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