src/google/protobuf/dynamic_message.cc

// Protocol Buffers - Google's data interchange format
// Copyright 2008 Google Inc.  All rights reserved.
//
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file or at
// https://developers.google.com/open-source/licenses/bsd

// Author: kenton@google.com (Kenton Varda)
//  Based on original Protocol Buffers design by
//  Sanjay Ghemawat, Jeff Dean, and others.
//
// DynamicMessage is implemented by constructing a data structure which
// has roughly the same memory layout as a generated message would have.
// Then, we use Reflection to implement our reflection interface.  All
// the other operations we need to implement (e.g.  parsing, copying,
// etc.) are already implemented in terms of Reflection, so the rest is
// easy.
//
// The up side of this strategy is that it's very efficient.  We don't
// need to use hash_maps or generic representations of fields.  The
// down side is that this is a low-level memory management hack which
// can be tricky to get right.
//
// As mentioned in the header, we only expose a DynamicMessageFactory
// publicly, not the DynamicMessage class itself.  This is because
// GenericMessageReflection wants to have a pointer to a "default"
// copy of the class, with all fields initialized to their default
// values.  We only want to construct one of these per message type,
// so DynamicMessageFactory stores a cache of default messages for
// each type it sees (each unique Descriptor pointer).  The code
// refers to the "default" copy of the class as the "prototype".
//
// Note on memory allocation:  This module often calls "operator new()"
// to allocate untyped memory, rather than calling something like
// "new uint8_t[]".  This is because "operator new()" means "Give me some
// space which I can use as I please." while "new uint8_t[]" means "Give
// me an array of 8-bit integers.".  In practice, the later may return
// a pointer that is not aligned correctly for general use.  I believe
// Item 8 of "More Effective C++" discusses this in more detail, though
// I don't have the book on me right now so I'm not sure.

#include "google/protobuf/dynamic_message.h"

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <memory>
#include <new>
#include <string>
#include <type_traits>

#include "absl/log/absl_check.h"
#include "absl/log/absl_log.h"
#include "google/protobuf/arenastring.h"
#include "google/protobuf/descriptor.h"
#include "google/protobuf/descriptor.pb.h"
#include "google/protobuf/extension_set.h"
#include "google/protobuf/generated_message_reflection.h"
#include "google/protobuf/generated_message_util.h"
#include "google/protobuf/has_bits.h"
#include "google/protobuf/internal_metadata_locator.h"
#include "google/protobuf/map.h"
#include "google/protobuf/map_field.h"
#include "google/protobuf/message.h"
#include "google/protobuf/message_lite.h"
#include "google/protobuf/micro_string.h"
#include "google/protobuf/port.h"
#include "google/protobuf/repeated_field.h"
#include "google/protobuf/unknown_field_set.h"
#include "google/protobuf/wire_format.h"


// Must be included last.
#include "google/protobuf/port_def.inc"

namespace google {
namespace protobuf {
using internal::ExtensionSet;


using internal::ArenaStringPtr;
using internal::MicroString;

// ===================================================================
// Some helper tables and functions...

namespace internal {

class DynamicMapField final : public MapFieldBase {
 public:
  // We pass the prototype for the entry and the mapped type (if message) to
  // allow the caller to use the appropriate lookup function. During prototype
  // building we need to use a different one.
  DynamicMapField(const Message* default_entry,
                  const Message* mapped_default_entry_if_message,
                  InternalMetadataOffset offset);
  DynamicMapField(const DynamicMapField&) = delete;
  DynamicMapField& operator=(const DynamicMapField&) = delete;
  ~DynamicMapField();

 private:
  friend class MapFieldBase;

  // Must be first for GetMapRaw to work.
  UntypedMapBase map_;
};

static UntypedMapBase::TypeKind CppTypeToTypeKind(
    FieldDescriptor::CppType type) {
  using TK = UntypedMapBase::TypeKind;
  switch (type) {
    case FieldDescriptor::CPPTYPE_BOOL:
      return TK::kBool;
    case FieldDescriptor::CPPTYPE_INT32:
      return TK::kU32;
    case FieldDescriptor::CPPTYPE_UINT32:
      return TK::kU32;
    case FieldDescriptor::CPPTYPE_ENUM:
      return TK::kU32;
    case FieldDescriptor::CPPTYPE_INT64:
      return TK::kU64;
    case FieldDescriptor::CPPTYPE_UINT64:
      return TK::kU64;
    case FieldDescriptor::CPPTYPE_FLOAT:
      return TK::kFloat;
    case FieldDescriptor::CPPTYPE_DOUBLE:
      return TK::kDouble;
    case FieldDescriptor::CPPTYPE_STRING:
      return TK::kString;
    case FieldDescriptor::CPPTYPE_MESSAGE:
      return TK::kMessage;
    default:
      Unreachable();
  }
}

static auto DefaultEntryToTypeInfo(
    const Message* default_entry,
    const Message* mapped_default_entry_if_message) {
  auto* desc = default_entry->GetDescriptor();
  return UntypedMapBase::GetTypeInfoDynamic(
      CppTypeToTypeKind(desc->map_key()->cpp_type()),
      CppTypeToTypeKind(desc->map_value()->cpp_type()),
      mapped_default_entry_if_message);
}

