writes a DOUBLE field, including tag, to the stream.
+inline Status WriteDouble(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<double> d = data.ToDouble();
+  if (d.ok()) {
+    WireFormatLite::WriteDouble(field_number, d.ValueOrDie(), stream);
+  }
+  return d.status();
+}
+
+// Writes a FLOAT field, including tag, to the stream.
+inline Status WriteFloat(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<float> f = data.ToFloat();
+  if (f.ok()) {
+    WireFormatLite::WriteFloat(field_number, f.ValueOrDie(), stream);
+  }
+  return f.status();
+}
+
+// Writes a BOOL field, including tag, to the stream.
+inline Status WriteBool(int field_number, const DataPiece& data,
+                        CodedOutputStream* stream) {
+  StatusOr<bool> b = data.ToBool();
+  if (b.ok()) {
+    WireFormatLite::WriteBool(field_number, b.ValueOrDie(), stream);
+  }
+  return b.status();
+}
+
+// Writes a BYTES field, including tag, to the stream.
+inline Status WriteBytes(int field_number, const DataPiece& data,
+                         CodedOutputStream* stream) {
+  StatusOr<string> c = data.ToBytes();
+  if (c.ok()) {
+    WireFormatLite::WriteBytes(field_number, c.ValueOrDie(), stream);
+  }
+  return c.status();
+}
+
+// Writes a STRING field, including tag, to the stream.
+inline Status WriteString(int field_number, const DataPiece& data,
+                          CodedOutputStream* stream) {
+  StatusOr<string> s = data.ToString();
+  if (s.ok()) {
+    WireFormatLite::WriteString(field_number, s.ValueOrDie(), stream);
+  }
+  return s.status();
+}
+
+// Writes an ENUM field, including tag, to the stream.
+inline Status WriteEnum(int field_number, const DataPiece& data,
+                        const google::protobuf::Enum* enum_type,
+                        CodedOutputStream* stream) {
+  StatusOr<int> e = data.ToEnum(enum_type);
+  if (e.ok()) {
+    WireFormatLite::WriteEnum(field_number, e.ValueOrDie(), stream);
+  }
+  return e.status();
+}
+
+// Given a google::protobuf::Type, returns the set of all required fields.
+std::set<const google::protobuf::Field*> GetRequiredFields(
+    const google::protobuf::Type& type) {
+  std::set<const google::protobuf::Field*> required;
+  for (int i = 0; i < type.fields_size(); i++) {
+    const google::protobuf::Field& field = type.fields(i);
+    if (field.cardinality() ==
+        google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
+      required.insert(&field);
+    }
+  }
+  return required;
+}
+
+}  // namespace
+
+ProtoWriter::ProtoElement::ProtoElement(const TypeInfo* typeinfo,
+                                        const google::protobuf::Type& type,
+                                        ProtoWriter* enclosing)
+    : BaseElement(NULL),
+      ow_(enclosing),
+      parent_field_(NULL),
+      typeinfo_(typeinfo),
+      type_(type),
+      required_fields_(GetRequiredFields(type)),
+      size_index_(-1),
+      array_index_(-1) {}
+
+ProtoWriter::ProtoElement::ProtoElement(ProtoWriter::ProtoElement* parent,
+                                        const google::protobuf::Field* field,
+                                        const google::protobuf::Type& type,
+                                        bool is_list)
+    : BaseElement(parent),
+      ow_(this->parent()->ow_),
+      parent_field_(field),
+      typeinfo_(this->parent()->typeinfo_),
+      type_(type),
+      size_index_(
+          !is_list && field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE
+              ? ow_->size_insert_.size()
+              : -1),
+      array_index_(is_list ? 0 : -1) {
+  if (!is_list) {
+    if (ow_->IsRepeated(*field)) {
+      // Update array_index_ if it is an explicit list.
+      if (this->parent()->array_index_ >= 0) this->parent()->array_index_++;
+    } else {
+      this->parent()->RegisterField(field);
+    }
+
+    if (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+      required_fields_ = GetRequiredFields(type_);
+      int start_pos = ow_->stream_->ByteCount();
+      // length of serialized message is the final buffer position minus
+      // starting buffer position, plus length adjustments for size fields
+      // of any nested messages. We start with -start_pos here, so we only
+      // need to add the final buffer position to it at the end.
+      SizeInfo info = {start_pos, -start_pos};
+      ow_->size_insert_.push_back(info);
+    }
+  }
+}
+
+ProtoWriter::ProtoElement* ProtoWriter::ProtoElement::pop() {
+  // Calls the registered error listener for any required field(s) not yet
+  // seen.
+  for (set<const google::protobuf::Field*>::iterator it =
+           required_fields_.begin();
+       it != required_fields_.end(); ++it) {
+    ow_->MissingField((*it)->name());
+  }
+  // Computes the total number of proto bytes used by a message, also adjusts
+  // the size of all parent messages by the length of this size field.
+  // If size_index_ < 0, this is not a message, so no size field is added.
+  if (size_index_ >= 0) {
+    // Add the final buffer position to compute the total length of this
+    // serialized message. The stored value (before this addition) already
+    // contains the total length of the size fields of all nested messages
+    // minus the initial buffer position.
+    ow_->size_insert_[size_index_].size += ow_->stream_->ByteCount();
+    // Calculate the length required to serialize the size field of the
+    // message, and propagate this additional size information upward to
+    // all enclosing messages.
+    int size = ow_->size_insert_[size_index_].size;
+    int length = CodedOutputStream::VarintSize32(size);
+    for (ProtoElement* e = parent(); e != NULL; e = e->parent()) {
+      // Only nested messages have size field, lists do not have size field.
+      if (e->size_index_ >= 0) {
+        ow_->size_insert_[e->size_index_].size += length;
+      }
+    }
+  }
+  return BaseElement::pop<ProtoElement>();
+}
+
+void ProtoWriter::ProtoElement::RegisterField(
+    const google::protobuf::Field* field) {
+  if (!required_fields_.empty() &&
+      field->cardinality() ==
+          google::protobuf::Field_Cardinality_CARDINALITY_REQUIRED) {
+    required_fields_.erase(field);
+  }
+}
+
+string ProtoWriter::ProtoElement::ToString() const {
+  if (parent() == NULL) return "";
+  string loc = parent()->ToString();
+  if (!ow_->IsRepeated(*parent_field_) ||
+      parent()->parent_field_ != parent_field_) {
+    string name = parent_field_->name();
+    int i = 0;
+    while (i < name.size() && (ascii_isalnum(name[i]) || name[i] == '_')) ++i;
+    if (i > 0 && i == name.size()) {  // safe field name
+      if (loc.empty()) {
+        loc = name;
+      } else {
+        StrAppend(&loc, ".", name);
+      }
+    } else {
+      StrAppend(&loc, "[\"", CEscape(name), "\"]");
+    }
+  }
+  if (ow_->IsRepeated(*parent_field_) && array_index_ > 0) {
+    StrAppend(&loc, "[", array_index_ - 1, "]");
+  }
+  return loc.empty() ? "." : loc;
+}
+
+bool ProtoWriter::ProtoElement::IsOneofIndexTaken(int32 index) {
+  return ContainsKey(oneof_indices_, index);
+}
+
+void ProtoWriter::ProtoElement::TakeOneofIndex(int32 index) {
+  InsertIfNotPresent(&oneof_indices_, index);
+}
+
+void ProtoWriter::InvalidName(StringPiece unknown_name, StringPiece message) {
+  listener_->InvalidName(location(), ToSnakeCase(unknown_name), message);
+}
+
+void ProtoWriter::InvalidValue(StringPiece type_name, StringPiece value) {
+  listener_->InvalidValue(location(), type_name, value);
+}
+
+void ProtoWriter::MissingField(StringPiece missing_name) {
+  listener_->MissingField(location(), missing_name);
+}
+
+ProtoWriter* ProtoWriter::StartObject(StringPiece name) {
+  // Starting the root message. Create the root ProtoElement and return.
+  if (element_ == NULL) {
+    if (!name.empty()) {
+      InvalidName(name, "Root element should not be named.");
+    }
+    element_.reset(new ProtoElement(typeinfo_, master_type_, this));
+    return this;
+  }
+
+  const google::protobuf::Field* field = NULL;
+  field = BeginNamed(name, false);
+  if (field == NULL) return this;
+
+  // Check to see if this field is a oneof and that no oneof in that group has
+  // already been set.
+  if (!ValidOneof(*field, name)) {
+    ++invalid_depth_;
+    return this;
+  }
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    ++invalid_depth_;
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+    WriteTag(*field);
+  element_.reset(new ProtoElement(element_.release(), field, *type, false));
+  return this;
+}
+
+ProtoWriter* ProtoWriter::EndObject() {
+  if (invalid_depth_ > 0) {
+    --invalid_depth_;
+    return this;
+  }
+
+  if (element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+
+
+  // If ending the root element,
+  // then serialize the full message with calculated sizes.
+  if (element_ == NULL) {
+    WriteRootMessage();
+  }
+  return this;
+}
+
+ProtoWriter* ProtoWriter::StartList(StringPiece name) {
+  const google::protobuf::Field* field = BeginNamed(name, true);
+  if (field == NULL) return this;
+
+  if (!ValidOneof(*field, name)) {
+    ++invalid_depth_;
+    return this;
+  }
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    ++invalid_depth_;
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  element_.reset(new ProtoElement(element_.release(), field, *type, true));
+  return this;
+}
+
+ProtoWriter* ProtoWriter::EndList() {
+  if (invalid_depth_ > 0) {
+    --invalid_depth_;
+  } else if (element_ != NULL) {
+    element_.reset(element_->pop());
+  }
+  return this;
+}
+
+ProtoWriter* ProtoWriter::RenderDataPiece(StringPiece name,
+                                          const DataPiece& data) {
+  Status status;
+  if (invalid_depth_ > 0) return this;
+
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) return this;
+
+  if (!ValidOneof(*field, name)) return this;
+
+  const google::protobuf::Type* type = LookupType(field);
+  if (type == NULL) {
+    InvalidName(name,
+                StrCat("Missing descriptor for field: ", field->type_url()));
+    return this;
+  }
+
+  // Pushing a ProtoElement and then pop it off at the end for 2 purposes:
+  // error location reporting and required field accounting.
+  element_.reset(new ProtoElement(element_.release(), field, *type, false));
+
+  if (field->kind() == google::protobuf::Field_Kind_TYPE_UNKNOWN ||
+      field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+    InvalidValue(field->type_url().empty()
+                     ? google::protobuf::Field_Kind_Name(field->kind())
+                     : field->type_url(),
+                 data.ValueAsStringOrDefault(""));
+    element_.reset(element()->pop());
+    return this;
+  }
+
+  switch (field->kind()) {
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      status = WriteInt32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      status = WriteSFixed32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      status = WriteSInt32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      status = WriteFixed32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      status = WriteUInt32(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      status = WriteInt64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      status = WriteSFixed64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      status = WriteSInt64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      status = WriteFixed64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      status = WriteUInt64(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      status = WriteDouble(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      status = WriteFloat(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      status = WriteBool(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      status = WriteBytes(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      status = WriteString(field->number(), data, stream_.get());
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      status = WriteEnum(field->number(), data,
+                         typeinfo_->GetEnumByTypeUrl(field->type_url()),
+                         stream_.get());
+      break;
+    }
+    default:  // TYPE_GROUP or TYPE_MESSAGE
+      status = Status(INVALID_ARGUMENT, data.ToString().ValueOrDie());
+  }
+
+  if (!status.ok()) {
+    InvalidValue(google::protobuf::Field_Kind_Name(field->kind()),
+                 status.error_message());
+  }
+
+  element_.reset(element()->pop());
+  return this;
+}
+
+bool ProtoWriter::ValidOneof(const google::protobuf::Field& field,
+                             StringPiece unnormalized_name) {
+  if (element_ == NULL) return true;
+
+  if (field.oneof_index() > 0) {
+    if (element_->IsOneofIndexTaken(field.oneof_index())) {
+      InvalidValue(
+          "oneof",
+          StrCat("oneof field '",
+                 element_->type().oneofs(field.oneof_index() - 1),
+                 "' is already set. Cannot set '", unnormalized_name, "'"));
+      return false;
+    }
+    element_->TakeOneofIndex(field.oneof_index());
+  }
+  return true;
+}
+
+bool ProtoWriter::IsRepeated(const google::protobuf::Field& field) {
+  return field.cardinality() ==
+         google::protobuf::Field_Cardinality_CARDINALITY_REPEATED;
+}
+
+const google::protobuf::Field* ProtoWriter::BeginNamed(StringPiece name,
+                                                       bool is_list) {
+  if (invalid_depth_ > 0) {
+    ++invalid_depth_;
+    return NULL;
+  }
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) {
+    ++invalid_depth_;
+    // InvalidName() already called in Lookup().
+    return NULL;
+  }
+  if (is_list && !IsRepeated(*field)) {
+    ++invalid_depth_;
+    InvalidName(name, "Proto field is not repeating, cannot start list.");
+    return NULL;
+  }
+  return field;
+}
+
+const google::protobuf::Field* ProtoWriter::Lookup(
+    StringPiece unnormalized_name) {
+  ProtoElement* e = element();
+  if (e == NULL) {
+    InvalidName(unnormalized_name, "Root element must be a message.");
+    return NULL;
+  }
+  if (unnormalized_name.empty()) {
+    // Objects in repeated field inherit the same field descriptor.
+    if (e->parent_field() == NULL) {
+      InvalidName(unnormalized_name, "Proto fields must have a name.");
+    } else if (!IsRepeated(*e->parent_field())) {
+      InvalidName(unnormalized_name, "Proto fields must have a name.");
+      return NULL;
+    }
+    return e->parent_field();
+  }
+  const google::protobuf::Field* field =
+      typeinfo_->FindField(&e->type(), unnormalized_name);
+  if (field == NULL) InvalidName(unnormalized_name, "Cannot find field.");
+  return field;
+}
+
+const google::protobuf::Type* ProtoWriter::LookupType(
+    const google::protobuf::Field* field) {
+  return ((field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE ||
+           field->kind() == google::protobuf::Field_Kind_TYPE_GROUP)
+              ? typeinfo_->GetTypeByTypeUrl(field->type_url())
+              : &element_->type());
+}
+
+void ProtoWriter::WriteRootMessage() {
+  GOOGLE_DCHECK(!done_);
+  int curr_pos = 0;
+  // Calls the destructor of CodedOutputStream to remove any uninitialized
+  // memory from the Cord before we read it.
+  stream_.reset(NULL);
+  const void* data;
+  int length;
+  google::protobuf::io::ArrayInputStream input_stream(buffer_.data(), buffer_.size());
+  while (input_stream.Next(&data, &length)) {
+    if (length == 0) continue;
+    int num_bytes = length;
+    // Write up to where we need to insert the size field.
+    // The number of bytes we may write is the smaller of:
+    //   - the current fragment size
+    //   - the distance to the next position where a size field needs to be
+    //     inserted.
+    if (!size_insert_.empty() &&
+        size_insert_.front().pos - curr_pos < num_bytes) {
+      num_bytes = size_insert_.front().pos - curr_pos;
+    }
+    output_->Append(static_cast<const char*>(data), num_bytes);
+    if (num_bytes < length) {
+      input_stream.BackUp(length - num_bytes);
+    }
+    curr_pos += num_bytes;
+    // Insert the size field.
+    //   size_insert_.front():      the next <index, size> pair to be written.
+    //   size_insert_.front().pos:  position of the size field.
+    //   size_insert_.front().size: the size (integer) to be inserted.
+    if (!size_insert_.empty() && curr_pos == size_insert_.front().pos) {
+      // Varint32 occupies at most 10 bytes.
+      uint8 insert_buffer[10];
+      uint8* insert_buffer_pos = CodedOutputStream::WriteVarint32ToArray(
+          size_insert_.front().size, insert_buffer);
+      output_->Append(reinterpret_cast<const char*>(insert_buffer),
+                      insert_buffer_pos - insert_buffer);
+      size_insert_.pop_front();
+    }
+  }
+  output_->Flush();
+  stream_.reset(new CodedOutputStream(&adapter_));
+  done_ = true;
+}
+
+void ProtoWriter::WriteTag(const google::protobuf::Field& field) {
+  WireFormatLite::WireType wire_type = WireFormatLite::WireTypeForFieldType(
+      static_cast<WireFormatLite::FieldType>(field.kind()));
+  stream_->WriteTag(WireFormatLite::MakeTag(field.number(), wire_type));
+}
+
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/proto_writer.h b/src/google/protobuf/util/internal/proto_writer.h
new file mode 100644
index 0000000..e631e56
--- /dev/null
+++ b/src/google/protobuf/util/internal/proto_writer.h
@@ -0,0 +1,315 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTO_WRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTO_WRITER_H__
+
+#include <deque>
+#include <google/protobuf/stubs/hash.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/datapiece.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/structured_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+class CodedOutputStream;
+}  // namespace io
+}  // namespace protobuf
+
+
+namespace protobuf {
+class Type;
+class Field;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectLocationTracker;
+
+// An ObjectWriter that can write protobuf bytes directly from writer events.
+// This class does not support special types like Struct or Map. However, since
+// this class supports raw protobuf, it can be used to provide support for
+// special types by inheriting from it or by wrapping it.
+//
+// It also supports streaming.
+class LIBPROTOBUF_EXPORT ProtoWriter : public StructuredObjectWriter {
+ public:
+// Constructor. Does not take ownership of any parameter passed in.
+  ProtoWriter(TypeResolver* type_resolver, const google::protobuf::Type& type,
+              strings::ByteSink* output, ErrorListener* listener);
+  virtual ~ProtoWriter();
+
+  // ObjectWriter methods.
+  virtual ProtoWriter* StartObject(StringPiece name);
+  virtual ProtoWriter* EndObject();
+  virtual ProtoWriter* StartList(StringPiece name);
+  virtual ProtoWriter* EndList();
+  virtual ProtoWriter* RenderBool(StringPiece name, bool value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderInt32(StringPiece name, int32 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderUint32(StringPiece name, uint32 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderInt64(StringPiece name, int64 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderUint64(StringPiece name, uint64 value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderDouble(StringPiece name, double value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderFloat(StringPiece name, float value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderString(StringPiece name, StringPiece value) {
+    return RenderDataPiece(name, DataPiece(value));
+  }
+  virtual ProtoWriter* RenderBytes(StringPiece name, StringPiece value) {
+    return RenderDataPiece(name, DataPiece(value, false));
+  }
+  virtual ProtoWriter* RenderNull(StringPiece name) {
+    return RenderDataPiece(name, DataPiece::NullData());
+  }
+
+  // Renders a DataPiece 'value' into a field whose wire type is determined
+  // from the given field 'name'.
+  virtual ProtoWriter* RenderDataPiece(StringPiece name,
+                                       const DataPiece& value);
+
+  // Returns the location tracker to use for tracking locations for errors.
+  const LocationTrackerInterface& location() {
+    return element_ != NULL ? *element_ : *tracker_;
+  }
+
+  // When true, we finished writing to output a complete message.
+  bool done() const { return done_; }
+
+  // Returns the proto stream object.
+  google::protobuf::io::CodedOutputStream* stream() { return stream_.get(); }
+
+  // Getters and mutators of invalid_depth_.
+  void IncrementInvalidDepth() { ++invalid_depth_; }
+  void DecrementInvalidDepth() { --invalid_depth_; }
+  int invalid_depth() { return invalid_depth_; }
+
+  ErrorListener* listener() { return listener_; }
+
+  const TypeInfo* typeinfo() { return typeinfo_; }
+
+ protected:
+  class LIBPROTOBUF_EXPORT ProtoElement : public BaseElement, public LocationTrackerInterface {
+   public:
+    // Constructor for the root element. No parent nor field.
+    ProtoElement(const TypeInfo* typeinfo, const google::protobuf::Type& type,
+                 ProtoWriter* enclosing);
+
+    // Constructor for a field of an element.
+    ProtoElement(ProtoElement* parent, const google::protobuf::Field* field,
+                 const google::protobuf::Type& type, bool is_list);
+
+    virtual ~ProtoElement() {}
+
+    // Called just before the destructor for clean up:
+    //   - reports any missing required fields
+    //   - computes the space needed by the size field, and augment the
+    //     length of all parent messages by this additional space.
+    //   - releases and returns the parent pointer.
+    ProtoElement* pop();
+
+    // Accessors
+    // parent_field() may be NULL if we are at root.
+    const google::protobuf::Field* parent_field() const {
+      return parent_field_;
+    }
+    const google::protobuf::Type& type() const { return type_; }
+
+    // Registers field for accounting required fields.
+    void RegisterField(const google::protobuf::Field* field);
+
+    // To report location on error messages.
+    virtual string ToString() const;
+
+    virtual ProtoElement* parent() const {
+      return static_cast<ProtoElement*>(BaseElement::parent());
+    }
+
+    // Returns true if the index is already taken by a preceeding oneof input.
+    bool IsOneofIndexTaken(int32 index);
+
+    // Marks the oneof 'index' as taken. Future inputs to this oneof will
+    // generate an error.
+    void TakeOneofIndex(int32 index);
+
+   private:
+    // Used for access to variables of the enclosing instance of
+    // ProtoWriter.
+    ProtoWriter* ow_;
+
+    // Describes the element as a field in the parent message.
+    // parent_field_ is NULL if and only if this element is the root element.
+    const google::protobuf::Field* parent_field_;
+
+    // TypeInfo to lookup types.
+    const TypeInfo* typeinfo_;
+
+    // Additional variables if this element is a message:
+    // (Root element is always a message).
+    // type_             : the type of this element.
+    // required_fields_  : set of required fields.
+    // size_index_       : index into ProtoWriter::size_insert_
+    //                     for later insertion of serialized message length.
+    const google::protobuf::Type& type_;
+    std::set<const google::protobuf::Field*> required_fields_;
+    const int size_index_;
+
+    // Tracks position in repeated fields, needed for LocationTrackerInterface.
+    int array_index_;
+
+    // Set of oneof indices already seen for the type_. Used to validate
+    // incoming messages so no more than one oneof is set.
+    hash_set<int32> oneof_indices_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoElement);
+  };
+
+  // Container for inserting 'size' information at the 'pos' position.
+  struct SizeInfo {
+    const int pos;
+    int size;
+  };
+
+  ProtoWriter(const TypeInfo* typeinfo, const google::protobuf::Type& type,
+              strings::ByteSink* output, ErrorListener* listener);
+
+  virtual ProtoElement* element() { return element_.get(); }
+
+  // Helper methods for calling ErrorListener. See error_listener.h.
+  void InvalidName(StringPiece unknown_name, StringPiece message);
+  void InvalidValue(StringPiece type_name, StringPiece value);
+  void MissingField(StringPiece missing_name);
+
+  // Common code for BeginObject() and BeginList() that does invalid_depth_
+  // bookkeeping associated with name lookup.
+  const google::protobuf::Field* BeginNamed(StringPiece name, bool is_list);
+
+  // Lookup the field in the current element. Looks in the base descriptor
+  // and in any extension. This will report an error if the field cannot be
+  // found or if multiple matching extensions are found.
+  const google::protobuf::Field* Lookup(StringPiece name);
+
+  // Lookup the field type in the type descriptor. Returns NULL if the type
+  // is not known.
+  const google::protobuf::Type* LookupType(
+      const google::protobuf::Field* field);
+
+  // Write serialized output to the final output ByteSink, inserting all
+  // the size information for nested messages that are missing from the
+  // intermediate Cord buffer.
+  void WriteRootMessage();
+
+  // Helper method to write proto tags based on the given field.
+  void WriteTag(const google::protobuf::Field& field);
+
+
+  // Returns true if the field for type_ can be set as a oneof. If field is not
+  // a oneof type, this function does nothing and returns true.
+  // If another field for this oneof is already set, this function returns
+  // false. It also calls the appropriate error callback.
+  // unnormalized_name is used for error string.
+  bool ValidOneof(const google::protobuf::Field& field,
+                  StringPiece unnormalized_name);
+
+  // Returns true if the field is repeated.
+  bool IsRepeated(const google::protobuf::Field& field);
+
+ private:
+  // Variables for describing the structure of the input tree:
+  // master_type_: descriptor for the whole protobuf message.
+  // typeinfo_ : the TypeInfo object to lookup types.
+  const google::protobuf::Type& master_type_;
+  const TypeInfo* typeinfo_;
+  // Whether we own the typeinfo_ object.
+  bool own_typeinfo_;
+
+  // Indicates whether we finished writing root message completely.
+  bool done_;
+
+  // Variable for internal state processing:
+  // element_    : the current element.
+  // size_insert_: sizes of nested messages.
+  //               pos  - position to insert the size field.
+  //               size - size value to be inserted.
+  google::protobuf::scoped_ptr<ProtoElement> element_;
+  std::deque<SizeInfo> size_insert_;
+
+  // Variables for output generation:
+  // output_  : pointer to an external ByteSink for final user-visible output.
+  // buffer_  : buffer holding partial message before being ready for output_.
+  // adapter_ : internal adapter between CodedOutputStream and buffer_.
+  // stream_  : wrapper for writing tags and other encodings in wire format.
+  strings::ByteSink* output_;
+  string buffer_;
+  google::protobuf::io::StringOutputStream adapter_;
+  google::protobuf::scoped_ptr<google::protobuf::io::CodedOutputStream> stream_;
+
+  // Variables for error tracking and reporting:
+  // listener_     : a place to report any errors found.
+  // invalid_depth_: number of enclosing invalid nested messages.
+  // tracker_      : the root location tracker interface.
+  ErrorListener* listener_;
+  int invalid_depth_;
+  google::protobuf::scoped_ptr<LocationTrackerInterface> tracker_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTO_WRITER_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectsource.cc b/src/google/protobuf/util/internal/protostream_objectsource.cc
new file mode 100644
index 0000000..034d616
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectsource.cc
@@ -0,0 +1,1045 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+
+#include <utility>
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/wire_format.h>
+#include <google/protobuf/wire_format_lite.h>
+#include <google/protobuf/util/internal/field_mask_utility.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/status_macros.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+using util::Status;
+using util::StatusOr;
+namespace error {
+using util::error::Code;
+using util::error::INTERNAL;
+}
+namespace converter {
+
+using google::protobuf::Descriptor;
+using google::protobuf::EnumValueDescriptor;
+using google::protobuf::FieldDescriptor;
+using google::protobuf::internal::WireFormat;
+using google::protobuf::internal::WireFormatLite;
+using util::Status;
+using util::StatusOr;
+
+namespace {
+// Finds a field with the given number. NULL if none found.
+const google::protobuf::Field* FindFieldByNumber(
+    const google::protobuf::Type& type, int number);
+
+// Returns true if the field is packable.
+bool IsPackable(const google::protobuf::Field& field);
+
+// Finds an enum value with the given number. NULL if none found.
+const google::protobuf::EnumValue* FindEnumValueByNumber(
+    const google::protobuf::Enum& tech_enum, int number);
+
+// Utility function to format nanos.
+const string FormatNanos(uint32 nanos);
+}  // namespace
+
+
+ProtoStreamObjectSource::ProtoStreamObjectSource(
+    google::protobuf::io::CodedInputStream* stream, TypeResolver* type_resolver,
+    const google::protobuf::Type& type)
+    : stream_(stream),
+      typeinfo_(TypeInfo::NewTypeInfo(type_resolver)),
+      own_typeinfo_(true),
+      type_(type) {
+  GOOGLE_LOG_IF(DFATAL, stream == NULL) << "Input stream is NULL.";
+}
+
+ProtoStreamObjectSource::ProtoStreamObjectSource(
+    google::protobuf::io::CodedInputStream* stream, const TypeInfo* typeinfo,
+    const google::protobuf::Type& type)
+    : stream_(stream), typeinfo_(typeinfo), own_typeinfo_(false), type_(type) {
+  GOOGLE_LOG_IF(DFATAL, stream == NULL) << "Input stream is NULL.";
+}
+
+ProtoStreamObjectSource::~ProtoStreamObjectSource() {
+  if (own_typeinfo_) {
+    delete typeinfo_;
+  }
+}
+
+Status ProtoStreamObjectSource::NamedWriteTo(StringPiece name,
+                                             ObjectWriter* ow) const {
+  return WriteMessage(type_, name, 0, true, ow);
+}
+
+const google::protobuf::Field* ProtoStreamObjectSource::FindAndVerifyField(
+    const google::protobuf::Type& type, uint32 tag) const {
+  // Lookup the new field in the type by tag number.
+  const google::protobuf::Field* field = FindFieldByNumber(type, tag >> 3);
+  // Verify if the field corresponds to the wire type in tag.
+  // If there is any discrepancy, mark the field as not found.
+  if (field != NULL) {
+    WireFormatLite::WireType expected_type =
+        WireFormatLite::WireTypeForFieldType(
+            static_cast<WireFormatLite::FieldType>(field->kind()));
+    WireFormatLite::WireType actual_type = WireFormatLite::GetTagWireType(tag);
+    if (actual_type != expected_type &&
+        (!IsPackable(*field) ||
+         actual_type != WireFormatLite::WIRETYPE_LENGTH_DELIMITED)) {
+      field = NULL;
+    }
+  }
+  return field;
+}
+
+Status ProtoStreamObjectSource::WriteMessage(const google::protobuf::Type& type,
+                                             StringPiece name,
+                                             const uint32 end_tag,
+                                             bool include_start_and_end,
+                                             ObjectWriter* ow) const {
+
+    const TypeRenderer* type_renderer = FindTypeRenderer(type.name());
+    if (type_renderer != NULL) {
+      return (*type_renderer)(this, type, name, ow);
+    }
+
+  const google::protobuf::Field* field = NULL;
+  string field_name;
+  // last_tag set to dummy value that is different from tag.
+  uint32 tag = stream_->ReadTag(), last_tag = tag + 1;
+
+  if (include_start_and_end) {
+    ow->StartObject(name);
+  }
+  while (tag != end_tag) {
+    if (tag != last_tag) {  // Update field only if tag is changed.
+      last_tag = tag;
+      field = FindAndVerifyField(type, tag);
+      if (field != NULL) {
+        field_name = field->json_name();
+      }
+    }
+    if (field == NULL) {
+      // If we didn't find a field, skip this unknown tag.
+      // TODO(wpoon): Check return boolean value.
+      WireFormat::SkipField(stream_, tag, NULL);
+      tag = stream_->ReadTag();
+      continue;
+    }
+
+    if (field->cardinality() ==
+        google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+      bool check_maps = true;
+
+      if (check_maps && IsMap(*field)) {
+        ow->StartObject(field_name);
+        ASSIGN_OR_RETURN(tag, RenderMap(field, field_name, tag, ow));
+        ow->EndObject();
+      } else {
+        ASSIGN_OR_RETURN(tag, RenderList(field, field_name, tag, ow));
+      }
+    } else {
+      // Render the field.
+      RETURN_IF_ERROR(RenderField(field, field_name, ow));
+      tag = stream_->ReadTag();
+    }
+  }
+  if (include_start_and_end) {
+    ow->EndObject();
+  }
+  return Status::OK;
+}
+
+StatusOr<uint32> ProtoStreamObjectSource::RenderList(
+    const google::protobuf::Field* field, StringPiece name, uint32 list_tag,
+    ObjectWriter* ow) const {
+  uint32 tag_to_return = 0;
+  ow->StartList(name);
+  if (IsPackable(*field) &&
+      list_tag ==
+          WireFormatLite::MakeTag(field->number(),
+                                  WireFormatLite::WIRETYPE_LENGTH_DELIMITED)) {
+    RETURN_IF_ERROR(RenderPacked(field, ow));
+    // Since packed fields have a single tag, read another tag from stream to
+    // return.
+    tag_to_return = stream_->ReadTag();
+  } else {
+    do {
+      RETURN_IF_ERROR(RenderField(field, "", ow));
+    } while ((tag_to_return = stream_->ReadTag()) == list_tag);
+  }
+  ow->EndList();
+  return tag_to_return;
+}
+
+StatusOr<uint32> ProtoStreamObjectSource::RenderMap(
+    const google::protobuf::Field* field, StringPiece name, uint32 list_tag,
+    ObjectWriter* ow) const {
+  const google::protobuf::Type* field_type =
+      typeinfo_->GetTypeByTypeUrl(field->type_url());
+  uint32 tag_to_return = 0;
+  do {
+    // Render map entry message type.
+    uint32 buffer32;
+    stream_->ReadVarint32(&buffer32);  // message length
+    int old_limit = stream_->PushLimit(buffer32);
+    string map_key;
+    for (uint32 tag = stream_->ReadTag(); tag != 0; tag = stream_->ReadTag()) {
+      const google::protobuf::Field* field =
+          FindAndVerifyField(*field_type, tag);
+      if (field == NULL) {
+        WireFormat::SkipField(stream_, tag, NULL);
+        continue;
+      }
+      // Map field numbers are key = 1 and value = 2
+      if (field->number() == 1) {
+        map_key = ReadFieldValueAsString(*field);
+      } else if (field->number() == 2) {
+        if (map_key.empty()) {
+          return Status(util::error::INTERNAL, "Map key must be non-empty");
+        }
+        RETURN_IF_ERROR(RenderField(field, map_key, ow));
+      }
+    }
+    stream_->PopLimit(old_limit);
+  } while ((tag_to_return = stream_->ReadTag()) == list_tag);
+  return tag_to_return;
+}
+
+Status ProtoStreamObjectSource::RenderPacked(
+    const google::protobuf::Field* field, ObjectWriter* ow) const {
+  uint32 length;
+  stream_->ReadVarint32(&length);
+  int old_limit = stream_->PushLimit(length);
+  while (stream_->BytesUntilLimit() > 0) {
+    RETURN_IF_ERROR(RenderField(field, StringPiece(), ow));
+  }
+  stream_->PopLimit(old_limit);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderTimestamp(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  pair<int64, int32> p = os->ReadSecondsAndNanos(type);
+  int64 seconds = p.first;
+  int32 nanos = p.second;
+  if (seconds > kMaxSeconds || seconds < kMinSeconds) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Timestamp seconds exceeds limit for field: ", field_name));
+  }
+
+  if (nanos < 0 || nanos >= kNanosPerSecond) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Timestamp nanos exceeds limit for field: ", field_name));
+  }
+
+  ow->RenderString(field_name,
+                   ::google::protobuf::internal::FormatTime(seconds, nanos));
+
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderDuration(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  pair<int64, int32> p = os->ReadSecondsAndNanos(type);
+  int64 seconds = p.first;
+  int32 nanos = p.second;
+  if (seconds > kMaxSeconds || seconds < kMinSeconds) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Duration seconds exceeds limit for field: ", field_name));
+  }
+
+  if (nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
+    return Status(
+        util::error::INTERNAL,
+        StrCat("Duration nanos exceeds limit for field: ", field_name));
+  }
+
+  string sign = "";
+  if (seconds < 0) {
+    if (nanos > 0) {
+      return Status(util::error::INTERNAL,
+                    StrCat("Duration nanos is non-negative, but seconds is "
+                           "negative for field: ",
+                           field_name));
+    }
+    sign = "-";
+    seconds = -seconds;
+    nanos = -nanos;
+  } else if (seconds == 0 && nanos < 0) {
+    sign = "-";
+    nanos = -nanos;
+  }
+  string formatted_duration = StringPrintf("%s%lld%ss", sign.c_str(), seconds,
+                                           FormatNanos(nanos).c_str());
+  ow->RenderString(field_name, formatted_duration);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderDouble(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // default value of Double wrapper value
+  if (tag != 0) {
+    os->stream_->ReadLittleEndian64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderDouble(field_name, bit_cast<double>(buffer64));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderFloat(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32 = 0;  // default value of Float wrapper value
+  if (tag != 0) {
+    os->stream_->ReadLittleEndian32(&buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderFloat(field_name, bit_cast<float>(buffer32));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderInt64(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // default value of Int64 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderUInt64(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // default value of UInt64 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderInt32(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32 = 0;  // default value of Int32 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderUInt32(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32 = 0;  // default value of UInt32 wrapper value
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderBool(const ProtoStreamObjectSource* os,
+                                           const google::protobuf::Type& type,
+                                           StringPiece field_name,
+                                           ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint64 buffer64 = 0;  // results in 'false' value as default, which is the
+                        // default value of Bool wrapper
+  if (tag != 0) {
+    os->stream_->ReadVarint64(&buffer64);
+    os->stream_->ReadTag();
+  }
+  ow->RenderBool(field_name, buffer64 != 0);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderString(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32;
+  string str;  // default value of empty for String wrapper
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);  // string size.
+    os->stream_->ReadString(&str, buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderString(field_name, str);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderBytes(const ProtoStreamObjectSource* os,
+                                            const google::protobuf::Type& type,
+                                            StringPiece field_name,
+                                            ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+  uint32 buffer32;
+  string str;
+  if (tag != 0) {
+    os->stream_->ReadVarint32(&buffer32);
+    os->stream_->ReadString(&str, buffer32);
+    os->stream_->ReadTag();
+  }
+  ow->RenderBytes(field_name, str);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderStruct(const ProtoStreamObjectSource* os,
+                                             const google::protobuf::Type& type,
+                                             StringPiece field_name,
+                                             ObjectWriter* ow) {
+  const google::protobuf::Field* field = NULL;
+  uint32 tag = os->stream_->ReadTag();
+  ow->StartObject(field_name);
+  while (tag != 0) {
+    field = os->FindAndVerifyField(type, tag);
+    // google.protobuf.Struct has only one field that is a map. Hence we use
+    // RenderMap to render that field.
+    if (os->IsMap(*field)) {
+      ASSIGN_OR_RETURN(tag, os->RenderMap(field, field_name, tag, ow));
+    }
+  }
+  ow->EndObject();
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderStructValue(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  const google::protobuf::Field* field = NULL;
+  for (uint32 tag = os->stream_->ReadTag(); tag != 0;
+       tag = os->stream_->ReadTag()) {
+    field = os->FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(os->stream_, tag, NULL);
+      continue;
+    }
+    RETURN_IF_ERROR(os->RenderField(field, field_name, ow));
+  }
+  return Status::OK;
+}
+
+// TODO(skarvaje): Avoid code duplication of for loops and SkipField logic.
+Status ProtoStreamObjectSource::RenderStructListValue(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  uint32 tag = os->stream_->ReadTag();
+
+  // Render empty list when we find empty ListValue message.
+  if (tag == 0) {
+    ow->StartList(field_name);
+    ow->EndList();
+    return Status::OK;
+  }
+
+  while (tag != 0) {
+    const google::protobuf::Field* field = os->FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(os->stream_, tag, NULL);
+      tag = os->stream_->ReadTag();
+      continue;
+    }
+    ASSIGN_OR_RETURN(tag, os->RenderList(field, field_name, tag, ow));
+  }
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderAny(const ProtoStreamObjectSource* os,
+                                          const google::protobuf::Type& type,
+                                          StringPiece field_name,
+                                          ObjectWriter* ow) {
+  // An Any is of the form { string type_url = 1; bytes value = 2; }
+  uint32 tag;
+  string type_url;
+  string value;
+
+  // First read out the type_url and value from the proto stream
+  for (tag = os->stream_->ReadTag(); tag != 0; tag = os->stream_->ReadTag()) {
+    const google::protobuf::Field* field = os->FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(os->stream_, tag, NULL);
+      continue;
+    }
+    // 'type_url' has field number of 1 and 'value' has field number 2
+    // //google/protobuf/any.proto
+    if (field->number() == 1) {
+      // read type_url
+      uint32 type_url_size;
+      os->stream_->ReadVarint32(&type_url_size);
+      os->stream_->ReadString(&type_url, type_url_size);
+    } else if (field->number() == 2) {
+      // read value
+      uint32 value_size;
+      os->stream_->ReadVarint32(&value_size);
+      os->stream_->ReadString(&value, value_size);
+    }
+  }
+
+  // If there is no value, we don't lookup the type, we just output it (if
+  // present). If both type and value are empty we output an empty object.
+  if (value.empty()) {
+    ow->StartObject(field_name);
+    if (!type_url.empty()) {
+      ow->RenderString("@type", type_url);
+    }
+    ow->EndObject();
+    return util::Status::OK;
+  }
+
+  // If there is a value but no type, we cannot render it, so report an error.
+  if (type_url.empty()) {
+    // TODO(sven): Add an external message once those are ready.
+    return util::Status(util::error::INTERNAL,
+                        "Invalid Any, the type_url is missing.");
+  }
+
+  util::StatusOr<const google::protobuf::Type*> resolved_type =
+      os->typeinfo_->ResolveTypeUrl(type_url);
+
+  if (!resolved_type.ok()) {
+    // Convert into an internal error, since this means the backend gave us
+    // an invalid response (missing or invalid type information).
+    return util::Status(util::error::INTERNAL,
+                        resolved_type.status().error_message());
+  }
+  // nested_type cannot be null at this time.
+  const google::protobuf::Type* nested_type = resolved_type.ValueOrDie();
+
+  google::protobuf::io::ArrayInputStream zero_copy_stream(value.data(), value.size());
+  google::protobuf::io::CodedInputStream in_stream(&zero_copy_stream);
+  // We know the type so we can render it. Recursively parse the nested stream
+  // using a nested ProtoStreamObjectSource using our nested type information.
+  ProtoStreamObjectSource nested_os(&in_stream, os->typeinfo_, *nested_type);
+
+  // We manually call start and end object here so we can inject the @type.
+  ow->StartObject(field_name);
+  ow->RenderString("@type", type_url);
+  util::Status result =
+      nested_os.WriteMessage(nested_os.type_, "value", 0, false, ow);
+  ow->EndObject();
+  return result;
+}
+
+Status ProtoStreamObjectSource::RenderFieldMask(
+    const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+    StringPiece field_name, ObjectWriter* ow) {
+  string combined;
+  uint32 buffer32;
+  uint32 paths_field_tag = 0;
+  for (uint32 tag = os->stream_->ReadTag(); tag != 0;
+       tag = os->stream_->ReadTag()) {
+    if (paths_field_tag == 0) {
+      const google::protobuf::Field* field = os->FindAndVerifyField(type, tag);
+      if (field != NULL && field->number() == 1 &&
+          field->name() == "paths") {
+        paths_field_tag = tag;
+      }
+    }
+    if (paths_field_tag != tag) {
+      return util::Status(util::error::INTERNAL,
+                          "Invalid FieldMask, unexpected field.");
+    }
+    string str;
+    os->stream_->ReadVarint32(&buffer32);  // string size.
+    os->stream_->ReadString(&str, buffer32);
+    if (!combined.empty()) {
+      combined.append(",");
+    }
+    combined.append(ConvertFieldMaskPath(str, &ToCamelCase));
+  }
+  ow->RenderString(field_name, combined);
+  return Status::OK;
+}
+
+
+hash_map<string, ProtoStreamObjectSource::TypeRenderer>*
+    ProtoStreamObjectSource::renderers_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(source_renderers_init_);
+
+void ProtoStreamObjectSource::InitRendererMap() {
+  renderers_ = new hash_map<string, ProtoStreamObjectSource::TypeRenderer>();
+  (*renderers_)["google.protobuf.Timestamp"] =
+      &ProtoStreamObjectSource::RenderTimestamp;
+  (*renderers_)["google.protobuf.Duration"] =
+      &ProtoStreamObjectSource::RenderDuration;
+  (*renderers_)["google.protobuf.DoubleValue"] =
+      &ProtoStreamObjectSource::RenderDouble;
+  (*renderers_)["google.protobuf.FloatValue"] =
+      &ProtoStreamObjectSource::RenderFloat;
+  (*renderers_)["google.protobuf.Int64Value"] =
+      &ProtoStreamObjectSource::RenderInt64;
+  (*renderers_)["google.protobuf.UInt64Value"] =
+      &ProtoStreamObjectSource::RenderUInt64;
+  (*renderers_)["google.protobuf.Int32Value"] =
+      &ProtoStreamObjectSource::RenderInt32;
+  (*renderers_)["google.protobuf.UInt32Value"] =
+      &ProtoStreamObjectSource::RenderUInt32;
+  (*renderers_)["google.protobuf.BoolValue"] =
+      &ProtoStreamObjectSource::RenderBool;
+  (*renderers_)["google.protobuf.StringValue"] =
+      &ProtoStreamObjectSource::RenderString;
+  (*renderers_)["google.protobuf.BytesValue"] =
+      &ProtoStreamObjectSource::RenderBytes;
+  (*renderers_)["google.protobuf.Any"] = &ProtoStreamObjectSource::RenderAny;
+  (*renderers_)["google.protobuf.Struct"] =
+      &ProtoStreamObjectSource::RenderStruct;
+  (*renderers_)["google.protobuf.Value"] =
+      &ProtoStreamObjectSource::RenderStructValue;
+  (*renderers_)["google.protobuf.ListValue"] =
+      &ProtoStreamObjectSource::RenderStructListValue;
+  (*renderers_)["google.protobuf.FieldMask"] =
+      &ProtoStreamObjectSource::RenderFieldMask;
+  ::google::protobuf::internal::OnShutdown(&DeleteRendererMap);
+}
+
+void ProtoStreamObjectSource::DeleteRendererMap() {
+  delete ProtoStreamObjectSource::renderers_;
+  renderers_ = NULL;
+}
+
+// static
+ProtoStreamObjectSource::TypeRenderer*
+ProtoStreamObjectSource::FindTypeRenderer(const string& type_url) {
+  ::google::protobuf::GoogleOnceInit(&source_renderers_init_, &InitRendererMap);
+  return FindOrNull(*renderers_, type_url);
+}
+
+Status ProtoStreamObjectSource::RenderField(
+    const google::protobuf::Field* field, StringPiece field_name,
+    ObjectWriter* ow) const {
+  // Short-circuit message types as it tends to call WriteMessage recursively
+  // and ends up using a lot of stack space. Keep the stack usage of this
+  // message small in order to preserve stack space and not crash.
+  if (field->kind() == google::protobuf::Field_Kind_TYPE_MESSAGE) {
+    uint32 buffer32;
+    stream_->ReadVarint32(&buffer32);  // message length
+    int old_limit = stream_->PushLimit(buffer32);
+    // Get the nested message type for this field.
+    const google::protobuf::Type* type =
+        typeinfo_->GetTypeByTypeUrl(field->type_url());
+    if (type == NULL) {
+      return Status(util::error::INTERNAL,
+                    StrCat("Invalid configuration. Could not find the type: ",
+                           field->type_url()));
+    }
+
+    // Short-circuit any special type rendering to save call-stack space.
+    const TypeRenderer* type_renderer = FindTypeRenderer(type->name());
+
+    bool use_type_renderer = type_renderer != NULL;
+
+    if (use_type_renderer) {
+      RETURN_IF_ERROR((*type_renderer)(this, *type, field_name, ow));
+    } else {
+      RETURN_IF_ERROR(WriteMessage(*type, field_name, 0, true, ow));
+    }
+    if (!stream_->ConsumedEntireMessage()) {
+      return Status(util::error::INVALID_ARGUMENT,
+                    "Nested protocol message not parsed in its entirety.");
+    }
+    stream_->PopLimit(old_limit);
+  } else {
+    // Render all other non-message types.
+    return RenderNonMessageField(field, field_name, ow);
+  }
+  return Status::OK;
+}
+
+Status ProtoStreamObjectSource::RenderNonMessageField(
+    const google::protobuf::Field* field, StringPiece field_name,
+    ObjectWriter* ow) const {
+  // Temporary buffers of different types.
+  uint32 buffer32;
+  uint64 buffer64;
+  string strbuffer;
+  switch (field->kind()) {
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderBool(field_name, buffer64 != 0);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      stream_->ReadVarint32(&buffer32);
+      ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      stream_->ReadVarint32(&buffer32);
+      ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      stream_->ReadVarint32(&buffer32);
+      ow->RenderInt32(field_name, WireFormatLite::ZigZagDecode32(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      stream_->ReadVarint64(&buffer64);
+      ow->RenderInt64(field_name, WireFormatLite::ZigZagDecode64(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      stream_->ReadLittleEndian32(&buffer32);
+      ow->RenderInt32(field_name, bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      stream_->ReadLittleEndian64(&buffer64);
+      ow->RenderInt64(field_name, bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      stream_->ReadLittleEndian32(&buffer32);
+      ow->RenderUint32(field_name, bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      stream_->ReadLittleEndian64(&buffer64);
+      ow->RenderUint64(field_name, bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      stream_->ReadLittleEndian32(&buffer32);
+      ow->RenderFloat(field_name, bit_cast<float>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      stream_->ReadLittleEndian64(&buffer64);
+      ow->RenderDouble(field_name, bit_cast<double>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      stream_->ReadVarint32(&buffer32);
+
+      // If the field represents an explicit NULL value, render null.
+      if (field->type_url() == kStructNullValueTypeUrl) {
+        ow->RenderNull(field_name);
+        break;
+      }
+
+      // Get the nested enum type for this field.
+      // TODO(skarvaje): Avoid string manipulation. Find ways to speed this
+      // up.
+      const google::protobuf::Enum* en =
+          typeinfo_->GetEnumByTypeUrl(field->type_url());
+      // Lookup the name of the enum, and render that. Skips unknown enums.
+      if (en != NULL) {
+        const google::protobuf::EnumValue* enum_value =
+            FindEnumValueByNumber(*en, buffer32);
+        if (enum_value != NULL) {
+          ow->RenderString(field_name, enum_value->name());
+        }
+      } else {
+        GOOGLE_LOG(INFO) << "Unknown enum skipped: " << field->type_url();
+      }
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      stream_->ReadVarint32(&buffer32);  // string size.
+      stream_->ReadString(&strbuffer, buffer32);
+      ow->RenderString(field_name, strbuffer);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      stream_->ReadVarint32(&buffer32);  // bytes size.
+      stream_->ReadString(&strbuffer, buffer32);
+      ow->RenderBytes(field_name, strbuffer);
+      break;
+    }
+    default:
+      break;
+  }
+  return Status::OK;
+}
+
+// TODO(skarvaje): Fix this to avoid code duplication.
+const string ProtoStreamObjectSource::ReadFieldValueAsString(
+    const google::protobuf::Field& field) const {
+  string result;
+  switch (field.kind()) {
+    case google::protobuf::Field_Kind_TYPE_BOOL: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = buffer64 != 0 ? "true" : "false";
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      result = SimpleItoa(bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_INT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = SimpleItoa(bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      result = SimpleItoa(bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_UINT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = SimpleItoa(bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT32: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      result = SimpleItoa(WireFormatLite::ZigZagDecode32(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SINT64: {
+      uint64 buffer64;
+      stream_->ReadVarint64(&buffer64);
+      result = SimpleItoa(WireFormatLite::ZigZagDecode64(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED32: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      result = SimpleItoa(bit_cast<int32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_SFIXED64: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      result = SimpleItoa(bit_cast<int64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED32: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      result = SimpleItoa(bit_cast<uint32>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FIXED64: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      result = SimpleItoa(bit_cast<uint64>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_FLOAT: {
+      uint32 buffer32;
+      stream_->ReadLittleEndian32(&buffer32);
+      result = SimpleFtoa(bit_cast<float>(buffer32));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_DOUBLE: {
+      uint64 buffer64;
+      stream_->ReadLittleEndian64(&buffer64);
+      result = SimpleDtoa(bit_cast<double>(buffer64));
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_ENUM: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);
+      // Get the nested enum type for this field.
+      // TODO(skarvaje): Avoid string manipulation. Find ways to speed this
+      // up.
+      const google::protobuf::Enum* en =
+          typeinfo_->GetEnumByTypeUrl(field.type_url());
+      // Lookup the name of the enum, and render that. Skips unknown enums.
+      if (en != NULL) {
+        const google::protobuf::EnumValue* enum_value =
+            FindEnumValueByNumber(*en, buffer32);
+        if (enum_value != NULL) {
+          result = enum_value->name();
+        }
+      }
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_STRING: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);  // string size.
+      stream_->ReadString(&result, buffer32);
+      break;
+    }
+    case google::protobuf::Field_Kind_TYPE_BYTES: {
+      uint32 buffer32;
+      stream_->ReadVarint32(&buffer32);  // bytes size.
+      stream_->ReadString(&result, buffer32);
+      break;
+    }
+    default:
+      break;
+  }
+  return result;
+}
+
+// Field is a map if it is a repeated message and it has an option "map_type".
+// TODO(skarvaje): Consider pre-computing the IsMap() into Field directly.
+bool ProtoStreamObjectSource::IsMap(
+    const google::protobuf::Field& field) const {
+  const google::protobuf::Type* field_type =
+      typeinfo_->GetTypeByTypeUrl(field.type_url());
+
+  // TODO(xiaofeng): Unify option names.
+  return field.kind() == google::protobuf::Field_Kind_TYPE_MESSAGE &&
+         (GetBoolOptionOrDefault(field_type->options(),
+                                 "google.protobuf.MessageOptions.map_entry", false) ||
+          GetBoolOptionOrDefault(field_type->options(), "map_entry", false));
+}
+
+std::pair<int64, int32> ProtoStreamObjectSource::ReadSecondsAndNanos(
+    const google::protobuf::Type& type) const {
+  uint64 seconds = 0;
+  uint32 nanos = 0;
+  uint32 tag = 0;
+  int64 signed_seconds = 0;
+  int32 signed_nanos = 0;
+
+  for (tag = stream_->ReadTag(); tag != 0; tag = stream_->ReadTag()) {
+    const google::protobuf::Field* field = FindAndVerifyField(type, tag);
+    if (field == NULL) {
+      WireFormat::SkipField(stream_, tag, NULL);
+      continue;
+    }
+    // 'seconds' has field number of 1 and 'nanos' has field number 2
+    // //google/protobuf/timestamp.proto & duration.proto
+    if (field->number() == 1) {
+      // read seconds
+      stream_->ReadVarint64(&seconds);
+      signed_seconds = bit_cast<int64>(seconds);
+    } else if (field->number() == 2) {
+      // read nanos
+      stream_->ReadVarint32(&nanos);
+      signed_nanos = bit_cast<int32>(nanos);
+    }
+  }
+  return std::pair<int64, int32>(signed_seconds, signed_nanos);
+}
+
+namespace {
+// TODO(skarvaje): Speed this up by not doing a linear scan.
+const google::protobuf::Field* FindFieldByNumber(
+    const google::protobuf::Type& type, int number) {
+  for (int i = 0; i < type.fields_size(); ++i) {
+    if (type.fields(i).number() == number) {
+      return &type.fields(i);
+    }
+  }
+  return NULL;
+}
+
+// TODO(skarvaje): Replace FieldDescriptor by implementing IsTypePackable()
+// using tech Field.
+bool IsPackable(const google::protobuf::Field& field) {
+  return field.cardinality() ==
+             google::protobuf::Field_Cardinality_CARDINALITY_REPEATED &&
+         google::protobuf::FieldDescriptor::IsTypePackable(
+             static_cast<google::protobuf::FieldDescriptor::Type>(field.kind()));
+}
+
+// TODO(skarvaje): Speed this up by not doing a linear scan.
+const google::protobuf::EnumValue* FindEnumValueByNumber(
+    const google::protobuf::Enum& tech_enum, int number) {
+  for (int i = 0; i < tech_enum.enumvalue_size(); ++i) {
+    const google::protobuf::EnumValue& ev = tech_enum.enumvalue(i);
+    if (ev.number() == number) {
+      return &ev;
+    }
+  }
+  return NULL;
+}
+
+// TODO(skarvaje): Look into optimizing this by not doing computation on
+// double.
+const string FormatNanos(uint32 nanos) {
+  const char* format =
+      (nanos % 1000 != 0) ? "%.9f" : (nanos % 1000000 != 0) ? "%.6f" : "%.3f";
+  string formatted =
+      StringPrintf(format, static_cast<double>(nanos) / kNanosPerSecond);
+  // remove the leading 0 before decimal.
+  return formatted.substr(1);
+}
+}  // namespace
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/protostream_objectsource.h b/src/google/protobuf/util/internal/protostream_objectsource.h
new file mode 100644
index 0000000..78defa1
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectsource.h
@@ -0,0 +1,248 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTSOURCE_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTSOURCE_H__
+
+#include <functional>
+#include <google/protobuf/stubs/hash.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/util/internal/object_source.h>
+#include <google/protobuf/util/internal/object_writer.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+class Field;
+class Type;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class TypeInfo;
+
+// An ObjectSource that can parse a stream of bytes as a protocol buffer.
+// Its WriteTo() method can be given an ObjectWriter.
+// This implementation uses a google.protobuf.Type for tag and name lookup.
+// The field names are converted into lower camel-case when writing to the
+// ObjectWriter.
+//
+// Sample usage: (suppose input is: string proto)
+//   ArrayInputStream arr_stream(proto.data(), proto.size());
+//   CodedInputStream in_stream(&arr_stream);
+//   ProtoStreamObjectSource os(&in_stream, /*ServiceTypeInfo*/ typeinfo,
+//                              <your message google::protobuf::Type>);
+//
+//   Status status = os.WriteTo(<some ObjectWriter>);
+class LIBPROTOBUF_EXPORT ProtoStreamObjectSource : public ObjectSource {
+ public:
+  ProtoStreamObjectSource(google::protobuf::io::CodedInputStream* stream,
+                          TypeResolver* type_resolver,
+                          const google::protobuf::Type& type);
+
+  virtual ~ProtoStreamObjectSource();
+
+  virtual util::Status NamedWriteTo(StringPiece name, ObjectWriter* ow) const;
+
+ protected:
+  // Writes a proto2 Message to the ObjectWriter. When the given end_tag is
+  // found this method will complete, allowing it to be used for parsing both
+  // nested messages (end with 0) and nested groups (end with group end tag).
+  // The include_start_and_end parameter allows this method to be called when
+  // already inside of an object, and skip calling StartObject and EndObject.
+  virtual util::Status WriteMessage(const google::protobuf::Type& descriptor,
+                                      StringPiece name, const uint32 end_tag,
+                                      bool include_start_and_end,
+                                      ObjectWriter* ow) const;
+
+ private:
+  ProtoStreamObjectSource(google::protobuf::io::CodedInputStream* stream,
+                          const TypeInfo* typeinfo,
+                          const google::protobuf::Type& type);
+  // Function that renders a well known type with a modified behavior.
+  typedef util::Status (*TypeRenderer)(const ProtoStreamObjectSource*,
+                                         const google::protobuf::Type&,
+                                         StringPiece, ObjectWriter*);
+
+  // Looks up a field and verify its consistency with wire type in tag.
+  const google::protobuf::Field* FindAndVerifyField(
+      const google::protobuf::Type& type, uint32 tag) const;
+
+  // TODO(skarvaje): Mark these methods as non-const as they modify internal
+  // state (stream_).
+  //
+  // Renders a repeating field (packed or unpacked).
+  // Returns the next tag after reading all sequential repeating elements. The
+  // caller should use this tag before reading more tags from the stream.
+  util::StatusOr<uint32> RenderList(const google::protobuf::Field* field,
+                                      StringPiece name, uint32 list_tag,
+                                      ObjectWriter* ow) const;
+  // Renders a NWP map.
+  // Returns the next tag after reading all map entries. The caller should use
+  // this tag before reading more tags from the stream.
+  util::StatusOr<uint32> RenderMap(const google::protobuf::Field* field,
+                                     StringPiece name, uint32 list_tag,
+                                     ObjectWriter* ow) const;
+
+  // Renders a packed repeating field. A packed field is stored as:
+  // {tag length item1 item2 item3} instead of the less efficient
+  // {tag item1 tag item2 tag item3}.
+  util::Status RenderPacked(const google::protobuf::Field* field,
+                              ObjectWriter* ow) const;
+
+  // Renders a google.protobuf.Timestamp value to ObjectWriter
+  static util::Status RenderTimestamp(const ProtoStreamObjectSource* os,
+                                        const google::protobuf::Type& type,
+                                        StringPiece name, ObjectWriter* ow);
+
+  // Renders a google.protobuf.Duration value to ObjectWriter
+  static util::Status RenderDuration(const ProtoStreamObjectSource* os,
+                                       const google::protobuf::Type& type,
+                                       StringPiece name, ObjectWriter* ow);
+
+  // Following RenderTYPE functions render well known types in
+  // google/protobuf/wrappers.proto corresponding to TYPE.
+  static util::Status RenderDouble(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderFloat(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+  static util::Status RenderInt64(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+  static util::Status RenderUInt64(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderInt32(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+  static util::Status RenderUInt32(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderBool(const ProtoStreamObjectSource* os,
+                                   const google::protobuf::Type& type,
+                                   StringPiece name, ObjectWriter* ow);
+  static util::Status RenderString(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+  static util::Status RenderBytes(const ProtoStreamObjectSource* os,
+                                    const google::protobuf::Type& type,
+                                    StringPiece name, ObjectWriter* ow);
+
+  // Renders a google.protobuf.Struct to ObjectWriter.
+  static util::Status RenderStruct(const ProtoStreamObjectSource* os,
+                                     const google::protobuf::Type& type,
+                                     StringPiece name, ObjectWriter* ow);
+
+  // Helper to render google.protobuf.Struct's Value fields to ObjectWriter.
+  static util::Status RenderStructValue(const ProtoStreamObjectSource* os,
+                                          const google::protobuf::Type& type,
+                                          StringPiece name, ObjectWriter* ow);
+
+  // Helper to render google.protobuf.Struct's ListValue fields to ObjectWriter.
+  static util::Status RenderStructListValue(
+      const ProtoStreamObjectSource* os, const google::protobuf::Type& type,
+      StringPiece name, ObjectWriter* ow);
+
+  // Render the "Any" type.
