C++ AudioBuffer::zero方法代码示例

void JavaScriptAudioNode::process(size_t framesToProcess)
{
    // Discussion about inputs and outputs:
    // As in other AudioNodes, JavaScriptAudioNode uses an AudioBus for its input and output (see inputBus and outputBus below).
    // Additionally, there is a double-buffering for input and output which is exposed directly to JavaScript (see inputBuffer and outputBuffer below).
    // This node is the producer for inputBuffer and the consumer for outputBuffer.
    // The JavaScript code is the consumer of inputBuffer and the producer for outputBuffer.
    
    // Get input and output busses.
    AudioBus* inputBus = this->input(0)->bus();
    AudioBus* outputBus = this->output(0)->bus();

    // Get input and output buffers.  We double-buffer both the input and output sides.
    unsigned doubleBufferIndex = this->doubleBufferIndex();
    bool isDoubleBufferIndexGood = doubleBufferIndex < 2 && doubleBufferIndex < m_inputBuffers.size() && doubleBufferIndex < m_outputBuffers.size();
    ASSERT(isDoubleBufferIndexGood);
    if (!isDoubleBufferIndexGood)
        return;
    
    AudioBuffer* inputBuffer = m_inputBuffers[doubleBufferIndex].get();
    AudioBuffer* outputBuffer = m_outputBuffers[doubleBufferIndex].get();

    // Check the consistency of input and output buffers.
    unsigned numberOfInputChannels = m_internalInputBus.numberOfChannels();
    bool buffersAreGood = outputBuffer && bufferSize() == outputBuffer->length() && m_bufferReadWriteIndex + framesToProcess <= bufferSize();

    // If the number of input channels is zero, it's ok to have inputBuffer = 0.
    if (m_internalInputBus.numberOfChannels())
        buffersAreGood = buffersAreGood && inputBuffer && bufferSize() == inputBuffer->length();

    ASSERT(buffersAreGood);
    if (!buffersAreGood)
        return;

    // We assume that bufferSize() is evenly divisible by framesToProcess - should always be true, but we should still check.
    bool isFramesToProcessGood = framesToProcess && bufferSize() >= framesToProcess && !(bufferSize() % framesToProcess);
    ASSERT(isFramesToProcessGood);
    if (!isFramesToProcessGood)
        return;

    unsigned numberOfOutputChannels = outputBus->numberOfChannels();

    bool channelsAreGood = (numberOfInputChannels == m_numberOfInputChannels) && (numberOfOutputChannels == m_numberOfOutputChannels);
    ASSERT(channelsAreGood);
    if (!channelsAreGood)
        return;

    for (unsigned i = 0; i < numberOfInputChannels; i++)
        m_internalInputBus.setChannelMemory(i, inputBuffer->getChannelData(i)->data() + m_bufferReadWriteIndex, framesToProcess);

    if (numberOfInputChannels)
        m_internalInputBus.copyFrom(*inputBus);

    // Copy from the output buffer to the output. 
    for (unsigned i = 0; i < numberOfOutputChannels; ++i)
        memcpy(outputBus->channel(i)->mutableData(), outputBuffer->getChannelData(i)->data() + m_bufferReadWriteIndex, sizeof(float) * framesToProcess);

    // Update the buffering index.
    m_bufferReadWriteIndex = (m_bufferReadWriteIndex + framesToProcess) % bufferSize();

    // m_bufferReadWriteIndex will wrap back around to 0 when the current input and output buffers are full.
    // When this happens, fire an event and swap buffers.
    if (!m_bufferReadWriteIndex) {
        // Avoid building up requests on the main thread to fire process events when they're not being handled.
        // This could be a problem if the main thread is very busy doing other things and is being held up handling previous requests.
        if (m_isRequestOutstanding) {
            // We're late in handling the previous request.  The main thread must be very busy.
            // The best we can do is clear out the buffer ourself here.
            outputBuffer->zero();            
        } else {
            // Reference ourself so we don't accidentally get deleted before fireProcessEvent() gets called.
            ref();
            
            // Fire the event on the main thread, not this one (which is the realtime audio thread).
            m_doubleBufferIndexForEvent = m_doubleBufferIndex;
            m_isRequestOutstanding = true;
            callOnMainThread(fireProcessEventDispatch, this);
        }

        swapBuffers();
    }
}

void ScriptProcessorHandler::process(size_t framesToProcess)
{
    // Discussion about inputs and outputs:
    // As in other AudioNodes, ScriptProcessorNode uses an AudioBus for its input and output (see inputBus and outputBus below).
    // Additionally, there is a double-buffering for input and output which is exposed directly to JavaScript (see inputBuffer and outputBuffer below).
    // This node is the producer for inputBuffer and the consumer for outputBuffer.
    // The JavaScript code is the consumer of inputBuffer and the producer for outputBuffer.