DynamicMapField::DynamicMapField(const Message* default_entry,
                                 const Message* mapped_default_entry_if_message,
                                 InternalMetadataOffset offset)
    : MapFieldBase(default_entry),
      map_(offset.TranslateForMember<offsetof(DynamicMapField, map_)>(),
           DefaultEntryToTypeInfo(default_entry,
                                  mapped_default_entry_if_message)) {
  // This invariant is required by `GetMapRaw` to easily access the map
  // member without paying for dynamic dispatch.
  static_assert(MapFieldBaseForParse::MapOffset() ==
                PROTOBUF_FIELD_OFFSET(DynamicMapField, map_));
}

DynamicMapField::~DynamicMapField() {
  ABSL_DCHECK_EQ(map_.arena(), nullptr);
  map_.ClearTable(/*arena=*/nullptr, /*reset=*/false);
}

}  // namespace internal

using internal::DynamicMapField;

namespace {

bool IsMapFieldInApi(const FieldDescriptor* field) { return field->is_map(); }

bool IsMapEntryField(const FieldDescriptor* field) {
  return (field->containing_type() != nullptr &&
          field->containing_type()->options().map_entry());
}


inline bool InRealOneof(const FieldDescriptor* field) {
  return field->real_containing_oneof() != nullptr;
}

// Compute the byte size of the in-memory representation of the field.
int FieldSpaceUsed(const FieldDescriptor* field) {
  typedef FieldDescriptor FD;  // avoid line wrapping
  if (field->is_repeated()) {
    switch (field->cpp_type()) {
      case FD::CPPTYPE_INT32:
        return sizeof(RepeatedField<int32_t>);
      case FD::CPPTYPE_INT64:
        return sizeof(RepeatedField<int64_t>);
      case FD::CPPTYPE_UINT32:
        return sizeof(RepeatedField<uint32_t>);
      case FD::CPPTYPE_UINT64:
        return sizeof(RepeatedField<uint64_t>);
      case FD::CPPTYPE_DOUBLE:
        return sizeof(RepeatedField<double>);
      case FD::CPPTYPE_FLOAT:
        return sizeof(RepeatedField<float>);
      case FD::CPPTYPE_BOOL:
        return sizeof(RepeatedField<bool>);
      case FD::CPPTYPE_ENUM:
        return sizeof(RepeatedField<int>);
      case FD::CPPTYPE_MESSAGE:
        if (IsMapFieldInApi(field)) {
          return sizeof(DynamicMapField);
        } else {
          return sizeof(RepeatedPtrField<Message>);
        }

      case FD::CPPTYPE_STRING:
        switch (field->cpp_string_type()) {
          case FieldDescriptor::CppStringType::kCord:
            return sizeof(RepeatedField<absl::Cord>);
          case FieldDescriptor::CppStringType::kView:
          case FieldDescriptor::CppStringType::kString:
            return sizeof(RepeatedPtrField<std::string>);
        }
        break;
    }
  } else {
    switch (field->cpp_type()) {
      case FD::CPPTYPE_INT32:
        return sizeof(int32_t);
      case FD::CPPTYPE_INT64:
        return sizeof(int64_t);
      case FD::CPPTYPE_UINT32:
        return sizeof(uint32_t);
      case FD::CPPTYPE_UINT64:
        return sizeof(uint64_t);
      case FD::CPPTYPE_DOUBLE:
        return sizeof(double);
      case FD::CPPTYPE_FLOAT:
        return sizeof(float);
      case FD::CPPTYPE_BOOL:
        return sizeof(bool);
      case FD::CPPTYPE_ENUM:
        return sizeof(int);

      case FD::CPPTYPE_MESSAGE:
        return sizeof(Message*);

      case FD::CPPTYPE_STRING:
        switch (field->cpp_string_type()) {
          case FieldDescriptor::CppStringType::kCord:
            return sizeof(absl::Cord);
          case FieldDescriptor::CppStringType::kView:
            if (internal::EnableExperimentalMicroString()) {
              return sizeof(MicroString);
            }
            [[fallthrough]];
          case FieldDescriptor::CppStringType::kString:
            return sizeof(ArenaStringPtr);
        }
        break;
    }
  }

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

uint32_t FieldFlags(const FieldDescriptor* field) {
  if (internal::EnableExperimentalMicroString() &&   //
      !field->is_repeated() &&                       //
      !field->is_extension() &&                      //
      field->cpp_type() == field->CPPTYPE_STRING &&  //
      field->cpp_string_type() == FieldDescriptor::CppStringType::kView) {
    return internal::kMicroStringMask;
  }
  return 0;
}

inline int DivideRoundingUp(int i, int j) { return (i + (j - 1)) / j; }

static const int kSafeAlignment = sizeof(uint64_t);
static const int kMaxOneofUnionSize = sizeof(uint64_t);

inline int AlignTo(int offset, int alignment) {
  return DivideRoundingUp(offset, alignment) * alignment;
}

// Rounds the given byte offset up to the next offset aligned such that any
// type may be stored at it.
inline int AlignOffset(int offset) { return AlignTo(offset, kSafeAlignment); }

#define bitsizeof(T) (sizeof(T) * 8)

}  // namespace

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

class DynamicMessage final : public Message {
 public:
  // This should only be used by GetPrototypeNoLock() to avoid dead lock.
  DynamicMessage(DynamicMessageFactory::TypeInfo* type_info, bool lock_factory);
  DynamicMessage(const DynamicMessage&) = delete;
  DynamicMessage& operator=(const DynamicMessage&) = delete;

