// 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 <google/protobuf/extension_set.h>

#include <tuple>
#include <unordered_map>
#include <utility>
#include <google/protobuf/stubs/common.h>
#include <google/protobuf/extension_set_inl.h>
#include <google/protobuf/parse_context.h>
#include <google/protobuf/io/coded_stream.h>
#include <google/protobuf/io/zero_copy_stream_impl_lite.h>
#include <google/protobuf/message_lite.h>
#include <google/protobuf/metadata_lite.h>
#include <google/protobuf/repeated_field.h>
#include <google/protobuf/stubs/map_util.h>
#include <google/protobuf/stubs/hash.h>

#include <google/protobuf/port_def.inc>

namespace google {
namespace protobuf {
namespace internal {

namespace {

inline WireFormatLite::FieldType real_type(FieldType type) {
  GOOGLE_DCHECK(type > 0 && type <= WireFormatLite::MAX_FIELD_TYPE);
  return static_cast<WireFormatLite::FieldType>(type);
}

inline WireFormatLite::CppType cpp_type(FieldType type) {
  return WireFormatLite::FieldTypeToCppType(real_type(type));
}

inline bool is_packable(WireFormatLite::WireType type) {
  switch (type) {
    case WireFormatLite::WIRETYPE_VARINT:
    case WireFormatLite::WIRETYPE_FIXED64:
    case WireFormatLite::WIRETYPE_FIXED32:
      return true;
    case WireFormatLite::WIRETYPE_LENGTH_DELIMITED:
    case WireFormatLite::WIRETYPE_START_GROUP:
    case WireFormatLite::WIRETYPE_END_GROUP:
      return false;

    // Do not add a default statement. Let the compiler complain when someone
    // adds a new wire type.
  }
  GOOGLE_LOG(FATAL) << "can't reach here.";
  return false;
}

// Registry stuff.
struct ExtensionHasher {
  std::size_t operator()(const std::pair<const MessageLite*, int>& p) const {
    return std::hash<const MessageLite*>{}(p.first) ^
           std::hash<int>{}(p.second);
  }
};

typedef std::unordered_map<std::pair<const MessageLite*, int>, ExtensionInfo,
                           ExtensionHasher>
    ExtensionRegistry;

static const ExtensionRegistry* global_registry = nullptr;

// This function is only called at startup, so there is no need for thread-
// safety.
void Register(const MessageLite* containing_type,
              int number, ExtensionInfo info) {
  static auto local_static_registry = OnShutdownDelete(new ExtensionRegistry);
  global_registry = local_static_registry;
  if (!InsertIfNotPresent(local_static_registry,
                               std::make_pair(containing_type, number), info)) {
    GOOGLE_LOG(FATAL) << "Multiple extension registrations for type \""
               << containing_type->GetTypeName()
               << "\", field number " << number << ".";
  }
}

const ExtensionInfo* FindRegisteredExtension(
    const MessageLite* containing_type, int number) {
  return global_registry == nullptr
             ? nullptr
             : FindOrNull(*global_registry,
                               std::make_pair(containing_type, number));
}

}  // namespace

ExtensionFinder::~ExtensionFinder() {}

bool GeneratedExtensionFinder::Find(int number, ExtensionInfo* output) {
  const ExtensionInfo* extension =
      FindRegisteredExtension(containing_type_, number);
  if (extension == NULL) {
    return false;
  } else {
    *output = *extension;
    return true;
  }
}

void ExtensionSet::RegisterExtension(const MessageLite* containing_type,
                                     int number, FieldType type,
                                     bool is_repeated, bool is_packed) {
  GOOGLE_CHECK_NE(type, WireFormatLite::TYPE_ENUM);
  GOOGLE_CHECK_NE(type, WireFormatLite::TYPE_MESSAGE);
  GOOGLE_CHECK_NE(type, WireFormatLite::TYPE_GROUP);
  ExtensionInfo info(type, is_repeated, is_packed);
  Register(containing_type, number, info);
}

static bool CallNoArgValidityFunc(const void* arg, int number) {
  // Note:  Must use C-style cast here rather than reinterpret_cast because
  //   the C++ standard at one point did not allow casts between function and
  //   data pointers and some compilers enforce this for C++-style casts.  No
  //   compiler enforces it for C-style casts since lots of C-style code has
  //   relied on these kinds of casts for a long time, despite being
  //   technically undefined.  See:
  //     http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_defects.html#195
  // Also note:  Some compilers do not allow function pointers to be "const".
  //   Which makes sense, I suppose, because it's meaningless.
  return ((EnumValidityFunc*)arg)(number);
}

void ExtensionSet::RegisterEnumExtension(const MessageLite* containing_type,
                                         int number, FieldType type,
                                         bool is_repeated, bool is_packed,
                                         EnumValidityFunc* is_valid) {
  GOOGLE_CHECK_EQ(type, WireFormatLite::TYPE_ENUM);
  ExtensionInfo info(type, is_repeated, is_packed);
  info.enum_validity_check.func = CallNoArgValidityFunc;
  // See comment in CallNoArgValidityFunc() about why we use a c-style cast.
  info.enum_validity_check.arg = (void*)is_valid;
  Register(containing_type, number, info);
}

void ExtensionSet::RegisterMessageExtension(const MessageLite* containing_type,
                                            int number, FieldType type,
                                            bool is_repeated, bool is_packed,
                                            const MessageLite* prototype) {
  GOOGLE_CHECK(type == WireFormatLite::TYPE_MESSAGE ||
        type == WireFormatLite::TYPE_GROUP);
  ExtensionInfo info(type, is_repeated, is_packed);
  info.message_info = {prototype};
  Register(containing_type, number, info);
}


// ===================================================================
// Constructors and basic methods.

ExtensionSet::ExtensionSet(Arena* arena)
    : arena_(arena),
      flat_capacity_(0),
      flat_size_(0),
      map_{flat_capacity_ == 0
               ? NULL
               : Arena::CreateArray<KeyValue>(arena_, flat_capacity_)} {}

ExtensionSet::ExtensionSet()
    : arena_(NULL),
      flat_capacity_(0),
      flat_size_(0),
      map_{flat_capacity_ == 0
               ? NULL
               : Arena::CreateArray<KeyValue>(arena_, flat_capacity_)} {}

ExtensionSet::~ExtensionSet() {
  // Deletes all allocated extensions.
  if (arena_ == NULL) {
    ForEach([](int /* number */, Extension& ext) { ext.Free(); });
    if (PROTOBUF_PREDICT_FALSE(is_large())) {
      delete map_.large;
    } else {
      DeleteFlatMap(map_.flat, flat_capacity_);
    }
  }
}

void ExtensionSet::DeleteFlatMap(
    const ExtensionSet::KeyValue* flat, uint16 flat_capacity) {
#ifdef __cpp_sized_deallocation
  // Arena::CreateArray already requires a trivially destructible type, but
  // ensure this constraint is not violated in the future.
  static_assert(std::is_trivially_destructible<KeyValue>::value,
                "CreateArray requires a trivially destructible type");
  // A const-cast is needed, but this is safe as we are about to deallocate the
  // array.
  ::operator delete[](
      const_cast<ExtensionSet::KeyValue*>(flat), sizeof(*flat) * flat_capacity);
#else  // !__cpp_sized_deallocation
  delete[] flat;
#endif  // !__cpp_sized_deallocation
}

// Defined in extension_set_heavy.cc.
// void ExtensionSet::AppendToList(const Descriptor* containing_type,
//                                 const DescriptorPool* pool,
//                                 vector<const FieldDescriptor*>* output) const

bool ExtensionSet::Has(int number) const {
  const Extension* ext = FindOrNull(number);
  if (ext == NULL) return false;
  GOOGLE_DCHECK(!ext->is_repeated);
  return !ext->is_cleared;
}

int ExtensionSet::NumExtensions() const {
  int result = 0;
  ForEach([&result](int /* number */, const Extension& ext) {
    if (!ext.is_cleared) {
      ++result;
    }
  });
  return result;
}

int ExtensionSet::ExtensionSize(int number) const {
  const Extension* ext = FindOrNull(number);
  return ext == NULL ? 0 : ext->GetSize();
}

FieldType ExtensionSet::ExtensionType(int number) const {
  const Extension* ext = FindOrNull(number);
  if (ext == NULL) {
    GOOGLE_LOG(DFATAL) << "Don't lookup extension types if they aren't present (1). ";
    return 0;
  }
  if (ext->is_cleared) {
    GOOGLE_LOG(DFATAL) << "Don't lookup extension types if they aren't present (2). ";
  }
  return ext->type;
}

void ExtensionSet::ClearExtension(int number) {
  Extension* ext = FindOrNull(number);
  if (ext == NULL) return;
  ext->Clear();
}

// ===================================================================
// Field accessors

namespace {

enum {
  REPEATED,
  OPTIONAL
};

}  // namespace

#define GOOGLE_DCHECK_TYPE(EXTENSION, LABEL, CPPTYPE)                             \
  GOOGLE_DCHECK_EQ((EXTENSION).is_repeated ? REPEATED : OPTIONAL, LABEL);         \
  GOOGLE_DCHECK_EQ(cpp_type((EXTENSION).type), WireFormatLite::CPPTYPE_##CPPTYPE)

// -------------------------------------------------------------------
// Primitives

