path: root/src/google/protobuf/compiler/cpp/cpp_message.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.

// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.

#include <algorithm>
#include <google/protobuf/stubs/hash.h>
#include <map>
#include <memory>
#ifndef _SHARED_PTR_H
#include <google/protobuf/stubs/shared_ptr.h>
#endif
#include <utility>
#include <vector>
#include <google/protobuf/compiler/cpp/cpp_message.h>
#include <google/protobuf/compiler/cpp/cpp_field.h>
#include <google/protobuf/compiler/cpp/cpp_enum.h>
#include <google/protobuf/compiler/cpp/cpp_extension.h>
#include <google/protobuf/compiler/cpp/cpp_helpers.h>
#include <google/protobuf/stubs/strutil.h>
#include <google/protobuf/io/printer.h>
#include <google/protobuf/io/coded_stream.h>
#include <google/protobuf/wire_format.h>
#include <google/protobuf/descriptor.pb.h>


namespace google {
namespace protobuf {
namespace compiler {
namespace cpp {

using internal::WireFormat;
using internal::WireFormatLite;

namespace {

template <class T>
void PrintFieldComment(io::Printer* printer, const T* field) {
  // Print the field's (or oneof's) proto-syntax definition as a comment.
  // We don't want to print group bodies so we cut off after the first
  // line.
  DebugStringOptions options;
  options.elide_group_body = true;
  options.elide_oneof_body = true;
  string def = field->DebugStringWithOptions(options);
  printer->Print("// $def$\n",
    "def", def.substr(0, def.find_first_of('\n')));
}

struct FieldOrderingByNumber {
  inline bool operator()(const FieldDescriptor* a,
                         const FieldDescriptor* b) const {
    return a->number() < b->number();
  }
};

// Sort the fields of the given Descriptor by number into a new[]'d array
// and return it.
std::vector<const FieldDescriptor*> SortFieldsByNumber(
    const Descriptor* descriptor) {
  std::vector<const FieldDescriptor*> fields(descriptor->field_count());
  for (int i = 0; i < descriptor->field_count(); i++) {
    fields[i] = descriptor->field(i);
  }
  std::sort(fields.begin(), fields.end(), FieldOrderingByNumber());
  return fields;
}

// Functor for sorting extension ranges by their "start" field number.
struct ExtensionRangeSorter {
  bool operator()(const Descriptor::ExtensionRange* left,
                  const Descriptor::ExtensionRange* right) const {
    return left->start < right->start;
  }
};

// Returns true if the "required" restriction check should be ignored for the
// given field.
inline static bool ShouldIgnoreRequiredFieldCheck(const FieldDescriptor* field,
                                                  const Options& options) {
  return false;
}

// Returns true if the message type has any required fields.  If it doesn't,
// we can optimize out calls to its IsInitialized() method.
//
// already_seen is used to avoid checking the same type multiple times
// (and also to protect against recursion).
static bool HasRequiredFields(const Descriptor* type, const Options& options,
                              hash_set<const Descriptor*>* already_seen) {
  if (already_seen->count(type) > 0) {
    // Since the first occurrence of a required field causes the whole
    // function to return true, we can assume that if the type is already
    // in the cache it didn't have any required fields.
    return false;
  }
  already_seen->insert(type);

  // If the type has extensions, an extension with message type could contain
  // required fields, so we have to be conservative and assume such an
  // extension exists.
  if (type->extension_range_count() > 0) return true;

  for (int i = 0; i < type->field_count(); i++) {
    const FieldDescriptor* field = type->field(i);
    if (field->is_required()) {
      return true;
    }
    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
        !ShouldIgnoreRequiredFieldCheck(field, options)) {
      if (HasRequiredFields(field->message_type(), options, already_seen)) {
        return true;
      }
    }
  }

  return false;
}

static bool HasRequiredFields(const Descriptor* type, const Options& options) {
  hash_set<const Descriptor*> already_seen;
  return HasRequiredFields(type, options, &already_seen);
}

// This returns an estimate of the compiler's alignment for the field.  This
// can't guarantee to be correct because the generated code could be compiled on
// different systems with different alignment rules.  The estimates below assume
// 64-bit pointers.
int EstimateAlignmentSize(const FieldDescriptor* field) {
  if (field == NULL) return 0;
  if (field->is_repeated()) return 8;
  switch (field->cpp_type()) {
    case FieldDescriptor::CPPTYPE_BOOL:
      return 1;

    case FieldDescriptor::CPPTYPE_INT32:
    case FieldDescriptor::CPPTYPE_UINT32:
    case FieldDescriptor::CPPTYPE_ENUM:
    case FieldDescriptor::CPPTYPE_FLOAT:
      return 4;

    case FieldDescriptor::CPPTYPE_INT64:
    case FieldDescriptor::CPPTYPE_UINT64:
    case FieldDescriptor::CPPTYPE_DOUBLE:
    case FieldDescriptor::CPPTYPE_STRING:
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return 8;
  }
  GOOGLE_LOG(FATAL) << "Can't get here.";
  return -1;  // Make compiler happy.
}

// FieldGroup is just a helper for OptimizePadding below.  It holds a vector of
// fields that are grouped together because they have compatible alignment, and
// a preferred location in the final field ordering.
class FieldGroup {
 public:
  FieldGroup()
      : preferred_location_(0) {}

  // A group with a single field.
  FieldGroup(float preferred_location, const FieldDescriptor* field)
      : preferred_location_(preferred_location),
        fields_(1, field) {}

  // Append the fields in 'other' to this group.
  void Append(const FieldGroup& other) {
    if (other.fields_.empty()) {
      return;
    }
    // Preferred location is the average among all the fields, so we weight by
    // the number of fields on each FieldGroup object.
    preferred_location_ =
        (preferred_location_ * fields_.size() +
         (other.preferred_location_ * other.fields_.size())) /
        (fields_.size() + other.fields_.size());
    fields_.insert(fields_.end(), other.fields_.begin(), other.fields_.end());
  }

  void SetPreferredLocation(float location) { preferred_location_ = location; }
  const std::vector<const FieldDescriptor*>& fields() const { return fields_; }

  // FieldGroup objects sort by their preferred location.
  bool operator<(const FieldGroup& other) const {
    return preferred_location_ < other.preferred_location_;
  }

 private:
  // "preferred_location_" is an estimate of where this group should go in the
  // final list of fields.  We compute this by taking the average index of each
  // field in this group in the original ordering of fields.  This is very
  // approximate, but should put this group close to where its member fields
  // originally went.
  float preferred_location_;
  std::vector<const FieldDescriptor*> fields_;
  // We rely on the default copy constructor and operator= so this type can be
  // used in a vector.
};

// Helper for the code that emits the Clear() method.
bool CanInitializeByZeroing(const FieldDescriptor* field) {
  if (field->is_repeated() || field->is_extension()) return false;
  switch (field->cpp_type()) {
    case internal::WireFormatLite::CPPTYPE_ENUM:
      return field->default_value_enum()->number() == 0;
    case internal::WireFormatLite::CPPTYPE_INT32:
      return field->default_value_int32() == 0;
    case internal::WireFormatLite::CPPTYPE_INT64:
      return field->default_value_int64() == 0;
    case internal::WireFormatLite::CPPTYPE_UINT32:
      return field->default_value_uint32() == 0;
    case internal::WireFormatLite::CPPTYPE_UINT64:
      return field->default_value_uint64() == 0;
    case internal::WireFormatLite::CPPTYPE_FLOAT:
      return field->default_value_float() == 0;
    case internal::WireFormatLite::CPPTYPE_DOUBLE:
      return field->default_value_double() == 0;
    case internal::WireFormatLite::CPPTYPE_BOOL:
      return field->default_value_bool() == false;
    default:
      return false;
  }
}

bool IsPOD(const FieldDescriptor* field) {
  if (field->is_repeated() || field->is_extension()) return false;
  switch (field->cpp_type()) {
    case internal::WireFormatLite::CPPTYPE_ENUM:
    case internal::WireFormatLite::CPPTYPE_INT32:
    case internal::WireFormatLite::CPPTYPE_INT64:
    case internal::WireFormatLite::CPPTYPE_UINT32:
    case internal::WireFormatLite::CPPTYPE_UINT64:
    case internal::WireFormatLite::CPPTYPE_FLOAT:
    case internal::WireFormatLite::CPPTYPE_DOUBLE:
    case internal::WireFormatLite::CPPTYPE_BOOL:
      return true;
    case internal::WireFormatLite::CPPTYPE_STRING:
      return false;
    default:
      return false;
  }
}

// Helper for the code that emits the SharedCtor() method.
bool CanConstructByZeroing(const FieldDescriptor* field,
                           const Options& options) {
  bool ret = CanInitializeByZeroing(field);

  // Non-repeated, non-lazy message fields are simply raw pointers, so we can
  // use memset to initialize these in SharedCtor.  We cannot use this in
  // Clear, as we need to potentially delete the existing value.
  ret = ret ||
      (!field->is_repeated() &&
       field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE);
  return ret;
}

// Reorder 'fields' so that if the fields are output into a c++ class in the new
// order, fields of similiar family (see below) are together and within each
// family, alignment padding is minimized.
//
// We try to do this while keeping each field as close as possible to its
// declaration order (from the .proto file) so that we don't reduce cache
// locality much for function that access each field in order.  This is also the
// only (weak) signal we have for author intent concerning field layout.
//
// TODO(ckennelly):  If/when we have profiles available for the compiler, use
// those rather than respect declaration order.
//
// We classify each field into a particular "family" of fields, that we perform
// the same operation on in our generated functions.
//
// REPEATED is placed first, as the C++ compiler automatically initializes
// these fields in layout order.
//
// STRING is grouped next, as our Clear/SharedCtor/SharedDtor walks it and
// calls ArenaStringPtr::Destroy on each.
//
//
// MESSAGE is grouped next, as our Clear/SharedDtor code walks it and calls
// delete on each.  We initialize these fields with a NULL pointer (see
// MessageFieldGenerator::GenerateConstructorCode), which allows them to be
// memset.
//
// ZERO_INITIALIZABLE is memset in Clear/SharedCtor
//
// OTHER these fields are initialized one-by-one.
void OptimizePadding(std::vector<const FieldDescriptor*>* fields,
                     const Options& options) {
  // The sorted numeric order of Family determines the declaration order in the
  // memory layout.
  enum Family {
    REPEATED = 0,
    STRING = 1,
    MESSAGE = 2,
    ZERO_INITIALIZABLE = 4,
    OTHER = 5,
    kMaxFamily
  };

  // First divide fields into those that align to 1 byte, 4 bytes or 8 bytes.
  std::vector<FieldGroup> aligned_to_1[kMaxFamily];
  std::vector<FieldGroup> aligned_to_4[kMaxFamily];
  std::vector<FieldGroup> aligned_to_8[kMaxFamily];
  for (int i = 0; i < fields->size(); ++i) {
    const FieldDescriptor* field = (*fields)[i];

    Family f = OTHER;
    if (field->is_repeated()) {
      f = REPEATED;
    } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING) {
      f = STRING;
    } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
      f = MESSAGE;

    } else if (CanInitializeByZeroing(field)) {
      f = ZERO_INITIALIZABLE;
    }

    switch (EstimateAlignmentSize(field)) {
      case 1: aligned_to_1[f].push_back(FieldGroup(i, field)); break;
      case 4: aligned_to_4[f].push_back(FieldGroup(i, field)); break;
      case 8: aligned_to_8[f].push_back(FieldGroup(i, field)); break;
      default:
        GOOGLE_LOG(FATAL) << "Unknown alignment size.";
    }
  }

  // For each family, group fields to optimize padding.
  for (int f = 0; f < kMaxFamily; f++) {
    // Now group fields aligned to 1 byte into sets of 4, and treat those like a
    // single field aligned to 4 bytes.
    for (int i = 0; i < aligned_to_1[f].size(); i += 4) {
      FieldGroup field_group;
      for (int j = i; j < aligned_to_1[f].size() && j < i + 4; ++j) {
        field_group.Append(aligned_to_1[f][j]);
      }
      aligned_to_4[f].push_back(field_group);
    }
    // Sort by preferred location to keep fields as close to their declaration
    // order as possible.  Using stable_sort ensures that the output is
    // consistent across runs.
    std::stable_sort(aligned_to_4[f].begin(), aligned_to_4[f].end());

    // Now group fields aligned to 4 bytes (or the 4-field groups created above)
    // into pairs, and treat those like a single field aligned to 8 bytes.
    for (int i = 0; i < aligned_to_4[f].size(); i += 2) {
      FieldGroup field_group;
      for (int j = i; j < aligned_to_4[f].size() && j < i + 2; ++j) {
        field_group.Append(aligned_to_4[f][j]);
      }
      if (i == aligned_to_4[f].size() - 1) {
        if (f == OTHER) {
          // Move incomplete 4-byte block to the beginning.  This is done to
          // pair with the (possible) leftover blocks from the
          // ZERO_INITIALIZABLE family.
          field_group.SetPreferredLocation(-1);
        } else {
          // Move incomplete 4-byte block to the end.
          field_group.SetPreferredLocation(fields->size() + 1);
        }
      }
      aligned_to_8[f].push_back(field_group);
    }
    // Sort by preferred location.
    std::stable_sort(aligned_to_8[f].begin(), aligned_to_8[f].end());
  }

  // Now pull out all the FieldDescriptors in order.
  fields->clear();
  for (int f = 0; f < kMaxFamily; ++f) {
    for (int i = 0; i < aligned_to_8[f].size(); ++i) {
      fields->insert(fields->end(),
                     aligned_to_8[f][i].fields().begin(),
                     aligned_to_8[f][i].fields().end());
    }
  }
}

string MessageTypeProtoName(const FieldDescriptor* field) {
  return field->message_type()->full_name();
}

// Emits an if-statement with a condition that evaluates to true if |field| is
// considered non-default (will be sent over the wire), for message types
// without true field presence. Should only be called if
// !HasFieldPresence(message_descriptor).
bool EmitFieldNonDefaultCondition(io::Printer* printer,
                                  const string& prefix,
                                  const FieldDescriptor* field) {
  // Merge and serialize semantics: primitive fields are merged/serialized only
  // if non-zero (numeric) or non-empty (string).
  if (!field->is_repeated() && !field->containing_oneof()) {
    if (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING) {
      printer->Print(
          "if ($prefix$$name$().size() > 0) {\n",
          "prefix", prefix,
          "name", FieldName(field));
    } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
      // Message fields still have has_$name$() methods.
      printer->Print(
          "if ($prefix$has_$name$()) {\n",
          "prefix", prefix,
          "name", FieldName(field));
    } else {
      printer->Print(
          "if ($prefix$$name$() != 0) {\n",
          "prefix", prefix,
          "name", FieldName(field));
    }
    printer->Indent();
    return true;
  } else if (field->containing_oneof()) {
    printer->Print(
        "if (has_$name$()) {\n",
        "name", FieldName(field));
    printer->Indent();
    return true;
  }
  return false;
}

// Does the given field have a has_$name$() method?
bool HasHasMethod(const FieldDescriptor* field) {
  if (HasFieldPresence(field->file())) {
    // In proto1/proto2, every field has a has_$name$() method.
    return true;
  }
  // For message types without true field presence, only fields with a message
  // type have a has_$name$() method.
  return field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE;
}

// Collects map entry message type information.
void CollectMapInfo(const Descriptor* descriptor,
                    std::map<string, string>* variables) {
  GOOGLE_CHECK(IsMapEntryMessage(descriptor));
  const FieldDescriptor* key = descriptor->FindFieldByName("key");
  const FieldDescriptor* val = descriptor->FindFieldByName("value");
  (*variables)["key"] = PrimitiveTypeName(key->cpp_type());
  switch (val->cpp_type()) {
    case FieldDescriptor::CPPTYPE_MESSAGE:
      (*variables)["val"] = FieldMessageTypeName(val);
      break;
    case FieldDescriptor::CPPTYPE_ENUM:
      (*variables)["val"] = ClassName(val->enum_type(), true);
      break;
    default:
      (*variables)["val"] = PrimitiveTypeName(val->cpp_type());
  }
  (*variables)["key_wire_type"] =
      "::google::protobuf::internal::WireFormatLite::TYPE_" +
      ToUpper(DeclaredTypeMethodName(key->type()));
  (*variables)["val_wire_type"] =
      "::google::protobuf::internal::WireFormatLite::TYPE_" +
      ToUpper(DeclaredTypeMethodName(val->type()));
}

// Does the given field have a private (internal helper only) has_$name$()
// method?
bool HasPrivateHasMethod(const FieldDescriptor* field) {
  // Only for oneofs in message types with no field presence. has_$name$(),
  // based on the oneof case, is still useful internally for generated code.
  return (!HasFieldPresence(field->file()) &&
          field->containing_oneof() != NULL);
}


