1 files changed, 84 insertions, 0 deletions
diff --git a/xpcom/base/nsIWeakReferenceUtils.h b/xpcom/base/nsIWeakReferenceUtils.h
new file mode 100644
index 0000000000..b76303096e
--- /dev/null
+++ b/xpcom/base/nsIWeakReferenceUtils.h
@@ -0,0 +1,84 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#ifndef nsIWeakReferenceUtils_h__
+#define nsIWeakReferenceUtils_h__
+
+#include "nsCOMPtr.h"
+#include "nsIWeakReference.h"
+
+typedef nsCOMPtr<nsIWeakReference> nsWeakPtr;
+
+/**
+ *
+ */
+
+// a type-safe shortcut for calling the |QueryReferent()| member function
+// T must inherit from nsIWeakReference, but the cast may be ambiguous.
+template <class T, class DestinationType>
+inline nsresult CallQueryReferent(T* aSource, DestinationType** aDestination) {
+  MOZ_ASSERT(aSource, "null parameter");
+  MOZ_ASSERT(aDestination, "null parameter");
+
+  return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
+                                reinterpret_cast<void**>(aDestination));
+}
+
+inline const nsQueryReferent do_QueryReferent(nsIWeakReference* aRawPtr,
+                                              nsresult* aError = 0) {
+  return nsQueryReferent(aRawPtr, aError);
+}
+
+/**
+ * Deprecated, use |do_GetWeakReference| instead.
+ */
+extern nsIWeakReference* NS_GetWeakReference(nsISupports*,
+                                             nsresult* aResult = 0);
+extern nsIWeakReference* NS_GetWeakReference(nsISupportsWeakReference*,
+                                             nsresult* aResult = 0);
+
+/**
+ * |do_GetWeakReference| is a convenience function that bundles up all the work
+ * needed to get a weak reference to an arbitrary object, i.e., the
+ * |QueryInterface|, test, and call through to |GetWeakReference|, and put it
+ * into your |nsCOMPtr|. It is specifically designed to cooperate with
+ * |nsCOMPtr| (or |nsWeakPtr|) like so: |nsWeakPtr myWeakPtr =
+ * do_GetWeakReference(aPtr);|.
+ */
+inline already_AddRefed<nsIWeakReference> do_GetWeakReference(
+    nsISupports* aRawPtr, nsresult* aError = 0) {
+  return dont_AddRef(NS_GetWeakReference(aRawPtr, aError));
+}
+
+inline already_AddRefed<nsIWeakReference> do_GetWeakReference(
+    nsISupportsWeakReference* aRawPtr, nsresult* aError = 0) {
+  return dont_AddRef(NS_GetWeakReference(aRawPtr, aError));
+}
+
+inline void do_GetWeakReference(nsIWeakReference* aRawPtr,
+                                nsresult* aError = 0) {
+  // This signature exists solely to _stop_ you from doing a bad thing.
+  //  Saying |do_GetWeakReference()| on a weak reference itself,
+  //  is very likely to be a programmer error.
+}
+
+template <class T>
+inline void do_GetWeakReference(already_AddRefed<T>&) {
+  // This signature exists solely to _stop_ you from doing the bad thing.
+  //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
+  //  someone else is an automatic leak.  See
+  //  <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
+}
+
+template <class T>
+inline void do_GetWeakReference(already_AddRefed<T>&, nsresult*) {
+  // This signature exists solely to _stop_ you from doing the bad thing.
+  //  Saying |do_GetWeakReference()| on a pointer that is not otherwise owned by
+  //  someone else is an automatic leak.  See
+  //  <http://bugzilla.mozilla.org/show_bug.cgi?id=8221>.
+}
+
+#endif