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

/*
 * 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.
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 *     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
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 */

#include "platform/audio/AudioFIFO.h"

namespace blink {

AudioFIFO::AudioFIFO(unsigned numberOfChannels, size_t fifoLength)
    : m_fifoAudioBus(AudioBus::create(numberOfChannels, fifoLength)),
      m_fifoLength(fifoLength),
      m_framesInFifo(0),
      m_readIndex(0),
      m_writeIndex(0) {}

void AudioFIFO::consume(AudioBus* destination, size_t framesToConsume) {
  bool isGood = destination && (framesToConsume <= m_fifoLength) &&
                (framesToConsume <= m_framesInFifo) &&
                (destination->length() >= framesToConsume);
  ASSERT(isGood);
  if (!isGood)
    return;

  // Copy the requested number of samples to the destination.

  size_t part1Length;
  size_t part2Length;
  findWrapLengths(m_readIndex, framesToConsume, part1Length, part2Length);

  size_t numberOfChannels = m_fifoAudioBus->numberOfChannels();

  for (size_t channelIndex = 0; channelIndex < numberOfChannels;
       ++channelIndex) {
    float* destinationData = destination->channel(channelIndex)->mutableData();
    const float* sourceData = m_fifoAudioBus->channel(channelIndex)->data();

    bool isCopyGood = ((m_readIndex < m_fifoLength) &&
                       (m_readIndex + part1Length) <= m_fifoLength &&
                       (part1Length <= destination->length()) &&
                       (part1Length + part2Length) <= destination->length());
    ASSERT(isCopyGood);
    if (!isCopyGood)
      return;

    memcpy(destinationData, sourceData + m_readIndex,
           part1Length * sizeof(*sourceData));
    // Handle wrap around of the FIFO, if needed.
    if (part2Length)
      memcpy(destinationData + part1Length, sourceData,
             part2Length * sizeof(*sourceData));
  }
  m_readIndex = updateIndex(m_readIndex, framesToConsume);
  ASSERT(m_framesInFifo >= framesToConsume);
  m_framesInFifo -= framesToConsume;
}

void AudioFIFO::push(const AudioBus* sourceBus) {
  // Copy the sourceBus into the FIFO buffer.

  bool isGood =
      sourceBus && (m_framesInFifo + sourceBus->length() <= m_fifoLength);
  if (!isGood)
    return;

  size_t sourceLength = sourceBus->length();
  size_t part1Length;
  size_t part2Length;
  findWrapLengths(m_writeIndex, sourceLength, part1Length, part2Length);

  size_t numberOfChannels = m_fifoAudioBus->numberOfChannels();

  for (size_t channelIndex = 0; channelIndex < numberOfChannels;
       ++channelIndex) {
    float* destination = m_fifoAudioBus->channel(channelIndex)->mutableData();
    const float* source = sourceBus->channel(channelIndex)->data();

    bool isCopyGood = ((m_writeIndex < m_fifoLength) &&
                       (m_writeIndex + part1Length) <= m_fifoLength &&
                       part2Length < m_fifoLength &&
                       part1Length + part2Length <= sourceLength);
    ASSERT(isCopyGood);
    if (!isCopyGood)
      return;

    memcpy(destination + m_writeIndex, source,
           part1Length * sizeof(*destination));

    // Handle wrap around of the FIFO, if needed.
    if (part2Length)
      memcpy(destination, source + part1Length,
             part2Length * sizeof(*destination));
  }

  m_framesInFifo += sourceLength;
  ASSERT(m_framesInFifo <= m_fifoLength);
  m_writeIndex = updateIndex(m_writeIndex, sourceLength);
}

void AudioFIFO::findWrapLengths(size_t index,
                                size_t size,
                                size_t& part1Length,
                                size_t& part2Length) {
  SECURITY_DCHECK(index < m_fifoLength && size <= m_fifoLength);
  if (index < m_fifoLength && size <= m_fifoLength) {
    if (index + size > m_fifoLength) {
      // Need to wrap. Figure out the length of each piece.
      part1Length = m_fifoLength - index;
      part2Length = size - part1Length;
    } else {
      // No wrap needed.
      part1Length = size;
      part2Length = 0;
    }
  } else {
    // Invalid values for index or size. Set the part lengths to zero so nothing
    // is copied.
    part1Length = 0;
    part2Length = 0;
  }
}

}  // namespace blink