зеркало из https://github.com/mozilla/gecko-dev.git
106 строки
4.2 KiB
C++
106 строки
4.2 KiB
C++
/* -*- 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 "nsIObserver.h"
|
|
#include "mozilla/Monitor.h"
|
|
#include "mozilla/RefPtr.h"
|
|
#include "mozilla/StaticPtr.h"
|
|
#include "nsIThread.h"
|
|
#include "nsCOMPtr.h"
|
|
#include "nsTHashtable.h"
|
|
#include "nsHashKeys.h"
|
|
|
|
namespace mozilla {
|
|
|
|
class MediaDecoder;
|
|
class StateMachineThread;
|
|
|
|
// 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. Additionally the xpcom-shutdown observer *must* block until all
|
|
// threads are shutdown, which is tricky since we have a number of threads
|
|
// here and their shutdown is asynchronous. We can't have each element of
|
|
// our pipeline listening for xpcom-shutdown, as if each observer blocks
|
|
// waiting for its threads to shutdown it will block other xpcom-shutdown
|
|
// notifications from firing, and shutdown of one part of the media pipeline
|
|
// (say the State Machine thread) may depend another part to be shutdown
|
|
// first (the MediaDecoder threads). The MediaShutdownManager encapsulates
|
|
// all these dependencies, and provides a single xpcom-shutdown listener
|
|
// for the MediaDecoder infrastructure, 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 returning from its xpcom-shutdown observer by keeping track of all
|
|
// the active MediaDecoders, and upon xpcom-shutdown calling Shutdown() on
|
|
// every MediaDecoder and then spinning the main thread event loop until all
|
|
// SharedThreadPools have shutdown. Once the SharedThreadPools are shutdown,
|
|
// all the state machines and their threads have been shutdown, the
|
|
// xpcom-shutdown observer returns.
|
|
//
|
|
// 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 nsIObserver {
|
|
public:
|
|
NS_DECL_ISUPPORTS
|
|
NS_DECL_NSIOBSERVER
|
|
|
|
// 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.
|
|
void 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 Shutdown();
|
|
|
|
// Ensures we have a shutdown listener if we need one, and removes the
|
|
// listener and destroys the singleton if we don't.
|
|
void EnsureCorrectShutdownObserverState();
|
|
|
|
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;
|
|
|
|
// True if we have an XPCOM shutdown observer.
|
|
bool mIsObservingShutdown;
|
|
|
|
bool mIsDoingXPCOMShutDown;
|
|
};
|
|
|
|
} // namespace mozilla
|
|
|
|
#endif
|