+  static util::Status RenderAny(const ProtoStreamObjectSource* os,
+                                  const google::protobuf::Type& type,
+                                  StringPiece name, ObjectWriter* ow);
+
+  // Render the "FieldMask" type.
+  static util::Status RenderFieldMask(const ProtoStreamObjectSource* os,
+                                        const google::protobuf::Type& type,
+                                        StringPiece name, ObjectWriter* ow);
+
+  static hash_map<string, TypeRenderer>* renderers_;
+  static void InitRendererMap();
+  static void DeleteRendererMap();
+  static TypeRenderer* FindTypeRenderer(const string& type_url);
+
+  // Renders a field value to the ObjectWriter.
+  util::Status RenderField(const google::protobuf::Field* field,
+                             StringPiece field_name, ObjectWriter* ow) const;
+
+  // Same as above but renders all non-message field types. Callers don't call
+  // this function directly. They just use RenderField.
+  util::Status RenderNonMessageField(const google::protobuf::Field* field,
+                                       StringPiece field_name,
+                                       ObjectWriter* ow) const;
+
+
+  // Reads field value according to Field spec in 'field' and returns the read
+  // value as string. This only works for primitive datatypes (no message
+  // types).
+  const string ReadFieldValueAsString(
+      const google::protobuf::Field& field) const;
+
+  // Utility function to detect proto maps. The 'field' MUST be repeated.
+  bool IsMap(const google::protobuf::Field& field) const;
+
+  // Utility to read int64 and int32 values from a message type in stream_.
+  // Used for reading google.protobuf.Timestamp and Duration messages.
+  std::pair<int64, int32> ReadSecondsAndNanos(
+      const google::protobuf::Type& type) const;
+
+  // Input stream to read from. Ownership rests with the caller.
+  google::protobuf::io::CodedInputStream* stream_;
+
+  // Type information for all the types used in the descriptor. Used to find
+  // google::protobuf::Type of nested messages/enums.
+  const TypeInfo* typeinfo_;
+  // Whether this class owns the typeinfo_ object. If true the typeinfo_ object
+  // should be deleted in the destructor.
+  bool own_typeinfo_;
+
+  // google::protobuf::Type of the message source.
+  const google::protobuf::Type& type_;
+
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoStreamObjectSource);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTSOURCE_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectsource_test.cc b/src/google/protobuf/util/internal/protostream_objectsource_test.cc
new file mode 100644
index 0000000..561f676
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectsource_test.cc
@@ -0,0 +1,830 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <sstream>
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/any.pb.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/expecting_objectwriter.h>
+#include <google/protobuf/util/internal/testdata/books.pb.h>
+#include <google/protobuf/util/internal/testdata/field_mask.pb.h>
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/util/internal/testdata/anys.pb.h>
+#include <google/protobuf/util/internal/testdata/maps.pb.h>
+#include <google/protobuf/util/internal/testdata/struct.pb.h>
+#include <gtest/gtest.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::Descriptor;
+using google::protobuf::DescriptorPool;
+using google::protobuf::FileDescriptorProto;
+using google::protobuf::Message;
+using google::protobuf::io::ArrayInputStream;
+using google::protobuf::io::CodedInputStream;
+using util::Status;
+using google::protobuf::testing::Author;
+using google::protobuf::testing::BadAuthor;
+using google::protobuf::testing::BadNestedBook;
+using google::protobuf::testing::Book;
+using google::protobuf::testing::Book_Label;
+using google::protobuf::testing::NestedBook;
+using google::protobuf::testing::PackedPrimitive;
+using google::protobuf::testing::Primitive;
+using google::protobuf::testing::more_author;
+using google::protobuf::testing::maps::MapOut;
+using google::protobuf::testing::anys::AnyOut;
+using google::protobuf::testing::anys::AnyM;
+using google::protobuf::testing::FieldMaskTest;
+using google::protobuf::testing::NestedFieldMask;
+using google::protobuf::testing::structs::StructType;
+using ::testing::_;
+
+
+namespace {
+string GetTypeUrl(const Descriptor* descriptor) {
+  return string(kTypeServiceBaseUrl) + "/" + descriptor->full_name();
+}
+}  // namespace
+
+class ProtostreamObjectSourceTest
+    : public ::testing::TestWithParam<testing::TypeInfoSource> {
+ protected:
+  ProtostreamObjectSourceTest() : helper_(GetParam()), mock_(), ow_(&mock_) {
+    helper_.ResetTypeInfo(Book::descriptor());
+  }
+
+  virtual ~ProtostreamObjectSourceTest() {}
+
+  void DoTest(const Message& msg, const Descriptor* descriptor) {
+    Status status = ExecuteTest(msg, descriptor);
+    EXPECT_EQ(Status::OK, status);
+  }
+
+  Status ExecuteTest(const Message& msg, const Descriptor* descriptor) {
+    ostringstream oss;
+    msg.SerializePartialToOstream(&oss);
+    string proto = oss.str();
+    ArrayInputStream arr_stream(proto.data(), proto.size());
+    CodedInputStream in_stream(&arr_stream);
+
+    google::protobuf::scoped_ptr<ProtoStreamObjectSource> os(
+        helper_.NewProtoSource(&in_stream, GetTypeUrl(descriptor)));
+    return os->WriteTo(&mock_);
+  }
+
+  void PrepareExpectingObjectWriterForRepeatedPrimitive() {
+    ow_.StartObject("")
+        ->StartList("repFix32")
+        ->RenderUint32("", bit_cast<uint32>(3201))
+        ->RenderUint32("", bit_cast<uint32>(0))
+        ->RenderUint32("", bit_cast<uint32>(3202))
+        ->EndList()
+        ->StartList("repU32")
+        ->RenderUint32("", bit_cast<uint32>(3203))
+        ->RenderUint32("", bit_cast<uint32>(0))
+        ->EndList()
+        ->StartList("repI32")
+        ->RenderInt32("", 0)
+        ->RenderInt32("", 3204)
+        ->RenderInt32("", 3205)
+        ->EndList()
+        ->StartList("repSf32")
+        ->RenderInt32("", 3206)
+        ->RenderInt32("", 0)
+        ->EndList()
+        ->StartList("repS32")
+        ->RenderInt32("", 0)
+        ->RenderInt32("", 3207)
+        ->RenderInt32("", 3208)
+        ->EndList()
+        ->StartList("repFix64")
+        ->RenderUint64("", bit_cast<uint64>(6401LL))
+        ->RenderUint64("", bit_cast<uint64>(0LL))
+        ->EndList()
+        ->StartList("repU64")
+        ->RenderUint64("", bit_cast<uint64>(0LL))
+        ->RenderUint64("", bit_cast<uint64>(6402LL))
+        ->RenderUint64("", bit_cast<uint64>(6403LL))
+        ->EndList()
+        ->StartList("repI64")
+        ->RenderInt64("", 6404L)
+        ->RenderInt64("", 0L)
+        ->EndList()
+        ->StartList("repSf64")
+        ->RenderInt64("", 0L)
+        ->RenderInt64("", 6405L)
+        ->RenderInt64("", 6406L)
+        ->EndList()
+        ->StartList("repS64")
+        ->RenderInt64("", 6407L)
+        ->RenderInt64("", 0L)
+        ->EndList()
+        ->StartList("repFloat")
+        ->RenderFloat("", 0.0f)
+        ->RenderFloat("", 32.1f)
+        ->RenderFloat("", 32.2f)
+        ->EndList()
+        ->StartList("repDouble")
+        ->RenderDouble("", 64.1L)
+        ->RenderDouble("", 0.0L)
+        ->EndList()
+        ->StartList("repBool")
+        ->RenderBool("", true)
+        ->RenderBool("", false)
+        ->EndList()
+        ->EndObject();
+  }
+
+  Primitive PrepareRepeatedPrimitive() {
+    Primitive primitive;
+    primitive.add_rep_fix32(3201);
+    primitive.add_rep_fix32(0);
+    primitive.add_rep_fix32(3202);
+    primitive.add_rep_u32(3203);
+    primitive.add_rep_u32(0);
+    primitive.add_rep_i32(0);
+    primitive.add_rep_i32(3204);
+    primitive.add_rep_i32(3205);
+    primitive.add_rep_sf32(3206);
+    primitive.add_rep_sf32(0);
+    primitive.add_rep_s32(0);
+    primitive.add_rep_s32(3207);
+    primitive.add_rep_s32(3208);
+    primitive.add_rep_fix64(6401L);
+    primitive.add_rep_fix64(0L);
+    primitive.add_rep_u64(0L);
+    primitive.add_rep_u64(6402L);
+    primitive.add_rep_u64(6403L);
+    primitive.add_rep_i64(6404L);
+    primitive.add_rep_i64(0L);
+    primitive.add_rep_sf64(0L);
+    primitive.add_rep_sf64(6405L);
+    primitive.add_rep_sf64(6406L);
+    primitive.add_rep_s64(6407L);
+    primitive.add_rep_s64(0L);
+    primitive.add_rep_float(0.0f);
+    primitive.add_rep_float(32.1f);
+    primitive.add_rep_float(32.2f);
+    primitive.add_rep_double(64.1L);
+    primitive.add_rep_double(0.0);
+    primitive.add_rep_bool(true);
+    primitive.add_rep_bool(false);
+
+    PrepareExpectingObjectWriterForRepeatedPrimitive();
+    return primitive;
+  }
+
+  PackedPrimitive PreparePackedPrimitive() {
+    PackedPrimitive primitive;
+    primitive.add_rep_fix32(3201);
+    primitive.add_rep_fix32(0);
+    primitive.add_rep_fix32(3202);
+    primitive.add_rep_u32(3203);
+    primitive.add_rep_u32(0);
+    primitive.add_rep_i32(0);
+    primitive.add_rep_i32(3204);
+    primitive.add_rep_i32(3205);
+    primitive.add_rep_sf32(3206);
+    primitive.add_rep_sf32(0);
+    primitive.add_rep_s32(0);
+    primitive.add_rep_s32(3207);
+    primitive.add_rep_s32(3208);
+    primitive.add_rep_fix64(6401L);
+    primitive.add_rep_fix64(0L);
+    primitive.add_rep_u64(0L);
+    primitive.add_rep_u64(6402L);
+    primitive.add_rep_u64(6403L);
+    primitive.add_rep_i64(6404L);
+    primitive.add_rep_i64(0L);
+    primitive.add_rep_sf64(0L);
+    primitive.add_rep_sf64(6405L);
+    primitive.add_rep_sf64(6406L);
+    primitive.add_rep_s64(6407L);
+    primitive.add_rep_s64(0L);
+    primitive.add_rep_float(0.0f);
+    primitive.add_rep_float(32.1f);
+    primitive.add_rep_float(32.2f);
+    primitive.add_rep_double(64.1L);
+    primitive.add_rep_double(0.0);
+    primitive.add_rep_bool(true);
+    primitive.add_rep_bool(false);
+
+    PrepareExpectingObjectWriterForRepeatedPrimitive();
+    return primitive;
+  }
+
+  testing::TypeInfoTestHelper helper_;
+
+  ::testing::NiceMock<MockObjectWriter> mock_;
+  ExpectingObjectWriter ow_;
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtostreamObjectSourceTest, EmptyMessage) {
+  Book empty;
+  ow_.StartObject("")->EndObject();
+  DoTest(empty, Book::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, Primitives) {
+  Primitive primitive;
+  primitive.set_fix32(3201);
+  primitive.set_u32(3202);
+  primitive.set_i32(3203);
+  primitive.set_sf32(3204);
+  primitive.set_s32(3205);
+  primitive.set_fix64(6401L);
+  primitive.set_u64(6402L);
+  primitive.set_i64(6403L);
+  primitive.set_sf64(6404L);
+  primitive.set_s64(6405L);
+  primitive.set_str("String Value");
+  primitive.set_bytes("Some Bytes");
+  primitive.set_float_(32.1f);
+  primitive.set_double_(64.1L);
+  primitive.set_bool_(true);
+
+  ow_.StartObject("")
+      ->RenderUint32("fix32", bit_cast<uint32>(3201))
+      ->RenderUint32("u32", bit_cast<uint32>(3202))
+      ->RenderInt32("i32", 3203)
+      ->RenderInt32("sf32", 3204)
+      ->RenderInt32("s32", 3205)
+      ->RenderUint64("fix64", bit_cast<uint64>(6401LL))
+      ->RenderUint64("u64", bit_cast<uint64>(6402LL))
+      ->RenderInt64("i64", 6403L)
+      ->RenderInt64("sf64", 6404L)
+      ->RenderInt64("s64", 6405L)
+      ->RenderString("str", "String Value")
+      ->RenderBytes("bytes", "Some Bytes")
+      ->RenderFloat("float", 32.1f)
+      ->RenderDouble("double", 64.1L)
+      ->RenderBool("bool", true)
+      ->EndObject();
+  DoTest(primitive, Primitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, RepeatingPrimitives) {
+  Primitive primitive = PrepareRepeatedPrimitive();
+  primitive.add_rep_str("String One");
+  primitive.add_rep_str("String Two");
+  primitive.add_rep_bytes("Some Bytes");
+
+  ow_.StartList("repStr")
+      ->RenderString("", "String One")
+      ->RenderString("", "String Two")
+      ->EndList()
+      ->StartList("repBytes")
+      ->RenderBytes("", "Some Bytes")
+      ->EndList();
+  DoTest(primitive, Primitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, CustomJsonName) {
+  Author author;
+  author.set_id(12345);
+
+  ow_.StartObject("")->RenderUint64("@id", 12345)->EndObject();
+  DoTest(author, Author::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, NestedMessage) {
+  Author* author = new Author();
+  author->set_name("Tolstoy");
+  Book book;
+  book.set_title("My Book");
+  book.set_allocated_author(author);
+
+  ow_.StartObject("")
+      ->RenderString("title", "My Book")
+      ->StartObject("author")
+      ->RenderString("name", "Tolstoy")
+      ->EndObject()
+      ->EndObject();
+  DoTest(book, Book::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, RepeatingField) {
+  Author author;
+  author.set_alive(false);
+  author.set_name("john");
+  author.add_pseudonym("phil");
+  author.add_pseudonym("bob");
+
+  ow_.StartObject("")
+      ->RenderBool("alive", false)
+      ->RenderString("name", "john")
+      ->StartList("pseudonym")
+      ->RenderString("", "phil")
+      ->RenderString("", "bob")
+      ->EndList()
+      ->EndObject();
+  DoTest(author, Author::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, PackedRepeatingFields) {
+  DoTest(PreparePackedPrimitive(), PackedPrimitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, NonPackedPackableFieldsActuallyPacked) {
+  // Protostream is packed, but parse with non-packed Primitive.
+  DoTest(PreparePackedPrimitive(), Primitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, PackedPackableFieldNotActuallyPacked) {
+  // Protostream is not packed, but parse with PackedPrimitive.
+  DoTest(PrepareRepeatedPrimitive(), PackedPrimitive::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, BadAuthor) {
+  Author author;
+  author.set_alive(false);
+  author.set_name("john");
+  author.set_id(1234L);
+  author.add_pseudonym("phil");
+  author.add_pseudonym("bob");
+
+  ow_.StartObject("")
+      ->StartList("alive")
+      ->RenderBool("", false)
+      ->EndList()
+      ->StartList("name")
+      ->RenderUint64("", static_cast<uint64>('j'))
+      ->RenderUint64("", static_cast<uint64>('o'))
+      ->RenderUint64("", static_cast<uint64>('h'))
+      ->RenderUint64("", static_cast<uint64>('n'))
+      ->EndList()
+      ->RenderString("pseudonym", "phil")
+      ->RenderString("pseudonym", "bob")
+      ->EndObject();
+  // Protostream created with Author, but parsed with BadAuthor.
+  DoTest(author, BadAuthor::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, NestedBookToBadNestedBook) {
+  Book* book = new Book();
+  book->set_length(250);
+  book->set_published(2014L);
+  NestedBook nested;
+  nested.set_allocated_book(book);
+
+  ow_.StartObject("")
+      ->StartList("book")
+      ->RenderUint32("", 24)  // tag for field length (3 << 3)
+      ->RenderUint32("", 250)
+      ->RenderUint32("", 32)  // tag for field published (4 << 3)
+      ->RenderUint32("", 2014)
+      ->EndList()
+      ->EndObject();
+  // Protostream created with NestedBook, but parsed with BadNestedBook.
+  DoTest(nested, BadNestedBook::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest, BadNestedBookToNestedBook) {
+  BadNestedBook nested;
+  nested.add_book(1);
+  nested.add_book(2);
+  nested.add_book(3);
+  nested.add_book(4);
+  nested.add_book(5);
+  nested.add_book(6);
+  nested.add_book(7);
+
+  ow_.StartObject("")->StartObject("book")->EndObject()->EndObject();
+  // Protostream created with BadNestedBook, but parsed with NestedBook.
+  DoTest(nested, NestedBook::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceTest,
+       LongRepeatedListDoesNotBreakIntoMultipleJsonLists) {
+  Book book;
+
+  int repeat = 10000;
+  for (int i = 0; i < repeat; ++i) {
+    Book_Label* label = book.add_labels();
+    label->set_key(StrCat("i", i));
+    label->set_value(StrCat("v", i));
+  }
+
+  // Make sure StartList and EndList are called exactly once (see b/18227499 for
+  // problems when this doesn't happen)
+  EXPECT_CALL(mock_, StartList(_)).Times(1);
+  EXPECT_CALL(mock_, EndList()).Times(1);
+
+  DoTest(book, Book::descriptor());
+}
+
+class ProtostreamObjectSourceMapsTest : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceMapsTest() {
+    helper_.ResetTypeInfo(MapOut::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceMapsTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// Tests JSON map.
+//
+// This is the example expected output.
+// {
+//   "map1": {
+//     "key1": {
+//       "foo": "foovalue"
+//     },
+//     "key2": {
+//       "foo": "barvalue"
+//     }
+//   },
+//   "map2": {
+//     "nestedself": {
+//       "map1": {
+//         "nested_key1": {
+//           "foo": "nested_foo"
+//         }
+//       },
+//       "bar": "nested_bar_string"
+//     }
+//   },
+//   "map3": {
+//     "111": "one one one"
+//   },
+//   "bar": "top bar"
+// }
+TEST_P(ProtostreamObjectSourceMapsTest, MapsTest) {
+  MapOut out;
+  (*out.mutable_map1())["key1"].set_foo("foovalue");
+  (*out.mutable_map1())["key2"].set_foo("barvalue");
+
+  MapOut* nested_value = &(*out.mutable_map2())["nestedself"];
+  (*nested_value->mutable_map1())["nested_key1"].set_foo("nested_foo");
+  nested_value->set_bar("nested_bar_string");
+
+  (*out.mutable_map3())[111] = "one one one";
+
+  out.set_bar("top bar");
+
+  ow_.StartObject("")
+      ->StartObject("map1")
+      ->StartObject("key1")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->StartObject("key2")
+      ->RenderString("foo", "barvalue")
+      ->EndObject()
+      ->StartObject("map2")
+      ->StartObject("nestedself")
+      ->StartObject("map1")
+      ->StartObject("nested_key1")
+      ->RenderString("foo", "nested_foo")
+      ->EndObject()
+      ->EndObject()
+      ->RenderString("bar", "nested_bar_string")
+      ->EndObject()
+      ->EndObject()
+      ->StartObject("map3")
+      ->RenderString("111", "one one one")
+      ->EndObject()
+      ->EndObject()
+      ->RenderString("bar", "top bar")
+      ->EndObject();
+
+  DoTest(out, MapOut::descriptor());
+}
+
+class ProtostreamObjectSourceAnysTest : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceAnysTest() {
+    helper_.ResetTypeInfo(AnyOut::descriptor(),
+                          google::protobuf::Any::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceAnysTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// Tests JSON any support.
+//
+// This is the example expected output.
+// {
+//   "any": {
+//     "@type": "type.googleapis.com/google.protobuf.testing.anys.AnyM"
+//     "foo": "foovalue"
+//   }
+// }
+TEST_P(ProtostreamObjectSourceAnysTest, BasicAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->PackFrom(m);
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, RecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  nested_any.set_value(m.SerializeAsString());
+
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, DoubleRecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any second_nested_any;
+  second_nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  second_nested_any.set_value(m.SerializeAsString());
+  nested_any.set_value(second_nested_any.SerializeAsString());
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, EmptyAnyOutputsEmptyObject) {
+  AnyOut out;
+  out.mutable_any();
+
+  ow_.StartObject("")->StartObject("any")->EndObject()->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, EmptyWithTypeAndNoValueOutputsType) {
+  AnyOut out;
+  out.mutable_any()->set_type_url("foo.googleapis.com/my.Type");
+
+  ow_.StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "foo.googleapis.com/my.Type")
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, AnyOut::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, MissingTypeUrlError) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->set_value(m.SerializeAsString());
+
+  // We start the "AnyOut" part and then fail when we hit the Any object.
+  ow_.StartObject("");
+
+  Status status = ExecuteTest(out, AnyOut::descriptor());
+  EXPECT_EQ(util::error::INTERNAL, status.error_code());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, UnknownTypeServiceError) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("foo.googleapis.com/my.own.Type");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->set_value(m.SerializeAsString());
+
+  // We start the "AnyOut" part and then fail when we hit the Any object.
+  ow_.StartObject("");
+
+  Status status = ExecuteTest(out, AnyOut::descriptor());
+  EXPECT_EQ(util::error::INTERNAL, status.error_code());
+}
+
+TEST_P(ProtostreamObjectSourceAnysTest, UnknownTypeError) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/unknown.Type");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  any->set_value(m.SerializeAsString());
+
+  // We start the "AnyOut" part and then fail when we hit the Any object.
+  ow_.StartObject("");
+
+  Status status = ExecuteTest(out, AnyOut::descriptor());
+  EXPECT_EQ(util::error::INTERNAL, status.error_code());
+}
+
+class ProtostreamObjectSourceStructTest : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceStructTest() {
+    helper_.ResetTypeInfo(StructType::descriptor(),
+                          google::protobuf::Struct::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceStructTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// Tests struct
+//
+//  "object": {
+//    "k1": 123,
+//    "k2": true
+//  }
+TEST_P(ProtostreamObjectSourceStructTest, StructRenderSuccess) {
+  StructType out;
+  google::protobuf::Struct* s = out.mutable_object();
+  s->mutable_fields()->operator[]("k1").set_number_value(123);
+  s->mutable_fields()->operator[]("k2").set_bool_value(true);
+
+  ow_.StartObject("")
+      ->StartObject("object")
+      ->RenderDouble("k1", 123)
+      ->RenderBool("k2", true)
+      ->EndObject()
+      ->EndObject();
+
+  DoTest(out, StructType::descriptor());
+}
+
+TEST_P(ProtostreamObjectSourceStructTest, MissingValueSkipsField) {
+  StructType out;
+  google::protobuf::Struct* s = out.mutable_object();
+  s->mutable_fields()->operator[]("k1");
+
+  ow_.StartObject("")->StartObject("object")->EndObject()->EndObject();
+
+  DoTest(out, StructType::descriptor());
+}
+
+class ProtostreamObjectSourceFieldMaskTest
+    : public ProtostreamObjectSourceTest {
+ protected:
+  ProtostreamObjectSourceFieldMaskTest() {
+    helper_.ResetTypeInfo(FieldMaskTest::descriptor(),
+                          google::protobuf::FieldMask::descriptor());
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtostreamObjectSourceFieldMaskTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtostreamObjectSourceFieldMaskTest, FieldMaskRenderSuccess) {
+  FieldMaskTest out;
+  out.set_id("1");
+  out.mutable_single_mask()->add_paths("path1");
+  out.mutable_single_mask()->add_paths("snake_case_path2");
+  ::google::protobuf::FieldMask* mask = out.add_repeated_mask();
+  mask->add_paths("path3");
+  mask = out.add_repeated_mask();
+  mask->add_paths("snake_case_path4");
+  mask->add_paths("path5");
+  NestedFieldMask* nested = out.add_nested_mask();
+  nested->set_data("data");
+  nested->mutable_single_mask()->add_paths("nested.path1");
+  nested->mutable_single_mask()->add_paths("nested_field.snake_case_path2");
+  mask = nested->add_repeated_mask();
+  mask->add_paths("nested_field.path3");
+  mask->add_paths("nested.snake_case_path4");
+  mask = nested->add_repeated_mask();
+  mask->add_paths("nested.path5");
+  mask = nested->add_repeated_mask();
+  mask->add_paths(
+      "snake_case.map_field[\"map_key_should_be_ignored\"].nested_snake_case."
+      "map_field[\"map_key_sho\\\"uld_be_ignored\"]");
+
+  ow_.StartObject("")
+      ->RenderString("id", "1")
+      ->RenderString("singleMask", "path1,snakeCasePath2")
+      ->StartList("repeatedMask")
+      ->RenderString("", "path3")
+      ->RenderString("", "snakeCasePath4,path5")
+      ->EndList()
+      ->StartList("nestedMask")
+      ->StartObject("")
+      ->RenderString("data", "data")
+      ->RenderString("singleMask", "nested.path1,nestedField.snakeCasePath2")
+      ->StartList("repeatedMask")
+      ->RenderString("", "nestedField.path3,nested.snakeCasePath4")
+      ->RenderString("", "nested.path5")
+      ->RenderString("",
+                     "snakeCase.mapField[\"map_key_should_be_ignored\"]."
+                     "nestedSnakeCase.mapField[\"map_key_sho\\\"uld_be_"
+                     "ignored\"]")
+      ->EndList()
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+
+  DoTest(out, FieldMaskTest::descriptor());
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter.cc b/src/google/protobuf/util/internal/protostream_objectwriter.cc
new file mode 100644
index 0000000..786bf0b
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectwriter.cc
@@ -0,0 +1,1133 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+
+#include <functional>
+#include <stack>
+
+#include <google/protobuf/stubs/once.h>
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/wire_format_lite.h>
+#include <google/protobuf/util/internal/field_mask_utility.h>
+#include <google/protobuf/util/internal/object_location_tracker.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::internal::WireFormatLite;
+using util::error::INVALID_ARGUMENT;
+using util::Status;
+using util::StatusOr;
+
+
+ProtoStreamObjectWriter::ProtoStreamObjectWriter(
+    TypeResolver* type_resolver, const google::protobuf::Type& type,
+    strings::ByteSink* output, ErrorListener* listener)
+    : ProtoWriter(type_resolver, type, output, listener),
+      master_type_(type),
+      current_(NULL) {}
+
+ProtoStreamObjectWriter::ProtoStreamObjectWriter(
+    const TypeInfo* typeinfo, const google::protobuf::Type& type,
+    strings::ByteSink* output, ErrorListener* listener)
+    : ProtoWriter(typeinfo, type, output, listener),
+      master_type_(type),
+      current_(NULL) {}
+
+ProtoStreamObjectWriter::~ProtoStreamObjectWriter() {
+  if (current_ == NULL) return;
+  // Cleanup explicitly in order to avoid destructor stack overflow when input
+  // is deeply nested.
+  // Cast to BaseElement to avoid doing additional checks (like missing fields)
+  // during pop().
+  google::protobuf::scoped_ptr<BaseElement> element(
+      static_cast<BaseElement*>(current_.get())->pop<BaseElement>());
+  while (element != NULL) {
+    element.reset(element->pop<BaseElement>());
+  }
+}
+
+namespace {
+// Utility method to split a string representation of Timestamp or Duration and
+// return the parts.
+void SplitSecondsAndNanos(StringPiece input, StringPiece* seconds,
+                          StringPiece* nanos) {
+  size_t idx = input.rfind('.');
+  if (idx != string::npos) {
+    *seconds = input.substr(0, idx);
+    *nanos = input.substr(idx + 1);
+  } else {
+    *seconds = input;
+    *nanos = StringPiece();
+  }
+}
+
+Status GetNanosFromStringPiece(StringPiece s_nanos,
+                               const char* parse_failure_message,
+                               const char* exceeded_limit_message,
+                               int32* nanos) {
+  *nanos = 0;
+
+  // Count the number of leading 0s and consume them.
+  int num_leading_zeros = 0;
+  while (s_nanos.Consume("0")) {
+    num_leading_zeros++;
+  }
+  int32 i_nanos = 0;
+  // 's_nanos' contains fractional seconds -- i.e. 'nanos' is equal to
+  // "0." + s_nanos.ToString() seconds. An int32 is used for the
+  // conversion to 'nanos', rather than a double, so that there is no
+  // loss of precision.
+  if (!s_nanos.empty() && !safe_strto32(s_nanos.ToString(), &i_nanos)) {
+    return Status(INVALID_ARGUMENT, parse_failure_message);
+  }
+  if (i_nanos > kNanosPerSecond || i_nanos < 0) {
+    return Status(INVALID_ARGUMENT, exceeded_limit_message);
+  }
+  // s_nanos should only have digits. No whitespace.
+  if (s_nanos.find_first_not_of("0123456789") != StringPiece::npos) {
+    return Status(INVALID_ARGUMENT, parse_failure_message);
+  }
+
+  if (i_nanos > 0) {
+    // 'scale' is the number of digits to the right of the decimal
+    // point in "0." + s_nanos.ToString()
+    int32 scale = num_leading_zeros + s_nanos.size();
+    // 'conversion' converts i_nanos into nanoseconds.
+    // conversion = kNanosPerSecond / static_cast<int32>(std::pow(10, scale))
+    // For efficiency, we precompute the conversion factor.
+    int32 conversion = 0;
+    switch (scale) {
+      case 1:
+        conversion = 100000000;
+        break;
+      case 2:
+        conversion = 10000000;
+        break;
+      case 3:
+        conversion = 1000000;
+        break;
+      case 4:
+        conversion = 100000;
+        break;
+      case 5:
+        conversion = 10000;
+        break;
+      case 6:
+        conversion = 1000;
+        break;
+      case 7:
+        conversion = 100;
+        break;
+      case 8:
+        conversion = 10;
+        break;
+      case 9:
+        conversion = 1;
+        break;
+      default:
+        return Status(INVALID_ARGUMENT, exceeded_limit_message);
+    }
+    *nanos = i_nanos * conversion;
+  }
+
+  return Status::OK;
+}
+
+}  // namespace
+
+ProtoStreamObjectWriter::AnyWriter::AnyWriter(ProtoStreamObjectWriter* parent)
+    : parent_(parent),
+      ow_(),
+      invalid_(false),
+      data_(),
+      output_(&data_),
+      depth_(0),
+      has_injected_value_message_(false) {}
+
+ProtoStreamObjectWriter::AnyWriter::~AnyWriter() {}
+
+void ProtoStreamObjectWriter::AnyWriter::StartObject(StringPiece name) {
+  ++depth_;
+  // If an object writer is absent, that means we have not called StartAny()
+  // before reaching here. This is an invalid state. StartAny() gets called
+  // whenever we see an "@type" being rendered (see AnyWriter::RenderDataPiece).
+  if (ow_ == NULL) {
+    // Make sure we are not already in an invalid state. This avoids making
+    // multiple unnecessary InvalidValue calls.
+    if (!invalid_) {
+      parent_->InvalidValue("Any",
+                            StrCat("Missing or invalid @type for any field in ",
+                                   parent_->master_type_.name()));
+      invalid_ = true;
+    }
+  } else if (!has_injected_value_message_ || depth_ != 1 || name != "value") {
+    // We don't propagate to ow_ StartObject("value") calls for nested Anys or
+    // Struct at depth 1 as they are nested one level deep with an injected
+    // "value" field.
+    ow_->StartObject(name);
+  }
+}
+
+bool ProtoStreamObjectWriter::AnyWriter::EndObject() {
+  --depth_;
+  // As long as depth_ >= 0, we know we haven't reached the end of Any.
+  // Propagate these EndObject() calls to the contained ow_.  If we are in a
+  // nested Any or Struct type, ignore the second to last EndObject call (depth_
+  // == -1)
+  if (ow_ != NULL && (!has_injected_value_message_ || depth_ >= 0)) {
+    ow_->EndObject();
+  }
+  // A negative depth_ implies that we have reached the end of Any
+  // object. Now we write out its contents.
+  if (depth_ < 0) {
+    WriteAny();
+    return false;
+  }
+  return true;
+}
+
+void ProtoStreamObjectWriter::AnyWriter::StartList(StringPiece name) {
+  ++depth_;
+  // We expect ow_ to be present as this call only makes sense inside an Any.
+  if (ow_ == NULL) {
+    if (!invalid_) {
+      parent_->InvalidValue("Any",
+                            StrCat("Missing or invalid @type for any field in ",
+                                   parent_->master_type_.name()));
+      invalid_ = true;
+    }
+  } else {
+    ow_->StartList(name);
+  }
+}
+
+void ProtoStreamObjectWriter::AnyWriter::EndList() {
+  --depth_;
+  if (depth_ < 0) {
+    GOOGLE_LOG(DFATAL) << "Mismatched EndList found, should not be possible";
+    depth_ = 0;
+  }
+  // We don't write an error on the close, only on the open
+  if (ow_ != NULL) {
+    ow_->EndList();
+  }
+}
+
+void ProtoStreamObjectWriter::AnyWriter::RenderDataPiece(
+    StringPiece name, const DataPiece& value) {
+  // Start an Any only at depth_ 0. Other RenderDataPiece calls with "@type"
+  // should go to the contained ow_ as they indicate nested Anys.
+  if (depth_ == 0 && ow_ == NULL && name == "@type") {
+    StartAny(value);
+  } else if (ow_ == NULL) {
+    if (!invalid_) {
+      parent_->InvalidValue("Any",
+                            StrCat("Missing or invalid @type for any field in ",
+                                   parent_->master_type_.name()));
+      invalid_ = true;
+    }
+  } else {
+    // Check to see if the data needs to be rendered with well-known-type
+    // renderer.
+    const TypeRenderer* type_renderer =
+        FindTypeRenderer(GetFullTypeWithUrl(ow_->master_type_.name()));
+    if (type_renderer) {
+      Status status = (*type_renderer)(ow_.get(), value);
+      if (!status.ok()) ow_->InvalidValue("Any", status.error_message());
+    } else {
+      ow_->RenderDataPiece(name, value);
+    }
+  }
+}
+
+void ProtoStreamObjectWriter::AnyWriter::StartAny(const DataPiece& value) {
+  // Figure out the type url. This is a copy-paste from WriteString but we also
+  // need the value, so we can't just call through to that.
+  if (value.type() == DataPiece::TYPE_STRING) {
+    type_url_ = value.str().ToString();
+  } else {
+    StatusOr<string> s = value.ToString();
+    if (!s.ok()) {
+      parent_->InvalidValue("String", s.status().error_message());
+      invalid_ = true;
+      return;
+    }
+    type_url_ = s.ValueOrDie();
+  }
+  // Resolve the type url, and report an error if we failed to resolve it.
+  StatusOr<const google::protobuf::Type*> resolved_type =
+      parent_->typeinfo()->ResolveTypeUrl(type_url_);
+  if (!resolved_type.ok()) {
+    parent_->InvalidValue("Any", resolved_type.status().error_message());
+    invalid_ = true;
+    return;
+  }
+  // At this point, type is never null.
+  const google::protobuf::Type* type = resolved_type.ValueOrDie();
+
+  // If this is the case of an Any in an Any or Struct in an Any, we need to
+  // expect a StartObject call with "value" while we're at depth_ 0, which we
+  // should ignore (not propagate to our nested object writer). We also need to
+  // ignore the second-to-last EndObject call, and not propagate that either.
+  if (type->name() == kAnyType || type->name() == kStructType) {
+    has_injected_value_message_ = true;
+  }
+
+  // Create our object writer and initialize it with the first StartObject
+  // call.
+  ow_.reset(new ProtoStreamObjectWriter(parent_->typeinfo(), *type, &output_,
+                                        parent_->listener()));
+  ow_->StartObject("");
+}
+
+void ProtoStreamObjectWriter::AnyWriter::WriteAny() {
+  if (ow_ == NULL) {
+    // If we had no object writer, we never got any content, so just return
+    // immediately, which is equivalent to writing an empty Any.
+    return;
+  }
+  // Render the type_url and value fields directly to the stream.
+  // type_url has tag 1 and value has tag 2.
+  WireFormatLite::WriteString(1, type_url_, parent_->stream());
+  if (!data_.empty()) {
+    WireFormatLite::WriteBytes(2, data_, parent_->stream());
+  }
+}
+
+ProtoStreamObjectWriter::Item::Item(ProtoStreamObjectWriter* enclosing,
+                                    ItemType item_type, bool is_placeholder,
+                                    bool is_list)
+    : BaseElement(NULL),
+      ow_(enclosing),
+      any_(),
+      item_type_(item_type),
+      is_placeholder_(is_placeholder),
+      is_list_(is_list) {
+  if (item_type_ == ANY) {
+    any_.reset(new AnyWriter(ow_));
+  }
+}
+
+ProtoStreamObjectWriter::Item::Item(ProtoStreamObjectWriter::Item* parent,
+                                    ItemType item_type, bool is_placeholder,
+                                    bool is_list)
+    : BaseElement(parent),
+      ow_(this->parent()->ow_),
+      any_(),
+      item_type_(item_type),
+      is_placeholder_(is_placeholder),
+      is_list_(is_list) {
+  if (item_type == ANY) {
+    any_.reset(new AnyWriter(ow_));
+  }
+}
+
+bool ProtoStreamObjectWriter::Item::InsertMapKeyIfNotPresent(
+    StringPiece map_key) {
+  return InsertIfNotPresent(&map_keys_, map_key.ToString());
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::StartObject(
+    StringPiece name) {
+  if (invalid_depth() > 0) {
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  // Starting the root message. Create the root Item and return.
+  // ANY message type does not need special handling, just set the ItemType
+  // to ANY.
+  if (current_ == NULL) {
+    ProtoWriter::StartObject(name);
+    current_.reset(new Item(
+        this, master_type_.name() == kAnyType ? Item::ANY : Item::MESSAGE,
+        false, false));
+
+    // If master type is a special type that needs extra values to be written to
+    // stream, we write those values.
+    if (master_type_.name() == kStructType) {
+      // Struct has a map<string, Value> field called "fields".
+      // https://github.com/google/protobuf/blob/master/src/google/protobuf/struct.proto
+      // "fields": [
+      Push("fields", Item::MAP, true, true);
+      return this;
+    }
+
+    if (master_type_.name() == kStructValueType) {
+      // We got a StartObject call with google.protobuf.Value field. The only
+      // object within that type is a struct type. So start a struct.
+      //
+      // The struct field in Value type is named "struct_value"
+      // https://github.com/google/protobuf/blob/master/src/google/protobuf/struct.proto
+      // Also start the map field "fields" within the struct.
+      // "struct_value": {
+      //   "fields": [
+      Push("struct_value", Item::MESSAGE, true, false);
+      Push("fields", Item::MAP, true, true);
+      return this;
+    }
+
+    if (master_type_.name() == kStructListValueType) {
+      InvalidValue(kStructListValueType,
+                   "Cannot start root message with ListValue.");
+    }
+
+    return this;
+  }
+
+  // Send all ANY events to AnyWriter.
+  if (current_->IsAny()) {
+    current_->any()->StartObject(name);
+    return this;
+  }
+
+  // If we are within a map, we render name as keys and send StartObject to the
+  // value field.
+  if (current_->IsMap()) {
+    if (!ValidMapKey(name)) {
+      IncrementInvalidDepth();
+      return this;
+    }
+
+    // Map is a repeated field of message type with a "key" and a "value" field.
+    // https://developers.google.com/protocol-buffers/docs/proto3?hl=en#maps
+    // message MapFieldEntry {
+    //   key_type key = 1;
+    //   value_type value = 2;
+    // }
+    //
+    // repeated MapFieldEntry map_field = N;
+    //
+    // That means, we render the following element within a list (hence no
+    // name):
+    // { "key": "<name>", "value": {
+    Push("", Item::MESSAGE, false, false);
+    ProtoWriter::RenderDataPiece("key", DataPiece(name));
+    Push("value", Item::MESSAGE, true, false);
+
+    // Make sure we are valid so far after starting map fields.
+    if (invalid_depth() > 0) return this;
+
+    // If top of stack is g.p.Struct type, start the struct the map field within
+    // it.
+    if (element() != NULL && IsStruct(*element()->parent_field())) {
+      // Render "fields": [
+      Push("fields", Item::MAP, true, true);
+      return this;
+    }
+
+    // If top of stack is g.p.Value type, start the Struct within it.
+    if (element() != NULL && IsStructValue(*element()->parent_field())) {
+      // Render
+      // "struct_value": {
+      //   "fields": [
+      Push("struct_value", Item::MESSAGE, true, false);
+      Push("fields", Item::MAP, true, true);
+    }
+    return this;
+  }
+
+  const google::protobuf::Field* field = BeginNamed(name, false);
+  if (field == NULL) return this;
+
+  if (IsStruct(*field)) {
+    // Start a struct object.
+    // Render
+    // "<name>": {
+    //   "fields": {
+    Push(name, Item::MESSAGE, false, false);
+    Push("fields", Item::MAP, true, true);
+    return this;
+  }
+
+  if (IsStructValue(*field)) {
+    // We got a StartObject call with google.protobuf.Value field.  The only
+    // object within that type is a struct type. So start a struct.
+    // Render
+    // "<name>": {
+    //   "struct_value": {
+    //     "fields": {
+    Push(name, Item::MESSAGE, false, false);
+    Push("struct_value", Item::MESSAGE, true, false);
+    Push("fields", Item::MAP, true, true);
+    return this;
+  }
+
+  if (IsMap(*field)) {
+    // Begin a map. A map is triggered by a StartObject() call if the current
+    // field has a map type.
+    // A map type is always repeated, hence set is_list to true.
+    // Render
+    // "<name>": [
+    Push(name, Item::MAP, false, true);
+    return this;
+  }
+
+  // A regular message type. Pass it directly to ProtoWriter.
+  // Render
+  // "<name>": {
+  Push(name, IsAny(*field) ? Item::ANY : Item::MESSAGE, false, false);
+  return this;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::EndObject() {
+  if (invalid_depth() > 0) {
+    DecrementInvalidDepth();
+    return this;
+  }
+
+  if (current_ == NULL) return this;
+
+  if (current_->IsAny()) {
+    if (current_->any()->EndObject()) return this;
+  }
+
+  Pop();
+
+  return this;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::StartList(StringPiece name) {
+  if (invalid_depth() > 0) {
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  // Since we cannot have a top-level repeated item in protobuf, the only way
+  // this is valid is if we start a special type google.protobuf.ListValue or
+  // google.protobuf.Value.
+  if (current_ == NULL) {
+    if (!name.empty()) {
+      InvalidName(name, "Root element should not be named.");
+      IncrementInvalidDepth();
+      return this;
+    }
+
+    // If master type is a special type that needs extra values to be written to
+    // stream, we write those values.
+    if (master_type_.name() == kStructValueType) {
+      // We got a StartList with google.protobuf.Value master type. This means
+      // we have to start the "list_value" within google.protobuf.Value.
+      //
+      // See
+      // https://github.com/google/protobuf/blob/master/src/google/protobuf/struct.proto
+      //
+      // Render
+      // "<name>": {
+      //   "list_value": {
+      //     "values": [  // Start this list.
+      ProtoWriter::StartObject(name);
+      current_.reset(new Item(this, Item::MESSAGE, false, false));
+      Push("list_value", Item::MESSAGE, true, false);
+      Push("values", Item::MESSAGE, true, true);
+      return this;
+    }
+
+    if (master_type_.name() == kStructListValueType) {
+      // We got a StartList with google.protobuf.ListValue master type. This
+      // means we have to start the "values" within google.protobuf.ListValue.
+      //
+      // Render
+      // "<name>": {
+      //   "values": [  // Start this list.
+      ProtoWriter::StartObject(name);
+      current_.reset(new Item(this, Item::MESSAGE, false, false));
+      Push("values", Item::MESSAGE, true, true);
+      return this;
+    }
+
+    // Send the event to ProtoWriter so proper errors can be reported.
+    //
+    // Render a regular list:
+    // "<name>": [
+    ProtoWriter::StartList(name);
+    current_.reset(new Item(this, Item::MESSAGE, false, true));
+    return this;
+  }
+
+  if (current_->IsAny()) {
+    current_->any()->StartList(name);
+    return this;
+  }
+
+  // If the top of stack is a map, we are starting a list value within a map.
+  // Since map does not allow repeated values, this can only happen when the map
+  // value is of a special type that renders a list in JSON.  These can be one
+  // of 3 cases:
+  // i. We are rendering a list value within google.protobuf.Struct
+  // ii. We are rendering a list value within google.protobuf.Value
+  // iii. We are rendering a list value with type google.protobuf.ListValue.
+  if (current_->IsMap()) {
+    if (!ValidMapKey(name)) {
+      IncrementInvalidDepth();
+      return this;
+    }
+
+    // Start the repeated map entry object.
+    // Render
+    // { "key": "<name>", "value": {
+    Push("", Item::MESSAGE, false, false);
+    ProtoWriter::RenderDataPiece("key", DataPiece(name));
+    Push("value", Item::MESSAGE, true, false);
+
+    // Make sure we are valid after pushing all above items.
+    if (invalid_depth() > 0) return this;
+
+    // case i and ii above. Start "list_value" field within g.p.Value
+    if (element() != NULL && element()->parent_field() != NULL) {
+      // Render
+      // "list_value": {
+      //   "values": [  // Start this list
+      if (IsStructValue(*element()->parent_field())) {
+        Push("list_value", Item::MESSAGE, true, false);
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
+
+      // Render
+      // "values": [
+      if (IsStructListValue(*element()->parent_field())) {
+        // case iii above. Bind directly to g.p.ListValue
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
+    }
+
+    // Report an error.
+    InvalidValue("Map", StrCat("Cannot have repeated items ('", name,
+                               "') within a map."));
+    return this;
+  }
+
+  // When name is empty and stack is not empty, we are rendering an item within
+  // a list.
+  if (name.empty()) {
+    if (element() != NULL && element()->parent_field() != NULL) {
+      if (IsStructValue(*element()->parent_field())) {
+        // Since it is g.p.Value, we bind directly to the list_value.
+        // Render
+        // {  // g.p.Value item within the list
+        //   "list_value": {
+        //     "values": [
+        Push("", Item::MESSAGE, false, false);
+        Push("list_value", Item::MESSAGE, true, false);
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
+
+      if (IsStructListValue(*element()->parent_field())) {
+        // Since it is g.p.ListValue, we bind to it directly.
+        // Render
+        // {  // g.p.ListValue item within the list
+        //   "values": [
+        Push("", Item::MESSAGE, false, false);
+        Push("values", Item::MESSAGE, true, true);
+        return this;
+      }
+    }
+
+    // Pass the event to underlying ProtoWriter.
+    Push(name, Item::MESSAGE, false, true);
+    return this;
+  }
+
+  // name is not empty
+  const google::protobuf::Field* field = Lookup(name);
+  if (field == NULL) {
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  if (IsStructValue(*field)) {
+    // If g.p.Value is repeated, start that list. Otherwise, start the
+    // "list_value" within it.
+    if (IsRepeated(*field)) {
+      // Render it just like a regular repeated field.
+      // "<name>": [
+      Push(name, Item::MESSAGE, false, true);
+      return this;
+    }
+
+    // Start the "list_value" field.
+    // Render
+    // "<name>": {
+    //   "list_value": {
+    //     "values": [
+    Push(name, Item::MESSAGE, false, false);
+    Push("list_value", Item::MESSAGE, true, false);
+    Push("values", Item::MESSAGE, true, true);
+    return this;
+  }
+
+  if (IsStructListValue(*field)) {
+    // If g.p.ListValue is repeated, start that list. Otherwise, start the
+    // "values" within it.
+    if (IsRepeated(*field)) {
+      // Render it just like a regular repeated field.
+      // "<name>": [
+      Push(name, Item::MESSAGE, false, true);
+      return this;
+    }
+
+    // Start the "values" field within g.p.ListValue.
+    // Render
+    // "<name>": {
+    //   "values": [
+    Push(name, Item::MESSAGE, false, false);
+    Push("values", Item::MESSAGE, true, true);
+    return this;
+  }
+
+  // If we are here, the field should be repeated. Report an error otherwise.
+  if (!IsRepeated(*field)) {
+    IncrementInvalidDepth();
+    InvalidName(name, "Proto field is not repeating, cannot start list.");
+    return this;
+  }
+
+  if (IsMap(*field)) {
+    InvalidValue("Map",
+                 StrCat("Cannot bind a list to map for field '", name, "'."));
+    IncrementInvalidDepth();
+    return this;
+  }
+
+  // Pass the event to ProtoWriter.
+  // Render
+  // "<name>": [
+  Push(name, Item::MESSAGE, false, true);
+  return this;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::EndList() {
+  if (invalid_depth() > 0) {
+    DecrementInvalidDepth();
+    return this;
+  }
+
+  if (current_ == NULL) return this;
+
+  if (current_->IsAny()) {
+    current_->any()->EndList();
+    return this;
+  }
+
+  Pop();
+  return this;
+}
+
+Status ProtoStreamObjectWriter::RenderStructValue(ProtoStreamObjectWriter* ow,
+                                                  const DataPiece& data) {
+  string struct_field_name;
+  switch (data.type()) {
+    // Our JSON parser parses numbers as either int64, uint64, or double.
+    case DataPiece::TYPE_INT64:
+    case DataPiece::TYPE_UINT64:
+    case DataPiece::TYPE_DOUBLE: {
+      struct_field_name = "number_value";
+      break;
+    }
+    case DataPiece::TYPE_STRING: {
+      struct_field_name = "string_value";
+      break;
+    }
+    case DataPiece::TYPE_BOOL: {
+      struct_field_name = "bool_value";
+      break;
+    }
+    case DataPiece::TYPE_NULL: {
+      struct_field_name = "null_value";
+      break;
+    }
+    default: {
+      return Status(INVALID_ARGUMENT,
+                    "Invalid struct data type. Only number, string, boolean or "
+                    "null values are supported.");
+    }
+  }
+  ow->ProtoWriter::RenderDataPiece(struct_field_name, data);
+  return Status::OK;
+}
+
+Status ProtoStreamObjectWriter::RenderTimestamp(ProtoStreamObjectWriter* ow,
+                                                const DataPiece& data) {
+  if (data.type() != DataPiece::TYPE_STRING) {
+    return Status(INVALID_ARGUMENT,
+                  StrCat("Invalid data type for timestamp, value is ",
+                         data.ValueAsStringOrDefault("")));
+  }
+
+  StringPiece value(data.str());
+
+  int64 seconds;
+  int32 nanos;
+  if (!::google::protobuf::internal::ParseTime(value.ToString(), &seconds,
+                                               &nanos)) {
+    return Status(INVALID_ARGUMENT, StrCat("Invalid time format: ", value));
+  }
+
+
+  ow->ProtoWriter::RenderDataPiece("seconds", DataPiece(seconds));
+  ow->ProtoWriter::RenderDataPiece("nanos", DataPiece(nanos));
+  return Status::OK;
+}
+
+static inline util::Status RenderOneFieldPath(ProtoStreamObjectWriter* ow,
+                                                StringPiece path) {
+  ow->ProtoWriter::RenderDataPiece(
+      "paths", DataPiece(ConvertFieldMaskPath(path, &ToSnakeCase)));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectWriter::RenderFieldMask(ProtoStreamObjectWriter* ow,
+                                                const DataPiece& data) {
+  if (data.type() != DataPiece::TYPE_STRING) {
+    return Status(INVALID_ARGUMENT,
+                  StrCat("Invalid data type for field mask, value is ",
+                         data.ValueAsStringOrDefault("")));
+  }
+
+// TODO(tsun): figure out how to do proto descriptor based snake case
+// conversions as much as possible. Because ToSnakeCase sometimes returns the
+// wrong value.
+  google::protobuf::scoped_ptr<ResultCallback1<util::Status, StringPiece> > callback(
+      google::protobuf::internal::NewPermanentCallback(&RenderOneFieldPath, ow));
+  return DecodeCompactFieldMaskPaths(data.str(), callback.get());
+}
+
+Status ProtoStreamObjectWriter::RenderDuration(ProtoStreamObjectWriter* ow,
+                                               const DataPiece& data) {
+  if (data.type() != DataPiece::TYPE_STRING) {
+    return Status(INVALID_ARGUMENT,
+                  StrCat("Invalid data type for duration, value is ",
+                         data.ValueAsStringOrDefault("")));
+  }
+
+  StringPiece value(data.str());
+
+  if (!value.ends_with("s")) {
+    return Status(INVALID_ARGUMENT,
+                  "Illegal duration format; duration must end with 's'");
+  }
+  value = value.substr(0, value.size() - 1);
+  int sign = 1;
+  if (value.starts_with("-")) {
+    sign = -1;
+    value = value.substr(1);
+  }
+
+  StringPiece s_secs, s_nanos;
+  SplitSecondsAndNanos(value, &s_secs, &s_nanos);
+  uint64 unsigned_seconds;
+  if (!safe_strtou64(s_secs, &unsigned_seconds)) {
+    return Status(INVALID_ARGUMENT,
+                  "Invalid duration format, failed to parse seconds");
+  }
+
+  int32 nanos = 0;
+  Status nanos_status = GetNanosFromStringPiece(
+      s_nanos, "Invalid duration format, failed to parse nano seconds",
+      "Duration value exceeds limits", &nanos);
+  if (!nanos_status.ok()) {
+    return nanos_status;
+  }
+  nanos = sign * nanos;
+
+  int64 seconds = sign * unsigned_seconds;
+  if (seconds > kMaxSeconds || seconds < kMinSeconds ||
+      nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
+    return Status(INVALID_ARGUMENT, "Duration value exceeds limits");
+  }
+
+  ow->ProtoWriter::RenderDataPiece("seconds", DataPiece(seconds));
+  ow->ProtoWriter::RenderDataPiece("nanos", DataPiece(nanos));
+  return Status::OK;
+}
+
+Status ProtoStreamObjectWriter::RenderWrapperType(ProtoStreamObjectWriter* ow,
+                                                  const DataPiece& data) {
+  ow->ProtoWriter::RenderDataPiece("value", data);
+  return Status::OK;
+}
+
+ProtoStreamObjectWriter* ProtoStreamObjectWriter::RenderDataPiece(
+    StringPiece name, const DataPiece& data) {
+  Status status;
+  if (invalid_depth() > 0) return this;
+
+  if (current_ == NULL) {
+    const TypeRenderer* type_renderer =
+        FindTypeRenderer(GetFullTypeWithUrl(master_type_.name()));
+    if (type_renderer == NULL) {
+      InvalidName(name, "Root element must be a message.");
+      return this;
+    }
+    // Render the special type.
+    // "<name>": {
+    //   ... Render special type ...
+    // }
+    ProtoWriter::StartObject(name);
+    status = (*type_renderer)(this, data);
+    if (!status.ok()) {
+      InvalidValue(master_type_.name(),
+                   StrCat("Field '", name, "', ", status.error_message()));
+    }
+    ProtoWriter::EndObject();
+    return this;
+  }
+
+  if (current_->IsAny()) {
+    current_->any()->RenderDataPiece(name, data);
+    return this;
+  }
+
+  const google::protobuf::Field* field = NULL;
+  if (current_->IsMap()) {
+    if (!ValidMapKey(name)) return this;
+
+    // Render an item in repeated map list.
+    // { "key": "<name>", "value":
+    Push("", Item::MESSAGE, false, false);
+    ProtoWriter::RenderDataPiece("key", DataPiece(name));
+    field = Lookup("value");
+    if (field == NULL) {
+      GOOGLE_LOG(DFATAL) << "Map does not have a value field.";
+      return this;
+    }
+
+    const TypeRenderer* type_renderer = FindTypeRenderer(field->type_url());
+    if (type_renderer != NULL) {
+      // Map's value type is a special type. Render it like a message:
+      // "value": {
+      //   ... Render special type ...
+      // }
+      Push("value", Item::MESSAGE, true, false);
+      status = (*type_renderer)(this, data);
+      if (!status.ok()) {
+        InvalidValue(field->type_url(),
+                     StrCat("Field '", name, "', ", status.error_message()));
+      }
+      Pop();
+      return this;
+    }
+
+    // If we are rendering explicit null values and the backend proto field is
+    // not of the google.protobuf.NullType type, we do nothing.
+    if (data.type() == DataPiece::TYPE_NULL &&
+        field->type_url() != kStructNullValueTypeUrl) {
+      return this;
+    }
+
+    // Render the map value as a primitive type.
+    ProtoWriter::RenderDataPiece("value", data);
+    Pop();
+    return this;
+  }
+
+  field = Lookup(name);
+  if (field == NULL) return this;
+
+  // Check if the field is of special type. Render it accordingly if so.
+  const TypeRenderer* type_renderer = FindTypeRenderer(field->type_url());
+  if (type_renderer != NULL) {
+    Push(name, Item::MESSAGE, false, false);
+    status = (*type_renderer)(this, data);
+    if (!status.ok()) {
+      InvalidValue(field->type_url(),
+                   StrCat("Field '", name, "', ", status.error_message()));
+    }
+    Pop();
+    return this;
+  }
+
+  // If we are rendering explicit null values and the backend proto field is
+  // not of the google.protobuf.NullType type, we do nothing.
+  if (data.type() == DataPiece::TYPE_NULL &&
+      field->type_url() != kStructNullValueTypeUrl) {
+    return this;
+  }
+
+  ProtoWriter::RenderDataPiece(name, data);
+  return this;
+}
+
+// Map of functions that are responsible for rendering well known type
+// represented by the key.
+hash_map<string, ProtoStreamObjectWriter::TypeRenderer>*
+    ProtoStreamObjectWriter::renderers_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(writer_renderers_init_);
+
+void ProtoStreamObjectWriter::InitRendererMap() {
+  renderers_ = new hash_map<string, ProtoStreamObjectWriter::TypeRenderer>();
+  (*renderers_)["type.googleapis.com/google.protobuf.Timestamp"] =
+      &ProtoStreamObjectWriter::RenderTimestamp;
+  (*renderers_)["type.googleapis.com/google.protobuf.Duration"] =
+      &ProtoStreamObjectWriter::RenderDuration;
+  (*renderers_)["type.googleapis.com/google.protobuf.FieldMask"] =
+      &ProtoStreamObjectWriter::RenderFieldMask;
+  (*renderers_)["type.googleapis.com/google.protobuf.Double"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Float"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Int64"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.UInt64"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Int32"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.UInt32"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Bool"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.String"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Bytes"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.DoubleValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.FloatValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Int64Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.UInt64Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Int32Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.UInt32Value"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.BoolValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.StringValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.BytesValue"] =
+      &ProtoStreamObjectWriter::RenderWrapperType;
+  (*renderers_)["type.googleapis.com/google.protobuf.Value"] =
+      &ProtoStreamObjectWriter::RenderStructValue;
+  ::google::protobuf::internal::OnShutdown(&DeleteRendererMap);
+}
+
+void ProtoStreamObjectWriter::DeleteRendererMap() {
+  delete ProtoStreamObjectWriter::renderers_;
+  renderers_ = NULL;
+}
+
+ProtoStreamObjectWriter::TypeRenderer*
+ProtoStreamObjectWriter::FindTypeRenderer(const string& type_url) {
+  ::google::protobuf::GoogleOnceInit(&writer_renderers_init_, &InitRendererMap);
+  return FindOrNull(*renderers_, type_url);
+}
+
+bool ProtoStreamObjectWriter::ValidMapKey(StringPiece unnormalized_name) {
+  if (current_ == NULL) return true;
+
+  if (!current_->InsertMapKeyIfNotPresent(unnormalized_name)) {
+    listener()->InvalidName(
+        location(), unnormalized_name,
+        StrCat("Repeated map key: '", unnormalized_name, "' is already set."));
+    return false;
+  }
+
+  return true;
+}
+
+void ProtoStreamObjectWriter::Push(StringPiece name, Item::ItemType item_type,
+                                   bool is_placeholder, bool is_list) {
+  is_list ? ProtoWriter::StartList(name) : ProtoWriter::StartObject(name);
+
+  // invalid_depth == 0 means it is a successful StartObject or StartList.
+  if (invalid_depth() == 0)
+    current_.reset(
+        new Item(current_.release(), item_type, is_placeholder, is_list));
+}
+
+void ProtoStreamObjectWriter::Pop() {
+  // Pop all placeholder items sending StartObject or StartList events to
+  // ProtoWriter according to is_list value.
+  while (current_ != NULL && current_->is_placeholder()) {
+    PopOneElement();
+  }
+  if (current_ != NULL) {
+    PopOneElement();
+  }
+}
+
+void ProtoStreamObjectWriter::PopOneElement() {
+  current_->is_list() ? ProtoWriter::EndList() : ProtoWriter::EndObject();
+  current_.reset(current_->pop<Item>());
+}
+
+bool ProtoStreamObjectWriter::IsMap(const google::protobuf::Field& field) {
+  if (field.type_url().empty() ||
+      field.kind() != google::protobuf::Field_Kind_TYPE_MESSAGE ||
+      field.cardinality() !=
+          google::protobuf::Field_Cardinality_CARDINALITY_REPEATED) {
+    return false;
+  }
+  const google::protobuf::Type* field_type =
+      typeinfo()->GetTypeByTypeUrl(field.type_url());
+
+  // TODO(xiaofeng): Unify option names.