#define PRIMITIVE_ACCESSORS(UPPERCASE, LOWERCASE, CAMELCASE)                   \
                                                                               \
LOWERCASE ExtensionSet::Get##CAMELCASE(int number,                             \
                                       LOWERCASE default_value) const {        \
  const Extension* extension = FindOrNull(number);                             \
  if (extension == NULL || extension->is_cleared) {                            \
    return default_value;                                                      \
  } else {                                                                     \
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, UPPERCASE);                              \
    return extension->LOWERCASE##_value;                                       \
  }                                                                            \
}                                                                              \
                                                                               \
void ExtensionSet::Set##CAMELCASE(int number, FieldType type,                  \
                                  LOWERCASE value,                             \
                                  const FieldDescriptor* descriptor) {         \
  Extension* extension;                                                        \
  if (MaybeNewExtension(number, descriptor, &extension)) {                     \
    extension->type = type;                                                    \
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_##UPPERCASE); \
    extension->is_repeated = false;                                            \
  } else {                                                                     \
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, UPPERCASE);                              \
  }                                                                            \
  extension->is_cleared = false;                                               \
  extension->LOWERCASE##_value = value;                                        \
}                                                                              \
                                                                               \
LOWERCASE ExtensionSet::GetRepeated##CAMELCASE(int number, int index) const {  \
  const Extension* extension = FindOrNull(number);                             \
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";         \
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, UPPERCASE);                                \
  return extension->repeated_##LOWERCASE##_value->Get(index);                  \
}                                                                              \
                                                                               \
void ExtensionSet::SetRepeated##CAMELCASE(                                     \
    int number, int index, LOWERCASE value) {                                  \
  Extension* extension = FindOrNull(number);                                   \
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";         \
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, UPPERCASE);                                \
  extension->repeated_##LOWERCASE##_value->Set(index, value);                  \
}                                                                              \
                                                                               \
void ExtensionSet::Add##CAMELCASE(int number, FieldType type,                  \
                                  bool packed, LOWERCASE value,                \
                                  const FieldDescriptor* descriptor) {         \
  Extension* extension;                                                        \
  if (MaybeNewExtension(number, descriptor, &extension)) {                     \
    extension->type = type;                                                    \
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_##UPPERCASE); \
    extension->is_repeated = true;                                             \
    extension->is_packed = packed;                                             \
    extension->repeated_##LOWERCASE##_value =                                  \
      Arena::CreateMessage<RepeatedField<LOWERCASE> >(arena_);                 \
  } else {                                                                     \
    GOOGLE_DCHECK_TYPE(*extension, REPEATED, UPPERCASE);                              \
    GOOGLE_DCHECK_EQ(extension->is_packed, packed);                                   \
  }                                                                            \
  extension->repeated_##LOWERCASE##_value->Add(value);                         \
}

PRIMITIVE_ACCESSORS( INT32,  int32,  Int32)
PRIMITIVE_ACCESSORS( INT64,  int64,  Int64)
PRIMITIVE_ACCESSORS(UINT32, uint32, UInt32)
PRIMITIVE_ACCESSORS(UINT64, uint64, UInt64)
PRIMITIVE_ACCESSORS( FLOAT,  float,  Float)
PRIMITIVE_ACCESSORS(DOUBLE, double, Double)
PRIMITIVE_ACCESSORS(  BOOL,   bool,   Bool)

#undef PRIMITIVE_ACCESSORS

const void* ExtensionSet::GetRawRepeatedField(int number,
                                              const void* default_value) const {
  const Extension* extension = FindOrNull(number);
  if (extension == NULL) {
    return default_value;
  }
  // We assume that all the RepeatedField<>* pointers have the same
  // size and alignment within the anonymous union in Extension.
  return extension->repeated_int32_value;
}

void* ExtensionSet::MutableRawRepeatedField(int number, FieldType field_type,
                                            bool packed,
                                            const FieldDescriptor* desc) {
  Extension* extension;

  // We instantiate an empty Repeated{,Ptr}Field if one doesn't exist for this
  // extension.
  if (MaybeNewExtension(number, desc, &extension)) {
    extension->is_repeated = true;
    extension->type = field_type;
    extension->is_packed = packed;

    switch (WireFormatLite::FieldTypeToCppType(
        static_cast<WireFormatLite::FieldType>(field_type))) {
      case WireFormatLite::CPPTYPE_INT32:
        extension->repeated_int32_value =
            Arena::CreateMessage<RepeatedField<int32> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_INT64:
        extension->repeated_int64_value =
            Arena::CreateMessage<RepeatedField<int64> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_UINT32:
        extension->repeated_uint32_value =
            Arena::CreateMessage<RepeatedField<uint32> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_UINT64:
        extension->repeated_uint64_value =
            Arena::CreateMessage<RepeatedField<uint64> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_DOUBLE:
        extension->repeated_double_value =
            Arena::CreateMessage<RepeatedField<double> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_FLOAT:
        extension->repeated_float_value =
            Arena::CreateMessage<RepeatedField<float> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_BOOL:
        extension->repeated_bool_value =
            Arena::CreateMessage<RepeatedField<bool> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_ENUM:
        extension->repeated_enum_value =
            Arena::CreateMessage<RepeatedField<int> >(arena_);
        break;
      case WireFormatLite::CPPTYPE_STRING:
        extension->repeated_string_value =
            Arena::CreateMessage<RepeatedPtrField<std::string>>(arena_);
        break;
      case WireFormatLite::CPPTYPE_MESSAGE:
        extension->repeated_message_value =
            Arena::CreateMessage<RepeatedPtrField<MessageLite> >(arena_);
        break;
    }
  }

  // We assume that all the RepeatedField<>* pointers have the same
  // size and alignment within the anonymous union in Extension.
  return extension->repeated_int32_value;
}

// Compatible version using old call signature. Does not create extensions when
// the don't already exist; instead, just GOOGLE_CHECK-fails.
void* ExtensionSet::MutableRawRepeatedField(int number) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Extension not found.";
  // We assume that all the RepeatedField<>* pointers have the same
  // size and alignment within the anonymous union in Extension.
  return extension->repeated_int32_value;
}


// -------------------------------------------------------------------
// Enums

int ExtensionSet::GetEnum(int number, int default_value) const {
  const Extension* extension = FindOrNull(number);
  if (extension == NULL || extension->is_cleared) {
    // Not present.  Return the default value.
    return default_value;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, ENUM);
    return extension->enum_value;
  }
}

void ExtensionSet::SetEnum(int number, FieldType type, int value,
                           const FieldDescriptor* descriptor) {
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_ENUM);
    extension->is_repeated = false;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, ENUM);
  }
  extension->is_cleared = false;
  extension->enum_value = value;
}

int ExtensionSet::GetRepeatedEnum(int number, int index) const {
  const Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, ENUM);
  return extension->repeated_enum_value->Get(index);
}

void ExtensionSet::SetRepeatedEnum(int number, int index, int value) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, ENUM);
  extension->repeated_enum_value->Set(index, value);
}

void ExtensionSet::AddEnum(int number, FieldType type,
                           bool packed, int value,
                           const FieldDescriptor* descriptor) {
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_ENUM);
    extension->is_repeated = true;
    extension->is_packed = packed;
    extension->repeated_enum_value =
        Arena::CreateMessage<RepeatedField<int> >(arena_);
  } else {
    GOOGLE_DCHECK_TYPE(*extension, REPEATED, ENUM);
    GOOGLE_DCHECK_EQ(extension->is_packed, packed);
  }
  extension->repeated_enum_value->Add(value);
}

// -------------------------------------------------------------------
// Strings

const std::string& ExtensionSet::GetString(
    int number, const std::string& default_value) const {
  const Extension* extension = FindOrNull(number);
  if (extension == NULL || extension->is_cleared) {
    // Not present.  Return the default value.
    return default_value;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, STRING);
    return *extension->string_value;
  }
}

std::string* ExtensionSet::MutableString(int number, FieldType type,
                                         const FieldDescriptor* descriptor) {
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_STRING);
    extension->is_repeated = false;
    extension->string_value = Arena::Create<std::string>(arena_);
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, STRING);
  }
  extension->is_cleared = false;
  return extension->string_value;
}

const std::string& ExtensionSet::GetRepeatedString(int number,
                                                   int index) const {
  const Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, STRING);
  return extension->repeated_string_value->Get(index);
}

std::string* ExtensionSet::MutableRepeatedString(int number, int index) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, STRING);
  return extension->repeated_string_value->Mutable(index);
}

std::string* ExtensionSet::AddString(int number, FieldType type,
                                     const FieldDescriptor* descriptor) {
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_STRING);
    extension->is_repeated = true;
    extension->is_packed = false;
    extension->repeated_string_value =
        Arena::CreateMessage<RepeatedPtrField<std::string>>(arena_);
  } else {
    GOOGLE_DCHECK_TYPE(*extension, REPEATED, STRING);
  }
  return extension->repeated_string_value->Add();
}

// -------------------------------------------------------------------
// Messages

const MessageLite& ExtensionSet::GetMessage(
    int number, const MessageLite& default_value) const {
  const Extension* extension = FindOrNull(number);
  if (extension == NULL) {
    // Not present.  Return the default value.
    return default_value;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
    if (extension->is_lazy) {
      return extension->lazymessage_value->GetMessage(default_value);
    } else {
      return *extension->message_value;
    }
  }
}

