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 b95e4da61988f5074ebc95145d4682c63b41c476..c76cb5eaa3dced181f3909af176aae11affc5f50 100644
--- a/Source/modules/webaudio/OfflineAudioContext.cpp
+++ b/Source/modules/webaudio/OfflineAudioContext.cpp
@@ -32,7 +32,13 @@
 #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 {
 
@@ -93,26 +99,106 @@ 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)
 {
 }
 
 OfflineAudioContext::~OfflineAudioContext()
 {
+    // Reject all the remaining suspends and delete the raw pointer.
+    for (ScheduledSuspendContainer* suspendContainer : m_suspendContainers) {
+        suspendContainer->rejectPromise(InvalidStateError,
+            "Offline audio context is going away");
+
+        delete suspendContainer;
+    }
+
+    // TODO(hongchan): is this necessary?
+    m_suspendContainers.clear();
+}
+
+DEFINE_TRACE(OfflineAudioContext)
+{
+    visitor->trace(m_completeResolver);
+    AbstractAudioContext::trace(visitor);
+}
+
+bool OfflineAudioContext::shouldSuspendNow()
+{
+    ASSERT(!isMainThread());
+
+    // If there is any scheduled suspend at |currentSampleFrame|, the context
+    // should be suspended.
+    if (!m_scheduledSuspends.contains(currentSampleFrame()))
+        return false;
+
+    return true;
+}
+
+void OfflineAudioContext::resolvePendingSuspendPromises()
+{
+    ASSERT(!isMainThread());
+
+    // Find a suspend scheduled at |currentSampleFrame| and resolve the
+    // associated promise on the main thread.
+    SuspendContainerMap::iterator it = m_scheduledSuspends.find(currentSampleFrame());
+    if (it == m_scheduledSuspends.end())
+        return;
+
+    ScheduledSuspendContainer* suspendContainer = it->value;
+    m_scheduledSuspends.remove(it);
+
+    // Passing a raw pointer |suspendContainer| is safe here because it is
+    // created and destructed on the main thread. Also it is guaranteed to
+    // be alive until the task is finished somewhere else.

[hiroshige, 2015/07/22 17:32:12]

How about:
Passing a raw pointer |suspendContainer| is safe here because it is
created, destructed and owned (by |m_suspendContainers|) on the main thread.
Also it is guaranteed to be alive until:
- the raw pointer is passed back to the main thread and
resolveSuspendContainerOnMainThread()/rejectSuspendContainerOnMainThread() is
called on the main thread, or
- OfflineAudioContext is destructed.

[hongchan, 2015/07/22 20:36:35]

Done.

+    Platform::current()->mainThread()->postTask(FROM_HERE,
+        threadSafeBind(&OfflineAudioContext::resolveSuspendContainerOnMainThread, this,
+            AllowCrossThreadAccess(suspendContainer)));
+}
+
+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"));
+    }
 }
 
 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,
@@ -121,9 +207,24 @@ 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.
+    ASSERT(!m_isRenderingStarted);
+    m_isRenderingStarted = true;
+    setContextState(Running);
+    destinationHandler().startRendering();
+
+    return m_completeResolver->promise();
 }
 
 ScriptPromise OfflineAudioContext::closeContext(ScriptState* scriptState)
@@ -135,20 +236,201 @@ ScriptPromise OfflineAudioContext::closeContext(ScriptState* scriptState)
 
 ScriptPromise OfflineAudioContext::suspendContext(ScriptState* scriptState)
 {
-    return ScriptPromise::rejectWithDOMException(
-        scriptState,
-        DOMException::create(
-            InvalidAccessError,
-            "cannot suspend an OfflineAudioContext"));
+    // This CANNOT be called on OfflineAudioContext; it is to implement the pure
+    // virtual interface from AbstractAudioContext.
+    RELEASE_ASSERT_NOT_REACHED();
+
+    return ScriptPromise();
+}
+
+ScriptPromise OfflineAudioContext::suspendContext(ScriptState* scriptState, double when)
+{
+    ASSERT(isMainThread());
+
+    RefPtrWillBeRawPtr<ScriptPromiseResolver> resolver = ScriptPromiseResolver::create(scriptState);
+    ScriptPromise promise = resolver->promise();
+
+    // 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;
+    }
+
+    // Quantize the suspend time to the render quantum boundary.
+    size_t quantizedFrame = destinationHandler().quantizeTimeToRenderQuantum(when);
+
+    // 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(resolver);
+
+    // Basic checks are passed; store the object to maintain the ownership.
+    m_suspendContainers.add(suspendContainer);
+
+    // Validate the suspend and add it if necessary on the render thread.
+    // Note that passing a raw pointer |suspendContainer| is safe here as well
+    // with the same reason in |resolvePendingSuspendPromises|.
+    destinationHandler().offlineRenderThread()->postTask(FROM_HERE,
+        threadSafeBind(&OfflineAudioContext::validateSuspendContainerOnRenderThread, this,

[hiroshige, 2015/07/22 17:51:17]

IIUC,
1. OfflineAudioContext is GarbageCollected.
2. offlineRenderThread() is not a Oilpan-attached thread.

From 1., threadSafeBind() passes a reference of OfflineAudioContext as
CrossThreadPersistent<OfflineAudioContext> to offlineRenderThread() (See 
PointerParamStorageTraits<T*, true> in
https://code.google.com/p/chromium/codesearch#chromium/src/third_party/WebKit...).
But holding/manipulating CrossThreadPersistent on a non-Oilpan thread (i.e. the
offline render thread) might not be safe?
haraken@, any comments?

