xpcom/threads/nsEventQueue.cpp

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   2 /* vim:set ts=2 sw=2 sts=2 et cindent: */
   3 /* ***** BEGIN LICENSE BLOCK *****
   4  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
   5  *
   6  * The contents of this file are subject to the Mozilla Public License Version
   7  * 1.1 (the "License"); you may not use this file except in compliance with
   8  * the License. You may obtain a copy of the License at
   9  * http://www.mozilla.org/MPL/
  10  *
  11  * Software distributed under the License is distributed on an "AS IS" basis,
  12  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
  13  * for the specific language governing rights and limitations under the
  14  * License.
  15  *
  16  * The Original Code is Mozilla code.
  17  *
  18  * The Initial Developer of the Original Code is Google Inc.
  19  * Portions created by the Initial Developer are Copyright (C) 2006
  20  * the Initial Developer. All Rights Reserved.
  21  *
  22  * Contributor(s):
  23  *  Darin Fisher <darin@meer.net>
  24  *
  25  * Alternatively, the contents of this file may be used under the terms of
  26  * either the GNU General Public License Version 2 or later (the "GPL"), or
  27  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
  28  * in which case the provisions of the GPL or the LGPL are applicable instead
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  34  * the provisions above, a recipient may use your version of this file under
  35  * the terms of any one of the MPL, the GPL or the LGPL.
  36  *
  37  * ***** END LICENSE BLOCK ***** */
  38
  39 #include "nsEventQueue.h"
  40 #include "nsAutoLock.h"
  41 #include "nsAutoPtr.h"
  42 #include "prlog.h"
  43 #include "nsThreadUtils.h"
  44
  45 #ifdef PR_LOGGING
  46 static PRLogModuleInfo *sLog = PR_NewLogModule("nsEventQueue");
  47 #endif
  48 #define LOG(args) PR_LOG(sLog, PR_LOG_DEBUG, args)
  49
  50 nsEventQueue::nsEventQueue()
  51   : mMonitor(nsAutoMonitor::NewMonitor("xpcom.eventqueue"))
  52   , mHead(nsnull)
  53   , mTail(nsnull)
  54   , mOffsetHead(0)
  55   , mOffsetTail(0)
  56 {
  57 }
  58
  59 nsEventQueue::~nsEventQueue()
  60 {
  61   // It'd be nice to be able to assert that no one else is holding the monitor,
  62   // but NSPR doesn't really expose APIs for it.
  63   NS_ASSERTION(IsEmpty(), "Non-empty event queue being destroyed; events being leaked.");
  64
  65   if (mHead)
  66     FreePage(mHead);
  67
  68   if (mMonitor)
  69     nsAutoMonitor::DestroyMonitor(mMonitor);
  70 }
  71
  72 PRBool
  73 nsEventQueue::GetEvent(PRBool mayWait, nsIRunnable **result)
  74 {
  75   {
  76     nsAutoMonitor mon(mMonitor);
  77
  78     while (IsEmpty()) {
  79       if (!mayWait) {
  80         if (result)
  81           *result = nsnull;
  82         return PR_FALSE;
  83       }
  84       LOG(("EVENTQ(%p): wait begin\n", this));
  85       mon.Wait();
  86       LOG(("EVENTQ(%p): wait end\n", this));
  87     }
  88
  89     if (result) {
  90       *result = mHead->mEvents[mOffsetHead++];
  91
  92       // Check if mHead points to empty Page
  93       if (mOffsetHead == EVENTS_PER_PAGE) {
  94         Page *dead = mHead;
  95         mHead = mHead->mNext;
  96         FreePage(dead);
  97         mOffsetHead = 0;
  98       }
  99     }
 100   }
 101
 102   return PR_TRUE;
 103 }
 104
 105 PRBool
 106 nsEventQueue::PutEvent(nsIRunnable *runnable)
 107 {
 108   // Avoid calling AddRef+Release while holding our monitor.
 109   nsRefPtr<nsIRunnable> event(runnable);
 110   PRBool rv = PR_TRUE;
 111   {
 112     nsAutoMonitor mon(mMonitor);
 113
 114     if (!mHead) {
 115       mHead = NewPage();
 116       if (!mHead) {
 117         rv = PR_FALSE;
 118       } else {
 119         mTail = mHead;
 120         mOffsetHead = 0;
 121         mOffsetTail = 0;
 122       }
 123     } else if (mOffsetTail == EVENTS_PER_PAGE) {
 124       Page *page = NewPage();
 125       if (!page) {
 126         rv = PR_FALSE;
 127       } else {
 128         mTail->mNext = page;
 129         mTail = page;
 130         mOffsetTail = 0;
 131       }
 132     }
 133     if (rv) {
 134       event.swap(mTail->mEvents[mOffsetTail]);
 135       ++mOffsetTail;
 136       LOG(("EVENTQ(%p): notify\n", this));
 137       mon.NotifyAll();
 138     }
 139   }
 140   return rv;
 141 }