90 lines
3.3 KiB
JavaScript
90 lines
3.3 KiB
JavaScript
/*****************************************************************************
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* Open MCT Web, Copyright (c) 2009-2015, United States Government
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* as represented by the Administrator of the National Aeronautics and Space
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* Administration. All rights reserved.
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*
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* Open MCT Web is licensed under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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* http://www.apache.org/licenses/LICENSE-2.0.
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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*
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* Open MCT Web includes source code licensed under additional open source
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* licenses. See the Open Source Licenses file (LICENSES.md) included with
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* this source code distribution or the Licensing information page available
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* at runtime from the About dialog for additional information.
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*****************************************************************************/
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/*global define*/
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define(
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['moment'],
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function (moment) {
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"use strict";
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/**
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* Calls functions every second, as close to the actual second
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* tick as is feasible.
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* @constructor
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* @param $timeout Angular's $timeout
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* @param {Function} now function to provide the current time in ms
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*/
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function TickerService($timeout, now) {
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var callbacks = [],
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last = now() - 1000;
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function tick() {
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var timestamp = now(),
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millis = timestamp % 1000;
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// Only update callbacks if a second has actually passed.
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if (timestamp >= last + 1000) {
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callbacks.forEach(function (callback) {
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callback(timestamp);
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});
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last = timestamp - millis;
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}
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// Try to update at exactly the next second
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$timeout(tick, 1000 - millis, true);
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}
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tick();
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return {
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/**
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* Listen for clock ticks. The provided callback will
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* be invoked with the current timestamp (in milliseconds
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* since Jan 1 1970) at regular intervals, as near to the
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* second boundary as possible.
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*
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* @method listen
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* @name TickerService#listen
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* @param {Function} callback callback to invoke
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* @returns {Function} a function to unregister this listener
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*/
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listen: function (callback) {
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callbacks.push(callback);
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// Provide immediate feedback
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callback(last);
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// Provide a deregistration function
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return function () {
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callbacks = callbacks.filter(function (cb) {
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return cb !== callback;
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});
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};
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}
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};
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}
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return TickerService;
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}
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);
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