}  // anonymous namespace

// ===================================================================

MessageGenerator::MessageGenerator(const Descriptor* descriptor,
                                   const Options& options)
    : descriptor_(descriptor),
      classname_(ClassName(descriptor, false)),
      options_(options),
      field_generators_(descriptor, options),
      nested_generators_(new google::protobuf::scoped_ptr<
          MessageGenerator>[descriptor->nested_type_count()]),
      enum_generators_(
          new google::protobuf::scoped_ptr<EnumGenerator>[descriptor->enum_type_count()]),
      extension_generators_(new google::protobuf::scoped_ptr<
          ExtensionGenerator>[descriptor->extension_count()]),
      use_dependent_base_(false) {

  // Compute optimized field order to be used for layout and initialization
  // purposes.
  for (int i = 0; i < descriptor_->field_count(); i++) {
    if (!descriptor_->field(i)->containing_oneof()) {
      optimized_order_.push_back(descriptor_->field(i));
    }
  }
  OptimizePadding(&optimized_order_, options_);

  if (HasFieldPresence(descriptor_->file())) {
    int has_bit_index = 0;
    has_bit_indices_.resize(descriptor_->field_count(), -1);
    for (int i = 0; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      // Skip fields that do not have has bits.
      if (field->is_repeated()) {
        continue;
      }

      has_bit_indices_[field->index()] = has_bit_index;
      has_bit_index++;
    }

    // Assign fields that do not use has bits to be at the end.  This can be
    // removed once we shrink the has bits we assign.
    //
    // TODO(ckennelly):  Shrink the has bits for these fields.
    for (int i = 0; i < descriptor_->field_count(); i++) {
      const FieldDescriptor* field = descriptor_->field(i);
      if (has_bit_indices_[field->index()] < 0) {
        has_bit_indices_[field->index()] = has_bit_index++;
      }
    }
  }

  for (int i = 0; i < descriptor->nested_type_count(); i++) {
    nested_generators_[i].reset(
      new MessageGenerator(descriptor->nested_type(i), options));
  }

  for (int i = 0; i < descriptor->enum_type_count(); i++) {
    enum_generators_[i].reset(
      new EnumGenerator(descriptor->enum_type(i), options));
  }

  for (int i = 0; i < descriptor->extension_count(); i++) {
    extension_generators_[i].reset(
      new ExtensionGenerator(descriptor->extension(i), options));
  }

  num_required_fields_ = 0;
  for (int i = 0; i < descriptor->field_count(); i++) {
    if (descriptor->field(i)->is_required()) {
      ++num_required_fields_;
    }
    if (options.proto_h && IsFieldDependent(descriptor->field(i))) {
      use_dependent_base_ = true;
    }
  }
  if (options.proto_h && descriptor->oneof_decl_count() > 0) {
    // Always make oneofs dependent.
    use_dependent_base_ = true;
  }
}

MessageGenerator::~MessageGenerator() {}

size_t MessageGenerator::HasBitsSize() const {
  // TODO(jieluo) - Optimize _has_bits_ for repeated and oneof fields.
  size_t sizeof_has_bits = (descriptor_->field_count() + 31) / 32 * 4;
  if (descriptor_->field_count() == 0) {
    // Zero-size arrays aren't technically allowed, and MSVC in particular
    // doesn't like them.  We still need to declare these arrays to make
    // other code compile.  Since this is an uncommon case, we'll just declare
    // them with size 1 and waste some space.  Oh well.
    sizeof_has_bits = 4;
  }

  return sizeof_has_bits;
}

void MessageGenerator::Flatten(std::vector<MessageGenerator*>* list) {
  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
    nested_generators_[i]->Flatten(list);
  }
  list->push_back(this);
}

void MessageGenerator::AddGenerators(
    std::vector<EnumGenerator*>* enum_generators,
    std::vector<ExtensionGenerator*>* extension_generators) {
  for (int i = 0; i < descriptor_->enum_type_count(); i++) {
    enum_generators->push_back(enum_generators_[i].get());
  }
  for (int i = 0; i < descriptor_->extension_count(); i++) {
    extension_generators->push_back(extension_generators_[i].get());
  }
}

void MessageGenerator::FillMessageForwardDeclarations(
    std::map<string, const Descriptor*>* class_names) {
  if (IsMapEntryMessage(descriptor_)) return;
  (*class_names)[classname_] = descriptor_;
}

void MessageGenerator::
GenerateDependentFieldAccessorDeclarations(io::Printer* printer) {
  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);

    PrintFieldComment(printer, field);

    std::map<string, string> vars;
    SetCommonFieldVariables(field, &vars, options_);

    if (use_dependent_base_ && IsFieldDependent(field)) {
      // If the message is dependent, the inline clear_*() method will need
      // to delete the message type, so it must be in the dependent base
      // class. (See also GenerateFieldAccessorDeclarations.)
      printer->Print(vars, "$deprecated_attr$void clear_$name$();\n");
    }
    // Generate type-specific accessor declarations.
    field_generators_.get(field).GenerateDependentAccessorDeclarations(printer);
    printer->Print("\n");
  }
}

void MessageGenerator::
GenerateFieldAccessorDeclarations(io::Printer* printer) {
  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);

    PrintFieldComment(printer, field);

    std::map<string, string> vars;
    SetCommonFieldVariables(field, &vars, options_);
    vars["constant_name"] = FieldConstantName(field);

    bool dependent_field = use_dependent_base_ && IsFieldDependent(field);
    if (dependent_field &&
        field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
        !field->is_map()) {
      // If this field is dependent, the dependent base class determines
      // the message type from the derived class (which is a template
      // parameter). This typedef is for that:
      printer->Print(
          "private:\n"
          "typedef $field_type$ $dependent_type$;\n"
          "public:\n",
          "field_type", FieldMessageTypeName(field),
          "dependent_type", DependentTypeName(field));
    }

    if (field->is_repeated()) {
      printer->Print(vars, "$deprecated_attr$int $name$_size() const;\n");
    } else if (HasHasMethod(field)) {
      printer->Print(vars, "$deprecated_attr$bool has_$name$() const;\n");
    } else if (HasPrivateHasMethod(field)) {
      printer->Print(vars,
          "private:\n"
          "bool has_$name$() const;\n"
          "public:\n");
    }

    if (!dependent_field) {
      // If this field is dependent, then its clear_() method is in the
      // depenent base class. (See also GenerateDependentAccessorDeclarations.)
      printer->Print(vars, "$deprecated_attr$void clear_$name$();\n");
    }
    printer->Print(vars,
                   "$deprecated_attr$static const int $constant_name$ = "
                   "$number$;\n");

    // Generate type-specific accessor declarations.
    field_generators_.get(field).GenerateAccessorDeclarations(printer);

    printer->Print("\n");
  }

  if (descriptor_->extension_range_count() > 0) {
    // Generate accessors for extensions.  We just call a macro located in
    // extension_set.h since the accessors about 80 lines of static code.
    printer->Print(
      "GOOGLE_PROTOBUF_EXTENSION_ACCESSORS($classname$)\n",
      "classname", classname_);
  }

  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "$camel_oneof_name$Case $oneof_name$_case() const;\n",
        "camel_oneof_name",
        UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true),
        "oneof_name", descriptor_->oneof_decl(i)->name());
  }
}

void MessageGenerator::
GenerateDependentFieldAccessorDefinitions(io::Printer* printer) {
  if (!use_dependent_base_) return;

  printer->Print("// $classname$\n\n", "classname",
                 DependentBaseClassTemplateName(descriptor_));

  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);

    if (field->options().weak()) continue;

    PrintFieldComment(printer, field);

    // These functions are not really dependent: they are part of the
    // (non-dependent) derived class. However, they need to live outside
    // any #ifdef guards, so we treat them as if they were dependent.
    //
    // See the comment in FileGenerator::GenerateInlineFunctionDefinitions
    // for a more complete explanation.
    if (use_dependent_base_ && IsFieldDependent(field)) {
      std::map<string, string> vars;
      SetCommonFieldVariables(field, &vars, options_);
      vars["inline"] = "inline ";
      if (field->containing_oneof()) {
        vars["field_name"] = UnderscoresToCamelCase(field->name(), true);
        vars["oneof_name"] = field->containing_oneof()->name();
        vars["oneof_index"] = SimpleItoa(field->containing_oneof()->index());
        GenerateOneofMemberHasBits(field, vars, printer);
      } else if (!field->is_repeated()) {
        // There will be no header guard, so this always has to be inline.
        GenerateSingularFieldHasBits(field, vars, printer);
      }
      // vars needed for clear_(), which is in the dependent base:
      // (See also GenerateDependentFieldAccessorDeclarations.)
      vars["tmpl"] = "template<class T>\n";
      vars["dependent_classname"] =
          DependentBaseClassTemplateName(descriptor_) + "<T>";
      vars["this_message"] = DependentBaseDownCast();
      vars["this_const_message"] = DependentBaseConstDownCast();
      GenerateFieldClear(field, vars, printer);
    }

    // Generate type-specific accessors.
    field_generators_.get(field)
        .GenerateDependentInlineAccessorDefinitions(printer);

    printer->Print("\n");
  }

  // Generate has_$name$() and clear_has_$name$() functions for oneofs
  // Similar to other has-bits, these must always be in the header if we
  // are using a dependent base class.
  GenerateOneofHasBits(printer, true /* is_inline */);
}

void MessageGenerator::
GenerateSingularFieldHasBits(const FieldDescriptor* field,
                             std::map<string, string> vars,
                             io::Printer* printer) {
  if (HasFieldPresence(descriptor_->file())) {
    // N.B.: without field presence, we do not use has-bits or generate
    // has_$name$() methods.
    int has_bit_index = has_bit_indices_[field->index()];
    GOOGLE_CHECK_GE(has_bit_index, 0);

    vars["has_array_index"] = SimpleItoa(has_bit_index / 32);
    vars["has_mask"] = StrCat(strings::Hex(1u << (has_bit_index % 32),
                                           strings::ZERO_PAD_8));
    printer->Print(vars,
      "$inline$"
      "bool $classname$::has_$name$() const {\n"
      "  return (_has_bits_[$has_array_index$] & 0x$has_mask$u) != 0;\n"
      "}\n"
      "$inline$"
      "void $classname$::set_has_$name$() {\n"
      "  _has_bits_[$has_array_index$] |= 0x$has_mask$u;\n"
      "}\n"
      "$inline$"
      "void $classname$::clear_has_$name$() {\n"
      "  _has_bits_[$has_array_index$] &= ~0x$has_mask$u;\n"
      "}\n");
  } else {
    // Message fields have a has_$name$() method.
    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
      bool is_lazy = false;
      if (is_lazy) {
        printer->Print(vars,
          "$inline$"
          "bool $classname$::has_$name$() const {\n"
          "  return !$name$_.IsCleared();\n"
          "}\n");
      } else {
        printer->Print(
            vars,
            "$inline$"
            "bool $classname$::has_$name$() const {\n"
            "  return this != internal_default_instance() && $name$_ != NULL;\n"
            "}\n");
      }
    }
  }
}

void MessageGenerator::
GenerateOneofHasBits(io::Printer* printer, bool is_inline) {
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    std::map<string, string> vars;
    vars["oneof_name"] = descriptor_->oneof_decl(i)->name();
    vars["oneof_index"] = SimpleItoa(descriptor_->oneof_decl(i)->index());
    vars["cap_oneof_name"] =
        ToUpper(descriptor_->oneof_decl(i)->name());
    vars["classname"] = classname_;
    vars["inline"] = (is_inline ? "inline " : "");
    printer->Print(
        vars,
        "$inline$"
        "bool $classname$::has_$oneof_name$() const {\n"
        "  return $oneof_name$_case() != $cap_oneof_name$_NOT_SET;\n"
        "}\n"
        "$inline$"
        "void $classname$::clear_has_$oneof_name$() {\n"
        "  _oneof_case_[$oneof_index$] = $cap_oneof_name$_NOT_SET;\n"
        "}\n");
  }
}

void MessageGenerator::
GenerateOneofMemberHasBits(const FieldDescriptor* field,
                           const std::map<string, string>& vars,
                           io::Printer* printer) {
  // Singular field in a oneof
  // N.B.: Without field presence, we do not use has-bits or generate
  // has_$name$() methods, but oneofs still have set_has_$name$().
  // Oneofs also have has_$name$() but only as a private helper
  // method, so that generated code is slightly cleaner (vs.  comparing
  // _oneof_case_[index] against a constant everywhere).
  printer->Print(vars,
    "$inline$"
    "bool $classname$::has_$name$() const {\n"
    "  return $oneof_name$_case() == k$field_name$;\n"
    "}\n");
  printer->Print(vars,
    "$inline$"
    "void $classname$::set_has_$name$() {\n"
    "  _oneof_case_[$oneof_index$] = k$field_name$;\n"
    "}\n");
}

void MessageGenerator::
GenerateFieldClear(const FieldDescriptor* field,
                   const std::map<string, string>& vars,
                   io::Printer* printer) {
  // Generate clear_$name$() (See GenerateFieldAccessorDeclarations and
  // GenerateDependentFieldAccessorDeclarations, $dependent_classname$ is
  // set by the Generate*Definitions functions.)
  printer->Print(vars,
    "$tmpl$"
    "$inline$"
    "void $dependent_classname$::clear_$name$() {\n");

  printer->Indent();

  if (field->containing_oneof()) {
    // Clear this field only if it is the active field in this oneof,
    // otherwise ignore
    printer->Print(vars,
      "if ($this_message$has_$name$()) {\n");
    printer->Indent();
    field_generators_.get(field)
        .GenerateClearingCode(printer);
    printer->Print(vars,
      "$this_message$clear_has_$oneof_name$();\n");
    printer->Outdent();
    printer->Print("}\n");
  } else {
    field_generators_.get(field)
        .GenerateClearingCode(printer);
    if (HasFieldPresence(descriptor_->file())) {
      if (!field->is_repeated()) {
        printer->Print(vars,
                       "$this_message$clear_has_$name$();\n");
      }
    }
  }

  printer->Outdent();
  printer->Print("}\n");
}

void MessageGenerator::
GenerateFieldAccessorDefinitions(io::Printer* printer, bool is_inline) {
  printer->Print("// $classname$\n\n", "classname", classname_);

  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);

    PrintFieldComment(printer, field);

    std::map<string, string> vars;
    SetCommonFieldVariables(field, &vars, options_);
    vars["inline"] = is_inline ? "inline " : "";
    if (use_dependent_base_ && IsFieldDependent(field)) {
      vars["tmpl"] = "template<class T>\n";
      vars["dependent_classname"] =
          DependentBaseClassTemplateName(descriptor_) + "<T>";
      vars["this_message"] = "reinterpret_cast<T*>(this)->";
      vars["this_const_message"] = "reinterpret_cast<const T*>(this)->";
    } else {
      vars["tmpl"] = "";
      vars["dependent_classname"] = vars["classname"];
      vars["this_message"] = "";
      vars["this_const_message"] = "";
    }

    // Generate has_$name$() or $name$_size().
    if (field->is_repeated()) {
      printer->Print(vars,
        "$inline$"
        "int $classname$::$name$_size() const {\n"
        "  return $name$_.size();\n"
        "}\n");
    } else if (field->containing_oneof()) {
      vars["field_name"] = UnderscoresToCamelCase(field->name(), true);
      vars["oneof_name"] = field->containing_oneof()->name();
      vars["oneof_index"] = SimpleItoa(field->containing_oneof()->index());
      if (!use_dependent_base_ || !IsFieldDependent(field)) {
        GenerateOneofMemberHasBits(field, vars, printer);
      }
    } else {
      // Singular field.
      if (!use_dependent_base_ || !IsFieldDependent(field)) {
        GenerateSingularFieldHasBits(field, vars, printer);
      }
    }

    if (!use_dependent_base_ || !IsFieldDependent(field)) {
      GenerateFieldClear(field, vars, printer);
    }

    // Generate type-specific accessors.
    field_generators_.get(field).GenerateInlineAccessorDefinitions(printer,
                                                                   is_inline);

    printer->Print("\n");
  }

  if (!use_dependent_base_) {
    // Generate has_$name$() and clear_has_$name$() functions for oneofs
    // If we aren't using a dependent base, they can be with the other functions
    // that are #ifdef-guarded.
    GenerateOneofHasBits(printer, is_inline);
  }
}

void MessageGenerator::
GenerateDependentBaseClassDefinition(io::Printer* printer) {
  if (!use_dependent_base_) {
    return;
  }

  std::map<string, string> vars;
  vars["classname"] = DependentBaseClassTemplateName(descriptor_);
  vars["full_name"] = descriptor_->full_name();
  vars["superclass"] = SuperClassName(descriptor_, options_);

  printer->Print(vars,
    "template <class T>\n"
    "class $classname$ : public $superclass$ "
    "/* @@protoc_insertion_point(dep_base_class_definition:$full_name$) */ {\n"
    " public:\n");
  printer->Indent();

  printer->Print(vars,
    "$classname$() {}\n"
    "virtual ~$classname$() {}\n"
    "\n");

