Implementation of 'AudioContext.getOutputTimestamp' method

third_party/WebKit/Source/modules/webaudio/BaseAudioContext.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 84 matching lines @@
       m_isCleared(false),
       m_isResolvingResumePromises(false),
       m_userGestureRequired(false),
       m_connectionCount(0),
       m_deferredTaskHandler(DeferredTaskHandler::create()),
       m_contextState(Suspended),
       m_closedContextSampleRate(-1),
       m_periodicWaveSine(nullptr),
       m_periodicWaveSquare(nullptr),
       m_periodicWaveSawtooth(nullptr),
-      m_periodicWaveTriangle(nullptr) {
+      m_periodicWaveTriangle(nullptr),
+      m_outputPosition() {

[Raymond Toy, 2016/11/04 17:51:40]

Don't you want to initialize this to something?  It's possible for the context
to be suspended at startup so if it gets queried, the output position will be
random junk.

[Mikhail, 2016/11/07 18:28:03]

this invokes "default" constructor for the structure, so both position and
timestamp are set to zero.

   // If mediaPlaybackRequiresUserGesture is enabled, cross origin iframes will
   // require user gesture for the AudioContext to produce sound.
   if (document->settings() &&
       document->settings()->mediaPlaybackRequiresUserGesture() &&
       document->frame() && document->frame()->isCrossOriginSubframe()) {
     m_autoplayStatus = AutoplayStatus::AutoplayStatusFailed;
     m_userGestureRequired = true;
   }
 
   m_destinationNode = DefaultAudioDestinationNode::create(this);
@@ skipping 12 matching lines @@
       m_isCleared(false),
       m_isResolvingResumePromises(false),
       m_userGestureRequired(false),
       m_connectionCount(0),
       m_deferredTaskHandler(DeferredTaskHandler::create()),
       m_contextState(Suspended),
       m_closedContextSampleRate(-1),
       m_periodicWaveSine(nullptr),
       m_periodicWaveSquare(nullptr),
       m_periodicWaveSawtooth(nullptr),
-      m_periodicWaveTriangle(nullptr) {}
+      m_periodicWaveTriangle(nullptr),
+      m_outputPosition() {}
 
 BaseAudioContext::~BaseAudioContext() {
   deferredTaskHandler().contextWillBeDestroyed();
   // AudioNodes keep a reference to their context, so there should be no way to
   // be in the destructor if there are still AudioNodes around.
   DCHECK(!isDestinationInitialized());
   DCHECK(!m_activeSourceNodes.size());
   DCHECK(!m_finishedSourceHandlers.size());
   DCHECK(!m_isResolvingResumePromises);
   DCHECK(!m_resumeResolvers.size());
@@ skipping 550 matching lines @@
       continue;
     if (node->handler().getNodeType() ==
         AudioHandler::NodeTypeAudioBufferSource) {
       AudioBufferSourceNode* sourceNode =
           static_cast<AudioBufferSourceNode*>(node);
       sourceNode->audioBufferSourceHandler().handleStoppableSourceNode();
     }
   }
 }
 
-void BaseAudioContext::handlePreRenderTasks() {
+void BaseAudioContext::handlePreRenderTasks(
+    const AudioIOPosition& outputPosition) {
   DCHECK(isAudioThread());
 
   // At the beginning of every render quantum, try to update the internal
   // rendering graph state (from main thread changes).  It's OK if the tryLock()
   // fails, we'll just take slightly longer to pick up the changes.
   if (tryLock()) {
     deferredTaskHandler().handleDeferredTasks();
 
     resolvePromisesForResume();
 
     // Check to see if source nodes can be stopped because the end time has
     // passed.
     handleStoppableSourceNodes();
 
     // Update the dirty state of the listener.
     listener()->updateState();
 
+    // Update output timestamp.
+    m_outputPosition = outputPosition;
+
     unlock();
   }
 }
 
 void BaseAudioContext::handlePostRenderTasks() {
   DCHECK(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
@@ skipping 73 matching lines @@
     return true;
 
   toDocument(getExecutionContext())
       ->addConsoleMessage(ConsoleMessage::create(
           JSMessageSource, WarningMessageLevel,
           "An AudioContext in a cross origin iframe must be created or resumed "
           "from a user gesture to enable audio output."));
   return false;
 }
 
+AudioIOPosition BaseAudioContext::outputPosition() {
+  AutoLocker locker(this);
+  return m_outputPosition;
+}
+
 void BaseAudioContext::rejectPendingResolvers() {
   DCHECK(isMainThread());
 
   // Audio context is closing down so reject any resume promises that are still
   // pending.
 
   for (auto& resolver : m_resumeResolvers) {
     resolver->reject(
         DOMException::create(InvalidStateError, "Audio context is going away"));
   }
@@ skipping 51 matching lines @@
 }
 
 SecurityOrigin* BaseAudioContext::getSecurityOrigin() const {
   if (getExecutionContext())
     return getExecutionContext()->getSecurityOrigin();
 
   return nullptr;
 }
 
 }  // namespace blink