js/xpconnect/src/XPCJSWeakReference.cpp

   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
  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
  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 }