Back to index

lightning-sunbird  0.9+nobinonly
nsWeakReference.h
Go to the documentation of this file.
00001 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*-
00002  *
00003  * ***** BEGIN LICENSE BLOCK *****
00004  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00005  *
00006  * The contents of this file are subject to the Mozilla Public License Version
00007  * 1.1 (the "License"); you may not use this file except in compliance with
00008  * the License. You may obtain a copy of the License at
00009  * http://www.mozilla.org/MPL/
00010  *
00011  * Software distributed under the License is distributed on an "AS IS" basis,
00012  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
00013  * for the specific language governing rights and limitations under the
00014  * License.
00015  *
00016  * The Original Code is the Mozilla browser.
00017  *
00018  * The Initial Developer of the Original Code is
00019  * Netscape Communications, Inc.
00020  * Portions created by the Initial Developer are Copyright (C) 1999
00021  * the Initial Developer. All Rights Reserved.
00022  *
00023  * Contributor(s):
00024  *   Scott Collins <scc@netscape.com>
00025  *
00026  * Alternatively, the contents of this file may be used under the terms of
00027  * either of the GNU General Public License Version 2 or later (the "GPL"),
00028  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
00029  * in which case the provisions of the GPL or the LGPL are applicable instead
00030  * of those above. If you wish to allow use of your version of this file only
00031  * under the terms of either the GPL or the LGPL, and not to allow others to
00032  * use your version of this file under the terms of the MPL, indicate your
00033  * decision by deleting the provisions above and replace them with the notice
00034  * and other provisions required by the GPL or the LGPL. If you do not delete
00035  * the provisions above, a recipient may use your version of this file under
00036  * the terms of any one of the MPL, the GPL or the LGPL.
00037  *
00038  * ***** END LICENSE BLOCK ***** */
00039 
00040 #ifndef nsWeakReference_h__
00041 #define nsWeakReference_h__
00042 
00043 // nsWeakReference.h
00044 
00045 #include "nsIWeakReference.h"
00046 #include "nsIWeakReferenceUtils.h"
00047 
00048 class nsWeakReference;
00049 
00050 #undef  IMETHOD_VISIBILITY
00051 #define IMETHOD_VISIBILITY NS_VISIBILITY_DEFAULT
00052 
00053 class NS_COM_GLUE nsSupportsWeakReference : public nsISupportsWeakReference
00054   {
00055     public:
00056       nsSupportsWeakReference()
00057           : mProxy(0)
00058         {
00059           // nothing else to do here
00060         }
00061 
00062       NS_DECL_NSISUPPORTSWEAKREFERENCE
00063 
00064     protected:
00065       inline ~nsSupportsWeakReference();
00066 
00067     private:
00068       friend class nsWeakReference;
00069 
00070       void
00071       NoticeProxyDestruction()
00072           // ...called (only) by an |nsWeakReference| from _its_ dtor.
00073         {
00074           mProxy = 0;
00075         }
00076 
00077       nsWeakReference* mProxy;
00078 
00079               protected:
00080 
00081                      inline void ClearWeakReferences();
00082                      PRBool HasWeakReferences() const {return mProxy != 0;}
00083   };
00084 
00085 #undef  IMETHOD_VISIBILITY
00086 #define IMETHOD_VISIBILITY NS_VISIBILITY_HIDDEN
00087 
00088 class NS_COM_GLUE nsWeakReference : public nsIWeakReference
00089   {
00090     public:
00091     // nsISupports...
00092       NS_DECL_ISUPPORTS
00093 
00094     // nsIWeakReference...
00095       NS_DECL_NSIWEAKREFERENCE
00096 
00097     private:
00098       friend class nsSupportsWeakReference;
00099 
00100       nsWeakReference( nsSupportsWeakReference* referent )
00101           : mReferent(referent)
00102           // ...I can only be constructed by an |nsSupportsWeakReference|
00103         {
00104           // nothing else to do here
00105         }
00106 
00107       ~nsWeakReference()
00108            // ...I will only be destroyed by calling |delete| myself.
00109         {
00110           if ( mReferent )
00111             mReferent->NoticeProxyDestruction();
00112         }
00113 
00114       void
00115       NoticeReferentDestruction()
00116           // ...called (only) by an |nsSupportsWeakReference| from _its_ dtor.
00117         {
00118           mReferent = 0;
00119         }
00120 
00121       nsSupportsWeakReference*  mReferent;
00122   };
00123 
00124 inline
00125 void
00126 nsSupportsWeakReference::ClearWeakReferences()
00127               /*
00128                      Usually being called from |nsSupportsWeakReference::~nsSupportsWeakReference|
00129                      will be good enough, but you may have a case where you need to call disconnect
00130                      your weak references in an outer destructor (to prevent some client holding a
00131                      weak reference from re-entering your destructor).
00132               */
00133        {
00134               if ( mProxy )
00135                      {
00136                             mProxy->NoticeReferentDestruction();
00137                             mProxy = 0;
00138                      }
00139        }
00140 
00141 inline
00142 nsSupportsWeakReference::~nsSupportsWeakReference()
00143   {
00144        ClearWeakReferences();
00145   }
00146 
00147 #endif