  // Generate dependent accessor methods for all fields.
  GenerateDependentFieldAccessorDeclarations(printer);

  printer->Outdent();
  printer->Print("};\n");
}

void MessageGenerator::
GenerateClassDefinition(io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return;
  if (use_dependent_base_) {
    GenerateDependentBaseClassDefinition(printer);
      printer->Print("\n");
  }

  std::map<string, string> vars;
  vars["classname"] = classname_;
  vars["full_name"] = descriptor_->full_name();
  vars["field_count"] = SimpleItoa(descriptor_->field_count());
  vars["oneof_decl_count"] = SimpleItoa(descriptor_->oneof_decl_count());
  if (options_.dllexport_decl.empty()) {
    vars["dllexport"] = "";
  } else {
    vars["dllexport"] = options_.dllexport_decl + " ";
  }
  if (use_dependent_base_) {
    vars["superclass"] =
        DependentBaseClassTemplateName(descriptor_) + "<" + classname_ + ">";
  } else {
    vars["superclass"] = SuperClassName(descriptor_, options_);
  }
  printer->Print(vars,
    "class $dllexport$$classname$ : public $superclass$ "
    "/* @@protoc_insertion_point(class_definition:$full_name$) */ "
    "{\n");
  printer->Annotate("classname", descriptor_);
  if (use_dependent_base_) {
    printer->Print(vars, "  friend class $superclass$;\n");
  }
  printer->Print(" public:\n");
  printer->Indent();

  printer->Print(vars,
    "$classname$();\n"
    "virtual ~$classname$();\n"
    "\n"
    "$classname$(const $classname$& from);\n"
    "\n"
    "inline $classname$& operator=(const $classname$& from) {\n"
    "  CopyFrom(from);\n"
    "  return *this;\n"
    "}\n"
    "\n");

  if (PreserveUnknownFields(descriptor_)) {
    string type = UseUnknownFieldSet(descriptor_->file(), options_)
                      ? "::google::protobuf::UnknownFieldSet"
                      : "::std::string";
    printer->Print(
      "inline const $type$& unknown_fields() const {\n"
      "  return _internal_metadata_.unknown_fields();\n"
      "}\n"
      "\n"
      "inline $type$* mutable_unknown_fields() {\n"
      "  return _internal_metadata_.mutable_unknown_fields();\n"
      "}\n"
      "\n",
      "type", type );
  }

  // N.B.: We exclude GetArena() when arena support is disabled, falling back on
  // MessageLite's implementation which returns NULL rather than generating our
  // own method which returns NULL, in order to reduce code size.
  if (SupportsArenas(descriptor_)) {
    // virtual method version of GetArenaNoVirtual(), required for generic dispatch given a
    // MessageLite* (e.g., in RepeatedField::AddAllocated()).
    printer->Print(
        "inline ::google::protobuf::Arena* GetArena() const PROTOBUF_FINAL {\n"
        "  return GetArenaNoVirtual();\n"
        "}\n"
        "inline void* GetMaybeArenaPointer() const PROTOBUF_FINAL {\n"
        "  return MaybeArenaPtr();\n"
        "}\n");
  }

  // Only generate this member if it's not disabled.
  if (HasDescriptorMethods(descriptor_->file(), options_) &&
      !descriptor_->options().no_standard_descriptor_accessor()) {
    printer->Print(vars,
      "static const ::google::protobuf::Descriptor* descriptor();\n");
  }

  printer->Print(vars,
    "static const $classname$& default_instance();\n"
    "\n");

  // Generate enum values for every field in oneofs. One list is generated for
  // each oneof with an additional *_NOT_SET value.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "enum $camel_oneof_name$Case {\n",
        "camel_oneof_name",
        UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true));
    printer->Indent();
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      printer->Print(
          "k$field_name$ = $field_number$,\n",
          "field_name",
          UnderscoresToCamelCase(
              descriptor_->oneof_decl(i)->field(j)->name(), true),
          "field_number",
          SimpleItoa(descriptor_->oneof_decl(i)->field(j)->number()));
    }
    printer->Print(
        "$cap_oneof_name$_NOT_SET = 0,\n",
        "cap_oneof_name",
        ToUpper(descriptor_->oneof_decl(i)->name()));
    printer->Outdent();
    printer->Print(
        "};\n"
        "\n");
  }

  // TODO(gerbens) make this private, while still granting other protos access.
  printer->Print(
      vars,
      "static inline const $classname$* internal_default_instance() {\n"
      "  return reinterpret_cast<const $classname$*>(\n"
      "             &_$classname$_default_instance_);\n"
      "}\n"
      "\n");


  if (SupportsArenas(descriptor_)) {
    printer->Print(vars,
      "void UnsafeArenaSwap($classname$* other);\n");
  }

  if (IsAnyMessage(descriptor_)) {
    printer->Print(vars,
      "// implements Any -----------------------------------------------\n"
      "\n"
      "void PackFrom(const ::google::protobuf::Message& message);\n"
      "void PackFrom(const ::google::protobuf::Message& message,\n"
      "              const ::std::string& type_url_prefix);\n"
      "bool UnpackTo(::google::protobuf::Message* message) const;\n"
      "template<typename T> bool Is() const {\n"
      "  return _any_metadata_.Is<T>();\n"
      "}\n"
      "\n");
  }

  vars["new_final"] = " PROTOBUF_FINAL";

  printer->Print(vars,
    "void Swap($classname$* other);\n"
    "\n"
    "// implements Message ----------------------------------------------\n"
    "\n"
    "inline $classname$* New() const$new_final$ { return New(NULL); }\n"
    "\n"
    "$classname$* New(::google::protobuf::Arena* arena) const$new_final$;\n");

  // For instances that derive from Message (rather than MessageLite), some
  // methods are virtual and should be marked as final.
  string use_final = HasDescriptorMethods(descriptor_->file(), options_) ?
      " PROTOBUF_FINAL" : "";

  if (HasGeneratedMethods(descriptor_->file(), options_)) {
    if (HasDescriptorMethods(descriptor_->file(), options_)) {
      printer->Print(vars,
        "void CopyFrom(const ::google::protobuf::Message& from) PROTOBUF_FINAL;\n"
        "void MergeFrom(const ::google::protobuf::Message& from) PROTOBUF_FINAL;\n");
    } else {
      printer->Print(vars,
        "void CheckTypeAndMergeFrom(const ::google::protobuf::MessageLite& from)\n"
        "  PROTOBUF_FINAL;\n");
    }

    vars["clear_final"] = " PROTOBUF_FINAL";
    vars["is_initialized_final"] = " PROTOBUF_FINAL";
    vars["merge_partial_final"] = " PROTOBUF_FINAL";

    printer->Print(
        vars,
        "void CopyFrom(const $classname$& from);\n"
        "void MergeFrom(const $classname$& from);\n"
        "void Clear()$clear_final$;\n"
        "bool IsInitialized() const$is_initialized_final$;\n"
        "\n"
        "size_t ByteSizeLong() const PROTOBUF_FINAL;\n"
        "bool MergePartialFromCodedStream(\n"
        "    ::google::protobuf::io::CodedInputStream* input)$merge_partial_final$;\n"
        "void SerializeWithCachedSizes(\n"
        "    ::google::protobuf::io::CodedOutputStream* output) const PROTOBUF_FINAL;\n");
    // DiscardUnknownFields() is implemented in message.cc using reflections. We
    // need to implement this function in generated code for messages.
    if (!UseUnknownFieldSet(descriptor_->file(), options_)) {
      printer->Print(
        "void DiscardUnknownFields()$final$;\n",
        "final", use_final);
    }
    if (HasFastArraySerialization(descriptor_->file(), options_)) {
      printer->Print(
        "::google::protobuf::uint8* InternalSerializeWithCachedSizesToArray(\n"
        "    bool deterministic, ::google::protobuf::uint8* target) const PROTOBUF_FINAL;\n"
        "::google::protobuf::uint8* SerializeWithCachedSizesToArray(::google::protobuf::uint8* output)\n"
        "    const PROTOBUF_FINAL {\n"
        "  return InternalSerializeWithCachedSizesToArray(false, output);\n"
        "}\n");
    }
  }

  printer->Print(
    "int GetCachedSize() const PROTOBUF_FINAL { return _cached_size_; }\n"
    "private:\n"
    "void SharedCtor();\n"
    "void SharedDtor();\n"
    "void SetCachedSize(int size) const$final$;\n"
    "void InternalSwap($classname$* other);\n",
    "classname", classname_,
    "final", use_final);
  if (SupportsArenas(descriptor_)) {
    printer->Print(
      "protected:\n"
      "explicit $classname$(::google::protobuf::Arena* arena);\n"
      "private:\n"
      "static void ArenaDtor(void* object);\n"
      "inline void RegisterArenaDtor(::google::protobuf::Arena* arena);\n",
      "classname", classname_);
  }

  if (SupportsArenas(descriptor_)) {
    printer->Print(
      "private:\n"
      "inline ::google::protobuf::Arena* GetArenaNoVirtual() const {\n"
      "  return _internal_metadata_.arena();\n"
      "}\n"
      "inline void* MaybeArenaPtr() const {\n"
      "  return _internal_metadata_.raw_arena_ptr();\n"
      "}\n");
  } else {
    printer->Print(
      "private:\n"
      "inline ::google::protobuf::Arena* GetArenaNoVirtual() const {\n"
      "  return NULL;\n"
      "}\n"
      "inline void* MaybeArenaPtr() const {\n"
      "  return NULL;\n"
      "}\n");
  }

  printer->Print(
      "public:\n"
      "\n");

  if (HasDescriptorMethods(descriptor_->file(), options_)) {
    printer->Print(
      "::google::protobuf::Metadata GetMetadata() const PROTOBUF_FINAL;\n"
      "\n");
  } else {
    printer->Print(
      "::std::string GetTypeName() const PROTOBUF_FINAL;\n"
      "\n");
  }

  printer->Print(
    "// nested types ----------------------------------------------------\n"
    "\n");

  // Import all nested message classes into this class's scope with typedefs.
  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
    const Descriptor* nested_type = descriptor_->nested_type(i);
    if (!IsMapEntryMessage(nested_type)) {
      printer->Print("typedef $nested_full_name$ $nested_name$;\n",
                     "nested_name", nested_type->name(),
                     "nested_full_name", ClassName(nested_type, false));
    }
  }

  if (descriptor_->nested_type_count() > 0) {
    printer->Print("\n");
  }

  // Import all nested enums and their values into this class's scope with
  // typedefs and constants.
  for (int i = 0; i < descriptor_->enum_type_count(); i++) {
    enum_generators_[i]->GenerateSymbolImports(printer);
    printer->Print("\n");
  }

  printer->Print(
    "// accessors -------------------------------------------------------\n"
    "\n");

  // Generate accessor methods for all fields.
  GenerateFieldAccessorDeclarations(printer);

  // Declare extension identifiers.
  for (int i = 0; i < descriptor_->extension_count(); i++) {
    extension_generators_[i]->GenerateDeclaration(printer);
  }


  printer->Print(
    "// @@protoc_insertion_point(class_scope:$full_name$)\n",
    "full_name", descriptor_->full_name());

  // Generate private members.
  printer->Outdent();
  printer->Print(" private:\n");
  printer->Indent();


  for (int i = 0; i < descriptor_->field_count(); i++) {
    if (!descriptor_->field(i)->is_repeated()) {
      // set_has_***() generated in all proto1/2 code and in oneofs (only) for
      // messages without true field presence.
      if (HasFieldPresence(descriptor_->file()) ||
          descriptor_->field(i)->containing_oneof()) {
        printer->Print("void set_has_$name$();\n", "name",
                       FieldName(descriptor_->field(i)));
      }
      // clear_has_***() generated only for non-oneof fields
      // in proto1/2.
      if (!descriptor_->field(i)->containing_oneof() &&
          HasFieldPresence(descriptor_->file())) {
        printer->Print("void clear_has_$name$();\n", "name",
                       FieldName(descriptor_->field(i)));
      }
    }
  }
  printer->Print("\n");

  // Generate oneof function declarations
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "inline bool has_$oneof_name$() const;\n"
        "void clear_$oneof_name$();\n"
        "inline void clear_has_$oneof_name$();\n\n",
        "oneof_name", descriptor_->oneof_decl(i)->name());
  }

  if (HasGeneratedMethods(descriptor_->file(), options_) &&
      !descriptor_->options().message_set_wire_format() &&
      num_required_fields_ > 1) {
    printer->Print(
        "// helper for ByteSizeLong()\n"
        "size_t RequiredFieldsByteSizeFallback() const;\n\n");
  }

  // Prepare decls for _cached_size_ and _has_bits_.  Their position in the
  // output will be determined later.

  bool need_to_emit_cached_size = true;
  // TODO(kenton):  Make _cached_size_ an atomic<int> when C++ supports it.
  const string cached_size_decl = "mutable int _cached_size_;\n";

  const size_t sizeof_has_bits = HasBitsSize();
  const string has_bits_decl = sizeof_has_bits == 0 ? "" :
      "::google::protobuf::internal::HasBits<" + SimpleItoa(sizeof_has_bits / 4) +
      "> _has_bits_;\n";

  // To minimize padding, data members are divided into three sections:
  // (1) members assumed to align to 8 bytes
  // (2) members corresponding to message fields, re-ordered to optimize
  //     alignment.
  // (3) members assumed to align to 4 bytes.

  // Members assumed to align to 8 bytes:

  if (descriptor_->extension_range_count() > 0) {
    printer->Print(
      "::google::protobuf::internal::ExtensionSet _extensions_;\n"
      "\n");
  }

  if (UseUnknownFieldSet(descriptor_->file(), options_)) {
    printer->Print(
      "::google::protobuf::internal::InternalMetadataWithArena _internal_metadata_;\n");
  } else {
    printer->Print(
        "::google::protobuf::internal::InternalMetadataWithArenaLite "
        "_internal_metadata_;\n");
  }

  if (SupportsArenas(descriptor_)) {
    printer->Print(
      "friend class ::google::protobuf::Arena;\n"
      "typedef void InternalArenaConstructable_;\n"
      "typedef void DestructorSkippable_;\n");
  }

  if (HasFieldPresence(descriptor_->file())) {
    // _has_bits_ is frequently accessed, so to reduce code size and improve
    // speed, it should be close to the start of the object.  But, try not to
    // waste space:_has_bits_ by itself always makes sense if its size is a
    // multiple of 8, but, otherwise, maybe _has_bits_ and cached_size_ together
    // will work well.
    printer->Print(has_bits_decl.c_str());
    if ((sizeof_has_bits % 8) != 0) {
      printer->Print(cached_size_decl.c_str());
      need_to_emit_cached_size = false;
    }
  }

  // Field members:

  // Emit some private and static members
  for (int i = 0; i < optimized_order_.size(); ++i) {
    const FieldDescriptor* field = optimized_order_[i];
    const FieldGenerator& generator = field_generators_.get(field);
    generator.GenerateStaticMembers(printer);
    generator.GeneratePrivateMembers(printer);
  }

  // For each oneof generate a union
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "union $camel_oneof_name$Union {\n"
        // explicit empty constructor is needed when union contains
        // ArenaStringPtr members for string fields.
        "  $camel_oneof_name$Union() {}\n",
        "camel_oneof_name",
        UnderscoresToCamelCase(descriptor_->oneof_decl(i)->name(), true));
    printer->Indent();
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      field_generators_.get(descriptor_->oneof_decl(i)->
                            field(j)).GeneratePrivateMembers(printer);
    }
    printer->Outdent();
    printer->Print(
        "} $oneof_name$_;\n",
        "oneof_name", descriptor_->oneof_decl(i)->name());
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      field_generators_.get(descriptor_->oneof_decl(i)->
                            field(j)).GenerateStaticMembers(printer);
    }
  }

  // Members assumed to align to 4 bytes:

  if (need_to_emit_cached_size) {
    printer->Print(cached_size_decl.c_str());
    need_to_emit_cached_size = false;
  }

  // Generate _oneof_case_.
  if (descriptor_->oneof_decl_count() > 0) {
    printer->Print(vars,
      "::google::protobuf::uint32 _oneof_case_[$oneof_decl_count$];\n"
      "\n");
  }

  // Generate _any_metadata_ for the Any type.
  if (IsAnyMessage(descriptor_)) {
    printer->Print(vars,
      "::google::protobuf::internal::AnyMetadata _any_metadata_;\n");
  }

