gecko/xpcom/threads/nsEventQueue.h
2012-05-21 12:12:37 +01:00

90 lines
2.6 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/. */
#ifndef nsEventQueue_h__
#define nsEventQueue_h__
#include <stdlib.h>
#include "mozilla/ReentrantMonitor.h"
#include "nsIRunnable.h"
// A threadsafe FIFO event queue...
class nsEventQueue
{
typedef mozilla::ReentrantMonitor ReentrantMonitor;
public:
nsEventQueue();
~nsEventQueue();
// This method adds a new event to the pending event queue. The event object
// is AddRef'd if this method succeeds. This method returns true if the
// event was stored in the event queue, and it returns false if it could
// not allocate sufficient memory.
bool PutEvent(nsIRunnable *event);
// 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 mayWait, nsIRunnable **event);
// This method returns true if there is a pending event.
bool HasPendingEvent() {
return GetEvent(false, nsnull);
}
// This method returns the next pending event or null.
bool GetPendingEvent(nsIRunnable **runnable) {
return GetEvent(false, runnable);
}
// This method waits for and returns the next pending event.
bool WaitPendingEvent(nsIRunnable **runnable) {
return GetEvent(true, runnable);
}
// Expose the event queue's monitor for "power users"
ReentrantMonitor& GetReentrantMonitor() {
return mReentrantMonitor;
}
private:
bool IsEmpty() {
return !mHead || (mHead == mTail && mOffsetHead == mOffsetTail);
}
enum { EVENTS_PER_PAGE = 250 };
// Page objects are linked together to form a simple deque.
struct Page {
struct Page *mNext;
nsIRunnable *mEvents[EVENTS_PER_PAGE];
};
static Page *NewPage() {
return static_cast<Page *>(calloc(1, sizeof(Page)));
}
static void FreePage(Page *p) {
free(p);
}
ReentrantMonitor mReentrantMonitor;
Page *mHead;
Page *mTail;
PRUint16 mOffsetHead; // offset into mHead where next item is removed
PRUint16 mOffsetTail; // offset into mTail where next item is added
};
#endif // nsEventQueue_h__