67 lines
2.2 KiB
C
67 lines
2.2 KiB
C
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// Copyright (c) 2012 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef MEDIA_MP4_OFFSET_BYTE_QUEUE_H_
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#define MEDIA_MP4_OFFSET_BYTE_QUEUE_H_
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#include "base/basictypes.h"
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#include "media/base/byte_queue.h"
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#include "media/base/media_export.h"
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namespace media {
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// A wrapper around a ByteQueue which maintains a notion of a
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// monotonically-increasing offset. All buffer access is done by passing these
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// offsets into this class, going some way towards preventing the proliferation
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// of many different meanings of "offset", "head", etc.
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class MEDIA_EXPORT OffsetByteQueue {
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public:
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OffsetByteQueue();
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~OffsetByteQueue();
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// These work like their underlying ByteQueue counterparts.
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void Reset();
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void Push(const uint8* buf, int size);
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void Peek(const uint8** buf, int* size);
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void Pop(int count);
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// Sets |buf| to point at the first buffered byte corresponding to |offset|,
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// and |size| to the number of bytes available starting from that offset.
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//
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// It is an error if the offset is before the current head. It's not an error
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// if the current offset is beyond tail(), but you will of course get back
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// a null |buf| and a |size| of zero.
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void PeekAt(int64 offset, const uint8** buf, int* size);
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// Marks the bytes up to (but not including) |max_offset| as ready for
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// deletion. This is relatively inexpensive, but will not necessarily reduce
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// the resident buffer size right away (or ever).
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//
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// Returns true if the full range of bytes were successfully trimmed,
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// including the case where |max_offset| is less than the current head.
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// Returns false if |max_offset| > tail() (although all bytes currently
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// buffered are still cleared).
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bool Trim(int64 max_offset);
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// The head and tail positions, in terms of the file's absolute offsets.
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// tail() is an exclusive bound.
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int64 head() { return head_; }
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int64 tail() { return head_ + size_; }
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private:
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// Synchronize |buf_| and |size_| with |queue_|.
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void Sync();
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ByteQueue queue_;
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const uint8* buf_;
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int size_;
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int64 head_;
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DISALLOW_COPY_AND_ASSIGN(OffsetByteQueue);
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};
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} // namespace media
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#endif // MEDIA_MP4_MP4_STREAM_PARSER_H_
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