Add a block based Audio FIFO.

media/base/audio_fifo.h

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef MEDIA_BASE_AUDIO_FIFO_H_
 #define MEDIA_BASE_AUDIO_FIFO_H_
 
 #include "media/base/audio_bus.h"
 #include "media/base/media_export.h"
 
 namespace media {
 
 // First-in first-out container for AudioBus elements.
 // The maximum number of audio frames in the FIFO is set at construction and
 // can not be extended dynamically.  The allocated memory is utilized as a
 // ring buffer.
 // This class is thread-unsafe.
 class MEDIA_EXPORT AudioFifo {
  public:
   // Creates a new AudioFifo and allocates |channels| of length |frames|.
   AudioFifo(int channels, int frames);
   virtual ~AudioFifo();
 
+  static void GetSizes(int pos, int max_size, int in_size, int* size,
+                       int* wrap_size);
+  static int UpdatePos(int pos, int step, int max_size);
+
   // Pushes all audio channel data from |source| to the FIFO.
   // Push() will crash if the allocated space is insufficient.
   void Push(const AudioBus* source);
 
   // Consumes |frames_to_consume| audio frames from the FIFO and copies
   // them to |destination| starting at position |start_frame|.
   // Consume() will crash if the FIFO does not contain |frames_to_consume|
   // frames or if there is insufficient space in |destination| to store the
   // frames.
   void Consume(AudioBus* destination, int start_frame, int frames_to_consume);
@@ skipping 23 matching lines @@
 
   // Current write position.
   int write_pos_;
 
   DISALLOW_COPY_AND_ASSIGN(AudioFifo);
 };
 
 }  // namespace media
 
 #endif  // MEDIA_BASE_AUDIO_FIFO_H_