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 CallQueryReferent(T* aSource, DestinationType** aDestination)
24 {
25 NS_PRECONDITION(aSource, "null parameter");
26 NS_PRECONDITION(aDestination, "null parameter");
27
28 return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
29 reinterpret_cast<void**>(aDestination));
30 }
31
32
33 class MOZ_STACK_CLASS nsQueryReferent final : public nsCOMPtr_helper
34 {
35 public:
nsQueryReferent(nsIWeakReference * aWeakPtr,nsresult * aError)36 nsQueryReferent(nsIWeakReference* aWeakPtr, nsresult* aError)
37 : mWeakPtr(aWeakPtr)
38 , mErrorPtr(aError)
39 {
40 }
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 do_QueryReferent(nsIWeakReference* aRawPtr, nsresult* aError = 0)
52 {
53 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 do_GetWeakReference(nsISupports* aRawPtr, nsresult* aError = 0)
72 {
73 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
do_GetWeakReference(already_AddRefed<T> &)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
do_GetWeakReference(already_AddRefed<T> &,nsresult *)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
103