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nsIWeakReferenceUtils.h
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00002 /* ***** BEGIN LICENSE BLOCK *****
00003  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
00004  *
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00010  * Software distributed under the License is distributed on an "AS IS" basis,
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00014  *
00015  * The Original Code is mozilla.org code.
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00017  * The Initial Developer of the Original Code is
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00019  * Portions created by the Initial Developer are Copyright (C) 1998
00020  * the Initial Developer. All Rights Reserved.
00021  *
00022  * Contributor(s):
00023  *   Scott Collins <scc@mozilla.org> (Original Author)
00024  *
00025  * Alternatively, the contents of this file may be used under the terms of
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00038 
00039 #ifndef nsIWeakReferenceUtils_h__
00040 #define nsIWeakReferenceUtils_h__
00041 
00042 #ifndef nsCOMPtr_h__
00043 #include "nsCOMPtr.h"
00044 #endif
00045 
00046 typedef nsCOMPtr<nsIWeakReference> nsWeakPtr;
00047 
00052 // a type-safe shortcut for calling the |QueryReferent()| member function
00053 // T must inherit from nsIWeakReference, but the cast may be ambiguous.
00054 template <class T, class DestinationType>
00055 inline
00056 nsresult
00057 CallQueryReferent( T* aSource, DestinationType** aDestination )
00058   {
00059     NS_PRECONDITION(aSource, "null parameter");
00060     NS_PRECONDITION(aDestination, "null parameter");
00061 
00062     return aSource->QueryReferent(NS_GET_IID(DestinationType),
00063                                   NS_REINTERPRET_CAST(void**, aDestination));
00064   }
00065 
00066 
00067 class NS_COM_GLUE nsQueryReferent : public nsCOMPtr_helper
00068   {
00069     public:
00070       nsQueryReferent( nsIWeakReference* aWeakPtr, nsresult* error )
00071           : mWeakPtr(aWeakPtr),
00072             mErrorPtr(error)
00073         {
00074           // nothing else to do here
00075         }
00076 
00077       virtual nsresult NS_FASTCALL operator()( const nsIID& aIID, void** ) const;
00078 
00079     private:
00080       nsIWeakReference*  mWeakPtr;
00081       nsresult*          mErrorPtr;
00082   };
00083 
00084 inline
00085 const nsQueryReferent
00086 do_QueryReferent( nsIWeakReference* aRawPtr, nsresult* error = 0 )
00087   {
00088     return nsQueryReferent(aRawPtr, error);
00089   }
00090 
00091 
00095 extern NS_COM_GLUE
00096 nsIWeakReference*
00097 NS_GetWeakReference( nsISupports* , nsresult* aResult=0 );
00098 
00106 inline
00107 already_AddRefed<nsIWeakReference>
00108 do_GetWeakReference( nsISupports* aRawPtr, nsresult* error = 0 )
00109   {
00110     return NS_GetWeakReference(aRawPtr, error);
00111   }
00112 
00113 inline
00114 void
00115 do_GetWeakReference( nsIWeakReference* aRawPtr, nsresult* error = 0 )
00116   {
00117     // This signature exists soley to _stop_ you from doing a bad thing.
00118     //  Saying |do_GetWeakReference()| on a weak reference itself,
00119     //  is very likely to be a programmer error.
00120   }
00121 
00122 template <class T>
00123 inline
00124 void
00125 do_GetWeakReference( already_AddRefed<T>& )
00126   {
00127     // This signature exists soley to _stop_ you from doing the bad thing.
00128     //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
00129     //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
00130   }
00131 
00132 template <class T>
00133 inline
00134 void
00135 do_GetWeakReference( already_AddRefed<T>&, nsresult* )
00136   {
00137     // This signature exists soley to _stop_ you from doing the bad thing.
00138     //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
00139     //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
00140   }
00141 
00142 #endif