forked from mirrors/gecko-dev
71 lines
2.3 KiB
JavaScript
71 lines
2.3 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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export var PromiseUtils = {
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/*
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* Creates a new pending Promise and provide methods to resolve and reject this Promise.
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*
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* @return {Deferred} an object consisting of a pending Promise "promise"
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* and methods "resolve" and "reject" to change its state.
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*/
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defer() {
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return new Deferred();
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},
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/**
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* Requests idle dispatch to the main thread for the given callback,
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* and returns a promise which resolves to the callback's return value
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* when it has been executed.
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*
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* @param {function} callback
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* @param {integer} [timeout]
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* An optional timeout, after which the callback will be
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* executed immediately if idle dispatch has not yet occurred.
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*
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* @returns {Promise}
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*/
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idleDispatch(callback, timeout = 0) {
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return new Promise((resolve, reject) => {
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Services.tm.idleDispatchToMainThread(() => {
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try {
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resolve(callback());
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} catch (e) {
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reject(e);
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}
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}, timeout);
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});
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},
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};
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/**
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* The definition of Deferred object which is returned by PromiseUtils.defer(),
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* It contains a Promise and methods to resolve/reject it.
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*/
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function Deferred() {
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/* A method to resolve the associated Promise with the value passed.
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* If the promise is already settled it does nothing.
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*
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* @param {anything} value : This value is used to resolve the promise
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* If the value is a Promise then the associated promise assumes the state
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* of Promise passed as value.
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*/
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this.resolve = null;
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/* A method to reject the assocaited Promise with the value passed.
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* If the promise is already settled it does nothing.
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*
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* @param {anything} reason: The reason for the rejection of the Promise.
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* Generally its an Error object. If however a Promise is passed, then the Promise
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* itself will be the reason for rejection no matter the state of the Promise.
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*/
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this.reject = null;
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/* A newly created Pomise object.
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* Initially in pending state.
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*/
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this.promise = new Promise((resolve, reject) => {
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this.resolve = resolve;
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this.reject = reject;
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});
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}
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