Bug 1364001. P1 - add an API to throttle download. r=cpearce

MozReview-Commit-ID: HdmAgvo1GE3

--HG--
extra : rebase_source : 97f0aa3e40c6c774ad7681ee2aae69393c47e741
extra : intermediate-source : 9f2e1751e19f88625d2a89dba0b1648f97d2478f
extra : source : b68fed514292e5e8c7815633052daeee24f64a95

dom/media/MediaCache.cpp

@@ -24,8 +24,10 @@
 namespace mozilla {
 
 #undef LOG
+#undef LOGI
 LazyLogModule gMediaCacheLog("MediaCache");
 #define LOG(...) MOZ_LOG(gMediaCacheLog, LogLevel::Debug, (__VA_ARGS__))
+#define LOGI(...) MOZ_LOG(gMediaCacheLog, LogLevel::Info, (__VA_ARGS__))
 
 
 // Readahead blocks for non-seekable streams will be limited to this
@@ -1243,12 +1245,14 @@ MediaCache::Update()
       } else {
         TimeDuration predictedNewDataUse = PredictNextUseForIncomingData(stream);
 
-        if (stream->mCacheSuspended &&
+        if (stream->mThrottleReadahead &&
+            stream->mCacheSuspended &&
             predictedNewDataUse.ToSeconds() > resumeThreshold) {
           // Don't need data for a while, so don't bother waking up the stream
           LOG("Stream %p avoiding wakeup since more data is not needed", stream);
           enableReading = false;
-        } else if (predictedNewDataUse.ToSeconds() > readaheadLimit) {
+        } else if (stream->mThrottleReadahead &&
+                   predictedNewDataUse.ToSeconds() > readaheadLimit) {
           // Don't read ahead more than this much
           LOG("Stream %p throttling to avoid reading ahead too far", stream);
           enableReading = false;
@@ -2208,6 +2212,18 @@ MediaCacheStream::Seek(int32_t aWhence, int64_t aOffset)
   return NS_OK;
 }
 
+void
+MediaCacheStream::ThrottleReadahead(bool bThrottle)
+{
+  MOZ_ASSERT(NS_IsMainThread());
+  if (mThrottleReadahead != bThrottle) {
+    LOGI("Stream %p ThrottleReadahead %d", this, bThrottle);
+    mThrottleReadahead = bThrottle;
+    ReentrantMonitorAutoEnter mon(gMediaCache->GetReentrantMonitor());
+    gMediaCache->QueueUpdate();
+  }
+}
+
 int64_t
 MediaCacheStream::Tell()
 {
@@ -2490,3 +2506,4 @@ nsresult MediaCacheStream::GetCachedRanges(MediaByteRangeSet& aRanges)
 
 // avoid redefined macro in unified build
 #undef LOG
+#undef LOGI

dom/media/MediaCache.h

@@ -348,6 +348,8 @@ public:
   nsresult ReadAt(int64_t aOffset, char* aBuffer,
                   uint32_t aCount, uint32_t* aBytes);
 
+  void ThrottleReadahead(bool bThrottle);
+
   size_t SizeOfExcludingThis(MallocSizeOf aMallocSizeOf) const;
 
 private:
@@ -514,6 +516,8 @@ private:
 
   // True if associated with a private browsing window.
   const bool mIsPrivateBrowsing;
+
+  bool mThrottleReadahead = false;
 };
 
 } // namespace mozilla

dom/media/MediaResource.cpp

@@ -716,6 +716,12 @@ ChannelMediaResource::MediaReadAt(int64_t aOffset, uint32_t aCount)
   return bytes.forget();
 }
 
+void
+ChannelMediaResource::ThrottleReadahead(bool bThrottle)
+{
+  mCacheStream.ThrottleReadahead(bThrottle);
+}
+
 int64_t ChannelMediaResource::Tell()
 {
   return mCacheStream.Tell();

dom/media/MediaResource.h

@@ -253,6 +253,11 @@ public:
     return bytes.forget();
   }
 
+  // Pass true to limit the amount of readahead data (specified by
+  // "media.cache_readahead_limit") or false to read as much as the
+  // cache size allows.
+  virtual void ThrottleReadahead(bool bThrottle) { }
+
   // Report the current offset in bytes from the start of the stream.
   // This is used to approximate where we currently are in the playback of a
   // media.
@@ -556,6 +561,8 @@ public:
   // Resume the current load since data is wanted again
   nsresult CacheClientResume();
 
+  void ThrottleReadahead(bool bThrottle) override;
+
   // Ensure that the media cache writes any data held in its partial block.
   // Called on the main thread.
   void FlushCache() override;