Bug 1126465 - Introduce machinery to hold onto MediaPromise::Consumer references, and use it for MediaSourceReader subdecoders. r=mattwoodrow

dom/media/MediaPromise.h

@@ -252,8 +252,8 @@ public:
 
   template<typename TargetType, typename ThisType,
            typename ResolveMethodType, typename RejectMethodType>
-  void Then(TargetType* aResponseTarget, const char* aCallSite, ThisType* aThisVal,
-            ResolveMethodType aResolveMethod, RejectMethodType aRejectMethod)
+  already_AddRefed<Consumer> RefableThen(TargetType* aResponseTarget, const char* aCallSite, ThisType* aThisVal,
+                                         ResolveMethodType aResolveMethod, RejectMethodType aRejectMethod)
   {
     MutexAutoLock lock(mMutex);
     MOZ_RELEASE_ASSERT(!IsExclusive || !mHaveConsumer);
@@ -269,6 +269,18 @@ public:
     } else {
       mThenValues.AppendElement(thenValue);
     }
+
+    return thenValue.forget();
+  }
+
+  template<typename TargetType, typename ThisType,
+           typename ResolveMethodType, typename RejectMethodType>
+  void Then(TargetType* aResponseTarget, const char* aCallSite, ThisType* aThisVal,
+            ResolveMethodType aResolveMethod, RejectMethodType aRejectMethod)
+  {
+    nsRefPtr<Consumer> c =
+      RefableThen(aResponseTarget, aCallSite, aThisVal, aResolveMethod, aRejectMethod);
+    return;
   }
 
   void ChainTo(already_AddRefed<MediaPromise> aChainedPromise, const char* aCallSite)
@@ -436,6 +448,35 @@ private:
   nsRefPtr<PromiseType> mPromise;
 };
 
+/*
+ * Class to encapsulate a MediaPromise::Consumer reference. Use this as the member
+ * variable for a class waiting on a media promise.
+ */
+template<typename PromiseType>
+class MediaPromiseConsumerHolder
+{
+public:
+  MediaPromiseConsumerHolder() {}
+  ~MediaPromiseConsumerHolder() { MOZ_ASSERT(!mConsumer); }
+
+  void Begin(already_AddRefed<typename PromiseType::Consumer> aConsumer)
+  {
+    MOZ_RELEASE_ASSERT(!Exists());
+    mConsumer = aConsumer;
+  }
+
+  void Complete()
+  {
+    MOZ_RELEASE_ASSERT(Exists());
+    mConsumer = nullptr;
+  }
+
+  bool Exists() { return !!mConsumer; }
+
+private:
+  nsRefPtr<typename PromiseType::Consumer> mConsumer;
+};
+
 #undef PROMISE_LOG
 
 } // namespace mozilla

dom/media/mediasource/MediaSourceReader.cpp

@@ -148,9 +148,10 @@ MediaSourceReader::RequestAudioData()
 void
 MediaSourceReader::RequestAudioDataComplete(int64_t aTime)
 {
-  mAudioReader->RequestAudioData()->Then(GetTaskQueue(), __func__, this,
-                                         &MediaSourceReader::OnAudioDecoded,
-                                         &MediaSourceReader::OnAudioNotDecoded);
+  mAudioRequest.Begin(mAudioReader->RequestAudioData()
+                      ->RefableThen(GetTaskQueue(), __func__, this,
+                                    &MediaSourceReader::OnAudioDecoded,
+                                    &MediaSourceReader::OnAudioNotDecoded));
 }
 
