src/google/protobuf/repeated_ptr_field.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.

#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <cstring>
#include <limits>
#include <string>

#include "absl/log/absl_check.h"
#include "google/protobuf/arena.h"
#include "google/protobuf/implicit_weak_message.h"
#include "google/protobuf/port.h"
#include "google/protobuf/repeated_field.h"

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

namespace google {
namespace protobuf {

namespace internal {

void** RepeatedPtrFieldBase::InternalExtend(int extend_amount) {
  ABSL_DCHECK(extend_amount > 0);
  constexpr size_t ptr_size = sizeof(rep()->elements[0]);
  int new_capacity = total_size_ + extend_amount;
  Arena* arena = GetArena();
  new_capacity = internal::CalculateReserveSize<void*, kRepHeaderSize>(
      total_size_, new_capacity);
  ABSL_CHECK_LE(
      static_cast<int64_t>(new_capacity),
      static_cast<int64_t>(
          (std::numeric_limits<size_t>::max() - kRepHeaderSize) / ptr_size))
      << "Requested size is too large to fit into size_t.";
  size_t bytes = kRepHeaderSize + ptr_size * new_capacity;
  Rep* new_rep;
  void* old_tagged_ptr = tagged_rep_or_elem_;
  if (arena == nullptr) {
    internal::SizedPtr res = internal::AllocateAtLeast(bytes);
    new_capacity = static_cast<int>((res.n - kRepHeaderSize) / ptr_size);
    new_rep = reinterpret_cast<Rep*>(res.p);
  } else {
    new_rep = reinterpret_cast<Rep*>(Arena::CreateArray<char>(arena, bytes));
  }

  if (using_sso()) {
    new_rep->allocated_size = old_tagged_ptr != nullptr ? 1 : 0;
    new_rep->elements[0] = old_tagged_ptr;
  } else {
    Rep* old_rep =
        reinterpret_cast<Rep*>(reinterpret_cast<uintptr_t>(old_tagged_ptr) - 1);
    if (old_rep->allocated_size > 0) {
      memcpy(new_rep->elements, old_rep->elements,
             old_rep->allocated_size * ptr_size);
    }
    new_rep->allocated_size = old_rep->allocated_size;

    size_t old_size = total_size_ * ptr_size + kRepHeaderSize;
    if (arena == nullptr) {
      internal::SizedDelete(old_rep, old_size);
    } else {
      arena->ReturnArrayMemory(old_rep, old_size);
    }
  }

  tagged_rep_or_elem_ =
      reinterpret_cast<void*>(reinterpret_cast<uintptr_t>(new_rep) + 1);
  total_size_ = new_capacity;
  return &new_rep->elements[current_size_];
}

void RepeatedPtrFieldBase::Reserve(int capacity) {
  if (capacity > total_size_) {
    InternalExtend(capacity - total_size_);
  }
}

void RepeatedPtrFieldBase::DestroyProtos() {
  ABSL_DCHECK(tagged_rep_or_elem_);
  ABSL_DCHECK(arena_ == nullptr);
  if (using_sso()) {
    delete static_cast<MessageLite*>(tagged_rep_or_elem_);
  } else {
    Rep* r = rep();
    int n = r->allocated_size;
    void* const* elements = r->elements;
    for (int i = 0; i < n; i++) {
      delete static_cast<MessageLite*>(elements[i]);
    }
    const size_t size = total_size_ * sizeof(elements[0]) + kRepHeaderSize;
    internal::SizedDelete(r, size);
  }

  // TODO:  Eliminate this store when invoked from the destructor,
  // since it is dead.
  tagged_rep_or_elem_ = nullptr;
}

void* RepeatedPtrFieldBase::AddOutOfLineHelper(void* obj) {
  if (tagged_rep_or_elem_ == nullptr) {
    ABSL_DCHECK_EQ(current_size_, 0);
    ABSL_DCHECK(using_sso());
    ABSL_DCHECK_EQ(allocated_size(), 0);
    ExchangeCurrentSize(1);
    return tagged_rep_or_elem_ = obj;
  }
  if (using_sso() || rep()->allocated_size == total_size_) {
    InternalExtend(1);  // Equivalent to "Reserve(total_size_ + 1)"
  }
  Rep* r = rep();
  ++r->allocated_size;
  return r->elements[ExchangeCurrentSize(current_size_ + 1)] = obj;
}

void RepeatedPtrFieldBase::CloseGap(int start, int num) {
  if (using_sso()) {
    if (start == 0 && num == 1) {
      tagged_rep_or_elem_ = nullptr;
    }
  } else {
    // Close up a gap of "num" elements starting at offset "start".
    Rep* r = rep();
    for (int i = start + num; i < r->allocated_size; ++i)
      r->elements[i - num] = r->elements[i];
    r->allocated_size -= num;
  }
  ExchangeCurrentSize(current_size_ - num);
}

