Implement suspend() and resume() for OfflineAudioContext

Source/modules/webaudio/OfflineAudioContext.cpp

Index: Source/modules/webaudio/OfflineAudioContext.cpp
diff --git a/Source/modules/webaudio/OfflineAudioContext.cpp b/Source/modules/webaudio/OfflineAudioContext.cpp
index d3488419e947e373d50f13cb105be0fb0604d178..3529be094ee44f9e4f837a6d06d5d2c7c7cdd735 100644
--- a/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -31,7 +31,13 @@
 #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/Task.h"
+#include "platform/ThreadSafeFunctional.h"
 #include "platform/audio/AudioUtilities.h"
+#include "public/platform/Platform.h"
+
 
 namespace blink {
 
@@ -92,6 +98,8 @@ OfflineAudioContext* OfflineAudioContext::create(ExecutionContext* context, unsi
 
 OfflineAudioContext::OfflineAudioContext(Document* document, unsigned numberOfChannels, size_t numberOfFrames, float sampleRate)
     : AudioContext(document, numberOfChannels, numberOfFrames, sampleRate)
+    , m_isRenderingStarted(false)
+    , m_totalRenderFrames(numberOfFrames)
 {
 }
 
@@ -99,8 +107,71 @@ OfflineAudioContext::~OfflineAudioContext()
 {
 }
 
+DEFINE_TRACE(OfflineAudioContext)
+{
+    visitor->trace(m_scheduledSuspends);
+    visitor->trace(m_completeResolver);
+    AudioContext::trace(visitor);
+}
+
+bool OfflineAudioContext::shouldSuspendNow()
+{
+    ASSERT(!isMainThread());
+
+    // Suspend if necessary and mark the associated promise as pending. Marked
+    // promises will be resolved later. Note that duplicate entries in the
+    // suspend list are prohibited so it returns immediately when a valid
+    // suspend is found. This duplicate check is done by
+    // |suspendOfflineRendering|.
+    size_t nowFrame = currentSampleFrame();
+    for (unsigned index = 0; index < m_scheduledSuspends.size(); ++index) {
+        if (m_scheduledSuspends.at(index)->shouldSuspendAtFrame(nowFrame)) {
+            m_scheduledSuspends.at(index)->markAsPending();
+            return true;
+        }
+    }
+
+    return false;
+}
+
+void OfflineAudioContext::resolvePendingSuspendPromises()
+{
+    ASSERT(!isMainThread());
+
+    // Resolve promises marked as 'pending'.
+    if (m_scheduledSuspends.size() > 0) {
+        Platform::current()->mainThread()->postTask(FROM_HERE,
+            threadSafeBind(&OfflineAudioContext::resolvePendingSuspendPromisesOnMainThread, this));
+    }
+}
+
+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);
+    }
+}
+
 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.
     if (isContextClosed()) {
@@ -111,7 +182,7 @@ ScriptPromise OfflineAudioContext::startOfflineRendering(ScriptState* scriptStat
                 "cannot call startRendering on an OfflineAudioContext in a stopped state."));
     }
 
-    if (m_offlineResolver) {
+    if (m_completeResolver) {
         // Can't call startRendering more than once.  Return a rejected promise now.
         return ScriptPromise::rejectWithDOMException(
             scriptState,
@@ -120,9 +191,207 @@ 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);
+
+    // Start rendering and return the promise.
+    m_isRenderingStarted = true;
+    setContextState(Running);
+    destination()->audioDestinationHandler().startRendering();
+
+    return m_completeResolver->promise();
+}
+
+ScriptPromise OfflineAudioContext::suspendOfflineRendering(ScriptState* scriptState, double when)
+{
+    ASSERT(isMainThread());
+    ASSERT(destination()->audioDestinationHandler().offlineRenderThread());
+
+    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->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;
+    }
+
+    // Quantize the suspend time to the rendering block boundary.
+    size_t quantizedFrame = destination()->audioDestinationHandler().quantizeTimeToRenderQuantum(when);
+
+    // The specified suspend time is in the past, reject the promise.
+    if (quantizedFrame < currentSampleFrame()) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot schedule a suspend at frame " + String::number(quantizedFrame) +
+            " (" + String::number(when) + " seconds) because it is earlier than the current frame of " +
+            String::number(currentSampleFrame())));
+        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 <= quantizedFrame) {
+        resolver->reject(DOMException::create(InvalidStateError,
+            "cannot schedule a suspend at frame " + String::number(quantizedFrame) +
+            " (" + String::number(when) + " seconds) because it is greater than or equal to the total render duration of " +
+            String::number(m_totalRenderFrames) + " frames"));
+        return promise;
+    }
+
+    ScheduledSuspendContainer* suspendContainer = ScheduledSuspendContainer::create(when, quantizedFrame, resolver);
+
+    // Validate the suspend and append if necessary on the render thread.
+    destination()->audioDestinationHandler().offlineRenderThread()->postTask(FROM_HERE,
+        threadSafeBind(&OfflineAudioContext::checkDuplicateSuspend, this, suspendContainer));
+
+    return promise;
+}
+
+ScriptPromise OfflineAudioContext::resumeOfflineRendering(ScriptState* scriptState)
+{
+    ASSERT(isMainThread());
+
+    RefPtrWillBeRawPtr<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"));
+        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);
+    destination()->audioDestinationHandler().startRendering();
+
+    // Resolve the promise immediately.
+    resolver->resolve();
+
+    return promise;
+}
+
+void OfflineAudioContext::checkDuplicateSuspend(ScheduledSuspendContainer* suspendContainer)
+{
+    ASSERT(!isMainThread());
+
+    // If there is a duplicate suspension at the same quantize frame, reject the
+    // promise. The rejection of promise should happen in the main thread, so we
+    // post a task to it.
+    for (unsigned index = 0; index < m_scheduledSuspends.size(); ++index) {
+        if (m_scheduledSuspends.at(index)->suspendFrame() == suspendContainer->suspendFrame()) {
+            Platform::current()->mainThread()->postTask(FROM_HERE,
+                threadSafeBind(&OfflineAudioContext::rejectSuspendOnMainThread, this, suspendContainer));
+            return;
+        }
+    }
+
+    // If duplicate check passes, we can add the container safely here in the
+    // render thread.
+    MutexLocker locker(m_suspendMutex);
+    fprintf(stderr, "adding suspend...\n");
+    // TODO: this does not work. The tab crashes here.
+    m_scheduledSuspends.append(suspendContainer);