+  return GetBoolOptionOrDefault(field_type->options(),
+                                "google.protobuf.MessageOptions.map_entry", false) ||
+         GetBoolOptionOrDefault(field_type->options(), "map_entry", false);
+}
+
+bool ProtoStreamObjectWriter::IsAny(const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kAnyType;
+}
+
+bool ProtoStreamObjectWriter::IsStruct(const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kStructType;
+}
+
+bool ProtoStreamObjectWriter::IsStructValue(
+    const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kStructValueType;
+}
+
+bool ProtoStreamObjectWriter::IsStructListValue(
+    const google::protobuf::Field& field) {
+  return GetTypeWithoutUrl(field.type_url()) == kStructListValueType;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter.h b/src/google/protobuf/util/internal/protostream_objectwriter.h
new file mode 100644
index 0000000..08ac6e3
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectwriter.h
@@ -0,0 +1,312 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTWRITER_H__
+
+#include <deque>
+#include <google/protobuf/stubs/hash.h>
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/datapiece.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/proto_writer.h>
+#include <google/protobuf/util/internal/structured_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+class CodedOutputStream;
+}  // namespace io
+}  // namespace protobuf
+
+
+namespace protobuf {
+class Type;
+class Field;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+
+class ObjectLocationTracker;
+
+// An ObjectWriter that can write protobuf bytes directly from writer events.
+// This class supports all special types like Struct and Map. It uses
+// the ProtoWriter class to write raw proto bytes.
+//
+// It also supports streaming.
+class LIBPROTOBUF_EXPORT ProtoStreamObjectWriter : public ProtoWriter {
+ public:
+// Constructor. Does not take ownership of any parameter passed in.
+  ProtoStreamObjectWriter(TypeResolver* type_resolver,
+                          const google::protobuf::Type& type,
+                          strings::ByteSink* output, ErrorListener* listener);
+  virtual ~ProtoStreamObjectWriter();
+
+  // ObjectWriter methods.
+  virtual ProtoStreamObjectWriter* StartObject(StringPiece name);
+  virtual ProtoStreamObjectWriter* EndObject();
+  virtual ProtoStreamObjectWriter* StartList(StringPiece name);
+  virtual ProtoStreamObjectWriter* EndList();
+
+  // Renders a DataPiece 'value' into a field whose wire type is determined
+  // from the given field 'name'.
+  virtual ProtoStreamObjectWriter* RenderDataPiece(StringPiece name,
+                                                   const DataPiece& value);
+
+ protected:
+  // Function that renders a well known type with modified behavior.
+  typedef util::Status (*TypeRenderer)(ProtoStreamObjectWriter*,
+                                         const DataPiece&);
+
+  // Handles writing Anys out using nested object writers and the like.
+  class LIBPROTOBUF_EXPORT AnyWriter {
+   public:
+    explicit AnyWriter(ProtoStreamObjectWriter* parent);
+    ~AnyWriter();
+
+    // Passes a StartObject call through to the Any writer.
+    void StartObject(StringPiece name);
+
+    // Passes an EndObject call through to the Any. Returns true if the any
+    // handled the EndObject call, false if the Any is now all done and is no
+    // longer needed.
+    bool EndObject();
+
+    // Passes a StartList call through to the Any writer.
+    void StartList(StringPiece name);
+
+    // Passes an EndList call through to the Any writer.
+    void EndList();
+
+    // Renders a data piece on the any.
+    void RenderDataPiece(StringPiece name, const DataPiece& value);
+
+   private:
+    // Handles starting up the any once we have a type.
+    void StartAny(const DataPiece& value);
+
+    // Writes the Any out to the parent writer in its serialized form.
+    void WriteAny();
+
+    // The parent of this writer, needed for various bits such as type info and
+    // the listeners.
+    ProtoStreamObjectWriter* parent_;
+
+    // The nested object writer, used to write events.
+    google::protobuf::scoped_ptr<ProtoStreamObjectWriter> ow_;
+
+    // The type_url_ that this Any represents.
+    string type_url_;
+
+    // Whether this any is invalid. This allows us to only report an invalid
+    // Any message a single time rather than every time we get a nested field.
+    bool invalid_;
+
+    // The output data and wrapping ByteSink.
+    string data_;
+    strings::StringByteSink output_;
+
+    // The depth within the Any, so we can track when we're done.
+    int depth_;
+
+    // True if the message type contained in Any has a special "value" message
+    // injected. This is true for well-known message types like Any or Struct.
+    bool has_injected_value_message_;
+  };
+
+  // Represents an item in a stack of items used to keep state between
+  // ObjectWrier events.
+  class LIBPROTOBUF_EXPORT Item : public BaseElement {
+   public:
+    // Indicates the type of item.
+    enum ItemType {
+      MESSAGE,  // Simple message
+      MAP,      // Proto3 map type
+      ANY,      // Proto3 Any type
+    };
+
+    // Constructor for the root item.
+    Item(ProtoStreamObjectWriter* enclosing, ItemType item_type,
+         bool is_placeholder, bool is_list);
+
+    // Constructor for a field of a message.
+    Item(Item* parent, ItemType item_type, bool is_placeholder, bool is_list);
+
+    virtual ~Item() {}
+
+    // These functions return true if the element type is corresponding to the
+    // type in function name.
+    bool IsMap() { return item_type_ == MAP; }
+    bool IsAny() { return item_type_ == ANY; }
+
+    AnyWriter* any() const { return any_.get(); }
+
+    virtual Item* parent() const {
+      return static_cast<Item*>(BaseElement::parent());
+    }
+
+    // Inserts map key into hash set if and only if the key did NOT already
+    // exist in hash set.
+    // The hash set (map_keys_) is ONLY used to keep track of map keys.
+    // Return true if insert successfully; returns false if the map key was
+    // already present.
+    bool InsertMapKeyIfNotPresent(StringPiece map_key);
+
+    bool is_placeholder() const { return is_placeholder_; }
+    bool is_list() const { return is_list_; }
+
+   private:
+    // Used for access to variables of the enclosing instance of
+    // ProtoStreamObjectWriter.
+    ProtoStreamObjectWriter* ow_;
+
+    // A writer for Any objects, handles all Any-related nonsense.
+    google::protobuf::scoped_ptr<AnyWriter> any_;
+
+    // The type of this element, see enum for permissible types.
+    ItemType item_type_;
+
+    // Set of map keys already seen for the type_. Used to validate incoming
+    // messages so no map key appears more than once.
+    hash_set<string> map_keys_;
+
+    // Conveys whether this Item is a placeholder or not. Placeholder items are
+    // pushed to stack to account for special types.
+    bool is_placeholder_;
+
+    // Conveys whether this Item is a list or not. This is used to send
+    // StartList or EndList calls to underlying ObjectWriter.
+    bool is_list_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(Item);
+  };
+
+  ProtoStreamObjectWriter(const TypeInfo* typeinfo,
+                          const google::protobuf::Type& type,
+                          strings::ByteSink* output, ErrorListener* listener);
+
+  // Returns true if the field is a map.
+  bool IsMap(const google::protobuf::Field& field);
+
+  // Returns true if the field is an any.
+  bool IsAny(const google::protobuf::Field& field);
+
+  // Returns true if the field is google.protobuf.Struct.
+  bool IsStruct(const google::protobuf::Field& field);
+
+  // Returns true if the field is google.protobuf.Value.
+  bool IsStructValue(const google::protobuf::Field& field);
+
+  // Returns true if the field is google.protobuf.ListValue.
+  bool IsStructListValue(const google::protobuf::Field& field);
+
+  // Renders google.protobuf.Value in struct.proto. It picks the right oneof
+  // type based on value's type.
+  static util::Status RenderStructValue(ProtoStreamObjectWriter* ow,
+                                          const DataPiece& value);
+
+  // Renders google.protobuf.Timestamp value.
+  static util::Status RenderTimestamp(ProtoStreamObjectWriter* ow,
+                                        const DataPiece& value);
+
+  // Renders google.protobuf.FieldMask value.
+  static util::Status RenderFieldMask(ProtoStreamObjectWriter* ow,
+                                        const DataPiece& value);
+
+  // Renders google.protobuf.Duration value.
+  static util::Status RenderDuration(ProtoStreamObjectWriter* ow,
+                                       const DataPiece& value);
+
+  // Renders wrapper message types for primitive types in
+  // google/protobuf/wrappers.proto.
+  static util::Status RenderWrapperType(ProtoStreamObjectWriter* ow,
+                                          const DataPiece& value);
+
+  static void InitRendererMap();
+  static void DeleteRendererMap();
+  static TypeRenderer* FindTypeRenderer(const string& type_url);
+
+  // Returns true if the map key for type_ is not duplicated key.
+  // If map key is duplicated key, this function returns false.
+  // Note that caller should make sure that the current proto element (current_)
+  // is of element type MAP or STRUCT_MAP.
+  // It also calls the appropriate error callback and unnormalzied_name is used
+  // for error string.
+  bool ValidMapKey(StringPiece unnormalized_name);
+
+  // Pushes an item on to the stack. Also calls either StartObject or StartList
+  // on the underlying ObjectWriter depending on whether is_list is false or
+  // not.
+  // is_placeholder conveys whether the item is a placeholder item or not.
+  // Placeholder items are pushed when adding auxillary types' StartObject or
+  // StartList calls.
+  void Push(StringPiece name, Item::ItemType item_type, bool is_placeholder,
+            bool is_list);
+
+  // Pops items from the stack. All placeholder items are popped until a
+  // non-placeholder item is found.
+  void Pop();
+
+  // Pops one element from the stack. Calls EndObject() or EndList() on the
+  // underlying ObjectWriter depending on the value of is_list_.
+  void PopOneElement();
+
+ private:
+  // Helper functions to create the map and find functions responsible for
+  // rendering well known types, keyed by type URL.
+  static hash_map<string, TypeRenderer>* renderers_;
+
+  // Variables for describing the structure of the input tree:
+  // master_type_: descriptor for the whole protobuf message.
+  const google::protobuf::Type& master_type_;
+
+  // The current element, variable for internal state processing.
+  google::protobuf::scoped_ptr<Item> current_;
+
+  GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(ProtoStreamObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_PROTOSTREAM_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/protostream_objectwriter_test.cc b/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
new file mode 100644
index 0000000..5f9ffb9
--- /dev/null
+++ b/src/google/protobuf/util/internal/protostream_objectwriter_test.cc
@@ -0,0 +1,1895 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+
+#include <stddef.h>  // For size_t
+
+#include <google/protobuf/field_mask.pb.h>
+#include <google/protobuf/timestamp.pb.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/message.h>
+#include <google/protobuf/util/internal/mock_error_listener.h>
+#include <google/protobuf/util/internal/testdata/books.pb.h>
+#include <google/protobuf/util/internal/testdata/field_mask.pb.h>
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/message_differencer.h>
+#include <google/protobuf/stubs/bytestream.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/util/internal/testdata/anys.pb.h>
+#include <google/protobuf/util/internal/testdata/maps.pb.h>
+#include <google/protobuf/util/internal/testdata/oneofs.pb.h>
+#include <google/protobuf/util/internal/testdata/struct.pb.h>
+#include <google/protobuf/util/internal/testdata/timestamp_duration.pb.h>
+#include <gtest/gtest.h>
+
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+using google::protobuf::testing::Author;
+using google::protobuf::testing::Book;
+using google::protobuf::testing::Book_Data;
+using google::protobuf::testing::Primitive;
+using google::protobuf::testing::Publisher;
+using google::protobuf::Descriptor;
+using google::protobuf::DescriptorPool;
+using google::protobuf::DynamicMessageFactory;
+using google::protobuf::FileDescriptorProto;
+using google::protobuf::Message;
+using google::protobuf::io::ArrayInputStream;
+using strings::GrowingArrayByteSink;
+using ::testing::_;
+using ::testing::Args;
+using google::protobuf::testing::anys::AnyM;
+using google::protobuf::testing::anys::AnyOut;
+using google::protobuf::testing::oneofs::OneOfsRequest;
+using google::protobuf::testing::FieldMaskTest;
+using google::protobuf::testing::maps::MapIn;
+using google::protobuf::testing::structs::StructType;
+using google::protobuf::testing::timestampduration::TimestampDuration;
+
+
+namespace {
+string GetTypeUrl(const Descriptor* descriptor) {
+  return string(kTypeServiceBaseUrl) + "/" + descriptor->full_name();
+}
+}  // namespace
+
+class BaseProtoStreamObjectWriterTest
+    : public ::testing::TestWithParam<testing::TypeInfoSource> {
+ protected:
+  BaseProtoStreamObjectWriterTest()
+      : helper_(GetParam()),
+        listener_(),
+        output_(new GrowingArrayByteSink(1000)),
+        ow_() {}
+
+  explicit BaseProtoStreamObjectWriterTest(const Descriptor* descriptor)
+      : helper_(GetParam()),
+        listener_(),
+        output_(new GrowingArrayByteSink(1000)),
+        ow_() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(descriptor);
+    ResetTypeInfo(descriptors);
+  }
+
+  explicit BaseProtoStreamObjectWriterTest(
+      vector<const Descriptor*> descriptors)
+      : helper_(GetParam()),
+        listener_(),
+        output_(new GrowingArrayByteSink(1000)),
+        ow_() {
+    ResetTypeInfo(descriptors);
+  }
+
+  void ResetTypeInfo(vector<const Descriptor*> descriptors) {
+    GOOGLE_CHECK(!descriptors.empty()) << "Must have at least one descriptor!";
+    helper_.ResetTypeInfo(descriptors);
+    ow_.reset(helper_.NewProtoWriter(GetTypeUrl(descriptors[0]), output_.get(),
+                                     &listener_));
+  }
+
+  virtual ~BaseProtoStreamObjectWriterTest() {}
+
+  void CheckOutput(const Message& expected, int expected_length) {
+    size_t nbytes;
+    google::protobuf::scoped_array<char> buffer(output_->GetBuffer(&nbytes));
+    if (expected_length >= 0) {
+      EXPECT_EQ(expected_length, nbytes);
+    }
+    string str(buffer.get(), nbytes);
+
+    std::stringbuf str_buf(str, std::ios_base::in);
+    std::istream istream(&str_buf);
+    google::protobuf::scoped_ptr<Message> message(expected.New());
+    message->ParsePartialFromIstream(&istream);
+
+    if (!MessageDifferencer::Equivalent(expected, *message)) {
+      EXPECT_EQ(expected.DebugString(), message->DebugString());
+    }
+  }
+
+  void CheckOutput(const Message& expected) { CheckOutput(expected, -1); }
+
+  const google::protobuf::Type* GetType(const Descriptor* descriptor) {
+    return helper_.GetTypeInfo()->GetTypeByTypeUrl(GetTypeUrl(descriptor));
+  }
+
+  testing::TypeInfoTestHelper helper_;
+  MockErrorListener listener_;
+  google::protobuf::scoped_ptr<GrowingArrayByteSink> output_;
+  google::protobuf::scoped_ptr<ProtoStreamObjectWriter> ow_;
+};
+
+MATCHER_P(HasObjectLocation, expected,
+          "Verifies the expected object location") {
+  string actual;
+#if __cplusplus >= 201103L
+  actual = std::get<0>(arg).ToString();
+#else
+  actual = std::tr1::get<0>(arg).ToString();
+#endif
+  if (actual.compare(expected) == 0) return true;
+  *result_listener << "actual location is: " << actual;
+  return false;
+}
+
+class ProtoStreamObjectWriterTest : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterTest()
+      : BaseProtoStreamObjectWriterTest(Book::descriptor()) {}
+
+  virtual ~ProtoStreamObjectWriterTest() {}
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterTest, EmptyObject) {
+  Book empty;
+  ow_->StartObject("")->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, SimpleObject) {
+  string content("My content");
+
+  Book book;
+  book.set_title("My Title");
+  book.set_length(222);
+  book.set_content(content);
+
+  ow_->StartObject("")
+      ->RenderString("title", "My Title")
+      ->RenderInt32("length", 222)
+      ->RenderBytes("content", content)
+      ->EndObject();
+  CheckOutput(book);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, SimpleMessage) {
+  Book book;
+  book.set_title("Some Book");
+  book.set_length(102);
+  Publisher* publisher = book.mutable_publisher();
+  publisher->set_name("My Publisher");
+  Author* robert = book.mutable_author();
+  robert->set_alive(true);
+  robert->set_name("robert");
+  robert->add_pseudonym("bob");
+  robert->add_pseudonym("bobby");
+  robert->add_friend_()->set_name("john");
+
+  ow_->StartObject("")
+      ->RenderString("title", "Some Book")
+      ->RenderInt32("length", 102)
+      ->StartObject("publisher")
+      ->RenderString("name", "My Publisher")
+      ->EndObject()
+      ->StartObject("author")
+      ->RenderBool("alive", true)
+      ->RenderString("name", "robert")
+      ->StartList("pseudonym")
+      ->RenderString("", "bob")
+      ->RenderString("", "bobby")
+      ->EndList()
+      ->StartList("friend")
+      ->StartObject("")
+      ->RenderString("name", "john")
+      ->EndObject()
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(book);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, CustomJsonName) {
+  Book book;
+  Author* robert = book.mutable_author();
+  robert->set_id(12345);
+  robert->set_name("robert");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderUint64("@id", 12345)
+      ->RenderString("name", "robert")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(book);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, PrimitiveFromStringConversion) {
+  Primitive full;
+  full.set_fix32(101);
+  full.set_u32(102);
+  full.set_i32(-103);
+  full.set_sf32(-104);
+  full.set_s32(-105);
+  full.set_fix64(40000000001L);
+  full.set_u64(40000000002L);
+  full.set_i64(-40000000003L);
+  full.set_sf64(-40000000004L);
+  full.set_s64(-40000000005L);
+  full.set_str("string1");
+  full.set_bytes("Some Bytes");
+  full.set_float_(3.14f);
+  full.set_double_(-4.05L);
+  full.set_bool_(true);
+  full.add_rep_fix32(201);
+  full.add_rep_u32(202);
+  full.add_rep_i32(-203);
+  full.add_rep_sf32(-204);
+  full.add_rep_s32(-205);
+  full.add_rep_fix64(80000000001L);
+  full.add_rep_u64(80000000002L);
+  full.add_rep_i64(-80000000003L);
+  full.add_rep_sf64(-80000000004L);
+  full.add_rep_s64(-80000000005L);
+  full.add_rep_str("string2");
+  full.add_rep_bytes("More Bytes");
+  full.add_rep_float(6.14f);
+  full.add_rep_double(-8.05L);
+  full.add_rep_bool(false);
+
+  ow_.reset(helper_.NewProtoWriter(GetTypeUrl(Primitive::descriptor()),
+                                   output_.get(), &listener_));
+
+  ow_->StartObject("")
+      ->RenderString("fix32", "101")
+      ->RenderString("u32", "102")
+      ->RenderString("i32", "-103")
+      ->RenderString("sf32", "-104")
+      ->RenderString("s32", "-105")
+      ->RenderString("fix64", "40000000001")
+      ->RenderString("u64", "40000000002")
+      ->RenderString("i64", "-40000000003")
+      ->RenderString("sf64", "-40000000004")
+      ->RenderString("s64", "-40000000005")
+      ->RenderString("str", "string1")
+      ->RenderString("bytes", "U29tZSBCeXRlcw==")  // "Some Bytes"
+      ->RenderString("float", "3.14")
+      ->RenderString("double", "-4.05")
+      ->RenderString("bool", "true")
+      ->StartList("rep_fix32")
+      ->RenderString("", "201")
+      ->EndList()
+      ->StartList("rep_u32")
+      ->RenderString("", "202")
+      ->EndList()
+      ->StartList("rep_i32")
+      ->RenderString("", "-203")
+      ->EndList()
+      ->StartList("rep_sf32")
+      ->RenderString("", "-204")
+      ->EndList()
+      ->StartList("rep_s32")
+      ->RenderString("", "-205")
+      ->EndList()
+      ->StartList("rep_fix64")
+      ->RenderString("", "80000000001")
+      ->EndList()
+      ->StartList("rep_u64")
+      ->RenderString("", "80000000002")
+      ->EndList()
+      ->StartList("rep_i64")
+      ->RenderString("", "-80000000003")
+      ->EndList()
+      ->StartList("rep_sf64")
+      ->RenderString("", "-80000000004")
+      ->EndList()
+      ->StartList("rep_s64")
+      ->RenderString("", "-80000000005")
+      ->EndList()
+      ->StartList("rep_str")
+      ->RenderString("", "string2")
+      ->EndList()
+      ->StartList("rep_bytes")
+      ->RenderString("", "TW9yZSBCeXRlcw==")  // "More Bytes"
+      ->EndList()
+      ->StartList("rep_float")
+      ->RenderString("", "6.14")
+      ->EndList()
+      ->StartList("rep_double")
+      ->RenderString("", "-8.05")
+      ->EndList()
+      ->StartList("rep_bool")
+      ->RenderString("", "false")
+      ->EndList()
+      ->EndObject();
+  CheckOutput(full);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, InfinityInputTest) {
+  Primitive full;
+  full.set_double_(std::numeric_limits<double>::infinity());
+  full.set_float_(std::numeric_limits<float>::infinity());
+  full.set_str("-Infinity");
+
+  ow_.reset(helper_.NewProtoWriter(GetTypeUrl(Primitive::descriptor()),
+                                   output_.get(), &listener_));
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_INT32"),
+                                      StringPiece("\"Infinity\"")))
+      .With(Args<0>(HasObjectLocation("i32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"Infinity\"")))
+      .With(Args<0>(HasObjectLocation("u32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_SFIXED64"),
+                                      StringPiece("\"-Infinity\"")))
+      .With(Args<0>(HasObjectLocation("sf64")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_BOOL"),
+                                      StringPiece("\"Infinity\"")))
+      .With(Args<0>(HasObjectLocation("bool")));
+
+  ow_->StartObject("")
+      ->RenderString("double", "Infinity")
+      ->RenderString("float", "Infinity")
+      ->RenderString("i32", "Infinity")
+      ->RenderString("u32", "Infinity")
+      ->RenderString("sf64", "-Infinity")
+      ->RenderString("str", "-Infinity")
+      ->RenderString("bool", "Infinity")
+      ->EndObject();
+  CheckOutput(full);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NaNInputTest) {
+  Primitive full;
+  full.set_double_(std::numeric_limits<double>::quiet_NaN());
+  full.set_float_(std::numeric_limits<float>::quiet_NaN());
+  full.set_str("NaN");
+
+  ow_.reset(helper_.NewProtoWriter(GetTypeUrl(Primitive::descriptor()),
+                                   output_.get(), &listener_));
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_INT32"),
+                                      StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("i32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("u32")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_SFIXED64"),
+                                      StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("sf64")));
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("TYPE_BOOL"), StringPiece("\"NaN\"")))
+      .With(Args<0>(HasObjectLocation("bool")));
+
+  ow_->StartObject("")
+      ->RenderString("double", "NaN")
+      ->RenderString("float", "NaN")
+      ->RenderString("i32", "NaN")
+      ->RenderString("u32", "NaN")
+      ->RenderString("sf64", "NaN")
+      ->RenderString("str", "NaN")
+      ->RenderString("bool", "NaN")
+      ->EndObject();
+
+  CheckOutput(full);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ImplicitPrimitiveList) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+  author->add_pseudonym("first");
+  author->add_pseudonym("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->RenderString("pseudonym", "first")
+      ->RenderString("pseudonym", "second")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest,
+       LastWriteWinsOnNonRepeatedPrimitiveFieldWithDuplicates) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "first")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ExplicitPrimitiveList) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+  author->add_pseudonym("first");
+  author->add_pseudonym("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->StartList("pseudonym")
+      ->RenderString("", "first")
+      ->RenderString("", "second")
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NonRepeatedExplicitPrimitiveList) {
+  Book expected;
+  expected.set_allocated_author(new Author());
+
+  EXPECT_CALL(
+      listener_,
+      InvalidName(
+          _, StringPiece("name"),
+          StringPiece("Proto field is not repeating, cannot start list.")))
+      .With(Args<0>(HasObjectLocation("author")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->StartList("name")
+      ->RenderString("", "first")
+      ->RenderString("", "second")
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ImplicitMessageList) {
+  Book expected;
+  Author* outer = expected.mutable_author();
+  outer->set_name("outer");
+  outer->set_alive(true);
+  Author* first = outer->add_friend_();
+  first->set_name("first");
+  Author* second = outer->add_friend_();
+  second->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "outer")
+      ->RenderBool("alive", true)
+      ->StartObject("friend")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("friend")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest,
+       LastWriteWinsOnNonRepeatedMessageFieldWithDuplicates) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+  Publisher* publisher = expected.mutable_publisher();
+  publisher->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->EndObject()
+      ->StartObject("publisher")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("publisher")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, ExplicitMessageList) {
+  Book expected;
+  Author* outer = expected.mutable_author();
+  outer->set_name("outer");
+  outer->set_alive(true);
+  Author* first = outer->add_friend_();
+  first->set_name("first");
+  Author* second = outer->add_friend_();
+  second->set_name("second");
+
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "outer")
+      ->RenderBool("alive", true)
+      ->StartList("friend")
+      ->StartObject("")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NonRepeatedExplicitMessageList) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("The Author");
+
+  EXPECT_CALL(
+      listener_,
+      InvalidName(
+          _, StringPiece("publisher"),
+          StringPiece("Proto field is not repeating, cannot start list.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "The Author")
+      ->EndObject()
+      ->StartList("publisher")
+      ->StartObject("")
+      ->RenderString("name", "first")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "second")
+      ->EndObject()
+      ->EndList()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownFieldAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("unknown"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->RenderString("unknown", "Nope!")->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownFieldAtAuthorFriend) {
+  Book expected;
+  Author* paul = expected.mutable_author();
+  paul->set_name("Paul");
+  Author* mark = paul->add_friend_();
+  mark->set_name("Mark");
+  Author* john = paul->add_friend_();
+  john->set_name("John");
+  Author* luke = paul->add_friend_();
+  luke->set_name("Luke");
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("address"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("author.friend[1]")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "Paul")
+      ->StartList("friend")
+      ->StartObject("")
+      ->RenderString("name", "Mark")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "John")
+      ->RenderString("address", "Patmos")
+      ->EndObject()
+      ->StartObject("")
+      ->RenderString("name", "Luke")
+      ->EndObject()
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownObjectAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("unknown"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->StartObject("unknown")->EndObject()->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownObjectAtAuthor) {
+  Book expected;
+  Author* author = expected.mutable_author();
+  author->set_name("William");
+  author->add_pseudonym("Bill");
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("wife"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("author")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderString("name", "William")
+      ->StartObject("wife")
+      ->RenderString("name", "Hilary")
+      ->EndObject()
+      ->RenderString("pseudonym", "Bill")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownListAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("unknown"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->StartList("unknown")->EndList()->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnknownListAtPublisher) {
+  Book expected;
+  expected.set_title("Brainwashing");
+  Publisher* publisher = expected.mutable_publisher();
+  publisher->set_name("propaganda");
+
+  EXPECT_CALL(listener_, InvalidName(_, StringPiece("alliance"),
+                                     StringPiece("Cannot find field.")))
+      .With(Args<0>(HasObjectLocation("publisher")));
+  ow_->StartObject("")
+      ->StartObject("publisher")
+      ->RenderString("name", "propaganda")
+      ->StartList("alliance")
+      ->EndList()
+      ->EndObject()
+      ->RenderString("title", "Brainwashing")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, MissingRequiredField) {
+  Book expected;
+  expected.set_title("My Title");
+  expected.set_allocated_publisher(new Publisher());
+
+  EXPECT_CALL(listener_, MissingField(_, StringPiece("name")))
+      .With(Args<0>(HasObjectLocation("publisher")));
+  ow_->StartObject("")
+      ->StartObject("publisher")
+      ->EndObject()
+      ->RenderString("title", "My Title")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, InvalidFieldValueAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"garbage\"")))
+      .With(Args<0>(HasObjectLocation("length")));
+  ow_->StartObject("")->RenderString("length", "garbage")->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, MultipleInvalidFieldValues) {
+  Book expected;
+  expected.set_title("My Title");
+
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_UINT32"),
+                                      StringPiece("\"-400\"")))
+      .With(Args<0>(HasObjectLocation("length")));
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("TYPE_INT64"),
+                                      StringPiece("\"3.14\"")))
+      .With(Args<0>(HasObjectLocation("published")));
+  ow_->StartObject("")
+      ->RenderString("length", "-400")
+      ->RenderString("published", "3.14")
+      ->RenderString("title", "My Title")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnnamedFieldAtRoot) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->RenderFloat("", 3.14)->EndObject();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnnamedFieldAtAuthor) {
+  Book expected;
+  expected.set_title("noname");
+  expected.set_allocated_author(new Author());
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("author")));
+  ow_->StartObject("")
+      ->StartObject("author")
+      ->RenderInt32("", 123)
+      ->EndObject()
+      ->RenderString("title", "noname")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, UnnamedListAtRoot) {
+  Book expected;
+  expected.set_title("noname");
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")
+      ->StartList("")
+      ->EndList()
+      ->RenderString("title", "noname")
+      ->EndObject();
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootNamedObject) {
+  Book expected;
+  expected.set_title("Annie");
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece("oops"),
+                          StringPiece("Root element should not be named.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("oops")->RenderString("title", "Annie")->EndObject();
+  CheckOutput(expected, 7);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootNamedList) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece("oops"),
+                          StringPiece("Root element should not be named.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartList("oops")->RenderString("", "item")->EndList();
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootUnnamedField) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Root element must be a message.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->RenderBool("", true);
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, RootNamedField) {
+  Book empty;
+
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece("oops"),
+                          StringPiece("Root element must be a message.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->RenderBool("oops", true);
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NullValue) {
+  Book empty;
+
+  ow_->RenderNull("");
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NullValueForMessageField) {
+  Book empty;
+
+  ow_->RenderNull("author");
+  CheckOutput(empty, 0);
+}
+
+TEST_P(ProtoStreamObjectWriterTest, NullValueForPrimitiveField) {
+  Book empty;
+
+  ow_->RenderNull("length");
+  CheckOutput(empty, 0);
+}
+
+class ProtoStreamObjectWriterTimestampDurationTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterTimestampDurationTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(TimestampDuration::descriptor());
+    descriptors.push_back(google::protobuf::Timestamp::descriptor());
+    descriptors.push_back(google::protobuf::Duration::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterTimestampDurationTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, ParseTimestamp) {
+  TimestampDuration timestamp;
+  google::protobuf::Timestamp* ts = timestamp.mutable_ts();
+  ts->set_seconds(1448249855);
+  ts->set_nanos(33155000);
+
+  ow_->StartObject("")
+      ->RenderString("ts", "2015-11-23T03:37:35.033155Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError1) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: ")));
+
+  ow_->StartObject("")->RenderString("ts", "")->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError2) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: Z")));
+
+  ow_->StartObject("")->RenderString("ts", "Z")->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError3) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "1970-01-01T00:00:00.ABZ")));
+
+  ow_->StartObject("")
+      ->RenderString("ts", "1970-01-01T00:00:00.ABZ")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError4) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "-8032-10-18T00:00:00.000Z")));
+
+  ow_->StartObject("")
+      ->RenderString("ts", "-8032-10-18T00:00:00.000Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError5) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "2015-11-23T03:37:35.033155   Z")));
+
+  ow_->StartObject("")
+      // Whitespace in the Timestamp nanos is not allowed.
+      ->RenderString("ts", "2015-11-23T03:37:35.033155   Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError6) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "2015-11-23T03:37:35.033155 1234Z")));
+
+  ow_->StartObject("")
+      // Whitespace in the Timestamp nanos is not allowed.
+      ->RenderString("ts", "2015-11-23T03:37:35.033155 1234Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidTimestampError7) {
+  TimestampDuration timestamp;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+                   StringPiece("Field 'ts', Invalid time format: "
+                               "2015-11-23T03:37:35.033abc155Z")));
+
+  ow_->StartObject("")
+      // Non-numeric characters in the Timestamp nanos is not allowed.
+      ->RenderString("ts", "2015-11-23T03:37:35.033abc155Z")
+      ->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, ParseDuration) {
+  TimestampDuration duration;
+  google::protobuf::Duration* dur = duration.mutable_dur();
+  dur->set_seconds(1448216930);
+  dur->set_nanos(132262000);
+
+  ow_->StartObject("")->RenderString("dur", "1448216930.132262s")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError1) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Duration"),
+          StringPiece("Field 'dur', Illegal duration format; duration must "
+                      "end with 's'")));
+
+  ow_->StartObject("")->RenderString("dur", "")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError2) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Duration"),
+          StringPiece("Field 'dur', Invalid duration format, failed to parse "
+                      "seconds")));
+
+  ow_->StartObject("")->RenderString("dur", "s")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError3) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Duration"),
+          StringPiece("Field 'dur', Invalid duration format, failed to "
+                      "parse nano seconds")));
+
+  ow_->StartObject("")->RenderString("dur", "123.DEFs")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError4) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece("Field 'dur', Duration value exceeds limits")));
+
+  ow_->StartObject("")->RenderString("dur", "315576000002s")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest, InvalidDurationError5) {
+  TimestampDuration duration;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.Duration"),
+                   StringPiece("Field 'dur', Duration value exceeds limits")));
+
+  ow_->StartObject("")->RenderString("dur", "0.1000000001s")->EndObject();
+  CheckOutput(duration);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest,
+       MismatchedTimestampTypeInput) {
+  TimestampDuration timestamp;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Timestamp"),
+          StringPiece(
+              "Field 'ts', Invalid data type for timestamp, value is null")))
+      .With(Args<0>(HasObjectLocation("ts")));
+  ow_->StartObject("")->RenderNull("ts")->EndObject();
+  CheckOutput(timestamp);
+}
+
+TEST_P(ProtoStreamObjectWriterTimestampDurationTest,
+       MismatchedDurationTypeInput) {
+  TimestampDuration duration;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.Duration"),
+          StringPiece(
+              "Field 'dur', Invalid data type for duration, value is null")))
+      .With(Args<0>(HasObjectLocation("dur")));
+  ow_->StartObject("")->RenderNull("dur")->EndObject();
+  CheckOutput(duration);
+}
+
+class ProtoStreamObjectWriterStructTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterStructTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(StructType::descriptor());
+    descriptors.push_back(google::protobuf::Struct::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterStructTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+// TODO(skarvaje): Write tests for failure cases.
+TEST_P(ProtoStreamObjectWriterStructTest, StructRenderSuccess) {
+  StructType struct_type;
+  google::protobuf::Struct* s = struct_type.mutable_object();
+  s->mutable_fields()->operator[]("k1").set_number_value(123);
+  s->mutable_fields()->operator[]("k2").set_bool_value(true);
+
+  ow_->StartObject("")
+      ->StartObject("object")
+      ->RenderDouble("k1", 123)
+      ->RenderBool("k2", true)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(struct_type);
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, StructNullInputSuccess) {
+  StructType struct_type;
+  EXPECT_CALL(listener_,
+              InvalidName(_, StringPiece(""),
+                          StringPiece("Proto fields must have a name.")))
+      .With(Args<0>(HasObjectLocation("")));
+  ow_->StartObject("")->RenderNull("")->EndObject();
+  CheckOutput(struct_type);
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, StructInvalidInputFailure) {
+  StructType struct_type;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("type.googleapis.com/google.protobuf.Struct"),
+                   StringPiece("true")))
+      .With(Args<0>(HasObjectLocation("object")));
+
+  ow_->StartObject("")->RenderBool("object", true)->EndObject();
+  CheckOutput(struct_type);
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, SimpleRepeatedStructMapKeyTest) {
+  EXPECT_CALL(
+      listener_,
+      InvalidName(_, StringPiece("gBike"),
+                  StringPiece("Repeated map key: 'gBike' is already set.")));
+  ow_->StartObject("")
+      ->StartObject("object")
+      ->RenderString("gBike", "v1")
+      ->RenderString("gBike", "v2")
+      ->EndObject()
+      ->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, RepeatedStructMapListKeyTest) {
+  EXPECT_CALL(
+      listener_,
+      InvalidName(_, StringPiece("k1"),
+                  StringPiece("Repeated map key: 'k1' is already set.")));
+  ow_->StartObject("")
+      ->StartObject("object")
+      ->RenderString("k1", "v1")
+      ->StartList("k1")
+      ->RenderString("", "v2")
+      ->EndList()
+      ->EndObject()
+      ->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterStructTest, RepeatedStructMapObjectKeyTest) {
+  EXPECT_CALL(
+      listener_,
+      InvalidName(_, StringPiece("k1"),
+                  StringPiece("Repeated map key: 'k1' is already set.")));
+  ow_->StartObject("")
+      ->StartObject("object")
+      ->StartObject("k1")
+      ->RenderString("sub_k1", "v1")
+      ->EndObject()
+      ->StartObject("k1")
+      ->RenderString("sub_k2", "v2")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+}
+
+class ProtoStreamObjectWriterMapTest : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterMapTest()
+      : BaseProtoStreamObjectWriterTest(MapIn::descriptor()) {}
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterMapTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterMapTest, MapShouldNotAcceptList) {
+  MapIn mm;
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("Map"),
+          StringPiece("Cannot bind a list to map for field 'map_input'.")));
+  ow_->StartObject("")
+      ->StartList("map_input")
+      ->RenderString("a", "b")
+      ->EndList()
+      ->EndObject();
+  CheckOutput(mm);
+}
+
+TEST_P(ProtoStreamObjectWriterMapTest, RepeatedMapKeyTest) {
+  EXPECT_CALL(
+      listener_,
+      InvalidName(_, StringPiece("k1"),
+                  StringPiece("Repeated map key: 'k1' is already set.")));
+  ow_->StartObject("")
+      ->RenderString("other", "test")
+      ->StartObject("map_input")
+      ->RenderString("k1", "v1")
+      ->RenderString("k1", "v2")
+      ->EndObject()
+      ->EndObject();
+}
+
+class ProtoStreamObjectWriterAnyTest : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterAnyTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(AnyOut::descriptor());
+    descriptors.push_back(google::protobuf::DoubleValue::descriptor());
+    descriptors.push_back(google::protobuf::Timestamp::descriptor());
+    descriptors.push_back(google::protobuf::Any::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterAnyTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyRenderSuccess) {
+  AnyOut any;
+  google::protobuf::Any* any_type = any.mutable_any();
+  any_type->set_type_url("type.googleapis.com/google.protobuf.DoubleValue");
+  google::protobuf::DoubleValue d;
+  d.set_value(40.2);
+  any_type->set_value(d.SerializeAsString());
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.DoubleValue")
+      ->RenderDouble("value", 40.2)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, RecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  nested_any.set_value(m.SerializeAsString());
+
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, DoubleRecursiveAny) {
+  AnyOut out;
+  ::google::protobuf::Any* any = out.mutable_any();
+  any->set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any nested_any;
+  nested_any.set_type_url("type.googleapis.com/google.protobuf.Any");
+
+  ::google::protobuf::Any second_nested_any;
+  second_nested_any.set_type_url(
+      "type.googleapis.com/google.protobuf.testing.anys.AnyM");
+
+  AnyM m;
+  m.set_foo("foovalue");
+  second_nested_any.set_value(m.SerializeAsString());
+
+  nested_any.set_value(second_nested_any.SerializeAsString());
+  any->set_value(nested_any.SerializeAsString());
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Any")
+      ->StartObject("value")
+      ->RenderString("@type",
+                     "type.googleapis.com/google.protobuf.testing.anys.AnyM")
+      ->RenderString("foo", "foovalue")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, EmptyAnyFromEmptyObject) {
+  AnyOut out;
+  out.mutable_any();
+
+  ow_->StartObject("")->StartObject("any")->EndObject()->EndObject();
+
+  CheckOutput(out, 2);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithoutTypeUrlFails1) {
+  AnyOut any;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("Any"),
+                   StringPiece("Missing or invalid @type for any field in "
+                               "google.protobuf.testing.anys.AnyOut")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->StartObject("another")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithoutTypeUrlFails2) {
+  AnyOut any;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("Any"),
+                   StringPiece("Missing or invalid @type for any field in "
+                               "google.protobuf.testing.anys.AnyOut")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->StartList("another")
+      ->EndObject()
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithoutTypeUrlFails3) {
+  AnyOut any;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("Any"),
+                   StringPiece("Missing or invalid @type for any field in "
+                               "google.protobuf.testing.anys.AnyOut")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("value", "somevalue")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithInvalidTypeUrlFails) {
+  AnyOut any;
+
+  EXPECT_CALL(listener_,
+              InvalidValue(
+                  _, StringPiece("Any"),
+                  StringPiece("Invalid type URL, type URLs must be of the form "
+                              "'type.googleapis.com/<typename>', got: "
+                              "type.other.com/some.Type")));
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.other.com/some.Type")
+      ->RenderDouble("value", 40.2)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWithUnknownTypeFails) {
+  AnyOut any;
+
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_, StringPiece("Any"),
+                   StringPiece("Invalid type URL, unknown type: some.Type")));
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/some.Type")
+      ->RenderDouble("value", 40.2)
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyNullInputFails) {
+  AnyOut any;
+
+  ow_->StartObject("")->RenderNull("any")->EndObject();
+  CheckOutput(any);
+}
+
+TEST_P(ProtoStreamObjectWriterAnyTest, AnyWellKnownTypeErrorTest) {
+  EXPECT_CALL(listener_, InvalidValue(_, StringPiece("Any"),
+                                      StringPiece("Invalid time format: ")));
+
+  AnyOut any;
+  google::protobuf::Any* any_type = any.mutable_any();
+  any_type->set_type_url("type.googleapis.com/google.protobuf.Timestamp");
+
+  ow_->StartObject("")
+      ->StartObject("any")
+      ->RenderString("@type", "type.googleapis.com/google.protobuf.Timestamp")
+      ->RenderString("value", "")
+      ->EndObject()
+      ->EndObject();
+  CheckOutput(any);
+}
+
+class ProtoStreamObjectWriterFieldMaskTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterFieldMaskTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(FieldMaskTest::descriptor());
+    descriptors.push_back(google::protobuf::FieldMask::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterFieldMaskTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, SimpleFieldMaskTest) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+  expected.mutable_single_mask()->add_paths("path1");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "path1");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MutipleMasksInCompactForm) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+  expected.mutable_single_mask()->add_paths("camel_case1");
+  expected.mutable_single_mask()->add_paths("camel_case2");
+  expected.mutable_single_mask()->add_paths("camel_case3");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "camelCase1,camelCase2,camelCase3");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, RepeatedFieldMaskTest) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+  google::protobuf::FieldMask* mask = expected.add_repeated_mask();
+  mask->add_paths("field1");
+  mask->add_paths("field2");
+  expected.add_repeated_mask()->add_paths("field3");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->StartList("repeated_mask");
+  ow_->RenderString("", "field1,field2");
+  ow_->RenderString("", "field3");
+  ow_->EndList();
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, EmptyFieldMaskTest) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MaskUsingApiaryStyleShouldWork) {
+  FieldMaskTest expected;
+  expected.set_id("1");
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  // Case1
+  ow_->RenderString("single_mask",
+                    "outerField(camelCase1,camelCase2,camelCase3)");
+  expected.mutable_single_mask()->add_paths("outer_field.camel_case1");
+  expected.mutable_single_mask()->add_paths("outer_field.camel_case2");
+  expected.mutable_single_mask()->add_paths("outer_field.camel_case3");
+
+  ow_->StartList("repeated_mask");
+
+  ow_->RenderString("", "a(field1,field2)");
+  google::protobuf::FieldMask* mask = expected.add_repeated_mask();
+  mask->add_paths("a.field1");
+  mask->add_paths("a.field2");
+
+  ow_->RenderString("", "a(field3)");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field3");
+
+  ow_->RenderString("", "a()");
+  expected.add_repeated_mask();
+
+  ow_->RenderString("", "a(,)");
+  expected.add_repeated_mask();
+
+  ow_->RenderString("", "a(field1(field2(field3)))");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field1.field2.field3");
+
+  ow_->RenderString("", "a(field1(field2(field3,field4),field5),field6)");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field1.field2.field3");
+  mask->add_paths("a.field1.field2.field4");
+  mask->add_paths("a.field1.field5");
+  mask->add_paths("a.field6");
+
+  ow_->RenderString("", "a(id,field1(id,field2(field3,field4),field5),field6)");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.id");
+  mask->add_paths("a.field1.id");
+  mask->add_paths("a.field1.field2.field3");
+  mask->add_paths("a.field1.field2.field4");
+  mask->add_paths("a.field1.field5");
+  mask->add_paths("a.field6");
+
+  ow_->RenderString("", "a(((field3,field4)))");
+  mask = expected.add_repeated_mask();
+  mask->add_paths("a.field3");
+  mask->add_paths("a.field4");
+
+  ow_->EndList();
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MoreCloseThanOpenParentheses) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+          StringPiece("Field 'single_mask', Invalid FieldMask 'a(b,c))'. "
+                      "Cannot find matching '(' for all ')'.")));
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "a(b,c))");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MoreOpenThanCloseParentheses) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+          StringPiece(
+              "Field 'single_mask', Invalid FieldMask 'a(((b,c)'. Cannot "
+              "find matching ')' for all '('.")));
+
+  ow_->StartObject("");
+  ow_->RenderString("id", "1");
+  ow_->RenderString("single_mask", "a(((b,c)");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, PathWithMapKeyShouldWork) {
+  FieldMaskTest expected;
+  expected.mutable_single_mask()->add_paths("path.to.map[\"key1\"]");
+  expected.mutable_single_mask()->add_paths(
+      "path.to.map[\"e\\\"[]][scape\\\"\"]");
+  expected.mutable_single_mask()->add_paths("path.to.map[\"key2\"]");
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask",
+                    "path.to.map[\"key1\"],path.to.map[\"e\\\"[]][scape\\\"\"],"
+                    "path.to.map[\"key2\"]");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest,
+       MapKeyMustBeAtTheEndOfAPathSegment) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+          StringPiece("Field 'single_mask', Invalid FieldMask "
+                      "'path.to.map[\"key1\"]a,path.to.map[\"key2\"]'. "
+                      "Map keys should be at the end of a path segment.")));
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask",
+                    "path.to.map[\"key1\"]a,path.to.map[\"key2\"]");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MapKeyMustEnd) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+                   StringPiece("Field 'single_mask', Invalid FieldMask "
+                               "'path.to.map[\"key1\"'. Map keys should be "
+                               "represented as [\"some_key\"].")));
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask", "path.to.map[\"key1\"");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MapKeyMustBeEscapedCorrectly) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(_,
+                   StringPiece("type.googleapis.com/google.protobuf.FieldMask"),
+                   StringPiece("Field 'single_mask', Invalid FieldMask "
+                               "'path.to.map[\"ke\"y1\"]'. Map keys should be "
+                               "represented as [\"some_key\"].")));
+
+  ow_->StartObject("");
+  ow_->RenderString("single_mask", "path.to.map[\"ke\"y1\"]");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterFieldMaskTest, MapKeyCanContainAnyChars) {
+  FieldMaskTest expected;
+  expected.mutable_single_mask()->add_paths(
+      // \xE5\xAD\x99 is the UTF-8 byte sequence for chinese character 孙.
+      // We cannot embed non-ASCII characters in the code directly because
+      // some windows compilers will try to interpret them using the system's
+      // current encoding and end up with invalid UTF-8 byte sequence.
+      "path.to.map[\"(),[],\\\"'!@#$%^&*123_|War\xE5\xAD\x99,./?><\\\\\"]");
+  expected.mutable_single_mask()->add_paths("path.to.map[\"key2\"]");
+
+  ow_->StartObject("");
+  ow_->RenderString(
+      "single_mask",
+      "path.to.map[\"(),[],\\\"'!@#$%^&*123_|War\xE5\xAD\x99,./?><\\\\\"],"
+      "path.to.map[\"key2\"]");
+  ow_->EndObject();
+
+  CheckOutput(expected);
+}
+
+class ProtoStreamObjectWriterOneOfsTest
+    : public BaseProtoStreamObjectWriterTest {
+ protected:
+  ProtoStreamObjectWriterOneOfsTest() {
+    vector<const Descriptor*> descriptors;
+    descriptors.push_back(OneOfsRequest::descriptor());
+    descriptors.push_back(google::protobuf::Struct::descriptor());
+    ResetTypeInfo(descriptors);
+  }
+};
+
+INSTANTIATE_TEST_CASE_P(DifferentTypeInfoSourceTest,
+                        ProtoStreamObjectWriterOneOfsTest,
+                        ::testing::Values(
+                            testing::USE_TYPE_RESOLVER));
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForPrimitiveTypesTest) {
+  EXPECT_CALL(
+      listener_,
+      InvalidValue(
+          _, StringPiece("oneof"),
+          StringPiece(
+              "oneof field 'data' is already set. Cannot set 'intData'")));
+
+  ow_->StartObject("");
+  ow_->RenderString("strData", "blah");
+  ow_->RenderString("intData", "123");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForMessageTypesPrimitiveFirstTest) {
+  // Test for setting primitive oneof field first and then message field.
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'messageData'")));
+
+  // JSON: { "strData": "blah", "messageData": { "dataValue": 123 } }
+  ow_->StartObject("");
+  ow_->RenderString("strData", "blah");
+  ow_->StartObject("messageData");
+  ow_->RenderInt32("dataValue", 123);
+  ow_->EndObject();
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForMessageTypesMessageFirstTest) {
+  // Test for setting message oneof field first and then primitive field.
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'strData'")));
+
+  // JSON: { "messageData": { "dataValue": 123 }, "strData": "blah" }
+  ow_->StartObject("");
+  ow_->StartObject("messageData");
+  ow_->RenderInt32("dataValue", 123);
+  ow_->EndObject();
+  ow_->RenderString("strData", "blah");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForStructTypesPrimitiveFirstTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'structData'")));
+
+  // JSON: { "strData": "blah", "structData": { "a": "b" } }
+  ow_->StartObject("");
+  ow_->RenderString("strData", "blah");
+  ow_->StartObject("structData");
+  ow_->RenderString("a", "b");
+  ow_->EndObject();
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForStructTypesStructFirstTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'strData'")));
+
+  // JSON: { "structData": { "a": "b" }, "strData": "blah" }
+  ow_->StartObject("");
+  ow_->StartObject("structData");
+  ow_->RenderString("a", "b");
+  ow_->EndObject();
+  ow_->RenderString("strData", "blah");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForStructValueTypesTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'valueData'")));
+
+  // JSON: { "messageData": { "dataValue": 123 }, "valueData": { "a": "b" } }
+  ow_->StartObject("");
+  ow_->StartObject("messageData");
+  ow_->RenderInt32("dataValue", 123);
+  ow_->EndObject();
+  ow_->StartObject("valueData");
+  ow_->RenderString("a", "b");
+  ow_->EndObject();
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForWellKnownTypesPrimitiveFirstTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'tsData'")));
+
+  // JSON: { "intData": 123, "tsData": "1970-01-02T01:00:00.000Z" }
+  ow_->StartObject("");
+  ow_->RenderInt32("intData", 123);
+  ow_->RenderString("tsData", "1970-01-02T01:00:00.000Z");
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForWellKnownTypesWktFirstTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'intData'")));
+
+  // JSON: { "tsData": "1970-01-02T01:00:00.000Z", "intData": 123 }
+  ow_->StartObject("");
+  ow_->RenderString("tsData", "1970-01-02T01:00:00.000Z");
+  ow_->RenderInt32("intData", 123);
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForWellKnownTypesAndMessageTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'messageData'")));
+
+  // JSON: { "tsData": "1970-01-02T01:00:00.000Z",
+  //         "messageData": { "dataValue": 123 } }
+  ow_->StartObject("");
+  ow_->RenderString("tsData", "1970-01-02T01:00:00.000Z");
+  ow_->StartObject("messageData");
+  ow_->RenderInt32("dataValue", 123);
+  ow_->EndObject();
+  ow_->EndObject();
+}
+
+TEST_P(ProtoStreamObjectWriterOneOfsTest,
+       MultipleOneofsFailForOneofWithinAnyTest) {
+  EXPECT_CALL(listener_,
+              InvalidValue(_, StringPiece("oneof"),
+                           StringPiece("oneof field 'data' is already set. "
+                                       "Cannot set 'intData'")));
+
+  using google::protobuf::testing::oneofs::OneOfsRequest;
+  // JSON:
+  // { "anyData":
+  //    { "@type":
+  //       "type.googleapis.com/google.protobuf.testing.oneofs.OneOfsRequest",
+  //     "strData": "blah",
+  //     "intData": 123
+  //    }
+  // }
+  ow_->StartObject("");
+  ow_->StartObject("anyData");
+  ow_->RenderString(
+      "@type",
+      "type.googleapis.com/google.protobuf.testing.oneofs.OneOfsRequest");
+  ow_->RenderString("strData", "blah");
+  ow_->RenderInt32("intData", 123);
+  ow_->EndObject();
+  ow_->EndObject();
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/structured_objectwriter.h b/src/google/protobuf/util/internal/structured_objectwriter.h
new file mode 100644
index 0000000..3f065d6
--- /dev/null
+++ b/src/google/protobuf/util/internal/structured_objectwriter.h
@@ -0,0 +1,118 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+
+#include <google/protobuf/stubs/casts.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/util/internal/object_writer.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+// An StructuredObjectWriter is an ObjectWriter for writing
+// tree-structured data in a stream of events representing objects
+// and collections. Implementation of this interface can be used to
+// write an object stream to an in-memory structure, protobufs,
+// JSON, XML, or any other output format desired. The ObjectSource
+// interface is typically used as the source of an object stream.
+//
+// See JsonObjectWriter for a sample implementation of
+// StructuredObjectWriter and its use.
+//
+// Derived classes could be thread-unsafe.
+class LIBPROTOBUF_EXPORT StructuredObjectWriter : public ObjectWriter {
+ public:
+  virtual ~StructuredObjectWriter() {}
+
+ protected:
+  // A base element class for subclasses to extend, makes tracking state easier.
+  //
+  // StructuredObjectWriter behaves as a visitor. BaseElement represents a node
+  // in the input tree. Implementation of StructuredObjectWriter should also
+  // extend BaseElement to keep track of the location in the input tree.
+  class LIBPROTOBUF_EXPORT BaseElement {
+   public:
+    // Takes ownership of the parent Element.
+    explicit BaseElement(BaseElement* parent)
+        : parent_(parent), level_(parent == NULL ? 0 : parent->level() + 1) {}
+    virtual ~BaseElement() {}
+
+    // Releases ownership of the parent and returns a pointer to it.
+    template <typename ElementType>
+    ElementType* pop() {
+      return down_cast<ElementType*>(parent_.release());
+    }
+
+    // Returns true if this element is the root.
+    bool is_root() const { return parent_ == NULL; }
+
+    // Returns the number of hops from this element to the root element.
+    int level() const { return level_; }
+
+   protected:
+    // Returns pointer to parent element without releasing ownership.
+    virtual BaseElement* parent() const { return parent_.get(); }
+
+   private:
+    // Pointer to the parent Element.
+    google::protobuf::scoped_ptr<BaseElement> parent_;
+
+    // Number of hops to the root Element.
+    // The root Element has NULL parent_ and a level_ of 0.
+    const int level_;
+
+    GOOGLE_DISALLOW_IMPLICIT_CONSTRUCTORS(BaseElement);
+  };
+
+  StructuredObjectWriter() {}
+
+  // Returns the current element. Used for indentation and name overrides.
+  virtual BaseElement* element() = 0;
+
+ private:
+  // Do not add any data members to this class.
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StructuredObjectWriter);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_STRUCTURED_OBJECTWRITER_H__
diff --git a/src/google/protobuf/util/internal/testdata/anys.proto b/src/google/protobuf/util/internal/testdata/anys.proto
new file mode 100644
index 0000000..18c59cb
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/anys.proto
@@ -0,0 +1,53 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test Proto3 Any serialization.
+syntax = "proto3";
+
+package google.protobuf.testing.anys;
+option java_package = "com.google.protobuf.testing.anys";
+
+import "google/protobuf/any.proto";
+
+message AnyIn {
+  string something = 1;
+}
+
+message AnyOut {
+  google.protobuf.Any any = 1;
+}
+
+message AnyM {
+  string foo = 1;
+}
+
+service TestService {
+  rpc Call(AnyIn) returns (AnyOut);
+}
diff --git a/src/google/protobuf/util/internal/testdata/books.proto b/src/google/protobuf/util/internal/testdata/books.proto
new file mode 100644
index 0000000..82b8176
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/books.proto
@@ -0,0 +1,171 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: sven@google.com (Sven Mawson)
+//
+// Sample protos for testing.
+syntax = "proto2";
+
+package google.protobuf.testing;
+
+// A book
+message Book {
+  optional string title = 1;
+  optional Author author = 2;
+  optional uint32 length = 3;
+  optional int64 published = 4;
+  optional bytes content = 5;
+
+  optional group Data = 6 {
+    optional uint32 year = 7;
+    optional string copyright = 8;
+  }
+
+  message Label {
+    optional string key = 1;
+    optional string value = 2;
+  }
+
+  optional Publisher publisher = 9;
+  repeated Label labels = 10;
+
+  extensions 200 to 499;
+}
+
+// A publisher of a book, tests required fields.
+message Publisher {
+  required string name = 1;
+}
+
+// An author of a book
+message Author {
+  optional uint64 id = 1 [json_name = "@id"];
+  optional string name = 2;
+  repeated string pseudonym = 3;
+  optional bool alive = 4;
+  repeated Author friend = 5;
+}
+
+// For testing resiliency of our protostream parser.
+// Field numbers of Author are reused for something else.
+message BadAuthor {
+  optional string id = 1;  // non-length-delimited to length-delimited.
+  repeated uint64 name = 2;  // string to repeated (both length-delimited).
+  optional string pseudonym = 3;  // Repeated to optional.
+  repeated bool alive = 4 [packed=true];  // Optional to repeated.
+}
+
+// All primitive types
+message Primitive {
+  // 32 bit numbers:
+  optional fixed32 fix32 = 1;
+  optional uint32 u32 = 2;
+  optional int32 i32 = 3;
+  optional sfixed32 sf32 = 4;
+  optional sint32 s32 = 5;
+
+  // 64 bit numbers:
+  optional fixed64 fix64 = 6;
+  optional uint64 u64 = 7;
+  optional int64 i64 = 8;
+  optional sfixed64 sf64 = 9;
+  optional sint64 s64 = 10;
+
+  // The other stuff.
+  optional string str = 11;
+  optional bytes bytes = 12;
+  optional float float = 13;
+  optional double double = 14;
+  optional bool bool = 15;
+
+  // repeated 32 bit numbers:
+  repeated fixed32 rep_fix32 = 16;
+  repeated uint32 rep_u32 = 17;
+  repeated int32 rep_i32 = 18;
+  repeated sfixed32 rep_sf32 = 19;
+  repeated sint32 rep_s32 = 20;
+
+  // repeated 64 bit numbers:
+  repeated fixed64 rep_fix64 = 21;
+  repeated uint64 rep_u64 = 22;
+  repeated int64 rep_i64 = 23;
+  repeated sfixed64 rep_sf64 = 24;
+  repeated sint64 rep_s64 = 25;
+
+  // repeated other stuff:
+  repeated string rep_str = 26;
+  repeated bytes rep_bytes = 27;
+  repeated float rep_float = 28;
+  repeated double rep_double = 29;
+  repeated bool rep_bool = 30;
+}
+
+// Test packed versions of all repeated primitives.
+// The field numbers should match their non-packed version in Primitive message.
+message PackedPrimitive {
+  // repeated 32 bit numbers:
+  repeated fixed32 rep_fix32 = 16 [packed=true];
+  repeated uint32 rep_u32 = 17 [packed=true];
+  repeated int32 rep_i32 = 18 [packed=true];
+  repeated sfixed32 rep_sf32 = 19 [packed=true];
+  repeated sint32 rep_s32 = 20 [packed=true];
+
+  // repeated 64 bit numbers:
+  repeated fixed64 rep_fix64 = 21 [packed=true];
+  repeated uint64 rep_u64 = 22 [packed=true];
+  repeated int64 rep_i64 = 23 [packed=true];
+  repeated sfixed64 rep_sf64 = 24 [packed=true];
+  repeated sint64 rep_s64 = 25 [packed=true];
+
+  // repeated other stuff:
+  repeated float rep_float = 28 [packed=true];
+  repeated double rep_double = 29 [packed=true];
+  repeated bool rep_bool = 30 [packed=true];
+}
+
+// Test extensions.
+extend Book {
+  repeated Author more_author = 201;
+}
+
+// Test nested extensions.
+message NestedBook {
+  extend Book {
+    optional NestedBook another_book = 301;
+  }
+  // Recurse
+  optional Book book = 1;
+}
+
+// For testing resiliency of our protostream parser.
+// Field number of NestedBook is reused for something else.
+message BadNestedBook {
+  repeated uint32 book = 1 [packed=true];  // Packed to optional message.
