media/base/audio_fifo.h

   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_