xpcom/base/nsIWeakReferenceUtils.h

   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 CallQueryReferent(T* aSource, DestinationType** aDestination) {
  23   MOZ_ASSERT(aSource, "null parameter");
  24   MOZ_ASSERT(aDestination, "null parameter");
  25
  26   return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
  27                                 reinterpret_cast<void**>(aDestination));
  28 }
  29
  30 inline const nsQueryReferent do_QueryReferent(nsIWeakReference* aRawPtr,
  31                                               nsresult* aError = 0) {
  32   return nsQueryReferent(aRawPtr, aError);
  33 }
  34
  35 /**
  36  * Deprecated, use |do_GetWeakReference| instead.
  37  */
  38 extern nsIWeakReference* NS_GetWeakReference(nsISupports*,
  39                                              nsresult* aResult = 0);
  40 extern nsIWeakReference* NS_GetWeakReference(nsISupportsWeakReference*,
  41                                              nsresult* aResult = 0);
  42
  43 /**
  44  * |do_GetWeakReference| is a convenience function that bundles up all the work
  45  * needed to get a weak reference to an arbitrary object, i.e., the
  46  * |QueryInterface|, test, and call through to |GetWeakReference|, and put it
  47  * into your |nsCOMPtr|. It is specifically designed to cooperate with
  48  * |nsCOMPtr| (or |nsWeakPtr|) like so: |nsWeakPtr myWeakPtr =
  49  * do_GetWeakReference(aPtr);|.
  50  */
  51 inline already_AddRefed<nsIWeakReference> do_GetWeakReference(
  52     nsISupports* aRawPtr, nsresult* aError = 0) {
  53   return dont_AddRef(NS_GetWeakReference(aRawPtr, aError));
  54 }
  55
  56 inline already_AddRefed<nsIWeakReference> do_GetWeakReference(
  57     nsISupportsWeakReference* aRawPtr, nsresult* aError = 0) {
  58   return dont_AddRef(NS_GetWeakReference(aRawPtr, aError));
  59 }
  60
  61 inline void do_GetWeakReference(nsIWeakReference* aRawPtr,
  62                                 nsresult* aError = 0) {
  63   // This signature exists solely to _stop_ you from doing a bad thing.
  64   //  Saying |do_GetWeakReference()| on a weak reference itself,
  65   //  is very likely to be a programmer error.
  66 }
  67
  68 template <class T>
  69 inline void do_GetWeakReference(already_AddRefed<T>&) {
  70   // This signature exists solely to _stop_ you from doing the bad thing.
  71   //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
  72   //  someone else is an automatic leak.  See
  73   //  <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
  74 }
  75
  76 template <class T>
  77 inline void do_GetWeakReference(already_AddRefed<T>&, nsresult*) {
  78   // This signature exists solely to _stop_ you from doing the bad thing.
  79   //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
  80   //  someone else is an automatic leak.  See
  81   //  <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
  82 }
  83
  84 #endif