  // Declare AddDescriptors(), BuildDescriptors(), and ShutdownFile() as
  // friends so that they can access private static variables like
  // default_instance_ and reflection_.
  printer->Print("friend void $dllexport_decl$ $initdefaultsname$_impl();\n",
                 // Vars.
                 "dllexport_decl", options_.dllexport_decl, "initdefaultsname",
                 GlobalInitDefaultsName(descriptor_->file()->name()));
  printer->Print("friend void $dllexport_decl$ $adddescriptorsname$_impl();\n",
                 // Vars.
                 "dllexport_decl", options_.dllexport_decl,
                 "adddescriptorsname",
                 GlobalAddDescriptorsName(descriptor_->file()->name()));

  printer->Print(
      "friend const ::google::protobuf::uint32* $offsetfunname$();\n"
      "friend void $shutdownfilename$();\n"
      "\n",
      "offsetfunname", GlobalOffsetTableName(descriptor_->file()->name()),
      "shutdownfilename", GlobalShutdownFileName(descriptor_->file()->name()));

  printer->Outdent();
  printer->Print("};");
  GOOGLE_DCHECK(!need_to_emit_cached_size);
}

void MessageGenerator::
GenerateDependentInlineMethods(io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return;
  for (int i = 0; i < descriptor_->field_count(); i++) {
    if (descriptor_->field(i)->options().weak()) {
      field_generators_.get(descriptor_->field(i))
          .GenerateDependentInlineAccessorDefinitions(printer);
    }
  }
  GenerateDependentFieldAccessorDefinitions(printer);
}

void MessageGenerator::
GenerateInlineMethods(io::Printer* printer, bool is_inline) {
  if (IsMapEntryMessage(descriptor_)) return;
  GenerateFieldAccessorDefinitions(printer, is_inline);

  // Generate oneof_case() functions.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    std::map<string, string> vars;
    vars["class_name"] = classname_;
    vars["camel_oneof_name"] = UnderscoresToCamelCase(
        descriptor_->oneof_decl(i)->name(), true);
    vars["oneof_name"] = descriptor_->oneof_decl(i)->name();
    vars["oneof_index"] = SimpleItoa(descriptor_->oneof_decl(i)->index());
    vars["inline"] = is_inline ? "inline " : "";
    printer->Print(
        vars,
        "$inline$"
        "$class_name$::$camel_oneof_name$Case $class_name$::"
        "$oneof_name$_case() const {\n"
        "  return $class_name$::$camel_oneof_name$Case("
        "_oneof_case_[$oneof_index$]);\n"
        "}\n");
  }
}

void MessageGenerator::
GenerateDescriptorDeclarations(io::Printer* printer) {
  // Generate oneof default instance for reflection usage.
  if (descriptor_->oneof_decl_count() > 0) {
    printer->Print("struct $name$OneofInstance {\n",
                   "name", classname_);
    for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
      for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
        const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
        printer->Print("  ");
        if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE ||
            (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING &&
             EffectiveStringCType(field) != FieldOptions::STRING)) {
          printer->Print("const ");
        }
        field_generators_.get(field).GeneratePrivateMembers(printer);
      }
    }

    printer->Print("} $name$_default_oneof_instance_;\n", "name", classname_);
  }
}

void MessageGenerator::GenerateSchema(io::Printer* printer, int offset,
                                      int has_offset) {
  if (IsMapEntryMessage(descriptor_)) return;

  std::map<string, string> vars;

  vars["classname"] = classname_;
  vars["offset"] = SimpleItoa(offset);
  vars["has_bits_offsets"] = HasFieldPresence(descriptor_->file())
                                 ? SimpleItoa(offset + has_offset)
                                 : "-1";

  printer->Print(vars,
                 "{ $offset$, $has_bits_offsets$, sizeof($classname$)},\n");
}

void MessageGenerator::
GenerateTypeRegistrations(io::Printer* printer) {
  // Register this message type with the message factory.
  if (IsMapEntryMessage(descriptor_)) {
    std::map<string, string> vars;
    CollectMapInfo(descriptor_, &vars);
    vars["classname"] = classname_;

    const FieldDescriptor* val = descriptor_->FindFieldByName("value");
    if (descriptor_->file()->syntax() == FileDescriptor::SYNTAX_PROTO2 &&
        val->type() == FieldDescriptor::TYPE_ENUM) {
      const EnumValueDescriptor* default_value = val->default_value_enum();
      vars["default_enum_value"] = Int32ToString(default_value->number());
    } else {
      vars["default_enum_value"] = "0";
    }

    vars["index_in_metadata"] = SimpleItoa(index_in_metadata_);

    printer->Print(
        vars,
        "const ::google::protobuf::Descriptor* $classname$_descriptor = "
        "file_level_metadata[$index_in_metadata$].descriptor;\n"
        "::google::protobuf::MessageFactory::InternalRegisterGeneratedMessage(\n"
        "      $classname$_descriptor,\n"
        "      ::google::protobuf::internal::MapEntry<\n"
        "          $key$,\n"
        "          $val$,\n"
        "          $key_wire_type$,\n"
        "          $val_wire_type$,\n"
        "          $default_enum_value$>::CreateDefaultInstance(\n"
        "              $classname$_descriptor));\n");
  }
}

void MessageGenerator::
GenerateDefaultInstanceAllocator(io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return;

  // Construct the default instances of all fields, as they will be used
  // when creating the default instance of the entire message.
  for (int i = 0; i < descriptor_->field_count(); i++) {
    field_generators_.get(descriptor_->field(i))
                     .GenerateDefaultInstanceAllocator(printer);
  }

  // Construct the default instance.  We can't call InitAsDefaultInstance() yet
  // because we need to make sure all default instances that this one might
  // depend on are constructed first.
  printer->Print("_$classname$_default_instance_.DefaultConstruct();\n",
                 "classname", classname_);
}

void MessageGenerator::
GenerateDefaultInstanceInitializer(io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return;

  // The default instance needs all of its embedded message pointers
  // cross-linked to other default instances.  We can't do this initialization
  // in the constructor because some other default instances may not have been
  // constructed yet at that time.
  // TODO(kenton):  Maybe all message fields (even for non-default messages)
  //   should be initialized to point at default instances rather than NULL?
  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);

    if (!field->is_repeated() &&
        field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
        (field->containing_oneof() == NULL ||
         HasDescriptorMethods(descriptor_->file(), options_))) {
      string name;
      if (field->containing_oneof()) {
        name = classname_ + "_default_oneof_instance_.";
      } else {
        name = "_" + classname_ + "_default_instance_.get_mutable()->";
      }
      name += FieldName(field);
      printer->Print(
          "$name$_ = const_cast< $type$*>(\n"
          "    $type$::internal_default_instance());\n",
          // Vars.
          "name", name, "type", FieldMessageTypeName(field));
    } else if (field->containing_oneof() &&
               HasDescriptorMethods(descriptor_->file(), options_)) {
      field_generators_.get(descriptor_->field(i))
          .GenerateConstructorCode(printer);
    }
  }
}

void MessageGenerator::
GenerateShutdownCode(io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return;

  printer->Print("_$classname$_default_instance_.Shutdown();\n", "classname",
                 classname_);

  if (HasDescriptorMethods(descriptor_->file(), options_)) {
    printer->Print("delete file_level_metadata[$index$].reflection;\n", "index",
                   SimpleItoa(index_in_metadata_));
  }

  // Handle default instances of fields.
  for (int i = 0; i < descriptor_->field_count(); i++) {
    field_generators_.get(descriptor_->field(i))
                     .GenerateShutdownCode(printer);
  }
}

void MessageGenerator::
GenerateClassMethods(io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return;

  if (IsAnyMessage(descriptor_)) {
    printer->Print(
      "void $classname$::PackFrom(const ::google::protobuf::Message& message) {\n"
      "  _any_metadata_.PackFrom(message);\n"
      "}\n"
      "\n"
      "void $classname$::PackFrom(const ::google::protobuf::Message& message,\n"
      "                           const ::std::string& type_url_prefix) {\n"
      "  _any_metadata_.PackFrom(message, type_url_prefix);\n"
      "}\n"
      "\n"
      "bool $classname$::UnpackTo(::google::protobuf::Message* message) const {\n"
      "  return _any_metadata_.UnpackTo(message);\n"
      "}\n"
      "\n",
      "classname", classname_);
  }

  // Generate non-inline field definitions.
  for (int i = 0; i < descriptor_->field_count(); i++) {
    field_generators_.get(descriptor_->field(i))
                     .GenerateNonInlineAccessorDefinitions(printer);
  }

  // Generate field number constants.
  printer->Print("#if !defined(_MSC_VER) || _MSC_VER >= 1900\n");
  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor *field = descriptor_->field(i);
    printer->Print(
      "const int $classname$::$constant_name$;\n",
      "classname", ClassName(FieldScope(field), false),
      "constant_name", FieldConstantName(field));
  }
  printer->Print(
    "#endif  // !defined(_MSC_VER) || _MSC_VER >= 1900\n"
    "\n");

  GenerateStructors(printer);
  printer->Print("\n");

  if (descriptor_->oneof_decl_count() > 0) {
    GenerateOneofClear(printer);
    printer->Print("\n");
  }

  if (HasGeneratedMethods(descriptor_->file(), options_)) {
    GenerateClear(printer);
    printer->Print("\n");

    GenerateMergeFromCodedStream(printer);
    printer->Print("\n");

    GenerateSerializeWithCachedSizes(printer);
    printer->Print("\n");

    if (HasFastArraySerialization(descriptor_->file(), options_)) {
      GenerateSerializeWithCachedSizesToArray(printer);
      printer->Print("\n");
    }

    GenerateByteSize(printer);
    printer->Print("\n");

    GenerateMergeFrom(printer);
    printer->Print("\n");

    GenerateCopyFrom(printer);
    printer->Print("\n");

    GenerateIsInitialized(printer);
    printer->Print("\n");
  }

  GenerateSwap(printer);
  printer->Print("\n");

  if (HasDescriptorMethods(descriptor_->file(), options_)) {
    printer->Print(
        "::google::protobuf::Metadata $classname$::GetMetadata() const {\n"
        "  protobuf_AssignDescriptorsOnce();\n"
        "  return file_level_metadata[$index$];\n"
        "}\n"
        "\n",
        "classname", classname_, "index", SimpleItoa(index_in_metadata_));
  } else {
    printer->Print(
      "::std::string $classname$::GetTypeName() const {\n"
      "  return \"$type_name$\";\n"
      "}\n"
      "\n",
      "classname", classname_,
      "type_name", descriptor_->full_name());
  }

}

std::pair<size_t, size_t> MessageGenerator::GenerateOffsets(
    io::Printer* printer) {
  if (IsMapEntryMessage(descriptor_)) return std::make_pair(0, 0);
  std::map<string, string> variables;
  variables["classname"] = classname_;

  if (HasFieldPresence(descriptor_->file())) {
    printer->Print(
        variables,
        "GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, _has_bits_),\n");
  } else {
    printer->Print("~0u,  // no _has_bits_\n");
  }
  printer->Print(variables,
                 "GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, "
                 "_internal_metadata_),\n");
  if (descriptor_->extension_range_count() > 0) {
    printer->Print(
        variables,
        "GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, _extensions_),\n");
  } else {
    printer->Print("~0u,  // no _extensions_\n");
  }
  if (descriptor_->oneof_decl_count() > 0) {
    printer->Print(variables,
                   "GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, "
                   "_oneof_case_[0]),\n");
  } else {
    printer->Print("~0u,  // no _oneof_case_\n");
  }

  const int kNumGenericOffsets = 4;  // the number of fixed offsets above
  const size_t offsets = kNumGenericOffsets +
                         descriptor_->field_count() +
                         descriptor_->oneof_decl_count();
  size_t entries = offsets;
  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);
    if (field->containing_oneof()) {
      printer->Print(
          "PROTO2_GENERATED_DEFAULT_ONEOF_FIELD_OFFSET("
          "(&$classname$_default_oneof_instance_), $name$_),\n",
          "classname", classname_, "name", FieldName(field));
    } else {
      printer->Print(
          "GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, "
                                                 "$name$_),\n",
          "classname", classname_,
          "name", FieldName(field));
    }
  }

  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    const OneofDescriptor* oneof = descriptor_->oneof_decl(i);
    printer->Print(
      "GOOGLE_PROTOBUF_GENERATED_MESSAGE_FIELD_OFFSET($classname$, $name$_),\n",
      "classname", classname_,
      "name", oneof->name());
  }

  if (HasFieldPresence(descriptor_->file())) {
    entries += has_bit_indices_.size();
    for (int i = 0; i < has_bit_indices_.size(); i++) {
      printer->Print("$index$,\n", "index", SimpleItoa(has_bit_indices_[i]));
    }
  }

  return std::make_pair(entries, offsets);
}

void MessageGenerator::
GenerateSharedConstructorCode(io::Printer* printer) {
  printer->Print(
    "void $classname$::SharedCtor() {\n",
    "classname", classname_);
  printer->Indent();

  bool need_to_clear_cached_size = true;
  // We reproduce the logic used for laying out _cached_sized_ in the class
  // definition, as to initialize it in-order.
  if (HasFieldPresence(descriptor_->file()) &&
      (HasBitsSize() % 8) != 0) {
    printer->Print("_cached_size_ = 0;\n");
    need_to_clear_cached_size = false;
  }

  // TODO(gerbens) Clean this hack, and why do i need a reference to a pointer??
  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
    if (HasDescriptorMethods(descriptor_->file(), options_) &&
        IsMapEntryMessage(descriptor_->nested_type(i))) {
      printer->Print(
          "const ::google::protobuf::Descriptor*& $type$_descriptor = "
          "file_level_metadata[$index$].descriptor;\n",
          "type", ClassName(descriptor_->nested_type(i), false), "index",
          SimpleItoa(nested_generators_[i]->index_in_metadata_));
    }
  }

  std::vector<bool> processed(optimized_order_.size(), false);
  GenerateConstructorBody(printer, processed, false);

  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "clear_has_$oneof_name$();\n",
        "oneof_name", descriptor_->oneof_decl(i)->name());
  }

  if (need_to_clear_cached_size) {
    printer->Print("_cached_size_ = 0;\n");
  }

  printer->Outdent();
  printer->Print("}\n\n");
}

void MessageGenerator::
GenerateSharedDestructorCode(io::Printer* printer) {
  printer->Print(
    "void $classname$::SharedDtor() {\n",
    "classname", classname_);
  printer->Indent();
  if (SupportsArenas(descriptor_)) {
    // Do nothing when the message is allocated in an arena.
    printer->Print(
      "::google::protobuf::Arena* arena = GetArenaNoVirtual();\n"
      "if (arena != NULL) {\n"
      "  return;\n"
      "}\n"
      "\n");
  }

  // Write the destructors for each field except oneof members.
  // optimized_order_ does not contain oneof fields.
  for (int i = 0; i < optimized_order_.size(); i++) {
    const FieldDescriptor* field = optimized_order_[i];
    field_generators_.get(field).GenerateDestructorCode(printer);
  }

  // Generate code to destruct oneofs. Clearing should do the work.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "if (has_$oneof_name$()) {\n"
        "  clear_$oneof_name$();\n"
        "}\n",
        "oneof_name", descriptor_->oneof_decl(i)->name());
  }

  printer->Outdent();
  printer->Print(
    "}\n"
    "\n");
}

void MessageGenerator::
GenerateArenaDestructorCode(io::Printer* printer) {
  // Generate the ArenaDtor() method. Track whether any fields actually produced
  // code that needs to be called.
  printer->Print(
      "void $classname$::ArenaDtor(void* object) {\n",
      "classname", classname_);
  printer->Indent();

  // This code is placed inside a static method, rather than an ordinary one,
  // since that simplifies Arena's destructor list (ordinary function pointers
  // rather than member function pointers). _this is the object being
  // destructed.
  printer->Print(
      "$classname$* _this = reinterpret_cast< $classname$* >(object);\n"
      // avoid an "unused variable" warning in case no fields have dtor code.
      "(void)_this;\n",
      "classname", classname_);

  bool need_registration = false;
  // Process non-oneof fields first.
  for (int i = 0; i < optimized_order_.size(); i++) {
    const FieldDescriptor* field = optimized_order_[i];
    if (field_generators_.get(field)
                         .GenerateArenaDestructorCode(printer)) {
      need_registration = true;
    }
  }

