media/base/byte_queue.cc

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/base/byte_queue.h"

#include "base/logging.h"

namespace media {

// Default starting size for the queue.
enum { kDefaultQueueSize = 1024 };

ByteQueue::ByteQueue()
    : buffer_(new uint8_t[kDefaultQueueSize]),
      size_(kDefaultQueueSize),
      offset_(0),
      used_(0) {}

ByteQueue::~ByteQueue() = default;

void ByteQueue::Reset() {
  offset_ = 0;
  used_ = 0;
}

void ByteQueue::Push(const uint8_t* data, int size) {
  DCHECK(data);
  DCHECK_GT(size, 0);

  size_t size_needed = used_ + size;

  // Check to see if we need a bigger buffer.
  if (size_needed > size_) {
    size_t new_size = 2 * size_;
    while (size_needed > new_size && new_size > size_)
      new_size *= 2;

    // Sanity check to make sure we didn't overflow.
    CHECK_GT(new_size, size_);

    std::unique_ptr<uint8_t[]> new_buffer(new uint8_t[new_size]);

    // Copy the data from the old buffer to the start of the new one.
    if (used_ > 0)
      memcpy(new_buffer.get(), front(), used_);

    buffer_ = std::move(new_buffer);
    size_ = new_size;
    offset_ = 0;
  } else if ((offset_ + used_ + size) > size_) {
    // The buffer is big enough, but we need to move the data in the queue.
    memmove(buffer_.get(), front(), used_);
    offset_ = 0;
  }

  memcpy(front() + used_, data, size);
  used_ += size;
}

void ByteQueue::Peek(const uint8_t** data, int* size) const {
  DCHECK(data);
  DCHECK(size);
  *data = front();
  *size = used_;
}

void ByteQueue::Pop(int count) {
  DCHECK_LE(count, used_);

  offset_ += count;
  used_ -= count;

  // Move the offset back to 0 if we have reached the end of the buffer.
  if (offset_ == size_) {
    DCHECK_EQ(used_, 0);
    offset_ = 0;
  }
}

uint8_t* ByteQueue::front() const {
  return buffer_.get() + offset_;
}

}  // namespace media