// Defined in extension_set_heavy.cc.
// const MessageLite& ExtensionSet::GetMessage(int number,
//                                             const Descriptor* message_type,
//                                             MessageFactory* factory) const

MessageLite* ExtensionSet::MutableMessage(int number, FieldType type,
                                          const MessageLite& prototype,
                                          const FieldDescriptor* descriptor) {
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
    extension->is_repeated = false;
    extension->is_lazy = false;
    extension->message_value = prototype.New(arena_);
    extension->is_cleared = false;
    return extension->message_value;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
    extension->is_cleared = false;
    if (extension->is_lazy) {
      return extension->lazymessage_value->MutableMessage(prototype);
    } else {
      return extension->message_value;
    }
  }
}

// Defined in extension_set_heavy.cc.
// MessageLite* ExtensionSet::MutableMessage(int number, FieldType type,
//                                           const Descriptor* message_type,
//                                           MessageFactory* factory)

void ExtensionSet::SetAllocatedMessage(int number, FieldType type,
                                       const FieldDescriptor* descriptor,
                                       MessageLite* message) {
  if (message == NULL) {
    ClearExtension(number);
    return;
  }
  Arena* message_arena = message->GetArena();
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
    extension->is_repeated = false;
    extension->is_lazy = false;
    if (message_arena == arena_) {
      extension->message_value = message;
    } else if (message_arena == NULL) {
      extension->message_value = message;
      arena_->Own(message);  // not NULL because not equal to message_arena
    } else {
      extension->message_value = message->New(arena_);
      extension->message_value->CheckTypeAndMergeFrom(*message);
    }
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
    if (extension->is_lazy) {
      extension->lazymessage_value->SetAllocatedMessage(message);
    } else {
      if (arena_ == NULL) {
        delete extension->message_value;
      }
      if (message_arena == arena_) {
        extension->message_value = message;
      } else if (message_arena == NULL) {
        extension->message_value = message;
        arena_->Own(message);  // not NULL because not equal to message_arena
      } else {
        extension->message_value = message->New(arena_);
        extension->message_value->CheckTypeAndMergeFrom(*message);
      }
    }
  }
  extension->is_cleared = false;
}

void ExtensionSet::UnsafeArenaSetAllocatedMessage(
    int number, FieldType type, const FieldDescriptor* descriptor,
    MessageLite* message) {
  if (message == NULL) {
    ClearExtension(number);
    return;
  }
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
    extension->is_repeated = false;
    extension->is_lazy = false;
    extension->message_value = message;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
    if (extension->is_lazy) {
      extension->lazymessage_value->UnsafeArenaSetAllocatedMessage(message);
    } else {
      if (arena_ == NULL) {
        delete extension->message_value;
      }
      extension->message_value = message;
    }
  }
  extension->is_cleared = false;
}

MessageLite* ExtensionSet::ReleaseMessage(int number,
                                          const MessageLite& prototype) {
  Extension* extension = FindOrNull(number);
  if (extension == NULL) {
    // Not present.  Return NULL.
    return NULL;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
    MessageLite* ret = NULL;
    if (extension->is_lazy) {
      ret = extension->lazymessage_value->ReleaseMessage(prototype);
      if (arena_ == NULL) {
        delete extension->lazymessage_value;
      }
    } else {
      if (arena_ == NULL) {
        ret = extension->message_value;
      } else {
        // ReleaseMessage() always returns a heap-allocated message, and we are
        // on an arena, so we need to make a copy of this message to return.
        ret = extension->message_value->New();
        ret->CheckTypeAndMergeFrom(*extension->message_value);
      }
    }
    Erase(number);
    return ret;
  }
}

MessageLite* ExtensionSet::UnsafeArenaReleaseMessage(
    int number, const MessageLite& prototype) {
  Extension* extension = FindOrNull(number);
  if (extension == NULL) {
    // Not present.  Return NULL.
    return NULL;
  } else {
    GOOGLE_DCHECK_TYPE(*extension, OPTIONAL, MESSAGE);
    MessageLite* ret = NULL;
    if (extension->is_lazy) {
      ret = extension->lazymessage_value->UnsafeArenaReleaseMessage(prototype);
      if (arena_ == NULL) {
        delete extension->lazymessage_value;
      }
    } else {
      ret = extension->message_value;
    }
    Erase(number);
    return ret;
  }
}

// Defined in extension_set_heavy.cc.
// MessageLite* ExtensionSet::ReleaseMessage(const FieldDescriptor* descriptor,
//                                           MessageFactory* factory);

const MessageLite& ExtensionSet::GetRepeatedMessage(
    int number, int index) const {
  const Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, MESSAGE);
  return extension->repeated_message_value->Get(index);
}

MessageLite* ExtensionSet::MutableRepeatedMessage(int number, int index) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK_TYPE(*extension, REPEATED, MESSAGE);
  return extension->repeated_message_value->Mutable(index);
}

MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
                                      const MessageLite& prototype,
                                      const FieldDescriptor* descriptor) {
  Extension* extension;
  if (MaybeNewExtension(number, descriptor, &extension)) {
    extension->type = type;
    GOOGLE_DCHECK_EQ(cpp_type(extension->type), WireFormatLite::CPPTYPE_MESSAGE);
    extension->is_repeated = true;
    extension->repeated_message_value =
        Arena::CreateMessage<RepeatedPtrField<MessageLite> >(arena_);
  } else {
    GOOGLE_DCHECK_TYPE(*extension, REPEATED, MESSAGE);
  }

  // RepeatedPtrField<MessageLite> does not know how to Add() since it cannot
  // allocate an abstract object, so we have to be tricky.
  MessageLite* result = reinterpret_cast<internal::RepeatedPtrFieldBase*>(
                            extension->repeated_message_value)
                            ->AddFromCleared<GenericTypeHandler<MessageLite>>();
  if (result == NULL) {
    result = prototype.New(arena_);
    extension->repeated_message_value->AddAllocated(result);
  }
  return result;
}

// Defined in extension_set_heavy.cc.
// MessageLite* ExtensionSet::AddMessage(int number, FieldType type,
//                                       const Descriptor* message_type,
//                                       MessageFactory* factory)

#undef GOOGLE_DCHECK_TYPE

void ExtensionSet::RemoveLast(int number) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK(extension->is_repeated);

  switch(cpp_type(extension->type)) {
    case WireFormatLite::CPPTYPE_INT32:
      extension->repeated_int32_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_INT64:
      extension->repeated_int64_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_UINT32:
      extension->repeated_uint32_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_UINT64:
      extension->repeated_uint64_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_FLOAT:
      extension->repeated_float_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_DOUBLE:
      extension->repeated_double_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_BOOL:
      extension->repeated_bool_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_ENUM:
      extension->repeated_enum_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_STRING:
      extension->repeated_string_value->RemoveLast();
      break;
    case WireFormatLite::CPPTYPE_MESSAGE:
      extension->repeated_message_value->RemoveLast();
      break;
  }
}

MessageLite* ExtensionSet::ReleaseLast(int number) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK(extension->is_repeated);
  GOOGLE_DCHECK(cpp_type(extension->type) == WireFormatLite::CPPTYPE_MESSAGE);
  return extension->repeated_message_value->ReleaseLast();
}

void ExtensionSet::SwapElements(int number, int index1, int index2) {
  Extension* extension = FindOrNull(number);
  GOOGLE_CHECK(extension != NULL) << "Index out-of-bounds (field is empty).";
  GOOGLE_DCHECK(extension->is_repeated);

  switch(cpp_type(extension->type)) {
    case WireFormatLite::CPPTYPE_INT32:
      extension->repeated_int32_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_INT64:
      extension->repeated_int64_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_UINT32:
      extension->repeated_uint32_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_UINT64:
      extension->repeated_uint64_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_FLOAT:
      extension->repeated_float_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_DOUBLE:
      extension->repeated_double_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_BOOL:
      extension->repeated_bool_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_ENUM:
      extension->repeated_enum_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_STRING:
      extension->repeated_string_value->SwapElements(index1, index2);
      break;
    case WireFormatLite::CPPTYPE_MESSAGE:
      extension->repeated_message_value->SwapElements(index1, index2);
      break;
  }
}