  // Process oneof fields.
  //
  // Note:  As of 10/5/2016, GenerateArenaDestructorCode does not emit anything
  // and returns false for oneof fields.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    const OneofDescriptor* oneof = descriptor_->oneof_decl(i);

    for (int j = 0; j < oneof->field_count(); j++) {
      const FieldDescriptor* field = oneof->field(j);
      if (field_generators_.get(field)
                           .GenerateArenaDestructorCode(printer)) {
        need_registration = true;
      }
    }
  }

  printer->Outdent();
  printer->Print(
      "}\n");

  if (need_registration) {
    printer->Print(
        "inline void $classname$::RegisterArenaDtor(::google::protobuf::Arena* arena) {\n"
        "  if (arena != NULL) {\n"
        "    arena->OwnCustomDestructor(this, &$classname$::ArenaDtor);\n"
        "  }\n"
        "}\n",
        "classname", classname_);
  } else {
    printer->Print(
        "void $classname$::RegisterArenaDtor(::google::protobuf::Arena* arena) {\n"
        "}\n",
        "classname", classname_);
  }
}

void MessageGenerator::GenerateConstructorBody(io::Printer* printer,
                                               std::vector<bool> processed,
                                               bool copy_constructor) const {
  const FieldDescriptor* last_start = NULL;
  // RunMap maps from fields that start each run to the number of fields in that
  // run.  This is optimized for the common case that there are very few runs in
  // a message and that most of the eligible fields appear together.
  typedef hash_map<const FieldDescriptor*, size_t> RunMap;
  RunMap runs;

  for (int i = 0; i < optimized_order_.size(); ++i) {
    const FieldDescriptor* field = optimized_order_[i];
    if ((copy_constructor && IsPOD(field)) ||
        (!copy_constructor && CanConstructByZeroing(field, options_))) {
      if (last_start == NULL) {
        last_start = field;
      }

      runs[last_start]++;
    } else {
      last_start = NULL;
    }
  }

  string pod_template;
  if (copy_constructor) {
    pod_template =
        "::memcpy(&$first$_, &from.$first$_,\n"
        "  reinterpret_cast<char*>(&$last$_) -\n"
        "  reinterpret_cast<char*>(&$first$_) + sizeof($last$_));\n";
  } else {
    pod_template =
        "::memset(&$first$_, 0, reinterpret_cast<char*>(&$last$_) -\n"
        "  reinterpret_cast<char*>(&$first$_) + sizeof($last$_));\n";
  }

  for (int i = 0; i < optimized_order_.size(); ++i) {
    if (processed[i]) {
      continue;
    }

    const FieldDescriptor* field = optimized_order_[i];
    RunMap::const_iterator it = runs.find(field);

    // We only apply the memset technique to runs of more than one field, as
    // assignment is better than memset for generated code clarity.
    if (it != runs.end() && it->second > 1) {
      // Use a memset, then skip run_length fields.
      const size_t run_length = it->second;
      const string first_field_name = FieldName(field);
      const string last_field_name =
          FieldName(optimized_order_[i + run_length - 1]);

      printer->Print(pod_template.c_str(),
        "first", first_field_name,
        "last", last_field_name);

      i += run_length - 1;
      // ++i at the top of the loop.
    } else {
      if (copy_constructor) {
        field_generators_.get(field).GenerateCopyConstructorCode(printer);
      } else {
        field_generators_.get(field).GenerateConstructorCode(printer);
      }
    }
  }
}

void MessageGenerator::
GenerateStructors(io::Printer* printer) {
  string superclass;
  if (use_dependent_base_) {
    superclass =
        DependentBaseClassTemplateName(descriptor_) + "<" + classname_ + ">";
  } else {
    superclass = SuperClassName(descriptor_, options_);
  }
  string initializer_with_arena = superclass + "()";

  if (descriptor_->extension_range_count() > 0) {
    initializer_with_arena += ",\n  _extensions_(arena)";
  }

  initializer_with_arena += ",\n  _internal_metadata_(arena)";

  // Initialize member variables with arena constructor.
  for (int i = 0; i < optimized_order_.size(); i++) {
    const FieldDescriptor* field = optimized_order_[i];

    bool has_arena_constructor = field->is_repeated();
    if (has_arena_constructor) {
      initializer_with_arena += string(",\n  ") +
          FieldName(field) + string("_(arena)");
    }
  }

  if (IsAnyMessage(descriptor_)) {
    initializer_with_arena += ",\n  _any_metadata_(&type_url_, &value_)";
  }

  string initializer_null;
  initializer_null = ", _internal_metadata_(NULL)";
  if (IsAnyMessage(descriptor_)) {
    initializer_null += ", _any_metadata_(&type_url_, &value_)";
  }

  printer->Print(
      "$classname$::$classname$()\n"
      "  : $superclass$()$initializer$ {\n"
      "  if (GOOGLE_PREDICT_TRUE(this != internal_default_instance())) {\n"
      "    $initdefaultsname$();\n"
      "  }\n"
      "  SharedCtor();\n"
      "  // @@protoc_insertion_point(constructor:$full_name$)\n"
      "}\n",
      "classname", classname_, "superclass", superclass, "full_name",
      descriptor_->full_name(), "initializer", initializer_null,
      "initdefaultsname", GlobalInitDefaultsName(descriptor_->file()->name()));

  if (SupportsArenas(descriptor_)) {
    printer->Print(
        "$classname$::$classname$(::google::protobuf::Arena* arena)\n"
        "  : $initializer$ {\n"
        // When arenas are used it's safe to assume we have finished
        // static init time (protos with arenas are unsafe during static init)
        "#ifdef GOOGLE_PROTOBUF_NO_STATIC_INITIALIZER\n"
        "  $initdefaultsname$();\n"
        "#endif  // GOOGLE_PROTOBUF_NO_STATIC_INITIALIZER\n"
        "  SharedCtor();\n"
        "  RegisterArenaDtor(arena);\n"
        "  // @@protoc_insertion_point(arena_constructor:$full_name$)\n"
        "}\n",
        "initializer", initializer_with_arena, "classname", classname_,
        "superclass", superclass, "full_name", descriptor_->full_name(),
        "initdefaultsname",
        GlobalInitDefaultsName(descriptor_->file()->name()));
  }

  // Generate the copy constructor.
  printer->Print(
    "$classname$::$classname$(const $classname$& from)\n"
    "  : $superclass$()",
    "classname", classname_,
    "superclass", superclass,
    "full_name", descriptor_->full_name());
  printer->Indent();
  printer->Indent();
  printer->Indent();

  printer->Print(
      ",\n_internal_metadata_(NULL)");

  if (HasFieldPresence(descriptor_->file())) {
      printer->Print(",\n_has_bits_(from._has_bits_)");
  }

  bool need_to_emit_cached_size = true;
  const string cached_size_decl = ",\n_cached_size_(0)";
  // We reproduce the logic used for laying out _cached_sized_ in the class
  // definition, as to initialize it in-order.
  if (HasFieldPresence(descriptor_->file()) &&
      (HasBitsSize() % 8) != 0) {
    printer->Print(cached_size_decl.c_str());
    need_to_emit_cached_size = false;
  }

  std::vector<bool> processed(optimized_order_.size(), false);
  for (int i = 0; i < optimized_order_.size(); ++i) {
    const FieldDescriptor* field = optimized_order_[i];

    if (!(field->is_repeated() && !(field->is_map()))
        ) {
      continue;
    }

    processed[i] = true;
    printer->Print(",\n$name$_(from.$name$_)",
                   "name", FieldName(field));
  }

  if (need_to_emit_cached_size) {
    printer->Print(cached_size_decl.c_str());
    need_to_emit_cached_size = false;
  }

  if (IsAnyMessage(descriptor_)) {
    printer->Print(",\n_any_metadata_(&type_url_, &value_)");
  }

  printer->Outdent();
  printer->Outdent();
  printer->Print(" {\n");

  printer->Print(
      "_internal_metadata_.MergeFrom(from._internal_metadata_);\n");

  if (descriptor_->extension_range_count() > 0) {
    printer->Print("_extensions_.MergeFrom(from._extensions_);\n");
  }

  // TODO(gerbens) Clean this hack, and why do i need a reference to a pointer??
  for (int i = 0; i < descriptor_->nested_type_count(); i++) {
    if (HasDescriptorMethods(descriptor_->file(), options_) &&
        IsMapEntryMessage(descriptor_->nested_type(i))) {
      printer->Print(
          "const ::google::protobuf::Descriptor*& $type$_descriptor = "
          "file_level_metadata[$index$].descriptor;\n",
          "type", ClassName(descriptor_->nested_type(i), false), "index",
          SimpleItoa(nested_generators_[i]->index_in_metadata_));
    }
  }

  GenerateConstructorBody(printer, processed, true);

  // Copy oneof fields. Oneof field requires oneof case check.
  for (int i = 0; i < descriptor_->oneof_decl_count(); ++i) {
    printer->Print(
        "clear_has_$oneofname$();\n"
        "switch (from.$oneofname$_case()) {\n",
        "oneofname", descriptor_->oneof_decl(i)->name());
    printer->Indent();
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
      printer->Print(
          "case k$field_name$: {\n",
          "field_name", UnderscoresToCamelCase(field->name(), true));
      printer->Indent();
      field_generators_.get(field).GenerateMergingCode(printer);
      printer->Print(
          "break;\n");
      printer->Outdent();
      printer->Print(
          "}\n");
    }
    printer->Print(
        "case $cap_oneof_name$_NOT_SET: {\n"
        "  break;\n"
        "}\n",
        "oneof_index",
        SimpleItoa(descriptor_->oneof_decl(i)->index()),
        "cap_oneof_name",
        ToUpper(descriptor_->oneof_decl(i)->name()));
    printer->Outdent();
    printer->Print(
        "}\n");
  }

  printer->Outdent();
  printer->Print(
    "  // @@protoc_insertion_point(copy_constructor:$full_name$)\n"
    "}\n"
    "\n",
    "full_name", descriptor_->full_name());

  // Generate the shared constructor code.
  GenerateSharedConstructorCode(printer);

  // Generate the destructor.
  printer->Print(
    "$classname$::~$classname$() {\n"
    "  // @@protoc_insertion_point(destructor:$full_name$)\n"
    "  SharedDtor();\n"
    "}\n"
    "\n",
    "classname", classname_,
    "full_name", descriptor_->full_name());

  // Generate the shared destructor code.
  GenerateSharedDestructorCode(printer);

  // Generate the arena-specific destructor code.
  if (SupportsArenas(descriptor_)) {
    GenerateArenaDestructorCode(printer);
  }

  // Generate SetCachedSize.
  printer->Print(
    "void $classname$::SetCachedSize(int size) const {\n"
    "  GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();\n"
    "  _cached_size_ = size;\n"
    "  GOOGLE_SAFE_CONCURRENT_WRITES_END();\n"
    "}\n",
    "classname", classname_);

  // Only generate this member if it's not disabled.
  if (HasDescriptorMethods(descriptor_->file(), options_) &&
      !descriptor_->options().no_standard_descriptor_accessor()) {
    printer->Print(
        "const ::google::protobuf::Descriptor* $classname$::descriptor() {\n"
        "  protobuf_AssignDescriptorsOnce();\n"
        "  return file_level_metadata[$index$].descriptor;\n"
        "}\n"
        "\n",
        "index", SimpleItoa(index_in_metadata_), "classname", classname_);
  }

  printer->Print(
      "const $classname$& $classname$::default_instance() {\n"
      "  $initdefaultsname$();\n"
      "  return *internal_default_instance();\n"
      "}\n\n",
      "classname", classname_, "initdefaultsname",
      GlobalInitDefaultsName(descriptor_->file()->name()));

  if (SupportsArenas(descriptor_)) {
    printer->Print(
      "$classname$* $classname$::New(::google::protobuf::Arena* arena) const {\n"
      "  return ::google::protobuf::Arena::CreateMessage<$classname$>(arena);\n"
      "}\n",
      "classname", classname_);
  } else {
    printer->Print(
      "$classname$* $classname$::New(::google::protobuf::Arena* arena) const {\n"
      "  $classname$* n = new $classname$;\n"
      "  if (arena != NULL) {\n"
      "    arena->Own(n);\n"
      "  }\n"
      "  return n;\n"
      "}\n",
      "classname", classname_);
  }

}

// Return the number of bits set in n, a non-negative integer.
static int popcnt(uint32 n) {
  int result = 0;
  while (n != 0) {
    result += (n & 1);
    n = n / 2;
  }
  return result;
}

void MessageGenerator::
GenerateClear(io::Printer* printer) {
  printer->Print(
      "void $classname$::Clear() {\n"
      "// @@protoc_insertion_point(message_clear_start:$full_name$)\n",
      "classname", classname_, "full_name", descriptor_->full_name());
  printer->Indent();

  // Step 1: Extensions
  if (descriptor_->extension_range_count() > 0) {
    printer->Print("_extensions_.Clear();\n");
  }

  int last_i = -1;
  for (int i = 0; i < optimized_order_.size(); ) {
    // Detect infinite loops.
    GOOGLE_CHECK_NE(i, last_i);
    last_i = i;

    // Step 2: Repeated fields don't use _has_bits_; emit code to clear them
    // here.
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      const FieldGenerator& generator = field_generators_.get(field);

      if (!field->is_repeated()) {
        break;
      }

      if (use_dependent_base_ && IsFieldDependent(field)) {
        printer->Print("clear_$name$();\n", "name", FieldName(field));
      } else {
        generator.GenerateMessageClearingCode(printer);
      }
    }

    // Step 3: Greedily seek runs of fields that can be cleared by
    // memset-to-0.
    int last_chunk = -1;
    int last_chunk_start = -1;
    int last_chunk_end = -1;
    uint32 last_chunk_mask = 0;

    int memset_run_start = -1;
    int memset_run_end = -1;
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];

      if (!CanInitializeByZeroing(field)) {
        break;
      }

      // "index" defines where in the _has_bits_ the field appears.
      // "i" is our loop counter within optimized_order_.
      int index = HasFieldPresence(descriptor_->file()) ?
          has_bit_indices_[field->index()] : 0;
      int chunk = index / 8;

      if (last_chunk == -1) {
        last_chunk = chunk;
        last_chunk_start = i;
      } else if (chunk != last_chunk) {
        // Emit the fields for this chunk so far.
        break;
      }

      if (memset_run_start == -1) {
        memset_run_start = i;
      }

      memset_run_end = i;
      last_chunk_end = i;
      last_chunk_mask |= static_cast<uint32>(1) << (index % 32);
    }

    // Step 4: Non-repeated, non-zero initializable fields.
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (field->is_repeated() || CanInitializeByZeroing(field)) {
        break;
      }

      // "index" defines where in the _has_bits_ the field appears.
      // "i" is our loop counter within optimized_order_.
      int index = HasFieldPresence(descriptor_->file()) ?
          has_bit_indices_[field->index()] : 0;
      int chunk = index / 8;

      if (last_chunk == -1) {
        last_chunk = chunk;
        last_chunk_start = i;
      } else if (chunk != last_chunk) {
        // Emit the fields for this chunk so far.
        break;
      }

      last_chunk_end = i;
      last_chunk_mask |= static_cast<uint32>(1) << (index % 32);
    }

    if (last_chunk != -1) {
      GOOGLE_DCHECK_NE(-1, last_chunk_start);
      GOOGLE_DCHECK_NE(-1, last_chunk_end);
      GOOGLE_DCHECK_NE(0, last_chunk_mask);

      const int count = popcnt(last_chunk_mask);
      const bool have_outer_if = HasFieldPresence(descriptor_->file()) &&
          (last_chunk_start != last_chunk_end);

      if (have_outer_if) {
        // Check (up to) 8 has_bits at a time if we have more than one field in
        // this chunk.  Due to field layout ordering, we may check
        // _has_bits_[last_chunk * 8 / 32] multiple times.
        GOOGLE_DCHECK_LE(2, count);
        GOOGLE_DCHECK_GE(8, count);

        printer->Print(
          "if (_has_bits_[$index$ / 32] & $mask$u) {\n",
          "index", SimpleItoa(last_chunk * 8),
          "mask", SimpleItoa(last_chunk_mask));
        printer->Indent();
      }

      if (memset_run_start != -1) {
        if (memset_run_start == memset_run_end) {
          // For clarity, do not memset a single field.
          const FieldGenerator& generator =
              field_generators_.get(optimized_order_[memset_run_start]);
          generator.GenerateMessageClearingCode(printer);
        } else {
          const string first_field_name =
              FieldName(optimized_order_[memset_run_start]);
          const string last_field_name =
              FieldName(optimized_order_[memset_run_end]);

          printer->Print(
            "::memset(&$first$_, 0, reinterpret_cast<char*>(&$last$_) -\n"
            "  reinterpret_cast<char*>(&$first$_) + sizeof($last$_));\n",
            "first", first_field_name,
            "last", last_field_name);
        }

        // Advance last_chunk_start to skip over the fields we zeroed/memset.
        last_chunk_start = memset_run_end + 1;
      }

      // Go back and emit clears for each of the fields we processed.
      for (int j = last_chunk_start; j <= last_chunk_end; j++) {
        const FieldDescriptor* field = optimized_order_[j];
        const string fieldname = FieldName(field);
        const FieldGenerator& generator = field_generators_.get(field);

