The Tor Browser / file diff

     1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/addon-sdk/source/lib/sdk/core/observer.js	Wed Dec 31 06:09:35 2014 +0100
     1.3 @@ -0,0 +1,87 @@
     1.4 +/* This Source Code Form is subject to the terms of the Mozilla Public
     1.5 + * License, v. 2.0. If a copy of the MPL was not distributed with this
     1.6 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
     1.7 +
     1.8 +"use strict";
     1.9 +
    1.10 +module.metadata = {
    1.11 +  "stability": "experimental"
    1.12 +};
    1.13 +
    1.14 +
    1.15 +const { Cc, Ci, Cr } = require("chrome");
    1.16 +const { Class } = require("./heritage");
    1.17 +const { isWeak } = require("./reference");
    1.18 +const method = require("../../method/core");
    1.19 +
    1.20 +const { addObserver, removeObserver } = Cc['@mozilla.org/observer-service;1'].
    1.21 +                                          getService(Ci.nsIObserverService);
    1.22 +
    1.23 +
    1.24 +// This is a method that will be invoked when notification observer
    1.25 +// subscribed to occurs.
    1.26 +const observe = method("observer/observe");
    1.27 +exports.observe = observe;
    1.28 +
    1.29 +// Method to subscribe to the observer notification.
    1.30 +const subscribe = method("observe/subscribe");
    1.31 +exports.subscribe = subscribe;
    1.32 +
    1.33 +
    1.34 +// Method to unsubscribe from the observer notifications.
    1.35 +const unsubscribe = method("observer/unsubscribe");
    1.36 +exports.unsubscribe = unsubscribe;
    1.37 +
    1.38 +
    1.39 +// This is wrapper class that takes a `delegate` and produces
    1.40 +// instance of `nsIObserver` which will delegate to a given
    1.41 +// object when observer notification occurs.
    1.42 +const ObserverDelegee = Class({
    1.43 +  initialize: function(delegate) {
    1.44 +    this.delegate = delegate;
    1.45 +  },
    1.46 +  QueryInterface: function(iid) {
    1.47 +    const isObserver = iid.equals(Ci.nsIObserver);
    1.48 +    const isWeakReference = iid.equals(Ci.nsISupportsWeakReference);
    1.49 +
    1.50 +    if (!isObserver && !isWeakReference)
    1.51 +      throw Cr.NS_ERROR_NO_INTERFACE;
    1.52 +
    1.53 +    return this;
    1.54 +  },
    1.55 +  observe: function(subject, topic, data) {
    1.56 +    observe(this.delegate, subject, topic, data);
    1.57 +  }
    1.58 +});
    1.59 +
    1.60 +
    1.61 +// Class that can be either mixed in or inherited from in
    1.62 +// order to subscribe / unsubscribe for observer notifications.
    1.63 +const Observer = Class({});
    1.64 +exports.Observer = Observer;
    1.65 +
    1.66 +// Weak maps that associates instance of `ObserverDelegee` with
    1.67 +// an actual observer. It ensures that `ObserverDelegee` instance
    1.68 +// won't be GC-ed until given `observer` is.
    1.69 +const subscribers = new WeakMap();
    1.70 +
    1.71 +// Implementation of `subscribe` for `Observer` type just registers
    1.72 +// observer for an observer service. If `isWeak(observer)` is `true`
    1.73 +// observer service won't hold strong reference to a given `observer`.
    1.74 +subscribe.define(Observer, (observer, topic) => {
    1.75 +  if (!subscribers.has(observer)) {
    1.76 +    const delegee = new ObserverDelegee(observer);
    1.77 +    subscribers.set(observer, delegee);
    1.78 +    addObserver(delegee, topic, isWeak(observer));
    1.79 +  }
    1.80 +});
    1.81 +
    1.82 +// Unsubscribes `observer` from observer notifications for the
    1.83 +// given `topic`.
    1.84 +unsubscribe.define(Observer, (observer, topic) => {
    1.85 +  const delegee = subscribers.get(observer);
    1.86 +  if (delegee) {
    1.87 +    subscribers.delete(observer);
    1.88 +    removeObserver(delegee, topic);
    1.89 +  }
    1.90 +});