1 files changed, 102 insertions, 0 deletions
diff --git a/xpcom/glue/nsIWeakReferenceUtils.h b/xpcom/glue/nsIWeakReferenceUtils.h
new file mode 100644
index 0000000000..1c84e00dfb
--- /dev/null
+++ b/xpcom/glue/nsIWeakReferenceUtils.h
@@ -0,0 +1,102 @@
+/* -*- 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)
+{
+  NS_PRECONDITION(aSource, "null parameter");
+  NS_PRECONDITION(aDestination, "null parameter");
+
+  return aSource->QueryReferent(NS_GET_TEMPLATE_IID(DestinationType),
+                                reinterpret_cast<void**>(aDestination));
+}
+
+
+class MOZ_STACK_CLASS nsQueryReferent final : public nsCOMPtr_helper
+{
+public:
+  nsQueryReferent(nsIWeakReference* aWeakPtr, nsresult* aError)
+    : mWeakPtr(aWeakPtr)
+    , mErrorPtr(aError)
+  {
+  }
+
+  virtual nsresult NS_FASTCALL operator()(const nsIID& aIID, void**) const
+    override;
+
+private:
+  nsIWeakReference* MOZ_NON_OWNING_REF mWeakPtr;
+  nsresult*          mErrorPtr;
+};
+
+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);
+
+/**
+ * |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 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