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113 lines
3.2 KiB
C++
113 lines
3.2 KiB
C++
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
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/* vim: set ts=8 sts=2 et sw=2 tw=80: */
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/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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#ifndef nsEventQueue_h__
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#define nsEventQueue_h__
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#include <stdlib.h>
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#include "mozilla/CondVar.h"
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#include "mozilla/Mutex.h"
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#include "nsIRunnable.h"
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#include "nsCOMPtr.h"
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#include "mozilla/AlreadyAddRefed.h"
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class nsThreadPool;
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// A threadsafe FIFO event queue...
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class nsEventQueue
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{
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public:
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typedef mozilla::MutexAutoLock MutexAutoLock;
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explicit nsEventQueue(mozilla::Mutex& aLock);
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~nsEventQueue();
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// This method adds a new event to the pending event queue. The queue holds
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// a strong reference to the event after this method returns. This method
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// cannot fail.
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void PutEvent(nsIRunnable* aEvent, MutexAutoLock& aProofOfLock);
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void PutEvent(already_AddRefed<nsIRunnable>&& aEvent,
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MutexAutoLock& aProofOfLock);
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// This method gets an event from the event queue. If mayWait is true, then
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// the method will block the calling thread until an event is available. If
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// the event is null, then the method returns immediately indicating whether
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// or not an event is pending. When the resulting event is non-null, the
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// caller is responsible for releasing the event object. This method does
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// not alter the reference count of the resulting event.
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bool GetEvent(bool aMayWait, nsIRunnable** aEvent,
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MutexAutoLock& aProofOfLock);
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// This method returns true if there is a pending event.
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bool HasPendingEvent(MutexAutoLock& aProofOfLock)
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{
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return GetEvent(false, nullptr, aProofOfLock);
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}
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// This method returns the next pending event or null.
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bool GetPendingEvent(nsIRunnable** aRunnable, MutexAutoLock& aProofOfLock)
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{
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return GetEvent(false, aRunnable, aProofOfLock);
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}
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size_t Count(MutexAutoLock&);
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private:
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bool IsEmpty()
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{
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return !mHead || (mHead == mTail && mOffsetHead == mOffsetTail);
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}
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enum
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{
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EVENTS_PER_PAGE = 255
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};
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// Page objects are linked together to form a simple deque.
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struct Page
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{
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struct Page* mNext;
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nsIRunnable* mEvents[EVENTS_PER_PAGE];
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};
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static_assert((sizeof(Page) & (sizeof(Page) - 1)) == 0,
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"sizeof(Page) should be a power of two to avoid heap slop.");
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static Page* NewPage()
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{
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return static_cast<Page*>(moz_xcalloc(1, sizeof(Page)));
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}
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static void FreePage(Page* aPage)
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{
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free(aPage);
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}
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Page* mHead;
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Page* mTail;
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uint16_t mOffsetHead; // offset into mHead where next item is removed
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uint16_t mOffsetTail; // offset into mTail where next item is added
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mozilla::CondVar mEventsAvailable;
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// These methods are made available to nsThreadPool as a hack, since
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// nsThreadPool needs to have its threads sleep for fixed amounts of
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// time as well as being able to wake up all threads when thread
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// limits change.
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friend class nsThreadPool;
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void Wait(PRIntervalTime aInterval)
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{
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mEventsAvailable.Wait(aInterval);
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}
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void NotifyAll()
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{
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mEventsAvailable.NotifyAll();
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}
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};
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#endif // nsEventQueue_h__
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