+            AllowCrossThreadAccess(suspendContainer),
+            when,
+            quantizedFrame));
+
+    return promise;
 }
 
 ScriptPromise OfflineAudioContext::resumeContext(ScriptState* scriptState)
 {
-    return ScriptPromise::rejectWithDOMException(
-        scriptState,
-        DOMException::create(
-            InvalidAccessError,
-            "cannot resume an OfflineAudioContext"));
+    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);
+    destinationHandler().startRendering();
+
+    // Resolve the promise immediately.
+    resolver->resolve();
+
+    return promise;
+}
+
+OfflineAudioDestinationHandler& OfflineAudioContext::destinationHandler()
+{
+    return static_cast<OfflineAudioDestinationHandler&>(destination()->audioDestinationHandler());
+}
+
+void OfflineAudioContext::validateSuspendContainerOnRenderThread(ScheduledSuspendContainer* suspendContainer, double suspendTime, size_t suspendFrame)
+{
+    ASSERT(!isMainThread());
+
+    bool shouldBeRejected = false;
+    String errorMessage;
+
+    // The specified suspend time is in the past; reject the promise. We cannot
+    // reject the promise in here, so set the error message before posting the
+    // rejection task to the main thread.
+    if (suspendFrame < currentSampleFrame()) {
+        shouldBeRejected = true;
+        errorMessage = "cannot schedule a suspend at frame " +
+            String::number(suspendFrame) + " (" + String::number(suspendTime) +
+            " seconds) because it is earlier than the current frame of " +
+            String::number(currentSampleFrame()) + " (" +
+            String::number(currentTime()) + " seconds)";
+    } else if (m_scheduledSuspends.contains(suspendFrame)) {
+        // If there is a duplicate suspension at the same quantized frame,
+        // reject the promise. The rejection of promise should happen in the
+        // main thread, so we post a task to it. Here we simply set the error
+        // message and post a task to the main thread.
+        shouldBeRejected = true;
+        errorMessage = "cannot schedule more than one suspend at frame " +
+            String::number(suspendFrame) + " (" +
+            String::number(suspendTime) + " seconds)";
+    }
+
+    // Reject the promise if necessary on the main thread.
+    // Note that passing a raw pointer |suspendContainer| is safe here as well
+    // with the same reason in |resolvePendingSuspendPromises|.
+    if (shouldBeRejected) {
+        Platform::current()->mainThread()->postTask(FROM_HERE,
+            threadSafeBind(&OfflineAudioContext::rejectSuspendContainerOnMainThread, this,
+                AllowCrossThreadAccess(suspendContainer),
+                errorMessage.isolatedCopy()));

[hiroshige, 2015/07/22 17:32:12]

.isolatedCopy() is not needed because it is called automatically inside
threadSafeBind().

[hongchan, 2015/07/22 20:36:35]

Done.

+        return;
+    }
+
+    // If the validation check passes, we can add the container safely here in
+    // the render thread.
+    m_scheduledSuspends.add(suspendFrame, suspendContainer);
+}
+
+void OfflineAudioContext::rejectSuspendContainerOnMainThread(ScheduledSuspendContainer* suspendContainer, const String& errorMessage)
+{
+    ASSERT(isMainThread());
+

[hiroshige, 2015/07/22 17:32:12]

Please add RELEASE_ASSERT before dereferencing |suspendContainer| that
|suspendContainer| is in |m_suspendContainers| before remove().
(If |suspendContainer| is not in the set, then |*suspendContainer| is probably
already deleted and calling relectPromise() will be use-after-free, so
RELEASE_ASSERT).

[hongchan, 2015/07/22 20:36:35]

Done.

+    suspendContainer->rejectPromise(InvalidStateError, errorMessage);
+
+    // Remove the container out of the set and delete the raw pointer.
+    m_suspendContainers.remove(suspendContainer);
+    delete suspendContainer;
+}
+
+void OfflineAudioContext::resolveSuspendContainerOnMainThread(ScheduledSuspendContainer* suspendContainer)
+{
+    ASSERT(isMainThread());
+
+    // Suspend the context first. This will fire onstatechange event.
+    setContextState(Suspended);
+

[hiroshige, 2015/07/22 17:32:12]

ditto.

[hongchan, 2015/07/22 20:36:35]

Done.

+    suspendContainer->resolvePromise();
+
+    // Remove the container out of the set and delete the raw pointer.
+    m_suspendContainers.remove(suspendContainer);
+    delete suspendContainer;
+}
+
+ScheduledSuspendContainer::ScheduledSuspendContainer(PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver)
+    : m_resolver(resolver)
+{
+    ASSERT(isMainThread());
+}
+
+ScheduledSuspendContainer::~ScheduledSuspendContainer()
+{
+    ASSERT(isMainThread());
+}
+
+ScheduledSuspendContainer* ScheduledSuspendContainer::create(PassRefPtrWillBeRawPtr<ScriptPromiseResolver> resolver)
+{
+    return new ScheduledSuspendContainer(resolver);
+}
+
+void ScheduledSuspendContainer::resolvePromise()
+{
+    ASSERT(isMainThread());
+
+    m_resolver->resolve();
+}
+
+void ScheduledSuspendContainer::rejectPromise(ExceptionCode errorCode, const String& errorMessage)
+{
+    ASSERT(isMainThread());
+
+    m_resolver->reject(DOMException::create(errorCode, errorMessage));
 }
 
 } // namespace blink