text: // Copyright 2014 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 "mp4/offset_byte_queue.h"
  
  #include "base/logging.h"
  
  namespace media {
  
  OffsetByteQueue::OffsetByteQueue() : buf_(NULL), size_(0), head_(0) {}
  OffsetByteQueue::~OffsetByteQueue() {}
  
  void OffsetByteQueue::Reset() {
    queue_.Reset();
    buf_ = NULL;
    size_ = 0;
    head_ = 0;
  }
  
  void OffsetByteQueue::Push(const uint8_t* buf, int size) {
    queue_.Push(buf, size);
    Sync();
    DVLOG(4) << "Buffer pushed. head=" << head() << " tail=" << tail();
  }
  
  void OffsetByteQueue::Peek(const uint8_t** buf, int* size) {
    *buf = size_ > 0 ? buf_ : NULL;
    *size = size_;
  }
  
  void OffsetByteQueue::Pop(int count) {
    queue_.Pop(count);
    head_ += count;
    Sync();
  }
  
  void OffsetByteQueue::PeekAt(int64_t offset, const uint8_t** buf, int* size) {
    DCHECK(offset >= head());
    if (offset < head() || offset >= tail()) {
      *buf = NULL;
      *size = 0;
      return;
    }
    *buf = &buf_[offset - head()];
    *size = tail() - offset;
  }
  
  bool OffsetByteQueue::Trim(int64_t max_offset) {
    if (max_offset < head_) return true;
    if (max_offset > tail()) {
      Pop(size_);
      return false;
    }
    Pop(max_offset - head_);
    return true;
  }
  
  void OffsetByteQueue::Sync() {
    queue_.Peek(&buf_, &size_);
  }
  
  }  // namespace media
  