import FIREFOX_52_6_0esr_RELEASE from mozilla-esr52 hg repo

dom/media/MediaShutdownManager.h

@@ -0,0 +1,90 @@
+/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim:set ts=2 sw=2 sts=2 et cindent: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#if !defined(MediaShutdownManager_h_)
+#define MediaShutdownManager_h_
+
+#include "mozilla/Monitor.h"
+#include "mozilla/RefPtr.h"
+#include "mozilla/StaticPtr.h"
+#include "nsCOMPtr.h"
+#include "nsIAsyncShutdown.h"
+#include "nsIThread.h"
+#include "nsHashKeys.h"
+#include "nsTHashtable.h"
+
+namespace mozilla {
+
+class MediaDecoder;
+
+// The MediaShutdownManager manages shutting down the MediaDecoder
+// infrastructure in response to an xpcom-shutdown notification.
+// This happens when Gecko is shutting down in the middle of operation.
+// This is tricky, as there are a number of moving parts that must
+// be shutdown in a particular order. The MediaShutdownManager
+// encapsulates all these dependencies to ensure that no shutdown
+// order dependencies leak out of the MediaDecoder stack.
+// The MediaShutdownManager is a singleton.
+//
+// The MediaShutdownManager ensures that the MediaDecoder stack
+// is shutdown before exiting xpcom-shutdown stage by registering
+// itself with nsIAsyncShutdownService to receive notification
+// when the stage of shutdown has started and then calls Shutdown()
+// on every MediaDecoder. Shutdown will not proceed until all
+// MediaDecoders finish shutdown and MediaShutdownManager unregisters
+// itself from the async shutdown service.
+//
+// Note that calling the Unregister() functions may result in the singleton
+// being deleted, so don't store references to the singleton, always use the
+// singleton by derefing the referenced returned by
+// MediaShutdownManager::Instance(), which ensures that the singleton is
+// created when needed.
+// i.e. like this:
+//    MediaShutdownManager::Instance()::Unregister(someDecoder);
+//    MediaShutdownManager::Instance()::Register(someOtherDecoder);
+// Not like this:
+//  MediaShutdownManager& instance = MediaShutdownManager::Instance();
+//  instance.Unregister(someDecoder); // Warning! May delete instance!
+//  instance.Register(someOtherDecoder); // BAD! instance may be dangling!
+class MediaShutdownManager : public nsIAsyncShutdownBlocker {
+public:
+  NS_DECL_ISUPPORTS
+  NS_DECL_NSIASYNCSHUTDOWNBLOCKER
+
+  static void InitStatics();
+
+  // The MediaShutdownManager is a singleton, access its instance with
+  // this accessor.
+  static MediaShutdownManager& Instance();
+
+  // Notifies the MediaShutdownManager that it needs to track the shutdown
+  // of this MediaDecoder.
+  nsresult Register(MediaDecoder* aDecoder);
+
+  // Notifies the MediaShutdownManager that a MediaDecoder that it was
+  // tracking has shutdown, and it no longer needs to be shutdown in the
+  // xpcom-shutdown listener.
+  void Unregister(MediaDecoder* aDecoder);
+
+private:
+
+  MediaShutdownManager();
+  virtual ~MediaShutdownManager();
+  void RemoveBlocker();
+
+  static StaticRefPtr<MediaShutdownManager> sInstance;
+
+  // References to the MediaDecoder. The decoders unregister themselves
+  // in their Shutdown() method, so we'll drop the reference naturally when
+  // we're shutting down (in the non xpcom-shutdown case).
+  nsTHashtable<nsRefPtrHashKey<MediaDecoder>> mDecoders;
+
+  bool mIsDoingXPCOMShutDown = false;
+};
+
+} // namespace mozilla
+
+#endif