Implement suspend/resume for AudioContext

Source/modules/webaudio/AudioContext.cpp

 /*
  * Copyright (C) 2010, 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
@@ skipping 12 matching lines @@
  */
 
 #include "config.h"
 
 #if ENABLE(WEB_AUDIO)
 
 #include "modules/webaudio/AudioContext.h"
 
 #include "bindings/core/v8/ExceptionMessages.h"
 #include "bindings/core/v8/ExceptionState.h"
+#include "bindings/core/v8/ScriptState.h"
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/html/HTMLMediaElement.h"
 #include "core/inspector/ScriptCallStack.h"
 #include "platform/audio/FFTFrame.h"
 #include "platform/audio/HRTFPanner.h"
 #include "modules/mediastream/MediaStream.h"
 #include "modules/webaudio/AnalyserNode.h"
 #include "modules/webaudio/AudioBuffer.h"
 #include "modules/webaudio/AudioBufferCallback.h"
@@ skipping 51 matching lines @@
     return audioContext;
 }
 
 // Constructor for rendering to the audio hardware.
 AudioContext::AudioContext(Document* document)
     : ActiveDOMObject(document)
     , m_isStopScheduled(false)
     , m_isCleared(false)
     , m_isInitialized(false)
     , m_destinationNode(nullptr)
+    , m_isResolvingResumePromises(false)
     , m_automaticPullNodesNeedUpdating(false)
     , m_connectionCount(0)
     , m_audioThread(0)
     , m_isOfflineContext(false)
 {
     m_destinationNode = DefaultAudioDestinationNode::create(this);
 
     initialize();
 #if DEBUG_AUDIONODE_REFERENCES
     fprintf(stderr, "%p: AudioContext::AudioContext() #%u\n", this, AudioContext::s_hardwareContextCount);
 #endif
 }
 
 // Constructor for offline (non-realtime) rendering.
 AudioContext::AudioContext(Document* document, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate)
     : ActiveDOMObject(document)
     , m_isStopScheduled(false)
     , m_isCleared(false)
     , m_isInitialized(false)
     , m_destinationNode(nullptr)
+    , m_isResolvingResumePromises(false)
     , m_automaticPullNodesNeedUpdating(false)
     , m_connectionCount(0)
     , m_audioThread(0)
     , m_isOfflineContext(true)
 {
     // Create a new destination for offline rendering.
     m_renderTarget = AudioBuffer::create(numberOfChannels, numberOfFrames, sampleRate);
     if (m_renderTarget.get())
         m_destinationNode = OfflineAudioDestinationNode::create(this, m_renderTarget.get());
 
@@ skipping 390 matching lines @@
         exceptionState.throwDOMException(
             IndexSizeError,
             "length of imaginary array (" + String::number(imag->length())
             + ") exceeds allowed maximum of 4096");
         return 0;
     }
 
     return PeriodicWave::create(sampleRate(), real, imag);
 }
 
+void AudioContext::suspendContext()
+{
+    ASSERT(isMainThread());
+    AutoLocker locker(this);
+
+    if (m_destinationNode && !isOfflineContext())
+        m_destinationNode->stop();
+}
+
+ScriptPromise AudioContext::resumeContext(ScriptState* scriptState)
+{
+    ASSERT(isMainThread());
+    AutoLocker locker(this);
+
+    RefPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+
+    ScriptPromise promise = resolver->promise();
+
+    if (isOfflineContext()) {
+        // For offline context, just resolve the promise now.
+        resolver->resolve();
+    } else {
+        // Restart the destination node to pull on the audio graph.
+        if (m_destinationNode)
+            m_destinationNode->startRendering();
+
+        // Save the promise which will get resolved when the destination node starts pulling on the
+        // graph again.
+        m_resumePromises.append(resolver);
+    }
+
+    return promise;
+}
+
 void AudioContext::notifyNodeFinishedProcessing(AudioNode* node)
 {
     ASSERT(isAudioThread());
     m_finishedNodes.append(node);
 }
 
 void AudioContext::derefFinishedSourceNodes()
 {
     ASSERT(isGraphOwner());
     ASSERT(isAudioThread());
@@ skipping 86 matching lines @@
     // It's OK if the tryLock() fails, we'll just take slightly longer to pick up the changes.
     if (tryLock()) {
         // Update the channel count mode.
         updateChangedChannelCountMode();
 
         // Fixup the state of any dirty AudioSummingJunctions and AudioNodeOutputs.
         handleDirtyAudioSummingJunctions();
         handleDirtyAudioNodeOutputs();
 
         updateAutomaticPullNodes();
+        resolvePromisesForResume();
+
         unlock();
     }
 }
 
 void AudioContext::handlePostRenderTasks()
 {
     ASSERT(isAudioThread());
 
     // Must use a tryLock() here too.  Don't worry, the lock will very rarely be contended and this method is called frequently.
     // The worst that can happen is that there will be some nodes which will take slightly longer than usual to be deleted or removed
@@ skipping 145 matching lines @@
 }
 
 void AudioContext::processAutomaticPullNodes(size_t framesToProcess)
 {
     ASSERT(isAudioThread());
 
     for (unsigned i = 0; i < m_renderingAutomaticPullNodes.size(); ++i)
         m_renderingAutomaticPullNodes[i]->processIfNecessary(framesToProcess);
 }
 
+void AudioContext::resolvePromisesForResumeOnMainThread()
+{
+    ASSERT(isMainThread);

[yhirano, 2014/10/08 01:12:14]

Please acquire the lock.

[yhirano, 2014/10/08 01:15:54]

Oh, I found AudioContext::lock is not callable from the main thread. You need to
protect shared member variables though. Maybe manipulating these variables in
the audio thread and passing them to this function via parameters works?

[Raymond Toy, 2014/10/14 17:16:59]

Done.

+
+    for (unsigned k = 0; k < m_resumePromises.size(); ++k)
+        m_resumePromises[k]->resolve();
+
+    m_resumePromises.clear();
+    m_isResolvingResumePromises = false;
+}
+
+void AudioContext::resolvePromisesForResume()
+{
+    ASSERT(isAudioThread());
+

[yhirano, 2014/10/08 01:12:14]

Please add a comment that the lock is already acquired.

[Raymond Toy, 2014/10/14 17:16:59]

Done.

+    // Resolve any pending promises created by resume(). Only do this we if haven't already started
+    // resolving these promises. This gets called very often and it takes some time use to resolve
+    // the promises in the main thread.
+    if (!m_isResolvingResumePromises && m_resumePromises.size() > 0) {
+        m_isResolvingResumePromises = true;
+        callOnMainThread(bind(&AudioContext::resolvePromisesForResumeOnMainThread, this));
+    }
+}
+
 const AtomicString& AudioContext::interfaceName() const
 {
     return EventTargetNames::AudioContext;
 }
 
 ExecutionContext* AudioContext::executionContext() const
 {
     return m_isStopScheduled ? 0 : ActiveDOMObject::executionContext();
 }
 
@@ skipping 52 matching lines @@
 
     for (HashSet<AudioNode*>::iterator k = m_deferredCountModeChange.begin(); k != m_deferredCountModeChange.end(); ++k)
         (*k)->updateChannelCountMode();
 
     m_deferredCountModeChange.clear();
 }
 
 } // namespace blink
 
 #endif // ENABLE(WEB_AUDIO)