src/google/protobuf/util/internal/proto_writer.cc

// 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