MessageLite* RepeatedPtrFieldBase::AddWeak(const MessageLite* prototype) {
  if (current_size_ < allocated_size()) {
    return reinterpret_cast<MessageLite*>(
        element_at(ExchangeCurrentSize(current_size_ + 1)));
  }
  MessageLite* result = prototype
                            ? prototype->New(arena_)
                            : Arena::CreateMessage<ImplicitWeakMessage>(arena_);
  return static_cast<MessageLite*>(AddOutOfLineHelper(result));
}

void InternalOutOfLineDeleteMessageLite(MessageLite* message) {
  delete message;
}

template PROTOBUF_EXPORT_TEMPLATE_DEFINE void
memswap<ArenaOffsetHelper<RepeatedPtrFieldBase>::value>(
    char* PROTOBUF_RESTRICT, char* PROTOBUF_RESTRICT);

template <>
void RepeatedPtrFieldBase::MergeFrom<std::string>(
    const RepeatedPtrFieldBase& from) {
  ABSL_DCHECK_NE(&from, this);
  int new_size = current_size_ + from.current_size_;
  auto dst = reinterpret_cast<std::string**>(InternalReserve(new_size));
  auto src = reinterpret_cast<std::string* const*>(from.elements());
  auto end = src + from.current_size_;
  auto end_assign = src + std::min(ClearedCount(), from.current_size_);
  for (; src < end_assign; ++dst, ++src) {
    (*dst)->assign(**src);
  }
  if (Arena* const arena = arena_) {
    for (; src < end; ++dst, ++src) {
      *dst = Arena::Create<std::string>(arena, **src);
    }
  } else {
    for (; src < end; ++dst, ++src) {
      *dst = new std::string(**src);
    }
  }
  ExchangeCurrentSize(new_size);
  if (new_size > allocated_size()) {
    rep()->allocated_size = new_size;
  }
}


int RepeatedPtrFieldBase::MergeIntoClearedMessages(
    const RepeatedPtrFieldBase& from) {
  auto dst = reinterpret_cast<MessageLite**>(elements() + current_size_);
  auto src = reinterpret_cast<MessageLite* const*>(from.elements());
  int count = std::min(ClearedCount(), from.current_size_);
  for (int i = 0; i < count; ++i) {
    dst[i]->CheckTypeAndMergeFrom(*src[i]);
  }
  return count;
}

void RepeatedPtrFieldBase::MergeFromConcreteMessage(
    const RepeatedPtrFieldBase& from, CopyFn copy_fn) {
  ABSL_DCHECK_NE(&from, this);
  int new_size = current_size_ + from.current_size_;
  auto dst = reinterpret_cast<MessageLite**>(InternalReserve(new_size));
  auto src = reinterpret_cast<MessageLite const* const*>(from.elements());
  auto end = src + from.current_size_;
  if (PROTOBUF_PREDICT_FALSE(ClearedCount() > 0)) {
    int recycled = MergeIntoClearedMessages(from);
    dst += recycled;
    src += recycled;
  }
  Arena* arena = GetArena();
  for (; src < end; ++src, ++dst) {
    *dst = copy_fn(arena, **src);
  }
  ExchangeCurrentSize(new_size);
  if (new_size > allocated_size()) {
    rep()->allocated_size = new_size;
  }
}

template <>
void RepeatedPtrFieldBase::MergeFrom<MessageLite>(
    const RepeatedPtrFieldBase& from) {
  ABSL_DCHECK_NE(&from, this);
  int new_size = current_size_ + from.current_size_;
  auto dst = reinterpret_cast<MessageLite**>(InternalReserve(new_size));
  auto src = reinterpret_cast<MessageLite const* const*>(from.elements());
  auto end = src + from.current_size_;
  if (PROTOBUF_PREDICT_FALSE(ClearedCount() > 0)) {
    int recycled = MergeIntoClearedMessages(from);
    dst += recycled;
    src += recycled;
  }
  Arena* arena = GetArena();
  for (; src < end; ++src, ++dst) {
    *dst = (*src)->New(arena);
    (*dst)->CheckTypeAndMergeFrom(**src);
  }
  ExchangeCurrentSize(new_size);
  if (new_size > allocated_size()) {
    rep()->allocated_size = new_size;
  }
}

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

#include "google/protobuf/port_undef.inc"