Bug 1374441 - Backed out bug 1374173 (MediaCacheStream Seek&Read refactoring) - r=jwwang

Bug 1374173 seems to be the cause of all MediaCache intermittent assertion
failures. It's not an important bug, so let's back-out and verify that
intermittents disappear.

MozReview-Commit-ID: 2X8iW1hWu99

--HG--
extra : rebase_source : e22443a5b9d5ba9a6ce4b126953a880e8e469cd2

dom/media/MediaCache.cpp

@@ -2243,20 +2243,36 @@ MediaCacheStream::SetPlaybackRate(uint32_t aBytesPerSecond)
 }
 
 nsresult
-MediaCacheStream::SeekInternal(int64_t aOffset)
+MediaCacheStream::Seek(int32_t aWhence, int64_t aOffset)
 {
-  if (aOffset < 0) {
-    return NS_ERROR_FAILURE;
-  }
+  NS_ASSERTION(!NS_IsMainThread(), "Don't call on main thread");
 
-  mMediaCache->GetReentrantMonitor().AssertCurrentThreadIn();
-
-  if (mClosed) {
+  ReentrantMonitorAutoEnter mon(mMediaCache->GetReentrantMonitor());
+  if (mClosed)
     return NS_ERROR_FAILURE;
-  }
 
   int64_t oldOffset = mStreamOffset;
-  mStreamOffset = aOffset;
+  int64_t newOffset = mStreamOffset;
+  switch (aWhence) {
+  case PR_SEEK_END:
+    if (mStreamLength < 0)
+      return NS_ERROR_FAILURE;
+    newOffset = mStreamLength + aOffset;
+    break;
+  case PR_SEEK_CUR:
+    newOffset += aOffset;
+    break;
+  case PR_SEEK_SET:
+    newOffset = aOffset;
+    break;
+  default:
+    NS_ERROR("Unknown whence");
+    return NS_ERROR_FAILURE;
+  }
+
+  if (newOffset < 0)
+    return NS_ERROR_FAILURE;
+  mStreamOffset = newOffset;
 
   LOG("Stream %p Seek to %" PRId64, this, mStreamOffset);
   mMediaCache->NoteSeek(this, oldOffset);
@@ -2285,10 +2301,11 @@ MediaCacheStream::Tell()
 }
 
 nsresult
-MediaCacheStream::ReadInternal(char* aBuffer, uint32_t aCount, uint32_t* aBytes)
+MediaCacheStream::Read(char* aBuffer, uint32_t aCount, uint32_t* aBytes)
 {
-  mMediaCache->GetReentrantMonitor().AssertCurrentThreadIn();
+  NS_ASSERTION(!NS_IsMainThread(), "Don't call on main thread");
 
+  ReentrantMonitorAutoEnter mon(mMediaCache->GetReentrantMonitor());
   if (mClosed)
     return NS_ERROR_FAILURE;
 
@@ -2357,7 +2374,7 @@ MediaCacheStream::ReadInternal(char* aBuffer, uint32_t aCount, uint32_t* aBytes)
       }
 
       // No data has been read yet, so block
-      mMediaCache->GetReentrantMonitor().Wait();
+      mon.Wait();
       if (mClosed) {
         // We may have successfully read some data, but let's just throw
         // that out.
@@ -2402,9 +2419,9 @@ MediaCacheStream::ReadAt(int64_t aOffset, char* aBuffer,
   NS_ASSERTION(!NS_IsMainThread(), "Don't call on main thread");
 
   ReentrantMonitorAutoEnter mon(mMediaCache->GetReentrantMonitor());
-  nsresult rv = SeekInternal(aOffset);
+  nsresult rv = Seek(nsISeekableStream::NS_SEEK_SET, aOffset);
   if (NS_FAILED(rv)) return rv;
-  return ReadInternal(aBuffer, aCount, aBytes);
+  return Read(aBuffer, aCount, aBytes);
 }
 
 nsresult

dom/media/MediaCache.h

@@ -335,12 +335,17 @@ public:
   // These methods must be called on a different thread from the main
   // thread. They should always be called on the same thread for a given
   // stream.
+  // This can fail when aWhence is NS_SEEK_END and no stream length
+  // is known.
+  nsresult Seek(int32_t aWhence, int64_t aOffset);
   int64_t Tell();
-  // Seeks to aOffset in the stream then performs a Read operation.
   // *aBytes gets the number of bytes that were actually read. This can
   // be less than aCount. If the first byte of data is not in the cache,
   // this will block until the data is available or the stream is
   // closed, otherwise it won't block.
+  nsresult Read(char* aBuffer, uint32_t aCount, uint32_t* aBytes);
+  // Seeks to aOffset in the stream then performs a Read operation. See
+  // 'Read' for argument and return details.
   nsresult ReadAt(int64_t aOffset, char* aBuffer,
                   uint32_t aCount, uint32_t* aBytes);
 
@@ -434,13 +439,6 @@ private:
   // Update mPrincipal given that data has been received from aPrincipal
   bool UpdatePrincipal(nsIPrincipal* aPrincipal);
 
-  nsresult SeekInternal(int64_t aOffset);
-  // *aBytes gets the number of bytes that were actually read. This can
-  // be less than aCount. If the first byte of data is not in the cache,
-  // this will block until the data is available or the stream is
-  // closed, otherwise it won't block.
-  nsresult ReadInternal(char* aBuffer, uint32_t aCount, uint32_t* aBytes);
-
   // Instance of MediaCache to use with this MediaCacheStream.
   RefPtr<MediaCache> mMediaCache;