Adds AudioFifo class to Chrome media.

media/base/audio_fifo.h

Index: media/base/audio_fifo.h
diff --git a/media/base/audio_fifo.h b/media/base/audio_fifo.h
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+// 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.
+class MEDIA_EXPORT AudioFifo {
+ public:
+  // Creates a new AudioFifo and allocates |channels| of length |frames|.
+  AudioFifo(int channels, int frames);
+  virtual ~AudioFifo();
+
+  // Pushes all audio channel data from |source| to the FIFO.
+  // Returns false if the allocated space is not sufficient.  Partial data is
+  // not written to the FIFO for this overflow case.
+  bool Push(const AudioBus* source);
+
+  // Consumes |frames_to_consume| audio frames from the FIFO and copies
+  // them to |destination|.
+  // Returns false if the FIFO does not contain |frames_to_consume| frames
+  // or if there is not sufficient space in |destination| to store the frames.
+  bool Consume(AudioBus* destination, int frames_to_consume);
+
+  // Empties the FIFO without deallocating any memory.
+  void Clear();
+
+  // Number of actual audio frames in the FIFO.
+  int frames_in_fifo() const { return frames_in_fifo_; }
+
+ private:
+  int max_frames() const { return max_frames_in_fifo_; }
+
+  // The actual FIFO is an audio bus implemented as a ring buffer.
+  scoped_ptr<AudioBus> audio_bus_;
+
+  // Maximum number of elements the FIFO can contain.
+  // This value is set by |frames| in the constructor.
+  const int max_frames_in_fifo_;
+
+  // Number of actual elements in the FIFO.
+  int frames_in_fifo_;
+
+  // Current read position.
+  int read_pos_;
+
+  // Current write position.
+  int write_pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioFifo);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_FIFO_H_