Implementation of 'AudioContext.getOutputTimestamp' method

third_party/WebKit/Source/modules/webaudio/AudioDestinationNode.cpp

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 #include "modules/webaudio/AudioDestinationNode.h"
+
 #include "modules/webaudio/AbstractAudioContext.h"
 #include "modules/webaudio/AudioNodeInput.h"
 #include "modules/webaudio/AudioNodeOutput.h"
 #include "platform/audio/AudioUtilities.h"
 #include "platform/audio/DenormalDisabler.h"
 #include "wtf/Atomics.h"
 
 namespace blink {
 
 AudioDestinationHandler::AudioDestinationHandler(AudioNode& node, float sampleRate)
     : AudioHandler(NodeTypeDestination, node, sampleRate)
     , m_currentSampleFrame(0)
 {
     addInput();
 }
 
 AudioDestinationHandler::~AudioDestinationHandler()
 {
     ASSERT(!isInitialized());
 }
 
-void AudioDestinationHandler::render(AudioBus* sourceBus, AudioBus* destinationBus, size_t numberOfFrames)
+void AudioDestinationHandler::render(AudioBus* sourceBus, AudioBus* destinationBus, size_t numberOfFrames, const WebAudioTimestamp& outputTimestamp)
 {
+    {
+        MutexLocker locker(m_mutex);

[Raymond Toy, 2016/06/14 16:42:40]

Can this be blocked by the main thread?  Generally, we use tryLocks to make sure
we don't block the audio thread.

[hongchan, 2016/06/14 17:10:38]

Consider to move this operation to context's pre-render task.

+        m_outputTimestamp = outputTimestamp;
+    }
+
     // We don't want denormals slowing down any of the audio processing
     // since they can very seriously hurt performance.
     // This will take care of all AudioNodes because they all process within this scope.
     DenormalDisabler denormalDisabler;
 
     // Need to check if the context actually alive. Otherwise the subsequent
     // steps will fail. If the context is not alive somehow, return immediately
     // and do nothing.
     //
     // TODO(hongchan): because the context can go away while rendering, so this
@@ skipping 39 matching lines @@
     context()->deferredTaskHandler().processAutomaticPullNodes(numberOfFrames);
 
     // Let the context take care of any business at the end of each render quantum.
     context()->handlePostRenderTasks();
 
     // Advance current sample-frame.
     size_t newSampleFrame = m_currentSampleFrame + numberOfFrames;
     releaseStore(&m_currentSampleFrame, newSampleFrame);
 }
 
+WebAudioTimestamp AudioDestinationHandler::outputTimestamp() const
+{
+    MutexLocker locker(m_mutex);

[hongchan, 2016/06/14 17:10:38]

This will block the audio thread when the mutex is enabled.

+    return m_outputTimestamp;
+}
+
 // ----------------------------------------------------------------
 
 AudioDestinationNode::AudioDestinationNode(AbstractAudioContext& context)
     : AudioNode(context)
 {
 }
 
 AudioDestinationHandler& AudioDestinationNode::audioDestinationHandler() const
 {
     return static_cast<AudioDestinationHandler&>(handler());
 }
 
 unsigned long AudioDestinationNode::maxChannelCount() const
 {
     return audioDestinationHandler().maxChannelCount();
 }
 
 } // namespace blink