src/google/protobuf/message_lite.h

// 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.

// Authors: wink@google.com (Wink Saville),
//          kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// Defines MessageLite, the abstract interface implemented by all (lite
// and non-lite) protocol message objects.

#ifndef GOOGLE_PROTOBUF_MESSAGE_LITE_H__
#define GOOGLE_PROTOBUF_MESSAGE_LITE_H__

#include <climits>
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/stubs/logging.h>
#include <google/protobuf/stubs/once.h>
#include <google/protobuf/arena.h>
#include <google/protobuf/stubs/port.h>

namespace google {
namespace protobuf {
template <typename T>
class RepeatedPtrField;
namespace io {
class CodedInputStream;
class CodedOutputStream;
class ZeroCopyInputStream;
class ZeroCopyOutputStream;
}
namespace internal {

class RepeatedPtrFieldBase;
class WireFormatLite;
class WeakFieldMap;

#ifndef SWIG
// We compute sizes as size_t but cache them as int.  This function converts a
// computed size to a cached size.  Since we don't proceed with serialization
// if the total size was > INT_MAX, it is not important what this function
// returns for inputs > INT_MAX.  However this case should not error or
// GOOGLE_CHECK-fail, because the full size_t resolution is still returned from
// ByteSizeLong() and checked against INT_MAX; we can catch the overflow
// there.
inline int ToCachedSize(size_t size) { return static_cast<int>(size); }

// We mainly calculate sizes in terms of size_t, but some functions that
// compute sizes return "int".  These int sizes are expected to always be
// positive. This function is more efficient than casting an int to size_t
// directly on 64-bit platforms because it avoids making the compiler emit a
// sign extending instruction, which we don't want and don't want to pay for.
inline size_t FromIntSize(int size) {
  // Convert to unsigned before widening so sign extension is not necessary.
  return static_cast<unsigned int>(size);
}

// For cases where a legacy function returns an integer size.  We GOOGLE_DCHECK()
// that the conversion will fit within an integer; if this is false then we
// are losing information.
inline int ToIntSize(size_t size) {
  GOOGLE_DCHECK_LE(size, static_cast<size_t>(INT_MAX));
  return static_cast<int>(size);
}

// This type wraps a variable whose constructor and destructor are explicitly
// called. It is particularly useful for a global variable, without its
// constructor and destructor run on start and end of the program lifetime.
// This circumvents the initial construction order fiasco, while keeping
// the address of the empty string a compile time constant.
//
// Pay special attention to the initialization state of the object.
// 1. The object is "uninitialized" to begin with.
// 2. Call DefaultConstruct() only if the object is uninitialized.
//    After the call, the object becomes "initialized".
// 3. Call get() and get_mutable() only if the object is initialized.
// 4. Call Destruct() only if the object is initialized.
//    After the call, the object becomes uninitialized.
template <typename T>
class ExplicitlyConstructed {
 public:
  void DefaultConstruct() {
    new (&union_) T();
  }

  void Destruct() {
    get_mutable()->~T();
  }

  constexpr const T& get() const { return reinterpret_cast<const T&>(union_); }
  T* get_mutable() { return reinterpret_cast<T*>(&union_); }

 private:
  // Prefer c++14 aligned_storage, but for compatibility this will do.
  union AlignedUnion {
    char space[sizeof(T)];
    int64 align_to_int64;
    void* align_to_ptr;
  } union_;
};

// Default empty string object. Don't use this directly. Instead, call
// GetEmptyString() to get the reference.
LIBPROTOBUF_EXPORT extern ExplicitlyConstructed<::std::string> fixed_address_empty_string;

LIBPROTOBUF_EXPORT inline const ::std::string& GetEmptyStringAlreadyInited() {
  return fixed_address_empty_string.get();
}

LIBPROTOBUF_EXPORT size_t StringSpaceUsedExcludingSelfLong(const string& str);
#endif  // SWIG
}  // namespace internal