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

void ExtensionSet::Clear() {
  ForEach([](int /* number */, Extension& ext) { ext.Clear(); });
}

namespace {
// Computes the size of a std::set_union without constructing the union.
template <typename ItX, typename ItY>
size_t SizeOfUnion(ItX it_xs, ItX end_xs, ItY it_ys, ItY end_ys) {
  size_t result = 0;
  while (it_xs != end_xs && it_ys != end_ys) {
    ++result;
    if (it_xs->first < it_ys->first) {
      ++it_xs;
    } else if (it_xs->first == it_ys->first) {
      ++it_xs;
      ++it_ys;
    } else {
      ++it_ys;
    }
  }
  result += std::distance(it_xs, end_xs);
  result += std::distance(it_ys, end_ys);
  return result;
}
}  // namespace

void ExtensionSet::MergeFrom(const ExtensionSet& other) {
  if (PROTOBUF_PREDICT_TRUE(!is_large())) {
    if (PROTOBUF_PREDICT_TRUE(!other.is_large())) {
      GrowCapacity(SizeOfUnion(flat_begin(), flat_end(), other.flat_begin(),
                               other.flat_end()));
    } else {
      GrowCapacity(SizeOfUnion(flat_begin(), flat_end(),
                               other.map_.large->begin(),
                               other.map_.large->end()));
    }
  }
  other.ForEach([this](int number, const Extension& ext) {
    this->InternalExtensionMergeFrom(number, ext);
  });
}

void ExtensionSet::InternalExtensionMergeFrom(
  int number, const Extension& other_extension) {
  if (other_extension.is_repeated) {
    Extension* extension;
    bool is_new = MaybeNewExtension(number, other_extension.descriptor,
                                    &extension);
    if (is_new) {
      // Extension did not already exist in set.
      extension->type = other_extension.type;
      extension->is_packed = other_extension.is_packed;
      extension->is_repeated = true;
    } else {
      GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
      GOOGLE_DCHECK_EQ(extension->is_packed, other_extension.is_packed);
      GOOGLE_DCHECK(extension->is_repeated);
    }

    switch (cpp_type(other_extension.type)) {
#define HANDLE_TYPE(UPPERCASE, LOWERCASE, REPEATED_TYPE)                    \
      case WireFormatLite::CPPTYPE_##UPPERCASE:                             \
        if (is_new) {                                                       \
          extension->repeated_##LOWERCASE##_value =                         \
            Arena::CreateMessage<REPEATED_TYPE >(arena_);                   \
        }                                                                   \
        extension->repeated_##LOWERCASE##_value->MergeFrom(                 \
          *other_extension.repeated_##LOWERCASE##_value);                   \
        break;

      HANDLE_TYPE(  INT32,   int32, RepeatedField   <  int32>);
      HANDLE_TYPE(  INT64,   int64, RepeatedField   <  int64>);
      HANDLE_TYPE( UINT32,  uint32, RepeatedField   < uint32>);
      HANDLE_TYPE( UINT64,  uint64, RepeatedField   < uint64>);
      HANDLE_TYPE(  FLOAT,   float, RepeatedField   <  float>);
      HANDLE_TYPE( DOUBLE,  double, RepeatedField   < double>);
      HANDLE_TYPE(   BOOL,    bool, RepeatedField   <   bool>);
      HANDLE_TYPE(   ENUM,    enum, RepeatedField   <    int>);
      HANDLE_TYPE(STRING, string, RepeatedPtrField<std::string>);
#undef HANDLE_TYPE

      case WireFormatLite::CPPTYPE_MESSAGE:
        if (is_new) {
          extension->repeated_message_value =
              Arena::CreateMessage<RepeatedPtrField<MessageLite> >(arena_);
        }
        // We can't call RepeatedPtrField<MessageLite>::MergeFrom() because
        // it would attempt to allocate new objects.
        RepeatedPtrField<MessageLite>* other_repeated_message =
            other_extension.repeated_message_value;
        for (int i = 0; i < other_repeated_message->size(); i++) {
          const MessageLite& other_message = other_repeated_message->Get(i);
          MessageLite* target =
              reinterpret_cast<internal::RepeatedPtrFieldBase*>(
                  extension->repeated_message_value)
                  ->AddFromCleared<GenericTypeHandler<MessageLite>>();
          if (target == NULL) {
            target = other_message.New(arena_);
            extension->repeated_message_value->AddAllocated(target);
          }
          target->CheckTypeAndMergeFrom(other_message);
        }
        break;
    }
  } else {
    if (!other_extension.is_cleared) {
      switch (cpp_type(other_extension.type)) {
#define HANDLE_TYPE(UPPERCASE, LOWERCASE, CAMELCASE)                       \
        case WireFormatLite::CPPTYPE_##UPPERCASE:                          \
          Set##CAMELCASE(number, other_extension.type,                     \
                         other_extension.LOWERCASE##_value,                \
                         other_extension.descriptor);                      \
          break;

        HANDLE_TYPE( INT32,  int32,  Int32);
        HANDLE_TYPE( INT64,  int64,  Int64);
        HANDLE_TYPE(UINT32, uint32, UInt32);
        HANDLE_TYPE(UINT64, uint64, UInt64);
        HANDLE_TYPE( FLOAT,  float,  Float);
        HANDLE_TYPE(DOUBLE, double, Double);
        HANDLE_TYPE(  BOOL,   bool,   Bool);
        HANDLE_TYPE(  ENUM,   enum,   Enum);
#undef HANDLE_TYPE
        case WireFormatLite::CPPTYPE_STRING:
          SetString(number, other_extension.type,
                    *other_extension.string_value,
                    other_extension.descriptor);
          break;
        case WireFormatLite::CPPTYPE_MESSAGE: {
          Extension* extension;
          bool is_new = MaybeNewExtension(number,
                                          other_extension.descriptor,
                                          &extension);
          if (is_new) {
            extension->type = other_extension.type;
            extension->is_packed = other_extension.is_packed;
            extension->is_repeated = false;
            if (other_extension.is_lazy) {
              extension->is_lazy = true;
              extension->lazymessage_value =
                  other_extension.lazymessage_value->New(arena_);
              extension->lazymessage_value->MergeFrom(
                  *other_extension.lazymessage_value);
            } else {
              extension->is_lazy = false;
              extension->message_value =
                  other_extension.message_value->New(arena_);
              extension->message_value->CheckTypeAndMergeFrom(
                  *other_extension.message_value);
            }
          } else {
            GOOGLE_DCHECK_EQ(extension->type, other_extension.type);
            GOOGLE_DCHECK_EQ(extension->is_packed,other_extension.is_packed);
            GOOGLE_DCHECK(!extension->is_repeated);
            if (other_extension.is_lazy) {
              if (extension->is_lazy) {
                extension->lazymessage_value->MergeFrom(
                    *other_extension.lazymessage_value);
              } else {
                extension->message_value->CheckTypeAndMergeFrom(
                    other_extension.lazymessage_value->GetMessage(
                        *extension->message_value));
              }
            } else {
              if (extension->is_lazy) {
                extension->lazymessage_value->MutableMessage(
                    *other_extension.message_value)->CheckTypeAndMergeFrom(
                        *other_extension.message_value);
              } else {
                extension->message_value->CheckTypeAndMergeFrom(
                    *other_extension.message_value);
              }
            }
          }
          extension->is_cleared = false;
          break;
        }
      }
    }
  }
}

void ExtensionSet::Swap(ExtensionSet* x) {
  if (GetArenaNoVirtual() == x->GetArenaNoVirtual()) {
    using std::swap;
    swap(flat_capacity_, x->flat_capacity_);
    swap(flat_size_, x->flat_size_);
    swap(map_, x->map_);
  } else {
    // TODO(cfallin, rohananil): We maybe able to optimize a case where we are
    // swapping from heap to arena-allocated extension set, by just Own()'ing
    // the extensions.
    ExtensionSet extension_set;
    extension_set.MergeFrom(*x);
    x->Clear();
    x->MergeFrom(*this);
    Clear();
    MergeFrom(extension_set);
  }
}

void ExtensionSet::SwapExtension(ExtensionSet* other,
                                 int number) {
  if (this == other) return;
  Extension* this_ext = FindOrNull(number);
  Extension* other_ext = other->FindOrNull(number);

  if (this_ext == NULL && other_ext == NULL) {
    return;
  }

  if (this_ext != NULL && other_ext != NULL) {
    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
      using std::swap;
      swap(*this_ext, *other_ext);
    } else {
      // TODO(cfallin, rohananil): We could further optimize these cases,
      // especially avoid creation of ExtensionSet, and move MergeFrom logic
      // into Extensions itself (which takes arena as an argument).
      // We do it this way to reuse the copy-across-arenas logic already
      // implemented in ExtensionSet's MergeFrom.
      ExtensionSet temp;
      temp.InternalExtensionMergeFrom(number, *other_ext);
      Extension* temp_ext = temp.FindOrNull(number);
      other_ext->Clear();
      other->InternalExtensionMergeFrom(number, *this_ext);
      this_ext->Clear();
      InternalExtensionMergeFrom(number, *temp_ext);
    }
    return;
  }

  if (this_ext == NULL) {
    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
      *Insert(number).first = *other_ext;
    } else {
      InternalExtensionMergeFrom(number, *other_ext);
    }
    other->Erase(number);
    return;
  }

  if (other_ext == NULL) {
    if (GetArenaNoVirtual() == other->GetArenaNoVirtual()) {
      *other->Insert(number).first = *this_ext;
    } else {
      other->InternalExtensionMergeFrom(number, *this_ext);
    }
    Erase(number);
    return;
  }
}

bool ExtensionSet::IsInitialized() const {
  // Extensions are never required.  However, we need to check that all
  // embedded messages are initialized.
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    for (const auto& kv : *map_.large) {
      if (!kv.second.IsInitialized()) return false;
    }
    return true;
  }
  for (const KeyValue* it = flat_begin(); it != flat_end(); ++it) {
    if (!it->second.IsInitialized()) return false;
  }
  return true;
}

bool ExtensionSet::FindExtensionInfoFromTag(
    uint32 tag, ExtensionFinder* extension_finder, int* field_number,
    ExtensionInfo* extension, bool* was_packed_on_wire) {
  *field_number = WireFormatLite::GetTagFieldNumber(tag);
  WireFormatLite::WireType wire_type = WireFormatLite::GetTagWireType(tag);
  return FindExtensionInfoFromFieldNumber(wire_type, *field_number,
                                          extension_finder, extension,
                                          was_packed_on_wire);
}

bool ExtensionSet::FindExtensionInfoFromFieldNumber(
    int wire_type, int field_number, ExtensionFinder* extension_finder,
    ExtensionInfo* extension, bool* was_packed_on_wire) {
  if (!extension_finder->Find(field_number, extension)) {
    return false;
  }