        // It's faster to just overwrite primitive types, but we should only
        // clear strings and messages if they were set.
        //
        // TODO(kenton):  Let the CppFieldGenerator decide this somehow.
        bool should_check_bit =
          field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE ||
          field->cpp_type() == FieldDescriptor::CPPTYPE_STRING;

        bool have_enclosing_if = false;
        if (should_check_bit &&
            // If no field presence, then always clear strings/messages as well.
            HasFieldPresence(descriptor_->file())) {
          printer->Print("if (has_$name$()) {\n", "name", fieldname);
          printer->Indent();
          have_enclosing_if = true;
        }

        generator.GenerateMessageClearingCode(printer);

        if (have_enclosing_if) {
          printer->Outdent();
          printer->Print("}\n");
        }
      }

      if (have_outer_if) {
        printer->Outdent();
        printer->Print("}\n");
      }
    }
  }

  // Step 4: Unions.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "clear_$oneof_name$();\n",
        "oneof_name", descriptor_->oneof_decl(i)->name());
  }

  if (HasFieldPresence(descriptor_->file())) {
    // Step 5: Everything else.
    printer->Print("_has_bits_.Clear();\n");
  }

  if (PreserveUnknownFields(descriptor_)) {
    printer->Print("_internal_metadata_.Clear();\n");
  }

  printer->Outdent();
  printer->Print("}\n");
}

void MessageGenerator::
GenerateOneofClear(io::Printer* printer) {
  // Generated function clears the active field and union case (e.g. foo_case_).
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    std::map<string, string> oneof_vars;
    oneof_vars["classname"] = classname_;
    oneof_vars["oneofname"] = descriptor_->oneof_decl(i)->name();
    oneof_vars["full_name"] = descriptor_->full_name();
    string message_class;

    printer->Print(oneof_vars,
                   "void $classname$::clear_$oneofname$() {\n"
                   "// @@protoc_insertion_point(one_of_clear_start:"
                   "$full_name$)\n");
    printer->Indent();
    printer->Print(oneof_vars,
        "switch ($oneofname$_case()) {\n");
    printer->Indent();
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
      printer->Print(
          "case k$field_name$: {\n",
          "field_name", UnderscoresToCamelCase(field->name(), true));
      printer->Indent();
      // We clear only allocated objects in oneofs
      if (!IsStringOrMessage(field)) {
        printer->Print(
            "// No need to clear\n");
      } else {
        field_generators_.get(field).GenerateClearingCode(printer);
      }
      printer->Print(
          "break;\n");
      printer->Outdent();
      printer->Print(
          "}\n");
    }
    printer->Print(
        "case $cap_oneof_name$_NOT_SET: {\n"
        "  break;\n"
        "}\n",
        "cap_oneof_name",
        ToUpper(descriptor_->oneof_decl(i)->name()));
    printer->Outdent();
    printer->Print(
        "}\n"
        "_oneof_case_[$oneof_index$] = $cap_oneof_name$_NOT_SET;\n",
        "oneof_index", SimpleItoa(i),
        "cap_oneof_name",
        ToUpper(descriptor_->oneof_decl(i)->name()));
    printer->Outdent();
    printer->Print(
        "}\n"
        "\n");
  }
}

void MessageGenerator::
GenerateSwap(io::Printer* printer) {
  if (SupportsArenas(descriptor_)) {
    // Generate the Swap member function. This is a lightweight wrapper around
    // UnsafeArenaSwap() / MergeFrom() with temporaries, depending on the memory
    // ownership situation: swapping across arenas or between an arena and a
    // heap requires copying.
    printer->Print(
        "void $classname$::Swap($classname$* other) {\n"
        "  if (other == this) return;\n"
        "  if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {\n"
        "    InternalSwap(other);\n"
        "  } else {\n"
        "    $classname$* temp = New(GetArenaNoVirtual());\n"
        "    temp->MergeFrom(*other);\n"
        "    other->CopyFrom(*this);\n"
        "    InternalSwap(temp);\n"
        "    if (GetArenaNoVirtual() == NULL) {\n"
        "      delete temp;\n"
        "    }\n"
        "  }\n"
        "}\n"
        "void $classname$::UnsafeArenaSwap($classname$* other) {\n"
        "  if (other == this) return;\n"
        "  GOOGLE_DCHECK(GetArenaNoVirtual() == other->GetArenaNoVirtual());\n"
        "  InternalSwap(other);\n"
        "}\n",
        "classname", classname_);
  } else {
    printer->Print(
        "void $classname$::Swap($classname$* other) {\n"
        "  if (other == this) return;\n"
        "  InternalSwap(other);\n"
        "}\n",
        "classname", classname_);
  }

  // Generate the UnsafeArenaSwap member function.
  printer->Print("void $classname$::InternalSwap($classname$* other) {\n",
                 "classname", classname_);
  printer->Indent();

  if (HasGeneratedMethods(descriptor_->file(), options_)) {
    for (int i = 0; i < optimized_order_.size(); i++) {
      // optimized_order_ does not contain oneof fields, but the field
      // generators for these fields do not emit swapping code on their own.
      const FieldDescriptor* field = optimized_order_[i];
      field_generators_.get(field).GenerateSwappingCode(printer);
    }

    for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
      printer->Print(
        "std::swap($oneof_name$_, other->$oneof_name$_);\n"
        "std::swap(_oneof_case_[$i$], other->_oneof_case_[$i$]);\n",
        "oneof_name", descriptor_->oneof_decl(i)->name(),
        "i", SimpleItoa(i));
    }

    if (HasFieldPresence(descriptor_->file())) {
      for (int i = 0; i < (descriptor_->field_count() + 31) / 32; ++i) {
        printer->Print("std::swap(_has_bits_[$i$], other->_has_bits_[$i$]);\n",
                       "i", SimpleItoa(i));
      }
    }

    if (PreserveUnknownFields(descriptor_)) {
      printer->Print("_internal_metadata_.Swap(&other->_internal_metadata_);\n");
    }

    printer->Print("std::swap(_cached_size_, other->_cached_size_);\n");
    if (descriptor_->extension_range_count() > 0) {
      printer->Print("_extensions_.Swap(&other->_extensions_);\n");
    }
  } else {
    printer->Print("GetReflection()->Swap(this, other);");
  }

  printer->Outdent();
  printer->Print("}\n");
}

void MessageGenerator::
GenerateMergeFrom(io::Printer* printer) {
  if (HasDescriptorMethods(descriptor_->file(), options_)) {
    // Generate the generalized MergeFrom (aka that which takes in the Message
    // base class as a parameter).
    printer->Print(
        "void $classname$::MergeFrom(const ::google::protobuf::Message& from) {\n"
        "// @@protoc_insertion_point(generalized_merge_from_start:"
        "$full_name$)\n"
        "  GOOGLE_DCHECK_NE(&from, this);\n",
        "classname", classname_, "full_name", descriptor_->full_name());
    printer->Indent();

    // Cast the message to the proper type. If we find that the message is
    // *not* of the proper type, we can still call Merge via the reflection
    // system, as the GOOGLE_CHECK above ensured that we have the same descriptor
    // for each message.
    printer->Print(
      "const $classname$* source =\n"
      "    ::google::protobuf::internal::DynamicCastToGenerated<const $classname$>(\n"
      "        &from);\n"
      "if (source == NULL) {\n"
      "// @@protoc_insertion_point(generalized_merge_from_cast_fail:"
      "$full_name$)\n"
      "  ::google::protobuf::internal::ReflectionOps::Merge(from, this);\n"
      "} else {\n"
      "// @@protoc_insertion_point(generalized_merge_from_cast_success:"
      "$full_name$)\n"
      "  MergeFrom(*source);\n"
      "}\n",
      "classname", classname_, "full_name", descriptor_->full_name());

    printer->Outdent();
    printer->Print("}\n\n");
  } else {
    // Generate CheckTypeAndMergeFrom().
    printer->Print(
      "void $classname$::CheckTypeAndMergeFrom(\n"
      "    const ::google::protobuf::MessageLite& from) {\n"
      "  MergeFrom(*::google::protobuf::down_cast<const $classname$*>(&from));\n"
      "}\n"
      "\n",
      "classname", classname_);
  }

  // Generate the class-specific MergeFrom, which avoids the GOOGLE_CHECK and cast.
  printer->Print(
      "void $classname$::MergeFrom(const $classname$& from) {\n"
      "// @@protoc_insertion_point(class_specific_merge_from_start:"
      "$full_name$)\n"
      "  GOOGLE_DCHECK_NE(&from, this);\n",
      "classname", classname_, "full_name", descriptor_->full_name());
  printer->Indent();

  if (descriptor_->extension_range_count() > 0) {
    printer->Print("_extensions_.MergeFrom(from._extensions_);\n");
  }

  printer->Print(
    "_internal_metadata_.MergeFrom(from._internal_metadata_);\n");

  int last_i = -1;
  for (int i = 0; i < optimized_order_.size(); ) {
    // Detect infinite loops.
    GOOGLE_CHECK_NE(i, last_i);
    last_i = i;

    // Merge Repeated fields. These fields do not require a
    // check as we can simply iterate over them.
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (!field->is_repeated()) {
        break;
      }

      const FieldGenerator& generator = field_generators_.get(field);
      generator.GenerateMergingCode(printer);
    }

    // Merge Optional and Required fields (after a _has_bit check).
    int last_chunk = -1;
    int last_chunk_start = -1;
    int last_chunk_end = -1;
    uint32 last_chunk_mask = 0;
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (field->is_repeated()) {
        break;
      }

      // "index" defines where in the _has_bits_ the field appears.
      // "i" is our loop counter within optimized_order_.
      int index = HasFieldPresence(descriptor_->file()) ?
          has_bit_indices_[field->index()] : 0;
      int chunk = index / 8;

      if (last_chunk == -1) {
        last_chunk = chunk;
        last_chunk_start = i;
      } else if (chunk != last_chunk) {
        // Emit the fields for this chunk so far.
        break;
      }

      last_chunk_end = i;
      last_chunk_mask |= static_cast<uint32>(1) << (index % 32);
    }

    if (last_chunk != -1) {
      GOOGLE_DCHECK_NE(-1, last_chunk_start);
      GOOGLE_DCHECK_NE(-1, last_chunk_end);
      GOOGLE_DCHECK_NE(0, last_chunk_mask);

      const int count = popcnt(last_chunk_mask);
      const bool have_outer_if = HasFieldPresence(descriptor_->file()) &&
          (last_chunk_start != last_chunk_end);

      if (have_outer_if) {
        // Check (up to) 8 has_bits at a time if we have more than one field in
        // this chunk.  Due to field layout ordering, we may check
        // _has_bits_[last_chunk * 8 / 32] multiple times.
        GOOGLE_DCHECK_LE(2, count);
        GOOGLE_DCHECK_GE(8, count);

        printer->Print(
          "if (from._has_bits_[$index$ / 32] & $mask$u) {\n",
          "index", SimpleItoa(last_chunk * 8),
          "mask", SimpleItoa(last_chunk_mask));
        printer->Indent();
      }

      // Go back and emit clears for each of the fields we processed.
      for (int j = last_chunk_start; j <= last_chunk_end; j++) {
        const FieldDescriptor* field = optimized_order_[j];
        const FieldGenerator& generator = field_generators_.get(field);

        bool have_enclosing_if = false;
        if (HasFieldPresence(descriptor_->file())) {
          printer->Print(
            "if (from.has_$name$()) {\n",
            "name", FieldName(field));
          printer->Indent();
          have_enclosing_if = true;
        } else {
          // Merge semantics without true field presence: primitive fields are
          // merged only if non-zero (numeric) or non-empty (string).
          have_enclosing_if = EmitFieldNonDefaultCondition(
              printer, "from.", field);
        }

        generator.GenerateMergingCode(printer);

        if (have_enclosing_if) {
          printer->Outdent();
          printer->Print("}\n");
        }
      }

      if (have_outer_if) {
        printer->Outdent();
        printer->Print("}\n");
      }
    }
  }

  // Merge oneof fields. Oneof field requires oneof case check.
  for (int i = 0; i < descriptor_->oneof_decl_count(); ++i) {
    printer->Print(
        "switch (from.$oneofname$_case()) {\n",
        "oneofname", descriptor_->oneof_decl(i)->name());
    printer->Indent();
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
      printer->Print(
          "case k$field_name$: {\n",
          "field_name", UnderscoresToCamelCase(field->name(), true));
      printer->Indent();
      field_generators_.get(field).GenerateMergingCode(printer);
      printer->Print(
          "break;\n");
      printer->Outdent();
      printer->Print(
          "}\n");
    }
    printer->Print(
        "case $cap_oneof_name$_NOT_SET: {\n"
        "  break;\n"
        "}\n",
        "cap_oneof_name",
        ToUpper(descriptor_->oneof_decl(i)->name()));
    printer->Outdent();
    printer->Print(
        "}\n");
  }

  printer->Outdent();
  printer->Print("}\n");
}

void MessageGenerator::
GenerateCopyFrom(io::Printer* printer) {
  if (HasDescriptorMethods(descriptor_->file(), options_)) {
    // Generate the generalized CopyFrom (aka that which takes in the Message
    // base class as a parameter).
    printer->Print(
        "void $classname$::CopyFrom(const ::google::protobuf::Message& from) {\n"
        "// @@protoc_insertion_point(generalized_copy_from_start:"
        "$full_name$)\n",
        "classname", classname_, "full_name", descriptor_->full_name());
    printer->Indent();

    printer->Print(
      "if (&from == this) return;\n"
      "Clear();\n"
      "MergeFrom(from);\n");

    printer->Outdent();
    printer->Print("}\n\n");
  }

  // Generate the class-specific CopyFrom.
  printer->Print(
      "void $classname$::CopyFrom(const $classname$& from) {\n"
      "// @@protoc_insertion_point(class_specific_copy_from_start:"
      "$full_name$)\n",
      "classname", classname_, "full_name", descriptor_->full_name());
  printer->Indent();

  printer->Print(
    "if (&from == this) return;\n"
    "Clear();\n"
    "MergeFrom(from);\n");

  printer->Outdent();
  printer->Print("}\n");
}

void MessageGenerator::
GenerateMergeFromCodedStream(io::Printer* printer) {
  if (descriptor_->options().message_set_wire_format()) {
    // Special-case MessageSet.
    printer->Print(
      "bool $classname$::MergePartialFromCodedStream(\n"
      "    ::google::protobuf::io::CodedInputStream* input) {\n",
      "classname", classname_);

    printer->Print(
        "  return _extensions_.ParseMessageSet(input, "
        "internal_default_instance(),\n"
        "                                      mutable_unknown_fields());\n",
        // Vars.
        "classname", classname_);

    printer->Print(
      "}\n");
    return;
  }

  printer->Print(
    "bool $classname$::MergePartialFromCodedStream(\n"
    "    ::google::protobuf::io::CodedInputStream* input) {\n"
    "#define DO_(EXPRESSION) if (!GOOGLE_PREDICT_TRUE(EXPRESSION)) goto failure\n"
    "  ::google::protobuf::uint32 tag;\n",
    "classname", classname_);

  if (PreserveUnknownFields(descriptor_) &&
      !UseUnknownFieldSet(descriptor_->file(), options_)) {
    // Use LazyStringOutputString to avoid initializing unknown fields string
    // unless it is actually needed. For the same reason, disable eager refresh
    // on the CodedOutputStream.
    printer->Print(
      "  ::google::protobuf::io::LazyStringOutputStream unknown_fields_string(\n"
      "      ::google::protobuf::NewPermanentCallback(&_internal_metadata_,\n"
      "          &::google::protobuf::internal::InternalMetadataWithArenaLite::mutable_unknown_fields));\n"
      "  ::google::protobuf::io::CodedOutputStream unknown_fields_stream(\n"
      "      &unknown_fields_string, false);\n",
      "classname", classname_);
  }

  printer->Print(
    "  // @@protoc_insertion_point(parse_start:$full_name$)\n",
    "full_name", descriptor_->full_name());

  printer->Indent();
  printer->Print("for (;;) {\n");
  printer->Indent();

  std::vector<const FieldDescriptor*> ordered_fields =
      SortFieldsByNumber(descriptor_);
  uint32 maxtag = descriptor_->field_count() == 0 ? 0 :
      WireFormat::MakeTag(ordered_fields[descriptor_->field_count() - 1]);
  const int kCutoff0 = 127;               // fits in 1-byte varint
  const int kCutoff1 = (127 << 7) + 127;  // fits in 2-byte varint

  // We need to capture the last tag when parsing if this is a Group type, as
  // our caller will verify (via CodedInputStream::LastTagWas) that the correct
  // closing tag was received.
  bool capture_last_tag = false;
  const Descriptor* parent = descriptor_->containing_type();
  if (parent) {
    for (int i = 0; i < parent->field_count(); i++) {
      const FieldDescriptor* field = parent->field(i);
      if (field->type() == FieldDescriptor::TYPE_GROUP &&
          field->message_type() == descriptor_) {
        capture_last_tag = true;
        break;
      }
    }
  }

  for (int i = 0; i < descriptor_->file()->extension_count(); i++) {
    const FieldDescriptor* field = descriptor_->file()->extension(i);
    if (field->type() == FieldDescriptor::TYPE_GROUP &&
        field->message_type() == descriptor_) {
      capture_last_tag = true;
      break;
    }
  }

  printer->Print("::std::pair< ::google::protobuf::uint32, bool> p = "
                 "input->ReadTagWithCutoff$lasttag$($max$u);\n"
                 "tag = p.first;\n"
                 "if (!p.second) goto handle_unusual;\n",
                 "max", SimpleItoa(maxtag <= kCutoff0 ? kCutoff0 :
                                   (maxtag <= kCutoff1 ? kCutoff1 :
                                    maxtag)),
                 "lasttag", !capture_last_tag ? "NoLastTag" : "");

  if (descriptor_->field_count() > 0) {
    // We don't even want to print the switch() if we have no fields because
    // MSVC dislikes switch() statements that contain only a default value.