// Interface to light weight protocol messages.
//
// This interface is implemented by all protocol message objects.  Non-lite
// messages additionally implement the Message interface, which is a
// subclass of MessageLite.  Use MessageLite instead when you only need
// the subset of features which it supports -- namely, nothing that uses
// descriptors or reflection.  You can instruct the protocol compiler
// to generate classes which implement only MessageLite, not the full
// Message interface, by adding the following line to the .proto file:
//
//   option optimize_for = LITE_RUNTIME;
//
// This is particularly useful on resource-constrained systems where
// the full protocol buffers runtime library is too big.
//
// Note that on non-constrained systems (e.g. servers) when you need
// to link in lots of protocol definitions, a better way to reduce
// total code footprint is to use optimize_for = CODE_SIZE.  This
// will make the generated code smaller while still supporting all the
// same features (at the expense of speed).  optimize_for = LITE_RUNTIME
// is best when you only have a small number of message types linked
// into your binary, in which case the size of the protocol buffers
// runtime itself is the biggest problem.
class LIBPROTOBUF_EXPORT MessageLite {
 public:
  inline MessageLite() {}
  virtual ~MessageLite() {}

  // Basic Operations ------------------------------------------------

  // Get the name of this message type, e.g. "foo.bar.BazProto".
  virtual string GetTypeName() const = 0;

  // Construct a new instance of the same type.  Ownership is passed to the
  // caller.
  virtual MessageLite* New() const = 0;

  // Construct a new instance on the arena. Ownership is passed to the caller
  // if arena is a NULL. Default implementation for backwards compatibility.
  virtual MessageLite* New(::google::protobuf::Arena* arena) const;

  // Get the arena, if any, associated with this message. Virtual method
  // required for generic operations but most arena-related operations should
  // use the GetArenaNoVirtual() generated-code method. Default implementation
  // to reduce code size by avoiding the need for per-type implementations
  // when types do not implement arena support.
  virtual ::google::protobuf::Arena* GetArena() const { return NULL; }

  // Get a pointer that may be equal to this message's arena, or may not be.
  // If the value returned by this method is equal to some arena pointer, then
  // this message is on that arena; however, if this message is on some arena,
  // this method may or may not return that arena's pointer. As a tradeoff,
  // this method may be more efficient than GetArena(). The intent is to allow
  // underlying representations that use e.g. tagged pointers to sometimes
  // store the arena pointer directly, and sometimes in a more indirect way,
  // and allow a fastpath comparison against the arena pointer when it's easy
  // to obtain.
  virtual void* GetMaybeArenaPointer() const { return GetArena(); }

  // Clear all fields of the message and set them to their default values.
  // Clear() avoids freeing memory, assuming that any memory allocated
  // to hold parts of the message will be needed again to hold the next
  // message.  If you actually want to free the memory used by a Message,
  // you must delete it.
  virtual void Clear() = 0;

  // Quickly check if all required fields have values set.
  virtual bool IsInitialized() const = 0;

  // This is not implemented for Lite messages -- it just returns "(cannot
  // determine missing fields for lite message)".  However, it is implemented
  // for full messages.  See message.h.
  virtual string InitializationErrorString() const;

  // If |other| is the exact same class as this, calls MergeFrom(). Otherwise,
  // results are undefined (probably crash).
  virtual void CheckTypeAndMergeFrom(const MessageLite& other) = 0;

  // Parsing ---------------------------------------------------------
  // Methods for parsing in protocol buffer format.  Most of these are
  // just simple wrappers around MergeFromCodedStream().  Clear() will be
  // called before merging the input.

