gecko-dev/xpcom/threads/SynchronizedEventQueue.h

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/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* 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/. */
#ifndef mozilla_SynchronizedEventQueue_h
#define mozilla_SynchronizedEventQueue_h
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/AbstractEventQueue.h"
#include "mozilla/Mutex.h"
class nsIThreadObserver;
namespace mozilla {
// A SynchronizedEventQueue is an abstract class for event queues that can be
// used across threads. A SynchronizedEventQueue implementation will typically
// use locks and condition variables to guarantee consistency. The methods of
// SynchronizedEventQueue are split between ThreadTargetSink (which contains
// methods for posting events) and SynchronizedEventQueue (which contains
// methods for getting events). This split allows event targets (specifically
// ThreadEventTarget) to use a narrow interface, since they only need to post
// events.
//
// ThreadEventQueue is the canonical implementation of
// SynchronizedEventQueue. When Quantum DOM is implemented, we will use a
// different synchronized queue on the main thread, SchedulerEventQueue, which
// will handle the cooperative threading model.
class ThreadTargetSink
{
public:
NS_INLINE_DECL_THREADSAFE_REFCOUNTING(ThreadTargetSink)
virtual bool PutEvent(already_AddRefed<nsIRunnable>&& aEvent,
EventPriority aPriority) = 0;
// After this method is called, no more events can be posted.
virtual void Disconnect(const MutexAutoLock& aProofOfLock) = 0;
protected:
virtual ~ThreadTargetSink() {}
};
class SynchronizedEventQueue : public ThreadTargetSink
{
public:
virtual already_AddRefed<nsIRunnable> GetEvent(bool aMayWait,
EventPriority* aPriority) = 0;
virtual bool HasPendingEvent() = 0;
// This method atomically checks if there are pending events and, if there are
// none, forbids future events from being posted. It returns true if there
// were no pending events.
virtual bool ShutdownIfNoPendingEvents() = 0;
// These methods provide access to an nsIThreadObserver, whose methods are
// called when posting and processing events. SetObserver should only be
// called on the thread that processes events. GetObserver can be called from
// any thread. GetObserverOnThread must be used from the thread that processes
// events; it does not acquire a lock.
virtual already_AddRefed<nsIThreadObserver> GetObserver() = 0;
virtual already_AddRefed<nsIThreadObserver> GetObserverOnThread() = 0;
virtual void SetObserver(nsIThreadObserver* aObserver) = 0;
virtual void EnableInputEventPrioritization() = 0;
virtual void FlushInputEventPrioritization() = 0;
virtual void SuspendInputEventPrioritization() = 0;
virtual void ResumeInputEventPrioritization() = 0;
protected:
virtual ~SynchronizedEventQueue() {}
};
} // namespace mozilla
#endif // mozilla_SynchronizedEventQueue_h