[hongchan, 2015/06/22 18:23:59]

This actually crashes the tab (no error message in the console with the debug
build). I only can see up to "adding suspend..." and it does not proceed after
that. Not sure how to prevent the crash.

Any thought?

[yhirano, 2015/06/23 02:33:42]

I didn't notice that the render thread doesn't support Oilpan. As a result, we
cannot use oilpan-related objects (GarbageCollected, HeapVector, etc.) in the
render thread.

That means:
 - ScheduledSuspendContainer should be ThreadSafeRefCounted,
 - m_scheduledSuspends should be Vector<RefPtr<ScheduledSuspendContainer>>,
if you want to access them in the render thread.

haraken@, please correct me if I'm wrong.


I'm sorry for the inconvenience.

[hongchan, 2015/06/23 17:57:38]

yhirano@ haraken@

I guess we can decide what we want here, but probably the best thing for the
future is to make the render thread oilpan-compatible.

Or as you suggested, we can just leave the render thread alone and revert the
shared components back to the old reference counting mechanism.

WDYT?

+    fprintf(stderr, "suspend added.\n");
+}
+
+void OfflineAudioContext::rejectSuspendOnMainThread(ScheduledSuspendContainer* suspendContainer)
+{
+    ASSERT(isMainThread());
+
+    suspendContainer->resolver()->reject(DOMException::create(InvalidStateError,
+        "cannot schedule more than one suspend at frame " +
+        String::number(suspendContainer->suspendFrame()) + " (" +
+        String::number(suspendContainer->suspendTime()) + " seconds)"));
+}
+
+void OfflineAudioContext::resolvePendingSuspendPromisesOnMainThread()
+{
+    ASSERT(isMainThread());
+    AutoLocker locker(this);
+
+    // Suspend the context first. This will fire onstatechange event.
+    setContextState(Suspended);
+
+    // TODO: is removing elements efficient? What if there are 10K suspends?
+    // TODO: move this to the render thread.
+    // Resolve any pending suspend and remove it from the list.
+    bool pendingPromiseResolved = false;
+    for (unsigned index = 0; index < m_scheduledSuspends.size();) {
+        if (m_scheduledSuspends.at(index)->isPending()) {
+
+            // We should never have more than one pending suspend at any time.
+            ASSERT(!pendingPromiseResolved);
+
+            m_scheduledSuspends.at(index)->resolver()->resolve();
+            m_scheduledSuspends.remove(index);
+
+            pendingPromiseResolved = true;
+        } else {
+            ++index;
+        }
+    }
+}
+
+ScheduledSuspendContainer::ScheduledSuspendContainer(
+    double suspendTime, size_t suspendFrame, PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver)
+    : m_suspendTime(suspendTime)
+    , m_suspendFrame(suspendFrame)
+    , m_resolver(resolver)
+    , m_isPending(false)
+{
+}
+
+ScheduledSuspendContainer::~ScheduledSuspendContainer()
+{
+}
+
+DEFINE_TRACE(ScheduledSuspendContainer)
+{
+    visitor->trace(m_resolver);
+}
+
+ScheduledSuspendContainer* ScheduledSuspendContainer::create(
+    double suspendTime, size_t suspendFrame, PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver)
+{
+    return new ScheduledSuspendContainer(suspendTime, suspendFrame, resolver);
+}
+
+bool ScheduledSuspendContainer::shouldSuspendAtFrame(size_t whenFrame) const
+{
+    if (m_suspendFrame != whenFrame)
+        return false;
+
+    return true;
+}
+
+bool ScheduledSuspendContainer::isPending() const
+{
+    return m_isPending;
+}
+
+void ScheduledSuspendContainer::markAsPending()
+{
+    m_isPending = true;
 }
 
 } // namespace blink