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 #include "xpcprivate.h"
8 #include "XPCJSWeakReference.h"
9
10 #include "nsContentUtils.h"
11
12 using namespace JS;
13
14 xpcJSWeakReference::xpcJSWeakReference() = default;
15
NS_IMPL_ISUPPORTS(xpcJSWeakReference,xpcIJSWeakReference)16 NS_IMPL_ISUPPORTS(xpcJSWeakReference, xpcIJSWeakReference)
17
18 nsresult xpcJSWeakReference::Init(JSContext* cx, const JS::Value& object) {
19 if (!object.isObject()) {
20 return NS_OK;
21 }
22
23 JS::RootedObject obj(cx, &object.toObject());
24
25 XPCCallContext ccx(cx);
26
27 // See if the object is a wrapped native that supports weak references.
28 nsCOMPtr<nsISupports> supports = xpc::ReflectorToISupportsDynamic(obj, cx);
29 nsCOMPtr<nsISupportsWeakReference> supportsWeakRef =
30 do_QueryInterface(supports);
31 if (supportsWeakRef) {
32 supportsWeakRef->GetWeakReference(getter_AddRefs(mReferent));
33 if (mReferent) {
34 return NS_OK;
35 }
36 }
37 // If it's not a wrapped native, or it is a wrapped native that does not
38 // support weak references, fall back to getting a weak ref to the object.
39
40 // See if object is a wrapped JSObject.
41 RefPtr<nsXPCWrappedJS> wrapped;
42 nsresult rv = nsXPCWrappedJS::GetNewOrUsed(cx, obj, NS_GET_IID(nsISupports),
43 getter_AddRefs(wrapped));
44 if (!wrapped) {
45 NS_ERROR("can't get nsISupportsWeakReference wrapper for obj");
46 return rv;
47 }
48
49 return wrapped->GetWeakReference(getter_AddRefs(mReferent));
50 }
51
52 NS_IMETHODIMP
Get(JSContext * aCx,MutableHandleValue aRetval)53 xpcJSWeakReference::Get(JSContext* aCx, MutableHandleValue aRetval) {
54 aRetval.setNull();
55
56 if (!mReferent) {
57 return NS_OK;
58 }
59
60 nsCOMPtr<nsISupports> supports = do_QueryReferent(mReferent);
61 if (!supports) {
62 return NS_OK;
63 }
64
65 nsCOMPtr<nsIXPConnectWrappedJS> wrappedObj = do_QueryInterface(supports);
66 if (!wrappedObj) {
67 // We have a generic XPCOM object that supports weak references here.
68 // Wrap it and pass it out.
69 return nsContentUtils::WrapNative(aCx, supports, &NS_GET_IID(nsISupports),
70 aRetval);
71 }
72
73 JS::RootedObject obj(aCx, wrappedObj->GetJSObject());
74 if (!obj) {
75 return NS_OK;
76 }
77
78 // Most users of XPCWrappedJS don't need to worry about
79 // re-wrapping because things are implicitly rewrapped by
80 // xpcconvert. However, because we're doing this directly
81 // through the native call context, we need to call
82 // JS_WrapObject().
83 if (!JS_WrapObject(aCx, &obj)) {
84 return NS_ERROR_FAILURE;
85 }
86
87 aRetval.setObject(*obj);
88 return NS_OK;
89 }
90