+}
diff --git a/src/google/protobuf/util/internal/testdata/default_value.proto b/src/google/protobuf/util/internal/testdata/default_value.proto
new file mode 100644
index 0000000..cccc741
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/default_value.proto
@@ -0,0 +1,170 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+import "google/protobuf/any.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/wrappers.proto";
+
+message DefaultValueTestCases {
+  DoubleMessage empty_double = 1;
+  DoubleMessage double_with_default_value = 2;
+  DoubleMessage double_with_nondefault_value = 3;
+  DoubleMessage repeated_double = 4;
+  DoubleMessage nested_message = 5;
+  DoubleMessage repeated_nested_message = 6;
+  DoubleMessage double_message_with_oneof = 7;
+  StructMessage empty_struct = 201;
+  StructMessage empty_struct2 = 202;
+  StructMessage struct_with_null_value = 203;
+  StructMessage struct_with_values = 204;
+  StructMessage struct_with_nested_struct = 205;
+  StructMessage struct_with_nested_list = 206;
+  StructMessage struct_with_list_of_nulls = 207;
+  StructMessage struct_with_list_of_lists = 208;
+  StructMessage struct_with_list_of_structs = 209;
+  google.protobuf.Struct top_level_struct = 210;
+  ValueMessage value_wrapper_simple = 212;
+  ValueMessage value_wrapper_with_struct = 213;
+  ValueMessage value_wrapper_with_list = 214;
+  ListValueMessage list_value_wrapper = 215;
+  google.protobuf.Value top_level_value_simple = 216;
+  google.protobuf.Value top_level_value_with_struct = 217;
+  google.protobuf.Value top_level_value_with_list = 218;
+  google.protobuf.ListValue top_level_listvalue = 219;
+  AnyMessage empty_any = 301;
+  AnyMessage type_only_any = 302;
+  AnyMessage recursive_any = 303;
+  AnyMessage any_with_message_value = 304;
+  AnyMessage any_with_nested_message = 305;
+  AnyMessage any_with_message_containing_map = 306;
+  AnyMessage any_with_message_containing_struct = 307;
+  google.protobuf.Any top_level_any = 308;
+  StringtoIntMap empty_map = 401;
+  StringtoIntMap string_to_int = 402;
+  IntToStringMap int_to_string = 403;
+  MixedMap mixed1 = 404;
+  MixedMap2 mixed2 = 405;
+  MixedMap2 empty_mixed2 = 406;
+  MessageMap map_of_objects = 407;
+  MixedMap mixed_empty = 408;
+  MessageMap message_map_empty = 409;
+  DoubleValueMessage double_value = 501;
+  DoubleValueMessage double_value_default = 502;
+}
+
+message DoubleMessage {
+  double double_value = 1;
+  repeated double repeated_double = 2;
+  DoubleMessage nested_message = 3;
+  repeated DoubleMessage repeated_nested_message = 4;
+  google.protobuf.DoubleValue double_wrapper = 100;
+  oneof value {
+    string str_value = 112;
+    int64 num_value = 113;
+  }
+}
+
+message StructMessage {
+  google.protobuf.Struct struct = 1;
+}
+
+message ValueMessage {
+  google.protobuf.Value value = 1;
+}
+
+message ListValueMessage {
+  google.protobuf.ListValue shopping_list = 1;
+}
+message RequestMessage {
+  string content = 1;
+}
+
+// A test service.
+service DefaultValueTestService {
+  // A test method.
+  rpc Call(RequestMessage) returns (DefaultValueTestCases);
+}
+
+message AnyMessage {
+  google.protobuf.Any any = 1;
+  AnyData data = 2;
+}
+
+message AnyData {
+  int32 attr = 1;
+  string str = 2;
+  repeated string msgs = 3;
+  AnyData nested_data = 4;
+  map<string, string> map_data = 7;
+  google.protobuf.Struct struct_data = 8;
+  repeated AnyData repeated_data = 9;
+}
+
+message StringtoIntMap {
+  map<string, int32> map = 1;
+}
+
+message IntToStringMap {
+  map<int32, string> map = 1;
+}
+
+message MixedMap {
+  string msg = 1;
+  map<string, float> map = 2;
+  int32 int_value = 3;
+}
+
+message MixedMap2 {
+  enum E {
+    E0 = 0;
+    E1 = 1;
+    E2 = 2;
+    E3 = 3;
+  }
+  map<int32, bool> map = 1;
+  E ee = 2;
+  string msg = 4;
+}
+
+message MessageMap {
+  message M {
+    int32 inner_int = 1;
+    string inner_text = 2;
+  }
+  map<string, M> map = 1;
+}
+
+message DoubleValueMessage {
+  google.protobuf.DoubleValue double = 1;
+}
diff --git a/src/google/protobuf/util/internal/testdata/default_value_test.proto b/src/google/protobuf/util/internal/testdata/default_value_test.proto
new file mode 100644
index 0000000..9328834
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/default_value_test.proto
@@ -0,0 +1,53 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+message DefaultValueTest {
+  double double_value = 1;
+  repeated double repeated_double = 2;
+  float float_value = 3;
+  int64 int64_value = 5;
+  uint64 uint64_value = 7;
+  int32 int32_value = 9;
+  uint32 uint32_value = 11;
+  bool bool_value = 13;
+  string string_value = 15;
+  bytes bytes_value = 17 [ctype = CORD];
+
+  enum EnumDefault {
+    ENUM_FIRST = 0;
+    ENUM_SECOND = 1;
+    ENUM_THIRD = 2;
+  }
+  EnumDefault enum_value = 18;
+}
diff --git a/src/google/protobuf/util/internal/testdata/field_mask.proto b/src/google/protobuf/util/internal/testdata/field_mask.proto
new file mode 100644
index 0000000..e8b2bc5
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/field_mask.proto
@@ -0,0 +1,71 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+import "google/protobuf/field_mask.proto";
+
+message NestedFieldMask {
+  string data = 1;
+  google.protobuf.FieldMask single_mask = 2;
+  repeated google.protobuf.FieldMask repeated_mask = 3;
+}
+
+message FieldMaskTest {
+  string id = 1;
+  google.protobuf.FieldMask single_mask = 2;
+  repeated google.protobuf.FieldMask repeated_mask = 3;
+  repeated NestedFieldMask nested_mask = 4;
+}
+
+message FieldMaskTestCases {
+  FieldMaskWrapper single_mask = 1;
+  FieldMaskWrapper multiple_mask = 2;
+  FieldMaskWrapper snake_camel = 3;
+  FieldMaskWrapper empty_field = 4;
+  FieldMaskWrapper apiary_format1 = 5;
+  FieldMaskWrapper apiary_format2 = 6;
+  FieldMaskWrapper apiary_format3 = 7;
+  FieldMaskWrapper map_key1 = 8;
+  FieldMaskWrapper map_key2 = 9;
+  FieldMaskWrapper map_key3 = 10;
+  FieldMaskWrapper map_key4 = 11;
+  FieldMaskWrapper map_key5 = 12;
+}
+
+message FieldMaskWrapper {
+  google.protobuf.FieldMask mask = 1;
+}
+
+service FieldMaskTestService {
+  rpc Call(FieldMaskTestCases) returns (FieldMaskTestCases);
+}
diff --git a/src/google/protobuf/util/internal/testdata/maps.proto b/src/google/protobuf/util/internal/testdata/maps.proto
new file mode 100644
index 0000000..6475ecd
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/maps.proto
@@ -0,0 +1,86 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test proto3 maps.
+syntax = "proto3";
+
+package google.protobuf.testing.maps;
+option java_package = "com.google.protobuf.testing.maps";
+
+message MapIn {
+  string other = 1;
+  repeated string things = 2;
+  map<string, string> map_input = 3;
+}
+
+message MapOut {
+  map<string, MapM> map1 = 1;
+  map<string, MapOut> map2 = 2;
+  map<int32, string> map3 = 3;
+  map<bool, string> map4 = 5;
+  string bar = 4;
+}
+
+// A message with exactly the same wire representation as MapOut, but using
+// repeated message fields instead of map fields. We use this message to test
+// the wire-format compatibility of the JSON transcoder (e.g., whether it
+// handles missing keys correctly).
+message MapOutWireFormat {
+  message Map1Entry {
+    string key = 1;
+    MapM value = 2;
+  }
+  repeated Map1Entry map1 = 1;
+  message Map2Entry {
+    string key = 1;
+    MapOut value = 2;
+  }
+  repeated Map2Entry map2 = 2;
+  message Map3Entry {
+    int32 key = 1;
+    string value = 2;
+  }
+  repeated Map3Entry map3 = 3;
+  message Map4Entry {
+    bool key = 1;
+    string value = 2;
+  }
+  repeated Map4Entry map4 = 5;
+  string bar = 4;
+}
+
+message MapM {
+  string foo = 1;
+}
+
+service TestService {
+  rpc Call1(MapIn) returns (MapOut);
+  rpc Call2(MapIn) returns (MapOut);
+}
diff --git a/src/google/protobuf/util/internal/testdata/oneofs.proto b/src/google/protobuf/util/internal/testdata/oneofs.proto
new file mode 100644
index 0000000..5bc9fa0
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/oneofs.proto
@@ -0,0 +1,68 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test oneofs.
+syntax = "proto3";
+
+import "google/protobuf/any.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/timestamp.proto";
+
+package google.protobuf.testing.oneofs;
+option java_package = "com.google.protobuf.testing.oneofs";
+
+message OneOfsRequest {
+  string value = 1;
+  oneof data {
+    string str_data = 2;
+    int32 int_data = 3;
+    // Simple message
+    Data message_data = 4;
+    // Well known types
+    google.protobuf.Struct struct_data = 5;
+    google.protobuf.Value value_data = 6;
+    google.protobuf.ListValue list_value_data = 7;
+    google.protobuf.Timestamp ts_data = 8;
+  }
+  google.protobuf.Any any_data = 19;
+}
+
+message Data {
+  int32 data_value = 1;
+}
+
+message Response {
+  string value = 1;
+}
+
+service TestService {
+  // Test call.
+  rpc Call(OneOfsRequest) returns (Response);
+}
diff --git a/src/google/protobuf/util/internal/testdata/struct.proto b/src/google/protobuf/util/internal/testdata/struct.proto
new file mode 100644
index 0000000..c15aba0
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/struct.proto
@@ -0,0 +1,45 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test proto3 struct.
+syntax = "proto3";
+
+package google.protobuf.testing.structs;
+option java_package = "com.google.protobuf.testing.structs";
+
+import "google/protobuf/struct.proto";
+
+message StructType {
+  google.protobuf.Struct object = 1;
+}
+
+service TestService {
+  rpc Call(StructType) returns (StructType);
+}
diff --git a/src/google/protobuf/util/internal/testdata/timestamp_duration.proto b/src/google/protobuf/util/internal/testdata/timestamp_duration.proto
new file mode 100644
index 0000000..56351f1
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/timestamp_duration.proto
@@ -0,0 +1,47 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Proto to test proto3 Timestamp and Duration.
+syntax = "proto3";
+
+package google.protobuf.testing.timestampduration;
+option java_package = "com.google.protobuf.testing.timestampduration";
+
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/duration.proto";
+
+message TimestampDuration {
+  google.protobuf.Timestamp ts = 1;
+  google.protobuf.Duration dur = 2;
+}
+
+service TestService {
+  rpc Call(TimestampDuration) returns (TimestampDuration);
+}
diff --git a/src/google/protobuf/util/internal/testdata/wrappers.proto b/src/google/protobuf/util/internal/testdata/wrappers.proto
new file mode 100644
index 0000000..eabc99f
--- /dev/null
+++ b/src/google/protobuf/util/internal/testdata/wrappers.proto
@@ -0,0 +1,100 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package google.protobuf.testing;
+
+import "google/protobuf/wrappers.proto";
+
+// Top-level test cases proto used by MarshallingTest. See description
+// at the top of the class MarshallingTest for details on how to write
+// test cases.
+message WrappersTestCases {
+  DoubleWrapper double_wrapper = 1;
+  FloatWrapper float_wrapper = 2;
+  Int64Wrapper int64_wrapper = 3;
+  UInt64Wrapper uint64_wrapper = 4;
+  Int32Wrapper int32_wrapper = 5;
+  UInt32Wrapper uint32_wrapper = 6;
+  BoolWrapper bool_wrapper = 7;
+  StringWrapper string_wrapper = 8;
+  BytesWrapper bytes_wrapper = 9;
+
+  DoubleWrapper double_wrapper_default = 10;
+  FloatWrapper float_wrapper_default = 11;
+  Int64Wrapper int64_wrapper_default = 12;
+  UInt64Wrapper uint64_wrapper_default = 13;
+  Int32Wrapper int32_wrapper_default = 14;
+  UInt32Wrapper uint32_wrapper_default = 15;
+  BoolWrapper bool_wrapper_default = 16;
+  StringWrapper string_wrapper_default = 17;
+  BytesWrapper bytes_wrapper_default = 18;
+}
+
+message DoubleWrapper {
+  google.protobuf.DoubleValue double = 1;
+}
+
+message FloatWrapper {
+  google.protobuf.FloatValue float = 1;
+}
+
+message Int64Wrapper {
+  google.protobuf.Int64Value int64 = 1;
+}
+
+message UInt64Wrapper {
+  google.protobuf.UInt64Value uint64 = 1;
+}
+
+message Int32Wrapper {
+  google.protobuf.Int32Value int32 = 1;
+}
+
+message UInt32Wrapper {
+  google.protobuf.UInt32Value uint32 = 1;
+}
+
+message BoolWrapper {
+  google.protobuf.BoolValue bool = 1;
+}
+
+message StringWrapper {
+  google.protobuf.StringValue string = 1;
+}
+
+message BytesWrapper {
+  google.protobuf.BytesValue bytes = 1;
+}
+
+service WrappersTestService {
+  rpc Call(WrappersTestCases) returns (WrappersTestCases);
+}
diff --git a/src/google/protobuf/util/internal/type_info.cc b/src/google/protobuf/util/internal/type_info.cc
new file mode 100644
index 0000000..00a8ee7
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info.cc
@@ -0,0 +1,171 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/type_info.h>
+
+#include <map>
+#include <set>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+// A TypeInfo that looks up information provided by a TypeResolver.
+class TypeInfoForTypeResolver : public TypeInfo {
+ public:
+  explicit TypeInfoForTypeResolver(TypeResolver* type_resolver)
+      : type_resolver_(type_resolver) {}
+
+  virtual ~TypeInfoForTypeResolver() {
+    DeleteCachedTypes(&cached_types_);
+    DeleteCachedTypes(&cached_enums_);
+  }
+
+  virtual util::StatusOr<const google::protobuf::Type*> ResolveTypeUrl(
+      StringPiece type_url) const {
+    map<StringPiece, StatusOrType>::iterator it = cached_types_.find(type_url);
+    if (it != cached_types_.end()) {
+      return it->second;
+    }
+    // Stores the string value so it can be referenced using StringPiece in the
+    // cached_types_ map.
+    const string& string_type_url =
+        *string_storage_.insert(type_url.ToString()).first;
+    google::protobuf::scoped_ptr<google::protobuf::Type> type(new google::protobuf::Type());
+    util::Status status =
+        type_resolver_->ResolveMessageType(string_type_url, type.get());
+    StatusOrType result =
+        status.ok() ? StatusOrType(type.release()) : StatusOrType(status);
+    cached_types_[string_type_url] = result;
+    return result;
+  }
+
+  virtual const google::protobuf::Type* GetTypeByTypeUrl(
+      StringPiece type_url) const {
+    StatusOrType result = ResolveTypeUrl(type_url);
+    return result.ok() ? result.ValueOrDie() : NULL;
+  }
+
+  virtual const google::protobuf::Enum* GetEnumByTypeUrl(
+      StringPiece type_url) const {
+    map<StringPiece, StatusOrEnum>::iterator it = cached_enums_.find(type_url);
+    if (it != cached_enums_.end()) {
+      return it->second.ok() ? it->second.ValueOrDie() : NULL;
+    }
+    // Stores the string value so it can be referenced using StringPiece in the
+    // cached_enums_ map.
+    const string& string_type_url =
+        *string_storage_.insert(type_url.ToString()).first;
+    google::protobuf::scoped_ptr<google::protobuf::Enum> enum_type(
+        new google::protobuf::Enum());
+    util::Status status =
+        type_resolver_->ResolveEnumType(string_type_url, enum_type.get());
+    StatusOrEnum result =
+        status.ok() ? StatusOrEnum(enum_type.release()) : StatusOrEnum(status);
+    cached_enums_[string_type_url] = result;
+    return result.ok() ? result.ValueOrDie() : NULL;
+  }
+
+  virtual const google::protobuf::Field* FindField(
+      const google::protobuf::Type* type, StringPiece camel_case_name) const {
+    if (indexed_types_.find(type) == indexed_types_.end()) {
+      PopulateNameLookupTable(type);
+      indexed_types_.insert(type);
+    }
+    StringPiece name =
+        FindWithDefault(camel_case_name_table_, camel_case_name, StringPiece());
+    if (name.empty()) {
+      // Didn't find a mapping. Use whatever provided.
+      name = camel_case_name;
+    }
+    return FindFieldInTypeOrNull(type, name);
+  }
+
+ private:
+  typedef util::StatusOr<const google::protobuf::Type*> StatusOrType;
+  typedef util::StatusOr<const google::protobuf::Enum*> StatusOrEnum;
+
+  template <typename T>
+  static void DeleteCachedTypes(map<StringPiece, T>* cached_types) {
+    for (typename map<StringPiece, T>::iterator it = cached_types->begin();
+         it != cached_types->end(); ++it) {
+      if (it->second.ok()) {
+        delete it->second.ValueOrDie();
+      }
+    }
+  }
+
+  void PopulateNameLookupTable(const google::protobuf::Type* type) const {
+    for (int i = 0; i < type->fields_size(); ++i) {
+      const google::protobuf::Field& field = type->fields(i);
+      StringPiece name = field.name();
+      StringPiece camel_case_name = field.json_name();
+      const StringPiece* existing = InsertOrReturnExisting(
+          &camel_case_name_table_, camel_case_name, name);
+      if (existing && *existing != name) {
+        GOOGLE_LOG(WARNING) << "Field '" << name << "' and '" << *existing
+                     << "' map to the same camel case name '" << camel_case_name
+                     << "'.";
+      }
+    }
+  }
+
+  TypeResolver* type_resolver_;
+
+  // Stores string values that will be referenced by StringPieces in
+  // cached_types_, cached_enums_ and camel_case_name_table_.
+  mutable set<string> string_storage_;
+
+  mutable map<StringPiece, StatusOrType> cached_types_;
+  mutable map<StringPiece, StatusOrEnum> cached_enums_;
+
+  mutable set<const google::protobuf::Type*> indexed_types_;
+  mutable map<StringPiece, StringPiece> camel_case_name_table_;
+};
+}  // namespace
+
+TypeInfo* TypeInfo::NewTypeInfo(TypeResolver* type_resolver) {
+  return new TypeInfoForTypeResolver(type_resolver);
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/type_info.h b/src/google/protobuf/util/internal/type_info.h
new file mode 100644
index 0000000..d813317
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info.h
@@ -0,0 +1,92 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_H__
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+// Internal helper class for type resolving. Note that this class is not
+// thread-safe and should only be accessed in one thread.
+class LIBPROTOBUF_EXPORT TypeInfo {
+ public:
+  TypeInfo() {}
+  virtual ~TypeInfo() {}
+
+  // Resolves a type url into a Type. If the type url is invalid, returns
+  // INVALID_ARGUMENT error status. If the type url is valid but the
+  // corresponding type cannot be found, returns a NOT_FOUND error status.
+  //
+  // This TypeInfo class retains the ownership of the returned pointer.
+  virtual util::StatusOr<const google::protobuf::Type*> ResolveTypeUrl(
+      StringPiece type_url) const = 0;
+
+  // Resolves a type url into a Type. Like ResolveTypeUrl() but returns
+  // NULL if the type url is invalid or the type cannot be found.
+  //
+  // This TypeInfo class retains the ownership of the returned pointer.
+  virtual const google::protobuf::Type* GetTypeByTypeUrl(
+      StringPiece type_url) const = 0;
+
+  // Resolves a type url for an enum. Returns NULL if the type url is
+  // invalid or the type cannot be found.
+  //
+  // This TypeInfo class retains the ownership of the returned pointer.
+  virtual const google::protobuf::Enum* GetEnumByTypeUrl(
+      StringPiece type_url) const = 0;
+
+  // Looks up a field in the specified type given a CamelCase name.
+  virtual const google::protobuf::Field* FindField(
+      const google::protobuf::Type* type,
+      StringPiece camel_case_name) const = 0;
+
+  // Creates a TypeInfo object that looks up type information from a
+  // TypeResolver. Caller takes ownership of the returned pointer.
+  static TypeInfo* NewTypeInfo(TypeResolver* type_resolver);
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeInfo);
+};
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_H__
diff --git a/src/google/protobuf/util/internal/type_info_test_helper.cc b/src/google/protobuf/util/internal/type_info_test_helper.cc
new file mode 100644
index 0000000..1b9c515
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info_test_helper.cc
@@ -0,0 +1,134 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/type_info_test_helper.h>
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <vector>
+
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/util/type_resolver_util.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+namespace testing {
+
+
+void TypeInfoTestHelper::ResetTypeInfo(
+    const vector<const Descriptor*>& descriptors) {
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      const DescriptorPool* pool = descriptors[0]->file()->pool();
+      for (int i = 1; i < descriptors.size(); ++i) {
+        GOOGLE_CHECK(pool == descriptors[i]->file()->pool())
+            << "Descriptors from different pools are not supported.";
+      }
+      type_resolver_.reset(
+          NewTypeResolverForDescriptorPool(kTypeServiceBaseUrl, pool));
+      typeinfo_.reset(TypeInfo::NewTypeInfo(type_resolver_.get()));
+      return;
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+}
+
+void TypeInfoTestHelper::ResetTypeInfo(const Descriptor* descriptor) {
+  vector<const Descriptor*> descriptors;
+  descriptors.push_back(descriptor);
+  ResetTypeInfo(descriptors);
+}
+
+void TypeInfoTestHelper::ResetTypeInfo(const Descriptor* descriptor1,
+                                       const Descriptor* descriptor2) {
+  vector<const Descriptor*> descriptors;
+  descriptors.push_back(descriptor1);
+  descriptors.push_back(descriptor2);
+  ResetTypeInfo(descriptors);
+}
+
+TypeInfo* TypeInfoTestHelper::GetTypeInfo() { return typeinfo_.get(); }
+
+ProtoStreamObjectSource* TypeInfoTestHelper::NewProtoSource(
+    io::CodedInputStream* coded_input, const string& type_url) {
+  const google::protobuf::Type* type = typeinfo_->GetTypeByTypeUrl(type_url);
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      return new ProtoStreamObjectSource(coded_input, type_resolver_.get(),
+                                         *type);
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+  return NULL;
+}
+
+ProtoStreamObjectWriter* TypeInfoTestHelper::NewProtoWriter(
+    const string& type_url, strings::ByteSink* output,
+    ErrorListener* listener) {
+  const google::protobuf::Type* type = typeinfo_->GetTypeByTypeUrl(type_url);
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      return new ProtoStreamObjectWriter(type_resolver_.get(), *type, output,
+                                         listener);
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+  return NULL;
+}
+
+DefaultValueObjectWriter* TypeInfoTestHelper::NewDefaultValueWriter(
+    const string& type_url, ObjectWriter* writer) {
+  const google::protobuf::Type* type = typeinfo_->GetTypeByTypeUrl(type_url);
+  switch (type_) {
+    case USE_TYPE_RESOLVER: {
+      return new DefaultValueObjectWriter(type_resolver_.get(), *type, writer);
+    }
+  }
+  GOOGLE_LOG(FATAL) << "Can not reach here.";
+  return NULL;
+}
+
+}  // namespace testing
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/type_info_test_helper.h b/src/google/protobuf/util/internal/type_info_test_helper.h
new file mode 100644
index 0000000..6916a73
--- /dev/null
+++ b/src/google/protobuf/util/internal/type_info_test_helper.h
@@ -0,0 +1,98 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_TEST_HELPER_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_TEST_HELPER_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <vector>
+
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/type_info.h>
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+namespace testing {
+
+enum TypeInfoSource {
+  USE_TYPE_RESOLVER,
+};
+
+// In the unit-tests we want to test two scenarios: one with type info from
+// ServiceTypeInfo, the other with type info from TypeResolver. This class
+// wraps the detail of where the type info is from and provides the same
+// interface so the same unit-test code can test both scenarios.
+class TypeInfoTestHelper {
+ public:
+  explicit TypeInfoTestHelper(TypeInfoSource type) : type_(type) {}
+
+  // Creates a TypeInfo object for the given set of descriptors.
+  void ResetTypeInfo(const vector<const Descriptor*>& descriptors);
+
+  // Convinent overloads.
+  void ResetTypeInfo(const Descriptor* descriptor);
+  void ResetTypeInfo(const Descriptor* descriptor1,
+                     const Descriptor* descriptor2);
+
+  // Returns the TypeInfo created after ResetTypeInfo.
+  TypeInfo* GetTypeInfo();
+
+  ProtoStreamObjectSource* NewProtoSource(io::CodedInputStream* coded_input,
+                                          const string& type_url);
+
+  ProtoStreamObjectWriter* NewProtoWriter(const string& type_url,
+                                          strings::ByteSink* output,
+                                          ErrorListener* listener);
+
+  DefaultValueObjectWriter* NewDefaultValueWriter(const string& type_url,
+                                                  ObjectWriter* writer);
+
+ private:
+  TypeInfoSource type_;
+  google::protobuf::scoped_ptr<TypeInfo> typeinfo_;
+  google::protobuf::scoped_ptr<TypeResolver> type_resolver_;
+};
+}  // namespace testing
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_TYPE_INFO_TEST_HELPER_H__
diff --git a/src/google/protobuf/util/internal/utility.cc b/src/google/protobuf/util/internal/utility.cc
new file mode 100644
index 0000000..1ddf248
--- /dev/null
+++ b/src/google/protobuf/util/internal/utility.cc
@@ -0,0 +1,356 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/internal/utility.h>
+
+#include <google/protobuf/stubs/callback.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/constants.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/map_util.h>
+#include <google/protobuf/stubs/mathlimits.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace converter {
+
+namespace {
+const StringPiece SkipWhiteSpace(StringPiece str) {
+  StringPiece::size_type i;
+  for (i = 0; i < str.size() && isspace(str[i]); ++i) {
+  }
+  GOOGLE_DCHECK(i == str.size() || !isspace(str[i]));
+  return StringPiece(str, i);
+}
+}  // namespace
+
+bool GetBoolOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, bool default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetBoolFromAny(opt->value());
+}
+
+int64 GetInt64OptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, int64 default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetInt64FromAny(opt->value());
+}
+
+double GetDoubleOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, double default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetDoubleFromAny(opt->value());
+}
+
+string GetStringOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, const string& default_value) {
+  const google::protobuf::Option* opt = FindOptionOrNull(options, option_name);
+  if (opt == NULL) {
+    return default_value;
+  }
+  return GetStringFromAny(opt->value());
+}
+
+template <typename T>
+void ParseFromAny(const string& data, T* result) {
+  result->ParseFromString(data);
+}
+
+// Returns a boolean value contained in Any type.
+// TODO(skarvaje): Add type checking & error messages here.
+bool GetBoolFromAny(const google::protobuf::Any& any) {
+  google::protobuf::BoolValue b;
+  ParseFromAny(any.value(), &b);
+  return b.value();
+}
+
+int64 GetInt64FromAny(const google::protobuf::Any& any) {
+  google::protobuf::Int64Value i;
+  ParseFromAny(any.value(), &i);
+  return i.value();
+}
+
+double GetDoubleFromAny(const google::protobuf::Any& any) {
+  google::protobuf::DoubleValue i;
+  ParseFromAny(any.value(), &i);
+  return i.value();
+}
+
+string GetStringFromAny(const google::protobuf::Any& any) {
+  google::protobuf::StringValue s;
+  ParseFromAny(any.value(), &s);
+  return s.value();
+}
+
+const StringPiece GetTypeWithoutUrl(StringPiece type_url) {
+  size_t idx = type_url.rfind('/');
+  return type_url.substr(idx + 1);
+}
+
+const string GetFullTypeWithUrl(StringPiece simple_type) {
+  return StrCat(kTypeServiceBaseUrl, "/", simple_type);
+}
+
+const google::protobuf::Option* FindOptionOrNull(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name) {
+  for (int i = 0; i < options.size(); ++i) {
+    const google::protobuf::Option& opt = options.Get(i);
+    if (opt.name() == option_name) {
+      return &opt;
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::Field* FindFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece field_name) {
+  if (type != NULL) {
+    for (int i = 0; i < type->fields_size(); ++i) {
+      const google::protobuf::Field& field = type->fields(i);
+      if (field.name() == field_name) {
+        return &field;
+      }
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::Field* FindJsonFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece json_name) {
+  if (type != NULL) {
+    for (int i = 0; i < type->fields_size(); ++i) {
+      const google::protobuf::Field& field = type->fields(i);
+      if (field.json_name() == json_name) {
+        return &field;
+      }
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::EnumValue* FindEnumValueByNameOrNull(
+    const google::protobuf::Enum* enum_type, StringPiece enum_name) {
+  if (enum_type != NULL) {
+    for (int i = 0; i < enum_type->enumvalue_size(); ++i) {
+      const google::protobuf::EnumValue& enum_value = enum_type->enumvalue(i);
+      if (enum_value.name() == enum_name) {
+        return &enum_value;
+      }
+    }
+  }
+  return NULL;
+}
+
+const google::protobuf::EnumValue* FindEnumValueByNumberOrNull(
+    const google::protobuf::Enum* enum_type, int32 value) {
+  if (enum_type != NULL) {
+    for (int i = 0; i < enum_type->enumvalue_size(); ++i) {
+      const google::protobuf::EnumValue& enum_value = enum_type->enumvalue(i);
+      if (enum_value.number() == value) {
+        return &enum_value;
+      }
+    }
+  }
+  return NULL;
+}
+
+string ToCamelCase(const StringPiece input) {
+  bool capitalize_next = false;
+  bool was_cap = true;
+  bool is_cap = false;
+  bool first_word = true;
+  string result;
+  result.reserve(input.size());
+
+  for (size_t i = 0; i < input.size(); ++i, was_cap = is_cap) {
+    is_cap = ascii_isupper(input[i]);
+    if (input[i] == '_') {
+      capitalize_next = true;
+      if (!result.empty()) first_word = false;
+      continue;
+    } else if (first_word) {
+      // Consider when the current character B is capitalized,
+      // first word ends when:
+      // 1) following a lowercase:   "...aB..."
+      // 2) followed by a lowercase: "...ABc..."
+      if (!result.empty() && is_cap &&
+          (!was_cap || (i + 1 < input.size() && ascii_islower(input[i + 1])))) {
+        first_word = false;
+      } else {
+        result.push_back(ascii_tolower(input[i]));
+        continue;
+      }
+    } else if (capitalize_next) {
+      capitalize_next = false;
+      if (ascii_islower(input[i])) {
+        result.push_back(ascii_toupper(input[i]));
+        continue;
+      }
+    }
+    result.push_back(input[i]);
+  }
+  return result;
+}
+
+string ToSnakeCase(StringPiece input) {
+  bool was_not_underscore = false;  // Initialize to false for case 1 (below)
+  bool was_not_cap = false;
+  string result;
+  result.reserve(input.size() << 1);
+
+  for (size_t i = 0; i < input.size(); ++i) {
+    if (ascii_isupper(input[i])) {
+      // Consider when the current character B is capitalized:
+      // 1) At beginning of input:   "B..." => "b..."
+      //    (e.g. "Biscuit" => "biscuit")
+      // 2) Following a lowercase:   "...aB..." => "...a_b..."
+      //    (e.g. "gBike" => "g_bike")
+      // 3) At the end of input:     "...AB" => "...ab"
+      //    (e.g. "GoogleLAB" => "google_lab")
+      // 4) Followed by a lowercase: "...ABc..." => "...a_bc..."
+      //    (e.g. "GBike" => "g_bike")
+      if (was_not_underscore &&               //            case 1 out
+          (was_not_cap ||                     // case 2 in, case 3 out
+           (i + 1 < input.size() &&           //            case 3 out
+            ascii_islower(input[i + 1])))) {  // case 4 in
+        // We add an underscore for case 2 and case 4.
+        result.push_back('_');
+      }
+      result.push_back(ascii_tolower(input[i]));
+      was_not_underscore = true;
+      was_not_cap = false;
+    } else {
+      result.push_back(input[i]);
+      was_not_underscore = input[i] != '_';
+      was_not_cap = true;
+    }
+  }
+  return result;
+}
+
+set<string>* well_known_types_ = NULL;
+GOOGLE_PROTOBUF_DECLARE_ONCE(well_known_types_init_);
+const char* well_known_types_name_array_[] = {
+    "google.protobuf.Timestamp",   "google.protobuf.Duration",
+    "google.protobuf.DoubleValue", "google.protobuf.FloatValue",
+    "google.protobuf.Int64Value",  "google.protobuf.UInt64Value",
+    "google.protobuf.Int32Value",  "google.protobuf.UInt32Value",
+    "google.protobuf.BoolValue",   "google.protobuf.StringValue",
+    "google.protobuf.BytesValue",  "google.protobuf.FieldMask"};
+
+void DeleteWellKnownTypes() { delete well_known_types_; }
+
+void InitWellKnownTypes() {
+  well_known_types_ = new set<string>;
+  for (int i = 0; i < GOOGLE_ARRAYSIZE(well_known_types_name_array_); ++i) {
+    well_known_types_->insert(well_known_types_name_array_[i]);
+  }
+  google::protobuf::internal::OnShutdown(&DeleteWellKnownTypes);
+}
+
+bool IsWellKnownType(const string& type_name) {
+  InitWellKnownTypes();
+  return ContainsKey(*well_known_types_, type_name);
+}
+
+bool IsValidBoolString(const string& bool_string) {
+  return bool_string == "true" || bool_string == "false" ||
+         bool_string == "1" || bool_string == "0";
+}
+
+bool IsMap(const google::protobuf::Field& field,
+           const google::protobuf::Type& type) {
+  return (field.cardinality() ==
+              google::protobuf::Field_Cardinality_CARDINALITY_REPEATED &&
+          GetBoolOptionOrDefault(type.options(),
+                                 "google.protobuf.MessageOptions.map_entry", false));
+}
+
+bool IsMessageSetWireFormat(const google::protobuf::Type& type) {
+  return GetBoolOptionOrDefault(
+      type.options(), "google.protobuf.MessageOptions.message_set_wire_format", false);
+}
+
+string DoubleAsString(double value) {
+  if (MathLimits<double>::IsPosInf(value)) return "Infinity";
+  if (MathLimits<double>::IsNegInf(value)) return "-Infinity";
+  if (MathLimits<double>::IsNaN(value)) return "NaN";
+
+  return SimpleDtoa(value);
+}
+
+string FloatAsString(float value) {
+  if (MathLimits<float>::IsFinite(value)) return SimpleFtoa(value);
+  return DoubleAsString(value);
+}
+
+bool SafeStrToFloat(StringPiece str, float* value) {
+  double double_value;
+  if (!safe_strtod(str, &double_value)) {
+    return false;
+  }
+
+  if (MathLimits<double>::IsInf(double_value) ||
+      MathLimits<double>::IsNaN(double_value))
+    return false;
+
+  // Fail if the value is not representable in float.
+  if (double_value > std::numeric_limits<float>::max() ||
+      double_value < -std::numeric_limits<float>::max()) {
+    return false;
+  }
+
+  *value = static_cast<float>(double_value);
+  return true;
+}
+
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/internal/utility.h b/src/google/protobuf/util/internal/utility.h
new file mode 100644
index 0000000..33df8ed
--- /dev/null
+++ b/src/google/protobuf/util/internal/utility.h
@@ -0,0 +1,193 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_CONVERTER_UTILITY_H__
+#define GOOGLE_PROTOBUF_UTIL_CONVERTER_UTILITY_H__
+
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+#include <utility>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/repeated_field.h>
+#include <google/protobuf/stubs/stringpiece.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/status.h>
+#include <google/protobuf/stubs/statusor.h>
+
+
+namespace google {
+namespace protobuf {
+class Method;
+class Any;
+class Bool;
+class Option;
+class Field;
+class Type;
+class Enum;
+class EnumValue;
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace util {
+namespace converter {
+// Finds the tech option identified by option_name. Parses the boolean value and
+// returns it.
+// When the option with the given name is not found, default_value is returned.
+LIBPROTOBUF_EXPORT bool GetBoolOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, bool default_value);
+
+// Returns int64 option value. If the option isn't found, returns the
+// default_value.
+LIBPROTOBUF_EXPORT int64 GetInt64OptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, int64 default_value);
+
+// Returns double option value. If the option isn't found, returns the
+// default_value.
+LIBPROTOBUF_EXPORT double GetDoubleOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, double default_value);
+
+// Returns string option value. If the option isn't found, returns the
+// default_value.
+LIBPROTOBUF_EXPORT string GetStringOptionOrDefault(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name, const string& default_value);
+
+// Returns a boolean value contained in Any type.
+// TODO(skarvaje): Make these utilities dealing with Any types more generic,
+// add more error checking and move to a more public/sharable location so others
+// can use.
+LIBPROTOBUF_EXPORT bool GetBoolFromAny(const google::protobuf::Any& any);
+
+// Returns int64 value contained in Any type.
+LIBPROTOBUF_EXPORT int64 GetInt64FromAny(const google::protobuf::Any& any);
+
+// Returns double value contained in Any type.
+LIBPROTOBUF_EXPORT double GetDoubleFromAny(const google::protobuf::Any& any);
+
+// Returns string value contained in Any type.
+LIBPROTOBUF_EXPORT string GetStringFromAny(const google::protobuf::Any& any);
+
+// Returns the type string without the url prefix. e.g.: If the passed type is
+// 'type.googleapis.com/tech.type.Bool', the returned value is 'tech.type.Bool'.
+LIBPROTOBUF_EXPORT const StringPiece GetTypeWithoutUrl(StringPiece type_url);
+
+// Returns the simple_type with the base type url (kTypeServiceBaseUrl)
+// prefixed.
+//
+// E.g:
+// GetFullTypeWithUrl("google.protobuf.Timestamp") returns the string
+// "type.googleapis.com/google.protobuf.Timestamp".
+LIBPROTOBUF_EXPORT const string GetFullTypeWithUrl(StringPiece simple_type);
+
+// Finds and returns option identified by name and option_name within the
+// provided map. Returns NULL if none found.
+const google::protobuf::Option* FindOptionOrNull(
+    const google::protobuf::RepeatedPtrField<google::protobuf::Option>& options,
+    const string& option_name);
+
+// Finds and returns the field identified by field_name in the passed tech Type
+// object. Returns NULL if none found.
+const google::protobuf::Field* FindFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece field_name);
+
+// Similar to FindFieldInTypeOrNull, but this looks up fields with given
+// json_name.
+const google::protobuf::Field* FindJsonFieldInTypeOrNull(
+    const google::protobuf::Type* type, StringPiece json_name);
+
+// Finds and returns the EnumValue identified by enum_name in the passed tech
+// Enum object. Returns NULL if none found.
+const google::protobuf::EnumValue* FindEnumValueByNameOrNull(
+    const google::protobuf::Enum* enum_type, StringPiece enum_name);
+
+// Finds and returns the EnumValue identified by value in the passed tech
+// Enum object. Returns NULL if none found.
+const google::protobuf::EnumValue* FindEnumValueByNumberOrNull(
+    const google::protobuf::Enum* enum_type, int32 value);
+
+// Converts input to camel-case and returns it.
+LIBPROTOBUF_EXPORT string ToCamelCase(const StringPiece input);
+
+// Converts input to snake_case and returns it.
+LIBPROTOBUF_EXPORT string ToSnakeCase(StringPiece input);
+
+// Returns true if type_name represents a well-known type.
+LIBPROTOBUF_EXPORT bool IsWellKnownType(const string& type_name);
+
+// Returns true if 'bool_string' represents a valid boolean value. Only "true",
+// "false", "0" and "1" are allowed.
+LIBPROTOBUF_EXPORT bool IsValidBoolString(const string& bool_string);
+
+// Returns true if "field" is a protobuf map field based on its type.
+LIBPROTOBUF_EXPORT bool IsMap(const google::protobuf::Field& field,
+           const google::protobuf::Type& type);
+
+// Returns true if the given type has special MessageSet wire format.
+bool IsMessageSetWireFormat(const google::protobuf::Type& type);
+
+// Infinity/NaN-aware conversion to string.
+LIBPROTOBUF_EXPORT string DoubleAsString(double value);
+LIBPROTOBUF_EXPORT string FloatAsString(float value);
+
+// Convert from int32, int64, uint32, uint64, double or float to string.
+template <typename T>
+string ValueAsString(T value) {
+  return SimpleItoa(value);
+}
+
+template <>
+inline string ValueAsString(float value) {
+  return FloatAsString(value);
+}
+
+template <>
+inline string ValueAsString(double value) {
+  return DoubleAsString(value);
+}
+
+// Converts a string to float. Unlike safe_strtof, conversion will fail if the
+// value fits into double but not float (e.g., DBL_MAX).
+LIBPROTOBUF_EXPORT bool SafeStrToFloat(StringPiece str, float* value);
+}  // namespace converter
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_CONVERTER_UTILITY_H__
diff --git a/src/google/protobuf/util/json_format_proto3.proto b/src/google/protobuf/util/json_format_proto3.proto
new file mode 100644
index 0000000..a1e24c1
--- /dev/null
+++ b/src/google/protobuf/util/json_format_proto3.proto
@@ -0,0 +1,176 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+syntax = "proto3";
+
+package proto3;
+
+
+import "google/protobuf/duration.proto";
+import "google/protobuf/timestamp.proto";
+import "google/protobuf/wrappers.proto";
+import "google/protobuf/struct.proto";
+import "google/protobuf/any.proto";
+import "google/protobuf/field_mask.proto";
+
+enum EnumType {
+  FOO = 0;
+  BAR = 1;
+}
+
+message MessageType {
+  int32 value = 1;
+}
+
+message TestMessage {
+  bool bool_value = 1;
+  int32 int32_value = 2;
+  int64 int64_value = 3;
+  uint32 uint32_value = 4;
+  uint64 uint64_value = 5;
+  float float_value = 6;
+  double double_value = 7;
+  string string_value = 8;
+  bytes bytes_value = 9;
+  EnumType enum_value = 10;
+  MessageType message_value = 11;
+
+  repeated bool repeated_bool_value = 21;
+  repeated int32 repeated_int32_value = 22;
+  repeated int64 repeated_int64_value = 23;
+  repeated uint32 repeated_uint32_value = 24;
+  repeated uint64 repeated_uint64_value = 25;
+  repeated float repeated_float_value = 26;
+  repeated double repeated_double_value = 27;
+  repeated string repeated_string_value = 28;
+  repeated bytes repeated_bytes_value = 29;
+  repeated EnumType repeated_enum_value = 30;
+  repeated MessageType repeated_message_value = 31;
+}
+
+message TestOneof {
+  // In JSON format oneof fields behave mostly the same as optional
+  // fields except that:
+  //   1. Oneof fields have field presence information and will be
+  //      printed if it's set no matter whether it's the default value.
+  //   2. Multiple oneof fields in the same oneof cannot appear at the
+  //      same time in the input.
+  oneof oneof_value {
+    int32 oneof_int32_value = 1;
+    string oneof_string_value = 2;
+    bytes oneof_bytes_value = 3;
+    EnumType oneof_enum_value = 4;
+    MessageType oneof_message_value = 5;
+  }
+}
+
+message TestMap {
+  map<bool, int32> bool_map = 1;
+  map<int32, int32> int32_map = 2;
+  map<int64, int32> int64_map = 3;
+  map<uint32, int32> uint32_map = 4;
+  map<uint64, int32> uint64_map = 5;
+  map<string, int32> string_map = 6;
+}
+
+message TestNestedMap {
+  map<bool, int32> bool_map = 1;
+  map<int32, int32> int32_map = 2;
+  map<int64, int32> int64_map = 3;
+  map<uint32, int32> uint32_map = 4;
+  map<uint64, int32> uint64_map = 5;
+  map<string, int32> string_map = 6;
+  map<string, TestNestedMap> map_map = 7;
+}
+
+message TestWrapper {
+  google.protobuf.BoolValue bool_value = 1;
+  google.protobuf.Int32Value int32_value = 2;
+  google.protobuf.Int64Value int64_value = 3;
+  google.protobuf.UInt32Value uint32_value = 4;
+  google.protobuf.UInt64Value uint64_value = 5;
+  google.protobuf.FloatValue float_value = 6;
+  google.protobuf.DoubleValue double_value = 7;
+  google.protobuf.StringValue string_value = 8;
+  google.protobuf.BytesValue bytes_value = 9;
+
+  repeated google.protobuf.BoolValue repeated_bool_value = 11;
+  repeated google.protobuf.Int32Value repeated_int32_value = 12;
+  repeated google.protobuf.Int64Value repeated_int64_value = 13;
+  repeated google.protobuf.UInt32Value repeated_uint32_value = 14;
+  repeated google.protobuf.UInt64Value repeated_uint64_value = 15;
+  repeated google.protobuf.FloatValue repeated_float_value = 16;
+  repeated google.protobuf.DoubleValue repeated_double_value = 17;
+  repeated google.protobuf.StringValue repeated_string_value = 18;
+  repeated google.protobuf.BytesValue repeated_bytes_value = 19;
+}
+
+message TestTimestamp {
+  google.protobuf.Timestamp value = 1;
+  repeated google.protobuf.Timestamp repeated_value = 2;
+}
+
+message TestDuration {
+  google.protobuf.Duration value = 1;
+  repeated google.protobuf.Duration repeated_value = 2;
+}
+
+message TestFieldMask {
+  google.protobuf.FieldMask value = 1;
+}
+
+message TestStruct {
+  google.protobuf.Struct value = 1;
+  repeated google.protobuf.Struct repeated_value = 2;
+}
+
+message TestAny {
+  google.protobuf.Any value = 1;
+  repeated google.protobuf.Any repeated_value = 2;
+}
+
+message TestValue {
+  google.protobuf.Value value = 1;
+  repeated google.protobuf.Value repeated_value = 2;
+}
+
+message TestListValue {
+  google.protobuf.ListValue value = 1;
+  repeated google.protobuf.ListValue repeated_value = 2;
+}
+
+message TestBoolValue {
+  bool bool_value = 1;
+  map<bool, int32> bool_map = 2;
+}
+
+message TestCustomJsonName {
+  int32 value = 1 [json_name = "@value"];
+}
diff --git a/src/google/protobuf/util/json_util.cc b/src/google/protobuf/util/json_util.cc
new file mode 100644
index 0000000..c3b8d50
--- /dev/null
+++ b/src/google/protobuf/util/json_util.cc
@@ -0,0 +1,140 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/json_util.h>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/util/internal/default_value_objectwriter.h>
+#include <google/protobuf/util/internal/error_listener.h>
+#include <google/protobuf/util/internal/json_objectwriter.h>
+#include <google/protobuf/util/internal/json_stream_parser.h>
+#include <google/protobuf/util/internal/protostream_objectsource.h>
+#include <google/protobuf/util/internal/protostream_objectwriter.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/util/type_resolver_util.h>
+#include <google/protobuf/stubs/bytestream.h>
+#include <google/protobuf/stubs/status_macros.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+namespace internal {
+void ZeroCopyStreamByteSink::Append(const char* bytes, size_t len) {
+  while (len > 0) {
+    void* buffer;
+    int length;
+    if (!stream_->Next(&buffer, &length)) {
+      // There isn't a way for ByteSink to report errors.
+      return;
+    }
+    if (len < length) {
+      memcpy(buffer, bytes, len);
+      stream_->BackUp(length - len);
+      break;
+    } else {
+      memcpy(buffer, bytes, length);
+      bytes += length;
+      len -= length;
+    }
+  }
+}
+}  // namespace internal
+
+util::Status BinaryToJsonStream(TypeResolver* resolver,
+                                  const string& type_url,
+                                  io::ZeroCopyInputStream* binary_input,
+                                  io::ZeroCopyOutputStream* json_output,
+                                  const JsonOptions& options) {
+  io::CodedInputStream in_stream(binary_input);
+  google::protobuf::Type type;
+  RETURN_IF_ERROR(resolver->ResolveMessageType(type_url, &type));
+  converter::ProtoStreamObjectSource proto_source(&in_stream, resolver, type);
+  io::CodedOutputStream out_stream(json_output);
+  converter::JsonObjectWriter json_writer(options.add_whitespace ? " " : "",
+                                          &out_stream);
+  if (options.always_print_primitive_fields) {
+    converter::DefaultValueObjectWriter default_value_writer(
+        resolver, type, &json_writer);
+    return proto_source.WriteTo(&default_value_writer);
+  } else {
+    return proto_source.WriteTo(&json_writer);
+  }
+}
+
+util::Status BinaryToJsonString(TypeResolver* resolver,
+                                  const string& type_url,
+                                  const string& binary_input,
+                                  string* json_output,
+                                  const JsonOptions& options) {
+  io::ArrayInputStream input_stream(binary_input.data(), binary_input.size());
+  io::StringOutputStream output_stream(json_output);
+  return BinaryToJsonStream(resolver, type_url, &input_stream, &output_stream,
+                            options);
+}
+
+util::Status JsonToBinaryStream(TypeResolver* resolver,
+                                  const string& type_url,
+                                  io::ZeroCopyInputStream* json_input,
+                                  io::ZeroCopyOutputStream* binary_output) {
+  google::protobuf::Type type;
+  RETURN_IF_ERROR(resolver->ResolveMessageType(type_url, &type));
+  internal::ZeroCopyStreamByteSink sink(binary_output);
+  converter::NoopErrorListener listener;
+  converter::ProtoStreamObjectWriter proto_writer(resolver, type, &sink,
+                                                  &listener);
+
+  converter::JsonStreamParser parser(&proto_writer);
+  const void* buffer;
+  int length;
+  while (json_input->Next(&buffer, &length)) {
+    if (length == 0) continue;
+    RETURN_IF_ERROR(
+        parser.Parse(StringPiece(static_cast<const char*>(buffer), length)));
+  }
+  RETURN_IF_ERROR(parser.FinishParse());
+
+  return util::Status::OK;
+}
+
+util::Status JsonToBinaryString(TypeResolver* resolver,
+                                  const string& type_url,
+                                  const string& json_input,
+                                  string* binary_output) {
+  io::ArrayInputStream input_stream(json_input.data(), json_input.size());
+  io::StringOutputStream output_stream(binary_output);
+  return JsonToBinaryStream(resolver, type_url, &input_stream, &output_stream);
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/json_util.h b/src/google/protobuf/util/json_util.h
new file mode 100644
index 0000000..1718bfb
--- /dev/null
+++ b/src/google/protobuf/util/json_util.h
@@ -0,0 +1,136 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Utility functions to convert between protobuf binary format and proto3 JSON
+// format.
+#ifndef GOOGLE_PROTOBUF_UTIL_JSON_UTIL_H__
+#define GOOGLE_PROTOBUF_UTIL_JSON_UTIL_H__
+
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/bytestream.h>
+
+namespace google {
+namespace protobuf {
+namespace io {
+class ZeroCopyInputStream;
+class ZeroCopyOutputStream;
+}  // namespace io
+namespace util {
+
+struct JsonOptions {
+  // Whether to add spaces, line breaks and indentation to make the JSON output
+  // easy to read.
+  bool add_whitespace;
+  // Whether to always print primitive fields. By default primitive fields with
+  // default values will be omitted in JSON joutput. For example, an int32 field
+  // set to 0 will be omitted. Set this flag to true will override the default
+  // behavior and print primitive fields regardless of their values.
+  bool always_print_primitive_fields;
+
+  JsonOptions() : add_whitespace(false),
+                  always_print_primitive_fields(false) {
+  }
+};
+
+// Converts protobuf binary data to JSON.
+// The conversion will fail if:
+//   1. TypeResolver fails to resolve a type.
+//   2. input is not valid protobuf wire format, or conflicts with the type
+//      information returned by TypeResolver.
+// Note that unknown fields will be discarded silently.
+util::Status BinaryToJsonStream(
+    TypeResolver* resolver,
+    const string& type_url,
+    io::ZeroCopyInputStream* binary_input,
+    io::ZeroCopyOutputStream* json_output,
+    const JsonOptions& options);
+
+inline util::Status BinaryToJsonStream(
+    TypeResolver* resolver, const string& type_url,
+    io::ZeroCopyInputStream* binary_input,
+    io::ZeroCopyOutputStream* json_output) {
+  return BinaryToJsonStream(resolver, type_url, binary_input, json_output,
+                            JsonOptions());
+}
+
+LIBPROTOBUF_EXPORT util::Status BinaryToJsonString(
+    TypeResolver* resolver,
+    const string& type_url,
+    const string& binary_input,
+    string* json_output,
+    const JsonOptions& options);
+
+inline util::Status BinaryToJsonString(TypeResolver* resolver,
+                                         const string& type_url,
+                                         const string& binary_input,
+                                         string* json_output) {
+  return BinaryToJsonString(resolver, type_url, binary_input, json_output,
+                            JsonOptions());
+}
+
+// Converts JSON data to protobuf binary format.
+// The conversion will fail if:
+//   1. TypeResolver fails to resolve a type.
+//   2. input is not valid JSON format, or conflicts with the type
+//      information returned by TypeResolver.
+//   3. input has unknown fields.
+util::Status JsonToBinaryStream(
+    TypeResolver* resolver,
+    const string& type_url,
+    io::ZeroCopyInputStream* json_input,
+    io::ZeroCopyOutputStream* binary_output);
+
+LIBPROTOBUF_EXPORT util::Status JsonToBinaryString(
+    TypeResolver* resolver,
+    const string& type_url,
+    const string& json_input,
+    string* binary_output);
+
+namespace internal {
+// Internal helper class. Put in the header so we can write unit-tests for it.
+class LIBPROTOBUF_EXPORT ZeroCopyStreamByteSink : public strings::ByteSink {
+ public:
+  explicit ZeroCopyStreamByteSink(io::ZeroCopyOutputStream* stream)
+      : stream_(stream) {}
+
+  virtual void Append(const char* bytes, size_t len);
+
+ private:
+  io::ZeroCopyOutputStream* stream_;
+
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(ZeroCopyStreamByteSink);
+};
+}  // namespace internal
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_JSON_UTIL_H__
diff --git a/src/google/protobuf/util/json_util_test.cc b/src/google/protobuf/util/json_util_test.cc
new file mode 100644
index 0000000..da68495
--- /dev/null
+++ b/src/google/protobuf/util/json_util_test.cc
@@ -0,0 +1,289 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/json_util.h>
+
+#include <list>
+#include <string>
+
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/util/json_format_proto3.pb.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/util/type_resolver_util.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+
+using proto3::FOO;
+using proto3::BAR;
+using proto3::TestMessage;
+using proto3::TestMap;
+
+static const char kTypeUrlPrefix[] = "type.googleapis.com";
+
+static string GetTypeUrl(const Descriptor* message) {
+  return string(kTypeUrlPrefix) + "/" + message->full_name();
+}
+
+// As functions defined in json_util.h are just thin wrappers around the
+// JSON conversion code in //net/proto2/util/converter, in this test we
+// only cover some very basic cases to make sure the wrappers have forwarded
+// parameters to the underlying implementation correctly. More detailed
+// tests are contained in the //net/proto2/util/converter directory.
+class JsonUtilTest : public testing::Test {
+ protected:
+  JsonUtilTest() {
+    resolver_.reset(NewTypeResolverForDescriptorPool(
+        kTypeUrlPrefix, DescriptorPool::generated_pool()));
+  }
+
+  string ToJson(const Message& message, const JsonOptions& options) {
+    string result;
+    GOOGLE_CHECK_OK(BinaryToJsonString(resolver_.get(),
+                                GetTypeUrl(message.GetDescriptor()),
+                                message.SerializeAsString(), &result, options));
+    return result;
+  }
+
+  bool FromJson(const string& json, Message* message) {
+    string binary;
+    GOOGLE_CHECK_OK(JsonToBinaryString(
+        resolver_.get(), GetTypeUrl(message->GetDescriptor()), json, &binary));
+    return message->ParseFromString(binary);
+  }
+
+  google::protobuf::scoped_ptr<TypeResolver> resolver_;
+};
+
+TEST_F(JsonUtilTest, TestWhitespaces) {
+  TestMessage m;
+  m.mutable_message_value();
+
+  JsonOptions options;
+  EXPECT_EQ("{\"messageValue\":{}}", ToJson(m, options));
+  options.add_whitespace = true;
+  EXPECT_EQ(
+      "{\n"
+      " \"messageValue\": {}\n"
+      "}\n",
+      ToJson(m, options));
+}
+
+// TODO(skarvaje): Uncomment after cl/96232915 is submitted.
+// TEST_F(JsonUtilTest, TestDefaultValues) {
+  // TestMessage m;
+  // JsonOptions options;
+  // EXPECT_EQ("{}", ToJson(m, options));
+  // options.always_print_primitive_fields = true;
+  // EXPECT_EQ(
+      // "{\"boolValue\":false,"
+      // "\"int32Value\":0,"
+      // "\"int64Value\":\"0\","
+      // "\"uint32Value\":0,"
+      // "\"uint64Value\":\"0\","
+      // "\"floatValue\":0,"
+      // "\"doubleValue\":0,"
+      // "\"stringValue\":\"\","
+      // "\"bytesValue\":\"\","
+      // // TODO(xiaofeng): The default enum value should be FOO. I believe
+      // // this is a bug in DefaultValueObjectWriter.
+      // "\"enumValue\":null"
+      // "}",
+      // ToJson(m, options));
+// }
+
+TEST_F(JsonUtilTest, ParseMessage) {
+  // Some random message but good enough to verify that the parsing warpper
+  // functions are working properly.
+  string input =
+      "{\n"
+      "  \"int32Value\": 1024,\n"
+      "  \"repeatedInt32Value\": [1, 2],\n"
+      "  \"messageValue\": {\n"
+      "    \"value\": 2048\n"
+      "  },\n"
+      "  \"repeatedMessageValue\": [\n"
+      "    {\"value\": 40}, {\"value\": 96}\n"
+      "  ]\n"
+      "}\n";
+  TestMessage m;
+  ASSERT_TRUE(FromJson(input, &m));
+  EXPECT_EQ(1024, m.int32_value());
+  ASSERT_EQ(2, m.repeated_int32_value_size());
+  EXPECT_EQ(1, m.repeated_int32_value(0));
+  EXPECT_EQ(2, m.repeated_int32_value(1));
+  EXPECT_EQ(2048, m.message_value().value());
+  ASSERT_EQ(2, m.repeated_message_value_size());
+  EXPECT_EQ(40, m.repeated_message_value(0).value());
+  EXPECT_EQ(96, m.repeated_message_value(1).value());
+}
+
+TEST_F(JsonUtilTest, ParseMap) {
+  TestMap message;
+  (*message.mutable_string_map())["hello"] = 1234;
+  JsonOptions options;
+  EXPECT_EQ("{\"stringMap\":{\"hello\":1234}}", ToJson(message, options));
+  TestMap other;
+  ASSERT_TRUE(FromJson(ToJson(message, options), &other));
+  EXPECT_EQ(message.DebugString(), other.DebugString());
+}
+
+typedef pair<char*, int> Segment;
+// A ZeroCopyOutputStream that writes to multiple buffers.
+class SegmentedZeroCopyOutputStream : public io::ZeroCopyOutputStream {
+ public:
+  explicit SegmentedZeroCopyOutputStream(list<Segment> segments)
+      : segments_(segments), last_segment_(static_cast<char*>(NULL), 0), byte_count_(0) {}
+
+  virtual bool Next(void** buffer, int* length) {
+    if (segments_.empty()) {
+      return false;
+    }
+    last_segment_ = segments_.front();
+    segments_.pop_front();
+    *buffer = last_segment_.first;
+    *length = last_segment_.second;
+    byte_count_ += *length;
+    return true;
+  }
+
+  virtual void BackUp(int length) {
+    GOOGLE_CHECK(length <= last_segment_.second);
+    segments_.push_front(
+        Segment(last_segment_.first + last_segment_.second - length, length));
+    last_segment_ = Segment(last_segment_.first, last_segment_.second - length);
+    byte_count_ -= length;
+  }
+
+  virtual int64 ByteCount() const { return byte_count_; }
+
+ private:
+  list<Segment> segments_;
+  Segment last_segment_;
+  int64 byte_count_;
+};
+
+// This test splits the output buffer and also the input data into multiple
+// segments and checks that the implementation of ZeroCopyStreamByteSink
+// handles all possible cases correctly.
+TEST(ZeroCopyStreamByteSinkTest, TestAllInputOutputPatterns) {
+  static const int kOutputBufferLength = 10;
+  // An exhaustive test takes too long, skip some combinations to make the test
+  // run faster.
+  static const int kSkippedPatternCount = 7;
+
+  char buffer[kOutputBufferLength];
+  for (int split_pattern = 0; split_pattern < (1 << (kOutputBufferLength - 1));
+       split_pattern += kSkippedPatternCount) {
+    // Split the buffer into small segments according to the split_pattern.
+    list<Segment> segments;
+    int segment_start = 0;
+    for (int i = 0; i < kOutputBufferLength - 1; ++i) {
+      if (split_pattern & (1 << i)) {
+        segments.push_back(
+            Segment(buffer + segment_start, i - segment_start + 1));
+        segment_start = i + 1;
+      }
+    }
+    segments.push_back(
+        Segment(buffer + segment_start, kOutputBufferLength - segment_start));
+
+    // Write exactly 10 bytes through the ByteSink.
+    string input_data = "0123456789";
+    for (int input_pattern = 0; input_pattern < (1 << (input_data.size() - 1));
+         input_pattern += kSkippedPatternCount) {
+      memset(buffer, 0, sizeof(buffer));
+      {
+        SegmentedZeroCopyOutputStream output_stream(segments);
+        internal::ZeroCopyStreamByteSink byte_sink(&output_stream);
+        int start = 0;
+        for (int j = 0; j < input_data.length() - 1; ++j) {
+          if (input_pattern & (1 << j)) {
+            byte_sink.Append(&input_data[start], j - start + 1);
+            start = j + 1;
+          }
+        }
+        byte_sink.Append(&input_data[start], input_data.length() - start);
+      }
+      EXPECT_EQ(input_data, string(buffer, input_data.length()));
+    }
+
+    // Write only 9 bytes through the ByteSink.
