Implement suspend() and resume() for OfflineAudioContext

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

Index: third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
index b95e4da61988f5074ebc95145d4682c63b41c476..5fc0fb0d5b7695d85f1301d4b4125bf8575518b6 100644
--- a/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/third_party/WebKit/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -32,6 +32,8 @@
 #include "core/dom/Document.h"
 #include "core/dom/ExceptionCode.h"
 #include "core/dom/ExecutionContext.h"
+#include "modules/webaudio/OfflineAudioCompletionEvent.h"
+#include "modules/webaudio/OfflineAudioDestinationNode.h"
 #include "platform/audio/AudioUtilities.h"
 
 namespace blink {
@@ -93,26 +95,44 @@ OfflineAudioContext* OfflineAudioContext::create(ExecutionContext* context, unsi
 
 OfflineAudioContext::OfflineAudioContext(Document* document, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate)
     : AbstractAudioContext(document, numberOfChannels, numberOfFrames, sampleRate)
+    , m_isRenderingStarted(false)
+    , m_totalRenderFrames(numberOfFrames)
 {
+    // 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();
 }
 
 OfflineAudioContext::~OfflineAudioContext()
 {
 }
 
+DEFINE_TRACE(OfflineAudioContext)
+{
+    visitor->trace(m_renderTarget);
+    visitor->trace(m_completeResolver);
+    visitor->trace(m_scheduledSuspends);
+    AbstractAudioContext::trace(visitor);
+}
+
 ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptState)
 {
+    ASSERT(isMainThread());
+
     // Calling close() on an OfflineAudioContext is not supported/allowed,
-    // but it might well have been stopped by its execution context.
+    // but it might well have been closed by its execution context.
     if (isContextClosed()) {
         return ScriptPromise::rejectWithDOMException(
             scriptState,
             DOMException::create(
                 InvalidStateError,
-                "cannot call startRendering on an OfflineAudioContext in a stopped state."));
+                "cannot call startRendering on an OfflineAudioContext in a closed state."));
     }
 
-    if (m_offlineResolver) {
+    if (m_completeResolver) {
         // Can't call startRendering more than once.  Return a rejected promise now.
         return ScriptPromise::rejectWithDOMException(
             scriptState,
@@ -121,34 +141,229 @@ ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptStat
                 "cannot call startRendering more than once"));
     }
 
-    m_offlineResolver = ScriptPromiseResolver::create(scriptState);
-    startRendering();
-    return m_offlineResolver->promise();
+    // If the context is not in the suspended state, reject the promise.
+    if (contextState() != AudioContextState::Suspended) {
+        return ScriptPromise::rejectWithDOMException(
+            scriptState,
+            DOMException::create(
+                InvalidStateError,
+                "cannot startRendering when an OfflineAudioContext is not in a suspended state"));
+    }
+
+    m_completeResolver = ScriptPromiseResolver::create(scriptState);
+
+    ASSERT(!m_isRenderingStarted);
+
+    // Start rendering and return the promise.
+    m_isRenderingStarted = true;
+    setContextState(Running);
+    destinationHandler().startRendering();
+
+    return m_completeResolver->promise();
 }
 
 ScriptPromise OfflineAudioContext::closeContext(ScriptState* scriptState)
 {
-    return ScriptPromise::rejectWithDOMException(
-        scriptState,
+    return ScriptPromise::rejectWithDOMException(scriptState,
         DOMException::create(InvalidAccessError, "cannot close an OfflineAudioContext."));
 }
 
-ScriptPromise OfflineAudioContext::suspendContext(ScriptState* scriptState)
+ScriptPromise OfflineAudioContext::suspendContext(ScriptState* scriptState, double when)
 {
-    return ScriptPromise::rejectWithDOMException(
-        scriptState,
-        DOMException::create(
-            InvalidAccessError,
-            "cannot suspend an OfflineAudioContext"));
+    ASSERT(isMainThread());
+
+    ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->promise();
+
+    // Quantize (to the lower boundary) the suspend time by the render quantum.
+    size_t frame = when * sampleRate();

[Raymond Toy, 2015/10/16 23:32:36]

No check for negative value of when?  That should be illegal, right?

Oh, it's below.  Then I would move this code down past the check.

[hongchan, 2015/10/19 20:08:12]

Done.

+    frame = frame - (frame % destinationHandler().renderQuantumLength());

[Raymond Toy, 2015/10/16 23:32:36]

Maybe "frame -= ..." is clearer than "frame = frame - ..."

[hongchan, 2015/10/19 20:08:12]

Done.

+
+    // The render thread does not exist; reject the promise.
+    if (!destinationHandler().offlineRenderThread()) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "the rendering is already finished"));
+        return promise;
+    }
+
+    // The specified suspend time is negative; reject the promise.
+    if (when < 0) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "negative suspend time (" + String::number(when) + ") is not allowed"));
+        return promise;
+    }
+
+    // The suspend time should be earlier than the total render frame. If the
+    // requested suspension time is equal to the total render frame, the promise
+    // will be rejected.
+    if (m_totalRenderFrames <= frame) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot schedule a suspend at frame " + String::number(frame) +
+            " (" + String::number(when) + " seconds) " +
+            "because it is greater than or equal to the total render duration of " +
+            String::number(m_totalRenderFrames) + " frames"));
+        return promise;
+    }
+
+    // The specified suspend time is in the past; reject the promise.
+    if (frame < currentSampleFrame()) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot schedule a suspend at frame " +
+            String::number(frame) + " (" + String::number(when) +
+            " seconds) because it is earlier than the current frame of " +
+            String::number(currentSampleFrame()) + " (" +
+            String::number(currentTime()) + " seconds)"));
+        return promise;
+    }
+
+    // If there is a duplicate suspension at the same quantized frame,
+    // reject the promise.
+    if (m_scheduledSuspends.contains(frame)) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot schedule more than one suspend at frame " +
+            String::number(frame) + " (" +
+            String::number(when) + " seconds)"));
+        return promise;
+    }
+
+    // Wait until the suspend map is available for the insertion.
+    AutoLocker lock(this);
+
+    m_scheduledSuspends.add(frame, resolver);
+
+    return promise;
 }
 
