Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/OfflineAudioDestinationNode.h

 /*
  * Copyright (C) 2011, 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
  *    documentation and/or other materials provided with the distribution.
  *
  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
 #ifndef OfflineAudioDestinationNode_h
 #define OfflineAudioDestinationNode_h
 
 #include "modules/webaudio/AudioBuffer.h"
 #include "modules/webaudio/AudioDestinationNode.h"
+#include "modules/webaudio/OfflineAudioContext.h"
 #include "public/platform/WebThread.h"
 #include "wtf/PassRefPtr.h"
 #include "wtf/RefPtr.h"
 
 namespace blink {
 
 class AbstractAudioContext;
 class AudioBus;
+class OfflineAudioContext;
 
 class OfflineAudioDestinationHandler final : public AudioDestinationHandler {
 public:
     static PassRefPtr<OfflineAudioDestinationHandler> create(AudioNode&, AudioBuffer* renderTarget);
     ~OfflineAudioDestinationHandler() override;
 
     // AudioHandler
     void dispose() override;
     void initialize() override;
     void uninitialize() override;
 
-    // AudioDestinationHandler
+    OfflineAudioContext* context() const final;
+
+    // Override the one from AudioContext. Create a rendering thread and
+    // initiate rendering loop or resume rendering if already started and
+    // suspended.
     void startRendering() override;
+
+    // There is no support of the explicit stopping in OfflineAudioContext. This
+    // is just to match the class method signature.
     void stopRendering() override;
 
-    float sampleRate()  const override { return m_renderTarget->sampleRate(); }
+    float sampleRate() const override { return m_renderTarget->sampleRate(); }
+
+    // Return the frame position by quantizing the time (in seconds) and
+    // rounding it down to the nearest render quantum boundary.
+    size_t quantizeTimeToRenderQuantum(double when) const;
+
+    WebThread* offlineRenderThread();
 
 private:
     OfflineAudioDestinationHandler(AudioNode&, AudioBuffer* renderTarget);
-    void offlineRender();
-    void offlineRenderInternal();
+
+    // For start/suspend/resume rendering in the destination node.
+    void startOfflineRendering();
+    void runOfflineRendering();
+    void finishOfflineRendering();
 
     // For completion callback on main thread.
     void notifyComplete();
 
     // This AudioHandler renders into this AudioBuffer.
     // This Persistent doesn't make a reference cycle including the owner
     // OfflineAudioDestinationNode.
     Persistent<AudioBuffer> m_renderTarget;
     // Temporary AudioBus for each render quantum.
     RefPtr<AudioBus> m_renderBus;
 
     // Rendering thread.
     OwnPtr<WebThread> m_renderThread;
-    bool m_startedRendering;
+
+    size_t m_framesProcessed;
+    size_t m_framesToProcess;
+
+    bool m_isRenderingStarted;
 };
 
 class OfflineAudioDestinationNode final : public AudioDestinationNode {
 public:
     static OfflineAudioDestinationNode* create(AbstractAudioContext*, AudioBuffer* renderTarget);
 
 private:
     OfflineAudioDestinationNode(AbstractAudioContext&, AudioBuffer* renderTarget);
 };
 
 } // namespace blink
 
 #endif // OfflineAudioDestinationNode_h