third_party/WebKit/Source/platform/audio/AudioFIFO.h

/*
 * Copyright (C) 2012 Google Inc. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1.  Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 * 2.  Redistributions in binary form must reproduce the above copyright
 *     notice, this list of conditions and the following disclaimer in the
 *     documentation and/or other materials provided with the distribution.
 * 3.  Neither the name of Apple Computer, Inc. ("Apple") nor the names of
 *     its contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY APPLE AND ITS CONTRIBUTORS "AS IS" AND ANY
 * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL APPLE OR ITS CONTRIBUTORS BE LIABLE FOR ANY
 * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
 * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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 */

#ifndef AudioFIFO_h
#define AudioFIFO_h

#include "platform/audio/AudioBus.h"
#include "wtf/Allocator.h"

namespace blink {

class AudioFIFO {
  USING_FAST_MALLOC(AudioFIFO);
  WTF_MAKE_NONCOPYABLE(AudioFIFO);

 public:
  // Create a FIFO large enough to hold |fifoLength| frames of data of
  // |numberOfChannels| channels.
  AudioFIFO(unsigned numberOfChannels, size_t fifoLength);

  // Push the data from the bus into the FIFO.
  void push(const AudioBus*);

  // Consume |framesToConsume| frames of data from the FIFO and put them in
  // |destination|. The corresponding frames are removed from the FIFO.
  void consume(AudioBus* destination, size_t framesToConsume);

  // Number of frames of data that are currently in the FIFO.
  size_t framesInFifo() const { return m_framesInFifo; }

 private:
  // Update the FIFO index by the step, with appropriate wrapping around the
  // endpoint.
  int updateIndex(int index, int step) { return (index + step) % m_fifoLength; }

  void findWrapLengths(size_t index,
                       size_t providerSize,
                       size_t& part1Length,
                       size_t& part2Length);

  // The FIFO itself. In reality, the FIFO is a circular buffer.
  RefPtr<AudioBus> m_fifoAudioBus;

  // The total available space in the FIFO.
  size_t m_fifoLength;

  // The number of actual elements in the FIFO
  size_t m_framesInFifo;

  // Where to start reading from the FIFO.
  size_t m_readIndex;

  // Where to start writing to the FIFO.
  size_t m_writeIndex;
};

}  // namespace blink

#endif  // AudioFIFO.h