  // Fill the message with a protocol buffer parsed from the given input
  // stream. Returns false on a read error or if the input is in the wrong
  // format.  A successful return does not indicate the entire input is
  // consumed, ensure you call ConsumedEntireMessage() to check that if
  // applicable.
  bool ParseFromCodedStream(io::CodedInputStream* input);
  // Like ParseFromCodedStream(), but accepts messages that are missing
  // required fields.
  bool ParsePartialFromCodedStream(io::CodedInputStream* input);
  // Read a protocol buffer from the given zero-copy input stream.  If
  // successful, the entire input will be consumed.
  bool ParseFromZeroCopyStream(io::ZeroCopyInputStream* input);
  // Like ParseFromZeroCopyStream(), but accepts messages that are missing
  // required fields.
  bool ParsePartialFromZeroCopyStream(io::ZeroCopyInputStream* input);
  // Read a protocol buffer from the given zero-copy input stream, expecting
  // the message to be exactly "size" bytes long.  If successful, exactly
  // this many bytes will have been consumed from the input.
  bool ParseFromBoundedZeroCopyStream(io::ZeroCopyInputStream* input, int size);
  // Like ParseFromBoundedZeroCopyStream(), but accepts messages that are
  // missing required fields.
  bool ParsePartialFromBoundedZeroCopyStream(io::ZeroCopyInputStream* input,
                                             int size);
  // Parses a protocol buffer contained in a string. Returns true on success.
  // This function takes a string in the (non-human-readable) binary wire
  // format, matching the encoding output by MessageLite::SerializeToString().
  // If you'd like to convert a human-readable string into a protocol buffer
  // object, see google::protobuf::TextFormat::ParseFromString().
  bool ParseFromString(const string& data);
  // Like ParseFromString(), but accepts messages that are missing
  // required fields.
  bool ParsePartialFromString(const string& data);
  // Parse a protocol buffer contained in an array of bytes.
  bool ParseFromArray(const void* data, int size);
  // Like ParseFromArray(), but accepts messages that are missing
  // required fields.
  bool ParsePartialFromArray(const void* data, int size);


  // Reads a protocol buffer from the stream and merges it into this
  // Message.  Singular fields read from the what is
  // already in the Message and repeated fields are appended to those
  // already present.
  //
  // It is the responsibility of the caller to call input->LastTagWas()
  // (for groups) or input->ConsumedEntireMessage() (for non-groups) after
  // this returns to verify that the message's end was delimited correctly.
  //
  // ParsefromCodedStream() is implemented as Clear() followed by
  // MergeFromCodedStream().
  bool MergeFromCodedStream(io::CodedInputStream* input);

  // Like MergeFromCodedStream(), but succeeds even if required fields are
  // missing in the input.
  //
  // MergeFromCodedStream() is just implemented as MergePartialFromCodedStream()
  // followed by IsInitialized().
  virtual bool MergePartialFromCodedStream(io::CodedInputStream* input) = 0;


  // Serialization ---------------------------------------------------
  // Methods for serializing in protocol buffer format.  Most of these
  // are just simple wrappers around ByteSize() and SerializeWithCachedSizes().

  // Write a protocol buffer of this message to the given output.  Returns
  // false on a write error.  If the message is missing required fields,
  // this may GOOGLE_CHECK-fail.
  bool SerializeToCodedStream(io::CodedOutputStream* output) const;
  // Like SerializeToCodedStream(), but allows missing required fields.
  bool SerializePartialToCodedStream(io::CodedOutputStream* output) const;
  // Write the message to the given zero-copy output stream.  All required
  // fields must be set.
  bool SerializeToZeroCopyStream(io::ZeroCopyOutputStream* output) const;
  // Like SerializeToZeroCopyStream(), but allows missing required fields.
  bool SerializePartialToZeroCopyStream(io::ZeroCopyOutputStream* output) const;
  // Serialize the message and store it in the given string.  All required
  // fields must be set.
  bool SerializeToString(string* output) const;
  // Like SerializeToString(), but allows missing required fields.
  bool SerializePartialToString(string* output) const;
  // Serialize the message and store it in the given byte array.  All required
  // fields must be set.
  bool SerializeToArray(void* data, int size) const;
  // Like SerializeToArray(), but allows missing required fields.
  bool SerializePartialToArray(void* data, int size) const;

  // Make a string encoding the message. Is equivalent to calling
  // SerializeToString() on a string and using that.  Returns the empty
  // string if SerializeToString() would have returned an error.
  // Note: If you intend to generate many such strings, you may
  // reduce heap fragmentation by instead re-using the same string
  // object with calls to SerializeToString().
  string SerializeAsString() const;
  // Like SerializeAsString(), but allows missing required fields.
  string SerializePartialAsString() const;

