gecko-dev/xpcom/threads/AbstractEventQueue.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_AbstractEventQueue_h
#define mozilla_AbstractEventQueue_h
#include "mozilla/AlreadyAddRefed.h"
#include "mozilla/Mutex.h"
class nsIRunnable;
namespace mozilla {
enum class EventPriority
{
High,
Input,
Normal,
Idle
};
// AbstractEventQueue is an abstract base class for all our unsynchronized event
// queue implementations:
// - EventQueue: A queue of runnables. Used for non-main threads.
// - PrioritizedEventQueue: Contains a queue for each priority level.
// Has heuristics to decide which queue to pop from. Events are
// pushed into the queue corresponding to their priority.
// Used for the main thread.
//
// Since AbstractEventQueue implementations are unsynchronized, they should be
// wrapped in an outer SynchronizedEventQueue implementation (like
// ThreadEventQueue).
class AbstractEventQueue
{
public:
// Add an event to the end of the queue. Implementors are free to use
// aPriority however they wish. They may ignore it if the runnable has its own
// intrinsic priority (via nsIRunnablePriority).
virtual void PutEvent(already_AddRefed<nsIRunnable>&& aEvent,
EventPriority aPriority,
const MutexAutoLock& aProofOfLock) = 0;
// Get an event from the front of the queue. aPriority is an out param. If the
// implementation supports priorities, then this should be the same priority
// that the event was pushed with. aPriority may be null. This should return
// null if the queue is non-empty but the event in front is not ready to run.
virtual already_AddRefed<nsIRunnable> GetEvent(EventPriority* aPriority,
const MutexAutoLock& aProofOfLock) = 0;
// Returns true if the queue is empty. Implies !HasReadyEvent().
virtual bool IsEmpty(const MutexAutoLock& aProofOfLock) = 0;
// Returns true if the queue is non-empty and if the event in front is ready
// to run. Implies !IsEmpty(). This should return true iff GetEvent returns a
// non-null value.
virtual bool HasReadyEvent(const MutexAutoLock& aProofOfLock) = 0;
// Returns the number of events in the queue.
virtual size_t Count(const MutexAutoLock& aProofOfLock) const = 0;
virtual void EnableInputEventPrioritization(const MutexAutoLock& aProofOfLock) = 0;
virtual void FlushInputEventPrioritization(const MutexAutoLock& aProofOfLock) = 0;
virtual void SuspendInputEventPrioritization(const MutexAutoLock& aProofOfLock) = 0;
virtual void ResumeInputEventPrioritization(const MutexAutoLock& aProofOfLock) = 0;
virtual ~AbstractEventQueue() {}
};
} // namespace mozilla
#endif // mozilla_AbstractEventQueue_h