Bug 1558364 - Convert TrackBuffersManager::mPendingInput into a MediaSpan. r=jya

This allows us to avoid a (probably small) copy when we stash the pending input.

Differential Revision: https://phabricator.services.mozilla.com/D34662

--HG--
extra : moz-landing-system : lando

dom/media/MediaSpan.h

@@ -64,6 +64,8 @@ class MediaSpan {
     return (*mBuffer)[mStart + aIndex];
   }
 
+  bool Append(const MediaSpan& aBuffer) { return Append(aBuffer.Buffer()); }
+
   bool Append(MediaByteBuffer* aBuffer) {
     if (!aBuffer) {
       return true;

dom/media/mediasource/TrackBuffersManager.cpp

@@ -447,7 +447,7 @@ void TrackBuffersManager::CompleteResetParserState() {
   }
 
   // 7. Remove all bytes from the input buffer.
-  mPendingInputBuffer = nullptr;
+  mPendingInputBuffer.reset();
   mInputBuffer.reset();
   if (mCurrentInputBuffer) {
     mCurrentInputBuffer->EvictAll();
@@ -787,8 +787,8 @@ void TrackBuffersManager::SegmentParserLoop() {
           if (mPendingInputBuffer) {
             // We now have a complete media segment header. We can resume
             // parsing the data.
-            AppendDataToCurrentInputBuffer(mPendingInputBuffer);
-            mPendingInputBuffer = nullptr;
+            AppendDataToCurrentInputBuffer(*mPendingInputBuffer);
+            mPendingInputBuffer.reset();
           }
           mNewMediaSegmentStarted = false;
         } else {
@@ -797,10 +797,12 @@ void TrackBuffersManager::SegmentParserLoop() {
           // 2. If the input buffer does not contain a complete media segment
           // header yet, then jump to the need more data step below.
           if (!mPendingInputBuffer) {
-            mPendingInputBuffer = new MediaByteBuffer();
+            mPendingInputBuffer = Some(MediaSpan(*mInputBuffer));
+          } else {
+            // Note we reset mInputBuffer below, so this won't end up appending
+            // the contents of mInputBuffer to itself.
+            mPendingInputBuffer->Append(*mInputBuffer);
           }
-          mPendingInputBuffer->AppendElements(mInputBuffer->Elements(),
-                                              mInputBuffer->Length());
 
           mInputBuffer.reset();
           NeedMoreData();
@@ -974,8 +976,7 @@ void TrackBuffersManager::OnDemuxerResetDone(const MediaResult& aResult) {
     // We had a partial media segment header stashed aside.
     // Reparse its content so we can continue parsing the current input buffer.
     int64_t start, end;
-    mParser->ParseStartAndEndTimestamps(MediaSpan(mPendingInputBuffer), start,
-                                        end);
+    mParser->ParseStartAndEndTimestamps(*mPendingInputBuffer, start, end);
     mProcessedInput += mPendingInputBuffer->Length();
   }
 
@@ -989,13 +990,6 @@ void TrackBuffersManager::AppendDataToCurrentInputBuffer(
   mInputDemuxer->NotifyDataArrived();
 }
 
-void TrackBuffersManager::AppendDataToCurrentInputBuffer(
-    MediaByteBuffer* aData) {
-  MOZ_ASSERT(mCurrentInputBuffer);
-  mCurrentInputBuffer->AppendData(MediaSpan(aData));
-  mInputDemuxer->NotifyDataArrived();
-}
-
 void TrackBuffersManager::InitializationSegmentReceived() {
   MOZ_ASSERT(OnTaskQueue());
   MOZ_ASSERT(mParser->HasCompleteInitData());

dom/media/mediasource/TrackBuffersManager.h

@@ -223,14 +223,13 @@ class TrackBuffersManager final
 
   // Demuxer objects and methods.
   void AppendDataToCurrentInputBuffer(const MediaSpan& aData);
-  void AppendDataToCurrentInputBuffer(MediaByteBuffer* aData);
 
   RefPtr<MediaByteBuffer> mInitData;
   // Temporary input buffer to handle partial media segment header.
   // We store the current input buffer content into it should we need to
   // reinitialize the demuxer once we have some samples and a discontinuity is
   // detected.
-  RefPtr<MediaByteBuffer> mPendingInputBuffer;
+  Maybe<MediaSpan> mPendingInputBuffer;
   RefPtr<SourceBufferResource> mCurrentInputBuffer;
   RefPtr<MediaDataDemuxer> mInputDemuxer;
   // Length already processed in current media segment.