+    input_data = "012345678";
+    for (int input_pattern = 0; input_pattern < (1 << (input_data.size() - 1));
+         input_pattern += kSkippedPatternCount) {
+      memset(buffer, 0, sizeof(buffer));
+      {
+        SegmentedZeroCopyOutputStream output_stream(segments);
+        internal::ZeroCopyStreamByteSink byte_sink(&output_stream);
+        int start = 0;
+        for (int j = 0; j < input_data.length() - 1; ++j) {
+          if (input_pattern & (1 << j)) {
+            byte_sink.Append(&input_data[start], j - start + 1);
+            start = j + 1;
+          }
+        }
+        byte_sink.Append(&input_data[start], input_data.length() - start);
+      }
+      EXPECT_EQ(input_data, string(buffer, input_data.length()));
+      EXPECT_EQ(0, buffer[input_data.length()]);
+    }
+
+    // Write 11 bytes through the ByteSink. The extra byte will just
+    // be ignored.
+    input_data = "0123456789A";
+    for (int input_pattern = 0; input_pattern < (1 << (input_data.size() - 1));
+         input_pattern += kSkippedPatternCount) {
+      memset(buffer, 0, sizeof(buffer));
+      {
+        SegmentedZeroCopyOutputStream output_stream(segments);
+        internal::ZeroCopyStreamByteSink byte_sink(&output_stream);
+        int start = 0;
+        for (int j = 0; j < input_data.length() - 1; ++j) {
+          if (input_pattern & (1 << j)) {
+            byte_sink.Append(&input_data[start], j - start + 1);
+            start = j + 1;
+          }
+        }
+        byte_sink.Append(&input_data[start], input_data.length() - start);
+      }
+      EXPECT_EQ(input_data.substr(0, kOutputBufferLength),
+                string(buffer, kOutputBufferLength));
+    }
+  }
+}
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/message_differencer.cc b/src/google/protobuf/util/message_differencer.cc
new file mode 100644
index 0000000..0f879dc
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer.cc
@@ -0,0 +1,1686 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file defines static methods and classes for comparing Protocol
+// Messages (see //google/protobuf/util/message_differencer.h for more
+// information).
+
+#include <google/protobuf/util/message_differencer.h>
+
+#include <algorithm>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <utility>
+
+#include <google/protobuf/stubs/callback.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/any.h>
+#include <google/protobuf/io/printer.h>
+#include <google/protobuf/io/zero_copy_stream.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/dynamic_message.h>
+#include <google/protobuf/text_format.h>
+#include <google/protobuf/util/field_comparator.h>
+#include <google/protobuf/stubs/strutil.h>
+
+namespace google {
+namespace protobuf {
+
+namespace util {
+
+// When comparing a repeated field as map, MultipleFieldMapKeyComparator can
+// be used to specify multiple fields as key for key comparison.
+// Two elements of a repeated field will be regarded as having the same key
+// iff they have the same value for every specified key field.
+// Note that you can also specify only one field as key.
+class MessageDifferencer::MultipleFieldsMapKeyComparator
+    : public MessageDifferencer::MapKeyComparator {
+ public:
+  MultipleFieldsMapKeyComparator(
+      MessageDifferencer* message_differencer,
+      const vector<vector<const FieldDescriptor*> >& key_field_paths)
+        : message_differencer_(message_differencer),
+          key_field_paths_(key_field_paths) {
+    GOOGLE_CHECK(!key_field_paths_.empty());
+    for (int i = 0; i < key_field_paths_.size(); ++i) {
+      GOOGLE_CHECK(!key_field_paths_[i].empty());
+    }
+  }
+  MultipleFieldsMapKeyComparator(
+      MessageDifferencer* message_differencer,
+      const FieldDescriptor* key)
+        : message_differencer_(message_differencer) {
+    vector<const FieldDescriptor*> key_field_path;
+    key_field_path.push_back(key);
+    key_field_paths_.push_back(key_field_path);
+  }
+  virtual bool IsMatch(
+      const Message& message1,
+      const Message& message2,
+      const vector<SpecificField>& parent_fields) const {
+    for (int i = 0; i < key_field_paths_.size(); ++i) {
+      if (!IsMatchInternal(message1, message2, parent_fields,
+                           key_field_paths_[i], 0)) {
+        return false;
+      }
+    }
+    return true;
+  }
+ private:
+  bool IsMatchInternal(
+      const Message& message1,
+      const Message& message2,
+      const vector<SpecificField>& parent_fields,
+      const vector<const FieldDescriptor*>& key_field_path,
+      int path_index) const {
+    const FieldDescriptor* field = key_field_path[path_index];
+    vector<SpecificField> current_parent_fields(parent_fields);
+    if (path_index == key_field_path.size() - 1) {
+      if (field->is_repeated()) {
+        if (!message_differencer_->CompareRepeatedField(
+            message1, message2, field, &current_parent_fields)) {
+          return false;
+        }
+      } else {
+        if (!message_differencer_->CompareFieldValueUsingParentFields(
+            message1, message2, field, -1, -1, &current_parent_fields)) {
+          return false;
+        }
+      }
+      return true;
+    } else {
+      const Reflection* reflection1 = message1.GetReflection();
+      const Reflection* reflection2 = message2.GetReflection();
+      bool has_field1 = reflection1->HasField(message1, field);
+      bool has_field2 = reflection2->HasField(message2, field);
+      if (!has_field1 && !has_field2) {
+        return true;
+      }
+      if (has_field1 != has_field2) {
+        return false;
+      }
+      SpecificField specific_field;
+      specific_field.field = field;
+      current_parent_fields.push_back(specific_field);
+      return IsMatchInternal(
+          reflection1->GetMessage(message1, field),
+          reflection2->GetMessage(message2, field),
+          current_parent_fields,
+          key_field_path,
+          path_index + 1);
+    }
+  }
+  MessageDifferencer* message_differencer_;
+  vector<vector<const FieldDescriptor*> > key_field_paths_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MultipleFieldsMapKeyComparator);
+};
+
+bool MessageDifferencer::Equals(const Message& message1,
+                                const Message& message2) {
+  MessageDifferencer differencer;
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::Equivalent(const Message& message1,
+                                    const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_message_field_comparison(MessageDifferencer::EQUIVALENT);
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::ApproximatelyEquals(const Message& message1,
+                                             const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_float_comparison(
+      MessageDifferencer::APPROXIMATE);
+
+  return differencer.Compare(message1, message2);
+}
+
+bool MessageDifferencer::ApproximatelyEquivalent(const Message& message1,
+                                                 const Message& message2) {
+  MessageDifferencer differencer;
+  differencer.set_message_field_comparison(MessageDifferencer::EQUIVALENT);
+  differencer.set_float_comparison(MessageDifferencer::APPROXIMATE);
+
+  return differencer.Compare(message1, message2);
+}
+
+// ===========================================================================
+
+MessageDifferencer::MessageDifferencer()
+    : reporter_(NULL),
+      field_comparator_(NULL),
+      message_field_comparison_(EQUAL),
+      scope_(FULL),
+      repeated_field_comparison_(AS_LIST),
+      report_matches_(false),
+      output_string_(NULL) { }
+
+MessageDifferencer::~MessageDifferencer() {
+  for (int i = 0; i < owned_key_comparators_.size(); ++i) {
+    delete owned_key_comparators_[i];
+  }
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    delete ignore_criteria_[i];
+  }
+}
+
+void MessageDifferencer::set_field_comparator(FieldComparator* comparator) {
+  GOOGLE_CHECK(comparator) << "Field comparator can't be NULL.";
+  field_comparator_ = comparator;
+}
+
+void MessageDifferencer::set_message_field_comparison(
+    MessageFieldComparison comparison) {
+  message_field_comparison_ = comparison;
+}
+
+void MessageDifferencer::set_scope(Scope scope) {
+  scope_ = scope;
+}
+
+MessageDifferencer::Scope MessageDifferencer::scope() {
+  return scope_;
+}
+
+void MessageDifferencer::set_float_comparison(FloatComparison comparison) {
+  default_field_comparator_.set_float_comparison(
+      comparison == EXACT ?
+      DefaultFieldComparator::EXACT : DefaultFieldComparator::APPROXIMATE);
+}
+
+void MessageDifferencer::set_repeated_field_comparison(
+    RepeatedFieldComparison comparison) {
+  repeated_field_comparison_ = comparison;
+}
+
+void MessageDifferencer::TreatAsSet(const FieldDescriptor* field) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(field);
+  GOOGLE_CHECK(key_comparator == NULL)
+      << "Cannot treat this repeated field as both Map and Set for"
+      << " comparison.  Field name is: " << field->full_name();
+  GOOGLE_CHECK(list_fields_.find(field) == list_fields_.end())
+      << "Cannot treat the same field as both SET and LIST. Field name is: "
+      << field->full_name();
+  set_fields_.insert(field);
+}
+
+void MessageDifferencer::TreatAsList(const FieldDescriptor* field) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                              << field->full_name();
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(field);
+  GOOGLE_CHECK(key_comparator == NULL)
+      << "Cannot treat this repeated field as both Map and Set for"
+      << " comparison.  Field name is: " << field->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat the same field as both SET and LIST. Field name is: "
+      << field->full_name();
+  list_fields_.insert(field);
+}
+
+void MessageDifferencer::TreatAsMap(const FieldDescriptor* field,
+                                    const FieldDescriptor* key) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  GOOGLE_CHECK(key->containing_type() == field->message_type())
+      << key->full_name()
+      << " must be a direct subfield within the repeated field "
+      << field->full_name() << ", not " << key->containing_type()->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  GOOGLE_CHECK(list_fields_.find(field) == list_fields_.end())
+      << "Cannot treat this repeated field as both Map and List for "
+      << "comparison.";
+  MapKeyComparator* key_comparator =
+      new MultipleFieldsMapKeyComparator(this, key);
+  owned_key_comparators_.push_back(key_comparator);
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::TreatAsMapWithMultipleFieldsAsKey(
+    const FieldDescriptor* field,
+    const vector<const FieldDescriptor*>& key_fields) {
+  vector<vector<const FieldDescriptor*> > key_field_paths;
+  for (int i = 0; i < key_fields.size(); ++i) {
+    vector<const FieldDescriptor*> key_field_path;
+    key_field_path.push_back(key_fields[i]);
+    key_field_paths.push_back(key_field_path);
+  }
+  TreatAsMapWithMultipleFieldPathsAsKey(field, key_field_paths);
+}
+
+void MessageDifferencer::TreatAsMapWithMultipleFieldPathsAsKey(
+    const FieldDescriptor* field,
+    const vector<vector<const FieldDescriptor*> >& key_field_paths) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                              << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  for (int i = 0; i < key_field_paths.size(); ++i) {
+    const vector<const FieldDescriptor*>& key_field_path = key_field_paths[i];
+    for (int j = 0; j < key_field_path.size(); ++j) {
+      const FieldDescriptor* parent_field =
+          j == 0 ? field : key_field_path[j - 1];
+      const FieldDescriptor* child_field = key_field_path[j];
+      GOOGLE_CHECK(child_field->containing_type() == parent_field->message_type())
+          << child_field->full_name()
+          << " must be a direct subfield within the field: "
+          << parent_field->full_name();
+      if (j != 0) {
+        GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, parent_field->cpp_type())
+            << parent_field->full_name() << " has to be of type message.";
+        GOOGLE_CHECK(!parent_field->is_repeated())
+            << parent_field->full_name() << " cannot be a repeated field.";
+      }
+    }
+  }
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  MapKeyComparator* key_comparator =
+      new MultipleFieldsMapKeyComparator(this, key_field_paths);
+  owned_key_comparators_.push_back(key_comparator);
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::TreatAsMapUsingKeyComparator(
+    const FieldDescriptor* field,
+    const MapKeyComparator* key_comparator) {
+  GOOGLE_CHECK(field->is_repeated()) << "Field must be repeated: "
+                               << field->full_name();
+  GOOGLE_CHECK_EQ(FieldDescriptor::CPPTYPE_MESSAGE, field->cpp_type())
+      << "Field has to be message type.  Field name is: "
+      << field->full_name();
+  GOOGLE_CHECK(set_fields_.find(field) == set_fields_.end())
+      << "Cannot treat this repeated field as both Map and Set for "
+      << "comparison.";
+  map_field_key_comparator_[field] = key_comparator;
+}
+
+void MessageDifferencer::AddIgnoreCriteria(IgnoreCriteria* ignore_criteria) {
+  ignore_criteria_.push_back(ignore_criteria);
+}
+
+void MessageDifferencer::IgnoreField(const FieldDescriptor* field) {
+  ignored_fields_.insert(field);
+}
+
+void MessageDifferencer::SetFractionAndMargin(const FieldDescriptor* field,
+                                              double fraction, double margin) {
+  default_field_comparator_.SetFractionAndMargin(field, fraction, margin);
+}
+
+void MessageDifferencer::ReportDifferencesToString(string* output) {
+  GOOGLE_DCHECK(output) << "Specified output string was NULL";
+
+  output_string_ = output;
+  output_string_->clear();
+}
+
+void MessageDifferencer::ReportDifferencesTo(Reporter* reporter) {
+  // If an output string is set, clear it to prevent
+  // it superceding the specified reporter.
+  if (output_string_) {
+    output_string_ = NULL;
+  }
+
+  reporter_ = reporter;
+}
+
+bool MessageDifferencer::FieldBefore(const FieldDescriptor* field1,
+                                     const FieldDescriptor* field2) {
+  // Handle sentinel values (i.e. make sure NULLs are always ordered
+  // at the end of the list).
+  if (field1 == NULL) {
+    return false;
+  }
+
+  if (field2 == NULL) {
+    return true;
+  }
+
+  // Always order fields by their tag number
+  return (field1->number() < field2->number());
+}
+
+bool MessageDifferencer::Compare(const Message& message1,
+                                 const Message& message2) {
+  vector<SpecificField> parent_fields;
+
+  bool result = false;
+
+  // Setup the internal reporter if need be.
+  if (output_string_) {
+    io::StringOutputStream output_stream(output_string_);
+    StreamReporter reporter(&output_stream);
+    reporter_ = &reporter;
+    result = Compare(message1, message2, &parent_fields);
+    reporter_ = NULL;
+  } else {
+    result = Compare(message1, message2, &parent_fields);
+  }
+
+  return result;
+}
+
+bool MessageDifferencer::CompareWithFields(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields_arg,
+    const vector<const FieldDescriptor*>& message2_fields_arg) {
+  if (message1.GetDescriptor() != message2.GetDescriptor()) {
+    GOOGLE_LOG(DFATAL) << "Comparison between two messages with different "
+                << "descriptors.";
+    return false;
+  }
+
+  vector<SpecificField> parent_fields;
+
+  bool result = false;
+
+  vector<const FieldDescriptor*> message1_fields(message1_fields_arg);
+  vector<const FieldDescriptor*> message2_fields(message2_fields_arg);
+
+  std::sort(message1_fields.begin(), message1_fields.end(), FieldBefore);
+  std::sort(message2_fields.begin(), message2_fields.end(), FieldBefore);
+  // Append NULL sentinel values.
+  message1_fields.push_back(NULL);
+  message2_fields.push_back(NULL);
+
+  // Setup the internal reporter if need be.
+  if (output_string_) {
+    io::StringOutputStream output_stream(output_string_);
+    StreamReporter reporter(&output_stream);
+    reporter_ = &reporter;
+    result = CompareRequestedFieldsUsingSettings(
+        message1, message2, message1_fields, message2_fields, &parent_fields);
+    reporter_ = NULL;
+  } else {
+    result = CompareRequestedFieldsUsingSettings(
+        message1, message2, message1_fields, message2_fields, &parent_fields);
+  }
+
+  return result;
+}
+
+bool MessageDifferencer::Compare(
+    const Message& message1,
+    const Message& message2,
+    vector<SpecificField>* parent_fields) {
+  const Descriptor* descriptor1 = message1.GetDescriptor();
+  const Descriptor* descriptor2 = message2.GetDescriptor();
+  if (descriptor1 != descriptor2) {
+    GOOGLE_LOG(DFATAL) << "Comparison between two messages with different "
+                << "descriptors.";
+    return false;
+  }
+  // Expand google.protobuf.Any payload if possible.
+  if (descriptor1->full_name() == internal::kAnyFullTypeName) {
+    google::protobuf::scoped_ptr<Message> data1;
+    google::protobuf::scoped_ptr<Message> data2;
+    if (UnpackAny(message1, &data1) && UnpackAny(message2, &data2)) {
+      return Compare(*data1, *data2, parent_fields);
+    }
+  }
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+
+  // Retrieve all the set fields, including extensions.
+  vector<const FieldDescriptor*> message1_fields;
+  vector<const FieldDescriptor*> message2_fields;
+
+  reflection1->ListFields(message1, &message1_fields);
+  reflection2->ListFields(message2, &message2_fields);
+
+  // Add sentinel values to deal with the
+  // case where the number of the fields in
+  // each list are different.
+  message1_fields.push_back(NULL);
+  message2_fields.push_back(NULL);
+
+  bool unknown_compare_result = true;
+  // Ignore unknown fields in EQUIVALENT mode
+  if (message_field_comparison_ != EQUIVALENT) {
+    const google::protobuf::UnknownFieldSet* unknown_field_set1 =
+        &reflection1->GetUnknownFields(message1);
+    const google::protobuf::UnknownFieldSet* unknown_field_set2 =
+        &reflection2->GetUnknownFields(message2);
+    if (!CompareUnknownFields(message1, message2,
+                              *unknown_field_set1, *unknown_field_set2,
+                              parent_fields)) {
+      if (reporter_ == NULL) {
+        return false;
+      };
+      unknown_compare_result = false;
+    }
+  }
+
+  return CompareRequestedFieldsUsingSettings(
+      message1, message2,
+      message1_fields, message2_fields,
+      parent_fields) && unknown_compare_result;
+}
+
+bool MessageDifferencer::CompareRequestedFieldsUsingSettings(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields,
+    const vector<const FieldDescriptor*>& message2_fields,
+    vector<SpecificField>* parent_fields) {
+  if (scope_ == FULL) {
+    if (message_field_comparison_ == EQUIVALENT) {
+      // We need to merge the field lists of both messages (i.e.
+      // we are merely checking for a difference in field values,
+      // rather than the addition or deletion of fields).
+      vector<const FieldDescriptor*> fields_union;
+      CombineFields(message1_fields, FULL, message2_fields, FULL,
+                    &fields_union);
+      return CompareWithFieldsInternal(message1, message2, fields_union,
+                                       fields_union, parent_fields);
+    } else {
+      // Simple equality comparison, use the unaltered field lists.
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       message2_fields, parent_fields);
+    }
+  } else {
+    if (message_field_comparison_ == EQUIVALENT) {
+      // We use the list of fields for message1 for both messages when
+      // comparing.  This way, extra fields in message2 are ignored,
+      // and missing fields in message2 use their default value.
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       message1_fields, parent_fields);
+    } else {
+      // We need to consider the full list of fields for message1
+      // but only the intersection for message2.  This way, any fields
+      // only present in message2 will be ignored, but any fields only
+      // present in message1 will be marked as a difference.
+      vector<const FieldDescriptor*> fields_intersection;
+      CombineFields(message1_fields, PARTIAL, message2_fields, PARTIAL,
+                    &fields_intersection);
+      return CompareWithFieldsInternal(message1, message2, message1_fields,
+                                       fields_intersection, parent_fields);
+    }
+  }
+}
+
+void MessageDifferencer::CombineFields(
+    const vector<const FieldDescriptor*>& fields1,
+    Scope fields1_scope,
+    const vector<const FieldDescriptor*>& fields2,
+    Scope fields2_scope,
+    vector<const FieldDescriptor*>* combined_fields) {
+
+  int index1 = 0;
+  int index2 = 0;
+
+  while (index1 < fields1.size() && index2 < fields2.size()) {
+    const FieldDescriptor* field1 = fields1[index1];
+    const FieldDescriptor* field2 = fields2[index2];
+
+    if (FieldBefore(field1, field2)) {
+      if (fields1_scope == FULL) {
+        combined_fields->push_back(fields1[index1]);
+      }
+      ++index1;
+    } else if (FieldBefore(field2, field1)) {
+      if (fields2_scope == FULL) {
+        combined_fields->push_back(fields2[index2]);
+      }
+      ++index2;
+    } else {
+      combined_fields->push_back(fields1[index1]);
+      ++index1;
+      ++index2;
+    }
+  }
+}
+
+bool MessageDifferencer::CompareWithFieldsInternal(
+    const Message& message1,
+    const Message& message2,
+    const vector<const FieldDescriptor*>& message1_fields,
+    const vector<const FieldDescriptor*>& message2_fields,
+    vector<SpecificField>* parent_fields) {
+  bool isDifferent = false;
+  int field_index1 = 0;
+  int field_index2 = 0;
+
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+
+  while (true) {
+    const FieldDescriptor* field1 = message1_fields[field_index1];
+    const FieldDescriptor* field2 = message2_fields[field_index2];
+
+    // Once we have reached sentinel values, we are done the comparison.
+    if (field1 == NULL && field2 == NULL) {
+      break;
+    }
+
+    // Check for differences in the field itself.
+    if (FieldBefore(field1, field2)) {
+      // Field 1 is not in the field list for message 2.
+      if (IsIgnored(message1, message2, field1, *parent_fields)) {
+        // We are ignoring field1. Report the ignore and move on to
+        // the next field in message1_fields.
+        if (reporter_ != NULL) {
+          SpecificField specific_field;
+          specific_field.field = field1;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportIgnored(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+        ++field_index1;
+        continue;
+      }
+
+      if (reporter_ != NULL) {
+        int count = field1->is_repeated() ?
+            reflection1->FieldSize(message1, field1) : 1;
+
+        for (int i = 0; i < count; ++i) {
+          SpecificField specific_field;
+          specific_field.field = field1;
+          specific_field.index = field1->is_repeated() ? i : -1;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportDeleted(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+
+        isDifferent = true;
+      } else {
+        return false;
+      }
+
+      ++field_index1;
+      continue;
+    } else if (FieldBefore(field2, field1)) {
+      // Field 2 is not in the field list for message 1.
+      if (IsIgnored(message1, message2, field2, *parent_fields)) {
+        // We are ignoring field2. Report the ignore and move on to
+        // the next field in message2_fields.
+        if (reporter_ != NULL) {
+          SpecificField specific_field;
+          specific_field.field = field2;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportIgnored(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+        ++field_index2;
+        continue;
+      }
+
+      if (reporter_ != NULL) {
+        int count = field2->is_repeated() ?
+            reflection2->FieldSize(message2, field2) : 1;
+
+        for (int i = 0; i < count; ++i) {
+          SpecificField specific_field;
+          specific_field.field = field2;
+          specific_field.index = field2->is_repeated() ? i : -1;
+          specific_field.new_index = specific_field.index;
+
+          parent_fields->push_back(specific_field);
+          reporter_->ReportAdded(message1, message2, *parent_fields);
+          parent_fields->pop_back();
+        }
+
+        isDifferent = true;
+      } else {
+        return false;
+      }
+
+      ++field_index2;
+      continue;
+    }
+
+    // By this point, field1 and field2 are guarenteed to point to the same
+    // field, so we can now compare the values.
+    if (IsIgnored(message1, message2, field1, *parent_fields)) {
+      // Ignore this field. Report and move on.
+      if (reporter_ != NULL) {
+        SpecificField specific_field;
+        specific_field.field = field1;
+
+        parent_fields->push_back(specific_field);
+        reporter_->ReportIgnored(message1, message2, *parent_fields);
+        parent_fields->pop_back();
+      }
+
+      ++field_index1;
+      ++field_index2;
+      continue;
+    }
+
+    bool fieldDifferent = false;
+    if (field1->is_repeated()) {
+      fieldDifferent = !CompareRepeatedField(message1, message2, field1,
+                                             parent_fields);
+      if (fieldDifferent) {
+        if (reporter_ == NULL) return false;
+        isDifferent = true;
+      }
+    } else {
+      fieldDifferent = !CompareFieldValueUsingParentFields(
+          message1, message2, field1, -1, -1, parent_fields);
+
+      // If we have found differences, either report them or terminate if
+      // no reporter is present.
+      if (fieldDifferent && reporter_ == NULL) {
+        return false;
+      }
+
+      if (reporter_ != NULL) {
+        SpecificField specific_field;
+        specific_field.field = field1;
+        parent_fields->push_back(specific_field);
+        if (fieldDifferent) {
+          reporter_->ReportModified(message1, message2, *parent_fields);
+          isDifferent = true;
+        } else if (report_matches_) {
+          reporter_->ReportMatched(message1, message2, *parent_fields);
+        }
+        parent_fields->pop_back();
+      }
+    }
+    // Increment the field indicies.
+    ++field_index1;
+    ++field_index2;
+  }
+
+  return !isDifferent;
+}
+
+bool MessageDifferencer::IsMatch(const FieldDescriptor* repeated_field,
+                                 const MapKeyComparator* key_comparator,
+                                 const Message* message1,
+                                 const Message* message2,
+                                 const vector<SpecificField>& parent_fields,
+                                 int index1, int index2) {
+  vector<SpecificField> current_parent_fields(parent_fields);
+  if (repeated_field->cpp_type() != FieldDescriptor::CPPTYPE_MESSAGE) {
+    return CompareFieldValueUsingParentFields(
+        *message1, *message2, repeated_field, index1, index2,
+        &current_parent_fields);
+  }
+  // Back up the Reporter and output_string_.  They will be reset in the
+  // following code.
+  Reporter* backup_reporter = reporter_;
+  string* output_string = output_string_;
+  reporter_ = NULL;
+  output_string_ = NULL;
+  bool match;
+
+  if (key_comparator == NULL) {
+    match = CompareFieldValueUsingParentFields(
+        *message1, *message2, repeated_field, index1, index2,
+        &current_parent_fields);
+  } else {
+    const Reflection* reflection1 = message1->GetReflection();
+    const Reflection* reflection2 = message2->GetReflection();
+    const Message& m1 =
+        reflection1->GetRepeatedMessage(*message1, repeated_field, index1);
+    const Message& m2 =
+        reflection2->GetRepeatedMessage(*message2, repeated_field, index2);
+    SpecificField specific_field;
+    specific_field.field = repeated_field;
+    current_parent_fields.push_back(specific_field);
+    match = key_comparator->IsMatch(m1, m2, current_parent_fields);
+  }
+
+  reporter_ = backup_reporter;
+  output_string_ = output_string;
+  return match;
+}
+
+bool MessageDifferencer::CompareRepeatedField(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* repeated_field,
+    vector<SpecificField>* parent_fields) {
+  // the input FieldDescriptor is guaranteed to be repeated field.
+  const Reflection* reflection1 = message1.GetReflection();
+  const Reflection* reflection2 = message2.GetReflection();
+  const int count1 = reflection1->FieldSize(message1, repeated_field);
+  const int count2 = reflection2->FieldSize(message2, repeated_field);
+  const bool treated_as_subset = IsTreatedAsSubset(repeated_field);
+
+  // If the field is not treated as subset and no detailed reports is needed,
+  // we do a quick check on the number of the elements to avoid unnecessary
+  // comparison.
+  if (count1 != count2 && reporter_ == NULL && !treated_as_subset) {
+    return false;
+  }
+  // A match can never be found if message1 has more items than message2.
+  if (count1 > count2 && reporter_ == NULL) {
+    return false;
+  }
+
+  // These two list are used for store the index of the correspondent
+  // element in peer repeated field.
+  vector<int> match_list1;
+  vector<int> match_list2;
+
+  // Try to match indices of the repeated fields. Return false if match fails
+  // and there's no detailed report needed.
+  if (!MatchRepeatedFieldIndices(message1, message2, repeated_field,
+                                 *parent_fields, &match_list1, &match_list2) &&
+      reporter_ == NULL) {
+    return false;
+  }
+
+  bool fieldDifferent = false;
+  SpecificField specific_field;
+  specific_field.field = repeated_field;
+
+  // At this point, we have already matched pairs of fields (with the reporting
+  // to be done later). Now to check if the paired elements are different.
+  for (int i = 0; i < count1; i++) {
+    if (match_list1[i] == -1) continue;
+    specific_field.index = i;
+    specific_field.new_index = match_list1[i];
+
+    const bool result = CompareFieldValueUsingParentFields(
+        message1, message2, repeated_field, i, specific_field.new_index,
+        parent_fields);
+
+    // If we have found differences, either report them or terminate if
+    // no reporter is present. Note that ReportModified, ReportMoved, and
+    // ReportMatched are all mutually exclusive.
+    if (!result) {
+      if (reporter_ == NULL) return false;
+      parent_fields->push_back(specific_field);
+      reporter_->ReportModified(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+      fieldDifferent = true;
+    } else if (reporter_ != NULL &&
+               specific_field.index != specific_field.new_index) {
+      parent_fields->push_back(specific_field);
+      reporter_->ReportMoved(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+    } else if (report_matches_ && reporter_ != NULL) {
+      parent_fields->push_back(specific_field);
+      reporter_->ReportMatched(message1, message2, *parent_fields);
+      parent_fields->pop_back();
+    }
+  }
+
+  // Report any remaining additions or deletions.
+  for (int i = 0; i < count2; ++i) {
+    if (match_list2[i] != -1) continue;
+    if (!treated_as_subset) {
+      fieldDifferent = true;
+    }
+
+    if (reporter_ == NULL) continue;
+    specific_field.index = i;
+    specific_field.new_index = i;
+    parent_fields->push_back(specific_field);
+    reporter_->ReportAdded(message1, message2, *parent_fields);
+    parent_fields->pop_back();
+  }
+
+  for (int i = 0; i < count1; ++i) {
+    if (match_list1[i] != -1) continue;
+    specific_field.index = i;
+    parent_fields->push_back(specific_field);
+    reporter_->ReportDeleted(message1, message2, *parent_fields);
+    parent_fields->pop_back();
+    fieldDifferent = true;
+  }
+  return !fieldDifferent;
+}
+
+bool MessageDifferencer::CompareFieldValue(const Message& message1,
+                                           const Message& message2,
+                                           const FieldDescriptor* field,
+                                           int index1,
+                                           int index2) {
+  return CompareFieldValueUsingParentFields(message1, message2, field, index1,
+                                            index2, NULL);
+}
+
+bool MessageDifferencer::CompareFieldValueUsingParentFields(
+    const Message& message1, const Message& message2,
+    const FieldDescriptor* field, int index1, int index2,
+    vector<SpecificField>* parent_fields) {
+  FieldContext field_context(parent_fields);
+  FieldComparator::ComparisonResult result = GetFieldComparisonResult(
+      message1, message2, field, index1, index2, &field_context);
+
+  if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
+      result == FieldComparator::RECURSE) {
+    // Get the nested messages and compare them using one of the Compare
+    // methods.
+    const Reflection* reflection1 = message1.GetReflection();
+    const Reflection* reflection2 = message2.GetReflection();
+    const Message& m1 = field->is_repeated() ?
+        reflection1->GetRepeatedMessage(message1, field, index1) :
+        reflection1->GetMessage(message1, field);
+    const Message& m2 = field->is_repeated() ?
+        reflection2->GetRepeatedMessage(message2, field, index2) :
+        reflection2->GetMessage(message2, field);
+
+    // parent_fields is used in calls to Reporter methods.
+    if (parent_fields != NULL) {
+      // Append currently compared field to the end of parent_fields.
+      SpecificField specific_field;
+      specific_field.field = field;
+      specific_field.index = index1;
+      specific_field.new_index = index2;
+      parent_fields->push_back(specific_field);
+      const bool compare_result = Compare(m1, m2, parent_fields);
+      parent_fields->pop_back();
+      return compare_result;
+    } else {
+      // Recreates parent_fields as if m1 and m2 had no parents.
+      return Compare(m1, m2);
+    }
+  } else {
+    return (result == FieldComparator::SAME);
+  }
+}
+
+bool MessageDifferencer::CheckPathChanged(
+    const vector<SpecificField>& field_path) {
+  for (int i = 0; i < field_path.size(); ++i) {
+    if (field_path[i].index != field_path[i].new_index) return true;
+  }
+  return false;
+}
+
+bool MessageDifferencer::IsTreatedAsSet(const FieldDescriptor* field) {
+  if (!field->is_repeated()) return false;
+  if (field->is_map()) return true;
+  if (repeated_field_comparison_ == AS_SET)
+    return list_fields_.find(field) == list_fields_.end();
+  return (set_fields_.find(field) != set_fields_.end());
+}
+
+bool MessageDifferencer::IsTreatedAsSubset(const FieldDescriptor* field) {
+  return scope_ == PARTIAL &&
+      (IsTreatedAsSet(field) || GetMapKeyComparator(field) != NULL);
+}
+
+bool MessageDifferencer::IsIgnored(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* field,
+    const vector<SpecificField>& parent_fields) {
+  if (ignored_fields_.find(field) != ignored_fields_.end()) {
+    return true;
+  }
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    if (ignore_criteria_[i]->IsIgnored(message1, message2, field,
+                                       parent_fields)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+bool MessageDifferencer::IsUnknownFieldIgnored(
+    const Message& message1, const Message& message2,
+    const SpecificField& field, const vector<SpecificField>& parent_fields) {
+  for (int i = 0; i < ignore_criteria_.size(); ++i) {
+    if (ignore_criteria_[i]->IsUnknownFieldIgnored(message1, message2, field,
+                                                   parent_fields)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+const MessageDifferencer::MapKeyComparator* MessageDifferencer
+    ::GetMapKeyComparator(const FieldDescriptor* field) {
+  if (!field->is_repeated()) return NULL;
+  if (map_field_key_comparator_.find(field) !=
+      map_field_key_comparator_.end()) {
+    return map_field_key_comparator_[field];
+  }
+  return NULL;
+}
+
+namespace {
+
+typedef pair<int, const UnknownField*> IndexUnknownFieldPair;
+
+struct UnknownFieldOrdering {
+  inline bool operator()(const IndexUnknownFieldPair& a,
+                         const IndexUnknownFieldPair& b) const {
+    if (a.second->number() < b.second->number()) return true;
+    if (a.second->number() > b.second->number()) return false;
+    return a.second->type() < b.second->type();
+  }
+};
+
+}  // namespace
+
+bool MessageDifferencer::UnpackAny(const Message& any,
+                                   google::protobuf::scoped_ptr<Message>* data) {
+  const Reflection* reflection = any.GetReflection();
+  const FieldDescriptor* type_url_field;
+  const FieldDescriptor* value_field;
+  if (!internal::GetAnyFieldDescriptors(any, &type_url_field, &value_field)) {
+    return false;
+  }
+  const string& type_url = reflection->GetString(any, type_url_field);
+  string full_type_name;
+  if (!internal::ParseAnyTypeUrl(type_url, &full_type_name)) {
+    return false;
+  }
+
+  const google::protobuf::Descriptor* desc =
+      any.GetDescriptor()->file()->pool()->FindMessageTypeByName(
+          full_type_name);
+  if (desc == NULL) {
+    GOOGLE_LOG(ERROR) << "Proto type '" << full_type_name << "' not found";
+    return false;
+  }
+
+  if (dynamic_message_factory_ == NULL) {
+    dynamic_message_factory_.reset(new DynamicMessageFactory());
+  }
+  data->reset(dynamic_message_factory_->GetPrototype(desc)->New());
+  string serialized_value = reflection->GetString(any, value_field);
+  if (!(*data)->ParseFromString(serialized_value)) {
+    GOOGLE_LOG(ERROR) << "Failed to parse value for " << full_type_name;
+    return false;
+  }
+  return true;
+}
+
+bool MessageDifferencer::CompareUnknownFields(
+    const Message& message1, const Message& message2,
+    const google::protobuf::UnknownFieldSet& unknown_field_set1,
+    const google::protobuf::UnknownFieldSet& unknown_field_set2,
+    vector<SpecificField>* parent_field) {
+  // Ignore unknown fields in EQUIVALENT mode.
+  if (message_field_comparison_ == EQUIVALENT) return true;
+
+  if (unknown_field_set1.empty() && unknown_field_set2.empty()) {
+    return true;
+  }
+
+  bool is_different = false;
+
+  // We first sort the unknown fields by field number and type (in other words,
+  // in tag order), making sure to preserve ordering of values with the same
+  // tag.  This allows us to report only meaningful differences between the
+  // two sets -- that is, differing values for the same tag.  We use
+  // IndexUnknownFieldPairs to keep track of the field's original index for
+  // reporting purposes.
+  vector<IndexUnknownFieldPair> fields1;  // unknown_field_set1, sorted
+  vector<IndexUnknownFieldPair> fields2;  // unknown_field_set2, sorted
+  fields1.reserve(unknown_field_set1.field_count());
+  fields2.reserve(unknown_field_set2.field_count());
+
+  for (int i = 0; i < unknown_field_set1.field_count(); i++) {
+    fields1.push_back(std::make_pair(i, &unknown_field_set1.field(i)));
+  }
+  for (int i = 0; i < unknown_field_set2.field_count(); i++) {
+    fields2.push_back(std::make_pair(i, &unknown_field_set2.field(i)));
+  }
+
+  UnknownFieldOrdering is_before;
+  std::stable_sort(fields1.begin(), fields1.end(), is_before);
+  std::stable_sort(fields2.begin(), fields2.end(), is_before);
+
+  // In order to fill in SpecificField::index, we have to keep track of how
+  // many values we've seen with the same field number and type.
+  // current_repeated points at the first field in this range, and
+  // current_repeated_start{1,2} are the indexes of the first field in the
+  // range within fields1 and fields2.
+  const UnknownField* current_repeated = NULL;
+  int current_repeated_start1 = 0;
+  int current_repeated_start2 = 0;
+
+  // Now that we have two sorted lists, we can detect fields which appear only
+  // in one list or the other by traversing them simultaneously.
+  int index1 = 0;
+  int index2 = 0;
+  while (index1 < fields1.size() || index2 < fields2.size()) {
+    enum { ADDITION, DELETION, MODIFICATION, COMPARE_GROUPS,
+      NO_CHANGE } change_type;
+
+    // focus_field is the field we're currently reporting on.  (In the case
+    // of a modification, it's the field on the left side.)
+    const UnknownField* focus_field;
+    bool match = false;
+
+    if (index2 == fields2.size() ||
+        (index1 < fields1.size() &&
+          is_before(fields1[index1], fields2[index2]))) {
+      // fields1[index1] is not present in fields2.
+      change_type = DELETION;
+      focus_field = fields1[index1].second;
+    } else if (index1 == fields1.size() ||
+               is_before(fields2[index2], fields1[index1])) {
+      // fields2[index2] is not present in fields1.
+      if (scope_ == PARTIAL) {
+        // Ignore.
+        ++index2;
+        continue;
+      }
+      change_type = ADDITION;
+      focus_field = fields2[index2].second;
+    } else {
+      // Field type and number are the same.  See if the values differ.
+      change_type = MODIFICATION;
+      focus_field = fields1[index1].second;
+
+      switch (focus_field->type()) {
+        case UnknownField::TYPE_VARINT:
+          match = fields1[index1].second->varint() ==
+                  fields2[index2].second->varint();
+          break;
+        case UnknownField::TYPE_FIXED32:
+          match = fields1[index1].second->fixed32() ==
+                  fields2[index2].second->fixed32();
+          break;
+        case UnknownField::TYPE_FIXED64:
+          match = fields1[index1].second->fixed64() ==
+                  fields2[index2].second->fixed64();
+          break;
+        case UnknownField::TYPE_LENGTH_DELIMITED:
+          match = fields1[index1].second->length_delimited() ==
+                  fields2[index2].second->length_delimited();
+          break;
+        case UnknownField::TYPE_GROUP:
+          // We must deal with this later, after building the SpecificField.
+          change_type = COMPARE_GROUPS;
+          break;
+      }
+      if (match && change_type != COMPARE_GROUPS) {
+        change_type = NO_CHANGE;
+      }
+    }
+
+    if (current_repeated == NULL ||
+        focus_field->number() != current_repeated->number() ||
+        focus_field->type() != current_repeated->type()) {
+      // We've started a new repeated field.
+      current_repeated = focus_field;
+      current_repeated_start1 = index1;
+      current_repeated_start2 = index2;
+    }
+
+    if (change_type == NO_CHANGE && reporter_ == NULL) {
+      // Fields were already compared and matched and we have no reporter.
+      ++index1;
+      ++index2;
+      continue;
+    }
+
+    // Build the SpecificField.  This is slightly complicated.
+    SpecificField specific_field;
+    specific_field.unknown_field_number = focus_field->number();
+    specific_field.unknown_field_type = focus_field->type();
+
+    specific_field.unknown_field_set1 = &unknown_field_set1;
+    specific_field.unknown_field_set2 = &unknown_field_set2;
+
+    if (change_type != ADDITION) {
+      specific_field.unknown_field_index1 = fields1[index1].first;
+    }
+    if (change_type != DELETION) {
+      specific_field.unknown_field_index2 = fields2[index2].first;
+    }
+
+    // Calculate the field index.
+    if (change_type == ADDITION) {
+      specific_field.index = index2 - current_repeated_start2;
+      specific_field.new_index = index2 - current_repeated_start2;
+    } else {
+      specific_field.index = index1 - current_repeated_start1;
+      specific_field.new_index = index2 - current_repeated_start2;
+    }
+
+    if (IsUnknownFieldIgnored(message1, message2, specific_field,
+                              *parent_field)) {
+      if (reporter_ != NULL) {
+        parent_field->push_back(specific_field);
+        reporter_->ReportUnknownFieldIgnored(message1, message2, *parent_field);
+        parent_field->pop_back();
+      }
+      return true;
+    }
+
+    if (change_type == ADDITION || change_type == DELETION ||
+        change_type == MODIFICATION) {
+      if (reporter_ == NULL) {
+        // We found a difference and we have no reproter.
+        return false;
+      }
+      is_different = true;
+    }
+
+    parent_field->push_back(specific_field);
+
+    switch (change_type) {
+      case ADDITION:
+        reporter_->ReportAdded(message1, message2, *parent_field);
+        ++index2;
+        break;
+      case DELETION:
+        reporter_->ReportDeleted(message1, message2, *parent_field);
+        ++index1;
+        break;
+      case MODIFICATION:
+        reporter_->ReportModified(message1, message2, *parent_field);
+        ++index1;
+        ++index2;
+        break;
+      case COMPARE_GROUPS:
+        if (!CompareUnknownFields(message1, message2,
+                                  fields1[index1].second->group(),
+                                  fields2[index2].second->group(),
+                                  parent_field)) {
+          if (reporter_ == NULL) return false;
+          is_different = true;
+          reporter_->ReportModified(message1, message2, *parent_field);
+        }
+        ++index1;
+        ++index2;
+        break;
+      case NO_CHANGE:
+        ++index1;
+        ++index2;
+        if (report_matches_) {
+          reporter_->ReportMatched(message1, message2, *parent_field);
+        }
+    }
+
+    parent_field->pop_back();
+  }
+
+  return !is_different;
+}
+
+namespace {
+
+// Find maximum bipartite matching using the argumenting path algorithm.
+class MaximumMatcher {
+ public:
+  typedef ResultCallback2<bool, int, int> NodeMatchCallback;
+  // MaximumMatcher takes ownership of the passed in callback and uses it to
+  // determine whether a node on the left side of the bipartial graph matches
+  // a node on the right side. count1 is the number of nodes on the left side
+  // of the graph and count2 to is the number of nodes on the right side.
+  // Every node is referred to using 0-based indices.
+  // If a maximum match is found, the result will be stored in match_list1 and
+  // match_list2. match_list1[i] == j means the i-th node on the left side is
+  // matched to the j-th node on the right side and match_list2[x] == y means
+  // the x-th node on the right side is matched to y-th node on the left side.
+  // match_list1[i] == -1 means the node is not matched. Same with match_list2.
+  MaximumMatcher(int count1, int count2, NodeMatchCallback* callback,
+                 vector<int>* match_list1, vector<int>* match_list2);
+  // Find a maximum match and return the number of matched node pairs.
+  // If early_return is true, this method will return 0 immediately when it
+  // finds that not all nodes on the left side can be matched.
+  int FindMaximumMatch(bool early_return);
+ private:
+  // Determines whether the node on the left side of the bipartial graph
+  // matches the one on the right side.
+  bool Match(int left, int right);
+  // Find an argumenting path starting from the node v on the left side. If a
+  // path can be found, update match_list2_ to reflect the path and return
+  // true.
+  bool FindArgumentPathDFS(int v, vector<bool>* visited);
+
+  int count1_;
+  int count2_;
+  google::protobuf::scoped_ptr<NodeMatchCallback> match_callback_;
+  map<pair<int, int>, bool> cached_match_results_;
+  vector<int>* match_list1_;
+  vector<int>* match_list2_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MaximumMatcher);
+};
+
+MaximumMatcher::MaximumMatcher(int count1, int count2,
+                               NodeMatchCallback* callback,
+                               vector<int>* match_list1,
+                               vector<int>* match_list2)
+    : count1_(count1), count2_(count2), match_callback_(callback),
+      match_list1_(match_list1), match_list2_(match_list2) {
+  match_list1_->assign(count1, -1);
+  match_list2_->assign(count2, -1);
+}
+
+int MaximumMatcher::FindMaximumMatch(bool early_return) {
+  int result = 0;
+  for (int i = 0; i < count1_; ++i) {
+    vector<bool> visited(count1_);
+    if (FindArgumentPathDFS(i, &visited)) {
+      ++result;
+    } else if (early_return) {
+      return 0;
+    }
+  }
+  // Backfill match_list1_ as we only filled match_list2_ when finding
+  // argumenting pathes.
+  for (int i = 0; i < count2_; ++i) {
+    if ((*match_list2_)[i] != -1) {
+      (*match_list1_)[(*match_list2_)[i]] = i;
+    }
+  }
+  return result;
+}
+
+bool MaximumMatcher::Match(int left, int right) {
+  pair<int, int> p(left, right);
+  map<pair<int, int>, bool>::iterator it = cached_match_results_.find(p);
+  if (it != cached_match_results_.end()) {
+    return it->second;
+  }
+  cached_match_results_[p] = match_callback_->Run(left, right);
+  return cached_match_results_[p];
+}
+
+bool MaximumMatcher::FindArgumentPathDFS(int v, vector<bool>* visited) {
+  (*visited)[v] = true;
+  // We try to match those un-matched nodes on the right side first. This is
+  // the step that the navie greedy matching algorithm uses. In the best cases
+  // where the greedy algorithm can find a maximum matching, we will always
+  // find a match in this step and the performance will be identical to the
+  // greedy algorithm.
+  for (int i = 0; i < count2_; ++i) {
+    int matched = (*match_list2_)[i];
+    if (matched == -1 && Match(v, i)) {
+      (*match_list2_)[i] = v;
+      return true;
+    }
+  }
+  // Then we try those already matched nodes and see if we can find an
+  // alternaive match for the node matched to them.
+  // The greedy algorithm will stop before this and fail to produce the
+  // correct result.
+  for (int i = 0; i < count2_; ++i) {
+    int matched = (*match_list2_)[i];
+    if (matched != -1 && Match(v, i)) {
+      if (!(*visited)[matched] && FindArgumentPathDFS(matched, visited)) {
+        (*match_list2_)[i] = v;
+        return true;
+      }
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
+bool MessageDifferencer::MatchRepeatedFieldIndices(
+    const Message& message1,
+    const Message& message2,
+    const FieldDescriptor* repeated_field,
+    const vector<SpecificField>& parent_fields,
+    vector<int>* match_list1,
+    vector<int>* match_list2) {
+  const int count1 =
+      message1.GetReflection()->FieldSize(message1, repeated_field);
+  const int count2 =
+      message2.GetReflection()->FieldSize(message2, repeated_field);
+  const MapKeyComparator* key_comparator = GetMapKeyComparator(repeated_field);
+
+  match_list1->assign(count1, -1);
+  match_list2->assign(count2, -1);
+
+  SpecificField specific_field;
+  specific_field.field = repeated_field;
+
+  bool success = true;
+  // Find potential match if this is a special repeated field.
+  if (key_comparator != NULL || IsTreatedAsSet(repeated_field)) {
+    if (scope_ == PARTIAL) {
+      // When partial matching is enabled, Compare(a, b) && Compare(a, c)
+      // doesn't neccessarily imply Compare(b, c). Therefore a naive greedy
+      // algorithm will fail to find a maximum matching.
+      // Here we use the argumenting path algorithm.
+      MaximumMatcher::NodeMatchCallback* callback =
+          google::protobuf::internal::NewPermanentCallback(
+              this, &MessageDifferencer::IsMatch,
+              repeated_field, key_comparator,
+              &message1, &message2, parent_fields);
+      MaximumMatcher matcher(count1, count2, callback, match_list1,
+                             match_list2);
+      // If diff info is not needed, we should end the matching process as
+      // soon as possible if not all items can be matched.
+      bool early_return = (reporter_ == NULL);
+      int match_count = matcher.FindMaximumMatch(early_return);
+      if (match_count != count1 && reporter_ == NULL) return false;
+      success = success && (match_count == count1);
+    } else {
+      for (int i = 0; i < count1; ++i) {
+        // Indicates any matched elements for this repeated field.
+        bool match = false;
+
+        specific_field.index = i;
+        specific_field.new_index = i;
+
+        for (int j = 0; j < count2; j++) {
+          if (match_list2->at(j) != -1) continue;
+          specific_field.index = i;
+          specific_field.new_index = j;
+
+          match = IsMatch(repeated_field, key_comparator,
+                          &message1, &message2, parent_fields, i, j);
+
+          if (match) {
+            match_list1->at(specific_field.index) = specific_field.new_index;
+            match_list2->at(specific_field.new_index) = specific_field.index;
+            break;
+          }
+        }
+        if (!match && reporter_ == NULL) return false;
+        success = success && match;
+      }
+    }
+  } else {
+    // If this field should be treated as list, just label the match_list.
+    for (int i = 0; i < count1 && i < count2; i++) {
+      match_list1->at(i) = i;
+      match_list2->at(i) = i;
+    }
+  }
+
+  return success;
+}
+
+FieldComparator::ComparisonResult MessageDifferencer::GetFieldComparisonResult(
+    const Message& message1, const Message& message2,
+    const FieldDescriptor* field, int index1, int index2,
+    const FieldContext* field_context) {
+  FieldComparator* comparator = field_comparator_ != NULL ?
+      field_comparator_ : &default_field_comparator_;
+  return comparator->Compare(message1, message2, field,
+                             index1, index2, field_context);
+}
+
+// ===========================================================================
+
+MessageDifferencer::Reporter::Reporter() { }
+MessageDifferencer::Reporter::~Reporter() {}
+
+// ===========================================================================
+
+MessageDifferencer::MapKeyComparator::MapKeyComparator() {}
+MessageDifferencer::MapKeyComparator::~MapKeyComparator() {}
+
+// ===========================================================================
+
+MessageDifferencer::IgnoreCriteria::IgnoreCriteria() {}
+MessageDifferencer::IgnoreCriteria::~IgnoreCriteria() {}
+
+// ===========================================================================
+
+// Note that the printer's delimiter is not used, because if we are given a
+// printer, we don't know its delimiter.
+MessageDifferencer::StreamReporter::StreamReporter(
+    io::ZeroCopyOutputStream* output) : printer_(new io::Printer(output, '$')),
+                                        delete_printer_(true),
+                                        report_modified_aggregates_(false) { }
+
+MessageDifferencer::StreamReporter::StreamReporter(
+    io::Printer* printer) : printer_(printer),
+                            delete_printer_(false),
+                            report_modified_aggregates_(false) { }
+
+MessageDifferencer::StreamReporter::~StreamReporter() {
+  if (delete_printer_) delete printer_;
+}
+
+void MessageDifferencer::StreamReporter::PrintPath(
+    const vector<SpecificField>& field_path, bool left_side) {
+  for (int i = 0; i < field_path.size(); ++i) {
+    if (i > 0) {
+      printer_->Print(".");
+    }
+
+    SpecificField specific_field = field_path[i];
+
+    if (specific_field.field != NULL) {
+      if (specific_field.field->is_extension()) {
+        printer_->Print("($name$)", "name",
+                        specific_field.field->full_name());
+      } else {
+        printer_->PrintRaw(specific_field.field->name());
+      }
+    } else {
+      printer_->PrintRaw(SimpleItoa(specific_field.unknown_field_number));
+    }
+    if (left_side && specific_field.index >= 0) {
+      printer_->Print("[$name$]", "name", SimpleItoa(specific_field.index));
+    }
+    if (!left_side && specific_field.new_index >= 0) {
+      printer_->Print("[$name$]", "name", SimpleItoa(specific_field.new_index));
+    }
+  }
+}
+
+void MessageDifferencer::
+StreamReporter::PrintValue(const Message& message,
+                           const vector<SpecificField>& field_path,
+                           bool left_side) {
+  const SpecificField& specific_field = field_path.back();
+  const FieldDescriptor* field = specific_field.field;
+  if (field != NULL) {
+    string output;
+    int index = left_side ? specific_field.index : specific_field.new_index;
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      const Reflection* reflection = message.GetReflection();
+      const Message& field_message = field->is_repeated() ?
+          reflection->GetRepeatedMessage(message, field, index) :
+          reflection->GetMessage(message, field);
+      output = field_message.ShortDebugString();
+      if (output.empty()) {
+        printer_->Print("{ }");
+      } else {
+        printer_->Print("{ $name$ }", "name", output);
+      }
+    } else {
+      TextFormat::PrintFieldValueToString(message, field, index, &output);
+      printer_->PrintRaw(output);
+    }
+  } else {
+    const UnknownFieldSet* unknown_fields =
+        (left_side ?
+         specific_field.unknown_field_set1 :
+         specific_field.unknown_field_set2);
+    const UnknownField* unknown_field = &unknown_fields->field(
+        left_side ?
+        specific_field.unknown_field_index1 :
+        specific_field.unknown_field_index2);
+    PrintUnknownFieldValue(unknown_field);
+  }
+}
+
+void MessageDifferencer::
+StreamReporter::PrintUnknownFieldValue(const UnknownField* unknown_field) {
+  GOOGLE_CHECK(unknown_field != NULL) << " Cannot print NULL unknown_field.";
+
+  string output;
+  switch (unknown_field->type()) {
+    case UnknownField::TYPE_VARINT:
+      output = SimpleItoa(unknown_field->varint());
+      break;
+    case UnknownField::TYPE_FIXED32:
+      output = StrCat("0x", strings::Hex(unknown_field->fixed32(),
+                                         strings::ZERO_PAD_8));
+      break;
+    case UnknownField::TYPE_FIXED64:
+      output = StrCat("0x", strings::Hex(unknown_field->fixed64(),
+                                         strings::ZERO_PAD_16));
+      break;
+    case UnknownField::TYPE_LENGTH_DELIMITED:
+      output = StringPrintf("\"%s\"",
+          CEscape(unknown_field->length_delimited()).c_str());
+      break;
+    case UnknownField::TYPE_GROUP:
+      // TODO(kenton):  Print the contents of the group like we do for
+      //   messages.  Requires an equivalent of ShortDebugString() for
+      //   UnknownFieldSet.
+      output = "{ ... }";
+      break;
+  }
+  printer_->PrintRaw(output);
+}
+
+void MessageDifferencer::StreamReporter::Print(const string& str) {
+  printer_->Print(str.c_str());
+}
+
+void MessageDifferencer::StreamReporter::ReportAdded(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("added: ");
+  PrintPath(field_path, false);
+  printer_->Print(": ");
+  PrintValue(message2, field_path, false);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportDeleted(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("deleted: ");
+  PrintPath(field_path, true);
+  printer_->Print(": ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines
+}
+
+void MessageDifferencer::StreamReporter::ReportModified(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  if (!report_modified_aggregates_ && field_path.back().field == NULL) {
+    if (field_path.back().unknown_field_type == UnknownField::TYPE_GROUP) {
+      // Any changes to the subfields have already been printed.
+      return;
+    }
+  } else if (!report_modified_aggregates_) {
+    if (field_path.back().field->cpp_type() ==
+        FieldDescriptor::CPPTYPE_MESSAGE) {
+      // Any changes to the subfields have already been printed.
+      return;
+    }
+  }
+
+  printer_->Print("modified: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print(": ");
+  PrintValue(message1, field_path, true);
+  printer_->Print(" -> ");
+  PrintValue(message2, field_path, false);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportMoved(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("moved: ");
+  PrintPath(field_path, true);
+  printer_->Print(" -> ");
+  PrintPath(field_path, false);
+  printer_->Print(" : ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportMatched(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("matched: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print(" : ");
+  PrintValue(message1, field_path, true);
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportIgnored(
+    const Message& message1,
+    const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("ignored: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print("\n");  // Print for newlines.
+}
+
+void MessageDifferencer::StreamReporter::ReportUnknownFieldIgnored(
+    const Message& message1, const Message& message2,
+    const vector<SpecificField>& field_path) {
+  printer_->Print("ignored: ");
+  PrintPath(field_path, true);
+  if (CheckPathChanged(field_path)) {
+    printer_->Print(" -> ");
+    PrintPath(field_path, false);
+  }
+  printer_->Print("\n");  // Print for newlines.
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/message_differencer.h b/src/google/protobuf/util/message_differencer.h
new file mode 100644
index 0000000..3ea74e6
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer.h
@@ -0,0 +1,843 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file defines static methods and classes for comparing Protocol
+// Messages.
+//
+// Aug. 2008: Added Unknown Fields Comparison for messages.
+// Aug. 2009: Added different options to compare repeated fields.
+// Apr. 2010: Moved field comparison to FieldComparator.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
+#define GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
+
+#include <map>
+#include <set>
+#include <string>
+#include <vector>
+#include <google/protobuf/descriptor.h>  // FieldDescriptor
+#include <google/protobuf/message.h>  // Message
+#include <google/protobuf/unknown_field_set.h>
+#include <google/protobuf/util/field_comparator.h>
+
+namespace google {
+namespace protobuf {
+
+class DynamicMessageFactory;
+class FieldDescriptor;
+
+namespace io {
+class ZeroCopyOutputStream;
+class Printer;
+}
+
+namespace util {
+
+class FieldContext;  // declared below MessageDifferencer
+
+// A basic differencer that can be used to determine
+// the differences between two specified Protocol Messages. If any differences
+// are found, the Compare method will return false, and any differencer reporter
+// specified via ReportDifferencesTo will have its reporting methods called (see
+// below for implementation of the report). Based off of the original
+// ProtocolDifferencer implementation in //net/proto/protocol-differencer.h
+// (Thanks Todd!).
+//
+// MessageDifferencer REQUIRES that compared messages be the same type, defined
+// as messages that share the same descriptor.  If not, the behavior of this
+// class is undefined.
+//
+// People disagree on what MessageDifferencer should do when asked to compare
+// messages with different descriptors.  Some people think it should always
+// return false.  Others expect it to try to look for similar fields and
+// compare them anyway -- especially if the descriptors happen to be identical.
+// If we chose either of these behaviors, some set of people would find it
+// surprising, and could end up writing code expecting the other behavior
+// without realizing their error.  Therefore, we forbid that usage.
+//
+// This class is implemented based on the proto2 reflection. The performance
+// should be good enough for normal usages. However, for places where the
+// performance is extremely sensitive, there are several alternatives:
+// - Comparing serialized string
+// Downside: false negatives (there are messages that are the same but their
+// serialized strings are different).
+// - Equals code generator by compiler plugin (net/proto2/contrib/equals_plugin)
+// Downside: more generated code; maintenance overhead for the additional rule
+// (must be in sync with the original proto_library).
+//
+// Note on handling of google.protobuf.Any: MessageDifferencer automatically
+// unpacks Any::value into a Message and compares its individual fields.
+// Messages encoded in a repeated Any cannot be compared using TreatAsMap.
+//
+//
+// Note on thread-safety: MessageDifferencer is *not* thread-safe. You need to
+// guard it with a lock to use the same MessageDifferencer instance from
+// multiple threads. Note that it's fine to call static comparison methods
+// (like MessageDifferencer::Equals) concurrently.
+class LIBPROTOBUF_EXPORT MessageDifferencer {
+ public:
+  // Determines whether the supplied messages are equal. Equality is defined as
+  // all fields within the two messages being set to the same value. Primitive
+  // fields and strings are compared by value while embedded messages/groups
+  // are compared as if via a recursive call. Use IgnoreField() and Compare()
+  // if some fields should be ignored in the comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool Equals(const Message& message1, const Message& message2);
+
+  // Determines whether the supplied messages are equivalent. Equivalency is
+  // defined as all fields within the two messages having the same value. This
+  // differs from the Equals method above in that fields with default values
+  // are considered set to said value automatically. For details on how default
+  // values are defined for each field type, see http://shortn/_x2Gv6XFrWt.
+  // Also, Equivalent() ignores unknown fields. Use IgnoreField() and Compare()
+  // if some fields should be ignored in the comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool Equivalent(const Message& message1, const Message& message2);
+
+  // Determines whether the supplied messages are approximately equal.
+  // Approximate equality is defined as all fields within the two messages
+  // being approximately equal.  Primitive (non-float) fields and strings are
+  // compared by value, floats are compared using MathUtil::AlmostEquals() and
+  // embedded messages/groups are compared as if via a recursive call. Use
+  // IgnoreField() and Compare() if some fields should be ignored in the
+  // comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool ApproximatelyEquals(const Message& message1,
+                                  const Message& message2);
+
+  // Determines whether the supplied messages are approximately equivalent.