    // Get input and output busses.
    AudioBus* inputBus = input(0).bus();
    AudioBus* outputBus = output(0).bus();

    // Get input and output buffers. We double-buffer both the input and output sides.
    unsigned doubleBufferIndex = this->doubleBufferIndex();
    bool isDoubleBufferIndexGood = doubleBufferIndex < 2 && doubleBufferIndex < m_inputBuffers.size() && doubleBufferIndex < m_outputBuffers.size();
    ASSERT(isDoubleBufferIndexGood);
    if (!isDoubleBufferIndexGood)
        return;

    AudioBuffer* inputBuffer = m_inputBuffers[doubleBufferIndex].get();
    AudioBuffer* outputBuffer = m_outputBuffers[doubleBufferIndex].get();

    // Check the consistency of input and output buffers.
    unsigned numberOfInputChannels = m_internalInputBus->numberOfChannels();
    bool buffersAreGood = outputBuffer && bufferSize() == outputBuffer->length() && m_bufferReadWriteIndex + framesToProcess <= bufferSize();

    // If the number of input channels is zero, it's ok to have inputBuffer = 0.
    if (m_internalInputBus->numberOfChannels())
        buffersAreGood = buffersAreGood && inputBuffer && bufferSize() == inputBuffer->length();

    ASSERT(buffersAreGood);
    if (!buffersAreGood)
        return;

    // We assume that bufferSize() is evenly divisible by framesToProcess - should always be true, but we should still check.
    bool isFramesToProcessGood = framesToProcess && bufferSize() >= framesToProcess && !(bufferSize() % framesToProcess);
    ASSERT(isFramesToProcessGood);
    if (!isFramesToProcessGood)
        return;

    unsigned numberOfOutputChannels = outputBus->numberOfChannels();

    bool channelsAreGood = (numberOfInputChannels == m_numberOfInputChannels) && (numberOfOutputChannels == m_numberOfOutputChannels);
    ASSERT(channelsAreGood);
    if (!channelsAreGood)
        return;

    for (unsigned i = 0; i < numberOfInputChannels; ++i)
        m_internalInputBus->setChannelMemory(i, inputBuffer->getChannelData(i)->data() + m_bufferReadWriteIndex, framesToProcess);

    if (numberOfInputChannels)
        m_internalInputBus->copyFrom(*inputBus);

    // Copy from the output buffer to the output.
    for (unsigned i = 0; i < numberOfOutputChannels; ++i)
        memcpy(outputBus->channel(i)->mutableData(), outputBuffer->getChannelData(i)->data() + m_bufferReadWriteIndex, sizeof(float) * framesToProcess);

    // Update the buffering index.
    m_bufferReadWriteIndex = (m_bufferReadWriteIndex + framesToProcess) % bufferSize();

    // m_bufferReadWriteIndex will wrap back around to 0 when the current input and output buffers are full.
    // When this happens, fire an event and swap buffers.
    if (!m_bufferReadWriteIndex) {
        // Avoid building up requests on the main thread to fire process events when they're not being handled.
        // This could be a problem if the main thread is very busy doing other things and is being held up handling previous requests.
        // The audio thread can't block on this lock, so we call tryLock() instead.
        MutexTryLocker tryLocker(m_processEventLock);
        if (!tryLocker.locked()) {
            // We're late in handling the previous request. The main thread must be very busy.
            // The best we can do is clear out the buffer ourself here.
            outputBuffer->zero();
        } else if (context()->executionContext()) {
            // Fire the event on the main thread, not this one (which is the realtime audio thread).
            m_doubleBufferIndexForEvent = m_doubleBufferIndex;
            context()->executionContext()->postTask(BLINK_FROM_HERE, createCrossThreadTask(&ScriptProcessorHandler::fireProcessEvent, PassRefPtr<ScriptProcessorHandler>(this)));
        }

        swapBuffers();
    }
}

void ScriptProcessorHandler::process(size_t framesToProcess) {
  // Discussion about inputs and outputs:
  // As in other AudioNodes, ScriptProcessorNode uses an AudioBus for its input
  // and output (see inputBus and outputBus below).  Additionally, there is a
  // double-buffering for input and output which is exposed directly to
  // JavaScript (see inputBuffer and outputBuffer below).  This node is the
  // producer for inputBuffer and the consumer for outputBuffer.  The JavaScript
  // code is the consumer of inputBuffer and the producer for outputBuffer.