  WireFormatLite::WireType expected_wire_type =
      WireFormatLite::WireTypeForFieldType(real_type(extension->type));

  // Check if this is a packed field.
  *was_packed_on_wire = false;
  if (extension->is_repeated &&
      wire_type == WireFormatLite::WIRETYPE_LENGTH_DELIMITED &&
      is_packable(expected_wire_type)) {
    *was_packed_on_wire = true;
    return true;
  }
  // Otherwise the wire type must match.
  return expected_wire_type == wire_type;
}

bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
                              ExtensionFinder* extension_finder,
                              FieldSkipper* field_skipper) {
  int number;
  bool was_packed_on_wire;
  ExtensionInfo extension;
  if (!FindExtensionInfoFromTag(
      tag, extension_finder, &number, &extension, &was_packed_on_wire)) {
    return field_skipper->SkipField(input, tag);
  } else {
    return ParseFieldWithExtensionInfo(
        number, was_packed_on_wire, extension, input, field_skipper);
  }
}

#if GOOGLE_PROTOBUF_ENABLE_EXPERIMENTAL_PARSER
const char* ExtensionSet::ParseField(
    uint64 tag, const char* ptr, const MessageLite* containing_type,
    internal::InternalMetadataWithArenaLite* metadata,
    internal::ParseContext* ctx) {
  GeneratedExtensionFinder finder(containing_type);
  int number = tag >> 3;
  bool was_packed_on_wire;
  ExtensionInfo extension;
  if (!FindExtensionInfoFromFieldNumber(tag & 7, number, &finder, &extension,
                                        &was_packed_on_wire)) {
    return UnknownFieldParse(tag, metadata->mutable_unknown_fields(), ptr, ctx);
  }
  return ParseFieldWithExtensionInfo(number, was_packed_on_wire, extension,
                                     metadata, ptr, ctx);
}

const char* ExtensionSet::ParseMessageSetItem(
    const char* ptr, const MessageLite* containing_type,
    internal::InternalMetadataWithArenaLite* metadata,
    internal::ParseContext* ctx) {
  return ParseMessageSetItemTmpl(ptr, containing_type, metadata, ctx);
}

#endif

bool ExtensionSet::ParseFieldWithExtensionInfo(
    int number, bool was_packed_on_wire, const ExtensionInfo& extension,
    io::CodedInputStream* input,
    FieldSkipper* field_skipper) {
  // Explicitly not read extension.is_packed, instead check whether the field
  // was encoded in packed form on the wire.
  if (was_packed_on_wire) {
    uint32 size;
    if (!input->ReadVarint32(&size)) return false;
    io::CodedInputStream::Limit limit = input->PushLimit(size);

    switch (extension.type) {
#define HANDLE_TYPE(UPPERCASE, CPP_CAMELCASE, CPP_LOWERCASE)        \
      case WireFormatLite::TYPE_##UPPERCASE:                                   \
        while (input->BytesUntilLimit() > 0) {                                 \
          CPP_LOWERCASE value;                                                 \
          if (!WireFormatLite::ReadPrimitive<                                  \
                  CPP_LOWERCASE, WireFormatLite::TYPE_##UPPERCASE>(            \
                input, &value)) return false;                                  \
          Add##CPP_CAMELCASE(number, WireFormatLite::TYPE_##UPPERCASE,         \
                             extension.is_packed, value,                       \
                             extension.descriptor);                            \
        }                                                                      \
        break

      HANDLE_TYPE(   INT32,  Int32,   int32);
      HANDLE_TYPE(   INT64,  Int64,   int64);
      HANDLE_TYPE(  UINT32, UInt32,  uint32);
      HANDLE_TYPE(  UINT64, UInt64,  uint64);
      HANDLE_TYPE(  SINT32,  Int32,   int32);
      HANDLE_TYPE(  SINT64,  Int64,   int64);
      HANDLE_TYPE( FIXED32, UInt32,  uint32);
      HANDLE_TYPE( FIXED64, UInt64,  uint64);
      HANDLE_TYPE(SFIXED32,  Int32,   int32);
      HANDLE_TYPE(SFIXED64,  Int64,   int64);
      HANDLE_TYPE(   FLOAT,  Float,   float);
      HANDLE_TYPE(  DOUBLE, Double,  double);
      HANDLE_TYPE(    BOOL,   Bool,    bool);
#undef HANDLE_TYPE

      case WireFormatLite::TYPE_ENUM:
        while (input->BytesUntilLimit() > 0) {
          int value;
          if (!WireFormatLite::ReadPrimitive<int, WireFormatLite::TYPE_ENUM>(
                  input, &value)) return false;
          if (extension.enum_validity_check.func(
                  extension.enum_validity_check.arg, value)) {
            AddEnum(number, WireFormatLite::TYPE_ENUM, extension.is_packed,
                    value, extension.descriptor);
          } else {
            // Invalid value.  Treat as unknown.
            field_skipper->SkipUnknownEnum(number, value);
          }
        }
        break;

      case WireFormatLite::TYPE_STRING:
      case WireFormatLite::TYPE_BYTES:
      case WireFormatLite::TYPE_GROUP:
      case WireFormatLite::TYPE_MESSAGE:
        GOOGLE_LOG(FATAL) << "Non-primitive types can't be packed.";
        break;
    }

    input->PopLimit(limit);
  } else {
    switch (extension.type) {
#define HANDLE_TYPE(UPPERCASE, CPP_CAMELCASE, CPP_LOWERCASE)                   \
      case WireFormatLite::TYPE_##UPPERCASE: {                                 \
        CPP_LOWERCASE value;                                                   \
        if (!WireFormatLite::ReadPrimitive<                                    \
                CPP_LOWERCASE, WireFormatLite::TYPE_##UPPERCASE>(              \
               input, &value)) return false;                                   \
        if (extension.is_repeated) {                                           \
          Add##CPP_CAMELCASE(number, WireFormatLite::TYPE_##UPPERCASE,         \
                             extension.is_packed, value,                       \
                             extension.descriptor);                            \
        } else {                                                               \
          Set##CPP_CAMELCASE(number, WireFormatLite::TYPE_##UPPERCASE, value,  \
                             extension.descriptor);                            \
        }                                                                      \
      } break

      HANDLE_TYPE(   INT32,  Int32,   int32);
      HANDLE_TYPE(   INT64,  Int64,   int64);
      HANDLE_TYPE(  UINT32, UInt32,  uint32);
      HANDLE_TYPE(  UINT64, UInt64,  uint64);
      HANDLE_TYPE(  SINT32,  Int32,   int32);
      HANDLE_TYPE(  SINT64,  Int64,   int64);
      HANDLE_TYPE( FIXED32, UInt32,  uint32);
      HANDLE_TYPE( FIXED64, UInt64,  uint64);
      HANDLE_TYPE(SFIXED32,  Int32,   int32);
      HANDLE_TYPE(SFIXED64,  Int64,   int64);
      HANDLE_TYPE(   FLOAT,  Float,   float);
      HANDLE_TYPE(  DOUBLE, Double,  double);
      HANDLE_TYPE(    BOOL,   Bool,    bool);
#undef HANDLE_TYPE

      case WireFormatLite::TYPE_ENUM: {
        int value;
        if (!WireFormatLite::ReadPrimitive<int, WireFormatLite::TYPE_ENUM>(
                input, &value)) return false;

        if (!extension.enum_validity_check.func(
                extension.enum_validity_check.arg, value)) {
          // Invalid value.  Treat as unknown.
          field_skipper->SkipUnknownEnum(number, value);
        } else if (extension.is_repeated) {
          AddEnum(number, WireFormatLite::TYPE_ENUM, extension.is_packed, value,
                  extension.descriptor);
        } else {
          SetEnum(number, WireFormatLite::TYPE_ENUM, value,
                  extension.descriptor);
        }
        break;
      }

      case WireFormatLite::TYPE_STRING:  {
        std::string* value =
            extension.is_repeated
                ? AddString(number, WireFormatLite::TYPE_STRING,
                            extension.descriptor)
                : MutableString(number, WireFormatLite::TYPE_STRING,
                                extension.descriptor);
        if (!WireFormatLite::ReadString(input, value)) return false;
        break;
      }

      case WireFormatLite::TYPE_BYTES:  {
        std::string* value =
            extension.is_repeated
                ? AddString(number, WireFormatLite::TYPE_BYTES,
                            extension.descriptor)
                : MutableString(number, WireFormatLite::TYPE_BYTES,
                                extension.descriptor);
        if (!WireFormatLite::ReadBytes(input, value)) return false;
        break;
      }

      case WireFormatLite::TYPE_GROUP: {
        MessageLite* value =
            extension.is_repeated
                ? AddMessage(number, WireFormatLite::TYPE_GROUP,
                             *extension.message_info.prototype,
                             extension.descriptor)
                : MutableMessage(number, WireFormatLite::TYPE_GROUP,
                                 *extension.message_info.prototype,
                                 extension.descriptor);
        if (!WireFormatLite::ReadGroup(number, input, value)) return false;
        break;
      }

