gecko-dev/xpcom/threads/nsEventQueue.h

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/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim:set ts=2 sw=2 sts=2 et cindent: */
/* ***** BEGIN LICENSE BLOCK *****
* Version: MPL 1.1/GPL 2.0/LGPL 2.1
*
* The contents of this file are subject to the Mozilla Public License Version
* 1.1 (the "License"); you may not use this file except in compliance with
* the License. You may obtain a copy of the License at
* http://www.mozilla.org/MPL/
*
* Software distributed under the License is distributed on an "AS IS" basis,
* WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
* for the specific language governing rights and limitations under the
* License.
*
* The Original Code is Mozilla code.
*
* The Initial Developer of the Original Code is Google Inc.
* Portions created by the Initial Developer are Copyright (C) 2006
* the Initial Developer. All Rights Reserved.
*
* Contributor(s):
* Darin Fisher <darin@meer.net>
*
* Alternatively, the contents of this file may be used under the terms of
* either the GNU General Public License Version 2 or later (the "GPL"), or
* the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
* in which case the provisions of the GPL or the LGPL are applicable instead
* of those above. If you wish to allow use of your version of this file only
* under the terms of either the GPL or the LGPL, and not to allow others to
* use your version of this file under the terms of the MPL, indicate your
* decision by deleting the provisions above and replace them with the notice
* and other provisions required by the GPL or the LGPL. If you do not delete
* the provisions above, a recipient may use your version of this file under
* the terms of any one of the MPL, the GPL or the LGPL.
*
* ***** END LICENSE BLOCK ***** */
#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__