Update the current frame count in a safe place

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 92 matching lines @@
     , m_isCleared(false)
     , m_isInitialized(false)
     , m_destinationNode(nullptr)
     , m_isResolvingResumePromises(false)
     , m_automaticPullNodesNeedUpdating(false)
     , m_connectionCount(0)
     , m_didInitializeContextGraphMutex(false)
     , m_audioThread(0)
     , m_isOfflineContext(false)
     , m_contextState(Suspended)
+    , m_cachedSampleFrame(0)
 {
     m_didInitializeContextGraphMutex = true;
     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_didInitializeContextGraphMutex(false)
     , m_audioThread(0)
     , m_isOfflineContext(true)
     , m_contextState(Suspended)
+    , m_cachedSampleFrame(0)
 {
     m_didInitializeContextGraphMutex = 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());
 
     initialize();
 }
 
@@ skipping 402 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);
 }
 
+size_t AudioContext::cachedSampleFrame() const
+{
+    ASSERT(isMainThread());
+
+    return m_cachedSampleFrame;
+}
+
 String AudioContext::state() const
 {
     // These strings had better match the strings for AudioContextState in AudioContext.idl.
     switch (m_contextState) {
     case Suspended:
         return "suspended";
     case Running:
         return "running";
     case Closed:
         return "closed";
@@ skipping 192 matching lines @@
         // Update the channel count mode.
         updateChangedChannelCountMode();
 
         // Fixup the state of any dirty AudioSummingJunctions and AudioNodeOutputs.
         handleDirtyAudioSummingJunctions();
         handleDirtyAudioNodeOutputs();
 
         updateAutomaticPullNodes();
         resolvePromisesForResume();
 
+        // Update the cached sample frame value.
+        m_cachedSampleFrame = currentSampleFrame();
+
         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 332 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)