Add a block based Audio FIFO.

media/base/audio_block_fifo.h

Index: media/base/audio_block_fifo.h
diff --git a/media/base/audio_block_fifo.h b/media/base/audio_block_fifo.h
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+++ b/media/base/audio_block_fifo.h
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+// Copyright 2014 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_BLOCK_FIFO_H_
+#define MEDIA_BASE_AUDIO_BLOCK_FIFO_H_
+
+#include "base/memory/scoped_vector.h"
+#include "media/base/audio_bus.h"
+#include "media/base/media_export.h"
+
+namespace media {
+
+// First-in first-out container for AudioBus elements.
+// The FIFO is composed of blocks of AudioBus elements, it accepts interleaved
+// data as input and will deinterleave it into the FIFO, and it only allows
+// consuming a whole block of AudioBus element.
+// This class is thread-unsafe.
+class MEDIA_EXPORT AudioBlockFifo {
+ public:
+  // Creates a new AudioBlockFifo and allocates |blocks| memory, each block
+  // of memory can store |channels| of length |frames| data.
+  AudioBlockFifo(int channels, int frames, int blocks);
+  virtual ~AudioBlockFifo();
+
+  // Pushes interleaved audio data from |source| to the FIFO.
+  // The method will deinterleave the data into a audio bus.
+  // Push() will crash if the allocated space is insufficient.
+  void Push(const void* source, int frames, int bytes_per_sample);
+
+  // Consumes a block of audio from the FIFO.  Returns an AudioBus which
+  // contains the consumed audio data to avoid copying.
+  // Consume() will crash if the FIFO does not contain a block of data.
+  const AudioBus* Consume();
+
+  // Empties the FIFO without deallocating any memory.
+  void Clear();
+
+  // Number of available block of memory ready to be consumed in the FIFO.
+  int available_blocks() const { return available_blocks_; }
+
+  // Number of unfilled frames in the whole FIFO.
+  int GetUnfilledFrames() const;
+
+ private:
+  // The actual FIFO is a vector of audio buses.
+  ScopedVector<AudioBus> audio_blocks_;
+
+  // Maximum number of frames of data one block of memory can contain.
+  // This value is set by |frames| in the constructor.
+  const int block_frames_;
+
+  // Used to keep track which block of memory to be written.
+  int write_block_;
+
+  // Used to keep track which block of memory to be consumed.
+  int read_block_;
+
+  // Number of available blocks of memory to be consumed.
+  int available_blocks_;
+
+  // Current write position in the current written block.
+  int write_pos_;
+
+  DISALLOW_COPY_AND_ASSIGN(AudioBlockFifo);
+};
+
+}  // namespace media
+
+#endif  // MEDIA_BASE_AUDIO_BLOCK_FIFO_H_