  ~DynamicMessage() PROTOBUF_FINAL;

  // Called on the prototype after construction to initialize message fields.
  // Cross linking the default instances allows for fast reflection access of
  // unset message fields. Without it we would have to go to the MessageFactory
  // to get the prototype, which is a much more expensive operation.
  //
  // Generated messages do not cross-link to avoid dynamic initialization of the
  // global instances.
  // Instead, they keep the default instances in the FieldDescriptor objects.
  void CrossLinkPrototypes();

  // implements Message ----------------------------------------------

  const internal::ClassData* GetClassData() const PROTOBUF_FINAL;

#if defined(__cpp_lib_destroying_delete) && defined(__cpp_sized_deallocation)
  static void operator delete(DynamicMessage* msg, std::destroying_delete_t);
#else
  // We actually allocate more memory than sizeof(*this) when this
  // class's memory is allocated via the global operator new. Thus, we need to
  // manually call the global operator delete. Calling the destructor is taken
  // care of for us. This makes DynamicMessage compatible with -fsized-delete.
  static void operator delete(void* ptr) { ::operator delete(ptr); }
#endif

 private:
  DynamicMessage(const DynamicMessageFactory::TypeInfo* type_info,
                 Arena* arena);

  void SharedCtor(bool lock_factory);

  // Needed to get the offset of the internal metadata member.
  friend class DynamicMessageFactory;

  bool is_prototype() const;

  inline void* OffsetToPointer(int offset) {
    return reinterpret_cast<uint8_t*>(this) + offset;
  }
  inline const void* OffsetToPointer(int offset) const {
    return reinterpret_cast<const uint8_t*>(this) + offset;
  }

  static void* NewImpl(const void* prototype, void* mem, Arena* arena);
  static void DestroyImpl(MessageLite& msg);

  // If `T` is not `void`, it will mask bits off the offset via alignment.
  // Used to remove feature masks that are part of the reflection
  // implementation.
  template <typename T>
  uint32_t FieldOffset(int i) const;
  internal::InternalMetadataOffset FieldInternalMetadataOffset(int i) const;
  template <typename T = void>
  T* MutableRaw(int i);
  template <typename T = void>
  const T& GetRaw(int i) const;
  void* MutableExtensionsRaw();
  void* MutableWeakFieldMapRaw();
  void* MutableOneofCaseRaw(int i);
  void* MutableOneofFieldRaw(const FieldDescriptor* f);

  const DynamicMessageFactory::TypeInfo* type_info_;
  internal::CachedSize cached_byte_size_;
};

using internal::MessageGlobalsBase;

struct DynamicMessageGlobalsInternalType : MessageGlobalsBase {
#ifdef PROTOBUF_MESSAGE_GLOBALS
  explicit DynamicMessageGlobalsInternalType(internal::ClassDataFull data)
      : MessageGlobalsBase(data) {}
#endif  // PROTOBUF_MESSAGE_GLOBALS
  union {
    alignas(internal::kMaxMessageAlignment) DynamicMessage _default;  // NOLINT
  };
};

namespace {
inline uint32_t MsgSizeToGlobalsSize(uint32_t size) {
  return size +
         PROTOBUF_FIELD_OFFSET(DynamicMessageGlobalsInternalType, _default);
}
inline void* DynamicMessageGlobalsToDefaultInstance(void* globals) {
  return &(
      reinterpret_cast<DynamicMessageGlobalsInternalType*>(globals)->_default);
}
}  // namespace

struct DynamicMessageFactory::TypeInfo {
  int has_bits_offset;
  int oneof_case_offset;
  int extensions_offset;

  // Not owned by the TypeInfo.
  DynamicMessageFactory* factory;  // The factory that created this object.
  const DescriptorPool* pool;      // The factory's DescriptorPool.

  // Warning:  The order in which the following pointers are defined is
  //   important (the prototype must be deleted *before* the offsets).
  std::unique_ptr<uint32_t[]> offsets;
  std::unique_ptr<uint32_t[]> has_bits_indices;
  int weak_field_map_offset;  // The offset for the weak_field_map;

#ifndef PROTOBUF_MESSAGE_GLOBALS
  internal::ClassDataFull class_data = {
      internal::ClassData{
          nullptr,  // default_instance
          nullptr,  // tc_table
          &DynamicMessage::IsInitializedImpl,
          &DynamicMessage::MergeImpl,
          internal::MessageCreator(),  // to be filled later
          &DynamicMessage::DestroyImpl,
          static_cast<void (MessageLite::*)()>(&DynamicMessage::ClearImpl),
          DynamicMessage::ByteSizeLongImpl,
          DynamicMessage::_InternalSerializeImpl,
          PROTOBUF_FIELD_OFFSET(DynamicMessage, cached_byte_size_),
          false,
      },
      &internal::kDescriptorMethods,
      nullptr,  // descriptor_table
      nullptr,  // get_metadata_tracker
  };
#else   // !PROTOBUF_MESSAGE_GLOBALS
  DynamicMessageGlobalsInternalType* globals = nullptr;
  internal::ReflectionData reflection_data = {
      &internal::kDescriptorMethods,
      nullptr,  // descriptor_table
      nullptr,  // get_metadata_tracker
  };
#endif  // PROTOBUF_MESSAGE_GLOBALS

  TypeInfo() = default;

