// 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_COMMON_OFFSET_BYTE_QUEUE_H_
#define MEDIA_FORMATS_COMMON_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_COMMON_OFFSET_BYTE_QUEUE_H_