michael@0: /* This Source Code Form is subject to the terms of the Mozilla Public
michael@0:  * License, v. 2.0. If a copy of the MPL was not distributed with this
michael@0:  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
michael@0: 
michael@0: module.metadata = {
michael@0:   "stability": "experimental"
michael@0: };
michael@0: 
michael@0: "use strict";
michael@0: 
michael@0: const { Cu } = require("chrome");
michael@0: 
michael@0: function makeGetterFor(Type) {
michael@0:   let cache = new WeakMap();
michael@0: 
michael@0:   return function getFor(target) {
michael@0:     if (!cache.has(target))
michael@0:       cache.set(target, new Type());
michael@0: 
michael@0:     return cache.get(target);
michael@0:   }
michael@0: }
michael@0: 
michael@0: let getLookupFor = makeGetterFor(WeakMap);
michael@0: let getRefsFor = makeGetterFor(Set);
michael@0: 
michael@0: function add(target, value) {
michael@0:   if (has(target, value))
michael@0:     return;
michael@0: 
michael@0:   getLookupFor(target).set(value, true);
michael@0:   getRefsFor(target).add(Cu.getWeakReference(value));
michael@0: }
michael@0: exports.add = add;
michael@0: 
michael@0: function remove(target, value) {
michael@0:   getLookupFor(target).delete(value);
michael@0: }
michael@0: exports.remove = remove;
michael@0: 
michael@0: function has(target, value) {
michael@0:   return getLookupFor(target).has(value);
michael@0: }
michael@0: exports.has = has;
michael@0: 
michael@0: function clear(target) {
michael@0:   getLookupFor(target).clear();
michael@0:   getRefsFor(target).clear();
michael@0: }
michael@0: exports.clear = clear;
michael@0: 
michael@0: function iterator(target) {
michael@0:   let refs = getRefsFor(target);
michael@0: 
michael@0:   for (let ref of refs) {
michael@0:     let value = ref.get();
michael@0: 
michael@0:     // If `value` is already gc'ed, it would be `null`.
michael@0:     // The `has` function is using a WeakMap as lookup table, so passing `null`
michael@0:     // would raise an exception because WeakMap accepts as value only non-null
michael@0:     // object.
michael@0:     // Plus, if `value` is already gc'ed, we do not have to take it in account
michael@0:     // during the iteration, and remove it from the references.
michael@0:     if (value !== null && has(target, value))
michael@0:       yield value;
michael@0:     else
michael@0:       refs.delete(ref);
michael@0:   }
michael@0: }
michael@0: exports.iterator = iterator;