      case WireFormatLite::TYPE_MESSAGE: {
        MessageLite* value =
            extension.is_repeated
                ? AddMessage(number, WireFormatLite::TYPE_MESSAGE,
                             *extension.message_info.prototype,
                             extension.descriptor)
                : MutableMessage(number, WireFormatLite::TYPE_MESSAGE,
                                 *extension.message_info.prototype,
                                 extension.descriptor);
        if (!WireFormatLite::ReadMessage(input, value)) return false;
        break;
      }
    }
  }

  return true;
}

bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
                              const MessageLite* containing_type) {
  FieldSkipper skipper;
  GeneratedExtensionFinder finder(containing_type);
  return ParseField(tag, input, &finder, &skipper);
}

bool ExtensionSet::ParseField(uint32 tag, io::CodedInputStream* input,
                              const MessageLite* containing_type,
                              io::CodedOutputStream* unknown_fields) {
  CodedOutputStreamFieldSkipper skipper(unknown_fields);
  GeneratedExtensionFinder finder(containing_type);
  return ParseField(tag, input, &finder, &skipper);
}

bool ExtensionSet::ParseMessageSetLite(io::CodedInputStream* input,
                                       ExtensionFinder* extension_finder,
                                       FieldSkipper* field_skipper) {
  while (true) {
    const uint32 tag = input->ReadTag();
    switch (tag) {
      case 0:
        return true;
      case WireFormatLite::kMessageSetItemStartTag:
        if (!ParseMessageSetItemLite(input, extension_finder, field_skipper)) {
          return false;
        }
        break;
      default:
        if (!ParseField(tag, input, extension_finder, field_skipper)) {
          return false;
        }
        break;
    }
  }
}

bool ExtensionSet::ParseMessageSetItemLite(io::CodedInputStream* input,
                                           ExtensionFinder* extension_finder,
                                           FieldSkipper* field_skipper) {
  struct MSLite {
    bool ParseField(int type_id, io::CodedInputStream* input) {
      return me->ParseField(
          WireFormatLite::WIRETYPE_LENGTH_DELIMITED + 8 * type_id, input,
          extension_finder, field_skipper);
    }

    bool SkipField(uint32 tag, io::CodedInputStream* input) {
      return field_skipper->SkipField(input, tag);
    }

    ExtensionSet* me;
    ExtensionFinder* extension_finder;
    FieldSkipper* field_skipper;
  };

  return ParseMessageSetItemImpl(input,
                                 MSLite{this, extension_finder, field_skipper});
}

bool ExtensionSet::ParseMessageSet(io::CodedInputStream* input,
                                   const MessageLite* containing_type,
                                   std::string* unknown_fields) {
  io::StringOutputStream zcis(unknown_fields);
  io::CodedOutputStream output(&zcis);
  CodedOutputStreamFieldSkipper skipper(&output);
  GeneratedExtensionFinder finder(containing_type);
  return ParseMessageSetLite(input, &finder, &skipper);
}

void ExtensionSet::SerializeWithCachedSizes(
    int start_field_number, int end_field_number,
    io::CodedOutputStream* output) const {
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    const auto& end = map_.large->end();
    for (auto it = map_.large->lower_bound(start_field_number);
         it != end && it->first < end_field_number; ++it) {
      it->second.SerializeFieldWithCachedSizes(it->first, output);
    }
    return;
  }
  const KeyValue* end = flat_end();
  for (const KeyValue* it = std::lower_bound(
           flat_begin(), end, start_field_number, KeyValue::FirstComparator());
       it != end && it->first < end_field_number; ++it) {
    it->second.SerializeFieldWithCachedSizes(it->first, output);
  }
}

size_t ExtensionSet::ByteSize() const {
  size_t total_size = 0;
  ForEach([&total_size](int number, const Extension& ext) {
    total_size += ext.ByteSize(number);
  });
  return total_size;
}

// Defined in extension_set_heavy.cc.
// int ExtensionSet::SpaceUsedExcludingSelf() const

bool ExtensionSet::MaybeNewExtension(int number,
                                     const FieldDescriptor* descriptor,
                                     Extension** result) {
  bool extension_is_new = false;
  std::tie(*result, extension_is_new) = Insert(number);
  (*result)->descriptor = descriptor;
  return extension_is_new;
}

// ===================================================================
// Methods of ExtensionSet::Extension

void ExtensionSet::Extension::Clear() {
  if (is_repeated) {
    switch (cpp_type(type)) {
#define HANDLE_TYPE(UPPERCASE, LOWERCASE)                          \
      case WireFormatLite::CPPTYPE_##UPPERCASE:                    \
        repeated_##LOWERCASE##_value->Clear();                     \
        break

      HANDLE_TYPE(  INT32,   int32);
      HANDLE_TYPE(  INT64,   int64);
      HANDLE_TYPE( UINT32,  uint32);
      HANDLE_TYPE( UINT64,  uint64);
      HANDLE_TYPE(  FLOAT,   float);
      HANDLE_TYPE( DOUBLE,  double);
      HANDLE_TYPE(   BOOL,    bool);
      HANDLE_TYPE(   ENUM,    enum);
      HANDLE_TYPE( STRING,  string);
      HANDLE_TYPE(MESSAGE, message);
#undef HANDLE_TYPE
    }
  } else {
    if (!is_cleared) {
      switch (cpp_type(type)) {
        case WireFormatLite::CPPTYPE_STRING:
          string_value->clear();
          break;
        case WireFormatLite::CPPTYPE_MESSAGE:
          if (is_lazy) {
            lazymessage_value->Clear();
          } else {
            message_value->Clear();
          }
          break;
        default:
          // No need to do anything.  Get*() will return the default value
          // as long as is_cleared is true and Set*() will overwrite the
          // previous value.
          break;
      }

      is_cleared = true;
    }
  }
}

void ExtensionSet::Extension::SerializeFieldWithCachedSizes(
    int number,
    io::CodedOutputStream* output) const {
  if (is_repeated) {
    if (is_packed) {
      if (cached_size == 0) return;

      WireFormatLite::WriteTag(number,
          WireFormatLite::WIRETYPE_LENGTH_DELIMITED, output);
      output->WriteVarint32(cached_size);

      switch (real_type(type)) {
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                        \
        case WireFormatLite::TYPE_##UPPERCASE:                              \
          for (int i = 0; i < repeated_##LOWERCASE##_value->size(); i++) {  \
            WireFormatLite::Write##CAMELCASE##NoTag(                        \
              repeated_##LOWERCASE##_value->Get(i), output);                \
          }                                                                 \
          break

        HANDLE_TYPE(   INT32,    Int32,   int32);
        HANDLE_TYPE(   INT64,    Int64,   int64);
        HANDLE_TYPE(  UINT32,   UInt32,  uint32);
        HANDLE_TYPE(  UINT64,   UInt64,  uint64);
        HANDLE_TYPE(  SINT32,   SInt32,   int32);
        HANDLE_TYPE(  SINT64,   SInt64,   int64);
        HANDLE_TYPE( FIXED32,  Fixed32,  uint32);
        HANDLE_TYPE( FIXED64,  Fixed64,  uint64);
        HANDLE_TYPE(SFIXED32, SFixed32,   int32);
        HANDLE_TYPE(SFIXED64, SFixed64,   int64);
        HANDLE_TYPE(   FLOAT,    Float,   float);
        HANDLE_TYPE(  DOUBLE,   Double,  double);
        HANDLE_TYPE(    BOOL,     Bool,    bool);
        HANDLE_TYPE(    ENUM,     Enum,    enum);
#undef HANDLE_TYPE

        case WireFormatLite::TYPE_STRING:
        case WireFormatLite::TYPE_BYTES:
        case WireFormatLite::TYPE_GROUP:
        case WireFormatLite::TYPE_MESSAGE:
          GOOGLE_LOG(FATAL) << "Non-primitive types can't be packed.";
          break;
      }
    } else {
      switch (real_type(type)) {
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                        \
        case WireFormatLite::TYPE_##UPPERCASE:                              \
          for (int i = 0; i < repeated_##LOWERCASE##_value->size(); i++) {  \
            WireFormatLite::Write##CAMELCASE(number,                        \
              repeated_##LOWERCASE##_value->Get(i), output);                \
          }                                                                 \
          break

        HANDLE_TYPE(   INT32,    Int32,   int32);
        HANDLE_TYPE(   INT64,    Int64,   int64);
        HANDLE_TYPE(  UINT32,   UInt32,  uint32);
        HANDLE_TYPE(  UINT64,   UInt64,  uint64);
        HANDLE_TYPE(  SINT32,   SInt32,   int32);
        HANDLE_TYPE(  SINT64,   SInt64,   int64);
        HANDLE_TYPE( FIXED32,  Fixed32,  uint32);
        HANDLE_TYPE( FIXED64,  Fixed64,  uint64);
        HANDLE_TYPE(SFIXED32, SFixed32,   int32);
        HANDLE_TYPE(SFIXED64, SFixed64,   int64);
        HANDLE_TYPE(   FLOAT,    Float,   float);
        HANDLE_TYPE(  DOUBLE,   Double,  double);
        HANDLE_TYPE(    BOOL,     Bool,    bool);
        HANDLE_TYPE(  STRING,   String,  string);
        HANDLE_TYPE(   BYTES,    Bytes,  string);
        HANDLE_TYPE(    ENUM,     Enum,    enum);
        HANDLE_TYPE(   GROUP,    Group, message);
        HANDLE_TYPE( MESSAGE,  Message, message);
#undef HANDLE_TYPE
      }
    }
  } else if (!is_cleared) {
    switch (real_type(type)) {
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, VALUE)                 \
      case WireFormatLite::TYPE_##UPPERCASE:                     \
        WireFormatLite::Write##CAMELCASE(number, VALUE, output); \
        break