+  // Approximate equivalency is defined as all fields within the two messages
+  // being approximately equivalent. As in
+  // MessageDifferencer::ApproximatelyEquals, primitive (non-float) fields and
+  // strings are compared by value, floats are compared using
+  // MathUtil::AlmostEquals() and embedded messages/groups are compared as if
+  // via a recursive call. However, fields with default values are considered
+  // set to said value, as per MessageDiffencer::Equivalent. Use IgnoreField()
+  // and Compare() if some fields should be ignored in the comparison.
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  static bool ApproximatelyEquivalent(const Message& message1,
+                                      const Message& message2);
+
+  // Identifies an individual field in a message instance.  Used for field_path,
+  // below.
+  struct SpecificField {
+    // For known fields, "field" is filled in and "unknown_field_number" is -1.
+    // For unknown fields, "field" is NULL, "unknown_field_number" is the field
+    // number, and "unknown_field_type" is its type.
+    const FieldDescriptor* field;
+    int unknown_field_number;
+    UnknownField::Type unknown_field_type;
+
+    // If this a repeated field, "index" is the index within it.  For unknown
+    // fields, this is the index of the field among all unknown fields of the
+    // same field number and type.
+    int index;
+
+    // If "field" is a repeated field which is being treated as a map or
+    // a set (see TreatAsMap() and TreatAsSet(), below), new_index indicates
+    // the index the position to which the element has moved.  This only
+    // applies to ReportMoved() and (in the case of TreatAsMap())
+    // ReportModified().  In all other cases, "new_index" will have the same
+    // value as "index".
+    int new_index;
+
+    // For unknown fields, these are the pointers to the UnknownFieldSet
+    // containing the unknown fields. In certain cases (e.g. proto1's
+    // MessageSet, or nested groups of unknown fields), these may differ from
+    // the messages' internal UnknownFieldSets.
+    const UnknownFieldSet* unknown_field_set1;
+    const UnknownFieldSet* unknown_field_set2;
+
+    // For unknown fields, these are the index of the field within the
+    // UnknownFieldSets. One or the other will be -1 when
+    // reporting an addition or deletion.
+    int unknown_field_index1;
+    int unknown_field_index2;
+
+    SpecificField()
+        : field(NULL),
+          unknown_field_number(-1),
+          index(-1),
+          new_index(-1),
+          unknown_field_set1(NULL),
+          unknown_field_set2(NULL),
+          unknown_field_index1(-1),
+          unknown_field_index2(-1) {}
+  };
+
+  // Abstract base class from which all MessageDifferencer
+  // reporters derive. The five Report* methods below will be called when
+  // a field has been added, deleted, modified, moved, or matched. The third
+  // argument is a vector of FieldDescriptor pointers which describes the chain
+  // of fields that was taken to find the current field. For example, for a
+  // field found in an embedded message, the vector will contain two
+  // FieldDescriptors. The first will be the field of the embedded message
+  // itself and the second will be the actual field in the embedded message
+  // that was added/deleted/modified.
+  class LIBPROTOBUF_EXPORT Reporter {
+   public:
+    Reporter();
+    virtual ~Reporter();
+
+    // Reports that a field has been added into Message2.
+    virtual void ReportAdded(
+        const Message& message1, const Message& message2,
+        const vector<SpecificField>& field_path) = 0;
+
+    // Reports that a field has been deleted from Message1.
+    virtual void ReportDeleted(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) = 0;
+
+    // Reports that the value of a field has been modified.
+    virtual void ReportModified(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) = 0;
+
+    // Reports that a repeated field has been moved to another location.  This
+    // only applies when using TreatAsSet or TreatAsMap()  -- see below. Also
+    // note that for any given field, ReportModified and ReportMoved are
+    // mutually exclusive. If a field has been both moved and modified, then
+    // only ReportModified will be called.
+    virtual void ReportMoved(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) { }
+
+    // Reports that two fields match. Useful for doing side-by-side diffs.
+    // This function is mutually exclusive with ReportModified and ReportMoved.
+    // Note that you must call set_report_matches(true) before calling Compare
+    // to make use of this function.
+    virtual void ReportMatched(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) { }
+
+    // Reports that two fields would have been compared, but the
+    // comparison has been skipped because the field was marked as
+    // 'ignored' using IgnoreField().  This function is mutually
+    // exclusive with all the other Report() functions.
+    //
+    // The contract of ReportIgnored is slightly different than the
+    // other Report() functions, in that |field_path.back().index| is
+    // always equal to -1, even if the last field is repeated. This is
+    // because while the other Report() functions indicate where in a
+    // repeated field the action (Addition, Deletion, etc...)
+    // happened, when a repeated field is 'ignored', the differencer
+    // simply calls ReportIgnored on the repeated field as a whole and
+    // moves on without looking at its individual elements.
+    //
+    // Furthermore, ReportIgnored() does not indicate whether the
+    // fields were in fact equal or not, as Compare() does not inspect
+    // these fields at all. It is up to the Reporter to decide whether
+    // the fields are equal or not (perhaps with a second call to
+    // Compare()), if it cares.
+    virtual void ReportIgnored(
+        const Message& message1,
+        const Message& message2,
+        const vector<SpecificField>& field_path) { }
+
+    // Report that an unkown field is ignored. (see comment above).
+    // Note this is a different function since the last SpecificField in field
+    // path has a null field.  This could break existing Reporter.
+    virtual void ReportUnknownFieldIgnored(
+        const Message& message1, const Message& message2,
+        const vector<SpecificField>& field_path) {}
+
+   private:
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(Reporter);
+  };
+
+  // MapKeyComparator is used to determine if two elements have the same key
+  // when comparing elements of a repeated field as a map.
+  class LIBPROTOBUF_EXPORT MapKeyComparator {
+   public:
+    MapKeyComparator();
+    virtual ~MapKeyComparator();
+
+    virtual bool IsMatch(const Message& message1,
+                         const Message& message2,
+                         const vector<SpecificField>& parent_fields) const {
+      GOOGLE_CHECK(false) << "IsMatch() is not implemented.";
+      return false;
+    }
+
+   private:
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MapKeyComparator);
+  };
+
+  // Abstract base class from which all IgnoreCriteria derive.
+  // By adding IgnoreCriteria more complex ignore logic can be implemented.
+  // IgnoreCriteria are registed with AddIgnoreCriteria. For each compared
+  // field IsIgnored is called on each added IgnoreCriteria until one returns
+  // true or all return false.
+  // IsIgnored is called for fields where at least one side has a value.
+  class LIBPROTOBUF_EXPORT IgnoreCriteria {
+   public:
+    IgnoreCriteria();
+    virtual ~IgnoreCriteria();
+
+    // Returns true if the field should be ignored.
+    virtual bool IsIgnored(
+        const Message& message1,
+        const Message& message2,
+        const FieldDescriptor* field,
+        const vector<SpecificField>& parent_fields) = 0;
+
+    // Returns true if the unknown field should be ignored.
+    // Note: This will be called for unknown fields as well in which case
+    //       field.field will be null.
+    virtual bool IsUnknownFieldIgnored(
+        const Message& message1, const Message& message2,
+        const SpecificField& field,
+        const vector<SpecificField>& parent_fields) {
+      return false;
+    }
+  };
+
+  // To add a Reporter, construct default here, then use ReportDifferencesTo or
+  // ReportDifferencesToString.
+  explicit MessageDifferencer();
+
+  ~MessageDifferencer();
+
+  enum MessageFieldComparison {
+    EQUAL,       // Fields must be present in both messages
+                 // for the messages to be considered the same.
+    EQUIVALENT,  // Fields with default values are considered set
+                 // for comparison purposes even if not explicitly
+                 // set in the messages themselves.  Unknown fields
+                 // are ignored.
+  };
+
+  enum Scope {
+    FULL,    // All fields of both messages are considered in the comparison.
+    PARTIAL  // Only fields present in the first message are considered; fields
+             // set only in the second message will be skipped during
+             // comparison.
+  };
+
+  // DEPRECATED. Use FieldComparator::FloatComparison instead.
+  enum FloatComparison {
+    EXACT,       // Floats and doubles are compared exactly.
+    APPROXIMATE  // Floats and doubles are compared using the
+                 // MathUtil::AlmostEquals method.
+  };
+
+  enum RepeatedFieldComparison {
+    AS_LIST,     // Repeated fields are compared in order.  Differing values at
+                 // the same index are reported using ReportModified().  If the
+                 // repeated fields have different numbers of elements, the
+                 // unpaired elements are reported using ReportAdded() or
+                 // ReportDeleted().
+    AS_SET,      // Treat all the repeated fields as sets by default.
+                 // See TreatAsSet(), as below.
+  };
+
+  // The elements of the given repeated field will be treated as a set for
+  // diffing purposes, so different orderings of the same elements will be
+  // considered equal.  Elements which are present on both sides of the
+  // comparison but which have changed position will be reported with
+  // ReportMoved().  Elements which only exist on one side or the other are
+  // reported with ReportAdded() and ReportDeleted() regardless of their
+  // positions.  ReportModified() is never used for this repeated field.  If
+  // the only differences between the compared messages is that some fields
+  // have been moved, then the comparison returns true.
+  //
+  // If the scope of comparison is set to PARTIAL, then in addition to what's
+  // above, extra values added to repeated fields of the second message will
+  // not cause the comparison to fail.
+  //
+  // Note that set comparison is currently O(k * n^2) (where n is the total
+  // number of elements, and k is the average size of each element). In theory
+  // it could be made O(n * k) with a more complex hashing implementation. Feel
+  // free to contribute one if the current implementation is too slow for you.
+  // If partial matching is also enabled, the time complexity will be O(k * n^2
+  // + n^3) in which n^3 is the time complexity of the maximum matching
+  // algorithm.
+  //
+  // REQUIRES:  field->is_repeated() and field not registered with TreatAsList
+  void TreatAsSet(const FieldDescriptor* field);
+
+  // The elements of the given repeated field will be treated as a list for
+  // diffing purposes, so different orderings of the same elements will NOT be
+  // considered equal.
+  //
+  // REQUIRED: field->is_repeated() and field not registered with TreatAsSet
+  void TreatAsList(const FieldDescriptor* field);
+
+  // The elements of the given repeated field will be treated as a map for
+  // diffing purposes, with |key| being the map key.  Thus, elements with the
+  // same key will be compared even if they do not appear at the same index.
+  // Differences are reported similarly to TreatAsSet(), except that
+  // ReportModified() is used to report elements with the same key but
+  // different values.  Note that if an element is both moved and modified,
+  // only ReportModified() will be called.  As with TreatAsSet, if the only
+  // differences between the compared messages is that some fields have been
+  // moved, then the comparison returns true. See TreatAsSet for notes on
+  // performance.
+  //
+  // REQUIRES:  field->is_repeated()
+  // REQUIRES:  field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE
+  // REQUIRES:  key->containing_type() == field->message_type()
+  void TreatAsMap(const FieldDescriptor* field, const FieldDescriptor* key);
+  // Same as TreatAsMap except that this method will use multiple fields as
+  // the key in comparison. All specified fields in 'key_fields' should be
+  // present in the compared elements. Two elements will be treated as having
+  // the same key iff they have the same value for every specified field. There
+  // are two steps in the comparison process. The first one is key matching.
+  // Every element from one message will be compared to every element from
+  // the other message. Only fields in 'key_fields' are compared in this step
+  // to decide if two elements have the same key. The second step is value
+  // comparison. Those pairs of elements with the same key (with equal value
+  // for every field in 'key_fields') will be compared in this step.
+  // Time complexity of the first step is O(s * m * n ^ 2) where s is the
+  // average size of the fields specified in 'key_fields', m is the number of
+  // fields in 'key_fields' and n is the number of elements. If partial
+  // matching is enabled, an extra O(n^3) will be incured by the maximum
+  // matching algorithm. The second step is O(k * n) where k is the average
+  // size of each element.
+  void TreatAsMapWithMultipleFieldsAsKey(
+      const FieldDescriptor* field,
+      const vector<const FieldDescriptor*>& key_fields);
+  // Same as TreatAsMapWithMultipleFieldsAsKey, except that each of the field
+  // do not necessarily need to be a direct subfield. Each element in
+  // key_field_paths indicate a path from the message being compared, listing
+  // successive subfield to reach the key field.
+  //
+  // REQUIRES:
+  //   for key_field_path in key_field_paths:
+  //     key_field_path[0]->containing_type() == field->message_type()
+  //     for i in [0, key_field_path.size() - 1):
+  //       key_field_path[i+1]->containing_type() ==
+  //           key_field_path[i]->message_type()
+  //       key_field_path[i]->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE
+  //       !key_field_path[i]->is_repeated()
+  void TreatAsMapWithMultipleFieldPathsAsKey(
+      const FieldDescriptor* field,
+      const vector<vector<const FieldDescriptor*> >& key_field_paths);
+
+  // Uses a custom MapKeyComparator to determine if two elements have the same
+  // key when comparing a repeated field as a map.
+  // The caller is responsible to delete the key_comparator.
+  // This method varies from TreatAsMapWithMultipleFieldsAsKey only in the
+  // first key matching step. Rather than comparing some specified fields, it
+  // will invoke the IsMatch method of the given 'key_comparator' to decide if
+  // two elements have the same key.
+  void TreatAsMapUsingKeyComparator(
+      const FieldDescriptor* field,
+      const MapKeyComparator* key_comparator);
+
+  // Add a custom ignore criteria that is evaluated in addition to the
+  // ignored fields added with IgnoreField.
+  // Takes ownership of ignore_criteria.
+  void AddIgnoreCriteria(IgnoreCriteria* ignore_criteria);
+
+  // Indicates that any field with the given descriptor should be
+  // ignored for the purposes of comparing two messages. This applies
+  // to fields nested in the message structure as well as top level
+  // ones. When the MessageDifferencer encounters an ignored field,
+  // ReportIgnored is called on the reporter, if one is specified.
+  //
+  // The only place where the field's 'ignored' status is not applied is when
+  // it is being used as a key in a field passed to TreatAsMap or is one of
+  // the fields passed to TreatAsMapWithMultipleFieldsAsKey.
+  // In this case it is compared in key matching but after that it's ignored
+  // in value comparison.
+  void IgnoreField(const FieldDescriptor* field);
+
+  // Sets the field comparator used to determine differences between protocol
+  // buffer fields. By default it's set to a DefaultFieldComparator instance.
+  // MessageDifferencer doesn't take ownership over the passed object.
+  // Note that this method must be called before Compare for the comparator to
+  // be used.
+  void set_field_comparator(FieldComparator* comparator);
+
+  // DEPRECATED. Pass a DefaultFieldComparator instance instead.
+  // Sets the fraction and margin for the float comparison of a given field.
+  // Uses MathUtil::WithinFractionOrMargin to compare the values.
+  // NOTE: this method does nothing if differencer's field comparator has been
+  //       set to a custom object.
+  //
+  // REQUIRES: field->cpp_type == FieldDescriptor::CPPTYPE_DOUBLE or
+  //           field->cpp_type == FieldDescriptor::CPPTYPE_FLOAT
+  // REQUIRES: float_comparison_ == APPROXIMATE
+  void SetFractionAndMargin(const FieldDescriptor* field, double fraction,
+                            double margin);
+
+  // Sets the type of comparison (as defined in the MessageFieldComparison
+  // enumeration above) that is used by this differencer when determining how
+  // to compare fields in messages.
+  void set_message_field_comparison(MessageFieldComparison comparison);
+
+  // Tells the differencer whether or not to report matches. This method must
+  // be called before Compare. The default for a new differencer is false.
+  void set_report_matches(bool report_matches) {
+    report_matches_ = report_matches;
+  }
+
+  // Sets the scope of the comparison (as defined in the Scope enumeration
+  // above) that is used by this differencer when determining which fields to
+  // compare between the messages.
+  void set_scope(Scope scope);
+
+  // Returns the current scope used by this differencer.
+  Scope scope();
+
+  // DEPRECATED. Pass a DefaultFieldComparator instance instead.
+  // Sets the type of comparison (as defined in the FloatComparison enumeration
+  // above) that is used by this differencer when comparing float (and double)
+  // fields in messages.
+  // NOTE: this method does nothing if differencer's field comparator has been
+  //       set to a custom object.
+  void set_float_comparison(FloatComparison comparison);
+
+  // Sets the type of comparison for repeated field (as defined in the
+  // RepeatedFieldComparison enumeration above) that is used by this
+  // differencer when compare repeated fields in messages.
+  void set_repeated_field_comparison(RepeatedFieldComparison comparison);
+
+  // Compares the two specified messages, returning true if they are the same,
+  // false otherwise. If this method returns false, any changes between the
+  // two messages will be reported if a Reporter was specified via
+  // ReportDifferencesTo (see also ReportDifferencesToString).
+  //
+  // This method REQUIRES that the two messages have the same
+  // Descriptor (message1.GetDescriptor() == message2.GetDescriptor()).
+  bool Compare(const Message& message1, const Message& message2);
+
+  // Same as above, except comparing only the list of fields specified by the
+  // two vectors of FieldDescriptors.
+  bool CompareWithFields(const Message& message1, const Message& message2,
+                         const vector<const FieldDescriptor*>& message1_fields,
+                         const vector<const FieldDescriptor*>& message2_fields);
+
+  // Automatically creates a reporter that will output the differences
+  // found (if any) to the specified output string pointer. Note that this
+  // method must be called before Compare.
+  void ReportDifferencesToString(string* output);
+
+  // Tells the MessageDifferencer to report differences via the specified
+  // reporter. Note that this method must be called before Compare for
+  // the reporter to be used. It is the responsibility of the caller to delete
+  // this object.
+  // If the provided pointer equals NULL, the MessageDifferencer stops reporting
+  // differences to any previously set reporters or output strings.
+  void ReportDifferencesTo(Reporter* reporter);
+
+  // An implementation of the MessageDifferencer Reporter that outputs
+  // any differences found in human-readable form to the supplied
+  // ZeroCopyOutputStream or Printer. If a printer is used, the delimiter
+  // *must* be '$'.
+  class LIBPROTOBUF_EXPORT StreamReporter : public Reporter {
+   public:
+    explicit StreamReporter(io::ZeroCopyOutputStream* output);
+    explicit StreamReporter(io::Printer* printer);  // delimiter '$'
+    virtual ~StreamReporter();
+
+    // When set to true, the stream reporter will also output aggregates nodes
+    // (i.e. messages and groups) whose subfields have been modified. When
+    // false, will only report the individual subfields. Defaults to false.
+    void set_report_modified_aggregates(bool report) {
+      report_modified_aggregates_ = report;
+    }
+
+    // The following are implementations of the methods described above.
+    virtual void ReportAdded(const Message& message1, const Message& message2,
+                             const vector<SpecificField>& field_path);
+
+    virtual void ReportDeleted(const Message& message1,
+                               const Message& message2,
+                               const vector<SpecificField>& field_path);
+
+    virtual void ReportModified(const Message& message1,
+                                const Message& message2,
+                                const vector<SpecificField>& field_path);
+
+    virtual void ReportMoved(const Message& message1,
+                             const Message& message2,
+                             const vector<SpecificField>& field_path);
+
+    virtual void ReportMatched(const Message& message1,
+                               const Message& message2,
+                               const vector<SpecificField>& field_path);
+
+    virtual void ReportIgnored(const Message& message1,
+                               const Message& message2,
+                               const vector<SpecificField>& field_path);
+
+    virtual void ReportUnknownFieldIgnored(
+        const Message& message1, const Message& message2,
+        const vector<SpecificField>& field_path);
+
+   protected:
+    // Prints the specified path of fields to the buffer.
+    virtual void PrintPath(const vector<SpecificField>& field_path,
+                           bool left_side);
+
+    // Prints the value of fields to the buffer.  left_side is true if the
+    // given message is from the left side of the comparison, false if it
+    // was the right.  This is relevant only to decide whether to follow
+    // unknown_field_index1 or unknown_field_index2 when an unknown field
+    // is encountered in field_path.
+    virtual void PrintValue(const Message& message,
+                            const vector<SpecificField>& field_path,
+                            bool left_side);
+
+    // Prints the specified path of unknown fields to the buffer.
+    virtual void PrintUnknownFieldValue(const UnknownField* unknown_field);
+
+    // Just print a string
+    void Print(const string& str);
+
+   private:
+    io::Printer* printer_;
+    bool delete_printer_;
+    bool report_modified_aggregates_;
+
+    GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(StreamReporter);
+  };
+
+ private:
+  // A MapKeyComparator to be used in TreatAsMapUsingKeyComparator.
+  // Implementation of this class needs to do field value comparison which
+  // relies on some private methods of MessageDifferencer. That's why this
+  // class is declared as a nested class of MessageDifferencer.
+  class MultipleFieldsMapKeyComparator;
+  // Returns true if field1's number() is less than field2's.
+  static bool FieldBefore(const FieldDescriptor* field1,
+                          const FieldDescriptor* field2);
+
+  // Combine the two lists of fields into the combined_fields output vector.
+  // All fields present in both lists will always be included in the combined
+  // list.  Fields only present in one of the lists will only appear in the
+  // combined list if the corresponding fields_scope option is set to FULL.
+  void CombineFields(const vector<const FieldDescriptor*>& fields1,
+                     Scope fields1_scope,
+                     const vector<const FieldDescriptor*>& fields2,
+                     Scope fields2_scope,
+                     vector<const FieldDescriptor*>* combined_fields);
+
+  // Internal version of the Compare method which performs the actual
+  // comparison. The parent_fields vector is a vector containing field
+  // descriptors of all fields accessed to get to this comparison operation
+  // (i.e. if the current message is an embedded message, the parent_fields
+  // vector will contain the field that has this embedded message).
+  bool Compare(const Message& message1, const Message& message2,
+               vector<SpecificField>* parent_fields);
+
+  // Compares all the unknown fields in two messages.
+  bool CompareUnknownFields(const Message& message1, const Message& message2,
+                            const google::protobuf::UnknownFieldSet&,
+                            const google::protobuf::UnknownFieldSet&,
+                            vector<SpecificField>* parent_fields);
+
+  // Compares the specified messages for the requested field lists. The field
+  // lists are modified depending on comparison settings, and then passed to
+  // CompareWithFieldsInternal.
+  bool CompareRequestedFieldsUsingSettings(
+      const Message& message1, const Message& message2,
+      const vector<const FieldDescriptor*>& message1_fields,
+      const vector<const FieldDescriptor*>& message2_fields,
+      vector<SpecificField>* parent_fields);
+
+  // Compares the specified messages with the specified field lists.
+  bool CompareWithFieldsInternal(
+      const Message& message1, const Message& message2,
+      const vector<const FieldDescriptor*>& message1_fields,
+      const vector<const FieldDescriptor*>& message2_fields,
+      vector<SpecificField>* parent_fields);
+
+  // Compares the repeated fields, and report the error.
+  bool CompareRepeatedField(const Message& message1, const Message& message2,
+                            const FieldDescriptor* field,
+                            vector<SpecificField>* parent_fields);
+
+  // Shorthand for CompareFieldValueUsingParentFields with NULL parent_fields.
+  bool CompareFieldValue(const Message& message1,
+                         const Message& message2,
+                         const FieldDescriptor* field,
+                         int index1,
+                         int index2);
+
+  // Compares the specified field on the two messages, returning
+  // true if they are the same, false otherwise. For repeated fields,
+  // this method only compares the value in the specified index. This method
+  // uses Compare functions to recurse into submessages.
+  // The parent_fields vector is used in calls to a Reporter instance calls.
+  // It can be NULL, in which case the MessageDifferencer will create new
+  // list of parent messages if it needs to recursively compare the given field.
+  // To avoid confusing users you should not set it to NULL unless you modified
+  // Reporter to handle the change of parent_fields correctly.
+  bool CompareFieldValueUsingParentFields(const Message& message1,
+                                          const Message& message2,
+                                          const FieldDescriptor* field,
+                                          int index1,
+                                          int index2,
+                                          vector<SpecificField>* parent_fields);
+
+  // Compares the specified field on the two messages, returning comparison
+  // result, as returned by appropriate FieldComparator.
+  FieldComparator::ComparisonResult GetFieldComparisonResult(
+      const Message& message1, const Message& message2,
+      const FieldDescriptor* field, int index1, int index2,
+      const FieldContext* field_context);
+
+  // Check if the two elements in the repeated field are match to each other.
+  // if the key_comprator is NULL, this function returns true when the two
+  // elements are equal.
+  bool IsMatch(const FieldDescriptor* repeated_field,
+               const MapKeyComparator* key_comparator,
+               const Message* message1, const Message* message2,
+               const vector<SpecificField>& parent_fields,
+               int index1, int index2);
+
+  // Returns true when this repeated field has been configured to be treated
+  // as a set.
+  bool IsTreatedAsSet(const FieldDescriptor* field);
+
+  // Returns true when this repeated field is to be compared as a subset, ie.
+  // has been configured to be treated as a set or map and scope is set to
+  // PARTIAL.
+  bool IsTreatedAsSubset(const FieldDescriptor* field);
+
+  // Returns true if this field is to be ignored when this
+  // MessageDifferencer compares messages.
+  bool IsIgnored(
+      const Message& message1,
+      const Message& message2,
+      const FieldDescriptor* field,
+      const vector<SpecificField>& parent_fields);
+
+  // Returns true if this unknown field is to be ignored when this
+  // MessageDifferencer compares messages.
+  bool IsUnknownFieldIgnored(const Message& message1, const Message& message2,
+                             const SpecificField& field,
+                             const vector<SpecificField>& parent_fields);
+
+  // Returns MapKeyComparator* when this field has been configured to
+  // be treated as a map.  If not, returns NULL.
+  const MapKeyComparator* GetMapKeyComparator(const FieldDescriptor* field);
+
+  // Attempts to match indices of a repeated field, so that the contained values
+  // match. Clears output vectors and sets their values to indices of paired
+  // messages, ie. if message1[0] matches message2[1], then match_list1[0] == 1
+  // and match_list2[1] == 0. The unmatched indices are indicated by -1.
+  // This method returns false if the match failed. However, it doesn't mean
+  // that the comparison succeeds when this method returns true (you need to
+  // double-check in this case).
+  bool MatchRepeatedFieldIndices(const Message& message1,
+                                 const Message& message2,
+                                 const FieldDescriptor* repeated_field,
+                                 const vector<SpecificField>& parent_fields,
+                                 vector<int>* match_list1,
+                                 vector<int>* match_list2);
+
+  // If "any" is of type google.protobuf.Any, extract its payload using
+  // DynamicMessageFactory and store in "data".
+  bool UnpackAny(const Message& any, google::protobuf::scoped_ptr<Message>* data);
+
+  // Checks if index is equal to new_index in all the specific fields.
+  static bool CheckPathChanged(const vector<SpecificField>& parent_fields);
+
+  // Defines a map between field descriptors and their MapKeyComparators.
+  // Used for repeated fields when they are configured as TreatAsMap.
+  typedef map<const FieldDescriptor*,
+              const MapKeyComparator*> FieldKeyComparatorMap;
+
+  // Defines a set to store field descriptors.  Used for repeated fields when
+  // they are configured as TreatAsSet.
+  typedef set<const FieldDescriptor*> FieldSet;
+
+  Reporter* reporter_;
+  DefaultFieldComparator default_field_comparator_;
+  FieldComparator* field_comparator_;
+  MessageFieldComparison message_field_comparison_;
+  Scope scope_;
+  RepeatedFieldComparison repeated_field_comparison_;
+
+  FieldSet set_fields_;
+  FieldSet list_fields_;
+  // Keeps track of MapKeyComparators that are created within
+  // MessageDifferencer. These MapKeyComparators should be deleted
+  // before MessageDifferencer is destroyed.
+  // When TreatAsMap or TreatAsMapWithMultipleFieldsAsKey is called, we don't
+  // store the supplied FieldDescriptors directly. Instead, a new
+  // MapKeyComparator is created for comparison purpose.
+  vector<MapKeyComparator*> owned_key_comparators_;
+  FieldKeyComparatorMap map_field_key_comparator_;
+  vector<IgnoreCriteria*> ignore_criteria_;
+
+  FieldSet ignored_fields_;
+
+  bool compare_unknown_fields_;
+  bool report_matches_;
+
+  string* output_string_;
+
+  google::protobuf::scoped_ptr<DynamicMessageFactory> dynamic_message_factory_;
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageDifferencer);
+};
+
+// This class provides extra information to the FieldComparator::Compare
+// function.
+class LIBPROTOBUF_EXPORT FieldContext {
+ public:
+  explicit FieldContext(
+      vector<MessageDifferencer::SpecificField>* parent_fields)
+      : parent_fields_(parent_fields) {}
+
+  vector<MessageDifferencer::SpecificField>* parent_fields() const {
+    return parent_fields_;
+  }
+
+ private:
+  vector<MessageDifferencer::SpecificField>* parent_fields_;
+};
+
+}
+}
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_MESSAGE_DIFFERENCER_H__
diff --git a/src/google/protobuf/util/message_differencer_unittest.cc b/src/google/protobuf/util/message_differencer_unittest.cc
new file mode 100755
index 0000000..a867c88
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer_unittest.cc
@@ -0,0 +1,3151 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: jschorr@google.com (Joseph Schorr)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// TODO(ksroka): Move some of these tests to field_comparator_test.cc.
+
+#include <algorithm>
+#include <string>
+#include <vector>
+
+
+#include <google/protobuf/util/field_comparator.h>
+#include <google/protobuf/util/message_differencer.h>
+#include <google/protobuf/util/message_differencer_unittest.pb.h>
+#include <google/protobuf/text_format.h>
+#include <google/protobuf/wire_format.h>
+#include <google/protobuf/io/zero_copy_stream_impl.h>
+#include <google/protobuf/io/coded_stream.h>
+#include <google/protobuf/any_test.pb.h>
+#include <google/protobuf/map_unittest.pb.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/map_test_util.h>
+#include <google/protobuf/test_util.h>
+
+#include <google/protobuf/stubs/logging.h>
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+
+namespace {
+
+
+const FieldDescriptor* GetFieldDescriptor(
+    const Message& message, const string& field_name) {
+  vector<string> field_path =
+      Split(field_name, ".", true);
+  const Descriptor* descriptor = message.GetDescriptor();
+  const FieldDescriptor* field = NULL;
+  for (int i = 0; i < field_path.size(); i++) {
+    field = descriptor->FindFieldByName(field_path[i]);
+    descriptor = field->message_type();
+  }
+  return field;
+}
+
+void ExpectEqualsWithDifferencer(util::MessageDifferencer* differencer,
+                                 const Message& msg1,
+                                 const Message& msg2) {
+  differencer->set_scope(util::MessageDifferencer::FULL);
+  EXPECT_TRUE(differencer->Compare(msg1, msg2));
+
+  differencer->set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer->Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.add_repeated_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, MapFieldEqualityTest) {
+  // Create the testing protos
+  unittest::TestMap msg1;
+  unittest::TestMap msg2;
+
+  MapReflectionTester tester(unittest::TestMap::descriptor());
+  tester.SetMapFieldsViaReflection(&msg1);
+  tester.SetMapFieldsViaReflection(&msg2);
+  tester.SwapMapsViaReflection(&msg1);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEqualityTestExtraField) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.clear_optional_int32();
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEqualityTestSkipRequiredField) {
+  // Create the testing protos
+  unittest::TestRequired msg1;
+  unittest::TestRequired msg2;
+
+  msg1.set_a(401);
+  msg2.set_a(401);
+  msg2.set_b(402);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialInequalityMissingFieldTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg2.clear_optional_int32();
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldPartialInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.add_repeated_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, EquivalencyNotEqualTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.clear_optional_int32();
+  msg2.set_optional_int32(0);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicInequivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicEquivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicInequivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equivalent(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicPartialEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEquivalencyNotEqualTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(0);
+  msg2.clear_optional_int32();
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEquivalencyTestExtraField) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.clear_optional_int32();
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, PartialEquivalencyTestSkipRequiredField) {
+  // Create the testing protos
+  unittest::TestRequired msg1;
+  unittest::TestRequired msg2;
+
+  msg1.set_a(401);
+  msg2.set_a(401);
+  msg2.set_b(402);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialInequivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialEquivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicPartialInequivalencyNonSetTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  msg1.set_optional_int32(-1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateModifiedEqualityTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  const float v1 = 2.300005f;
+  const float v2 = 2.300006f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+
+  // Compare
+  ASSERT_NE(v1, v2) << "Should not be the same: " << v1 << ", " << v2;
+  ASSERT_FLOAT_EQ(v1, v2) << "Should be approx. equal: " << v1 << ", " << v2;
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateModifiedEquivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Modify the approximateness requirement
+  const float v1 = 2.300005f;
+  const float v2 = 2.300006f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+
+  // Compare
+  ASSERT_NE(v1, v2) << "Should not be the same: " << v1 << ", " << v2;
+  ASSERT_FLOAT_EQ(v1, v2) << "Should be approx. equal: " << v1 << ", " << v2;
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+
+  // Modify the equivalency requirement too
+  msg1.clear_optional_int32();
+  msg2.set_optional_int32(0);
+
+  // Compare. Now should only pass on ApproximatelyEquivalent
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+  EXPECT_FALSE(util::MessageDifferencer::Equivalent(msg1, msg2));
+  EXPECT_FALSE(util::MessageDifferencer::ApproximatelyEquals(msg1, msg2));
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+}
+
+TEST(MessageDifferencerTest, ApproximateInequivalencyTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on equivalency
+  msg1.set_optional_int32(-1);
+  EXPECT_FALSE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                 msg2));
+
+  // Make these fields the same again.
+  msg1.set_optional_int32(0);
+  msg2.set_optional_int32(0);
+  EXPECT_TRUE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                msg2));
+
+  // Should fail on approximate equality check
+  const float v1 = 2.3f;
+  const float v2 = 9.3f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+  EXPECT_FALSE(util::MessageDifferencer::ApproximatelyEquivalent(msg1,
+                                                                 msg2));
+}
+
+TEST(MessageDifferencerTest, WithinFractionOrMarginFloatTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on approximate equality check
+  const float v1 = 100.0f;
+  const float v2 = 109.9f;
+  msg1.set_optional_float(v1);
+  msg2.set_optional_float(v2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  const FieldDescriptor* fd =
+      msg1.GetDescriptor()->FindFieldByName("optional_float");
+
+  // Set float comparison to exact, margin and fraction value should not matter.
+  differencer.set_float_comparison(util::MessageDifferencer::EXACT);
+  // Set margin for float comparison.
+  differencer.SetFractionAndMargin(fd, 0.0, 10.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Margin and fraction float comparison is activated when float comparison is
+  // set to approximate.
+  differencer.set_float_comparison(util::MessageDifferencer::APPROXIMATE);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Test out float comparison with fraction.
+  differencer.SetFractionAndMargin(fd, 0.2, 0.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Should fail since the fraction is smaller than error.
+  differencer.SetFractionAndMargin(fd, 0.01, 0.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Should pass if either fraction or margin are satisfied.
+  differencer.SetFractionAndMargin(fd, 0.01, 10.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Make sure that the margin and fraction only affects the field that it was
+  // set for.
+  msg1.set_default_float(v1);
+  msg2.set_default_float(v2);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  msg1.set_default_float(v1);
+  msg2.set_default_float(v1);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, WithinFractionOrMarginDoubleTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on approximate equality check
+  const double v1 = 100.0;
+  const double v2 = 109.9;
+  msg1.set_optional_double(v1);
+  msg2.set_optional_double(v2);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Set comparison to exact, margin and fraction value should not matter.
+  differencer.set_float_comparison(util::MessageDifferencer::EXACT);
+  // Set margin for float comparison.
+  const FieldDescriptor* fd =
+      msg1.GetDescriptor()->FindFieldByName("optional_double");
+  differencer.SetFractionAndMargin(fd, 0.0, 10.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Margin and fraction comparison is activated when float comparison is
+  // set to approximate.
+  differencer.set_float_comparison(util::MessageDifferencer::APPROXIMATE);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Test out comparison with fraction.
+  differencer.SetFractionAndMargin(fd, 0.2, 0.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Should fail since the fraction is smaller than error.
+  differencer.SetFractionAndMargin(fd, 0.01, 0.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Should pass if either fraction or margin are satisfied.
+  differencer.SetFractionAndMargin(fd, 0.01, 10.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Make sure that the margin and fraction only affects the field that it was
+  // set for.
+  msg1.set_default_double(v1);
+  msg2.set_default_double(v2);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  msg1.set_default_double(v1);
+  msg2.set_default_double(v1);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, WithinDefaultFractionOrMarginDoubleTest) {
+  // Create the testing protos
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  // Should fail on approximate equality check
+  const double v1 = 100.0;
+  const double v2 = 109.9;
+  msg1.set_optional_double(v1);
+  msg2.set_optional_double(v2);
+
+  util::MessageDifferencer differencer;
+
+  // Compare
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Set up a custom field comparitor, with a default fraction and margin for
+  // float and double comparison.
+  util::DefaultFieldComparator field_comparitor;
+  field_comparitor.SetDefaultFractionAndMargin(0.0, 10.0);
+  differencer.set_field_comparator(&field_comparitor);
+
+  // Set comparison to exact, margin and fraction value should not matter.
+  field_comparitor.set_float_comparison(util::DefaultFieldComparator::EXACT);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Margin and fraction comparison is activated when float comparison is
+  // set to approximate.
+  field_comparitor.set_float_comparison(
+      util::DefaultFieldComparator::APPROXIMATE);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Test out comparison with fraction.
+  field_comparitor.SetDefaultFractionAndMargin(0.2, 0.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Should fail since the fraction is smaller than error.
+  field_comparitor.SetDefaultFractionAndMargin(0.01, 0.0);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Should pass if either fraction or margin are satisfied.
+  field_comparitor.SetDefaultFractionAndMargin(0.01, 10.0);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Make sure that the default margin and fraction affects all fields
+  msg1.set_default_double(v1);
+  msg2.set_default_double(v2);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicFieldOrderingsTest) {
+  // Create the testing protos
+  unittest::TestFieldOrderings msg1;
+  unittest::TestFieldOrderings msg2;
+
+  TestUtil::SetAllFieldsAndExtensions(&msg1);
+  TestUtil::SetAllFieldsAndExtensions(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicFieldOrderingInequalityTest) {
+  // Create the testing protos
+  unittest::TestFieldOrderings msg1;
+  unittest::TestFieldOrderings msg2;
+
+  TestUtil::SetAllFieldsAndExtensions(&msg1);
+  TestUtil::SetAllFieldsAndExtensions(&msg2);
+
+  msg1.set_my_float(15.00);
+  msg2.set_my_float(16.00);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, BasicExtensionTest) {
+  // Create the testing protos
+  unittest::TestAllExtensions msg1;
+  unittest::TestAllExtensions msg2;
+
+  TestUtil::SetAllExtensions(&msg1);
+  TestUtil::SetAllExtensions(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+
+TEST(MessageDifferencerTest, BasicExtensionInequalityTest) {
+  // Create the testing protos
+  unittest::TestAllExtensions msg1;
+  unittest::TestAllExtensions msg2;
+
+  TestUtil::SetAllExtensions(&msg1);
+  TestUtil::SetAllExtensions(&msg2);
+
+  msg1.SetExtension(unittest::optional_int32_extension, 101);
+  msg2.SetExtension(unittest::optional_int32_extension, 102);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, OneofTest) {
+  // Create the testing protos
+  unittest::TestOneof2 msg1;
+  unittest::TestOneof2 msg2;
+
+  TestUtil::SetOneof1(&msg1);
+  TestUtil::SetOneof1(&msg2);
+
+  // Compare
+  EXPECT_TRUE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, OneofInequalityTest) {
+  // Create the testing protos
+  unittest::TestOneof2 msg1;
+  unittest::TestOneof2 msg2;
+
+  TestUtil::SetOneof1(&msg1);
+  TestUtil::SetOneof2(&msg2);
+
+  // Compare
+  EXPECT_FALSE(util::MessageDifferencer::Equals(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, UnknownFieldPartialEqualTest) {
+  unittest::TestEmptyMessage empty1;
+  unittest::TestEmptyMessage empty2;
+
+  UnknownFieldSet* unknown1 = empty1.mutable_unknown_fields();
+  UnknownFieldSet* unknown2 = empty2.mutable_unknown_fields();
+
+  unknown1->AddVarint(243, 122);
+  unknown1->AddLengthDelimited(245, "abc");
+  unknown1->AddGroup(246)->AddFixed32(248, 1);
+  unknown1->mutable_field(2)->mutable_group()->AddFixed32(248, 2);
+
+  unknown2->AddVarint(243, 122);
+  unknown2->AddLengthDelimited(245, "abc");
+  unknown2->AddGroup(246)->AddFixed32(248, 1);
+  unknown2->mutable_field(2)->mutable_group()->AddFixed32(248, 2);
+
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(empty1, empty2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEqualityAllTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsInequalityAllTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEmptyListAlwaysSucceeds) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+
+  vector<const FieldDescriptor*> empty_fields;
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            empty_fields, empty_fields));
+
+  TestUtil::SetAllFields(&msg2);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            empty_fields, empty_fields));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsCompareWithSelf) {
+  unittest::TestAllTypes msg1;
+  TestUtil::SetAllFields(&msg1);
+
+  vector<const FieldDescriptor*> fields;
+  msg1.GetReflection()->ListFields(msg1, &fields);
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg1, fields, fields));
+
+  {
+    // Compare with a subset of fields.
+    vector<const FieldDescriptor*> compare_fields;
+    for (int i = 0; i < fields.size(); ++i) {
+      if (i % 2 == 0) {
+        compare_fields.push_back(fields[i]);
+      }
+    }
+    EXPECT_TRUE(differencer.CompareWithFields(msg1, msg1,
+                                              compare_fields, compare_fields));
+  }
+  {
+    // Specify a different set of fields to compare, even though we're using the
+    // same message. This should fail, since we are explicitly saying that the
+    // set of fields are different.
+    vector<const FieldDescriptor*> compare_fields1;
+    vector<const FieldDescriptor*> compare_fields2;
+    for (int i = 0; i < fields.size(); ++i) {
+      if (i % 2 == 0) {
+        compare_fields1.push_back(fields[i]);
+      } else {
+        compare_fields2.push_back(fields[i]);
+      }
+    }
+    EXPECT_FALSE(differencer.CompareWithFields(
+        msg1, msg1, compare_fields1, compare_fields2));
+  }
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEqualityAllShuffledTest) {
+  // This is a public function, so make sure there are no assumptions about the
+  // list of fields. Randomly shuffle them to make sure that they are properly
+  // ordered for comparison.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  std::random_shuffle(fields1.begin(), fields1.end());
+  std::random_shuffle(fields2.begin(), fields2.end());
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsSubsetEqualityTest) {
+  // Specify a set of fields to compare. All the fields are equal.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+
+  vector<const FieldDescriptor*> compare_fields;
+  // Only compare the field descriptors with even indices.
+  for (int i = 0; i < fields1.size(); ++i) {
+    if (i % 2 == 0) {
+      compare_fields.push_back(fields1[i]);
+    }
+  }
+
+  util::MessageDifferencer differencer;
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            compare_fields, compare_fields));
+}
+
+TEST(MessageDifferencerTest,
+     SpecifiedFieldsSubsetIgnoresOtherFieldDifferencesTest) {
+  // Specify a set of fields to compare, but clear all the other fields in one
+  // of the messages. This should fail a regular compare, but CompareWithFields
+  // should succeed.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  const Reflection* reflection = msg1.GetReflection();
+  reflection->ListFields(msg1, &fields1);
+
+  vector<const FieldDescriptor*> compare_fields;
+  // Only compare the field descriptors with even indices.
+  for (int i = 0; i < fields1.size(); ++i) {
+    if (i % 2 == 0) {
+      compare_fields.push_back(fields1[i]);
+    } else {
+      reflection->ClearField(&msg2, fields1[i]);
+    }
+  }
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2,
+                                            compare_fields, compare_fields));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsDetectsDifferencesTest) {
+  // Change all of the repeated fields in one of the messages, and use only
+  // those fields for comparison.
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+  TestUtil::ModifyRepeatedFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+
+  vector<const FieldDescriptor*> compare_fields;
+  // Only compare the repeated field descriptors.
+  for (int i = 0; i < fields1.size(); ++i) {
+    if (fields1[i]->is_repeated()) {
+      compare_fields.push_back(fields1[i]);
+    }
+  }
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.CompareWithFields(msg1, msg2,
+                                             compare_fields, compare_fields));
+}
+
+TEST(MessageDifferencerTest, SpecifiedFieldsEquivalenceAllTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+
+  TestUtil::SetAllFields(&msg1);
+  TestUtil::SetAllFields(&msg2);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  msg1.GetReflection()->ListFields(msg1, &fields1);
+  msg2.GetReflection()->ListFields(msg2, &fields2);
+
+  util::MessageDifferencer differencer;
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest,
+     SpecifiedFieldsEquivalenceIgnoresOtherFieldDifferencesTest) {
+  unittest::TestAllTypes msg1;
+  unittest::TestAllTypes msg2;
+  const Descriptor* desc = msg1.GetDescriptor();
+
+  const FieldDescriptor* optional_int32_desc =
+      desc->FindFieldByName("optional_int32");
+  const FieldDescriptor* optional_int64_desc =
+      desc->FindFieldByName("optional_int64");
+  const FieldDescriptor* default_int64_desc =
+      desc->FindFieldByName("default_int64");
+  ASSERT_TRUE(optional_int32_desc != NULL);
+  ASSERT_TRUE(optional_int64_desc != NULL);
+  ASSERT_TRUE(default_int64_desc != NULL);
+  msg1.set_optional_int32(0);
+  msg2.set_optional_int64(0);
+  msg1.set_default_int64(default_int64_desc->default_value_int64());
+
+  // Set a field to a non-default value so we know that field selection is
+  // actually doing something.
+  msg2.set_optional_uint64(23);
+
+  vector<const FieldDescriptor*> fields1;
+  vector<const FieldDescriptor*> fields2;
+  fields1.push_back(optional_int32_desc);
+  fields1.push_back(default_int64_desc);
+
+  fields2.push_back(optional_int64_desc);
+
+  util::MessageDifferencer differencer;
+  EXPECT_FALSE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+  differencer.set_message_field_comparison(
+      util::MessageDifferencer::EQUIVALENT);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields1, fields2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_SetOfSet) {
+  // Create the testing protos
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_ra(1); item->add_ra(2); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(5); item->add_ra(6);
+  item = msg1.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(6); item->add_ra(7); item->add_ra(8);
+
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(5);
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(8); item->add_ra(7);
+  item = msg2.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg2.add_item();
+  item->add_ra(3); item->add_ra(2); item->add_ra(1);
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Combination) {
+  // Create the testing protos
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = "a"
+  // Treat "item.ra" also as Set
+  // Treat "rv" as Set
+  // Treat "rw" as List
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(3);
+  item->add_ra(1); item->add_ra(2); item->add_ra(3);
+  item = msg1.add_item();
+  item->set_a(4);
+  item->add_ra(5); item->add_ra(6);
+  item = msg1.add_item();
+  item->set_a(1);
+  item->add_ra(1); item->add_ra(3);
+  item = msg1.add_item();
+  item->set_a(2);
+  item->add_ra(6); item->add_ra(7); item->add_ra(8);
+
+  item = msg2.add_item();
+  item->set_a(4);
+  item->add_ra(6); item->add_ra(5);
+  item = msg2.add_item();
+  item->set_a(2);
+  item->add_ra(6); item->add_ra(8); item->add_ra(7);
+  item = msg2.add_item();
+  item->set_a(1);
+  item->add_ra(1); item->add_ra(3);
+  item = msg2.add_item();
+  item->set_a(3);
+  item->add_ra(3); item->add_ra(2); item->add_ra(1);
+
+  msg1.add_rv(3);
+  msg1.add_rv(4);
+  msg1.add_rv(7);
+  msg1.add_rv(0);
+  msg2.add_rv(4);
+  msg2.add_rv(3);
+  msg2.add_rv(0);
+  msg2.add_rv(7);
+
+  msg1.add_rw("nothing"); msg2.add_rw("nothing");
+  msg1.add_rw("should"); msg2.add_rw("should");
+  msg1.add_rw("change"); msg2.add_rw("change");
+
+  // Compare
+  util::MessageDifferencer differencer1;
+  differencer1.TreatAsMap(msg1.GetDescriptor()->FindFieldByName("item"),
+                          item->GetDescriptor()->FindFieldByName("a"));
+  differencer1.TreatAsSet(msg1.GetDescriptor()->FindFieldByName("rv"));
+  differencer1.TreatAsSet(item->GetDescriptor()->FindFieldByName("ra"));
+  EXPECT_TRUE(differencer1.Compare(msg1, msg2));
+
+  util::MessageDifferencer differencer2;
+  differencer2.TreatAsMap(msg1.GetDescriptor()->FindFieldByName("item"),
+                          item->GetDescriptor()->FindFieldByName("a"));
+  differencer2.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  differencer2.TreatAsList(msg1.GetDescriptor()->FindFieldByName("rw"));
+  EXPECT_TRUE(differencer2.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_Partial) {
+  protobuf_unittest::TestDiffMessage msg1;
+  // message msg1 {
+  //   item { a: 1; b: "11" }
+  // }
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("11");
+
+  protobuf_unittest::TestDiffMessage msg2;
+  // message msg2 {
+  //   item { a: 2; b: "22" }
+  //   item { a: 1; b: "11" }
+  // }
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("22");
+  item = msg2.add_item();
+  item->set_a(1);
+  item->set_b("11");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsMap(GetFieldDescriptor(msg1, "item"),
+                         GetFieldDescriptor(msg1, "item.a"));
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Duplicates) {
+  protobuf_unittest::TestDiffMessage a, b, c;
+  // message a: {
+  //   rv: 0
+  //   rv: 1
+  //   rv: 0
+  // }
+  a.add_rv(0);
+  a.add_rv(1);
+  a.add_rv(0);
+  // message b: {
+  //   rv: 0
+  //   rv: 0
+  //   rv: 1
+  // }
+  b.add_rv(0);
+  b.add_rv(0);
+  b.add_rv(1);
+  // message c: {
+  //   rv: 0
+  //   rv: 1
+  // }
+  c.add_rv(0);
+  c.add_rv(1);
+  util::MessageDifferencer differencer;
+  differencer.TreatAsSet(GetFieldDescriptor(a, "rv"));
+  EXPECT_TRUE(differencer.Compare(b, a));
+  EXPECT_FALSE(differencer.Compare(c, a));
+
+  util::MessageDifferencer differencer1;
+  differencer1.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_TRUE(differencer1.Compare(b, a));
+  EXPECT_FALSE(differencer1.Compare(c, a));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_PartialSimple) {
+  protobuf_unittest::TestDiffMessage a, b, c;
+  // message a: {
+  //   rm { c: 1 }
+  //   rm { c: 0 }
+  // }
+  a.add_rm()->set_c(1);
+  a.add_rm()->set_c(0);
+  // message b: {
+  //   rm { c: 1 }
+  //   rm {}
+  // }
+  b.add_rm()->set_c(1);
+  b.add_rm();
+  // message c: {
+  //   rm {}
+  //   rm { c: 1 }
+  // }
+  c.add_rm();
+  c.add_rm()->set_c(1);
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.TreatAsSet(GetFieldDescriptor(a, "rm"));
+  EXPECT_TRUE(differencer.Compare(b, a));
+  EXPECT_TRUE(differencer.Compare(c, a));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Partial) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  // message msg1: {
+  //   rm { a: 1 }
+  //   rm { b: 2 }
+  //   rm { c: 3 }
+  // }
+  msg1.add_rm()->set_a(1);
+  msg1.add_rm()->set_b(2);
+  msg1.add_rm()->set_c(3);
+  // message msg2: {
+  //   rm { a: 1; c: 3 }
+  //   rm { b: 2; c: 3 }
+  //   rm { b: 2 }
+  // }
+  protobuf_unittest::TestField* field = msg2.add_rm();
+  field->set_a(1);
+  field->set_c(3);
+  field = msg2.add_rm();
+  field->set_b(2);
+  field->set_c(3);
+  field = msg2.add_rm();
+  field->set_b(2);
+
+  util::MessageDifferencer differencer;
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.TreatAsSet(GetFieldDescriptor(msg1, "rm"));
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_MultipleFieldsAsKey) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = ("a", "ra")
+  // Treat "item.ra" as Set
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->set_a(1);
+  item->add_ra(2);
+  item->add_ra(3);
+  item->set_b("a");
+  item = msg1.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->set_a(2);
+  item->add_ra(1);
+  item->add_ra(3);
+  item->set_b("b");
+  item = msg1.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->set_a(1);
+  item->add_ra(1);
+  item->add_ra(3);
+  item->set_b("c");
+
+  item = msg2.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->set_a(1);
+  item->add_ra(3);
+  item->add_ra(1);
+  item->set_b("c");
+  item = msg2.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->set_a(1);
+  item->add_ra(3);
+  item->add_ra(2);
+  item->set_b("a");
+  item = msg2.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->set_a(2);
+  item->add_ra(3);
+  item->add_ra(1);
+  item->set_b("b");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsSet(GetFieldDescriptor(msg1, "item.ra"));
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  vector<const FieldDescriptor*> key_fields;
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.a"));
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.ra"));
+  differencer.TreatAsMapWithMultipleFieldsAsKey(
+      GetFieldDescriptor(msg1, "item"), key_fields);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Introduce some differences.
+  msg1.clear_item();
+  msg2.clear_item();
+  item = msg1.add_item();
+  item->set_a(4);
+  item->add_ra(5);
+  item->add_ra(6);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->set_a(4);
+  item->add_ra(6);
+  item->add_ra(5);
+  item->set_b("world");
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "moved: item[0].ra[0] -> item[0].ra[1] : 5\n"
+      "moved: item[0].ra[1] -> item[0].ra[0] : 6\n"
+      "modified: item[0].b: \"hello\" -> \"world\"\n",
+      output);
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_MultipleFieldPathsAsKey) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = ("m.a", "m.rc")
+  // Treat "item.m.rc" as Set
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(2);
+  item->mutable_m()->add_rc(3);
+  item->set_b("a");
+  item = msg1.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->mutable_m()->set_a(2);
+  item->mutable_m()->add_rc(1);
+  item->mutable_m()->add_rc(3);
+  item->set_b("b");
+  item = msg1.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(1);
+  item->mutable_m()->add_rc(3);
+  item->set_b("c");
+
+  item = msg2.add_item();
+  // key => value: (1, {1, 3}) => "c"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(3);
+  item->mutable_m()->add_rc(1);
+  item->set_b("c");
+  item = msg2.add_item();
+  // key => value: (1, {2, 3}) => "a"
+  item->mutable_m()->set_a(1);
+  item->mutable_m()->add_rc(3);
+  item->mutable_m()->add_rc(2);
+  item->set_b("a");
+  item = msg2.add_item();
+  // key => value: (2, {1, 3}) => "b"
+  item->mutable_m()->set_a(2);
+  item->mutable_m()->add_rc(3);
+  item->mutable_m()->add_rc(1);
+  item->set_b("b");
+
+  // Compare
+  util::MessageDifferencer differencer;
+  differencer.TreatAsSet(GetFieldDescriptor(msg1, "item.m.rc"));
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  vector<vector<const FieldDescriptor*> > key_field_paths;
+  vector<const FieldDescriptor*> key_field_path1;
+  key_field_path1.push_back(GetFieldDescriptor(msg1, "item.m"));
+  key_field_path1.push_back(GetFieldDescriptor(msg1, "item.m.a"));
+  vector<const FieldDescriptor*> key_field_path2;
+  key_field_path2.push_back(GetFieldDescriptor(msg1, "item.m"));
+  key_field_path2.push_back(GetFieldDescriptor(msg1, "item.m.rc"));
+  key_field_paths.push_back(key_field_path1);
+  key_field_paths.push_back(key_field_path2);
+  differencer.TreatAsMapWithMultipleFieldPathsAsKey(
+      GetFieldDescriptor(msg1, "item"), key_field_paths);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+
+  // Introduce some differences.
+  msg1.clear_item();
+  msg2.clear_item();
+  item = msg1.add_item();
+  item->mutable_m()->set_a(4);
+  item->mutable_m()->add_rc(5);
+  item->mutable_m()->add_rc(6);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->mutable_m()->set_a(4);
+  item->mutable_m()->add_rc(6);
+  item->mutable_m()->add_rc(5);
+  item->set_b("world");
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "modified: item[0].b: \"hello\" -> \"world\"\n"
+      "moved: item[0].m.rc[0] -> item[0].m.rc[1] : 5\n"
+      "moved: item[0].m.rc[1] -> item[0].m.rc[0] : 6\n",
+      output);
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_IgnoredKeyFields) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, with key = ("a", "ra")
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(1);
+  item->add_ra(2);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->set_a(1);
+  item->add_ra(3);
+  item->set_b("world");
+  // Compare
+  util::MessageDifferencer differencer;
+  vector<const FieldDescriptor*> key_fields;
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.a"));
+  key_fields.push_back(GetFieldDescriptor(msg1, "item.ra"));
+  differencer.TreatAsMapWithMultipleFieldsAsKey(
+      GetFieldDescriptor(msg1, "item"), key_fields);
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "added: item[0]: { a: 1 ra: 3 b: \"world\" }\n"
+      "deleted: item[0]: { a: 1 ra: 2 b: \"hello\" }\n",
+      output);
+  // Ignored fields that are listed as parts of the key are still used
+  // in key comparison, but they're not used in value comparison.
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item.ra"));
+  output.clear();
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "added: item[0]: { a: 1 ra: 3 b: \"world\" }\n"
+      "deleted: item[0]: { a: 1 ra: 2 b: \"hello\" }\n",
+      output);
+  // Ignoring a field in the key is different from treating the left fields
+  // as key. That is:
+  //   (key = ("a", "ra") && ignore "ra") != (key = ("a") && ignore "ra")
+  util::MessageDifferencer differencer2;
+  differencer2.TreatAsMap(GetFieldDescriptor(msg1, "item"),
+                          GetFieldDescriptor(msg1, "item.a"));
+  differencer2.IgnoreField(GetFieldDescriptor(msg1, "item.ra"));
+  output.clear();
+  differencer2.ReportDifferencesToString(&output);
+  EXPECT_FALSE(differencer2.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "ignored: item[0].ra\n"
+      "modified: item[0].b: \"hello\" -> \"world\"\n",
+      output);
+}
+
+static const char* const kIgnoredFields[] = {"rm.b", "rm.m.b"};
+
+class TestIgnorer : public util::MessageDifferencer::IgnoreCriteria {
+ public:
+  virtual bool IsIgnored(
+      const Message& message1, const Message& message2,
+      const FieldDescriptor* field,
+      const vector<util::MessageDifferencer::SpecificField>& parent_fields) {
+    string name = "";
+    for (int i = 0; i < parent_fields.size(); ++i) {
+      name += parent_fields[i].field->name() + ".";
+    }
+    name += field->name();
+    for (int i = 0; i < GOOGLE_ARRAYSIZE(kIgnoredFields); ++i) {
+      if (name.compare(kIgnoredFields[i]) == 0) {
+        return true;
+      }
+    }
+    return false;
+  }
+};
+
+TEST(MessageDifferencerTest, TreatRepeatedFieldAsSetWithIgnoredFields) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  TextFormat::MergeFromString("rm { a: 11\n b: 12 }", &msg1);
+  TextFormat::MergeFromString("rm { a: 11\n b: 13 }", &msg2);
+  util::MessageDifferencer differ;
+  differ.TreatAsSet(GetFieldDescriptor(msg1, "rm"));
+  differ.AddIgnoreCriteria(new TestIgnorer);
+  EXPECT_TRUE(differ.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, TreatRepeatedFieldAsMapWithIgnoredKeyFields) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  TextFormat::MergeFromString("rm { a: 11\n m { a: 12\n b: 13\n } }", &msg1);
+  TextFormat::MergeFromString("rm { a: 11\n m { a: 12\n b: 14\n } }", &msg2);
+  util::MessageDifferencer differ;
+  differ.TreatAsMap(GetFieldDescriptor(msg1, "rm"),
+                    GetFieldDescriptor(msg1, "rm.m"));
+  differ.AddIgnoreCriteria(new TestIgnorer);
+  EXPECT_TRUE(differ.Compare(msg1, msg2));
+}
+
+// Takes the product of all elements of item.ra as the key for key comparison.
+class ValueProductMapKeyComparator
+    : public util::MessageDifferencer::MapKeyComparator {
+ public:
+  typedef util::MessageDifferencer::SpecificField SpecificField;
+  virtual bool IsMatch(
+      const Message &message1, const Message &message2,
+      const vector<SpecificField>& parent_fields) const {
+    const Reflection* reflection1 = message1.GetReflection();
+    const Reflection* reflection2 = message2.GetReflection();
+    // FieldDescriptor for item.ra
+    const FieldDescriptor* ra_field =
+        message1.GetDescriptor()->FindFieldByName("ra");
+    // Get the product of all elements in item.ra
+    int result1 = 1, result2 = 1;
+    for (int i = 0; i < reflection1->FieldSize(message1, ra_field); ++i) {
+      result1 *= reflection1->GetRepeatedInt32(message1, ra_field, i);
+    }
+    for (int i = 0; i < reflection2->FieldSize(message2, ra_field); ++i) {
+      result2 *= reflection2->GetRepeatedInt32(message2, ra_field, i);
+    }
+    return result1 == result2;
+  }
+};
+
+TEST(MessageDifferencerTest, RepeatedFieldMapTest_CustomMapKeyComparator) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  // Treat "item" as Map, using custom key comparator to determine if two
+  // elements have the same key.