#ifndef PROTOBUF_MESSAGE_GLOBALS
  const internal::ClassDataFull& GetClassDataFull() const { return class_data; }
  internal::ClassDataFull& MutableClassDataFull() { return class_data; }

  const Message* GetPrototype() const {
    return static_cast<const Message*>(class_data.prototype);
  }
#else   // !PROTOBUF_MESSAGE_GLOBALS
  const internal::ClassDataFull& GetClassDataFull() const {
    return globals->class_data;
  }
  internal::ClassDataFull& MutableClassDataFull() {
    return globals->class_data;
  }

  const Message* GetPrototype() const {
    return static_cast<const Message*>(&globals->_default);
  }
#endif  // PROTOBUF_MESSAGE_GLOBALS

  ~TypeInfo() {
    const auto& class_data = GetClassDataFull();
    DynamicMessage::DestroyImpl(const_cast<Message&>(*GetPrototype()));
    // With PROTOBUF_MESSAGE_GLOBALS, deleting globals means deleting
    // class_data. Access class_data beforehand.
    delete class_data.reflection();
    auto* type = class_data.descriptor();
    internal::SizedDelete(
        const_cast<MessageGlobalsBase*>(
            MessageGlobalsBase::FromDefaultInstance(GetPrototype())),
        MsgSizeToGlobalsSize(class_data.message_creator.allocation_size()));

    // Scribble the payload to prevent unsanitized opt builds from silently
    // allowing use-after-free bugs where the factory is destroyed but the
    // DynamicMessage instances are still used.
    // This is a common bug with DynamicMessageFactory.
    // NOTE: This must happen after deleting the prototype.
    if (offsets != nullptr) {
      std::fill_n(offsets.get(), type->field_count(), 0xCDCDCDCDu);
    }
    if (has_bits_indices != nullptr) {
      std::fill_n(has_bits_indices.get(), type->field_count(), 0xCDCDCDCDu);
    }
  }
};

DynamicMessage::DynamicMessage(const DynamicMessageFactory::TypeInfo* type_info,
                               Arena* arena)
    : Message(arena, type_info->GetClassDataFull().base()),
      type_info_(type_info) {
  SharedCtor(true);
}

DynamicMessage::DynamicMessage(DynamicMessageFactory::TypeInfo* type_info,
                               bool lock_factory)
    : Message(type_info->GetClassDataFull().base()), type_info_(type_info) {
  // The prototype in type_info has to be set before creating the prototype
  // instance on memory. e.g., message Foo { map<int32_t, Foo> a = 1; }. When
  // creating prototype for Foo, prototype of the map entry will also be
  // created, which needs the address of the prototype of Foo (the value in
  // map). To break the cyclic dependency, we have to assign the address of
  // prototype into type_info first.
#ifndef PROTOBUF_MESSAGE_GLOBALS
  type_info->MutableClassDataFull().prototype = this;
#endif  // PROTOBUF_MESSAGE_GLOBALS
  SharedCtor(lock_factory);
}

template <typename T>
inline uint32_t DynamicMessage::FieldOffset(int i) const {
  uint32_t mask = ~uint32_t{0};
  if constexpr (!std::is_void_v<T>) {
    mask = ~(uint32_t{alignof(T)} - 1);
  }
  return type_info_->offsets[i] & mask;
}
inline internal::InternalMetadataOffset
DynamicMessage::FieldInternalMetadataOffset(int i) const {
  size_t field_offset = FieldOffset<void>(i);
  return internal::InternalMetadataOffset::BuildFromDynamicOffset<
      DynamicMessage>(field_offset);
}
template <typename T>
inline T* DynamicMessage::MutableRaw(int i) {
  return reinterpret_cast<T*>(OffsetToPointer(FieldOffset<T>(i)));
}
template <typename T>
inline const T& DynamicMessage::GetRaw(int i) const {
  return *reinterpret_cast<const T*>(OffsetToPointer(FieldOffset<T>(i)));
}
inline void* DynamicMessage::MutableExtensionsRaw() {
  return OffsetToPointer(type_info_->extensions_offset);
}
inline void* DynamicMessage::MutableWeakFieldMapRaw() {
  return OffsetToPointer(type_info_->weak_field_map_offset);
}
inline void* DynamicMessage::MutableOneofCaseRaw(int i) {
  return OffsetToPointer(type_info_->oneof_case_offset + sizeof(uint32_t) * i);
}
inline void* DynamicMessage::MutableOneofFieldRaw(const FieldDescriptor* f) {
  return OffsetToPointer(
      type_info_
          ->offsets[type_info_->GetClassDataFull().descriptor()->field_count() +
                    f->containing_oneof()->index()]);
}

void DynamicMessage::SharedCtor(bool lock_factory) {
  // We need to call constructors for various fields manually and set
  // default values where appropriate.  We use placement new to call
  // constructors.  If you haven't heard of placement new, I suggest Googling
  // it now.  We use placement new even for primitive types that don't have
  // constructors for consistency.  (In theory, placement new should be used
  // any time you are trying to convert untyped memory to typed memory, though
  // in practice that's not strictly necessary for types that don't have a
  // constructor.)