      HANDLE_TYPE(   INT32,    Int32,    int32_value);
      HANDLE_TYPE(   INT64,    Int64,    int64_value);
      HANDLE_TYPE(  UINT32,   UInt32,   uint32_value);
      HANDLE_TYPE(  UINT64,   UInt64,   uint64_value);
      HANDLE_TYPE(  SINT32,   SInt32,    int32_value);
      HANDLE_TYPE(  SINT64,   SInt64,    int64_value);
      HANDLE_TYPE( FIXED32,  Fixed32,   uint32_value);
      HANDLE_TYPE( FIXED64,  Fixed64,   uint64_value);
      HANDLE_TYPE(SFIXED32, SFixed32,    int32_value);
      HANDLE_TYPE(SFIXED64, SFixed64,    int64_value);
      HANDLE_TYPE(   FLOAT,    Float,    float_value);
      HANDLE_TYPE(  DOUBLE,   Double,   double_value);
      HANDLE_TYPE(    BOOL,     Bool,     bool_value);
      HANDLE_TYPE(  STRING,   String,  *string_value);
      HANDLE_TYPE(   BYTES,    Bytes,  *string_value);
      HANDLE_TYPE(    ENUM,     Enum,     enum_value);
      HANDLE_TYPE(   GROUP,    Group, *message_value);
#undef HANDLE_TYPE
      case WireFormatLite::TYPE_MESSAGE:
        if (is_lazy) {
          lazymessage_value->WriteMessage(number, output);
        } else {
          WireFormatLite::WriteMessage(number, *message_value, output);
        }
        break;
    }
  }
}

size_t ExtensionSet::Extension::ByteSize(int number) const {
  size_t result = 0;

  if (is_repeated) {
    if (is_packed) {
      switch (real_type(type)) {
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                        \
        case WireFormatLite::TYPE_##UPPERCASE:                              \
          for (int i = 0; i < repeated_##LOWERCASE##_value->size(); i++) {  \
            result += WireFormatLite::CAMELCASE##Size(                      \
              repeated_##LOWERCASE##_value->Get(i));                        \
          }                                                                 \
          break

        HANDLE_TYPE(   INT32,    Int32,   int32);
        HANDLE_TYPE(   INT64,    Int64,   int64);
        HANDLE_TYPE(  UINT32,   UInt32,  uint32);
        HANDLE_TYPE(  UINT64,   UInt64,  uint64);
        HANDLE_TYPE(  SINT32,   SInt32,   int32);
        HANDLE_TYPE(  SINT64,   SInt64,   int64);
        HANDLE_TYPE(    ENUM,     Enum,    enum);
#undef HANDLE_TYPE

        // Stuff with fixed size.
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                        \
        case WireFormatLite::TYPE_##UPPERCASE:                              \
          result += WireFormatLite::k##CAMELCASE##Size *                    \
                    FromIntSize(repeated_##LOWERCASE##_value->size());      \
          break
        HANDLE_TYPE( FIXED32,  Fixed32, uint32);
        HANDLE_TYPE( FIXED64,  Fixed64, uint64);
        HANDLE_TYPE(SFIXED32, SFixed32,  int32);
        HANDLE_TYPE(SFIXED64, SFixed64,  int64);
        HANDLE_TYPE(   FLOAT,    Float,  float);
        HANDLE_TYPE(  DOUBLE,   Double, double);
        HANDLE_TYPE(    BOOL,     Bool,   bool);
#undef HANDLE_TYPE

        case WireFormatLite::TYPE_STRING:
        case WireFormatLite::TYPE_BYTES:
        case WireFormatLite::TYPE_GROUP:
        case WireFormatLite::TYPE_MESSAGE:
          GOOGLE_LOG(FATAL) << "Non-primitive types can't be packed.";
          break;
      }

      cached_size = ToCachedSize(result);
      if (result > 0) {
        result += io::CodedOutputStream::VarintSize32(result);
        result += io::CodedOutputStream::VarintSize32(
            WireFormatLite::MakeTag(number,
                WireFormatLite::WIRETYPE_LENGTH_DELIMITED));
      }
    } else {
      size_t tag_size = WireFormatLite::TagSize(number, real_type(type));

      switch (real_type(type)) {
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                        \
        case WireFormatLite::TYPE_##UPPERCASE:                              \
          result += tag_size *                                              \
                    FromIntSize(repeated_##LOWERCASE##_value->size());      \
          for (int i = 0; i < repeated_##LOWERCASE##_value->size(); i++) {  \
            result += WireFormatLite::CAMELCASE##Size(                      \
              repeated_##LOWERCASE##_value->Get(i));                        \
          }                                                                 \
          break

        HANDLE_TYPE(   INT32,    Int32,   int32);
        HANDLE_TYPE(   INT64,    Int64,   int64);
        HANDLE_TYPE(  UINT32,   UInt32,  uint32);
        HANDLE_TYPE(  UINT64,   UInt64,  uint64);
        HANDLE_TYPE(  SINT32,   SInt32,   int32);
        HANDLE_TYPE(  SINT64,   SInt64,   int64);
        HANDLE_TYPE(  STRING,   String,  string);
        HANDLE_TYPE(   BYTES,    Bytes,  string);
        HANDLE_TYPE(    ENUM,     Enum,    enum);
        HANDLE_TYPE(   GROUP,    Group, message);
        HANDLE_TYPE( MESSAGE,  Message, message);
#undef HANDLE_TYPE

        // Stuff with fixed size.
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                        \
        case WireFormatLite::TYPE_##UPPERCASE:                              \
          result += (tag_size + WireFormatLite::k##CAMELCASE##Size) *       \
                    FromIntSize(repeated_##LOWERCASE##_value->size());      \
          break
        HANDLE_TYPE( FIXED32,  Fixed32, uint32);
        HANDLE_TYPE( FIXED64,  Fixed64, uint64);
        HANDLE_TYPE(SFIXED32, SFixed32,  int32);
        HANDLE_TYPE(SFIXED64, SFixed64,  int64);
        HANDLE_TYPE(   FLOAT,    Float,  float);
        HANDLE_TYPE(  DOUBLE,   Double, double);
        HANDLE_TYPE(    BOOL,     Bool,   bool);
#undef HANDLE_TYPE
      }
    }
  } else if (!is_cleared) {
    result += WireFormatLite::TagSize(number, real_type(type));
    switch (real_type(type)) {
#define HANDLE_TYPE(UPPERCASE, CAMELCASE, LOWERCASE)                      \
      case WireFormatLite::TYPE_##UPPERCASE:                              \
        result += WireFormatLite::CAMELCASE##Size(LOWERCASE);             \
        break

      HANDLE_TYPE(   INT32,    Int32,    int32_value);
      HANDLE_TYPE(   INT64,    Int64,    int64_value);
      HANDLE_TYPE(  UINT32,   UInt32,   uint32_value);
      HANDLE_TYPE(  UINT64,   UInt64,   uint64_value);
      HANDLE_TYPE(  SINT32,   SInt32,    int32_value);
      HANDLE_TYPE(  SINT64,   SInt64,    int64_value);
      HANDLE_TYPE(  STRING,   String,  *string_value);
      HANDLE_TYPE(   BYTES,    Bytes,  *string_value);
      HANDLE_TYPE(    ENUM,     Enum,     enum_value);
      HANDLE_TYPE(   GROUP,    Group, *message_value);
#undef HANDLE_TYPE
      case WireFormatLite::TYPE_MESSAGE: {
        if (is_lazy) {
          size_t size = lazymessage_value->ByteSize();
          result += io::CodedOutputStream::VarintSize32(size) + size;
        } else {
          result += WireFormatLite::MessageSize(*message_value);
        }
        break;
      }

      // Stuff with fixed size.
#define HANDLE_TYPE(UPPERCASE, CAMELCASE)                                 \
      case WireFormatLite::TYPE_##UPPERCASE:                              \
        result += WireFormatLite::k##CAMELCASE##Size;                     \
        break
      HANDLE_TYPE( FIXED32,  Fixed32);
      HANDLE_TYPE( FIXED64,  Fixed64);
      HANDLE_TYPE(SFIXED32, SFixed32);
      HANDLE_TYPE(SFIXED64, SFixed64);
      HANDLE_TYPE(   FLOAT,    Float);
      HANDLE_TYPE(  DOUBLE,   Double);
      HANDLE_TYPE(    BOOL,     Bool);
#undef HANDLE_TYPE
    }
  }

  return result;
}

int ExtensionSet::Extension::GetSize() const {
  GOOGLE_DCHECK(is_repeated);
  switch (cpp_type(type)) {
#define HANDLE_TYPE(UPPERCASE, LOWERCASE)                        \
    case WireFormatLite::CPPTYPE_##UPPERCASE:                    \
      return repeated_##LOWERCASE##_value->size()