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_ra(6);
+  item->add_ra(35);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->add_ra(10);
+  item->add_ra(21);
+  item->set_b("hello");
+  util::MessageDifferencer differencer;
+  ValueProductMapKeyComparator key_comparator;
+  differencer.TreatAsMapUsingKeyComparator(
+      GetFieldDescriptor(msg1, "item"), &key_comparator);
+  string output;
+  differencer.ReportDifferencesToString(&output);
+  // Though the above two messages have different values for item.ra, they
+  // are regarded as having the same key because 6 * 35 == 10 * 21. That's
+  // how the key comparator determines if the two have the same key.
+  // However, in value comparison, all fields of the message are taken into
+  // consideration, so they are different because their item.ra fields have
+  // different values using normal value comparison.
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "modified: item[0].ra[0]: 6 -> 10\n"
+      "modified: item[0].ra[1]: 35 -> 21\n",
+      output);
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item.ra"));
+  output.clear();
+  // item.ra is ignored in value comparison, so the two messages equal.
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ("ignored: item[0].ra\n", output);
+}
+
+TEST(MessageDifferencerTest, RepeatedFieldSetTest_Subset) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  msg1.add_rv(3);
+  msg1.add_rv(8);
+  msg1.add_rv(2);
+  msg2.add_rv(2);
+  msg2.add_rv(3);
+  msg2.add_rv(5);
+  msg2.add_rv(8);
+
+  util::MessageDifferencer differencer;
+
+  // Fail with only partial scope set.
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_LIST);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Fail with only set-like comparison set.
+  differencer.set_scope(util::MessageDifferencer::FULL);
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+  // Succeed with scope and repeated field comparison set properly.
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  differencer.set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Single) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+
+  msg2.set_c(5);
+  msg2.add_rc(1);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "c"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Repeated) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+  msg1.add_rc(2);
+
+  msg2.set_c(3);
+  msg2.add_rc(1);
+  msg2.add_rc(3);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "rc"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Message) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestField* field;
+
+  field = msg1.add_rm();
+  field->set_c(3);
+
+  field = msg2.add_rm();
+  field->set_c(4);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "rm"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Group) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(3);
+
+  item = msg2.add_item();
+  item->set_a(4);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Missing) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+
+  msg2.add_rc(1);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "c"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+  ExpectEqualsWithDifferencer(&differencer, msg2, msg1);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_Multiple) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+  msg1.add_rc(2);
+
+  msg2.set_c(5);
+  msg2.add_rc(1);
+  msg2.add_rc(3);
+
+  const FieldDescriptor* c = GetFieldDescriptor(msg1, "c");
+  const FieldDescriptor* rc = GetFieldDescriptor(msg1, "rc");
+
+  { // Ignore c
+    util::MessageDifferencer differencer;
+    differencer.IgnoreField(c);
+
+    EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  }
+  { // Ignore rc
+    util::MessageDifferencer differencer;
+    differencer.IgnoreField(rc);
+
+    EXPECT_FALSE(differencer.Compare(msg1, msg2));
+  }
+  { // Ignore both
+    util::MessageDifferencer differencer;
+    differencer.IgnoreField(c);
+    differencer.IgnoreField(rc);
+
+    ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+  }
+}
+
+TEST(MessageDifferencerTest, IgnoreField_NestedMessage) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestField* field;
+
+  field = msg1.add_rm();
+  field->set_c(3);
+  field->add_rc(1);
+
+  field = msg2.add_rm();
+  field->set_c(4);
+  field->add_rc(1);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "rm.c"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_NestedGroup) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(3);
+  item->set_b("foo");
+
+  item = msg2.add_item();
+  item->set_a(4);
+  item->set_b("foo");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(GetFieldDescriptor(msg1, "item.a"));
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_InsideSet) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  item = msg1.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(1);
+  item->set_b("baz");
+  item->add_ra(1);
+
+  const FieldDescriptor* item_desc = GetFieldDescriptor(msg1, "item");
+  const FieldDescriptor* b = GetFieldDescriptor(msg1, "item.b");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(b);
+  differencer.TreatAsSet(item_desc);
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_InsideMap) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  item = msg1.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("bar");
+  item->add_ra(2);
+
+  item = msg2.add_item();
+  item->set_a(1);
+  item->set_b("baz");
+  item->add_ra(1);
+
+  const FieldDescriptor* item_desc = GetFieldDescriptor(msg1, "item");
+  const FieldDescriptor* a = GetFieldDescriptor(msg1, "item.a");
+  const FieldDescriptor* b = GetFieldDescriptor(msg1, "item.b");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(b);
+  differencer.TreatAsMap(item_desc, a);
+
+  ExpectEqualsWithDifferencer(&differencer, msg1, msg2);
+}
+
+TEST(MessageDifferencerTest, IgnoreField_DoesNotIgnoreKey) {
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item;
+
+  item = msg1.add_item();
+  item->set_a(1);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  item = msg2.add_item();
+  item->set_a(2);
+  item->set_b("foo");
+  item->add_ra(1);
+
+  const FieldDescriptor* item_desc = GetFieldDescriptor(msg1, "item");
+  const FieldDescriptor* a = GetFieldDescriptor(msg1, "item.a");
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(a);
+  differencer.TreatAsMap(item_desc, a);
+
+  EXPECT_FALSE(differencer.Compare(msg1, msg2));
+}
+
+TEST(MessageDifferencerTest, IgnoreField_TrumpsCompareWithFields) {
+  protobuf_unittest::TestField msg1;
+  protobuf_unittest::TestField msg2;
+
+  msg1.set_c(3);
+  msg1.add_rc(1);
+  msg1.add_rc(2);
+
+  msg2.set_c(3);
+  msg2.add_rc(1);
+  msg2.add_rc(3);
+
+  const FieldDescriptor* c = GetFieldDescriptor(msg1, "c");
+  const FieldDescriptor* rc = GetFieldDescriptor(msg1, "rc");
+
+  vector<const FieldDescriptor*> fields;
+  fields.push_back(c);
+  fields.push_back(rc);
+
+  util::MessageDifferencer differencer;
+  differencer.IgnoreField(rc);
+
+  differencer.set_scope(util::MessageDifferencer::FULL);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields, fields));
+
+  differencer.set_scope(util::MessageDifferencer::PARTIAL);
+  EXPECT_TRUE(differencer.CompareWithFields(msg1, msg2, fields, fields));
+}
+
+
+// Test class to save a copy of the last field_context.parent_fields() vector
+// passed to the comparison function.
+class ParentSavingFieldComparator : public util::FieldComparator {
+ public:
+  ParentSavingFieldComparator() {}
+
+  virtual ComparisonResult Compare(
+      const google::protobuf::Message& message_1,
+      const google::protobuf::Message& message_2,
+      const google::protobuf::FieldDescriptor* field,
+      int index_1, int index_2,
+      const google::protobuf::util::FieldContext* field_context) {
+    if (field_context)
+      parent_fields_ = *(field_context->parent_fields());
+    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
+      return RECURSE;
+    } else {
+      return SAME;
+    }
+  }
+
+  vector<google::protobuf::util::MessageDifferencer::SpecificField> parent_fields() {
+    return parent_fields_;
+  }
+
+ private:
+  vector<google::protobuf::util::MessageDifferencer::SpecificField> parent_fields_;
+};
+
+// Tests if MessageDifferencer sends the parent fields in the FieldContext
+// parameter.
+TEST(MessageDifferencerTest, FieldContextParentFieldsTest) {
+  protobuf_unittest::TestDiffMessage msg1;
+  msg1.add_rm()->set_c(1);
+  protobuf_unittest::TestDiffMessage msg2;
+  msg2.add_rm()->set_c(1);
+
+  ParentSavingFieldComparator field_comparator;
+  util::MessageDifferencer differencer;
+  differencer.set_field_comparator(&field_comparator);
+  differencer.Compare(msg1, msg2);
+
+  // We want only one parent with the name "rm"
+  ASSERT_EQ(1, field_comparator.parent_fields().size());
+  EXPECT_EQ("rm", field_comparator.parent_fields()[0].field->name());
+}
+
+
+class ComparisonTest : public testing::Test {
+ protected:
+  ComparisonTest() : use_equivalency_(false), repeated_field_as_set_(false) {
+    // Setup the test.
+    TestUtil::SetAllFields(&proto1_);
+    TestUtil::SetAllFields(&proto2_);
+
+    TestUtil::SetAllExtensions(&proto1ex_);
+    TestUtil::SetAllExtensions(&proto2ex_);
+
+    TestUtil::SetAllFieldsAndExtensions(&orderings_proto1_);
+    TestUtil::SetAllFieldsAndExtensions(&orderings_proto2_);
+
+    unknown1_ = empty1_.mutable_unknown_fields();
+    unknown2_ = empty2_.mutable_unknown_fields();
+  }
+
+  ~ComparisonTest() { }
+
+  void SetSpecialFieldOption(const Message& message,
+                              util::MessageDifferencer* d) {
+    if (!ignored_field_.empty()) {
+      d->IgnoreField(GetFieldDescriptor(message, ignored_field_));
+    }
+
+    if (repeated_field_as_set_) {
+      d->set_repeated_field_comparison(util::MessageDifferencer::AS_SET);
+    }
+
+    if (!set_field_.empty()) {
+      d->TreatAsSet(GetFieldDescriptor(message, set_field_));
+    }
+
+    if (!map_field_.empty() && !map_key_.empty()) {
+      d->TreatAsMap(GetFieldDescriptor(message, map_field_),
+                    GetFieldDescriptor(message, map_field_ + "." + map_key_));
+    }
+  }
+
+  string Run(const Message& msg1, const Message& msg2) {
+    string output;
+
+    // Setup the comparison.
+    util::MessageDifferencer differencer;
+    differencer.ReportDifferencesToString(&output);
+
+    if (use_equivalency_) {
+      differencer.set_message_field_comparison(
+          util::MessageDifferencer::EQUIVALENT);
+    }
+
+    SetSpecialFieldOption(msg1, &differencer);
+
+    // Conduct the comparison.
+    EXPECT_FALSE(differencer.Compare(msg1, msg2));
+
+    return output;
+  }
+
+  string Run() {
+    return Run(proto1_, proto2_);
+  }
+
+  string RunOrder() {
+    return Run(orderings_proto1_, orderings_proto2_);
+  }
+
+  string RunEx() {
+    return Run(proto1ex_, proto2ex_);
+  }
+
+  string RunDiff() {
+    return Run(proto1diff_, proto2diff_);
+  }
+
+  string RunUn() {
+    return Run(empty1_, empty2_);
+  }
+
+  void use_equivalency() {
+    use_equivalency_ = true;
+  }
+
+  void repeated_field_as_set() {
+    repeated_field_as_set_ = true;
+  }
+
+  void field_as_set(const string& field) {
+    set_field_ = field;
+  }
+
+  void field_as_map(const string& field, const string& key) {
+    map_field_ = field;
+    map_key_   = key;
+  }
+
+  void ignore_field(const string& field) {
+    ignored_field_ = field;
+  }
+
+  unittest::TestAllTypes proto1_;
+  unittest::TestAllTypes proto2_;
+
+  unittest::TestFieldOrderings orderings_proto1_;
+  unittest::TestFieldOrderings orderings_proto2_;
+
+  unittest::TestAllExtensions proto1ex_;
+  unittest::TestAllExtensions proto2ex_;
+
+  unittest::TestDiffMessage proto1diff_;
+  unittest::TestDiffMessage proto2diff_;
+
+  unittest::TestEmptyMessage empty1_;
+  unittest::TestEmptyMessage empty2_;
+
+  UnknownFieldSet* unknown1_;
+  UnknownFieldSet* unknown2_;
+
+  bool use_equivalency_;
+  bool repeated_field_as_set_;
+
+  string set_field_;
+  string map_field_;
+  string map_key_;
+  string ignored_field_;
+};
+
+// Basic tests.
+TEST_F(ComparisonTest, AdditionTest) {
+  proto1_.clear_optional_int32();
+
+  EXPECT_EQ("added: optional_int32: 101\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, Addition_OrderTest) {
+  orderings_proto1_.clear_my_int();
+
+  EXPECT_EQ("added: my_int: 1\n",
+            RunOrder());
+}
+
+TEST_F(ComparisonTest, DeletionTest) {
+  proto2_.clear_optional_int32();
+
+  EXPECT_EQ("deleted: optional_int32: 101\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, Deletion_OrderTest) {
+  orderings_proto2_.clear_my_string();
+
+  EXPECT_EQ("deleted: my_string: \"foo\"\n",
+            RunOrder());
+}
+
+TEST_F(ComparisonTest, RepeatedDeletionTest) {
+  proto2_.clear_repeated_int32();
+
+  EXPECT_EQ("deleted: repeated_int32[0]: 201\n"
+            "deleted: repeated_int32[1]: 301\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, ModificationTest) {
+  proto1_.set_optional_int32(-1);
+
+  EXPECT_EQ("modified: optional_int32: -1 -> 101\n",
+            Run());
+}
+
+// Basic equivalency tests.
+TEST_F(ComparisonTest, EquivalencyAdditionTest) {
+  use_equivalency();
+
+  proto1_.clear_optional_int32();
+
+  EXPECT_EQ("modified: optional_int32: 0 -> 101\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EquivalencyDeletionTest) {
+  use_equivalency();
+
+  proto2_.clear_optional_int32();
+
+  EXPECT_EQ("modified: optional_int32: 101 -> 0\n",
+            Run());
+}
+
+// Group tests.
+TEST_F(ComparisonTest, GroupAdditionTest) {
+  proto1_.mutable_optionalgroup()->clear_a();
+
+  EXPECT_EQ("added: optionalgroup.a: 117\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupDeletionTest) {
+  proto2_.mutable_optionalgroup()->clear_a();
+
+  EXPECT_EQ("deleted: optionalgroup.a: 117\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupModificationTest) {
+  proto1_.mutable_optionalgroup()->set_a(2);
+
+  EXPECT_EQ("modified: optionalgroup.a: 2 -> 117\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupFullAdditionTest) {
+  proto1_.clear_optionalgroup();
+
+  // Note the difference in the output between this and GroupAdditionTest.
+  EXPECT_EQ("added: optionalgroup: { a: 117 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, GroupFullDeletionTest) {
+  proto2_.clear_optionalgroup();
+
+  EXPECT_EQ("deleted: optionalgroup: { a: 117 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, RepeatedSetOptionTest) {
+  repeated_field_as_set();
+
+  proto2_.clear_repeatedgroup();
+  proto1_.clear_repeatedgroup();
+  proto1_.add_repeatedgroup()->set_a(317);
+  proto2_.add_repeatedgroup()->set_a(909);
+  proto2_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(904);
+  proto1_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(909);
+
+  EXPECT_EQ("moved: repeatedgroup[2] -> repeatedgroup[1] : { a: 907 }\n"
+            "moved: repeatedgroup[3] -> repeatedgroup[0] : { a: 909 }\n"
+            "deleted: repeatedgroup[0]: { a: 317 }\n"
+            "deleted: repeatedgroup[1]: { a: 904 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, RepeatedSetOptionTest_Ex) {
+  repeated_field_as_set();
+
+  proto1ex_.ClearExtension(protobuf_unittest::repeated_nested_message_extension);
+  proto2ex_.ClearExtension(protobuf_unittest::repeated_nested_message_extension);
+  proto2ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(909);
+  proto2ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(907);
+  proto1ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(904);
+  proto1ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(907);
+  proto1ex_.AddExtension(protobuf_unittest::repeated_nested_message_extension)
+      ->set_bb(909);
+
+  EXPECT_EQ("moved: (protobuf_unittest.repeated_nested_message_extension)[2] ->"
+            " (protobuf_unittest.repeated_nested_message_extension)[0] :"
+            " { bb: 909 }\n"
+            "deleted: (protobuf_unittest.repeated_nested_message_extension)[0]:"
+            " { bb: 904 }\n",
+            RunEx());
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_Group) {
+  field_as_map("repeatedgroup", "a");
+  proto1_.clear_repeatedgroup();
+  proto2_.clear_repeatedgroup();
+
+  proto1_.add_repeatedgroup()->set_a(317);  // deleted
+  proto1_.add_repeatedgroup()->set_a(904);  // deleted
+  proto1_.add_repeatedgroup()->set_a(907);  // moved from
+  proto1_.add_repeatedgroup()->set_a(909);  // moved from
+
+  proto2_.add_repeatedgroup()->set_a(909);  // moved to
+  proto2_.add_repeatedgroup()->set_a(318);  // added
+  proto2_.add_repeatedgroup()->set_a(907);  // moved to
+
+  EXPECT_EQ("moved: repeatedgroup[3] -> repeatedgroup[0] : { a: 909 }\n"
+            "added: repeatedgroup[1]: { a: 318 }\n"
+            "deleted: repeatedgroup[0]: { a: 317 }\n"
+            "deleted: repeatedgroup[1]: { a: 904 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_MessageKey) {
+  // Use m as key, but use b as value.
+  field_as_map("item", "m");
+
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+
+  // The following code creates one deletion, one addition and two moved fields
+  // on the messages.
+  item->mutable_m()->set_c(0);
+  item->set_b("first");
+  item = msg1.add_item();
+  item->mutable_m()->set_c(2);
+  item->set_b("second");
+  item = msg1.add_item(); item->set_b("null");  // empty key moved
+  item = msg1.add_item();
+  item->mutable_m()->set_c(3);
+  item->set_b("third");   // deletion
+  item = msg1.add_item();
+  item->mutable_m()->set_c(2);
+  item->set_b("second");  // duplicated key ( deletion )
+  item = msg2.add_item();
+  item->mutable_m()->set_c(2);
+  item->set_b("second");  // modification
+  item = msg2.add_item();
+  item->mutable_m()->set_c(4);
+  item->set_b("fourth");  // addition
+  item = msg2.add_item();
+  item->mutable_m()->set_c(0);
+  item->set_b("fist");    // move with change
+  item = msg2.add_item(); item->set_b("null");
+
+  EXPECT_EQ(
+      "modified: item[0].b -> item[2].b: \"first\" -> \"fist\"\n"
+      "moved: item[1] -> item[0] : { b: \"second\" m { c: 2 } }\n"
+      "moved: item[2] -> item[3] : { b: \"null\" }\n"
+      "added: item[1]: { b: \"fourth\" m { c: 4 } }\n"
+      "deleted: item[3]: { b: \"third\" m { c: 3 } }\n"
+      "deleted: item[4]: { b: \"second\" m { c: 2 } }\n",
+      Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedFieldSetTest_SetOfSet) {
+  repeated_field_as_set();
+  // Create the testing protos
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_ra(1); item->add_ra(2); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(5); item->add_ra(6);
+  item = msg1.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg1.add_item();
+  item->add_ra(6); item->add_ra(7); item->add_ra(8);
+
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(5);
+  item = msg2.add_item();
+  item->add_ra(6); item->add_ra(8);
+  item = msg2.add_item();
+  item->add_ra(1); item->add_ra(3);
+  item = msg2.add_item();
+  item->add_ra(3); item->add_ra(2); item->add_ra(1);
+
+  // Compare
+  EXPECT_EQ("moved: item[0].ra[0] -> item[3].ra[2] : 1\n"
+            "moved: item[0].ra[2] -> item[3].ra[0] : 3\n"
+            "moved: item[0] -> item[3] : { ra: 1 ra: 2 ra: 3 }\n"
+            "moved: item[1].ra[0] -> item[0].ra[1] : 5\n"
+            "moved: item[1].ra[1] -> item[0].ra[0] : 6\n"
+            "moved: item[1] -> item[0] : { ra: 5 ra: 6 }\n"
+            "added: item[1]: { ra: 6 ra: 8 }\n"
+            "deleted: item[3]: { ra: 6 ra: 7 ra: 8 }\n",
+            Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_RepeatedKey) {
+  // used rb as a key, but b is the value.
+  repeated_field_as_set();
+  field_as_map("item", "rb");
+
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->add_rb("a");
+  item->add_rb("b");
+  item->set_b("first");
+
+  item = msg2.add_item();
+  item->add_rb("c");
+  item->set_b("second");
+
+  item = msg2.add_item();
+  item->add_rb("b");
+  item->add_rb("a");
+  item->set_b("fist");
+
+
+  EXPECT_EQ("modified: item[0].b -> item[1].b: \"first\" -> \"fist\"\n"
+            "moved: item[0].rb[0] -> item[1].rb[1] : \"a\"\n"
+            "moved: item[0].rb[1] -> item[1].rb[0] : \"b\"\n"
+            "added: item[0]: { b: \"second\" rb: \"c\" }\n",
+            Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedMapFieldTest_RepeatedMessageKey) {
+  field_as_map("item", "rm");
+
+  protobuf_unittest::TestDiffMessage msg1;
+  protobuf_unittest::TestDiffMessage msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  protobuf_unittest::TestField* key = item->add_rm();
+  key->set_c(2); key->add_rc(10); key->add_rc(10);
+  item = msg1.add_item(); key = item->add_rm();
+  key->set_c(0); key->add_rc(1); key->add_rc(2);
+  key = item->add_rm();
+  key->set_c(0);
+  item->add_rb("first");
+
+  item = msg2.add_item();
+  item->CopyFrom(msg1.item(1));
+  item->add_rb("second");
+
+  EXPECT_EQ("added: item[0].rb[1]: \"second\"\n"
+            "deleted: item[0]: { rm { c: 2 rc: 10 rc: 10 } }\n",
+            Run(msg1, msg2));
+}
+
+TEST_F(ComparisonTest, RepeatedSetOptionTest_Unknown) {
+  // Currently, as_set option doens't have affects on unknown field.
+  // If needed, this feature will be added by request.
+  repeated_field_as_set();
+  unknown1_->AddGroup(245)->AddFixed32(248, 1);
+  unknown2_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddGroup(245)->AddFixed32(248, 1);
+
+  // We expect it behaves the same as normal comparison.
+  EXPECT_EQ("modified: 245[0].248[0]: 0x00000001 -> 0x00000003\n"
+            "added: 245[1]: { ... }\n",
+            RunUn());
+}
+
+TEST_F(ComparisonTest, Matching_Unknown) {
+  unknown1_->AddGroup(245)->AddFixed32(248, 1);
+  unknown2_->AddGroup(245)->AddFixed32(248, 1);
+  unknown1_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddLengthDelimited(242, "cat");
+  unknown2_->AddGroup(246)->AddFixed32(248, 4);
+
+  // report_match is false so only added/modified fields are expected.
+  EXPECT_EQ("added: 242[0]: \"cat\"\n"
+            "added: 246[0]: { ... }\n",
+            RunUn());
+}
+
+TEST_F(ComparisonTest, RepeatedSetFieldTest) {
+  field_as_set("repeatedgroup");
+
+  proto1_.clear_repeatedgroup();
+  proto2_.clear_repeatedgroup();
+  proto2_.add_repeatedgroup()->set_a(909);
+  proto2_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(317);
+  proto1_.add_repeatedgroup()->set_a(904);
+  proto1_.add_repeatedgroup()->set_a(907);
+  proto1_.add_repeatedgroup()->set_a(909);
+
+  EXPECT_EQ("moved: repeatedgroup[2] -> repeatedgroup[1] : { a: 907 }\n"
+            "moved: repeatedgroup[3] -> repeatedgroup[0] : { a: 909 }\n"
+            "deleted: repeatedgroup[0]: { a: 317 }\n"
+            "deleted: repeatedgroup[1]: { a: 904 }\n",
+            Run());
+}
+
+// Embedded message tests.
+TEST_F(ComparisonTest, EmbeddedAdditionTest) {
+  proto1_.mutable_optional_nested_message()->clear_bb();
+
+  EXPECT_EQ("added: optional_nested_message.bb: 118\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedDeletionTest) {
+  proto2_.mutable_optional_nested_message()->clear_bb();
+
+  EXPECT_EQ("deleted: optional_nested_message.bb: 118\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedModificationTest) {
+  proto1_.mutable_optional_nested_message()->set_bb(2);
+
+  EXPECT_EQ("modified: optional_nested_message.bb: 2 -> 118\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedFullAdditionTest) {
+  proto1_.clear_optional_nested_message();
+
+  EXPECT_EQ("added: optional_nested_message: { bb: 118 }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedPartialAdditionTest) {
+  proto1_.clear_optional_nested_message();
+  proto2_.mutable_optional_nested_message()->clear_bb();
+
+  EXPECT_EQ("added: optional_nested_message: { }\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, EmbeddedFullDeletionTest) {
+  proto2_.clear_optional_nested_message();
+
+  EXPECT_EQ("deleted: optional_nested_message: { bb: 118 }\n",
+            Run());
+}
+
+// Repeated element tests.
+TEST_F(ComparisonTest, BasicRepeatedTest) {
+  proto1_.clear_repeated_int32();
+  proto2_.clear_repeated_int32();
+
+  proto1_.add_repeated_int32(500);
+  proto1_.add_repeated_int32(501);
+  proto1_.add_repeated_int32(502);
+  proto1_.add_repeated_int32(503);
+  proto1_.add_repeated_int32(500);
+
+  proto2_.add_repeated_int32(500);
+  proto2_.add_repeated_int32(509);
+  proto2_.add_repeated_int32(502);
+  proto2_.add_repeated_int32(504);
+
+  EXPECT_EQ("modified: repeated_int32[1]: 501 -> 509\n"
+            "modified: repeated_int32[3]: 503 -> 504\n"
+            "deleted: repeated_int32[4]: 500\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, BasicRepeatedTest_SetOption) {
+  repeated_field_as_set();
+  proto1_.clear_repeated_int32();
+  proto2_.clear_repeated_int32();
+
+  proto1_.add_repeated_int32(501);
+  proto1_.add_repeated_int32(502);
+  proto1_.add_repeated_int32(503);
+  proto1_.add_repeated_int32(500);
+  proto1_.add_repeated_int32(500);
+
+  proto2_.add_repeated_int32(500);
+  proto2_.add_repeated_int32(509);
+  proto2_.add_repeated_int32(503);
+  proto2_.add_repeated_int32(502);
+  proto2_.add_repeated_int32(504);
+
+  EXPECT_EQ("moved: repeated_int32[1] -> repeated_int32[3] : 502\n"
+            "moved: repeated_int32[3] -> repeated_int32[0] : 500\n"
+            "added: repeated_int32[1]: 509\n"
+            "added: repeated_int32[4]: 504\n"
+            "deleted: repeated_int32[0]: 501\n"
+            "deleted: repeated_int32[4]: 500\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, BasicRepeatedTest_SetField) {
+  field_as_set("repeated_int32");
+  proto1_.clear_repeated_int32();
+  proto2_.clear_repeated_int32();
+
+  proto1_.add_repeated_int32(501);
+  proto1_.add_repeated_int32(502);
+  proto1_.add_repeated_int32(503);
+  proto1_.add_repeated_int32(500);
+  proto1_.add_repeated_int32(500);
+
+  proto2_.add_repeated_int32(500);
+  proto2_.add_repeated_int32(509);
+  proto2_.add_repeated_int32(503);
+  proto2_.add_repeated_int32(502);
+  proto2_.add_repeated_int32(504);
+
+  EXPECT_EQ("moved: repeated_int32[1] -> repeated_int32[3] : 502\n"
+            "moved: repeated_int32[3] -> repeated_int32[0] : 500\n"
+            "added: repeated_int32[1]: 509\n"
+            "added: repeated_int32[4]: 504\n"
+            "deleted: repeated_int32[0]: 501\n"
+            "deleted: repeated_int32[4]: 500\n",
+            Run());
+}
+
+// Multiple action tests.
+TEST_F(ComparisonTest, AddDeleteTest) {
+  proto1_.clear_optional_int32();
+  proto2_.clear_optional_int64();
+
+  EXPECT_EQ("added: optional_int32: 101\n"
+            "deleted: optional_int64: 102\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, AddDelete_FieldOrderingTest) {
+  orderings_proto1_.ClearExtension(unittest::my_extension_string);
+  orderings_proto2_.clear_my_int();
+
+  EXPECT_EQ("deleted: my_int: 1\n"
+            "added: (protobuf_unittest.my_extension_string): \"bar\"\n",
+            RunOrder());
+}
+
+TEST_F(ComparisonTest, AllThreeTest) {
+  proto1_.clear_optional_int32();
+  proto2_.clear_optional_float();
+  proto2_.set_optional_string("hello world!");
+
+  EXPECT_EQ("added: optional_int32: 101\n"
+            "deleted: optional_float: 111\n"
+            "modified: optional_string: \"115\" -> \"hello world!\"\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, SandwhichTest) {
+  proto1_.clear_optional_int64();
+  proto1_.clear_optional_uint32();
+
+  proto2_.clear_optional_uint64();
+
+  EXPECT_EQ("added: optional_int64: 102\n"
+            "added: optional_uint32: 103\n"
+            "deleted: optional_uint64: 104\n",
+            Run());
+}
+
+TEST_F(ComparisonTest, IgnoredNoChangeTest) {
+  proto1diff_.set_v(3);
+  proto2diff_.set_v(3);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredAddTest) {
+  proto2diff_.set_v(3);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredDeleteTest) {
+  proto1diff_.set_v(3);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredModifyTest) {
+  proto1diff_.set_v(3);
+  proto2diff_.set_v(4);
+  proto2diff_.set_w("foo");
+
+  ignore_field("v");
+
+  EXPECT_EQ("ignored: v\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedAddTest) {
+  proto1diff_.add_rv(3);
+  proto1diff_.add_rv(4);
+
+  proto2diff_.add_rv(3);
+  proto2diff_.add_rv(4);
+  proto2diff_.add_rv(5);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rv");
+
+  EXPECT_EQ("ignored: rv\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedDeleteTest) {
+  proto1diff_.add_rv(3);
+  proto1diff_.add_rv(4);
+  proto1diff_.add_rv(5);
+
+  proto2diff_.add_rv(3);
+  proto2diff_.add_rv(4);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rv");
+
+  EXPECT_EQ("ignored: rv\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedModifyTest) {
+  proto1diff_.add_rv(3);
+  proto1diff_.add_rv(4);
+
+  proto2diff_.add_rv(3);
+  proto2diff_.add_rv(5);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rv");
+
+  EXPECT_EQ("ignored: rv\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredWholeNestedMessage) {
+  proto1diff_.mutable_m()->set_c(3);
+  proto2diff_.mutable_m()->set_c(4);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("m");
+
+  EXPECT_EQ("added: w: \"foo\"\n"
+            "ignored: m\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredNestedField) {
+  proto1diff_.mutable_m()->set_c(3);
+  proto2diff_.mutable_m()->set_c(4);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("m.c");
+
+  EXPECT_EQ("added: w: \"foo\"\n"
+            "ignored: m.c\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredRepeatedNested) {
+  proto1diff_.add_rm()->set_c(0);
+  proto1diff_.add_rm()->set_c(1);
+  proto2diff_.add_rm()->set_c(2);
+  proto2diff_.add_rm()->set_c(3);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("rm.c");
+
+  EXPECT_EQ("ignored: rm[0].c\n"
+            "ignored: rm[1].c\n"
+            "added: w: \"foo\"\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, IgnoredNestedRepeated) {
+  proto1diff_.mutable_m()->add_rc(23);
+  proto1diff_.mutable_m()->add_rc(24);
+  proto2diff_.mutable_m()->add_rc(25);
+
+  proto2diff_.set_w("foo");
+
+  ignore_field("m.rc");
+
+  EXPECT_EQ("added: w: \"foo\"\n"
+            "ignored: m.rc\n",
+            RunDiff());
+}
+
+TEST_F(ComparisonTest, ExtensionTest) {
+  proto1ex_.SetExtension(unittest::optional_int32_extension, 401);
+  proto2ex_.SetExtension(unittest::optional_int32_extension, 402);
+
+  proto1ex_.ClearExtension(unittest::optional_int64_extension);
+  proto2ex_.SetExtension(unittest::optional_int64_extension, 403);
+
+  EXPECT_EQ(
+      "modified: (protobuf_unittest.optional_int32_extension): 401 -> 402\n"
+      "added: (protobuf_unittest.optional_int64_extension): 403\n",
+      RunEx());
+}
+
+TEST_F(ComparisonTest, MatchedUnknownFieldTagTest) {
+  unknown1_->AddVarint(240, 122);
+  unknown2_->AddVarint(240, 121);
+  unknown1_->AddFixed32(241, 1);
+  unknown2_->AddFixed64(241, 2);
+  unknown1_->AddLengthDelimited(242, "cat");
+  unknown2_->AddLengthDelimited(242, "dog");
+
+  EXPECT_EQ(
+      "modified: 240[0]: 122 -> 121\n"
+      "deleted: 241[0]: 0x00000001\n"
+      "added: 241[0]: 0x0000000000000002\n"
+      "modified: 242[0]: \"cat\" -> \"dog\"\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, UnmatchedUnknownFieldTagTest) {
+  unknown1_->AddFixed32(243, 1);
+  unknown2_->AddVarint(244, 2);
+  unknown2_->AddVarint(244, 4);
+
+  EXPECT_EQ(
+      "deleted: 243[0]: 0x00000001\n"
+      "added: 244[0]: 2\n"
+      "added: 244[1]: 4\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, DifferentSizedUnknownFieldTest) {
+  unknown1_->AddVarint(240, 1);
+  unknown1_->AddVarint(240, 3);
+  unknown1_->AddVarint(240, 4);
+  unknown2_->AddVarint(240, 2);
+  unknown2_->AddVarint(240, 3);
+  unknown2_->AddVarint(240, 2);
+  unknown2_->AddVarint(240, 5);
+
+  EXPECT_EQ(
+      "modified: 240[0]: 1 -> 2\n"
+      "modified: 240[2]: 4 -> 2\n"
+      "added: 240[3]: 5\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, UnknownFieldsAll) {
+  unknown1_->AddVarint(243, 122);
+  unknown1_->AddFixed64(244, 0x0172356);
+  unknown1_->AddFixed64(244, 0x098);
+  unknown1_->AddGroup(245)->AddFixed32(248, 1);
+  unknown1_->mutable_field(3)->mutable_group()->AddFixed32(248, 2);
+  unknown1_->AddGroup(249)->AddFixed64(250, 1);
+
+  unknown2_->AddVarint(243, 121);
+  unknown2_->AddLengthDelimited(73882, "test 123");
+  unknown2_->AddGroup(245)->AddFixed32(248, 3);
+  unknown2_->AddGroup(247);
+
+  EXPECT_EQ(
+      "modified: 243[0]: 122 -> 121\n"
+      "deleted: 244[0]: 0x0000000000172356\n"
+      "deleted: 244[1]: 0x0000000000000098\n"
+      "modified: 245[0].248[0]: 0x00000001 -> 0x00000003\n"
+      "deleted: 245[0].248[1]: 0x00000002\n"
+      "added: 247[0]: { ... }\n"
+      "deleted: 249[0]: { ... }\n"
+      "added: 73882[0]: \"test 123\"\n",
+      RunUn());
+}
+
+TEST_F(ComparisonTest, EquivalentIgnoresUnknown) {
+  unittest::ForeignMessage message1, message2;
+
+  message1.set_c(5);
+  message1.mutable_unknown_fields()->AddVarint(123, 456);
+  message2.set_c(5);
+  message2.mutable_unknown_fields()->AddVarint(321, 654);
+
+  EXPECT_FALSE(util::MessageDifferencer::Equals(message1, message2));
+  EXPECT_TRUE(util::MessageDifferencer::Equivalent(message1, message2));
+}
+
+class MatchingTest : public testing::Test {
+ public:
+  typedef util::MessageDifferencer MessageDifferencer;
+
+ protected:
+  MatchingTest() {
+  }
+
+  ~MatchingTest() {
+  }
+
+  string RunWithResult(MessageDifferencer* differencer,
+                              const Message& msg1, const Message& msg2,
+                              bool result) {
+    string output;
+    {
+      // Before we return the "output" string, we must make sure the
+      // StreamReporter is destructored because its destructor will
+      // flush the stream.
+      io::StringOutputStream output_stream(&output);
+      MessageDifferencer::StreamReporter reporter(&output_stream);
+      reporter.set_report_modified_aggregates(true);
+      differencer->set_report_matches(true);
+      differencer->ReportDifferencesTo(&reporter);
+      if (result) {
+        EXPECT_TRUE(differencer->Compare(msg1, msg2));
+      } else {
+        EXPECT_FALSE(differencer->Compare(msg1, msg2));
+      }
+    }
+    return output;
+  }
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MatchingTest);
+};
+
+TEST_F(MatchingTest, StreamReporterMatching) {
+  protobuf_unittest::TestField msg1, msg2;
+  msg1.set_c(72);
+  msg2.set_c(72);
+  msg1.add_rc(13);
+  msg2.add_rc(13);
+  msg1.add_rc(17);
+  msg2.add_rc(17);
+  string output;
+  MessageDifferencer differencer;
+  differencer.set_report_matches(true);
+  differencer.ReportDifferencesToString(&output);
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "matched: c : 72\n"
+      "matched: rc[0] : 13\n"
+      "matched: rc[1] : 17\n",
+      output);
+}
+
+TEST_F(MatchingTest, DontReportMatchedWhenIgnoring) {
+  protobuf_unittest::TestField msg1, msg2;
+  msg1.set_c(72);
+  msg2.set_c(72);
+  msg1.add_rc(13);
+  msg2.add_rc(13);
+  msg1.add_rc(17);
+  msg2.add_rc(17);
+  string output;
+  MessageDifferencer differencer;
+  differencer.set_report_matches(true);
+  differencer.ReportDifferencesToString(&output);
+
+  differencer.IgnoreField(msg1.GetDescriptor()->FindFieldByName("c"));
+
+  EXPECT_TRUE(differencer.Compare(msg1, msg2));
+  EXPECT_EQ(
+      "ignored: c\n"
+      "matched: rc[0] : 13\n"
+      "matched: rc[1] : 17\n",
+      output);
+}
+
+TEST_F(MatchingTest, ReportMatchedForMovedFields) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  protobuf_unittest::TestDiffMessage::Item* item = msg1.add_item();
+  item->set_a(53);
+  item->set_b("hello");
+  item = msg2.add_item();
+  item->set_a(27);
+  item = msg2.add_item();
+  item->set_a(53);
+  item->set_b("hello");
+  item = msg1.add_item();
+  item->set_a(27);
+  MessageDifferencer differencer;
+  const FieldDescriptor* desc;
+  desc = msg1.GetDescriptor()->FindFieldByName("item");
+  differencer.TreatAsSet(desc);
+
+  EXPECT_EQ(
+      "matched: item[0].a -> item[1].a : 53\n"
+      "matched: item[0].b -> item[1].b : \"hello\"\n"
+      "moved: item[0] -> item[1] : { a: 53 b: \"hello\" }\n"
+      "matched: item[1].a -> item[0].a : 27\n"
+      "moved: item[1] -> item[0] : { a: 27 }\n",
+      RunWithResult(&differencer, msg1, msg2, true));
+}
+
+TEST_F(MatchingTest, MatchesAppearInPostTraversalOrderForMovedFields) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  protobuf_unittest::TestDiffMessage::Item* item;
+  protobuf_unittest::TestField* field;
+
+  const FieldDescriptor* desc;
+  const FieldDescriptor* nested_desc;
+  const FieldDescriptor* double_nested_desc;
+  desc = msg1.GetDescriptor()->FindFieldByName("item");
+  nested_desc = desc->message_type()->FindFieldByName("rm");
+  double_nested_desc = nested_desc->message_type()->FindFieldByName("rc");
+  MessageDifferencer differencer;
+  differencer.TreatAsSet(desc);
+  differencer.TreatAsSet(nested_desc);
+  differencer.TreatAsSet(double_nested_desc);
+
+  item = msg1.add_item();
+  field = item->add_rm();
+  field->set_c(1);
+  field->add_rc(2);
+  field->add_rc(3);
+  field = item->add_rm();
+  field->set_c(4);
+  field->add_rc(5);
+  field->add_rc(6);
+  field->add_rc(7);
+  item = msg2.add_item();
+  field = item->add_rm();
+  field->set_c(4);
+  field->add_rc(7);
+  field->add_rc(6);
+  field->add_rc(5);
+  field = item->add_rm();
+  field->set_c(1);
+  field->add_rc(3);
+  field->add_rc(2);
+  item = msg1.add_item();
+  field = item->add_rm();
+  field->set_c(8);
+  field->add_rc(10);
+  field->add_rc(11);
+  field->add_rc(9);
+  item = msg2.add_item();
+  field = item->add_rm();
+  field->set_c(8);
+  field->add_rc(9);
+  field->add_rc(10);
+  field->add_rc(11);
+
+  EXPECT_EQ(
+      "matched: item[0].rm[0].c -> item[0].rm[1].c : 1\n"
+      "moved: item[0].rm[0].rc[0] -> item[0].rm[1].rc[1] : 2\n"
+      "moved: item[0].rm[0].rc[1] -> item[0].rm[1].rc[0] : 3\n"
+      "moved: item[0].rm[0] -> item[0].rm[1] : { c: 1 rc: 2 rc: 3 }\n"
+      "matched: item[0].rm[1].c -> item[0].rm[0].c : 4\n"
+      "moved: item[0].rm[1].rc[0] -> item[0].rm[0].rc[2] : 5\n"
+      "matched: item[0].rm[1].rc[1] -> item[0].rm[0].rc[1] : 6\n"
+      "moved: item[0].rm[1].rc[2] -> item[0].rm[0].rc[0] : 7\n"
+      "moved: item[0].rm[1] -> item[0].rm[0] : { c: 4 rc: 5 rc: 6 rc: 7 }\n"
+      "matched: item[0] : { rm { c: 1 rc: 2 rc: 3 }"
+                          " rm { c: 4 rc: 5 rc: 6 rc: 7 } }\n"
+      "matched: item[1].rm[0].c : 8\n"
+      "moved: item[1].rm[0].rc[0] -> item[1].rm[0].rc[1] : 10\n"
+      "moved: item[1].rm[0].rc[1] -> item[1].rm[0].rc[2] : 11\n"
+      "moved: item[1].rm[0].rc[2] -> item[1].rm[0].rc[0] : 9\n"
+      "matched: item[1].rm[0] : { c: 8 rc: 10 rc: 11 rc: 9 }\n"
+      "matched: item[1] : { rm { c: 8 rc: 10 rc: 11 rc: 9 } }\n",
+      RunWithResult(&differencer, msg1, msg2, true));
+}
+
+TEST_F(MatchingTest, MatchAndModifiedInterleaveProperly) {
+  protobuf_unittest::TestDiffMessage msg1, msg2;
+  protobuf_unittest::TestDiffMessage::Item* item;
+  protobuf_unittest::TestField* field;
+
+  const FieldDescriptor* desc;
+  const FieldDescriptor* nested_key;
+  const FieldDescriptor* nested_desc;
+  const FieldDescriptor* double_nested_key;
+  const FieldDescriptor* double_nested_desc;
+  desc = msg1.GetDescriptor()->FindFieldByName("item");
+  nested_key = desc->message_type()->FindFieldByName("a");
+  nested_desc = desc->message_type()->FindFieldByName("rm");
+  double_nested_key = nested_desc->message_type()->FindFieldByName("c");
+  double_nested_desc = nested_desc->message_type()->FindFieldByName("rc");
+
+  MessageDifferencer differencer;
+  differencer.TreatAsMap(desc, nested_key);
+  differencer.TreatAsMap(nested_desc, double_nested_key);
+  differencer.TreatAsSet(double_nested_desc);
+
+  item = msg1.add_item();
+  item->set_a(1);
+  field = item->add_rm();
+  field->set_c(2);
+  field->add_rc(3);
+  field->add_rc(4);
+  field = item->add_rm();
+  field->set_c(5);
+  field->add_rc(6);
+  field->add_rc(7);
+  field->add_rc(8);
+  item = msg1.add_item();
+  item->set_a(9);
+  field = item->add_rm();
+  field->set_c(10);
+  field->add_rc(11);
+  field->add_rc(12);
+  field = item->add_rm();
+  field->set_c(13);
+
+  item = msg2.add_item();
+  item->set_a(1);
+  field = item->add_rm();
+  field->set_c(5);
+  field->add_rc(8);
+  field->add_rc(8);
+  field->add_rc(6);
+  field = item->add_rm();
+  field->set_c(3);
+  field->add_rc(2);
+  field->add_rc(4);
+  item = msg2.add_item();
+  item->set_a(9);
+  field = item->add_rm();
+  field->set_c(10);
+  field->add_rc(12);
+  field->add_rc(11);
+  field = item->add_rm();
+  field->set_c(13);
+
+  EXPECT_EQ(
+      "matched: item[0].a : 1\n"
+      "matched: item[0].rm[1].c -> item[0].rm[0].c : 5\n"
+      "moved: item[0].rm[1].rc[0] -> item[0].rm[0].rc[2] : 6\n"
+      "moved: item[0].rm[1].rc[2] -> item[0].rm[0].rc[0] : 8\n"
+      "added: item[0].rm[0].rc[1]: 8\n"
+      "deleted: item[0].rm[1].rc[1]: 7\n"
+      "modified: item[0].rm[1] -> item[0].rm[0]: { c: 5 rc: 6 rc: 7 rc: 8 } ->"
+                                               " { c: 5 rc: 8 rc: 8 rc: 6 }\n"
+      "added: item[0].rm[1]: { c: 3 rc: 2 rc: 4 }\n"
+      "deleted: item[0].rm[0]: { c: 2 rc: 3 rc: 4 }\n"
+      "modified: item[0]: { a: 1 rm { c: 2 rc: 3 rc: 4 }"
+                               " rm { c: 5 rc: 6 rc: 7 rc: 8 } } ->"
+                        " { a: 1 rm { c: 5 rc: 8 rc: 8 rc: 6 }"
+                               " rm { c: 3 rc: 2 rc: 4 } }\n"
+      "matched: item[1].a : 9\n"
+      "matched: item[1].rm[0].c : 10\n"
+      "moved: item[1].rm[0].rc[0] -> item[1].rm[0].rc[1] : 11\n"
+      "moved: item[1].rm[0].rc[1] -> item[1].rm[0].rc[0] : 12\n"
+      "matched: item[1].rm[0] : { c: 10 rc: 11 rc: 12 }\n"
+      "matched: item[1].rm[1].c : 13\n"
+      "matched: item[1].rm[1] : { c: 13 }\n"
+      "matched: item[1] : { a: 9 rm { c: 10 rc: 11 rc: 12 } rm { c: 13 } }\n",
+      RunWithResult(&differencer, msg1, msg2, false));
+}
+
+TEST_F(MatchingTest, MatchingWorksWithExtensions) {
+  protobuf_unittest::TestAllExtensions msg1, msg2;
+  protobuf_unittest::TestAllTypes::NestedMessage* nested;
+  using protobuf_unittest::repeated_nested_message_extension;
+
+  const FileDescriptor* descriptor;
+  const FieldDescriptor* desc;
+  const FieldDescriptor* nested_key;
+  descriptor = msg1.GetDescriptor()->file();
+  desc = descriptor->FindExtensionByName("repeated_nested_message_extension");
+  ASSERT_FALSE(desc == NULL);
+  nested_key = desc->message_type()->FindFieldByName("bb");
+
+  MessageDifferencer differencer;
+  differencer.TreatAsMap(desc, nested_key);
+
+  nested = msg1.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(7);
+  nested = msg1.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(13);
+  nested = msg1.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(11);
+  nested = msg2.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(11);
+  nested = msg2.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(13);
+  nested = msg2.AddExtension(repeated_nested_message_extension);
+  nested->set_bb(7);
+
+  EXPECT_EQ(
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[0].bb ->"
+              " (protobuf_unittest.repeated_nested_message_extension)[2].bb : 7\n"
+      "moved: (protobuf_unittest.repeated_nested_message_extension)[0] ->"
+            " (protobuf_unittest.repeated_nested_message_extension)[2] :"
+                " { bb: 7 }\n"
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[1].bb :"
+                  " 13\n"
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[1] :"
+                  " { bb: 13 }\n"
+      "matched: (protobuf_unittest.repeated_nested_message_extension)[2].bb ->"
+              " (protobuf_unittest.repeated_nested_message_extension)[0].bb :"
+                  " 11\n"
+      "moved: (protobuf_unittest.repeated_nested_message_extension)[2] ->"
+            " (protobuf_unittest.repeated_nested_message_extension)[0] :"
+                " { bb: 11 }\n",
+      RunWithResult(&differencer, msg1, msg2, true));
+}
+
+TEST(AnyTest, Simple) {
+  protobuf_unittest::TestField value1, value2;
+  value1.set_a(20);
+  value2.set_a(21);
+
+  protobuf_unittest::TestAny m1, m2;
+  m1.mutable_any_value()->PackFrom(value1);
+  m2.mutable_any_value()->PackFrom(value2);
+  util::MessageDifferencer message_differencer;
+  string difference_string;
+  message_differencer.ReportDifferencesToString(&difference_string);
+  EXPECT_FALSE(message_differencer.Compare(m1, m2));
+  EXPECT_EQ("modified: any_value.a: 20 -> 21\n", difference_string);
+}
+
+TEST(Anytest, TreatAsSet) {
+  protobuf_unittest::TestField value1, value2;
+  value1.set_a(20);
+  value1.set_b(30);
+  value2.set_a(20);
+  value2.set_b(31);
+
+  protobuf_unittest::TestAny m1, m2;
+  m1.add_repeated_any_value()->PackFrom(value1);
+  m1.add_repeated_any_value()->PackFrom(value2);
+  m2.add_repeated_any_value()->PackFrom(value2);
+  m2.add_repeated_any_value()->PackFrom(value1);
+
+  util::MessageDifferencer message_differencer;
+  message_differencer.TreatAsSet(GetFieldDescriptor(m1, "repeated_any_value"));
+  EXPECT_TRUE(message_differencer.Compare(m1, m2));
+}
+
+
+}  // namespace
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/message_differencer_unittest.proto b/src/google/protobuf/util/message_differencer_unittest.proto
new file mode 100644
index 0000000..698775f
--- /dev/null
+++ b/src/google/protobuf/util/message_differencer_unittest.proto
@@ -0,0 +1,74 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Author: kenton@google.com (Kenton Varda)
+//  Based on original Protocol Buffers design by
+//  Sanjay Ghemawat, Jeff Dean, and others.
+//
+// This file contains messages for testing repeated field comparison
+
+syntax = "proto2";
+package protobuf_unittest;
+
+option optimize_for = SPEED;
+
+message TestField {
+  optional int32 a = 3;
+  optional int32 b = 4;
+  optional int32 c = 1;
+  repeated int32 rc = 2;
+  optional TestField m = 5;
+
+  extend TestDiffMessage {
+    optional TestField tf = 100;
+  }
+}
+
+message TestDiffMessage {
+  repeated group Item = 1 {
+    optional int32  a  =  2;     // Test basic repeated field comparison.
+    optional string b  =  4;     // Test basic repeated field comparison.
+    repeated int32  ra =  3;     // Test SetOfSet Comparison.
+    repeated string rb =  5;     // Test TreatAsMap when key is repeated
+    optional TestField m  = 6;   // Test TreatAsMap when key is a message
+    repeated TestField rm = 7;   // Test TreatAsMap when key is a repeated
+                                 // message
+  }
+
+  optional int32  v  = 13 [deprecated = true];
+  optional string w  = 14;
+  optional TestField m  = 15;
+  repeated int32  rv = 11;       // Test for combinations
+  repeated string rw = 10;       // Test for combinations
+  repeated TestField rm = 12 [deprecated = true];    // Test for combinations
+
+  extensions 100 to 199;
+}
+
diff --git a/src/google/protobuf/util/time_util.cc b/src/google/protobuf/util/time_util.cc
new file mode 100644
index 0000000..c782d69
--- /dev/null
+++ b/src/google/protobuf/util/time_util.cc
@@ -0,0 +1,525 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/time_util.h>
+
+#include <google/protobuf/stubs/time.h>
+#include <google/protobuf/stubs/int128.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/stringprintf.h>
+#include <google/protobuf/duration.pb.h>
+#include <google/protobuf/timestamp.pb.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+using google::protobuf::Timestamp;
+using google::protobuf::Duration;
+
+namespace {
+static const int kNanosPerSecond = 1000000000;
+static const int kMicrosPerSecond = 1000000;
+static const int kMillisPerSecond = 1000;
+static const int kNanosPerMillisecond = 1000000;
+static const int kMicrosPerMillisecond = 1000;
+static const int kNanosPerMicrosecond = 1000;
+static const int kSecondsPerMinute = 60;  // Note that we ignore leap seconds.
+static const int kSecondsPerHour = 3600;
+static const char kTimestampFormat[] = "%E4Y-%m-%dT%H:%M:%S";
+
+template <typename T>
+T CreateNormalized(int64 seconds, int64 nanos);
+
+template <>
+Timestamp CreateNormalized(int64 seconds, int64 nanos) {
+  // Make sure nanos is in the range.
+  if (nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
+    seconds += nanos / kNanosPerSecond;
+    nanos = nanos % kNanosPerSecond;
+  }
+  // For Timestamp nanos should be in the range [0, 999999999]
+  if (nanos < 0) {
+    seconds -= 1;
+    nanos += kNanosPerSecond;
+  }
+  GOOGLE_DCHECK(seconds >= TimeUtil::kTimestampMinSeconds &&
+         seconds <= TimeUtil::kTimestampMaxSeconds);
+  Timestamp result;
+  result.set_seconds(seconds);
+  result.set_nanos(static_cast<int32>(nanos));
+  return result;
+}
+
+template <>
+Duration CreateNormalized(int64 seconds, int64 nanos) {
+  // Make sure nanos is in the range.
+  if (nanos <= -kNanosPerSecond || nanos >= kNanosPerSecond) {
+    seconds += nanos / kNanosPerSecond;
+    nanos = nanos % kNanosPerSecond;
+  }
+  // nanos should have the same sign as seconds.
+  if (seconds < 0 && nanos > 0) {
+    seconds += 1;
+    nanos -= kNanosPerSecond;
+  } else if (seconds > 0 && nanos < 0) {
+    seconds -= 1;
+    nanos += kNanosPerSecond;
+  }
+  GOOGLE_DCHECK(seconds >= TimeUtil::kDurationMinSeconds &&
+         seconds <= TimeUtil::kDurationMaxSeconds);
+  Duration result;
+  result.set_seconds(seconds);
+  result.set_nanos(static_cast<int32>(nanos));
+  return result;
+}
+
+// Format nanoseconds with either 3, 6, or 9 digits depending on the required
+// precision to represent the exact value.
+string FormatNanos(int32 nanos) {
+  if (nanos % kNanosPerMillisecond == 0) {
+    return StringPrintf("%03d", nanos / kNanosPerMillisecond);
+  } else if (nanos % kNanosPerMicrosecond == 0) {
+    return StringPrintf("%06d", nanos / kNanosPerMicrosecond);
+  } else {
+    return StringPrintf("%09d", nanos);
+  }
+}
+
+string FormatTime(int64 seconds, int32 nanos) {
+  return ::google::protobuf::internal::FormatTime(seconds, nanos);
+}
+
+bool ParseTime(const string& value, int64* seconds, int32* nanos) {
+  return ::google::protobuf::internal::ParseTime(value, seconds, nanos);
+}
+
+void CurrentTime(int64* seconds, int32* nanos) {
+  return ::google::protobuf::internal::GetCurrentTime(seconds, nanos);
+}
+
+// Truncates the remainder part after division.
+int64 RoundTowardZero(int64 value, int64 divider) {
+  int64 result = value / divider;
+  int64 remainder = value % divider;
+  // Before C++11, the sign of the remainder is implementation dependent if
+  // any of the operands is negative. Here we try to enforce C++11's "rounded
+  // toward zero" semantics. For example, for (-5) / 2 an implementation may
+  // give -3 as the result with the remainder being 1. This function ensures
+  // we always return -2 (closer to zero) regardless of the implementation.
+  if (result < 0 && remainder > 0) {
+    return result + 1;
+  } else {
+    return result;
+  }
+}
+}  // namespace
+
+string TimeUtil::ToString(const Timestamp& timestamp) {
+  return FormatTime(timestamp.seconds(), timestamp.nanos());
+}
+
+bool TimeUtil::FromString(const string& value, Timestamp* timestamp) {
+  int64 seconds;
+  int32 nanos;
+  if (!ParseTime(value, &seconds, &nanos)) {
+    return false;
+  }
+  *timestamp = CreateNormalized<Timestamp>(seconds, nanos);
+  return true;
+}
+
+Timestamp TimeUtil::GetCurrentTime() {
+  int64 seconds;
+  int32 nanos;
+  CurrentTime(&seconds, &nanos);
+  return CreateNormalized<Timestamp>(seconds, nanos);
+}
+
+Timestamp TimeUtil::GetEpoch() { return Timestamp(); }
+
+string TimeUtil::ToString(const Duration& duration) {
+  string result;
+  int64 seconds = duration.seconds();
+  int32 nanos = duration.nanos();
+  if (seconds < 0 || nanos < 0) {
+    result += "-";
+    seconds = -seconds;
+    nanos = -nanos;
+  }
+  result += StringPrintf("%" GOOGLE_LL_FORMAT "d", seconds);
+  if (nanos != 0) {
+    result += "." + FormatNanos(nanos);
+  }
+  result += "s";
+  return result;
+}
+
+static int64 Pow(int64 x, int y) {
+  int64 result = 1;
+  for (int i = 0; i < y; ++i) {
+    result *= x;
+  }
+  return result;
+}
+
+bool TimeUtil::FromString(const string& value, Duration* duration) {
+  if (value.length() <= 1 || value[value.length() - 1] != 's') {
+    return false;
+  }
+  bool negative = (value[0] == '-');
+  int sign_length = (negative ? 1 : 0);
+  // Parse the duration value as two integers rather than a float value
+  // to avoid precision loss.
+  string seconds_part, nanos_part;
+  size_t pos = value.find_last_of(".");
+  if (pos == string::npos) {
+    seconds_part = value.substr(sign_length, value.length() - 1 - sign_length);
+    nanos_part = "0";
+  } else {
+    seconds_part = value.substr(sign_length, pos - sign_length);
+    nanos_part = value.substr(pos + 1, value.length() - pos - 2);
+  }
+  char* end;
+  int64 seconds = strto64(seconds_part.c_str(), &end, 10);
+  if (end != seconds_part.c_str() + seconds_part.length()) {
+    return false;
+  }
+  int64 nanos = strto64(nanos_part.c_str(), &end, 10);
+  if (end != nanos_part.c_str() + nanos_part.length()) {
+    return false;
+  }
+  nanos = nanos * Pow(10, 9 - nanos_part.length());
+  if (negative) {
+    // If a Duration is negative, both seconds and nanos should be negative.
+    seconds = -seconds;
+    nanos = -nanos;
+  }
+  duration->set_seconds(seconds);
+  duration->set_nanos(static_cast<int32>(nanos));
+  return true;
+}
+
+Duration TimeUtil::NanosecondsToDuration(int64 nanos) {
+  return CreateNormalized<Duration>(nanos / kNanosPerSecond,
+                                    nanos % kNanosPerSecond);
+}
+
+Duration TimeUtil::MicrosecondsToDuration(int64 micros) {
+  return CreateNormalized<Duration>(
+      micros / kMicrosPerSecond,
+      (micros % kMicrosPerSecond) * kNanosPerMicrosecond);
+}
+
+Duration TimeUtil::MillisecondsToDuration(int64 millis) {
+  return CreateNormalized<Duration>(
+      millis / kMillisPerSecond,
+      (millis % kMillisPerSecond) * kNanosPerMillisecond);
+}
+
+Duration TimeUtil::SecondsToDuration(int64 seconds) {
+  return CreateNormalized<Duration>(seconds, 0);
+}
+
+Duration TimeUtil::MinutesToDuration(int64 minutes) {
+  return CreateNormalized<Duration>(minutes * kSecondsPerMinute, 0);
+}
+
+Duration TimeUtil::HoursToDuration(int64 hours) {
+  return CreateNormalized<Duration>(hours * kSecondsPerHour, 0);
+}
+
+int64 TimeUtil::DurationToNanoseconds(const Duration& duration) {
+  return duration.seconds() * kNanosPerSecond + duration.nanos();
+}
+
+int64 TimeUtil::DurationToMicroseconds(const Duration& duration) {
+  return duration.seconds() * kMicrosPerSecond +
+         RoundTowardZero(duration.nanos(), kNanosPerMicrosecond);
+}
+
+int64 TimeUtil::DurationToMilliseconds(const Duration& duration) {
+  return duration.seconds() * kMillisPerSecond +
+         RoundTowardZero(duration.nanos(), kNanosPerMillisecond);
+}
+
+int64 TimeUtil::DurationToSeconds(const Duration& duration) {
+  return duration.seconds();
+}
+
+int64 TimeUtil::DurationToMinutes(const Duration& duration) {
+  return RoundTowardZero(duration.seconds(), kSecondsPerMinute);
+}
+
+int64 TimeUtil::DurationToHours(const Duration& duration) {
+  return RoundTowardZero(duration.seconds(), kSecondsPerHour);
+}
+
+Timestamp TimeUtil::NanosecondsToTimestamp(int64 nanos) {
+  return CreateNormalized<Timestamp>(nanos / kNanosPerSecond,
+                                     nanos % kNanosPerSecond);
+}
+
+Timestamp TimeUtil::MicrosecondsToTimestamp(int64 micros) {
+  return CreateNormalized<Timestamp>(
+      micros / kMicrosPerSecond,
+      micros % kMicrosPerSecond * kNanosPerMicrosecond);
+}
+
+Timestamp TimeUtil::MillisecondsToTimestamp(int64 millis) {
+  return CreateNormalized<Timestamp>(
+      millis / kMillisPerSecond,
+      millis % kMillisPerSecond * kNanosPerMillisecond);
+}
+
+Timestamp TimeUtil::SecondsToTimestamp(int64 seconds) {
+  return CreateNormalized<Timestamp>(seconds, 0);
+}
+
+int64 TimeUtil::TimestampToNanoseconds(const Timestamp& timestamp) {
+  return timestamp.seconds() * kNanosPerSecond + timestamp.nanos();
+}
+
+int64 TimeUtil::TimestampToMicroseconds(const Timestamp& timestamp) {
+  return timestamp.seconds() * kMicrosPerSecond +
+         RoundTowardZero(timestamp.nanos(), kNanosPerMicrosecond);
+}
+
+int64 TimeUtil::TimestampToMilliseconds(const Timestamp& timestamp) {
+  return timestamp.seconds() * kMillisPerSecond +
+         RoundTowardZero(timestamp.nanos(), kNanosPerMillisecond);
+}
+
+int64 TimeUtil::TimestampToSeconds(const Timestamp& timestamp) {
+  return timestamp.seconds();
+}
+
+Timestamp TimeUtil::TimeTToTimestamp(time_t value) {
+  return CreateNormalized<Timestamp>(static_cast<int64>(value), 0);
+}
+
+time_t TimeUtil::TimestampToTimeT(const Timestamp& value) {
+  return static_cast<time_t>(value.seconds());
+}
+
+Timestamp TimeUtil::TimevalToTimestamp(const timeval& value) {
+  return CreateNormalized<Timestamp>(value.tv_sec,
+                                     value.tv_usec * kNanosPerMicrosecond);
+}
+
+timeval TimeUtil::TimestampToTimeval(const Timestamp& value) {
+  timeval result;
+  result.tv_sec = value.seconds();
+  result.tv_usec = RoundTowardZero(value.nanos(), kNanosPerMicrosecond);
+  return result;
+}
+
+Duration TimeUtil::TimevalToDuration(const timeval& value) {
+  return CreateNormalized<Duration>(value.tv_sec,
+                                    value.tv_usec * kNanosPerMicrosecond);
+}
+
+timeval TimeUtil::DurationToTimeval(const Duration& value) {
+  timeval result;
+  result.tv_sec = value.seconds();
+  result.tv_usec = RoundTowardZero(value.nanos(), kNanosPerMicrosecond);
+  // timeval.tv_usec's range is [0, 1000000)
+  if (result.tv_usec < 0) {
+    result.tv_sec -= 1;
+    result.tv_usec += kMicrosPerSecond;
+  }
+  return result;
+}
+
+}  // namespace util
+}  // namespace protobuf
+
+
+namespace protobuf {
+namespace {
+using google::protobuf::util::kNanosPerSecond;
+using google::protobuf::util::CreateNormalized;
+
+// Convert a Timestamp to uint128.
