diff --git a/internal/ceres/stringprintf.cc b/internal/ceres/stringprintf.cc
new file mode 100644
index 0000000..b3b7474
--- /dev/null
+++ b/internal/ceres/stringprintf.cc
@@ -0,0 +1,145 @@
+// Ceres Solver - A fast non-linear least squares minimizer
+// Copyright 2015 Google Inc. All rights reserved.
+// http://ceres-solver.org/
+//
+// 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: Sanjay Ghemawat
+
+#include "ceres/stringprintf.h"
+
+#include <cerrno>
+#include <cstdarg>  // For va_list and related operations
+#include <cstdio>   // MSVC requires this for _vsnprintf
+#include <string>
+#include <vector>
+
+#include "ceres/internal/port.h"
+
+namespace ceres {
+namespace internal {
+
+using std::string;
+
+// va_copy() was defined in the C99 standard.  However, it did not appear in the
+// C++ standard until C++11.  This means that if Ceres is being compiled with a
+// strict pre-C++11 standard (e.g. -std=c++03), va_copy() will NOT be defined,
+// as we are using the C++ compiler (it would however be defined if we were
+// using the C compiler).  Note however that both GCC & Clang will in fact
+// define va_copy() when compiling for C++ if the C++ standard is not explicitly
+// specified (i.e. no -std=c++<XX> arg), even though it should not strictly be
+// defined unless -std=c++11 (or greater) was passed.
+#if !defined(va_copy)
+#if defined (__GNUC__)
+// On GCC/Clang, if va_copy() is not defined (C++ standard < C++11 explicitly
+// specified), use the internal __va_copy() version, which should be present
+// in even very old GCC versions.
+#define va_copy(d, s) __va_copy(d, s)
+#else
+// Some older versions of MSVC do not have va_copy(), in which case define it.
+// Although this is required for older MSVC versions, it should also work for
+// other non-GCC/Clang compilers which also do not defined va_copy().
+#define va_copy(d, s) ((d) = (s))
+#endif  // defined (__GNUC__)
+#endif  // !defined(va_copy)
+
+void StringAppendV(string* dst, const char* format, va_list ap) {
+  // First try with a small fixed size buffer
+  char space[1024];
+
+  // It's possible for methods that use a va_list to invalidate
+  // the data in it upon use.  The fix is to make a copy
+  // of the structure before using it and use that copy instead.
+  va_list backup_ap;
+  va_copy(backup_ap, ap);
+  int result = vsnprintf(space, sizeof(space), format, backup_ap);
+  va_end(backup_ap);
+
+  if (result < sizeof(space)) {
+    if (result >= 0) {
+      // Normal case -- everything fit.
+      dst->append(space, result);
+      return;
+    }
+
+#if defined (_MSC_VER)
+    // Error or MSVC running out of space.  MSVC 8.0 and higher
+    // can be asked about space needed with the special idiom below:
+    va_copy(backup_ap, ap);
+    result = vsnprintf(NULL, 0, format, backup_ap);
+    va_end(backup_ap);
+#endif
+
+    if (result < 0) {
+      // Just an error.
+      return;
+    }
+  }
+
+  // Increase the buffer size to the size requested by vsnprintf,
+  // plus one for the closing \0.
+  int length = result+1;
+  char* buf = new char[length];
+
+  // Restore the va_list before we use it again
+  va_copy(backup_ap, ap);
+  result = vsnprintf(buf, length, format, backup_ap);
+  va_end(backup_ap);
+
+  if (result >= 0 && result < length) {
+    // It fit
+    dst->append(buf, result);
+  }
+  delete[] buf;
+}
+
+
+string StringPrintf(const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  string result;
+  StringAppendV(&result, format, ap);
+  va_end(ap);
+  return result;
+}
+
+const string& SStringPrintf(string* dst, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  dst->clear();
+  StringAppendV(dst, format, ap);
+  va_end(ap);
+  return *dst;
+}
+
+void StringAppendF(string* dst, const char* format, ...) {
+  va_list ap;
+  va_start(ap, format);
+  StringAppendV(dst, format, ap);
+  va_end(ap);
+}
+
+}  // namespace internal
+}  // namespace ceres