  const Descriptor* descriptor = type_info_->GetClassDataFull().descriptor();
  Arena* arena = GetArena();
  // Initialize oneof cases.
  int oneof_count = 0;
  for (int i = 0; i < descriptor->real_oneof_decl_count(); ++i) {
    new (MutableOneofCaseRaw(oneof_count++)) uint32_t{0};
  }

  if (type_info_->extensions_offset != -1) {
    new (MutableExtensionsRaw()) ExtensionSet();
  }
  for (int i = 0; i < descriptor->field_count(); i++) {
    const FieldDescriptor* field = descriptor->field(i);
    void* field_ptr = MutableRaw(i);
    if (InRealOneof(field)) {
      continue;
    }
    switch (field->cpp_type()) {
#define HANDLE_TYPE(CPPTYPE, TYPE)                                         \
  case FieldDescriptor::CPPTYPE_##CPPTYPE:                                 \
    if (!field->is_repeated()) {                                           \
      new (field_ptr) TYPE(field->default_value_##TYPE());                 \
    } else {                                                               \
      new (field_ptr) RepeatedField<TYPE>(FieldInternalMetadataOffset(i)); \
    }                                                                      \
    break;

      HANDLE_TYPE(INT32, int32_t);
      HANDLE_TYPE(INT64, int64_t);
      HANDLE_TYPE(UINT32, uint32_t);
      HANDLE_TYPE(UINT64, uint64_t);
      HANDLE_TYPE(DOUBLE, double);
      HANDLE_TYPE(FLOAT, float);
      HANDLE_TYPE(BOOL, bool);
#undef HANDLE_TYPE

      case FieldDescriptor::CPPTYPE_ENUM:
        if (!field->is_repeated()) {
          new (field_ptr) int{field->default_value_enum()->number()};
        } else {
          new (field_ptr) RepeatedField<int>(FieldInternalMetadataOffset(i));
        }
        break;

      case FieldDescriptor::CPPTYPE_STRING:
        switch (field->cpp_string_type()) {
          case FieldDescriptor::CppStringType::kCord:
            if (!field->is_repeated()) {
              if (field->has_default_value()) {
                new (field_ptr) absl::Cord(field->default_value_string());
              } else {
                new (field_ptr) absl::Cord;
              }
              if (arena != nullptr) {
                // Cord does not support arena so here we need to notify arena
                // to remove the data it allocated on the heap by calling its
                // destructor.
                arena->OwnDestructor(static_cast<absl::Cord*>(field_ptr));
              }
            } else {
              new (field_ptr)
                  RepeatedField<absl::Cord>(FieldInternalMetadataOffset(i));
              if (arena != nullptr) {
                // Needs to destroy Cord elements.
                arena->OwnDestructor(
                    static_cast<RepeatedField<absl::Cord>*>(field_ptr));
              }
            }
            break;
          case FieldDescriptor::CppStringType::kView:
            if (internal::EnableExperimentalMicroString() &&
                !field->is_repeated()) {
              *MutableRaw<MicroString>(i) =
                  is_prototype()
                      // Make a new object, potentially creating the default.
                      ? MicroString::MakeDefaultValuePrototype(
                            field->default_value_string())
                      // Copy from the prototype.
                      : MicroString(arena, static_cast<const DynamicMessage*>(
                                               type_info_->GetPrototype())
                                               ->GetRaw<MicroString>(i));
              break;
            }
            [[fallthrough]];
          case FieldDescriptor::CppStringType::kString:
            if (!field->is_repeated()) {
              ArenaStringPtr* asp = new (field_ptr) ArenaStringPtr();
              asp->InitDefault();
            } else {
              new (field_ptr)
                  RepeatedPtrField<std::string>(FieldInternalMetadataOffset(i));
            }
            break;
        }
        break;

      case FieldDescriptor::CPPTYPE_MESSAGE: {
        if (!field->is_repeated()) {
          new (field_ptr) Message*(nullptr);
        } else {
          if (IsMapFieldInApi(field)) {
            const auto* sub =
                field->message_type()->map_value()->message_type();
            // We need to lock in most cases to avoid data racing. Only not lock
            // when the constructor is called inside GetPrototype(), in which
            // case we have already locked the factory.
            new (field_ptr) DynamicMapField(
                lock_factory
                    ? type_info_->factory->GetPrototype(field->message_type())
                    : type_info_->factory->GetPrototypeNoLock(
                          field->message_type()),
                sub != nullptr
                    ? lock_factory
                          ? type_info_->factory->GetPrototype(sub)
                          : type_info_->factory->GetPrototypeNoLock(sub)
                    : nullptr,
                FieldInternalMetadataOffset(i));
          } else {
            new (field_ptr)
                RepeatedPtrField<Message>(FieldInternalMetadataOffset(i));
          }
        }
        break;
      }
    }
  }
}

bool DynamicMessage::is_prototype() const {
  return type_info_->GetPrototype() == this ||
         // If type_info_->prototype is nullptr, then we must be constructing
         // the prototype now, which means we must be the prototype.
         type_info_->GetPrototype() == nullptr;
}

#if defined(__cpp_lib_destroying_delete) && defined(__cpp_sized_deallocation)
void DynamicMessage::operator delete(DynamicMessage* msg,
                                     std::destroying_delete_t) {
  const size_t size = msg->type_info_->GetClassDataFull().allocation_size();
  msg->~DynamicMessage();
  ::operator delete(msg, size);
}
#endif

DynamicMessage::~DynamicMessage() {
  const Descriptor* descriptor = type_info_->GetClassDataFull().descriptor();

  _internal_metadata_.Delete<UnknownFieldSet>();

  if (type_info_->extensions_offset != -1) {
    reinterpret_cast<ExtensionSet*>(MutableExtensionsRaw())->~ExtensionSet();
  }

