1 files changed, 89 insertions, 0 deletions
diff --git a/js/xpconnect/src/XPCJSWeakReference.cpp b/js/xpconnect/src/XPCJSWeakReference.cpp
new file mode 100644
index 0000000000..fbf2e22441
--- /dev/null
+++ b/js/xpconnect/src/XPCJSWeakReference.cpp
@@ -0,0 +1,89 @@
+/* -*- 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/. */
+
+#include "xpcprivate.h"
+#include "XPCJSWeakReference.h"
+
+#include "nsContentUtils.h"
+
+using namespace JS;
+
+xpcJSWeakReference::xpcJSWeakReference() = default;
+
+NS_IMPL_ISUPPORTS(xpcJSWeakReference, xpcIJSWeakReference)
+
+nsresult xpcJSWeakReference::Init(JSContext* cx, const JS::Value& object) {
+  if (!object.isObject()) {
+    return NS_OK;
+  }
+
+  JS::RootedObject obj(cx, &object.toObject());
+
+  XPCCallContext ccx(cx);
+
+  // See if the object is a wrapped native that supports weak references.
+  nsCOMPtr<nsISupports> supports = xpc::ReflectorToISupportsDynamic(obj, cx);
+  nsCOMPtr<nsISupportsWeakReference> supportsWeakRef =
+      do_QueryInterface(supports);
+  if (supportsWeakRef) {
+    supportsWeakRef->GetWeakReference(getter_AddRefs(mReferent));
+    if (mReferent) {
+      return NS_OK;
+    }
+  }
+  // If it's not a wrapped native, or it is a wrapped native that does not
+  // support weak references, fall back to getting a weak ref to the object.
+
+  // See if object is a wrapped JSObject.
+  RefPtr<nsXPCWrappedJS> wrapped;
+  nsresult rv = nsXPCWrappedJS::GetNewOrUsed(cx, obj, NS_GET_IID(nsISupports),
+                                             getter_AddRefs(wrapped));
+  if (!wrapped) {
+    NS_ERROR("can't get nsISupportsWeakReference wrapper for obj");
+    return rv;
+  }
+
+  return wrapped->GetWeakReference(getter_AddRefs(mReferent));
+}
+
+NS_IMETHODIMP
+xpcJSWeakReference::Get(JSContext* aCx, MutableHandleValue aRetval) {
+  aRetval.setNull();
+
+  if (!mReferent) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsISupports> supports = do_QueryReferent(mReferent);
+  if (!supports) {
+    return NS_OK;
+  }
+
+  nsCOMPtr<nsIXPConnectWrappedJS> wrappedObj = do_QueryInterface(supports);
+  if (!wrappedObj) {
+    // We have a generic XPCOM object that supports weak references here.
+    // Wrap it and pass it out.
+    return nsContentUtils::WrapNative(aCx, supports, &NS_GET_IID(nsISupports),
+                                      aRetval);
+  }
+
+  JS::RootedObject obj(aCx, wrappedObj->GetJSObject());
+  if (!obj) {
+    return NS_OK;
+  }
+
+  // Most users of XPCWrappedJS don't need to worry about
+  // re-wrapping because things are implicitly rewrapped by
+  // xpcconvert. However, because we're doing this directly
+  // through the native call context, we need to call
+  // JS_WrapObject().
+  if (!JS_WrapObject(aCx, &obj)) {
+    return NS_ERROR_FAILURE;
+  }
+
+  aRetval.setObject(*obj);
+  return NS_OK;
+}