    HANDLE_TYPE(  INT32,   int32);
    HANDLE_TYPE(  INT64,   int64);
    HANDLE_TYPE( UINT32,  uint32);
    HANDLE_TYPE( UINT64,  uint64);
    HANDLE_TYPE(  FLOAT,   float);
    HANDLE_TYPE( DOUBLE,  double);
    HANDLE_TYPE(   BOOL,    bool);
    HANDLE_TYPE(   ENUM,    enum);
    HANDLE_TYPE( STRING,  string);
    HANDLE_TYPE(MESSAGE, message);
#undef HANDLE_TYPE
  }

  GOOGLE_LOG(FATAL) << "Can't get here.";
  return 0;
}

// This function deletes all allocated objects. This function should be only
// called if the Extension was created with an arena.
void ExtensionSet::Extension::Free() {
  if (is_repeated) {
    switch (cpp_type(type)) {
#define HANDLE_TYPE(UPPERCASE, LOWERCASE)                          \
      case WireFormatLite::CPPTYPE_##UPPERCASE:                    \
        delete repeated_##LOWERCASE##_value;                       \
        break

      HANDLE_TYPE(  INT32,   int32);
      HANDLE_TYPE(  INT64,   int64);
      HANDLE_TYPE( UINT32,  uint32);
      HANDLE_TYPE( UINT64,  uint64);
      HANDLE_TYPE(  FLOAT,   float);
      HANDLE_TYPE( DOUBLE,  double);
      HANDLE_TYPE(   BOOL,    bool);
      HANDLE_TYPE(   ENUM,    enum);
      HANDLE_TYPE( STRING,  string);
      HANDLE_TYPE(MESSAGE, message);
#undef HANDLE_TYPE
    }
  } else {
    switch (cpp_type(type)) {
      case WireFormatLite::CPPTYPE_STRING:
        delete string_value;
        break;
      case WireFormatLite::CPPTYPE_MESSAGE:
        if (is_lazy) {
          delete lazymessage_value;
        } else {
          delete message_value;
        }
        break;
      default:
        break;
    }
  }
}

// Defined in extension_set_heavy.cc.
// int ExtensionSet::Extension::SpaceUsedExcludingSelf() const

bool ExtensionSet::Extension::IsInitialized() const {
  if (cpp_type(type) == WireFormatLite::CPPTYPE_MESSAGE) {
    if (is_repeated) {
      for (int i = 0; i < repeated_message_value->size(); i++) {
        if (!repeated_message_value->Get(i).IsInitialized()) {
          return false;
        }
      }
    } else {
      if (!is_cleared) {
        if (is_lazy) {
          if (!lazymessage_value->IsInitialized()) return false;
        } else {
          if (!message_value->IsInitialized()) return false;
        }
      }
    }
  }
  return true;
}

// Dummy key method to avoid weak vtable.
void ExtensionSet::LazyMessageExtension::UnusedKeyMethod() {}

const ExtensionSet::Extension* ExtensionSet::FindOrNull(int key) const {
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    return FindOrNullInLargeMap(key);
  }
  const KeyValue* end = flat_end();
  const KeyValue* it =
      std::lower_bound(flat_begin(), end, key, KeyValue::FirstComparator());
  if (it != end && it->first == key) {
    return &it->second;
  }
  return NULL;
}

const ExtensionSet::Extension* ExtensionSet::FindOrNullInLargeMap(
    int key) const {
  assert(is_large());
  LargeMap::const_iterator it = map_.large->find(key);
  if (it != map_.large->end()) {
    return &it->second;
  }
  return NULL;
}

ExtensionSet::Extension* ExtensionSet::FindOrNull(int key) {
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    return FindOrNullInLargeMap(key);
  }
  KeyValue* end = flat_end();
  KeyValue* it =
      std::lower_bound(flat_begin(), end, key, KeyValue::FirstComparator());
  if (it != end && it->first == key) {
    return &it->second;
  }
  return NULL;
}

ExtensionSet::Extension* ExtensionSet::FindOrNullInLargeMap(int key) {
  assert(is_large());
  LargeMap::iterator it = map_.large->find(key);
  if (it != map_.large->end()) {
    return &it->second;
  }
  return NULL;
}

std::pair<ExtensionSet::Extension*, bool> ExtensionSet::Insert(int key) {
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    auto maybe = map_.large->insert({key, Extension()});
    return {&maybe.first->second, maybe.second};
  }
  KeyValue* end = flat_end();
  KeyValue* it =
      std::lower_bound(flat_begin(), end, key, KeyValue::FirstComparator());
  if (it != end && it->first == key) {
    return {&it->second, false};
  }
  if (flat_size_ < flat_capacity_) {
    std::copy_backward(it, end, end + 1);
    ++flat_size_;
    it->first = key;
    it->second = Extension();
    return {&it->second, true};
  }
  GrowCapacity(flat_size_ + 1);
  return Insert(key);
}

void ExtensionSet::GrowCapacity(size_t minimum_new_capacity) {
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    return;  // LargeMap does not have a "reserve" method.
  }
  if (flat_capacity_ >= minimum_new_capacity) {
    return;
  }

  const auto old_flat_capacity = flat_capacity_;

  do {
    flat_capacity_ = flat_capacity_ == 0 ? 1 : flat_capacity_ * 4;
  } while (flat_capacity_ < minimum_new_capacity);

  const KeyValue* begin = flat_begin();
  const KeyValue* end = flat_end();
  if (flat_capacity_ > kMaximumFlatCapacity) {
    // Switch to LargeMap
    map_.large = Arena::Create<LargeMap>(arena_);
    LargeMap::iterator hint = map_.large->begin();
    for (const KeyValue* it = begin; it != end; ++it) {
      hint = map_.large->insert(hint, {it->first, it->second});
    }
    flat_size_ = 0;
  } else {
    map_.flat = Arena::CreateArray<KeyValue>(arena_, flat_capacity_);
    std::copy(begin, end, map_.flat);
  }
  if (arena_ == nullptr) {
    DeleteFlatMap(begin, old_flat_capacity);
  }
}

// static
constexpr uint16 ExtensionSet::kMaximumFlatCapacity;

void ExtensionSet::Erase(int key) {
  if (PROTOBUF_PREDICT_FALSE(is_large())) {
    map_.large->erase(key);
    return;
  }
  KeyValue* end = flat_end();
  KeyValue* it =
      std::lower_bound(flat_begin(), end, key, KeyValue::FirstComparator());
  if (it != end && it->first == key) {
    std::copy(it + 1, end, it);
    --flat_size_;
  }
}

// ==================================================================
// Default repeated field instances for iterator-compatible accessors

const RepeatedPrimitiveDefaults* RepeatedPrimitiveDefaults::default_instance() {
  static auto instance = OnShutdownDelete(new RepeatedPrimitiveDefaults);
  return instance;
}

const RepeatedStringTypeTraits::RepeatedFieldType*
RepeatedStringTypeTraits::GetDefaultRepeatedField() {
  static auto instance = OnShutdownDelete(new RepeatedFieldType);
  return instance;
}

void ExtensionSet::Extension::SerializeMessageSetItemWithCachedSizes(
    int number,
    io::CodedOutputStream* output) const {
  if (type != WireFormatLite::TYPE_MESSAGE || is_repeated) {
    // Not a valid MessageSet extension, but serialize it the normal way.
    SerializeFieldWithCachedSizes(number, output);
    return;
  }

  if (is_cleared) return;

  // Start group.
  output->WriteTag(WireFormatLite::kMessageSetItemStartTag);

  // Write type ID.
  WireFormatLite::WriteUInt32(WireFormatLite::kMessageSetTypeIdNumber,
                              number,
                              output);
  // Write message.
  if (is_lazy) {
    lazymessage_value->WriteMessage(
        WireFormatLite::kMessageSetMessageNumber, output);
  } else {
    WireFormatLite::WriteMessageMaybeToArray(
        WireFormatLite::kMessageSetMessageNumber,
        *message_value,
        output);
  }

  // End group.
  output->WriteTag(WireFormatLite::kMessageSetItemEndTag);
}

size_t ExtensionSet::Extension::MessageSetItemByteSize(int number) const {
  if (type != WireFormatLite::TYPE_MESSAGE || is_repeated) {
    // Not a valid MessageSet extension, but compute the byte size for it the
    // normal way.
    return ByteSize(number);
  }

  if (is_cleared) return 0;

  size_t our_size = WireFormatLite::kMessageSetItemTagsSize;

  // type_id
  our_size += io::CodedOutputStream::VarintSize32(number);

  // message
  size_t message_size = 0;
  if (is_lazy) {
    message_size = lazymessage_value->ByteSizeLong();
  } else {
    message_size = message_value->ByteSizeLong();
  }

  our_size += io::CodedOutputStream::VarintSize32(message_size);
  our_size += message_size;

  return our_size;
}

void ExtensionSet::SerializeMessageSetWithCachedSizes(
    io::CodedOutputStream* output) const {
  ForEach([output](int number, const Extension& ext) {
    ext.SerializeMessageSetItemWithCachedSizes(number, output);
  });
}

size_t ExtensionSet::MessageSetByteSize() const {
  size_t total_size = 0;
  ForEach([&total_size](int number, const Extension& ext) {
    total_size += ext.MessageSetItemByteSize(number);
  });
  return total_size;
}

}  // namespace internal
}  // namespace protobuf
}  // namespace google