 void
@@ -162,15 +163,18 @@ MediaSourceReader::RequestAudioDataFailed(nsresult aResult)
 void
 MediaSourceReader::OnAudioDecoded(AudioData* aSample)
 {
+  mAudioRequest.Complete();
+
   MSE_DEBUGV("MediaSourceReader(%p)::OnAudioDecoded [mTime=%lld mDuration=%lld mDiscontinuity=%d]",
              this, aSample->mTime, aSample->mDuration, aSample->mDiscontinuity);
   if (mDropAudioBeforeThreshold) {
     if (aSample->mTime < mTimeThreshold) {
       MSE_DEBUG("MediaSourceReader(%p)::OnAudioDecoded mTime=%lld < mTimeThreshold=%lld",
                 this, aSample->mTime, mTimeThreshold);
-      mAudioReader->RequestAudioData()->Then(GetTaskQueue(), __func__, this,
-                                             &MediaSourceReader::OnAudioDecoded,
-                                             &MediaSourceReader::OnAudioNotDecoded);
+      mAudioRequest.Begin(mAudioReader->RequestAudioData()
+                          ->RefableThen(GetTaskQueue(), __func__, this,
+                                        &MediaSourceReader::OnAudioDecoded,
+                                        &MediaSourceReader::OnAudioNotDecoded));
       return;
     }
     mDropAudioBeforeThreshold = false;
@@ -215,6 +219,8 @@ AdjustEndTime(int64_t* aEndTime, MediaDecoderReader* aReader)
 void
 MediaSourceReader::OnAudioNotDecoded(NotDecodedReason aReason)
 {
+  mAudioRequest.Complete();
+
   MSE_DEBUG("MediaSourceReader(%p)::OnAudioNotDecoded aReason=%u IsEnded: %d", this, aReason, IsEnded());
   if (aReason == DECODE_ERROR || aReason == CANCELED) {
     mAudioPromise.Reject(aReason, __func__);
@@ -279,9 +285,10 @@ MediaSourceReader::RequestVideoData(bool aSkipToNextKeyframe, int64_t aTimeThres
       }
       // Fallback to using current reader.
     default:
-      mVideoReader->RequestVideoData(aSkipToNextKeyframe, aTimeThreshold)
-                  ->Then(GetTaskQueue(), __func__, this,
-                         &MediaSourceReader::OnVideoDecoded, &MediaSourceReader::OnVideoNotDecoded);
+      mVideoRequest.Begin(mVideoReader->RequestVideoData(aSkipToNextKeyframe, aTimeThreshold)
+                          ->RefableThen(GetTaskQueue(), __func__, this,
+                                        &MediaSourceReader::OnVideoDecoded,
+                                        &MediaSourceReader::OnVideoNotDecoded));
       break;
   }
 
@@ -291,9 +298,10 @@ MediaSourceReader::RequestVideoData(bool aSkipToNextKeyframe, int64_t aTimeThres
 void
 MediaSourceReader::RequestVideoDataComplete(int64_t aTime)
 {
-  mVideoReader->RequestVideoData(false, 0)
-              ->Then(GetTaskQueue(), __func__, this,
-                     &MediaSourceReader::OnVideoDecoded, &MediaSourceReader::OnVideoNotDecoded);
+  mVideoRequest.Begin(mVideoReader->RequestVideoData(false, 0)
+                      ->RefableThen(GetTaskQueue(), __func__, this,
+                                    &MediaSourceReader::OnVideoDecoded,
+                                    &MediaSourceReader::OnVideoNotDecoded));
 }
 
 void
@@ -305,15 +313,18 @@ MediaSourceReader::RequestVideoDataFailed(nsresult aResult)
 void
 MediaSourceReader::OnVideoDecoded(VideoData* aSample)
 {
+  mVideoRequest.Complete();
+
   MSE_DEBUGV("MediaSourceReader(%p)::OnVideoDecoded [mTime=%lld mDuration=%lld mDiscontinuity=%d]",
              this, aSample->mTime, aSample->mDuration, aSample->mDiscontinuity);
   if (mDropVideoBeforeThreshold) {
     if (aSample->mTime < mTimeThreshold) {
       MSE_DEBUG("MediaSourceReader(%p)::OnVideoDecoded mTime=%lld < mTimeThreshold=%lld",
                 this, aSample->mTime, mTimeThreshold);
-      mVideoReader->RequestVideoData(false, 0)->Then(GetTaskQueue(), __func__, this,
-                                                     &MediaSourceReader::OnVideoDecoded,
-                                                     &MediaSourceReader::OnVideoNotDecoded);
+      mVideoRequest.Begin(mVideoReader->RequestVideoData(false, 0)
+                          ->RefableThen(GetTaskQueue(), __func__, this,
+                                        &MediaSourceReader::OnVideoDecoded,
+                                        &MediaSourceReader::OnVideoNotDecoded));
       return;
     }
     mDropVideoBeforeThreshold = false;
@@ -332,6 +343,8 @@ MediaSourceReader::OnVideoDecoded(VideoData* aSample)
 void
 MediaSourceReader::OnVideoNotDecoded(NotDecodedReason aReason)
 {
+  mVideoRequest.Complete();
+
   MSE_DEBUG("MediaSourceReader(%p)::OnVideoNotDecoded aReason=%u IsEnded: %d", this, aReason, IsEnded());
   if (aReason == DECODE_ERROR || aReason == CANCELED) {
     mVideoPromise.Reject(aReason, __func__);

dom/media/mediasource/MediaSourceReader.h

@@ -183,6 +183,9 @@ private:
   nsRefPtr<TrackBuffer> mAudioTrack;
   nsRefPtr<TrackBuffer> mVideoTrack;
 
+  MediaPromiseConsumerHolder<AudioDataPromise> mAudioRequest;
+  MediaPromiseConsumerHolder<VideoDataPromise> mVideoRequest;
+
   MediaPromiseHolder<AudioDataPromise> mAudioPromise;
   MediaPromiseHolder<VideoDataPromise> mVideoPromise;