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       1             : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
       2             : /* vim: set ts=8 sts=2 et sw=2 tw=80: */
       3             : /* This Source Code Form is subject to the terms of the Mozilla Public
       4             :  * License, v. 2.0. If a copy of the MPL was not distributed with this
       5             :  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
       6             : 
       7             : #ifndef nsIWeakReferenceUtils_h__
       8             : #define nsIWeakReferenceUtils_h__
       9             : 
      10             : #include "nsCOMPtr.h"
      11             : #include "nsIWeakReference.h"
      12             : 
      13             : typedef nsCOMPtr<nsIWeakReference> nsWeakPtr;
      14             : 
      15             : /**
      16             :  *
      17             :  */
      18             : 
      19             : // a type-safe shortcut for calling the |QueryReferent()| member function
      20             : // T must inherit from nsIWeakReference, but the cast may be ambiguous.
      21             : template<class T, class DestinationType>
      22             : inline nsresult
      23       10121 : CallQueryReferent(T* aSource, DestinationType** aDestination)
      24             : {
      25       10121 :   NS_PRECONDITION(aSource, "null parameter");
      26       10121 :   NS_PRECONDITION(aDestination, "null parameter");
      27             : 
      28             :   return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
      29       10121 :                                 reinterpret_cast<void**>(aDestination));
      30             : }
      31             : 
      32             : 
      33             : class MOZ_STACK_CLASS nsQueryReferent final : public nsCOMPtr_helper
      34             : {
      35             : public:
      36        6443 :   nsQueryReferent(nsIWeakReference* aWeakPtr, nsresult* aError)
      37        6443 :     : mWeakPtr(aWeakPtr)
      38        6443 :     , mErrorPtr(aError)
      39             :   {
      40        6443 :   }
      41             : 
      42             :   virtual nsresult NS_FASTCALL operator()(const nsIID& aIID, void**) const
      43             :     override;
      44             : 
      45             : private:
      46             :   nsIWeakReference* MOZ_NON_OWNING_REF mWeakPtr;
      47             :   nsresult*          mErrorPtr;
      48             : };
      49             : 
      50             : inline const nsQueryReferent
      51        6443 : do_QueryReferent(nsIWeakReference* aRawPtr, nsresult* aError = 0)
      52             : {
      53        6443 :   return nsQueryReferent(aRawPtr, aError);
      54             : }
      55             : 
      56             : 
      57             : /**
      58             :  * Deprecated, use |do_GetWeakReference| instead.
      59             :  */
      60             : extern nsIWeakReference* NS_GetWeakReference(nsISupports*,
      61             :                                              nsresult* aResult = 0);
      62             : 
      63             : /**
      64             :  * |do_GetWeakReference| is a convenience function that bundles up all the work needed
      65             :  * to get a weak reference to an arbitrary object, i.e., the |QueryInterface|, test, and
      66             :  * call through to |GetWeakReference|, and put it into your |nsCOMPtr|.
      67             :  * It is specifically designed to cooperate with |nsCOMPtr| (or |nsWeakPtr|) like so:
      68             :  * |nsWeakPtr myWeakPtr = do_GetWeakReference(aPtr);|.
      69             :  */
      70             : inline already_AddRefed<nsIWeakReference>
      71        2230 : do_GetWeakReference(nsISupports* aRawPtr, nsresult* aError = 0)
      72             : {
      73        2230 :   return dont_AddRef(NS_GetWeakReference(aRawPtr, aError));
      74             : }
      75             : 
      76             : inline void
      77             : do_GetWeakReference(nsIWeakReference* aRawPtr, nsresult* aError = 0)
      78             : {
      79             :   // This signature exists solely to _stop_ you from doing a bad thing.
      80             :   //  Saying |do_GetWeakReference()| on a weak reference itself,
      81             :   //  is very likely to be a programmer error.
      82             : }
      83             : 
      84             : template<class T>
      85             : inline void
      86             : do_GetWeakReference(already_AddRefed<T>&)
      87             : {
      88             :   // This signature exists solely to _stop_ you from doing the bad thing.
      89             :   //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
      90             :   //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
      91             : }
      92             : 
      93             : template<class T>
      94             : inline void
      95             : do_GetWeakReference(already_AddRefed<T>&, nsresult*)
      96             : {
      97             :   // This signature exists solely to _stop_ you from doing the bad thing.
      98             :   //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
      99             :   //  someone else is an automatic leak.  See <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
     100             : }
     101             : 
     102             : #endif