  // Get input and output busses.
  AudioBus* inputBus = input(0).bus();
  AudioBus* outputBus = output(0).bus();

  // Get input and output buffers. We double-buffer both the input and output
  // sides.
  unsigned doubleBufferIndex = this->doubleBufferIndex();
  bool isDoubleBufferIndexGood = doubleBufferIndex < 2 &&
                                 doubleBufferIndex < m_inputBuffers.size() &&
                                 doubleBufferIndex < m_outputBuffers.size();
  DCHECK(isDoubleBufferIndexGood);
  if (!isDoubleBufferIndexGood)
    return;

  AudioBuffer* inputBuffer = m_inputBuffers[doubleBufferIndex].get();
  AudioBuffer* outputBuffer = m_outputBuffers[doubleBufferIndex].get();

  // Check the consistency of input and output buffers.
  unsigned numberOfInputChannels = m_internalInputBus->numberOfChannels();
  bool buffersAreGood =
      outputBuffer && bufferSize() == outputBuffer->length() &&
      m_bufferReadWriteIndex + framesToProcess <= bufferSize();

  // If the number of input channels is zero, it's ok to have inputBuffer = 0.
  if (m_internalInputBus->numberOfChannels())
    buffersAreGood =
        buffersAreGood && inputBuffer && bufferSize() == inputBuffer->length();

  DCHECK(buffersAreGood);
  if (!buffersAreGood)
    return;

  // We assume that bufferSize() is evenly divisible by framesToProcess - should
  // always be true, but we should still check.
  bool isFramesToProcessGood = framesToProcess &&
                               bufferSize() >= framesToProcess &&
                               !(bufferSize() % framesToProcess);
  DCHECK(isFramesToProcessGood);
  if (!isFramesToProcessGood)
    return;

  unsigned numberOfOutputChannels = outputBus->numberOfChannels();

  bool channelsAreGood = (numberOfInputChannels == m_numberOfInputChannels) &&
                         (numberOfOutputChannels == m_numberOfOutputChannels);
  DCHECK(channelsAreGood);
  if (!channelsAreGood)
    return;

  for (unsigned i = 0; i < numberOfInputChannels; ++i)
    m_internalInputBus->setChannelMemory(
        i, inputBuffer->getChannelData(i)->data() + m_bufferReadWriteIndex,
        framesToProcess);

  if (numberOfInputChannels)
    m_internalInputBus->copyFrom(*inputBus);

  // Copy from the output buffer to the output.
  for (unsigned i = 0; i < numberOfOutputChannels; ++i)
    memcpy(outputBus->channel(i)->mutableData(),
           outputBuffer->getChannelData(i)->data() + m_bufferReadWriteIndex,
           sizeof(float) * framesToProcess);

  // Update the buffering index.
  m_bufferReadWriteIndex =
      (m_bufferReadWriteIndex + framesToProcess) % bufferSize();

  // m_bufferReadWriteIndex will wrap back around to 0 when the current input
  // and output buffers are full.
  // When this happens, fire an event and swap buffers.
  if (!m_bufferReadWriteIndex) {
    // Avoid building up requests on the main thread to fire process events when
    // they're not being handled.  This could be a problem if the main thread is
    // very busy doing other things and is being held up handling previous
    // requests.  The audio thread can't block on this lock, so we call
    // tryLock() instead.
    MutexTryLocker tryLocker(m_processEventLock);
    if (!tryLocker.locked()) {
      // We're late in handling the previous request. The main thread must be
      // very busy.  The best we can do is clear out the buffer ourself here.
      outputBuffer->zero();
    } else if (context()->getExecutionContext()) {
      // With the realtime context, execute the script code asynchronously
      // and do not wait.
      if (context()->hasRealtimeConstraint()) {
        // Fire the event on the main thread with the appropriate buffer
        // index.
        context()->getExecutionContext()->postTask(
            BLINK_FROM_HERE,
            createCrossThreadTask(&ScriptProcessorHandler::fireProcessEvent,
                                  crossThreadUnretained(this),
//.........这里部分代码省略.........