Bug 1195073: [MSE/webm] P4. Limit nestegg reads to the last block's boundaries. r=kinetik

This prevent entering into an unrecoverable error state when parsing incomplete data as often seen with MSE.

dom/media/mediasource/SourceBufferResource.h

@@ -100,6 +100,11 @@ public:
     return aMallocSizeOf(this) + SizeOfExcludingThis(aMallocSizeOf);
   }
 
+  virtual bool IsExpectingMoreData() override
+  {
+    return false;
+  }
+
   // Used by SourceBuffer.
   void AppendData(MediaByteBuffer* aData);
   void Ended();

dom/media/webm/WebMDemuxer.cpp

@@ -36,40 +36,39 @@ extern PRLogModuleInfo* gNesteggLog;
 
 // Functions for reading and seeking using WebMDemuxer required for
 // nestegg_io. The 'user data' passed to these functions is the
-// demuxer's MediaResourceIndex
+// demuxer.
 static int webmdemux_read(void* aBuffer, size_t aLength, void* aUserData)
 {
   MOZ_ASSERT(aUserData);
-  MediaResourceIndex* resource =
-    reinterpret_cast<MediaResourceIndex*>(aUserData);
-  int64_t length = resource->GetLength();
   MOZ_ASSERT(aLength < UINT32_MAX);
+  WebMDemuxer* demuxer = reinterpret_cast<WebMDemuxer*>(aUserData);
+  int64_t length = demuxer->GetEndDataOffset();
   uint32_t count = aLength;
-  if (length >= 0 && count + resource->Tell() > length) {
-    count = uint32_t(length - resource->Tell());
+  int64_t position = demuxer->GetResource()->Tell();
+  if (length >= 0 && count + position > length) {
+    count = length - position;
   }
 
   uint32_t bytes = 0;
-  nsresult rv = resource->Read(static_cast<char*>(aBuffer), count, &bytes);
-  bool eof = !bytes;
+  nsresult rv =
+    demuxer->GetResource()->Read(static_cast<char*>(aBuffer), count, &bytes);
+  bool eof = bytes < aLength;
   return NS_FAILED(rv) ? -1 : eof ? 0 : 1;
 }
 
 static int webmdemux_seek(int64_t aOffset, int aWhence, void* aUserData)
 {
   MOZ_ASSERT(aUserData);
-  MediaResourceIndex* resource =
-    reinterpret_cast<MediaResourceIndex*>(aUserData);
-  nsresult rv = resource->Seek(aWhence, aOffset);
+  WebMDemuxer* demuxer = reinterpret_cast<WebMDemuxer*>(aUserData);
+  nsresult rv = demuxer->GetResource()->Seek(aWhence, aOffset);
   return NS_SUCCEEDED(rv) ? 0 : -1;
 }
 
 static int64_t webmdemux_tell(void* aUserData)
 {
   MOZ_ASSERT(aUserData);
-  MediaResourceIndex* resource =
-    reinterpret_cast<MediaResourceIndex*>(aUserData);
-  return resource->Tell();
+  WebMDemuxer* demuxer = reinterpret_cast<WebMDemuxer*>(aUserData);
+  return demuxer->GetResource()->Tell();
 }
 
 static void webmdemux_log(nestegg* aContext,
@@ -130,6 +129,8 @@ WebMDemuxer::WebMDemuxer(MediaResource* aResource)
   , mHasVideo(false)
   , mHasAudio(false)
   , mNeedReIndex(true)
+  , mLastWebMBlockOffset(-1)
+  , mIsExpectingMoreData(true)
 {
   if (!gNesteggLog) {
     gNesteggLog = PR_NewLogModule("Nestegg");
@@ -254,7 +255,7 @@ WebMDemuxer::ReadMetadata()
   io.read = webmdemux_read;
   io.seek = webmdemux_seek;
   io.tell = webmdemux_tell;
-  io.userdata = &mResource;
+  io.userdata = this;
   int64_t maxOffset = mBufferedState->GetInitEndOffset();
   if (maxOffset == -1) {
     maxOffset = mResource.GetLength();
@@ -443,6 +444,8 @@ WebMDemuxer::EnsureUpToDateIndex()
   if (!mInitData && mBufferedState->GetInitEndOffset() != -1) {
     mInitData = mResource.MediaReadAt(0, mBufferedState->GetInitEndOffset());
   }
+  mLastWebMBlockOffset = mBufferedState->GetLastBlockOffset();
+  mIsExpectingMoreData = mResource.GetResource()->IsExpectingMoreData();
   mNeedReIndex = false;
 }
 
@@ -469,6 +472,8 @@ WebMDemuxer::GetCrypto()
 bool
 WebMDemuxer::GetNextPacket(TrackInfo::TrackType aType, MediaRawDataQueue *aSamples)
 {
+  EnsureUpToDateIndex();
+
   nsRefPtr<NesteggPacketHolder> holder(NextPacket(aType));
 
   if (!holder) {

dom/media/webm/WebMDemuxer.h

@@ -85,6 +85,18 @@ public:
   // Pushes a packet to the front of the video packet queue.
   virtual void PushVideoPacket(NesteggPacketHolder* aItem);
 
+  // Public accessor for nestegg callbacks
+  MediaResourceIndex* GetResource()
+  {
+    return &mResource;
+  }
+
+  int64_t GetEndDataOffset()
+  {
+    return mLastWebMBlockOffset < 0 || mIsExpectingMoreData
+      ? mResource.GetLength() : mLastWebMBlockOffset;
+  }
+
 private:
   friend class WebMTrackDemuxer;
 
@@ -152,6 +164,12 @@ private:
   bool mHasVideo;
   bool mHasAudio;
   bool mNeedReIndex;
+
+  // The last complete block parsed by the WebMBufferedState. -1 if not set.
+  // We cache those values rather than retrieving them for performance reasons
+  // as nestegg only performs 1-byte read at a time.
+  int64_t mLastWebMBlockOffset;
+  bool mIsExpectingMoreData;
 };
 
 class WebMTrackDemuxer : public MediaTrackDemuxer