  // We need to manually run the destructors for repeated fields and strings,
  // just as we ran their constructors in the DynamicMessage constructor.
  // We also need to manually delete oneof fields if it is set and is string
  // or message.
  // Additionally, if any singular embedded messages have been allocated, we
  // need to delete them, UNLESS we are the prototype message of this type,
  // in which case any embedded messages are other prototypes and shouldn't
  // be touched.
  for (int i = 0; i < descriptor->field_count(); i++) {
    const FieldDescriptor* field = descriptor->field(i);
    if (InRealOneof(field)) {
      void* field_ptr = MutableOneofCaseRaw(field->containing_oneof()->index());
      if (*(reinterpret_cast<const int32_t*>(field_ptr)) == field->number()) {
        field_ptr = MutableOneofFieldRaw(field);
        if (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING) {
          switch (field->cpp_string_type()) {
            case FieldDescriptor::CppStringType::kCord:
              delete *reinterpret_cast<absl::Cord**>(field_ptr);
              break;
            case FieldDescriptor::CppStringType::kView:
              if (internal::EnableExperimentalMicroString()) {
                if (is_prototype()) {
                  reinterpret_cast<MicroString*>(field_ptr)
                      ->DestroyDefaultValuePrototype();
                } else {
                  reinterpret_cast<MicroString*>(field_ptr)->Destroy();
                }
                break;
              }
              [[fallthrough]];
            case FieldDescriptor::CppStringType::kString: {
              reinterpret_cast<ArenaStringPtr*>(field_ptr)->Destroy();
              break;
            }
          }
        } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
            delete *reinterpret_cast<Message**>(field_ptr);
        }
      }
      continue;
    }
    void* field_ptr = MutableRaw(i);

    if (field->is_repeated()) {
      switch (field->cpp_type()) {
#define HANDLE_TYPE(UPPERCASE, LOWERCASE)                  \
  case FieldDescriptor::CPPTYPE_##UPPERCASE:               \
    reinterpret_cast<RepeatedField<LOWERCASE>*>(field_ptr) \
        ->~RepeatedField<LOWERCASE>();                     \
    break

        HANDLE_TYPE(INT32, int32_t);
        HANDLE_TYPE(INT64, int64_t);
        HANDLE_TYPE(UINT32, uint32_t);
        HANDLE_TYPE(UINT64, uint64_t);
        HANDLE_TYPE(DOUBLE, double);
        HANDLE_TYPE(FLOAT, float);
        HANDLE_TYPE(BOOL, bool);
        HANDLE_TYPE(ENUM, int);
#undef HANDLE_TYPE

        case FieldDescriptor::CPPTYPE_STRING:
          switch (field->cpp_string_type()) {
            case FieldDescriptor::CppStringType::kCord:
              reinterpret_cast<RepeatedField<absl::Cord>*>(field_ptr)
                  ->~RepeatedField<absl::Cord>();
              break;
            case FieldDescriptor::CppStringType::kView:
            case FieldDescriptor::CppStringType::kString:
              reinterpret_cast<RepeatedPtrField<std::string>*>(field_ptr)
                  ->~RepeatedPtrField<std::string>();
              break;
          }
          break;

        case FieldDescriptor::CPPTYPE_MESSAGE:
          if (IsMapFieldInApi(field)) {
            reinterpret_cast<DynamicMapField*>(field_ptr)->~DynamicMapField();
          } else {
            reinterpret_cast<RepeatedPtrField<Message>*>(field_ptr)
                ->~RepeatedPtrField<Message>();
          }
          break;
      }

    } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_STRING) {
      switch (field->cpp_string_type()) {
        case FieldDescriptor::CppStringType::kCord:
          reinterpret_cast<absl::Cord*>(field_ptr)->~Cord();
          break;
        case FieldDescriptor::CppStringType::kView:
          if (internal::EnableExperimentalMicroString()) {
            if (is_prototype()) {
              MutableRaw<MicroString>(i)->DestroyDefaultValuePrototype();
            } else {
              MutableRaw<MicroString>(i)->Destroy();
            }
            break;
          }
          [[fallthrough]];
        case FieldDescriptor::CppStringType::kString: {
          reinterpret_cast<ArenaStringPtr*>(field_ptr)->Destroy();
          break;
        }
      }
    } else if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE) {
        if (!is_prototype()) {
          Message* message = *reinterpret_cast<Message**>(field_ptr);
          if (message != nullptr) {
            delete message;
          }
        }
    }
  }
}

void* DynamicMessage::NewImpl(const void* prototype, void* mem, Arena* arena) {
  const auto* type_info =
      static_cast<const DynamicMessage*>(prototype)->type_info_;
  memset(mem, 0, type_info->GetClassDataFull().allocation_size());
  return new (mem) DynamicMessage(type_info, arena);
}

void DynamicMessage::DestroyImpl(MessageLite& msg) {
  static_cast<DynamicMessage&>(msg).~DynamicMessage();
}

void DynamicMessage::CrossLinkPrototypes() {
  // This should only be called on the prototype message.
  ABSL_CHECK(is_prototype());

  DynamicMessageFactory* factory = type_info_->factory;
  const Descriptor* descriptor = type_info_->GetClassDataFull().descriptor();

