gecko/dom/base/DOMRequestHelper.jsm

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/* 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/. */
/**
* Helper object for APIs that deal with DOMRequests and Promises and need to
* release them when the window goes out of scope.
*/
const Cu = Components.utils;
const Cc = Components.classes;
const Ci = Components.interfaces;
this.EXPORTED_SYMBOLS = ["DOMRequestIpcHelper"];
Cu.import("resource://gre/modules/XPCOMUtils.jsm");
Cu.import("resource://gre/modules/Services.jsm");
XPCOMUtils.defineLazyServiceGetter(this, "cpmm",
"@mozilla.org/childprocessmessagemanager;1",
"nsIMessageListenerManager");
/**
* We use DOMRequestIpcHelperMessageListener to avoid leaking objects which
* "inherit" from DOMRequestIpcHelper.
*
* The issue is that the message manager will hold a strong ref to the message
* listener we register with it. But we don't want to hold a strong ref to the
* DOMRequestIpcHelper object, because that object may be arbitrarily large.
*
* So instead the message manager holds a strong ref to the
* DOMRequestIpcHelperMessageListener, and that holds a /weak/ ref to its
* DOMRequestIpcHelper.
*
* Additionally, we want to unhook all of these message listeners when the
* appropriate window is destroyed. We use DOMRequestIpcHelperMessageListener
* for this, too.
*/
this.DOMRequestIpcHelperMessageListener = function(aHelper, aWindow, aMessages) {
this._weakHelper = Cu.getWeakReference(aHelper);
this._messages = aMessages;
this._messages.forEach(function(msgName) {
cpmm.addWeakMessageListener(msgName, this);
}, this);
Services.obs.addObserver(this, "inner-window-destroyed", /* weakRef */ true);
// aWindow may be null; in that case, the DOMRequestIpcHelperMessageListener
// is not tied to a particular window and lives forever.
if (aWindow) {
let util = aWindow.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIDOMWindowUtils);
this._innerWindowID = util.currentInnerWindowID;
}
}
DOMRequestIpcHelperMessageListener.prototype = {
QueryInterface: XPCOMUtils.generateQI([Ci.nsIMessageListener,
Ci.nsIObserver,
Ci.nsISupportsWeakReference]),
observe: function(aSubject, aTopic, aData) {
if (aTopic !== "inner-window-destroyed") {
return;
}
let wId = aSubject.QueryInterface(Ci.nsISupportsPRUint64).data;
if (wId != this._innerWindowID) {
return;
}
this.destroy();
},
receiveMessage: function(aMsg) {
let helper = this._weakHelper.get();
if (helper) {
helper.receiveMessage(aMsg);
} else {
this.destroy();
}
},
destroy: function() {
// DOMRequestIpcHelper.destroy() calls back into this function.
if (this._destroyed) {
return;
}
this._destroyed = true;
Services.obs.removeObserver(this, "inner-window-destroyed");
this._messages.forEach(function(msgName) {
cpmm.removeWeakMessageListener(msgName, this);
}, this);
this._messages = null;
let helper = this._weakHelper.get();
if (helper) {
helper.destroyDOMRequestHelper();
}
}
}
this.DOMRequestIpcHelper = function DOMRequestIpcHelper() {
}
DOMRequestIpcHelper.prototype = {
/**
* An object which "inherits" from DOMRequestIpcHelper and declares its own
* queryInterface method MUST implement Ci.nsISupportsWeakReference.
*/
QueryInterface: XPCOMUtils.generateQI([Ci.nsISupportsWeakReference]),
initDOMRequestHelper: function(aWindow, aMessages) {
this._DOMRequestIpcHelperMessageListener =
new DOMRequestIpcHelperMessageListener(this, aWindow, aMessages);
this._window = aWindow;
this._requests = {};
this._id = this._getRandomId();
if (this._window) {
// We don't use this.innerWindowID, but other classes rely on it.
let util = this._window.QueryInterface(Ci.nsIInterfaceRequestor)
.getInterface(Ci.nsIDOMWindowUtils);
this.innerWindowID = util.currentInnerWindowID;
}
},
getRequestId: function(aRequest) {
let id = "id" + this._getRandomId();
this._requests[id] = aRequest;
return id;
},
getPromiseResolverId: function(aPromiseResolver) {
// Delegates to getRequest() since the lookup table is agnostic about
// storage.
return this.getRequestId(aPromiseResolver);
},
getRequest: function(aId) {
if (this._requests[aId])
return this._requests[aId];
},
getPromiseResolver: function(aId) {
// Delegates to getRequest() since the lookup table is agnostic about
// storage.
return this.getRequest(aId);
},
removeRequest: function(aId) {
if (this._requests[aId])
delete this._requests[aId];
},
removePromiseResolver: function(aId) {
// Delegates to getRequest() since the lookup table is agnostic about
// storage.
this.removeRequest(aId);
},
takeRequest: function(aId) {
if (!this._requests[aId])
return null;
let request = this._requests[aId];
delete this._requests[aId];
return request;
},
takePromiseResolver: function(aId) {
// Delegates to getRequest() since the lookup table is agnostic about
// storage.
return this.takeRequest(aId);
},
_getRandomId: function() {
return Cc["@mozilla.org/uuid-generator;1"].getService(Ci.nsIUUIDGenerator).generateUUID().toString();
},
destroyDOMRequestHelper: function() {
// This function is re-entrant --
// DOMRequestIpcHelperMessageListener.destroy() calls back into this
// function, and this.uninit() may also call it.
if (this._destroyed) {
return;
}
this._destroyed = true;
this._DOMRequestIpcHelperMessageListener.destroy();
this._requests = {};
this._window = null;
if(this.uninit) {
this.uninit();
}
},
createRequest: function() {
return Services.DOMRequest.createRequest(this._window);
},
/**
* createPromise() creates a new Promise, with `aPromiseInit` as the
* PromiseInit callback. The promise constructor is obtained from the
* reference to window owned by this DOMRequestIPCHelper.
*/
createPromise: function(aPromiseInit) {
return new this._window.Promise(aPromiseInit);
},
forEachRequest: function(aCallback) {
Object.keys(this._requests).forEach(function(k) {
if (this.getRequest(k) instanceof this._window.DOMRequest) {
aCallback(k);
}
}, this);
},
forEachPromiseResolver: function(aCallback) {
Object.keys(this._requests).forEach(function(k) {
if (this.getPromiseResolver(k) instanceof this._window.PromiseResolver) {
aCallback(k);
}
}, this);
},
}