    // Note:  If we just switched on the tag rather than the field number, we
    // could avoid the need for the if() to check the wire type at the beginning
    // of each case.  However, this is actually a bit slower in practice as it
    // creates a jump table that is 8x larger and sparser, and meanwhile the
    // if()s are highly predictable.
    //
    // Historically, we inserted checks to peek at the next tag on the wire and
    // jump directly to the next case statement.  While this avoids the jump
    // table that the switch uses, it greatly increases code size (20-60%) and
    // inserts branches that may fail (especially for real world protos that
    // interleave--in field number order--hot and cold fields).  Loadtests
    // confirmed that removing this optimization is performance neutral.
    printer->Print("switch (::google::protobuf::internal::WireFormatLite::"
                   "GetTagFieldNumber(tag)) {\n");

    printer->Indent();

    // Find repeated messages and groups now, to simplify what follows.
    hash_set<int> fields_with_parse_loop;
    for (int i = 0; i < ordered_fields.size(); i++) {
      const FieldDescriptor* field = ordered_fields[i];
      if (field->is_repeated() &&
          (field->type() == FieldDescriptor::TYPE_MESSAGE ||
           field->type() == FieldDescriptor::TYPE_GROUP)) {
        fields_with_parse_loop.insert(i);
      }
    }

    for (int i = 0; i < ordered_fields.size(); i++) {
      const FieldDescriptor* field = ordered_fields[i];
      const bool loops = fields_with_parse_loop.count(i) > 0;

      PrintFieldComment(printer, field);

      printer->Print(
        "case $number$: {\n",
        "number", SimpleItoa(field->number()));
      printer->Indent();
      const FieldGenerator& field_generator = field_generators_.get(field);

      // Emit code to parse the common, expected case.
      printer->Print("if (tag == $commontag$u) {\n",
                     "commontag", SimpleItoa(WireFormat::MakeTag(field)));

      if (loops) {
        printer->Print("  DO_(input->IncrementRecursionDepth());\n");
      }

      printer->Indent();
      if (field->is_packed()) {
        field_generator.GenerateMergeFromCodedStreamWithPacking(printer);
      } else {
        field_generator.GenerateMergeFromCodedStream(printer);
      }
      printer->Outdent();

      // Emit code to parse unexpectedly packed or unpacked values.
      if (field->is_packed()) {
        internal::WireFormatLite::WireType wiretype =
            WireFormat::WireTypeForFieldType(field->type());
        printer->Print("} else if (tag == $uncommontag$u) {\n",
                       "uncommontag", SimpleItoa(
                           internal::WireFormatLite::MakeTag(
                               field->number(), wiretype)));
        printer->Indent();
        field_generator.GenerateMergeFromCodedStream(printer);
        printer->Outdent();
      } else if (field->is_packable() && !field->is_packed()) {
        internal::WireFormatLite::WireType wiretype =
            internal::WireFormatLite::WIRETYPE_LENGTH_DELIMITED;
        printer->Print("} else if (tag == $uncommontag$u) {\n",
                       "uncommontag", SimpleItoa(
                           internal::WireFormatLite::MakeTag(
                               field->number(), wiretype)));
        printer->Indent();
        field_generator.GenerateMergeFromCodedStreamWithPacking(printer);
        printer->Outdent();
      }

      printer->Print(
        "} else {\n"
        "  goto handle_unusual;\n"
        "}\n");

      // For repeated messages/groups, we need to decrement recursion depth.
      if (loops) {
        printer->Print(
            "input->UnsafeDecrementRecursionDepth();\n");
      }

      printer->Print(
        "break;\n");

      printer->Outdent();
      printer->Print("}\n\n");
    }

    printer->Print("default: {\n");
    printer->Indent();
  }

  printer->Outdent();
  printer->Print("handle_unusual:\n");
  printer->Indent();
  // If tag is 0 or an end-group tag then this must be the end of the message.
  printer->Print(
    "if (tag == 0 ||\n"
    "    ::google::protobuf::internal::WireFormatLite::GetTagWireType(tag) ==\n"
    "    ::google::protobuf::internal::WireFormatLite::WIRETYPE_END_GROUP) {\n"
    "  goto success;\n"
    "}\n");

  // Handle extension ranges.
  if (descriptor_->extension_range_count() > 0) {
    printer->Print(
      "if (");
    for (int i = 0; i < descriptor_->extension_range_count(); i++) {
      const Descriptor::ExtensionRange* range =
        descriptor_->extension_range(i);
      if (i > 0) printer->Print(" ||\n    ");

      uint32 start_tag = WireFormatLite::MakeTag(
        range->start, static_cast<WireFormatLite::WireType>(0));
      uint32 end_tag = WireFormatLite::MakeTag(
        range->end, static_cast<WireFormatLite::WireType>(0));

      if (range->end > FieldDescriptor::kMaxNumber) {
        printer->Print(
          "($start$u <= tag)",
          "start", SimpleItoa(start_tag));
      } else {
        printer->Print(
          "($start$u <= tag && tag < $end$u)",
          "start", SimpleItoa(start_tag),
          "end", SimpleItoa(end_tag));
      }
    }
    printer->Print(") {\n");
    if (PreserveUnknownFields(descriptor_)) {
      if (UseUnknownFieldSet(descriptor_->file(), options_)) {
        printer->Print(
            "  DO_(_extensions_.ParseField(tag, input, "
            "internal_default_instance(),\n"
            "                              mutable_unknown_fields()));\n");
      } else {
        printer->Print(
            "  DO_(_extensions_.ParseField(tag, input, "
            "internal_default_instance(),\n"
            "                              &unknown_fields_stream));\n");
      }
    } else {
      printer->Print(
          // With static initializers.
          "  DO_(_extensions_.ParseField(tag, input, "
          "internal_default_instance());\n");
    }
    printer->Print(
      "  continue;\n"
      "}\n");
  }

  // We really don't recognize this tag.  Skip it.
  if (PreserveUnknownFields(descriptor_)) {
    if (UseUnknownFieldSet(descriptor_->file(), options_)) {
      printer->Print(
        "DO_(::google::protobuf::internal::WireFormat::SkipField(\n"
        "      input, tag, mutable_unknown_fields()));\n");
    } else {
      printer->Print(
        "DO_(::google::protobuf::internal::WireFormatLite::SkipField(\n"
        "    input, tag, &unknown_fields_stream));\n");
    }
  } else {
    printer->Print(
      "DO_(::google::protobuf::internal::WireFormatLite::SkipField(input, tag));\n");
  }

  if (descriptor_->field_count() > 0) {
    printer->Print("break;\n");
    printer->Outdent();
    printer->Print("}\n");    // default:
    printer->Outdent();
    printer->Print("}\n");    // switch
  }

  printer->Outdent();
  printer->Outdent();
  printer->Print(
    "  }\n"                   // for (;;)
    "success:\n"
    "  // @@protoc_insertion_point(parse_success:$full_name$)\n"
    "  return true;\n"
    "failure:\n"
    "  // @@protoc_insertion_point(parse_failure:$full_name$)\n"
    "  return false;\n"
    "#undef DO_\n"
    "}\n", "full_name", descriptor_->full_name());
}

void MessageGenerator::GenerateSerializeOneofFields(
    io::Printer* printer, const std::vector<const FieldDescriptor*>& fields,
    bool to_array) {
  GOOGLE_CHECK(!fields.empty());
  if (fields.size() == 1) {
    GenerateSerializeOneField(printer, fields[0], to_array);
    return;
  }
  // We have multiple mutually exclusive choices.  Emit a switch statement.
  const OneofDescriptor* oneof = fields[0]->containing_oneof();
  printer->Print(
    "switch ($oneofname$_case()) {\n",
    "oneofname", oneof->name());
  printer->Indent();
  for (int i = 0; i < fields.size(); i++) {
    const FieldDescriptor* field = fields[i];
    printer->Print(
      "case k$field_name$:\n",
      "field_name", UnderscoresToCamelCase(field->name(), true));
    printer->Indent();
    if (to_array) {
      field_generators_.get(field).GenerateSerializeWithCachedSizesToArray(
          printer);
    } else {
      field_generators_.get(field).GenerateSerializeWithCachedSizes(printer);
    }
    printer->Print(
      "break;\n");
    printer->Outdent();
  }
  printer->Outdent();
  // Doing nothing is an option.
  printer->Print(
    "  default: ;\n"
    "}\n");
}

void MessageGenerator::GenerateSerializeOneField(
    io::Printer* printer, const FieldDescriptor* field, bool to_array) {
  PrintFieldComment(printer, field);

  bool have_enclosing_if = false;
  if (!field->is_repeated() && HasFieldPresence(descriptor_->file())) {
    printer->Print(
      "if (has_$name$()) {\n",
      "name", FieldName(field));
    printer->Indent();
    have_enclosing_if = true;
  } else if (!HasFieldPresence(descriptor_->file())) {
    have_enclosing_if = EmitFieldNonDefaultCondition(printer, "this->", field);
  }

  if (to_array) {
    field_generators_.get(field).GenerateSerializeWithCachedSizesToArray(
        printer);
  } else {
    field_generators_.get(field).GenerateSerializeWithCachedSizes(printer);
  }

  if (have_enclosing_if) {
    printer->Outdent();
    printer->Print("}\n");
  }
  printer->Print("\n");
}

void MessageGenerator::GenerateSerializeOneExtensionRange(
    io::Printer* printer, const Descriptor::ExtensionRange* range,
    bool to_array) {
  std::map<string, string> vars;
  vars["start"] = SimpleItoa(range->start);
  vars["end"] = SimpleItoa(range->end);
  printer->Print(vars,
    "// Extension range [$start$, $end$)\n");
  if (to_array) {
    printer->Print(vars,
      "target = _extensions_.InternalSerializeWithCachedSizesToArray(\n"
      "    $start$, $end$, false, target);\n\n");
  } else {
    printer->Print(vars,
      "_extensions_.SerializeWithCachedSizes(\n"
      "    $start$, $end$, output);\n\n");
  }
}

void MessageGenerator::
GenerateSerializeWithCachedSizes(io::Printer* printer) {
  if (descriptor_->options().message_set_wire_format()) {
    // Special-case MessageSet.
    printer->Print(
      "void $classname$::SerializeWithCachedSizes(\n"
      "    ::google::protobuf::io::CodedOutputStream* output) const {\n"
      "  _extensions_.SerializeMessageSetWithCachedSizes(output);\n",
      "classname", classname_);
    GOOGLE_CHECK(UseUnknownFieldSet(descriptor_->file(), options_));
    printer->Print(
      "  ::google::protobuf::internal::WireFormat::SerializeUnknownMessageSetItems(\n"
      "      unknown_fields(), output);\n");
    printer->Print(
      "}\n");
    return;
  }

  printer->Print(
    "void $classname$::SerializeWithCachedSizes(\n"
    "    ::google::protobuf::io::CodedOutputStream* output) const {\n",
    "classname", classname_);
  printer->Indent();

  printer->Print(
    "// @@protoc_insertion_point(serialize_start:$full_name$)\n",
    "full_name", descriptor_->full_name());

  GenerateSerializeWithCachedSizesBody(printer, false);

  printer->Print(
    "// @@protoc_insertion_point(serialize_end:$full_name$)\n",
    "full_name", descriptor_->full_name());

  printer->Outdent();
  printer->Print(
    "}\n");
}

void MessageGenerator::
GenerateSerializeWithCachedSizesToArray(io::Printer* printer) {
  if (descriptor_->options().message_set_wire_format()) {
    // Special-case MessageSet.
    printer->Print(
      "::google::protobuf::uint8* $classname$::InternalSerializeWithCachedSizesToArray(\n"
      "    bool deterministic, ::google::protobuf::uint8* target) const {\n"
      "  target = _extensions_."
      "InternalSerializeMessageSetWithCachedSizesToArray(\n"
      "               deterministic, target);\n",
      "classname", classname_);
    GOOGLE_CHECK(UseUnknownFieldSet(descriptor_->file(), options_));
    printer->Print(
      "  target = ::google::protobuf::internal::WireFormat::\n"
      "             SerializeUnknownMessageSetItemsToArray(\n"
      "               unknown_fields(), target);\n");
    printer->Print(
      "  return target;\n"
      "}\n");
    return;
  }

  printer->Print(
    "::google::protobuf::uint8* $classname$::InternalSerializeWithCachedSizesToArray(\n"
    "    bool deterministic, ::google::protobuf::uint8* target) const {\n",
    "classname", classname_);
  printer->Indent();

  printer->Print("(void)deterministic; // Unused\n");
  printer->Print(
    "// @@protoc_insertion_point(serialize_to_array_start:$full_name$)\n",
    "full_name", descriptor_->full_name());

  GenerateSerializeWithCachedSizesBody(printer, true);

  printer->Print(
    "// @@protoc_insertion_point(serialize_to_array_end:$full_name$)\n",
    "full_name", descriptor_->full_name());

  printer->Outdent();
  printer->Print(
    "  return target;\n"
    "}\n");
}

void MessageGenerator::
GenerateSerializeWithCachedSizesBody(io::Printer* printer, bool to_array) {
  // If there are multiple fields in a row from the same oneof then we
  // coalesce them and emit a switch statement.  This is more efficient
  // because it lets the C++ compiler know this is a "at most one can happen"
  // situation. If we emitted "if (has_x()) ...; if (has_y()) ..." the C++
  // compiler's emitted code might check has_y() even when has_x() is true.
  class LazySerializerEmitter {
   public:
    LazySerializerEmitter(MessageGenerator* mg, io::Printer* printer,
                          bool to_array)
        : mg_(mg),
          printer_(printer),
          to_array_(to_array),
          eager_(!HasFieldPresence(mg->descriptor_->file())) {}

    ~LazySerializerEmitter() { Flush(); }

    // If conditions allow, try to accumulate a run of fields from the same
    // oneof, and handle them at the next Flush().
    void Emit(const FieldDescriptor* field) {
      if (eager_ || MustFlush(field)) {
        Flush();
      }
      if (field->containing_oneof() == NULL) {
        mg_->GenerateSerializeOneField(printer_, field, to_array_);
      } else {
        v_.push_back(field);
      }
    }

    void Flush() {
      if (!v_.empty()) {
        mg_->GenerateSerializeOneofFields(printer_, v_, to_array_);
        v_.clear();
      }
    }

   private:
    // If we have multiple fields in v_ then they all must be from the same
    // oneof.  Would adding field to v_ break that invariant?
    bool MustFlush(const FieldDescriptor* field) {
      return !v_.empty() &&
             v_[0]->containing_oneof() != field->containing_oneof();
    }

    MessageGenerator* mg_;
    io::Printer* printer_;
    const bool to_array_;
    const bool eager_;
    std::vector<const FieldDescriptor*> v_;
  };

  std::vector<const FieldDescriptor*> ordered_fields =
      SortFieldsByNumber(descriptor_);

  std::vector<const Descriptor::ExtensionRange*> sorted_extensions;
  for (int i = 0; i < descriptor_->extension_range_count(); ++i) {
    sorted_extensions.push_back(descriptor_->extension_range(i));
  }
  std::sort(sorted_extensions.begin(), sorted_extensions.end(),
            ExtensionRangeSorter());