  // Cross-link default messages.
  for (int i = 0; i < descriptor->field_count(); i++) {
    const FieldDescriptor* field = descriptor->field(i);
    PROTOBUF_IGNORE_DEPRECATION_START
    const bool field_is_weak = field->options().weak();
    PROTOBUF_IGNORE_DEPRECATION_STOP
    if (field->cpp_type() == FieldDescriptor::CPPTYPE_MESSAGE &&
        !field_is_weak && !InRealOneof(field) && !field->is_repeated()) {
      void* field_ptr = MutableRaw(i);
      // For fields with message types, we need to cross-link with the
      // prototype for the field's type.
      // For singular fields, the field is just a pointer which should
      // point to the prototype.
      *reinterpret_cast<const Message**>(field_ptr) =
          factory->GetPrototypeNoLock(field->message_type());
    }
  }
}

const internal::ClassData* DynamicMessage::GetClassData() const {
  return type_info_->GetClassDataFull().base();
}

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

DynamicMessageFactory::DynamicMessageFactory()
    : pool_(nullptr), delegate_to_generated_factory_(false) {}

DynamicMessageFactory::DynamicMessageFactory(
    const DescriptorPool* PROTOBUF_NONNULL pool)
    : pool_(pool), delegate_to_generated_factory_(false) {}

DynamicMessageFactory::~DynamicMessageFactory() {
  for (auto iter = prototypes_.begin(); iter != prototypes_.end(); ++iter) {
    delete iter->second;
  }
}

const Message* PROTOBUF_NONNULL
DynamicMessageFactory::GetPrototype(const Descriptor* PROTOBUF_NONNULL type) {
  ABSL_CHECK(type != nullptr);
  absl::MutexLock lock(&prototypes_mutex_);
  return GetPrototypeNoLock(type);
}

const Message* DynamicMessageFactory::GetPrototypeNoLock(
    const Descriptor* PROTOBUF_NONNULL type) {
  if (delegate_to_generated_factory_ &&
      type->file()->pool() == DescriptorPool::generated_pool()) {
    const Message* result = MessageFactory::TryGetGeneratedPrototype(type);
    if (result != nullptr) return result;
    // Otherwise, we will create it dynamically so keep going.
  }

  const TypeInfo** target = &prototypes_[type];
  if (*target != nullptr) {
    // Already exists.
    return (*target)->GetPrototype();
  }

  TypeInfo* type_info = new TypeInfo;
  *target = type_info;

#ifndef PROTOBUF_MESSAGE_GLOBALS
  type_info->MutableClassDataFull().set_descriptor(type);
  type_info->MutableClassDataFull().is_dynamic = true;
#endif  // !PROTOBUF_MESSAGE_GLOBALS
  type_info->pool = (pool_ == nullptr) ? type->file()->pool() : pool_;
  type_info->factory = this;

  // We need to construct all the structures passed to Reflection's constructor.
  // This includes:
  // - A block of memory that contains space for all the message's fields.
  // - An array of integers indicating the byte offset of each field within
  //   this block.
  // - A big bitfield containing a bit for each field indicating whether
  //   or not that field is set.
  int real_oneof_count = type->real_oneof_decl_count();

  // Compute size and offsets.
  uint32_t* offsets = new uint32_t[type->field_count() + real_oneof_count];
  type_info->offsets.reset(offsets);

  // Decide all field offsets by packing in order.
  // We place the DynamicMessage object itself at the beginning of the allocated
  // space.
  int size = sizeof(DynamicMessage);
  size = AlignOffset(size);

  // Next the has_bits, which is an array of uint32s.
  type_info->has_bits_offset = -1;
  int max_hasbit = 0;
  for (int i = 0; i < type->field_count(); i++) {
    const FieldDescriptor* field = type->field(i);

    // If a field has hasbits, it could be either an explicit-presence or
    // implicit-presence field. Explicit presence fields will have "true
    // hasbits" where hasbit is set iff field is present. Implicit presence
    // fields will have "hint hasbits" where
    // - if hasbit is unset, field is not present.
    // - if hasbit is set, field is present if it is also nonempty.
    if (internal::cpp::HasHasbitWithoutProfile(field)) {
      // TODO: b/112602698 - during Python textproto serialization, MapEntry
      // messages may be generated from DynamicMessage on the fly. C++
      // implementations of MapEntry messages always have hasbits, but
      // has_presence return values might be different depending on how field
      // presence is set. For MapEntrys, has_presence returns true for
      // explicit-presence (proto2) messages and returns false for
      // implicit-presence (proto3) messages.
      //
      // In the case of implicit presence, there is a potential inconsistency in
      // code behavior between C++ and Python:
      // - If C++ implementation is linked, hasbits are always generated for
      //   MapEntry messages, and MapEntry messages will behave like explicit
      //   presence.
      // - If C++ implementation is not linked, Python defaults to the
      //   DynamicMessage implementation for MapEntrys which traditionally does
      //   not assume the presence of hasbits, so the default Python behavior
      //   for MapEntry messages (by default C++ implementations are not linked)
      //   will fall back to the DynamicMessage implementation and behave like
      //   implicit presence.
      // This is an inconsistency and this if-condition preserves it.
      //
      // Longer term, we want to get rid of this additional if-check of
      // IsMapEntryField. It might take one or more breaking changes and more
      // consensus gathering & clarification though.
      if (!field->has_presence() && IsMapEntryField(field)) {
        continue;
      }