+void ToUint128(const Timestamp& value, uint128* result, bool* negative) {
+  if (value.seconds() < 0) {
+    *negative = true;
+    *result = static_cast<uint64>(-value.seconds());
+    *result = *result * kNanosPerSecond - static_cast<uint32>(value.nanos());
+  } else {
+    *negative = false;
+    *result = static_cast<uint64>(value.seconds());
+    *result = *result * kNanosPerSecond + static_cast<uint32>(value.nanos());
+  }
+}
+
+// Convert a Duration to uint128.
+void ToUint128(const Duration& value, uint128* result, bool* negative) {
+  if (value.seconds() < 0 || value.nanos() < 0) {
+    *negative = true;
+    *result = static_cast<uint64>(-value.seconds());
+    *result = *result * kNanosPerSecond + static_cast<uint32>(-value.nanos());
+  } else {
+    *negative = false;
+    *result = static_cast<uint64>(value.seconds());
+    *result = *result * kNanosPerSecond + static_cast<uint32>(value.nanos());
+  }
+}
+
+void ToTimestamp(const uint128& value, bool negative, Timestamp* timestamp) {
+  int64 seconds = static_cast<int64>(Uint128Low64(value / kNanosPerSecond));
+  int32 nanos = static_cast<int32>(Uint128Low64(value % kNanosPerSecond));
+  if (negative) {
+    seconds = -seconds;
+    nanos = -nanos;
+    if (nanos < 0) {
+      nanos += kNanosPerSecond;
+      seconds -= 1;
+    }
+  }
+  timestamp->set_seconds(seconds);
+  timestamp->set_nanos(nanos);
+}
+
+void ToDuration(const uint128& value, bool negative, Duration* duration) {
+  int64 seconds = static_cast<int64>(Uint128Low64(value / kNanosPerSecond));
+  int32 nanos = static_cast<int32>(Uint128Low64(value % kNanosPerSecond));
+  if (negative) {
+    seconds = -seconds;
+    nanos = -nanos;
+  }
+  duration->set_seconds(seconds);
+  duration->set_nanos(nanos);
+}
+}  // namespace
+
+Duration& operator+=(Duration& d1, const Duration& d2) {
+  d1 = CreateNormalized<Duration>(d1.seconds() + d2.seconds(),
+                                  d1.nanos() + d2.nanos());
+  return d1;
+}
+
+Duration& operator-=(Duration& d1, const Duration& d2) {  // NOLINT
+  d1 = CreateNormalized<Duration>(d1.seconds() - d2.seconds(),
+                                  d1.nanos() - d2.nanos());
+  return d1;
+}
+
+Duration& operator*=(Duration& d, int64 r) {  // NOLINT
+  bool negative;
+  uint128 value;
+  ToUint128(d, &value, &negative);
+  if (r > 0) {
+    value *= static_cast<uint64>(r);
+  } else {
+    negative = !negative;
+    value *= static_cast<uint64>(-r);
+  }
+  ToDuration(value, negative, &d);
+  return d;
+}
+
+Duration& operator*=(Duration& d, double r) {  // NOLINT
+  double result = (d.seconds() * 1.0 + 1.0 * d.nanos() / kNanosPerSecond) * r;
+  int64 seconds = static_cast<int64>(result);
+  int32 nanos = static_cast<int32>((result - seconds) * kNanosPerSecond);
+  // Note that we normalize here not just because nanos can have a different
+  // sign from seconds but also that nanos can be any arbitrary value when
+  // overflow happens (i.e., the result is a much larger value than what
+  // int64 can represent).
+  d = CreateNormalized<Duration>(seconds, nanos);
+  return d;
+}
+
+Duration& operator/=(Duration& d, int64 r) {  // NOLINT
+  bool negative;
+  uint128 value;
+  ToUint128(d, &value, &negative);
+  if (r > 0) {
+    value /= static_cast<uint64>(r);
+  } else {
+    negative = !negative;
+    value /= static_cast<uint64>(-r);
+  }
+  ToDuration(value, negative, &d);
+  return d;
+}
+
+Duration& operator/=(Duration& d, double r) {  // NOLINT
+  return d *= 1.0 / r;
+}
+
+Duration& operator%=(Duration& d1, const Duration& d2) {  // NOLINT
+  bool negative1, negative2;
+  uint128 value1, value2;
+  ToUint128(d1, &value1, &negative1);
+  ToUint128(d2, &value2, &negative2);
+  uint128 result = value1 % value2;
+  // When negative values are involved in division, we round the division
+  // result towards zero. With this semantics, sign of the remainder is the
+  // same as the dividend. For example:
+  //     -5 / 10    = 0, -5 % 10    = -5
+  //     -5 / (-10) = 0, -5 % (-10) = -5
+  //      5 / (-10) = 0,  5 % (-10) = 5
+  ToDuration(result, negative1, &d1);
+  return d1;
+}
+
+int64 operator/(const Duration& d1, const Duration& d2) {
+  bool negative1, negative2;
+  uint128 value1, value2;
+  ToUint128(d1, &value1, &negative1);
+  ToUint128(d2, &value2, &negative2);
+  int64 result = Uint128Low64(value1 / value2);
+  if (negative1 != negative2) {
+    result = -result;
+  }
+  return result;
+}
+
+Timestamp& operator+=(Timestamp& t, const Duration& d) {  // NOLINT
+  t = CreateNormalized<Timestamp>(t.seconds() + d.seconds(),
+                                  t.nanos() + d.nanos());
+  return t;
+}
+
+Timestamp& operator-=(Timestamp& t, const Duration& d) {  // NOLINT
+  t = CreateNormalized<Timestamp>(t.seconds() - d.seconds(),
+                                  t.nanos() - d.nanos());
+  return t;
+}
+
+Duration operator-(const Timestamp& t1, const Timestamp& t2) {
+  return CreateNormalized<Duration>(t1.seconds() - t2.seconds(),
+                                    t1.nanos() - t2.nanos());
+}
+}  // namespace protobuf
+
+}  // namespace google
diff --git a/src/google/protobuf/util/time_util.h b/src/google/protobuf/util/time_util.h
new file mode 100644
index 0000000..1bac089
--- /dev/null
+++ b/src/google/protobuf/util/time_util.h
@@ -0,0 +1,293 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_TIME_UTIL_H__
+#define GOOGLE_PROTOBUF_UTIL_TIME_UTIL_H__
+
+#include <ctime>
+#include <ostream>
+#include <string>
+#ifdef _MSC_VER
+#include <winsock2.h>
+#else
+#include <sys/time.h>
+#endif
+
+#include <google/protobuf/duration.pb.h>
+#include <google/protobuf/timestamp.pb.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+class LIBPROTOBUF_EXPORT TimeUtil {
+  typedef google::protobuf::Timestamp Timestamp;
+  typedef google::protobuf::Duration Duration;
+
+ public:
+  // The min/max Timestamp/Duration values we support.
+  //
+  // For "0001-01-01T00:00:00Z".
+  static const int64 kTimestampMinSeconds = -62135596800LL;
+  // For "9999-12-31T23:59:59.999999999Z".
+  static const int64 kTimestampMaxSeconds = 253402300799LL;
+  static const int64 kDurationMinSeconds = -315576000000LL;
+  static const int64 kDurationMaxSeconds = 315576000000LL;
+
+  // Converts Timestamp to/from RFC 3339 date string format.
+  // Generated output will always be Z-normalized and uses 3, 6 or 9
+  // fractional digits as required to represent the exact time. When
+  // parsing, any fractional digits (or none) and any offset are
+  // accepted as long as they fit into nano-seconds precision.
+  // Note that Timestamp can only represent time from
+  // 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. Converting
+  // a Timestamp outside of this range is undefined behavior.
+  // See https://www.ietf.org/rfc/rfc3339.txt
+  //
+  // Example of generated format:
+  //   "1972-01-01T10:00:20.021Z"
+  //
+  // Example of accepted format:
+  //   "1972-01-01T10:00:20.021-05:00"
+  static string ToString(const Timestamp& timestamp);
+  static bool FromString(const string& value, Timestamp* timestamp);
+
+  // Converts Duration to/from string format. The string format will contains
+  // 3, 6, or 9 fractional digits depending on the precision required to
+  // represent the exact Duration value. For example:
+  //   "1s", "1.010s", "1.000000100s", "-3.100s"
+  // The range that can be represented by Duration is from -315,576,000,000
+  // to +315,576,000,000 inclusive (in seconds).
+  static string ToString(const Duration& duration);
+  static bool FromString(const string& value, Duration* timestamp);
+
+#ifdef GetCurrentTime
+#undef GetCurrentTime  // Visual Studio has macro GetCurrentTime
+#endif
+  // Gets the current UTC time.
+  static Timestamp GetCurrentTime();
+  // Returns the Time representing "1970-01-01 00:00:00".
+  static Timestamp GetEpoch();
+
+  // Converts between Duration and integer types. The behavior is undefined if
+  // the input value is not in the valid range of Duration.
+  static Duration NanosecondsToDuration(int64 nanos);
+  static Duration MicrosecondsToDuration(int64 micros);
+  static Duration MillisecondsToDuration(int64 millis);
+  static Duration SecondsToDuration(int64 seconds);
+  static Duration MinutesToDuration(int64 minutes);
+  static Duration HoursToDuration(int64 hours);
+  // Result will be truncated towards zero. For example, "-1.5s" will be
+  // truncated to "-1s", and "1.5s" to "1s" when converting to seconds.
+  // It's undefined behavior if the input duration is not valid or the result
+  // exceeds the range of int64. A duration is not valid if it's not in the
+  // valid range of Duration, or have an invalid nanos value (i.e., larger
+  // than 999999999, less than -999999999, or have a different sign from the
+  // seconds part).
+  static int64 DurationToNanoseconds(const Duration& duration);
+  static int64 DurationToMicroseconds(const Duration& duration);
+  static int64 DurationToMilliseconds(const Duration& duration);
+  static int64 DurationToSeconds(const Duration& duration);
+  static int64 DurationToMinutes(const Duration& duration);
+  static int64 DurationToHours(const Duration& duration);
+  // Creates Timestamp from integer types. The integer value indicates the
+  // time elapsed from Epoch time. The behavior is undefined if the input
+  // value is not in the valid range of Timestamp.
+  static Timestamp NanosecondsToTimestamp(int64 nanos);
+  static Timestamp MicrosecondsToTimestamp(int64 micros);
+  static Timestamp MillisecondsToTimestamp(int64 millis);
+  static Timestamp SecondsToTimestamp(int64 seconds);
+  // Result will be truncated down to the nearest integer value. For example,
+  // with "1969-12-31T23:59:59.9Z", TimestampToMilliseconds() returns -100
+  // and TimestampToSeconds() returns -1. It's undefined behavior if the input
+  // Timestamp is not valid (i.e., its seconds part or nanos part does not fall
+  // in the valid range) or the return value doesn't fit into int64.
+  static int64 TimestampToNanoseconds(const Timestamp& timestamp);
+  static int64 TimestampToMicroseconds(const Timestamp& timestamp);
+  static int64 TimestampToMilliseconds(const Timestamp& timestamp);
+  static int64 TimestampToSeconds(const Timestamp& timestamp);
+
+  // Conversion to/from other time/date types. Note that these types may
+  // have a different precision and time range from Timestamp/Duration.
+  // When converting to a lower precision type, the value will be truncated
+  // to the nearest value that can be represented. If the value is
+  // out of the range of the result type, the return value is undefined.
+  //
+  // Conversion to/from time_t
+  static Timestamp TimeTToTimestamp(time_t value);
+  static time_t TimestampToTimeT(const Timestamp& value);
+
+  // Conversion to/from timeval
+  static Timestamp TimevalToTimestamp(const timeval& value);
+  static timeval TimestampToTimeval(const Timestamp& value);
+  static Duration TimevalToDuration(const timeval& value);
+  static timeval DurationToTimeval(const Duration& value);
+};
+
+}  // namespace util
+}  // namespace protobuf
+
+
+namespace protobuf {
+// Overloaded operators for Duration.
+//
+// Assignment operators.
+LIBPROTOBUF_EXPORT Duration& operator+=(Duration& d1, const Duration& d2);  // NOLINT
+LIBPROTOBUF_EXPORT Duration& operator-=(Duration& d1, const Duration& d2);  // NOLINT
+LIBPROTOBUF_EXPORT Duration& operator*=(Duration& d, int64 r);  // NOLINT
+LIBPROTOBUF_EXPORT Duration& operator*=(Duration& d, double r);  // NOLINT
+LIBPROTOBUF_EXPORT Duration& operator/=(Duration& d, int64 r);  // NOLINT
+LIBPROTOBUF_EXPORT Duration& operator/=(Duration& d, double r);  // NOLINT
+// Overload for other integer types.
+template <typename T>
+Duration& operator*=(Duration& d, T r) {  // NOLINT
+  int64 x = r;
+  return d *= x;
+}
+template <typename T>
+Duration& operator/=(Duration& d, T r) {  // NOLINT
+  int64 x = r;
+  return d /= x;
+}
+LIBPROTOBUF_EXPORT Duration& operator%=(Duration& d1, const Duration& d2);  // NOLINT
+// Relational operators.
+inline bool operator<(const Duration& d1, const Duration& d2) {
+  if (d1.seconds() == d2.seconds()) {
+    return d1.nanos() < d2.nanos();
+  }
+  return d1.seconds() < d2.seconds();
+}
+inline bool operator>(const Duration& d1, const Duration& d2) {
+  return d2 < d1;
+}
+inline bool operator>=(const Duration& d1, const Duration& d2) {
+  return !(d1 < d2);
+}
+inline bool operator<=(const Duration& d1, const Duration& d2) {
+  return !(d2 < d1);
+}
+inline bool operator==(const Duration& d1, const Duration& d2) {
+  return d1.seconds() == d2.seconds() && d1.nanos() == d2.nanos();
+}
+inline bool operator!=(const Duration& d1, const Duration& d2) {
+  return !(d1 == d2);
+}
+// Additive operators
+inline Duration operator-(const Duration& d) {
+  Duration result;
+  result.set_seconds(-d.seconds());
+  result.set_nanos(-d.nanos());
+  return result;
+}
+inline Duration operator+(const Duration& d1, const Duration& d2) {
+  Duration result = d1;
+  return result += d2;
+}
+inline Duration operator-(const Duration& d1, const Duration& d2) {
+  Duration result = d1;
+  return result -= d2;
+}
+// Multiplicative operators
+template<typename T>
+inline Duration operator*(Duration d, T r) {
+  return d *= r;
+}
+template<typename T>
+inline Duration operator*(T r, Duration d) {
+  return d *= r;
+}
+template<typename T>
+inline Duration operator/(Duration d, T r) {
+  return d /= r;
+}
+LIBPROTOBUF_EXPORT int64 operator/(const Duration& d1, const Duration& d2);
+
+inline Duration operator%(const Duration& d1, const Duration& d2) {
+  Duration result = d1;
+  return result %= d2;
+}
+
+inline ostream& operator<<(ostream& out, const Duration& d) {
+  out << google::protobuf::util::TimeUtil::ToString(d);
+  return out;
+}
+
+// Overloaded operators for Timestamp
+//
+// Assignement operators.
+LIBPROTOBUF_EXPORT Timestamp& operator+=(Timestamp& t, const Duration& d);  // NOLINT
+LIBPROTOBUF_EXPORT Timestamp& operator-=(Timestamp& t, const Duration& d);  // NOLINT
+// Relational operators.
+inline bool operator<(const Timestamp& t1, const Timestamp& t2) {
+  if (t1.seconds() == t2.seconds()) {
+    return t1.nanos() < t2.nanos();
+  }
+  return t1.seconds() < t2.seconds();
+}
+inline bool operator>(const Timestamp& t1, const Timestamp& t2) {
+  return t2 < t1;
+}
+inline bool operator>=(const Timestamp& t1, const Timestamp& t2) {
+  return !(t1 < t2);
+}
+inline bool operator<=(const Timestamp& t1, const Timestamp& t2) {
+  return !(t2 < t1);
+}
+inline bool operator==(const Timestamp& t1, const Timestamp& t2) {
+  return t1.seconds() == t2.seconds() && t1.nanos() == t2.nanos();
+}
+inline bool operator!=(const Timestamp& t1, const Timestamp& t2) {
+  return !(t1 == t2);
+}
+// Additive operators.
+inline Timestamp operator+(const Timestamp& t, const Duration& d) {
+  Timestamp result = t;
+  return result += d;
+}
+inline Timestamp operator+(const Duration& d, const Timestamp& t) {
+  Timestamp result = t;
+  return result += d;
+}
+inline Timestamp operator-(const Timestamp& t, const Duration& d) {
+  Timestamp result = t;
+  return result -= d;
+}
+LIBPROTOBUF_EXPORT Duration operator-(const Timestamp& t1, const Timestamp& t2);
+
+inline ostream& operator<<(ostream& out, const Timestamp& t) {
+  out << google::protobuf::util::TimeUtil::ToString(t);
+  return out;
+}
+
+}  // namespace protobuf
+
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_TIME_UTIL_H__
diff --git a/src/google/protobuf/util/time_util_test.cc b/src/google/protobuf/util/time_util_test.cc
new file mode 100644
index 0000000..285740a
--- /dev/null
+++ b/src/google/protobuf/util/time_util_test.cc
@@ -0,0 +1,380 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/time_util.h>
+
+#include <ctime>
+
+#include <google/protobuf/timestamp.pb.h>
+#include <google/protobuf/duration.pb.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+
+using google::protobuf::Timestamp;
+using google::protobuf::Duration;
+
+namespace {
+
+TEST(TimeUtilTest, TimestampStringFormat) {
+  Timestamp begin, end;
+  EXPECT_TRUE(TimeUtil::FromString("0001-01-01T00:00:00Z", &begin));
+  EXPECT_EQ(TimeUtil::kTimestampMinSeconds, begin.seconds());
+  EXPECT_EQ(0, begin.nanos());
+  EXPECT_TRUE(TimeUtil::FromString("9999-12-31T23:59:59.999999999Z", &end));
+  EXPECT_EQ(TimeUtil::kTimestampMaxSeconds, end.seconds());
+  EXPECT_EQ(999999999, end.nanos());
+  EXPECT_EQ("0001-01-01T00:00:00Z", TimeUtil::ToString(begin));
+  EXPECT_EQ("9999-12-31T23:59:59.999999999Z", TimeUtil::ToString(end));
+
+  // Test negative timestamps.
+  Timestamp time = TimeUtil::NanosecondsToTimestamp(-1);
+  EXPECT_EQ(-1, time.seconds());
+  // Timestamp's nano part is always non-negative.
+  EXPECT_EQ(999999999, time.nanos());
+  EXPECT_EQ("1969-12-31T23:59:59.999999999Z", TimeUtil::ToString(time));
+
+  // Generated output should contain 3, 6, or 9 fractional digits.
+  EXPECT_EQ("1970-01-01T00:00:00Z",
+            TimeUtil::ToString(TimeUtil::NanosecondsToTimestamp(0)));
+  EXPECT_EQ("1970-01-01T00:00:00.010Z",
+            TimeUtil::ToString(TimeUtil::NanosecondsToTimestamp(10000000)));
+  EXPECT_EQ("1970-01-01T00:00:00.000010Z",
+            TimeUtil::ToString(TimeUtil::NanosecondsToTimestamp(10000)));
+  EXPECT_EQ("1970-01-01T00:00:00.000000010Z",
+            TimeUtil::ToString(TimeUtil::NanosecondsToTimestamp(10)));
+
+  // Parsing accepts an fractional digits as long as they fit into nano
+  // precision.
+  EXPECT_TRUE(TimeUtil::FromString("1970-01-01T00:00:00.1Z", &time));
+  EXPECT_EQ(100000000, TimeUtil::TimestampToNanoseconds(time));
+  EXPECT_TRUE(TimeUtil::FromString("1970-01-01T00:00:00.0001Z", &time));
+  EXPECT_EQ(100000, TimeUtil::TimestampToNanoseconds(time));
+  EXPECT_TRUE(TimeUtil::FromString("1970-01-01T00:00:00.0000001Z", &time));
+  EXPECT_EQ(100, TimeUtil::TimestampToNanoseconds(time));
+
+  // Also accpets offsets.
+  EXPECT_TRUE(TimeUtil::FromString("1970-01-01T00:00:00-08:00", &time));
+  EXPECT_EQ(8 * 3600, TimeUtil::TimestampToSeconds(time));
+}
+
+TEST(TimeUtilTest, DurationStringFormat) {
+  Timestamp begin, end;
+  EXPECT_TRUE(TimeUtil::FromString("0001-01-01T00:00:00Z", &begin));
+  EXPECT_TRUE(TimeUtil::FromString("9999-12-31T23:59:59.999999999Z", &end));
+
+  EXPECT_EQ("315537897599.999999999s", TimeUtil::ToString(end - begin));
+  EXPECT_EQ(999999999, (end - begin).nanos());
+  EXPECT_EQ("-315537897599.999999999s", TimeUtil::ToString(begin - end));
+  EXPECT_EQ(-999999999, (begin - end).nanos());
+
+  // Generated output should contain 3, 6, or 9 fractional digits.
+  EXPECT_EQ("1s", TimeUtil::ToString(TimeUtil::SecondsToDuration(1)));
+  EXPECT_EQ("0.010s", TimeUtil::ToString(TimeUtil::MillisecondsToDuration(10)));
+  EXPECT_EQ("0.000010s",
+            TimeUtil::ToString(TimeUtil::MicrosecondsToDuration(10)));
+  EXPECT_EQ("0.000000010s",
+            TimeUtil::ToString(TimeUtil::NanosecondsToDuration(10)));
+
+  // Parsing accepts an fractional digits as long as they fit into nano
+  // precision.
+  Duration d;
+  EXPECT_TRUE(TimeUtil::FromString("0.1s", &d));
+  EXPECT_EQ(100, TimeUtil::DurationToMilliseconds(d));
+  EXPECT_TRUE(TimeUtil::FromString("0.0001s", &d));
+  EXPECT_EQ(100, TimeUtil::DurationToMicroseconds(d));
+  EXPECT_TRUE(TimeUtil::FromString("0.0000001s", &d));
+  EXPECT_EQ(100, TimeUtil::DurationToNanoseconds(d));
+
+  // Duration must support range from -315,576,000,000s to +315576000000s
+  // which includes negative values.
+  EXPECT_TRUE(TimeUtil::FromString("315576000000.999999999s", &d));
+  EXPECT_EQ(315576000000LL, d.seconds());
+  EXPECT_EQ(999999999, d.nanos());
+  EXPECT_TRUE(TimeUtil::FromString("-315576000000.999999999s", &d));
+  EXPECT_EQ(-315576000000LL, d.seconds());
+  EXPECT_EQ(-999999999, d.nanos());
+}
+
+TEST(TimeUtilTest, GetEpoch) {
+  EXPECT_EQ(0, TimeUtil::TimestampToNanoseconds(TimeUtil::GetEpoch()));
+}
+
+TEST(TimeUtilTest, DurationIntegerConversion) {
+  EXPECT_EQ("0.000000001s",
+            TimeUtil::ToString(TimeUtil::NanosecondsToDuration(1)));
+  EXPECT_EQ("-0.000000001s",
+            TimeUtil::ToString(TimeUtil::NanosecondsToDuration(-1)));
+  EXPECT_EQ("0.000001s",
+            TimeUtil::ToString(TimeUtil::MicrosecondsToDuration(1)));
+  EXPECT_EQ("-0.000001s",
+            TimeUtil::ToString(TimeUtil::MicrosecondsToDuration(-1)));
+  EXPECT_EQ("0.001s", TimeUtil::ToString(TimeUtil::MillisecondsToDuration(1)));
+  EXPECT_EQ("-0.001s",
+            TimeUtil::ToString(TimeUtil::MillisecondsToDuration(-1)));
+  EXPECT_EQ("1s", TimeUtil::ToString(TimeUtil::SecondsToDuration(1)));
+  EXPECT_EQ("-1s", TimeUtil::ToString(TimeUtil::SecondsToDuration(-1)));
+  EXPECT_EQ("60s", TimeUtil::ToString(TimeUtil::MinutesToDuration(1)));
+  EXPECT_EQ("-60s", TimeUtil::ToString(TimeUtil::MinutesToDuration(-1)));
+  EXPECT_EQ("3600s", TimeUtil::ToString(TimeUtil::HoursToDuration(1)));
+  EXPECT_EQ("-3600s", TimeUtil::ToString(TimeUtil::HoursToDuration(-1)));
+
+  EXPECT_EQ(
+      1, TimeUtil::DurationToNanoseconds(TimeUtil::NanosecondsToDuration(1)));
+  EXPECT_EQ(
+      -1, TimeUtil::DurationToNanoseconds(TimeUtil::NanosecondsToDuration(-1)));
+  EXPECT_EQ(
+      1, TimeUtil::DurationToMicroseconds(TimeUtil::MicrosecondsToDuration(1)));
+  EXPECT_EQ(-1, TimeUtil::DurationToMicroseconds(
+                    TimeUtil::MicrosecondsToDuration(-1)));
+  EXPECT_EQ(
+      1, TimeUtil::DurationToMilliseconds(TimeUtil::MillisecondsToDuration(1)));
+  EXPECT_EQ(-1, TimeUtil::DurationToMilliseconds(
+                    TimeUtil::MillisecondsToDuration(-1)));
+  EXPECT_EQ(1, TimeUtil::DurationToSeconds(TimeUtil::SecondsToDuration(1)));
+  EXPECT_EQ(-1, TimeUtil::DurationToSeconds(TimeUtil::SecondsToDuration(-1)));
+  EXPECT_EQ(1, TimeUtil::DurationToMinutes(TimeUtil::MinutesToDuration(1)));
+  EXPECT_EQ(-1, TimeUtil::DurationToMinutes(TimeUtil::MinutesToDuration(-1)));
+  EXPECT_EQ(1, TimeUtil::DurationToHours(TimeUtil::HoursToDuration(1)));
+  EXPECT_EQ(-1, TimeUtil::DurationToHours(TimeUtil::HoursToDuration(-1)));
+
+  // Test truncation behavior.
+  EXPECT_EQ(1, TimeUtil::DurationToMicroseconds(
+                   TimeUtil::NanosecondsToDuration(1999)));
+  // For negative values, Duration will be rounded towards 0.
+  EXPECT_EQ(-1, TimeUtil::DurationToMicroseconds(
+                    TimeUtil::NanosecondsToDuration(-1999)));
+}
+
+TEST(TestUtilTest, TimestampIntegerConversion) {
+  EXPECT_EQ("1970-01-01T00:00:00.000000001Z",
+            TimeUtil::ToString(TimeUtil::NanosecondsToTimestamp(1)));
+  EXPECT_EQ("1969-12-31T23:59:59.999999999Z",
+            TimeUtil::ToString(TimeUtil::NanosecondsToTimestamp(-1)));
+  EXPECT_EQ("1970-01-01T00:00:00.000001Z",
+            TimeUtil::ToString(TimeUtil::MicrosecondsToTimestamp(1)));
+  EXPECT_EQ("1969-12-31T23:59:59.999999Z",
+            TimeUtil::ToString(TimeUtil::MicrosecondsToTimestamp(-1)));
+  EXPECT_EQ("1970-01-01T00:00:00.001Z",
+            TimeUtil::ToString(TimeUtil::MillisecondsToTimestamp(1)));
+  EXPECT_EQ("1969-12-31T23:59:59.999Z",
+            TimeUtil::ToString(TimeUtil::MillisecondsToTimestamp(-1)));
+  EXPECT_EQ("1970-01-01T00:00:01Z",
+            TimeUtil::ToString(TimeUtil::SecondsToTimestamp(1)));
+  EXPECT_EQ("1969-12-31T23:59:59Z",
+            TimeUtil::ToString(TimeUtil::SecondsToTimestamp(-1)));
+
+  EXPECT_EQ(
+      1, TimeUtil::TimestampToNanoseconds(TimeUtil::NanosecondsToTimestamp(1)));
+  EXPECT_EQ(-1, TimeUtil::TimestampToNanoseconds(
+                    TimeUtil::NanosecondsToTimestamp(-1)));
+  EXPECT_EQ(1, TimeUtil::TimestampToMicroseconds(
+                   TimeUtil::MicrosecondsToTimestamp(1)));
+  EXPECT_EQ(-1, TimeUtil::TimestampToMicroseconds(
+                    TimeUtil::MicrosecondsToTimestamp(-1)));
+  EXPECT_EQ(1, TimeUtil::TimestampToMilliseconds(
+                   TimeUtil::MillisecondsToTimestamp(1)));
+  EXPECT_EQ(-1, TimeUtil::TimestampToMilliseconds(
+                    TimeUtil::MillisecondsToTimestamp(-1)));
+  EXPECT_EQ(1, TimeUtil::TimestampToSeconds(TimeUtil::SecondsToTimestamp(1)));
+  EXPECT_EQ(-1, TimeUtil::TimestampToSeconds(TimeUtil::SecondsToTimestamp(-1)));
+
+  // Test truncation behavior.
+  EXPECT_EQ(1, TimeUtil::TimestampToMicroseconds(
+                   TimeUtil::NanosecondsToTimestamp(1999)));
+  // For negative values, Timestamp will be rounded down.
+  // For example, "1969-12-31T23:59:59.5Z" (i.e., -0.5s) rounded to seconds
+  // will be "1969-12-31T23:59:59Z" (i.e., -1s) rather than
+  // "1970-01-01T00:00:00Z" (i.e., 0s).
+  EXPECT_EQ(-2, TimeUtil::TimestampToMicroseconds(
+                    TimeUtil::NanosecondsToTimestamp(-1999)));
+}
+
+TEST(TimeUtilTest, TimeTConversion) {
+  time_t value = time(NULL);
+  EXPECT_EQ(value,
+            TimeUtil::TimestampToTimeT(TimeUtil::TimeTToTimestamp(value)));
+  EXPECT_EQ(
+      1, TimeUtil::TimestampToTimeT(TimeUtil::MillisecondsToTimestamp(1999)));
+}
+
+TEST(TimeUtilTest, TimevalConversion) {
+  timeval value = TimeUtil::TimestampToTimeval(
+      TimeUtil::NanosecondsToTimestamp(1999999999));
+  EXPECT_EQ(1, value.tv_sec);
+  EXPECT_EQ(999999, value.tv_usec);
+  value = TimeUtil::TimestampToTimeval(
+      TimeUtil::NanosecondsToTimestamp(-1999999999));
+  EXPECT_EQ(-2, value.tv_sec);
+  EXPECT_EQ(0, value.tv_usec);
+
+  value =
+      TimeUtil::DurationToTimeval(TimeUtil::NanosecondsToDuration(1999999999));
+  EXPECT_EQ(1, value.tv_sec);
+  EXPECT_EQ(999999, value.tv_usec);
+  value =
+      TimeUtil::DurationToTimeval(TimeUtil::NanosecondsToDuration(-1999999999));
+  EXPECT_EQ(-2, value.tv_sec);
+  EXPECT_EQ(1, value.tv_usec);
+}
+
+TEST(TimeUtilTest, DurationOperators) {
+  Duration one_second = TimeUtil::SecondsToDuration(1);
+  Duration one_nano = TimeUtil::NanosecondsToDuration(1);
+
+  // Test +/-
+  Duration a = one_second;
+  a += one_second;
+  a -= one_nano;
+  EXPECT_EQ("1.999999999s", TimeUtil::ToString(a));
+  Duration b = -a;
+  EXPECT_EQ("-1.999999999s", TimeUtil::ToString(b));
+  EXPECT_EQ("3.999999998s", TimeUtil::ToString(a + a));
+  EXPECT_EQ("0s", TimeUtil::ToString(a + b));
+  EXPECT_EQ("0s", TimeUtil::ToString(b + a));
+  EXPECT_EQ("-3.999999998s", TimeUtil::ToString(b + b));
+  EXPECT_EQ("3.999999998s", TimeUtil::ToString(a - b));
+  EXPECT_EQ("0s", TimeUtil::ToString(a - a));
+  EXPECT_EQ("0s", TimeUtil::ToString(b - b));
+  EXPECT_EQ("-3.999999998s", TimeUtil::ToString(b - a));
+
+  // Test *
+  EXPECT_EQ(a + a, a * 2);
+  EXPECT_EQ(b + b, a * (-2));
+  EXPECT_EQ(b + b, b * 2);
+  EXPECT_EQ(a + a, b * (-2));
+  EXPECT_EQ("0.999999999s", TimeUtil::ToString(a * 0.5));
+  EXPECT_EQ("-0.999999999s", TimeUtil::ToString(b * 0.5));
+  // Multiplication should not overflow if the result fits into the supported
+  // range of Duration (intermediate result may be larger than int64).
+  EXPECT_EQ("315575999684.424s",
+            TimeUtil::ToString((one_second - one_nano) * 315576000000LL));
+  EXPECT_EQ("-315575999684.424s",
+            TimeUtil::ToString((one_nano - one_second) * 315576000000LL));
+  EXPECT_EQ("-315575999684.424s",
+            TimeUtil::ToString((one_second - one_nano) * (-315576000000LL)));
+
+  // Test / and %
+  EXPECT_EQ("0.999999999s", TimeUtil::ToString(a / 2));
+  EXPECT_EQ("-0.999999999s", TimeUtil::ToString(b / 2));
+  Duration large = TimeUtil::SecondsToDuration(315576000000LL) - one_nano;
+  // We have to handle division with values beyond 64 bits.
+  EXPECT_EQ("0.999999999s", TimeUtil::ToString(large / 315576000000LL));
+  EXPECT_EQ("-0.999999999s", TimeUtil::ToString((-large) / 315576000000LL));
+  EXPECT_EQ("-0.999999999s", TimeUtil::ToString(large / (-315576000000LL)));
+  Duration large2 = large + one_nano;
+  EXPECT_EQ(large, large % large2);
+  EXPECT_EQ(-large, (-large) % large2);
+  EXPECT_EQ(large, large % (-large2));
+  EXPECT_EQ(one_nano, large2 % large);
+  EXPECT_EQ(-one_nano, (-large2) % large);
+  EXPECT_EQ(one_nano, large2 % (-large));
+  // Some corner cases about negative values.
+  //
+  // (-5) / 2 = -2, remainder = -1
+  // (-5) / (-2) = 2, remainder = -1
+  a = TimeUtil::NanosecondsToDuration(-5);
+  EXPECT_EQ(TimeUtil::NanosecondsToDuration(-2), a / 2);
+  EXPECT_EQ(TimeUtil::NanosecondsToDuration(2), a / (-2));
+  b = TimeUtil::NanosecondsToDuration(2);
+  EXPECT_EQ(-2, a / b);
+  EXPECT_EQ(TimeUtil::NanosecondsToDuration(-1), a % b);
+  EXPECT_EQ(2, a / (-b));
+  EXPECT_EQ(TimeUtil::NanosecondsToDuration(-1), a % (-b));
+
+  // Test relational operators.
+  EXPECT_TRUE(one_nano < one_second);
+  EXPECT_FALSE(one_second < one_second);
+  EXPECT_FALSE(one_second < one_nano);
+  EXPECT_FALSE(-one_nano < -one_second);
+  EXPECT_FALSE(-one_second < -one_second);
+  EXPECT_TRUE(-one_second < -one_nano);
+  EXPECT_TRUE(-one_nano < one_nano);
+  EXPECT_FALSE(one_nano < -one_nano);
+
+  EXPECT_FALSE(one_nano > one_second);
+  EXPECT_FALSE(one_nano > one_nano);
+  EXPECT_TRUE(one_second > one_nano);
+
+  EXPECT_FALSE(one_nano >= one_second);
+  EXPECT_TRUE(one_nano >= one_nano);
+  EXPECT_TRUE(one_second >= one_nano);
+
+  EXPECT_TRUE(one_nano <= one_second);
+  EXPECT_TRUE(one_nano <= one_nano);
+  EXPECT_FALSE(one_second <= one_nano);
+
+  EXPECT_TRUE(one_nano == one_nano);
+  EXPECT_FALSE(one_nano == one_second);
+
+  EXPECT_FALSE(one_nano != one_nano);
+  EXPECT_TRUE(one_nano != one_second);
+}
+
+TEST(TimeUtilTest, TimestampOperators) {
+  Timestamp begin, end;
+  EXPECT_TRUE(TimeUtil::FromString("0001-01-01T00:00:00Z", &begin));
+  EXPECT_TRUE(TimeUtil::FromString("9999-12-31T23:59:59.999999999Z", &end));
+  Duration d = end - begin;
+  EXPECT_TRUE(end == begin + d);
+  EXPECT_TRUE(end == d + begin);
+  EXPECT_TRUE(begin == end - d);
+
+  // Test relational operators
+  Timestamp t1 = begin + d / 4;
+  Timestamp t2 = end - d / 4;
+  EXPECT_TRUE(t1 < t2);
+  EXPECT_FALSE(t1 < t1);
+  EXPECT_FALSE(t2 < t1);
+  EXPECT_FALSE(t1 > t2);
+  EXPECT_FALSE(t1 > t1);
+  EXPECT_TRUE(t2 > t1);
+  EXPECT_FALSE(t1 >= t2);
+  EXPECT_TRUE(t1 >= t1);
+  EXPECT_TRUE(t2 >= t1);
+  EXPECT_TRUE(t1 <= t2);
+  EXPECT_TRUE(t1 <= t1);
+  EXPECT_FALSE(t2 <= t1);
+
+  EXPECT_FALSE(t1 == t2);
+  EXPECT_TRUE(t1 == t1);
+  EXPECT_FALSE(t2 == t1);
+  EXPECT_TRUE(t1 != t2);
+  EXPECT_FALSE(t1 != t1);
+  EXPECT_TRUE(t2 != t1);
+}
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/type_resolver.h b/src/google/protobuf/util/type_resolver.h
new file mode 100644
index 0000000..77d4416
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver.h
@@ -0,0 +1,75 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_H__
+#define GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+#include <google/protobuf/stubs/status.h>
+
+
+namespace google {
+namespace protobuf {
+class Type;
+class Enum;
+}  // namespace protobuf
+
+
+namespace protobuf {
+class DescriptorPool;
+namespace util {
+
+// Abstract interface for a type resovler.
+//
+// Implementations of this interface must be thread-safe.
+class LIBPROTOBUF_EXPORT TypeResolver {
+ public:
+  TypeResolver() {}
+  virtual ~TypeResolver() {}
+
+  // Resolves a type url for a message type.
+  virtual util::Status ResolveMessageType(
+      const string& type_url, google::protobuf::Type* message_type) = 0;
+
+  // Resolves a type url for an enum type.
+  virtual util::Status ResolveEnumType(const string& type_url,
+                                         google::protobuf::Enum* enum_type) = 0;
+
+ private:
+  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(TypeResolver);
+};
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_H__
diff --git a/src/google/protobuf/util/type_resolver_util.cc b/src/google/protobuf/util/type_resolver_util.cc
new file mode 100644
index 0000000..9639390
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver_util.cc
@@ -0,0 +1,259 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/type_resolver_util.h>
+
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/descriptor.pb.h>
+#include <google/protobuf/descriptor.h>
+#include <google/protobuf/util/internal/utility.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/stubs/strutil.h>
+#include <google/protobuf/stubs/status.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+using google::protobuf::BoolValue;
+using google::protobuf::Enum;
+using google::protobuf::EnumValue;
+using google::protobuf::Field;
+using google::protobuf::Option;
+using google::protobuf::Type;
+
+using util::Status;
+using util::error::INVALID_ARGUMENT;
+using util::error::NOT_FOUND;
+
+bool SplitTypeUrl(const string& type_url, string* url_prefix,
+                  string* message_name) {
+  size_t pos = type_url.find_last_of("/");
+  if (pos == string::npos) {
+    return false;
+  }
+  *url_prefix = type_url.substr(0, pos);
+  *message_name = type_url.substr(pos + 1);
+  return true;
+}
+
+class DescriptorPoolTypeResolver : public TypeResolver {
+ public:
+  DescriptorPoolTypeResolver(const string& url_prefix,
+                             const DescriptorPool* pool)
+      : url_prefix_(url_prefix), pool_(pool) {}
+
+  Status ResolveMessageType(const string& type_url, Type* type) {
+    string url_prefix, message_name;
+    if (!SplitTypeUrl(type_url, &url_prefix, &message_name) ||
+        url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT,
+                    StrCat("Invalid type URL, type URLs must be of the form '",
+                           url_prefix_, "/<typename>', got: ", type_url));
+    }
+    if (url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT,
+                    "Cannot resolve types from URL: " + url_prefix);
+    }
+    const Descriptor* descriptor = pool_->FindMessageTypeByName(message_name);
+    if (descriptor == NULL) {
+      return Status(NOT_FOUND,
+                    "Invalid type URL, unknown type: " + message_name);
+    }
+    ConvertDescriptor(descriptor, type);
+    return Status();
+  }
+
+  Status ResolveEnumType(const string& type_url, Enum* enum_type) {
+    string url_prefix, type_name;
+    if (!SplitTypeUrl(type_url, &url_prefix, &type_name) ||
+        url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT,
+                    StrCat("Invalid type URL, type URLs must be of the form '",
+                           url_prefix_, "/<typename>', got: ", type_url));
+    }
+    if (url_prefix != url_prefix_) {
+      return Status(INVALID_ARGUMENT,
+                    "Cannot resolve types from URL: " + url_prefix);
+    }
+    const EnumDescriptor* descriptor = pool_->FindEnumTypeByName(type_name);
+    if (descriptor == NULL) {
+      return Status(NOT_FOUND, "Invalid type URL, unknown type: " + type_name);
+    }
+    ConvertEnumDescriptor(descriptor, enum_type);
+    return Status();
+  }
+
+ private:
+  void ConvertDescriptor(const Descriptor* descriptor, Type* type) {
+    type->Clear();
+    type->set_name(descriptor->full_name());
+    for (int i = 0; i < descriptor->field_count(); ++i) {
+      const FieldDescriptor* field = descriptor->field(i);
+      if (field->type() == FieldDescriptor::TYPE_GROUP) {
+        // Group fields cannot be represented with Type. We discard them.
+        continue;
+      }
+      ConvertFieldDescriptor(descriptor->field(i), type->add_fields());
+    }
+    for (int i = 0; i < descriptor->oneof_decl_count(); ++i) {
+      type->add_oneofs(descriptor->oneof_decl(i)->name());
+    }
+    type->mutable_source_context()->set_file_name(descriptor->file()->name());
+    ConvertMessageOptions(descriptor->options(), type->mutable_options());
+  }
+
+  void ConvertMessageOptions(const MessageOptions& options,
+                             RepeatedPtrField<Option>* output) {
+    if (options.map_entry()) {
+      Option* option = output->Add();
+      option->set_name("map_entry");
+      BoolValue value;
+      value.set_value(true);
+      option->mutable_value()->PackFrom(value);
+    }
+
+    // TODO(xiaofeng): Set other "options"?
+  }
+
+  void ConvertFieldDescriptor(const FieldDescriptor* descriptor, Field* field) {
+    field->set_kind(static_cast<Field::Kind>(descriptor->type()));
+    switch (descriptor->label()) {
+      case FieldDescriptor::LABEL_OPTIONAL:
+        field->set_cardinality(Field::CARDINALITY_OPTIONAL);
+        break;
+      case FieldDescriptor::LABEL_REPEATED:
+        field->set_cardinality(Field::CARDINALITY_REPEATED);
+        break;
+      case FieldDescriptor::LABEL_REQUIRED:
+        field->set_cardinality(Field::CARDINALITY_REQUIRED);
+        break;
+    }
+    field->set_number(descriptor->number());
+    field->set_name(descriptor->name());
+    field->set_json_name(descriptor->json_name());
+    if (descriptor->has_default_value()) {
+      field->set_default_value(DefaultValueAsString(descriptor));
+    }
+    if (descriptor->type() == FieldDescriptor::TYPE_MESSAGE) {
+      field->set_type_url(GetTypeUrl(descriptor->message_type()));
+    } else if (descriptor->type() == FieldDescriptor::TYPE_ENUM) {
+      field->set_type_url(GetTypeUrl(descriptor->enum_type()));
+    }
+    if (descriptor->containing_oneof() != NULL) {
+      field->set_oneof_index(descriptor->containing_oneof()->index() + 1);
+    }
+    if (descriptor->is_packed()) {
+      field->set_packed(true);
+    }
+
+    // TODO(xiaofeng): Set other field "options"?
+  }
+
+  void ConvertEnumDescriptor(const EnumDescriptor* descriptor,
+                             Enum* enum_type) {
+    enum_type->Clear();
+    enum_type->set_name(descriptor->full_name());
+    enum_type->mutable_source_context()->set_file_name(
+        descriptor->file()->name());
+    for (int i = 0; i < descriptor->value_count(); ++i) {
+      const EnumValueDescriptor* value_descriptor = descriptor->value(i);
+      EnumValue* value = enum_type->mutable_enumvalue()->Add();
+      value->set_name(value_descriptor->name());
+      value->set_number(value_descriptor->number());
+
+      // TODO(xiaofeng): Set EnumValue options.
+    }
+    // TODO(xiaofeng): Set Enum "options".
+  }
+
+  string GetTypeUrl(const Descriptor* descriptor) {
+    return url_prefix_ + "/" + descriptor->full_name();
+  }
+
+  string GetTypeUrl(const EnumDescriptor* descriptor) {
+    return url_prefix_ + "/" + descriptor->full_name();
+  }
+
+  string DefaultValueAsString(const FieldDescriptor* descriptor) {
+    switch (descriptor->cpp_type()) {
+      case FieldDescriptor::CPPTYPE_INT32:
+        return SimpleItoa(descriptor->default_value_int32());
+        break;
+      case FieldDescriptor::CPPTYPE_INT64:
+        return SimpleItoa(descriptor->default_value_int64());
+        break;
+      case FieldDescriptor::CPPTYPE_UINT32:
+        return SimpleItoa(descriptor->default_value_uint32());
+        break;
+      case FieldDescriptor::CPPTYPE_UINT64:
+        return SimpleItoa(descriptor->default_value_uint64());
+        break;
+      case FieldDescriptor::CPPTYPE_FLOAT:
+        return SimpleFtoa(descriptor->default_value_float());
+        break;
+      case FieldDescriptor::CPPTYPE_DOUBLE:
+        return SimpleDtoa(descriptor->default_value_double());
+        break;
+      case FieldDescriptor::CPPTYPE_BOOL:
+        return descriptor->default_value_bool() ? "true" : "false";
+        break;
+      case FieldDescriptor::CPPTYPE_STRING:
+        if (descriptor->type() == FieldDescriptor::TYPE_BYTES) {
+          return CEscape(descriptor->default_value_string());
+        } else {
+          return descriptor->default_value_string();
+        }
+        break;
+      case FieldDescriptor::CPPTYPE_ENUM:
+        return descriptor->default_value_enum()->name();
+        break;
+      case FieldDescriptor::CPPTYPE_MESSAGE:
+        GOOGLE_LOG(DFATAL) << "Messages can't have default values!";
+        break;
+    }
+    return "";
+  }
+
+  string url_prefix_;
+  const DescriptorPool* pool_;
+};
+
+}  // namespace
+
+TypeResolver* NewTypeResolverForDescriptorPool(const string& url_prefix,
+                                               const DescriptorPool* pool) {
+  return new DescriptorPoolTypeResolver(url_prefix, pool);
+}
+
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google
diff --git a/src/google/protobuf/util/type_resolver_util.h b/src/google/protobuf/util/type_resolver_util.h
new file mode 100644
index 0000000..c0ef3c1
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver_util.h
@@ -0,0 +1,52 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#ifndef GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_UTIL_H__
+#define GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_UTIL_H__
+
+#include <string>
+
+#include <google/protobuf/stubs/common.h>
+namespace google {
+namespace protobuf {
+class DescriptorPool;
+namespace util {
+class TypeResolver;
+
+// Creates a TypeResolver that serves type information in the given descriptor
+// pool. Caller takes ownership of the returned TypeResolver.
+LIBPROTOBUF_EXPORT TypeResolver* NewTypeResolverForDescriptorPool(
+    const string& url_prefix, const DescriptorPool* pool);
+
+}  // namespace util
+}  // namespace protobuf
+
+}  // namespace google
+#endif  // GOOGLE_PROTOBUF_UTIL_TYPE_RESOLVER_UTIL_H__
diff --git a/src/google/protobuf/util/type_resolver_util_test.cc b/src/google/protobuf/util/type_resolver_util_test.cc
new file mode 100644
index 0000000..8a0bf65
--- /dev/null
+++ b/src/google/protobuf/util/type_resolver_util_test.cc
@@ -0,0 +1,352 @@
+// Protocol Buffers - Google's data interchange format
+// Copyright 2008 Google Inc.  All rights reserved.
+// https://developers.google.com/protocol-buffers/
+//
+// Redistribution and use in source and binary forms, with or without
+// modification, are permitted provided that the following conditions are
+// met:
+//
+//     * Redistributions of source code must retain the above copyright
+// notice, this list of conditions and the following disclaimer.
+//     * Redistributions in binary form must reproduce the above
+// copyright notice, this list of conditions and the following disclaimer
+// in the documentation and/or other materials provided with the
+// distribution.
+//     * Neither the name of Google Inc. nor the names of its
+// contributors may be used to endorse or promote products derived from
+// this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+#include <google/protobuf/util/type_resolver_util.h>
+
+#include <limits>
+#include <memory>
+#ifndef _SHARED_PTR_H
+#include <google/protobuf/stubs/shared_ptr.h>
+#endif
+#include <string>
+#include <vector>
+
+#include <google/protobuf/type.pb.h>
+#include <google/protobuf/wrappers.pb.h>
+#include <google/protobuf/map_unittest.pb.h>
+#include <google/protobuf/test_util.h>
+#include <google/protobuf/unittest.pb.h>
+#include <google/protobuf/util/json_format_proto3.pb.h>
+#include <google/protobuf/util/type_resolver.h>
+#include <google/protobuf/testing/googletest.h>
+#include <gtest/gtest.h>
+
+namespace google {
+namespace protobuf {
+namespace util {
+namespace {
+using google::protobuf::Type;
+using google::protobuf::Enum;
+using google::protobuf::Field;
+using google::protobuf::Option;
+using google::protobuf::BoolValue;
+
+static const char kUrlPrefix[] = "type.googleapis.com";
+
+class DescriptorPoolTypeResolverTest : public testing::Test {
+ public:
+  DescriptorPoolTypeResolverTest() {
+    resolver_.reset(NewTypeResolverForDescriptorPool(
+        kUrlPrefix, DescriptorPool::generated_pool()));
+  }
+
+  const Field* FindField(const Type& type, const string& name) {
+    for (int i = 0; i < type.fields_size(); ++i) {
+      const Field& field = type.fields(i);
+      if (field.name() == name) {
+        return &field;
+      }
+    }
+    return NULL;
+  }
+
+  bool HasField(const Type& type, const string& name) {
+    return FindField(type, name) != NULL;
+  }
+
+  bool HasField(const Type& type, Field::Cardinality cardinality,
+                Field::Kind kind, const string& name, int number) {
+    const Field* field = FindField(type, name);
+    if (field == NULL) {
+      return false;
+    }
+    return field->cardinality() == cardinality &&
+        field->kind() == kind && field->number() == number;
+  }
+
+  bool CheckFieldTypeUrl(const Type& type, const string& name,
+                         const string& type_url) {
+    const Field* field = FindField(type, name);
+    if (field == NULL) {
+      return false;
+    }
+    return field->type_url() == type_url;
+  }
+
+  bool FieldInOneof(const Type& type, const string& name,
+                    const string& oneof_name) {
+    const Field* field = FindField(type, name);
+    if (field == NULL || field->oneof_index() <= 0 ||
+        field->oneof_index() > type.oneofs_size()) {
+      return false;
+    }
+    return type.oneofs(field->oneof_index() - 1) == oneof_name;
+  }
+
+  bool IsPacked(const Type& type, const string& name) {
+    const Field* field = FindField(type, name);
+    if (field == NULL) {
+      return false;
+    }
+    return field->packed();
+  }
+
+  bool EnumHasValue(const Enum& type, const string& name, int number) {
+    for (int i = 0; i < type.enumvalue_size(); ++i) {
+      if (type.enumvalue(i).name() == name &&
+          type.enumvalue(i).number() == number) {
+        return true;
+      }
+    }
+    return false;
+  }
+
+  bool HasBoolOption(const RepeatedPtrField<Option>& options,
+                     const string& name, bool value) {
+    for (int i = 0; i < options.size(); ++i) {
+      const Option& option = options.Get(i);
+      if (option.name() == name) {
+        BoolValue bool_value;
+        if (option.value().UnpackTo(&bool_value) &&
+            bool_value.value() == value) {
+          return true;
+        }
+      }
+    }
+    return false;
+  }
+
+  string GetTypeUrl(string full_name) {
+    return kUrlPrefix + string("/") + full_name;
+  }
+
+  template<typename T>
+  string GetTypeUrl() {
+    return GetTypeUrl(T::descriptor()->full_name());
+  }
+
+ protected:
+  google::protobuf::scoped_ptr<TypeResolver> resolver_;
+};
+
+TEST_F(DescriptorPoolTypeResolverTest, TestAllTypes) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestAllTypes>(), &type).ok());
+  // Check all optional fields.
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_INT32, "optional_int32", 1));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_INT64, "optional_int64", 2));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_UINT32, "optional_uint32", 3));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_UINT64, "optional_uint64", 4));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SINT32, "optional_sint32", 5));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SINT64, "optional_sint64", 6));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_FIXED32, "optional_fixed32", 7));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_FIXED64, "optional_fixed64", 8));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SFIXED32, "optional_sfixed32", 9));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_SFIXED64, "optional_sfixed64", 10));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_FLOAT, "optional_float", 11));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_DOUBLE, "optional_double", 12));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_BOOL, "optional_bool", 13));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_STRING, "optional_string", 14));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_BYTES, "optional_bytes", 15));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_MESSAGE, "optional_nested_message", 18));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_MESSAGE, "optional_foreign_message", 19));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_nested_message",
+      GetTypeUrl<protobuf_unittest::TestAllTypes::NestedMessage>()));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_foreign_message",
+      GetTypeUrl<protobuf_unittest::ForeignMessage>()));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_ENUM, "optional_nested_enum", 21));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_ENUM, "optional_foreign_enum", 22));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_nested_enum",
+      GetTypeUrl("protobuf_unittest.TestAllTypes.NestedEnum")));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "optional_foreign_enum",
+      GetTypeUrl("protobuf_unittest.ForeignEnum")));
+
+  // Check all repeated fields.
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_INT32, "repeated_int32", 31));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_INT64, "repeated_int64", 32));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_UINT32, "repeated_uint32", 33));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_UINT64, "repeated_uint64", 34));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SINT32, "repeated_sint32", 35));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SINT64, "repeated_sint64", 36));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_FIXED32, "repeated_fixed32", 37));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_FIXED64, "repeated_fixed64", 38));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SFIXED32, "repeated_sfixed32", 39));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_SFIXED64, "repeated_sfixed64", 40));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_FLOAT, "repeated_float", 41));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_DOUBLE, "repeated_double", 42));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_BOOL, "repeated_bool", 43));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_STRING, "repeated_string", 44));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_BYTES, "repeated_bytes", 45));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_MESSAGE, "repeated_nested_message", 48));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_MESSAGE, "repeated_foreign_message", 49));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_nested_message",
+      GetTypeUrl<protobuf_unittest::TestAllTypes::NestedMessage>()));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_foreign_message",
+      GetTypeUrl<protobuf_unittest::ForeignMessage>()));
+
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_ENUM, "repeated_nested_enum", 51));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_ENUM, "repeated_foreign_enum", 52));
+
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_nested_enum",
+      GetTypeUrl("protobuf_unittest.TestAllTypes.NestedEnum")));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "repeated_foreign_enum",
+      GetTypeUrl("protobuf_unittest.ForeignEnum")));
+
+  // Groups are discarded when converting to Type.
+  const Descriptor* descriptor = protobuf_unittest::TestAllTypes::descriptor();
+  EXPECT_TRUE(descriptor->FindFieldByName("optionalgroup") != NULL);
+  EXPECT_TRUE(descriptor->FindFieldByName("repeatedgroup") != NULL);
+  ASSERT_FALSE(HasField(type, "optionalgroup"));
+  ASSERT_FALSE(HasField(type, "repeatedgroup"));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestPackedField) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestPackedTypes>(), &type).ok());
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_INT32, "packed_int32", 90));
+  EXPECT_TRUE(IsPacked(type, "packed_int32"));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestOneof) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestAllTypes>(), &type).ok());
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_UINT32, "oneof_uint32", 111));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_MESSAGE, "oneof_nested_message", 112));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_STRING, "oneof_string", 113));
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_OPTIONAL,
+                       Field::TYPE_BYTES, "oneof_bytes", 114));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_uint32", "oneof_field"));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_nested_message", "oneof_field"));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_string", "oneof_field"));
+  EXPECT_TRUE(FieldInOneof(type, "oneof_bytes", "oneof_field"));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestMap) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl<protobuf_unittest::TestMap>(), &type).ok());
+  EXPECT_TRUE(HasField(type, Field::CARDINALITY_REPEATED,
+                       Field::TYPE_MESSAGE, "map_int32_int32", 1));
+  EXPECT_TRUE(CheckFieldTypeUrl(
+      type, "map_int32_int32",
+      GetTypeUrl("protobuf_unittest.TestMap.MapInt32Int32Entry")));
+
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+      GetTypeUrl("protobuf_unittest.TestMap.MapInt32Int32Entry"),
+      &type).ok());
+  EXPECT_TRUE(HasBoolOption(type.options(), "map_entry", true));
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestEnum) {
+  Enum type;
+  ASSERT_TRUE(resolver_->ResolveEnumType(
+      GetTypeUrl("protobuf_unittest.TestAllTypes.NestedEnum"), &type).ok());
+  EnumHasValue(type, "FOO", 1);
+  EnumHasValue(type, "BAR", 2);
+  EnumHasValue(type, "BAZ", 3);
+  EnumHasValue(type, "NEG", -1);
+}
+
+TEST_F(DescriptorPoolTypeResolverTest, TestJsonName) {
+  Type type;
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+                           GetTypeUrl<protobuf_unittest::TestAllTypes>(), &type)
+                  .ok());
+  EXPECT_EQ("optionalInt32", FindField(type, "optional_int32")->json_name());
+
+  ASSERT_TRUE(resolver_->ResolveMessageType(
+                           GetTypeUrl<proto3::TestCustomJsonName>(), &type)
+                  .ok());
+  EXPECT_EQ("@value", FindField(type, "value")->json_name());
+}
+
+}  // namespace
+}  // namespace util
+}  // namespace protobuf
+}  // namespace google