third_party/WebKit/Source/platform/audio/AudioPullFIFO.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
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#ifndef AudioPullFIFO_h
#define AudioPullFIFO_h

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

namespace blink {

// A FIFO (First In First Out) buffer to handle mismatches in buffer sizes
// between a provider and receiver. The receiver will "pull" data from this
// FIFO. If data is already available in the FIFO, it is provided to the
// receiver. If insufficient data is available to satisfy the request, the FIFO
// will ask the provider for more data when necessary to fulfill a request.
// Contrast this with a "push" FIFO, where the sender pushes data to the FIFO
// which will itself push the data to the receiver when the FIFO is full.
class PLATFORM_EXPORT AudioPullFIFO {
  USING_FAST_MALLOC(AudioPullFIFO);
  WTF_MAKE_NONCOPYABLE(AudioPullFIFO);

 public:
  // Create a FIFO that gets data from |provider|. The FIFO will be large
  // enough to hold |fifoLength| frames of data of |numberOfChannels| channels.
  // The AudioSourceProvider will be asked to produce |providerSize| frames
  // when the FIFO needs more data.
  AudioPullFIFO(AudioSourceProvider& audioProvider,
                unsigned numberOfChannels,
                size_t fifoLength,
                size_t providerSize);

  // Read |framesToConsume| frames from the FIFO into the destination. If the
  // FIFO does not have enough data, we ask the |provider| to get more data to
  // fulfill the request.
  void consume(AudioBus* destination, size_t framesToConsume);

 private:
  // Fill the FIFO buffer with at least |numberOfFrames| more data.
  void fillBuffer(size_t numberOfFrames);

  // The provider of the data in our FIFO.
  AudioSourceProvider& m_provider;

  // The actual FIFO
  AudioFIFO m_fifo;

  // Number of frames of data that the provider will produce per call.
  unsigned m_providerSize;

  // Temporary workspace to hold the data from the provider.
  RefPtr<AudioBus> m_tempBus;
};

}  // namespace blink

#endif  // AudioPullFIFO.h