Move offset_byte_queue.* from media/mp4 to media/common.

media/formats/mp4/offset_byte_queue.h

-// 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.
-
-#ifndef MEDIA_FORMATS_MP4_OFFSET_BYTE_QUEUE_H_
-#define MEDIA_FORMATS_MP4_OFFSET_BYTE_QUEUE_H_
-
-#include "base/basictypes.h"
-#include "media/base/byte_queue.h"
-#include "media/base/media_export.h"
-
-namespace media {
-
-// A wrapper around a ByteQueue which maintains a notion of a
-// monotonically-increasing offset. All buffer access is done by passing these
-// offsets into this class, going some way towards preventing the proliferation
-// of many different meanings of "offset", "head", etc.
-class MEDIA_EXPORT OffsetByteQueue {
- public:
-  OffsetByteQueue();
-  ~OffsetByteQueue();
-
-  // These work like their underlying ByteQueue counterparts.
-  void Reset();
-  void Push(const uint8* buf, int size);
-  void Peek(const uint8** buf, int* size);
-  void Pop(int count);
-
-  // Sets |buf| to point at the first buffered byte corresponding to |offset|,
-  // and |size| to the number of bytes available starting from that offset.
-  //
-  // It is an error if the offset is before the current head. It's not an error
-  // if the current offset is beyond tail(), but you will of course get back
-  // a null |buf| and a |size| of zero.
-  void PeekAt(int64 offset, const uint8** buf, int* size);
-
-  // Marks the bytes up to (but not including) |max_offset| as ready for
-  // deletion. This is relatively inexpensive, but will not necessarily reduce
-  // the resident buffer size right away (or ever).
-  //
-  // Returns true if the full range of bytes were successfully trimmed,
-  // including the case where |max_offset| is less than the current head.
-  // Returns false if |max_offset| > tail() (although all bytes currently
-  // buffered are still cleared).
-  bool Trim(int64 max_offset);
-
-  // The head and tail positions, in terms of the file's absolute offsets.
-  // tail() is an exclusive bound.
-  int64 head() { return head_; }
-  int64 tail() { return head_ + size_; }
-
- private:
-  // Synchronize |buf_| and |size_| with |queue_|.
-  void Sync();
-
-  ByteQueue queue_;
-  const uint8* buf_;
-  int size_;
-  int64 head_;
-
-  DISALLOW_COPY_AND_ASSIGN(OffsetByteQueue);
-};
-
-}  // namespace media
-
-#endif  // MEDIA_FORMATS_MP4_MP4_STREAM_PARSER_H_