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