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_BASE_AUDIO_FIFO_H_ 6 #define MEDIA_BASE_AUDIO_FIFO_H_ 7 8 #include "base/atomicops.h" 9 #include "media/base/audio_bus.h" 10 #include "media/base/media_export.h" 11 12 namespace media { 13 14 // First-in first-out container for AudioBus elements. 15 // The maximum number of audio frames in the FIFO is set at construction and 16 // can not be extended dynamically. The allocated memory is utilized as a 17 // ring buffer. 18 // This class is thread-safe in the limited sense that one thread may call 19 // Push(), while a second thread calls Consume(). 20 class MEDIA_EXPORT AudioFifo { 21 public: 22 // Creates a new AudioFifo and allocates |channels| of length |frames|. 23 AudioFifo(int channels, int frames); 24 virtual ~AudioFifo(); 25 26 // Pushes all audio channel data from |source| to the FIFO. 27 // Push() will crash if the allocated space is insufficient. 28 void Push(const AudioBus* source); 29 30 // Consumes |frames_to_consume| audio frames from the FIFO and copies 31 // them to |destination| starting at position |start_frame|. 32 // Consume() will crash if the FIFO does not contain |frames_to_consume| 33 // frames or if there is insufficient space in |destination| to store the 34 // frames. 35 void Consume(AudioBus* destination, int start_frame, int frames_to_consume); 36 37 // Empties the FIFO without deallocating any memory. 38 void Clear(); 39 40 // Number of actual audio frames in the FIFO. 41 int frames() const; 42 43 int max_frames() const { return max_frames_; } 44 45 private: 46 // The actual FIFO is an audio bus implemented as a ring buffer. 47 scoped_ptr<AudioBus> audio_bus_; 48 49 // Maximum number of elements the FIFO can contain. 50 // This value is set by |frames| in the constructor. 51 const int max_frames_; 52 53 // Number of actual elements in the FIFO. 54 volatile base::subtle::Atomic32 frames_pushed_; 55 volatile base::subtle::Atomic32 frames_consumed_; 56 57 // Current read position. 58 int read_pos_; 59 60 // Current write position. 61 int write_pos_; 62 63 DISALLOW_COPY_AND_ASSIGN(AudioFifo); 64 }; 65 66 } // namespace media 67 68 #endif // MEDIA_BASE_AUDIO_FIFO_H_ 69