 ScriptPromise OfflineAudioContext::resumeContext(ScriptState* scriptState)
 {
-    return ScriptPromise::rejectWithDOMException(
-        scriptState,
-        DOMException::create(
-            InvalidAccessError,
-            "cannot resume an OfflineAudioContext"));
+    ASSERT(isMainThread());
+
+    ScriptPromiseResolver* resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->promise();
+
+    // If the context is not in a suspended state, reject the promise.
+    if (contextState() != AudioContextState::Suspended) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot resume a context that is not suspended"));

[Raymond Toy, 2015/10/16 23:32:36]

Maybe say what state we're actually in.  Just for extra info since we know what
state we're in for free.

[hongchan, 2015/10/20 22:03:06]

Okay, I will reverse the order of the checks. So if your context has not been
started, resuming will be rejected with the proper error message. Otherwise it
means user is trying to resume without suspending it previously.

+        return promise;
+    }
+
+    // If the rendering has not started, reject the promise.
+    if (!m_isRenderingStarted) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot resume a context that has not started"));
+        return promise;
+    }
+
+    // If the context is suspended, resume rendering by setting the state to
+    // "Running." and calling startRendering(). Note that resuming is possible
+    // only after the rendering started.
+    setContextState(Running);
+    destinationHandler().startRendering();
+
+    // Resolve the promise immediately.
+    resolver->resolve();
+
+    return promise;
+}
+
+ScriptPromise OfflineAudioContext::suspendContext(ScriptState* scriptState)
+{
+    // This CANNOT be called on OfflineAudioContext; this is only to implement
+    // the pure virtual interface from AbstractAudioContext.
+    RELEASE_ASSERT_NOT_REACHED();
+
+    return ScriptPromise();

[Raymond Toy, 2015/10/16 23:32:36]

Although this isn't reachable, maybe we should return a rejected promise.

[hongchan, 2015/10/19 20:08:12]

Done.

+}
+
+void OfflineAudioContext::fireCompletionEvent()
+{
+    ASSERT(isMainThread());
+
+    // We set the state to closed here so that the oncomplete event handler sees
+    // that the context has been closed.
+    setContextState(Closed);
+
+    AudioBuffer* renderedBuffer = renderTarget();
+
+    ASSERT(renderedBuffer);
+    if (!renderedBuffer)
+        return;
+
+    // Avoid firing the event if the document has already gone away.
+    if (executionContext()) {
+        // Call the offline rendering completion event listener and resolve the
+        // promise too.
+        dispatchEvent(OfflineAudioCompletionEvent::create(renderedBuffer));
+        m_completeResolver->resolve(renderedBuffer);
+    } else {
+        // The resolver should be rejected when the execution context is gone.
+        m_completeResolver->reject(DOMException::create(InvalidStateError,
+            "the execution context does not exist"));
+    }
+}
+
+bool OfflineAudioContext::handlePreOfflineRenderTasks()
+{
+    ASSERT(isAudioThread());
+
+    // This is offline rendering, so it is safe to lock.

[Raymond Toy, 2015/10/16 23:32:36]

I would expand on this to say why it's safe to cause pauses. (Is that covered
somewhere else?)

[hongchan, 2015/10/19 20:08:12]

Done.

+    deferredTaskHandler().offlineLock();
+
+    deferredTaskHandler().handleDeferredTasks();
+    handleStoppableSourceNodes();
+    deferredTaskHandler().unlock();
+
+    return shouldSuspend();
+}
+
+void OfflineAudioContext::handlePostOfflineRenderTasks()
+{
+    ASSERT(isAudioThread());
+
+    // This is offline rendering, so it is safe to lock.

[Raymond Toy, 2015/10/16 23:32:36]

Expand on this comment, like above.

[hongchan, 2015/10/19 20:08:12]

Done.

+    deferredTaskHandler().offlineLock();
+
+    deferredTaskHandler().breakConnections();
+    releaseFinishedSourceNodes();
+    deferredTaskHandler().handleDeferredTasks();
+    deferredTaskHandler().requestToDeleteHandlersOnMainThread();
+
+    deferredTaskHandler().unlock();
+}
+
+
+OfflineAudioDestinationHandler& OfflineAudioContext::destinationHandler()
+{
+    return static_cast<OfflineAudioDestinationHandler&>(destination()->audioDestinationHandler());
+}
+
+void OfflineAudioContext::resolveSuspendOnMainThread(size_t frame)
+{
+    ASSERT(isMainThread());
+
+    // Suspend the context first. This will fire onstatechange event.
+    setContextState(Suspended);
+
+    ASSERT(m_scheduledSuspends.contains(frame));
+
+    // Wait until the suspend map is available for the removal.
+    AutoLocker locker(this);
+
+    SuspendMap::iterator it = m_scheduledSuspends.find(frame);
+    it->value->resolve();
+
+    m_scheduledSuspends.remove(it);
+}
+
+bool OfflineAudioContext::shouldSuspend()
+{
+    ASSERT(isAudioThread());
+
+    if (m_scheduledSuspends.contains(currentSampleFrame()))
+        return true;
+
+    return false;
 }
 
 } // namespace blink