1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. 2 // Use of this source code is governed by a BSD-style license that can be 3 // found in the LICENSE file. 4 5 #ifndef MEDIA_MP4_OFFSET_BYTE_QUEUE_H_ 6 #define MEDIA_MP4_OFFSET_BYTE_QUEUE_H_ 7 8 #include "base/basictypes.h" 9 #include "media/base/byte_queue.h" 10 #include "media/base/media_export.h" 11 12 namespace media { 13 14 // A wrapper around a ByteQueue which maintains a notion of a 15 // monotonically-increasing offset. All buffer access is done by passing these 16 // offsets into this class, going some way towards preventing the proliferation 17 // of many different meanings of "offset", "head", etc. 18 class MEDIA_EXPORT OffsetByteQueue { 19 public: 20 OffsetByteQueue(); 21 ~OffsetByteQueue(); 22 23 // These work like their underlying ByteQueue counterparts. 24 void Reset(); 25 void Push(const uint8* buf, int size); 26 void Peek(const uint8** buf, int* size); 27 void Pop(int count); 28 29 // Sets |buf| to point at the first buffered byte corresponding to |offset|, 30 // and |size| to the number of bytes available starting from that offset. 31 // 32 // It is an error if the offset is before the current head. It's not an error 33 // if the current offset is beyond tail(), but you will of course get back 34 // a null |buf| and a |size| of zero. 35 void PeekAt(int64 offset, const uint8** buf, int* size); 36 37 // Marks the bytes up to (but not including) |max_offset| as ready for 38 // deletion. This is relatively inexpensive, but will not necessarily reduce 39 // the resident buffer size right away (or ever). 40 // 41 // Returns true if the full range of bytes were successfully trimmed, 42 // including the case where |max_offset| is less than the current head. 43 // Returns false if |max_offset| > tail() (although all bytes currently 44 // buffered are still cleared). 45 bool Trim(int64 max_offset); 46 47 // The head and tail positions, in terms of the file's absolute offsets. 48 // tail() is an exclusive bound. 49 int64 head() { return head_; } 50 int64 tail() { return head_ + size_; } 51 52 private: 53 // Synchronize |buf_| and |size_| with |queue_|. 54 void Sync(); 55 56 ByteQueue queue_; 57 const uint8* buf_; 58 int size_; 59 int64 head_; 60 61 DISALLOW_COPY_AND_ASSIGN(OffsetByteQueue); 62 }; 63 64 } // namespace media 65 66 #endif // MEDIA_MP4_MP4_STREAM_PARSER_H_ 67