  // Like SerializeToString(), but appends to the data to the string's existing
  // contents.  All required fields must be set.
  bool AppendToString(string* output) const;
  // Like AppendToString(), but allows missing required fields.
  bool AppendPartialToString(string* output) const;

  // Computes the serialized size of the message.  This recursively calls
  // ByteSizeLong() on all embedded messages.
  //
  // ByteSizeLong() is generally linear in the number of fields defined for the
  // proto.
  virtual size_t ByteSizeLong() const = 0;

  // Legacy ByteSize() API.
  PROTOBUF_RUNTIME_DEPRECATED("Please use ByteSizeLong() instead")
  int ByteSize() const {
    return internal::ToIntSize(ByteSizeLong());
  }

  // Serializes the message without recomputing the size.  The message must not
  // have changed since the last call to ByteSize(), and the value returned by
  // ByteSize must be non-negative.  Otherwise the results are undefined.
  virtual void SerializeWithCachedSizes(
      io::CodedOutputStream* output) const;

  // Functions below here are not part of the public interface.  It isn't
  // enforced, but they should be treated as private, and will be private
  // at some future time.  Unfortunately the implementation of the "friend"
  // keyword in GCC is broken at the moment, but we expect it will be fixed.

  // Like SerializeWithCachedSizes, but writes directly to *target, returning
  // a pointer to the byte immediately after the last byte written.  "target"
  // must point at a byte array of at least ByteSize() bytes.  Whether to use
  // deterministic serialization, e.g., maps in sorted order, is determined by
  // CodedOutputStream::IsDefaultSerializationDeterministic().
  virtual uint8* SerializeWithCachedSizesToArray(uint8* target) const;

  // Returns the result of the last call to ByteSize().  An embedded message's
  // size is needed both to serialize it (because embedded messages are
  // length-delimited) and to compute the outer message's size.  Caching
  // the size avoids computing it multiple times.
  //
  // ByteSize() does not automatically use the cached size when available
  // because this would require invalidating it every time the message was
  // modified, which would be too hard and expensive.  (E.g. if a deeply-nested
  // sub-message is changed, all of its parents' cached sizes would need to be
  // invalidated, which is too much work for an otherwise inlined setter
  // method.)
  virtual int GetCachedSize() const = 0;

  virtual uint8* InternalSerializeWithCachedSizesToArray(bool deterministic,
                                                         uint8* target) const;

 protected:
  // CastToBase allows generated code to cast a RepeatedPtrField<T> to
  // RepeatedPtrFieldBase. We try to restrict access to RepeatedPtrFieldBase
  // because it is an implementation detail that user code should not access
  // directly.
  template <typename T>
  static ::google::protobuf::internal::RepeatedPtrFieldBase* CastToBase(
      ::google::protobuf::RepeatedPtrField<T>* repeated) {
    return repeated;
  }
  template <typename T>
  static const ::google::protobuf::internal::RepeatedPtrFieldBase& CastToBase(
      const ::google::protobuf::RepeatedPtrField<T>& repeated) {
    return repeated;
  }

  template <typename T>
  static T* CreateMaybeMessage(Arena* arena) {
    return Arena::CreateMaybeMessage<T>(arena);
  }

 private:
  // TODO(gerbens) make this a pure abstract function
  virtual const void* InternalGetTable() const { return NULL; }

  friend class internal::WireFormatLite;
  friend class Message;
  friend class internal::WeakFieldMap;

  GOOGLE_DISALLOW_EVIL_CONSTRUCTORS(MessageLite);
};

namespace internal {

extern bool LIBPROTOBUF_EXPORT proto3_preserve_unknown_;

// DO NOT USE: For migration only. Will be removed when Proto3 defaults to
// preserve unknowns.
inline bool GetProto3PreserveUnknownsDefault() {
  return proto3_preserve_unknown_;
}

// DO NOT USE: For migration only. Will be removed when Proto3 defaults to
// preserve unknowns.
void LIBPROTOBUF_EXPORT SetProto3PreserveUnknownsDefault(bool preserve);
}  // namespace internal


}  // namespace protobuf

}  // namespace google
#endif  // GOOGLE_PROTOBUF_MESSAGE_LITE_H__