LCOV - code coverage report
Current view: directory - xpcom/threads - LazyIdleThread.h (source / functions) Found Hit Coverage
Test: app.info Lines: 2 2 100.0 %
Date: 2012-06-02 Functions: 1 1 100.0 %

       1                 : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2                 : /* vim: set ts=2 et sw=2 tw=80: */
       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 Indexed Database.
      17                 :  *
      18                 :  * The Initial Developer of the Original Code is
      19                 :  * The Mozilla Foundation.
      20                 :  * Portions created by the Initial Developer are Copyright (C) 2010
      21                 :  * the Initial Developer. All Rights Reserved.
      22                 :  *
      23                 :  * Contributor(s):
      24                 :  *   Ben Turner <bent.mozilla@gmail.com>
      25                 :  *
      26                 :  * Alternatively, the contents of this file may be used under the terms of
      27                 :  * either the GNU General Public License Version 2 or later (the "GPL"), or
      28                 :  * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      29                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      30                 :  * of those above. If you wish to allow use of your version of this file only
      31                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      32                 :  * use your version of this file under the terms of the MPL, indicate your
      33                 :  * decision by deleting the provisions above and replace them with the notice
      34                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      35                 :  * the provisions above, a recipient may use your version of this file under
      36                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      37                 :  *
      38                 :  * ***** END LICENSE BLOCK ***** */
      39                 : 
      40                 : #ifndef mozilla_lazyidlethread_h__
      41                 : #define mozilla_lazyidlethread_h__
      42                 : 
      43                 : #ifndef MOZILLA_INTERNAL_API
      44                 : #error "This header is only usable from within libxul (MOZILLA_INTERNAL_API)."
      45                 : #endif
      46                 : 
      47                 : #include "nsIObserver.h"
      48                 : #include "nsIThreadInternal.h"
      49                 : #include "nsITimer.h"
      50                 : 
      51                 : #include "mozilla/Mutex.h"
      52                 : #include "nsCOMPtr.h"
      53                 : #include "nsTArray.h"
      54                 : 
      55                 : #define IDLE_THREAD_TOPIC "thread-shutting-down"
      56                 : 
      57                 : namespace mozilla {
      58                 : 
      59                 : /**
      60                 :  * This class provides a basic event target that creates its thread lazily and
      61                 :  * destroys its thread after a period of inactivity. It may be created on any
      62                 :  * thread but it may only be used from the thread on which it is created. If it
      63                 :  * is created on the main thread then it will automatically join its thread on
      64                 :  * XPCOM shutdown using the Observer Service.
      65                 :  */
      66                 : class LazyIdleThread : public nsIThread,
      67                 :                        public nsITimerCallback,
      68                 :                        public nsIThreadObserver,
      69                 :                        public nsIObserver
      70                 : {
      71                 : public:
      72                 :   NS_DECL_ISUPPORTS
      73                 :   NS_DECL_NSIEVENTTARGET
      74                 :   NS_DECL_NSITHREAD
      75                 :   NS_DECL_NSITIMERCALLBACK
      76                 :   NS_DECL_NSITHREADOBSERVER
      77                 :   NS_DECL_NSIOBSERVER
      78                 : 
      79                 :   enum ShutdownMethod {
      80                 :     AutomaticShutdown = 0,
      81                 :     ManualShutdown
      82                 :   };
      83                 : 
      84                 :   /**
      85                 :    * Create a new LazyIdleThread that will destroy its thread after the given
      86                 :    * number of milliseconds.
      87                 :    */
      88                 :   LazyIdleThread(PRUint32 aIdleTimeoutMS,
      89                 :                  ShutdownMethod aShutdownMethod = AutomaticShutdown,
      90                 :                  nsIObserver* aIdleObserver = nsnull);
      91                 : 
      92                 :   /**
      93                 :    * Add an observer that will be notified when the thread is idle and about to
      94                 :    * be shut down. The aSubject argument can be QueryInterface'd to an nsIThread
      95                 :    * that can be used to post cleanup events. The aTopic argument will be
      96                 :    * IDLE_THREAD_TOPIC, and aData will be null. The LazyIdleThread does not add
      97                 :    * a reference to the observer to avoid circular references as it is assumed
      98                 :    * to be the owner. It is the caller's responsibility to clear this observer
      99                 :    * if the pointer becomes invalid.
     100                 :    */
     101                 :   void SetWeakIdleObserver(nsIObserver* aObserver);
     102                 : 
     103                 :   /**
     104                 :    * Disable the idle timeout for this thread. No effect if the timeout is
     105                 :    * already disabled.
     106                 :    */
     107                 :   void DisableIdleTimeout();
     108                 : 
     109                 :   /**
     110                 :    * Enable the idle timeout. No effect if the timeout is already enabled.
     111                 :    */
     112                 :   void EnableIdleTimeout();
     113                 : 
     114                 : private:
     115                 :   /**
     116                 :    * Calls Shutdown().