  // Merge the fields and the extension ranges, both sorted by field number.
  {
    LazySerializerEmitter e(this, printer, to_array);
    int i, j;
    for (i = 0, j = 0;
         i < ordered_fields.size() || j < sorted_extensions.size();) {
      if (i == descriptor_->field_count()) {
        e.Flush();
        GenerateSerializeOneExtensionRange(printer,
                                           sorted_extensions[j++],
                                           to_array);
      } else if (j == sorted_extensions.size()) {
        e.Emit(ordered_fields[i++]);
      } else if (ordered_fields[i]->number() < sorted_extensions[j]->start) {
        e.Emit(ordered_fields[i++]);
      } else {
        e.Flush();
        GenerateSerializeOneExtensionRange(printer,
                                           sorted_extensions[j++],
                                           to_array);
      }
    }
  }

  if (PreserveUnknownFields(descriptor_)) {
    if (UseUnknownFieldSet(descriptor_->file(), options_)) {
      printer->Print("if (_internal_metadata_.have_unknown_fields()) {\n");
      printer->Indent();
      if (to_array) {
        printer->Print(
          "target = "
              "::google::protobuf::internal::WireFormat::SerializeUnknownFieldsToArray(\n"
          "    unknown_fields(), target);\n");
      } else {
        printer->Print(
          "::google::protobuf::internal::WireFormat::SerializeUnknownFields(\n"
          "    unknown_fields(), output);\n");
      }
      printer->Outdent();

      printer->Print(
        "}\n");
    } else {
      printer->Print(
        "output->WriteRaw(unknown_fields().data(),\n"
        "                 static_cast<int>(unknown_fields().size()));\n");
    }
  }
}

std::vector<uint32> MessageGenerator::RequiredFieldsBitMask() const {
  const int array_size = HasBitsSize();
  std::vector<uint32> masks(array_size, 0);

  for (int i = 0; i < descriptor_->field_count(); i++) {
    const FieldDescriptor* field = descriptor_->field(i);
    if (!field->is_required()) {
      continue;
    }

    const int has_bit_index = has_bit_indices_[field->index()];
    masks[has_bit_index / 32] |=
        static_cast<uint32>(1) << (has_bit_index % 32);
  }
  return masks;
}

// Create an expression that evaluates to
//  "for all i, (_has_bits_[i] & masks[i]) == masks[i]"
// masks is allowed to be shorter than _has_bits_, but at least one element of
// masks must be non-zero.
static string ConditionalToCheckBitmasks(const std::vector<uint32>& masks) {
  std::vector<string> parts;
  for (int i = 0; i < masks.size(); i++) {
    if (masks[i] == 0) continue;
    string m = StrCat("0x", strings::Hex(masks[i], strings::ZERO_PAD_8));
    // Each xor evaluates to 0 if the expected bits are present.
    parts.push_back(StrCat("((_has_bits_[", i, "] & ", m, ") ^ ", m, ")"));
  }
  GOOGLE_CHECK(!parts.empty());
  // If we have multiple parts, each expected to be 0, then bitwise-or them.
  string result = parts.size() == 1 ? parts[0] :
      StrCat("(", Join(parts, "\n       | "), ")");
  return result + " == 0";
}

void MessageGenerator::
GenerateByteSize(io::Printer* printer) {
  if (descriptor_->options().message_set_wire_format()) {
    // Special-case MessageSet.
    printer->Print(
        "size_t $classname$::ByteSizeLong() const {\n"
        "// @@protoc_insertion_point(message_set_byte_size_start:$full_name$)\n"
        "  size_t total_size = _extensions_.MessageSetByteSize();\n",
        "classname", classname_, "full_name", descriptor_->full_name());
    GOOGLE_CHECK(UseUnknownFieldSet(descriptor_->file(), options_));
    printer->Print(
      "if (_internal_metadata_.have_unknown_fields()) {\n"
      "  total_size += ::google::protobuf::internal::WireFormat::\n"
      "      ComputeUnknownMessageSetItemsSize(unknown_fields());\n"
      "}\n");
    printer->Print(
      "  int cached_size = ::google::protobuf::internal::ToCachedSize(total_size);\n"
      "  GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();\n"
      "  _cached_size_ = cached_size;\n"
      "  GOOGLE_SAFE_CONCURRENT_WRITES_END();\n"
      "  return total_size;\n"
      "}\n");
    return;
  }

  if (num_required_fields_ > 1 && HasFieldPresence(descriptor_->file())) {
    // Emit a function (rarely used, we hope) that handles the required fields
    // by checking for each one individually.
    printer->Print(
        "size_t $classname$::RequiredFieldsByteSizeFallback() const {\n"
        "// @@protoc_insertion_point(required_fields_byte_size_fallback_start:"
        "$full_name$)\n",
        "classname", classname_, "full_name", descriptor_->full_name());
    printer->Indent();
    printer->Print("size_t total_size = 0;\n");
    for (int i = 0; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (field->is_required()) {
        printer->Print("\n"
                       "if (has_$name$()) {\n",
                       "name", FieldName(field));
        printer->Indent();
        PrintFieldComment(printer, field);
        field_generators_.get(field).GenerateByteSize(printer);
        printer->Outdent();
        printer->Print("}\n");
      }
    }
    printer->Print("\n"
                   "return total_size;\n");
    printer->Outdent();
    printer->Print("}\n");
  }

  printer->Print(
      "size_t $classname$::ByteSizeLong() const {\n"
      "// @@protoc_insertion_point(message_byte_size_start:$full_name$)\n",
      "classname", classname_, "full_name", descriptor_->full_name());
  printer->Indent();
  printer->Print(
    "size_t total_size = 0;\n"
    "\n");

  if (descriptor_->extension_range_count() > 0) {
    printer->Print(
      "total_size += _extensions_.ByteSize();\n"
      "\n");
  }

  if (PreserveUnknownFields(descriptor_)) {
    if (UseUnknownFieldSet(descriptor_->file(), options_)) {
      printer->Print(
        "if (_internal_metadata_.have_unknown_fields()) {\n"
        "  total_size +=\n"
        "    ::google::protobuf::internal::WireFormat::ComputeUnknownFieldsSize(\n"
        "      unknown_fields());\n"
        "}\n");
    } else {
      printer->Print(
        "total_size += unknown_fields().size();\n"
        "\n");
    }
  }

  // Handle required fields (if any).  We expect all of them to be
  // present, so emit one conditional that checks for that.  If they are all
  // present then the fast path executes; otherwise the slow path executes.
  if (num_required_fields_ > 1 && HasFieldPresence(descriptor_->file())) {
    // The fast path works if all required fields are present.
    const std::vector<uint32> masks_for_has_bits = RequiredFieldsBitMask();
    printer->Print((string("if (") +
                    ConditionalToCheckBitmasks(masks_for_has_bits) +
                    ") {  // All required fields are present.\n").c_str());
    printer->Indent();
    // Oneof fields cannot be required, so optimized_order_ contains all of the
    // fields that we need to potentially emit.
    for (int i = 0; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (!field->is_required()) continue;
      PrintFieldComment(printer, field);
      field_generators_.get(field).GenerateByteSize(printer);
      printer->Print("\n");
    }
    printer->Outdent();
    printer->Print("} else {\n"  // the slow path
                   "  total_size += RequiredFieldsByteSizeFallback();\n"
                   "}\n");
  } else {
    // num_required_fields_ <= 1: no need to be tricky
    for (int i = 0; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (!field->is_required()) continue;
      PrintFieldComment(printer, field);
      printer->Print("if (has_$name$()) {\n",
                     "name", FieldName(field));
      printer->Indent();
      field_generators_.get(field).GenerateByteSize(printer);
      printer->Outdent();
      printer->Print("}\n");
    }
  }

  int last_i = -1;
  for (int i = 0; i < optimized_order_.size(); ) {
    // Detect infinite loops.
    GOOGLE_CHECK_NE(i, last_i);
    last_i = i;

    // Skip required fields.
    for (; i < optimized_order_.size() &&
         optimized_order_[i]->is_required(); i++) {
    }

    // Handle repeated fields.
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (!field->is_repeated()) {
        break;
      }

      PrintFieldComment(printer, field);
      const FieldGenerator& generator = field_generators_.get(field);
      generator.GenerateByteSize(printer);
      printer->Print("\n");
    }

    // Handle optional (non-repeated/oneof) fields.
    //
    // These are handled in chunks of 8.  The first chunk is
    // the non-requireds-non-repeateds-non-unions-non-extensions in
    //  descriptor_->field(0), descriptor_->field(1), ... descriptor_->field(7),
    // and the second chunk is the same for
    //  descriptor_->field(8), descriptor_->field(9), ...
    //  descriptor_->field(15),
    // etc.
    int last_chunk = -1;
    int last_chunk_start = -1;
    int last_chunk_end = -1;
    uint32 last_chunk_mask = 0;
    for (; i < optimized_order_.size(); i++) {
      const FieldDescriptor* field = optimized_order_[i];
      if (field->is_repeated() || field->is_required()) {
        break;
      }

      // "index" defines where in the _has_bits_ the field appears.
      // "i" is our loop counter within optimized_order_.
      int index = HasFieldPresence(descriptor_->file()) ?
          has_bit_indices_[field->index()] : 0;
      int chunk = index / 8;

      if (last_chunk == -1) {
        last_chunk = chunk;
        last_chunk_start = i;
      } else if (chunk != last_chunk) {
        // Emit the fields for this chunk so far.
        break;
      }

      last_chunk_end = i;
      last_chunk_mask |= static_cast<uint32>(1) << (index % 32);
    }

    if (last_chunk != -1) {
      GOOGLE_DCHECK_NE(-1, last_chunk_start);
      GOOGLE_DCHECK_NE(-1, last_chunk_end);
      GOOGLE_DCHECK_NE(0, last_chunk_mask);

      const int count = popcnt(last_chunk_mask);
      const bool have_outer_if = HasFieldPresence(descriptor_->file()) &&
          (last_chunk_start != last_chunk_end);

      if (have_outer_if) {
        // Check (up to) 8 has_bits at a time if we have more than one field in
        // this chunk.  Due to field layout ordering, we may check
        // _has_bits_[last_chunk * 8 / 32] multiple times.
        GOOGLE_DCHECK_LE(2, count);
        GOOGLE_DCHECK_GE(8, count);

        printer->Print(
          "if (_has_bits_[$index$ / 32] & $mask$u) {\n",
          "index", SimpleItoa(last_chunk * 8),
          "mask", SimpleItoa(last_chunk_mask));
        printer->Indent();
      }

      // Go back and emit checks for each of the fields we processed.
      for (int j = last_chunk_start; j <= last_chunk_end; j++) {
        const FieldDescriptor* field = optimized_order_[j];
        const FieldGenerator& generator = field_generators_.get(field);

        PrintFieldComment(printer, field);

        bool have_enclosing_if = false;
        if (HasFieldPresence(descriptor_->file())) {
          printer->Print(
            "if (has_$name$()) {\n",
            "name", FieldName(field));
          printer->Indent();
          have_enclosing_if = true;
        } else {
          // Without field presence: field is serialized only if it has a
          // non-default value.
          have_enclosing_if = EmitFieldNonDefaultCondition(
              printer, "this->", field);
        }

        generator.GenerateByteSize(printer);

        if (have_enclosing_if) {
          printer->Outdent();
          printer->Print(
            "}\n"
            "\n");
        }
      }

      if (have_outer_if) {
        printer->Outdent();
        printer->Print("}\n");
      }
    }
  }

  // Fields inside a oneof don't use _has_bits_ so we count them in a separate
  // pass.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    printer->Print(
        "switch ($oneofname$_case()) {\n",
        "oneofname", descriptor_->oneof_decl(i)->name());
    printer->Indent();
    for (int j = 0; j < descriptor_->oneof_decl(i)->field_count(); j++) {
      const FieldDescriptor* field = descriptor_->oneof_decl(i)->field(j);
      PrintFieldComment(printer, field);
      printer->Print(
          "case k$field_name$: {\n",
          "field_name", UnderscoresToCamelCase(field->name(), true));
      printer->Indent();
      field_generators_.get(field).GenerateByteSize(printer);
      printer->Print(
          "break;\n");
      printer->Outdent();
      printer->Print(
          "}\n");
    }
    printer->Print(
        "case $cap_oneof_name$_NOT_SET: {\n"
        "  break;\n"
        "}\n",
        "cap_oneof_name",
        ToUpper(descriptor_->oneof_decl(i)->name()));
    printer->Outdent();
    printer->Print(
        "}\n");
  }

  // We update _cached_size_ even though this is a const method.  In theory,
  // this is not thread-compatible, because concurrent writes have undefined
  // results.  In practice, since any concurrent writes will be writing the
  // exact same value, it works on all common processors.  In a future version
  // of C++, _cached_size_ should be made into an atomic<int>.
  printer->Print(
    "int cached_size = ::google::protobuf::internal::ToCachedSize(total_size);\n"
    "GOOGLE_SAFE_CONCURRENT_WRITES_BEGIN();\n"
    "_cached_size_ = cached_size;\n"
    "GOOGLE_SAFE_CONCURRENT_WRITES_END();\n"
    "return total_size;\n");

  printer->Outdent();
  printer->Print("}\n");
}

void MessageGenerator::
GenerateIsInitialized(io::Printer* printer) {
  printer->Print(
    "bool $classname$::IsInitialized() const {\n",
    "classname", classname_);
  printer->Indent();

  if (descriptor_->extension_range_count() > 0) {
    printer->Print(
      "if (!_extensions_.IsInitialized()) {\n"
      "  return false;\n"
      "}\n\n");
  }

  if (HasFieldPresence(descriptor_->file())) {
    // Check that all required fields in this message are set.  We can do this
    // most efficiently by checking 32 "has bits" at a time.
    const std::vector<uint32> masks = RequiredFieldsBitMask();

    for (int i = 0; i < masks.size(); i++) {
      uint32 mask = masks[i];
      if (mask == 0) {
        continue;
      }

      // TODO(ckennelly): Consider doing something similar to ByteSizeLong(),
      // where we check all of the required fields in a single branch (assuming
      // that we aren't going to benefit from early termination).
      printer->Print(
        "if ((_has_bits_[$i$] & 0x$mask$) != 0x$mask$) return false;\n",
        "i", SimpleItoa(i),
        "mask", StrCat(strings::Hex(mask, strings::ZERO_PAD_8)));
    }
  }

  // Now check that all non-oneof embedded messages are initialized.
  for (int i = 0; i < optimized_order_.size(); i++) {
    const FieldDescriptor* field = optimized_order_[i];
    // TODO(ckennelly): Push this down into a generator?
    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
        !ShouldIgnoreRequiredFieldCheck(field, options_) &&
        HasRequiredFields(field->message_type(), options_)) {
      if (field->is_repeated()) {
        printer->Print(
          "if (!::google::protobuf::internal::AllAreInitialized(this->$name$()))"
          " return false;\n",
          "name", FieldName(field));
      } else {
        GOOGLE_CHECK(field->options().weak() || !field->containing_oneof());
        // For weak fields, use the data member (::google::protobuf::Message*) instead
        // of the getter to avoid a link dependency on the weak message type
        // which is only forward declared.
        printer->Print(
            "if (has_$name$()) {\n"
            "  if (!this->$name$_->IsInitialized()) return false;\n"
            "}\n",
          "name", FieldName(field));
      }
    }
  }

  // Go through the oneof fields, emitting a switch if any might have required
  // fields.
  for (int i = 0; i < descriptor_->oneof_decl_count(); i++) {
    const OneofDescriptor* oneof = descriptor_->oneof_decl(i);

    bool has_required_fields = false;
    for (int j = 0; j < oneof->field_count(); j++) {
      const FieldDescriptor* field = oneof->field(j);

      if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
          !ShouldIgnoreRequiredFieldCheck(field, options_) &&
          HasRequiredFields(field->message_type(), options_)) {
        has_required_fields = true;
        break;
      }
    }

    if (!has_required_fields) {
      continue;
    }

    printer->Print(
        "switch ($oneofname$_case()) {\n",
        "oneofname", oneof->name());
    printer->Indent();
    for (int j = 0; j < oneof->field_count(); j++) {
      const FieldDescriptor* field = oneof->field(j);
      printer->Print(
          "case k$field_name$: {\n",
          "field_name", UnderscoresToCamelCase(field->name(), true));
      printer->Indent();

      if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
          !ShouldIgnoreRequiredFieldCheck(field, options_) &&
          HasRequiredFields(field->message_type(), options_)) {
        GOOGLE_CHECK(!(field->options().weak() || !field->containing_oneof()));
        if (field->options().weak()) {
          // For weak fields, use the data member (::google::protobuf::Message*) instead
          // of the getter to avoid a link dependency on the weak message type
          // which is only forward declared.
          printer->Print(
              "if (has_$name$()) {\n"
              "  if (!this->$name$_->IsInitialized()) return false;\n"
              "}\n",
            "name", FieldName(field));
        } else {
          printer->Print(
            "if (has_$name$()) {\n"
            "  if (!this->$name$().IsInitialized()) return false;\n"
            "}\n",
            "name", FieldName(field));
        }
      }

      printer->Print(
          "break;\n");
      printer->Outdent();
      printer->Print(
          "}\n");
    }
    printer->Print(
        "case $cap_oneof_name$_NOT_SET: {\n"
        "  break;\n"
        "}\n",
        "cap_oneof_name",
        ToUpper(oneof->name()));
    printer->Outdent();
    printer->Print(
        "}\n");
  }

  printer->Outdent();
  printer->Print(
    "  return true;\n"
    "}\n");
}


}  // namespace cpp
}  // namespace compiler
}  // namespace protobuf
}  // namespace google