      if (type_info->has_bits_offset == -1) {
        // At least one field in the message requires a hasbit, so allocate
        // hasbits.
        type_info->has_bits_offset = size;
        uint32_t* has_bits_indices = new uint32_t[type->field_count()];
        for (int j = 0; j < type->field_count(); j++) {
          // Initialize to kNoHasbit, fields that need a hasbit will overwrite.
          has_bits_indices[j] = static_cast<uint32_t>(internal::kNoHasbit);
        }
        type_info->has_bits_indices.reset(has_bits_indices);
      }
      type_info->has_bits_indices[i] = max_hasbit++;
    }
  }

  if (max_hasbit > 0) {
    int has_bits_array_size = DivideRoundingUp(max_hasbit, bitsizeof(uint32_t));
    size += has_bits_array_size * sizeof(uint32_t);
    size = AlignOffset(size);
  }

  // The oneof_case, if any. It is an array of uint32s.
  if (real_oneof_count > 0) {
    type_info->oneof_case_offset = size;
    size += real_oneof_count * sizeof(uint32_t);
    size = AlignOffset(size);
  } else {
    // No oneofs.
    type_info->oneof_case_offset = -1;
  }

  // The ExtensionSet, if any.
  if (type->extension_range_count() > 0) {
    type_info->extensions_offset = size;
    size += sizeof(ExtensionSet);
    size = AlignOffset(size);
  } else {
    // No extensions.
    type_info->extensions_offset = -1;
  }

  // All the fields.
  //
  // TODO:  Optimize the order of fields to minimize padding.
  for (int i = 0; i < type->field_count(); i++) {
    // Make sure field is aligned to avoid bus errors.
    // Oneof fields do not use any space.
    if (!InRealOneof(type->field(i))) {
      int field_size = FieldSpaceUsed(type->field(i));
      size = AlignTo(size, std::min(kSafeAlignment, field_size));
      offsets[i] = size | FieldFlags(type->field(i));
      size += field_size;
    }
  }

  // The oneofs.
  for (int i = 0; i < type->real_oneof_decl_count(); i++) {
    size = AlignTo(size, kSafeAlignment);
    offsets[type->field_count() + i] = size;

    for (int j = 0; j < type->real_oneof_decl(i)->field_count(); j++) {
      const FieldDescriptor* field = type->real_oneof_decl(i)->field(j);
      // oneof fields' offset is the one for the union.
      // They are already set above, so copy them.
      offsets[field->index()] = size | FieldFlags(field);
    }

    size += kMaxOneofUnionSize;
  }

  type_info->weak_field_map_offset = -1;

#ifndef PROTOBUF_MESSAGE_GLOBALS
  type_info->MutableClassDataFull().message_creator =
      internal::MessageCreator(DynamicMessage::NewImpl, size, kSafeAlignment);
#endif  // !PROTOBUF_MESSAGE_GLOBALS

  // Construct the reflection object.

  // Allocate the message globals object that contains the default instance.
  uint32_t globals_size = MsgSizeToGlobalsSize(size);
  void* globals_base = internal::Allocate(globals_size);
  memset(globals_base, 0, globals_size);
  auto* msg_base = DynamicMessageGlobalsToDefaultInstance(globals_base);

#ifdef PROTOBUF_MESSAGE_GLOBALS
  type_info->globals = new (globals_base)
      DynamicMessageGlobalsInternalType(internal::ClassDataFull{
          internal::ClassData{
              reinterpret_cast<const DynamicMessage*>(msg_base),  // prototype
              nullptr,                                            // tc_table
              &DynamicMessage::IsInitializedImpl,
              &DynamicMessage::MergeImpl,
              internal::MessageCreator(DynamicMessage::NewImpl, size,
                                       kSafeAlignment),
              &DynamicMessage::DestroyImpl,
              static_cast<void (MessageLite::*)()>(&DynamicMessage::ClearImpl),
              DynamicMessage::ByteSizeLongImpl,
              DynamicMessage::_InternalSerializeImpl,
              PROTOBUF_FIELD_OFFSET(DynamicMessage, cached_byte_size_),
              false,
          },
          &type_info->reflection_data,
      });
  type_info->globals->class_data.set_descriptor(type);
  type_info->globals->class_data.is_dynamic = true;
#endif  // PROTOBUF_MESSAGE_GLOBALS

  // We have already locked the factory so we should not lock in the constructor
  // of dynamic message to avoid dead lock.
  DynamicMessage* prototype = new (msg_base) DynamicMessage(type_info, false);

  internal::ReflectionSchema schema(
      /*default_instance=*/static_cast<const Message*>(
          type_info->GetPrototype()),
      type_info->offsets.get(), type_info->has_bits_indices.get(),
      type_info->has_bits_offset, type_info->extensions_offset,
      type_info->oneof_case_offset,
      /*object_size=*/
      static_cast<int>(type_info->GetClassDataFull().allocation_size()),
      type_info->weak_field_map_offset,
      /*split_offset=*/-1,
      /*sizeof_split=*/-1);

  type_info->MutableClassDataFull().set_reflection(
      new Reflection(type_info->GetClassDataFull().descriptor(), schema,
                     type_info->pool, this));

  // Cross link prototypes.
  prototype->CrossLinkPrototypes();

  return prototype;
}

}  // namespace protobuf
}  // namespace google

#include "google/protobuf/port_undef.inc"  // NOLINT