     117                 :    */
     118                 :   ~LazyIdleThread();
     119                 : 
     120                 :   /**
     121                 :    * Called just before dispatching to mThread.
     122                 :    */
     123                 :   void PreDispatch();
     124                 : 
     125                 :   /**
     126                 :    * Makes sure a valid thread lives in mThread.
     127                 :    */
     128                 :   nsresult EnsureThread();
     129                 : 
     130                 :   /**
     131                 :    * Called on mThread to set up the thread observer.
     132                 :    */
     133                 :   void InitThread();
     134                 : 
     135                 :   /**
     136                 :    * Called on mThread to clean up the thread observer.
     137                 :    */
     138                 :   void CleanupThread();
     139                 : 
     140                 :   /**
     141                 :    * Called on the main thread when mThread believes itself to be idle. Sets up
     142                 :    * the idle timer.
     143                 :    */
     144                 :   void ScheduleTimer();
     145                 : 
     146                 :   /**
     147                 :    * Called when we are shutting down mThread.
     148                 :    */
     149                 :   nsresult ShutdownThread();
     150                 : 
     151                 :   /**
     152                 :    * Deletes this object. Used to delay calling mThread->Shutdown() during the
     153                 :    * final release (during a GC, for instance).
     154                 :    */
     155                 :   void SelfDestruct();
     156                 : 
     157                 :   /**
     158                 :    * Returns true if events should be queued rather than immediately dispatched
     159                 :    * to mThread. Currently only happens when the thread is shutting down.
     160                 :    */
     161              84 :   bool UseRunnableQueue() {
     162              84 :     return !!mQueuedRunnables;
     163                 :   }
     164                 : 
     165                 :   /**
     166                 :    * Protects data that is accessed on both threads.
     167                 :    */
     168                 :   mozilla::Mutex mMutex;
     169                 : 
     170                 :   /**
     171                 :    * Touched on both threads but set before mThread is created. Used to direct
     172                 :    * timer events to the owning thread.
     173                 :    */
     174                 :   nsCOMPtr<nsIThread> mOwningThread;
     175                 : 
     176                 :   /**
     177                 :    * Only accessed on the owning thread. Set by EnsureThread().
     178                 :    */
     179                 :   nsCOMPtr<nsIThread> mThread;
     180                 : 
     181                 :   /**
     182                 :    * Protected by mMutex. Created when mThread has no pending events and fired
     183                 :    * at mOwningThread. Any thread that dispatches to mThread will take ownership
     184                 :    * of the timer and fire a separate cancel event to the owning thread.
     185                 :    */
     186                 :   nsCOMPtr<nsITimer> mIdleTimer;
     187                 : 
     188                 :   /**
     189                 :    * Idle observer. Called when the thread is about to be shut down. Released
     190                 :    * only when Shutdown() is called.
     191                 :    */
     192                 :   nsIObserver* mIdleObserver;
     193                 : 
     194                 :   /**
     195                 :    * Temporary storage for events that happen to be dispatched while we're in
     196                 :    * the process of shutting down our real thread.
     197                 :    */
     198                 :   nsTArray<nsCOMPtr<nsIRunnable> >* mQueuedRunnables;
     199                 : 
     200                 :   /**
     201                 :    * The number of milliseconds a thread should be idle before dying.
     202                 :    */
     203                 :   const PRUint32 mIdleTimeoutMS;
     204                 : 
     205                 :   /**
     206                 :    * The number of events that are pending on mThread. A nonzero value means
     207                 :    * that the thread cannot be cleaned up.
     208                 :    */
     209                 :   PRUint32 mPendingEventCount;
     210                 : 
     211                 :   /**
     212                 :    * The number of times that mThread has dispatched an idle notification. Any
     213                 :    * timer that fires while this count is nonzero can safely be ignored as
     214                 :    * another timer will be on the way.
     215                 :    */
     216                 :   PRUint32 mIdleNotificationCount;
     217                 : 
     218                 :   /**
     219                 :    * Whether or not the thread should automatically shutdown. If the owner
     220                 :    * specified ManualShutdown at construction time then the owner should take
     221                 :    * care to call Shutdown() manually when appropriate.
     222                 :    */
     223                 :   ShutdownMethod mShutdownMethod;
     224                 : 
     225                 :   /**
     226                 :    * Only accessed on the owning thread. Set to true when Shutdown() has been
     227                 :    * called and prevents EnsureThread() from recreating mThread.
     228                 :    */
     229                 :   bool mShutdown;
     230                 : 
     231                 :   /**
     232                 :    * Set from CleanupThread and lasting until the thread has shut down. Prevents
     233                 :    * further idle notifications during the shutdown process.
     234                 :    */
     235                 :   bool mThreadIsShuttingDown;
     236                 : 
     237                 :   /**
     238                 :    * Whether or not the idle timeout is enabled.
     239                 :    */
     240                 :   bool mIdleTimeoutEnabled;
     241                 : };
     242                 : 
     243                 : } // namespace mozilla
     244                 : 
     245                 : #endif // mozilla_lazyidlethread_h__

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