// Copyright 2014 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "gpu/command_buffer/common/buffer.h"

#include <stddef.h>
#include <stdint.h>

#include <ostream>

#include "base/atomic_sequence_num.h"
#include "base/bits.h"
#include "base/check_op.h"
#include "base/compiler_specific.h"
#include "base/containers/span.h"
#include "base/format_macros.h"
#include "base/no_destructor.h"
#include "base/numerics/safe_math.h"
#include "base/strings/stringprintf.h"

namespace gpu {
namespace {

// Global atomic to generate unique buffer IDs.
base::AtomicSequenceNumber g_next_buffer_id;

}  // namespace

const base::UnsafeSharedMemoryRegion& BufferBacking::shared_memory_region()
    const {
  static const base::NoDestructor<base::UnsafeSharedMemoryRegion>
      kInvalidRegion;
  return *kInvalidRegion;
}

base::UnguessableToken BufferBacking::GetGUID() const {
  return base::UnguessableToken();
}

MemoryBufferBacking::MemoryBufferBacking(uint32_t size, uint32_t alignment)
    : memory_(base::AlignedUninit<uint8_t>(size, alignment)) {}

MemoryBufferBacking::~MemoryBufferBacking() = default;

const void* MemoryBufferBacking::GetMemory() const {
  return memory_.data();
}

base::span<const uint8_t> MemoryBufferBacking::as_byte_span() const {
  return memory_.as_span();
}
uint32_t MemoryBufferBacking::GetSize() const {
  return memory_.size();
}

SharedMemoryBufferBacking::SharedMemoryBufferBacking(
    base::UnsafeSharedMemoryRegion shared_memory_region,
    base::WritableSharedMemoryMapping shared_memory_mapping)
    : shared_memory_region_(std::move(shared_memory_region)),
      shared_memory_mapping_(std::move(shared_memory_mapping)) {
  DCHECK_EQ(shared_memory_region_.GetGUID(), shared_memory_mapping_.guid());
  DCHECK_LE(shared_memory_mapping_.size(), static_cast<size_t>(UINT32_MAX));
}

SharedMemoryBufferBacking::~SharedMemoryBufferBacking() = default;

const base::UnsafeSharedMemoryRegion&
SharedMemoryBufferBacking::shared_memory_region() const {
  return shared_memory_region_;
}

base::UnguessableToken SharedMemoryBufferBacking::GetGUID() const {
  return shared_memory_region_.GetGUID();
}

const void* SharedMemoryBufferBacking::GetMemory() const {
  return shared_memory_mapping_.memory();
}

base::span<const uint8_t> SharedMemoryBufferBacking::as_byte_span() const {
  return base::span(shared_memory_mapping_);
}

uint32_t SharedMemoryBufferBacking::GetSize() const {
  return static_cast<uint32_t>(shared_memory_mapping_.size());
}

Buffer::Buffer(std::unique_ptr<BufferBacking> backing)
    : backing_(std::move(backing)) {
  DCHECK(!backing_->as_byte_span().empty())
      << "The memory must be mapped to create a Buffer";
}

Buffer::~Buffer() = default;

void* Buffer::GetDataAddress(uint32_t data_offset, uint32_t data_size) const {
  base::CheckedNumeric<uint32_t> end = data_offset;
  end += data_size;
  if (!end.IsValid() || end.ValueOrDie() > size()) {
    return nullptr;
  }
  return backing_->as_byte_span().subspan(data_offset, data_size).data();
}

void* Buffer::GetDataAddressAndSize(uint32_t data_offset,
                                    uint32_t* data_size) const {
  if (data_offset > size()) {
    return nullptr;
  }
  *data_size = GetRemainingSize(data_offset);
  return backing_->as_byte_span().subspan(data_offset, *data_size).data();
}

uint32_t Buffer::GetRemainingSize(uint32_t data_offset) const {
  if (data_offset > size()) {
    return 0;
  }
  return size() - data_offset;
}

int32_t GetNextBufferId() {
  // 0 is a reserved value.
  return g_next_buffer_id.GetNext() + 1;
}

base::trace_event::MemoryAllocatorDumpGuid GetBufferGUIDForTracing(
    uint64_t tracing_process_id,
    int32_t buffer_id) {
  return base::trace_event::MemoryAllocatorDumpGuid(base::StringPrintf(
      "gpu-buffer-x-process/%" PRIx64 "/%d", tracing_process_id, buffer_id));
}

} // namespace gpu