gecko-dev/toolkit/modules/DeferredTask.jsm

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JavaScript

/* 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/. */
this.EXPORTED_SYMBOLS = ["DeferredTask"];
const Cu = Components.utils;
const Cc = Components.classes;
const Ci = Components.interfaces;
/**
* A task that will run after a delay. Multiple attempts to run the same task
* before the delay will be coalesced
*
* Use this for instance if you write data to a file and you expect that you
* may have to rewrite data very soon afterwards. With |DeferredTask|, the
* task is delayed by a few milliseconds and, should a new change to the data
* occur during this period,
* 1/ only the final version of the data is actually written;
* 2/ a further grace delay is added to take into account other changes.
*
* Constructor
* @param aDelay The delay time in milliseconds.
* @param aCallback The code to execute after the delay.
*/
this.DeferredTask = function DeferredTask(aCallback, aDelay) {
this._callback = function onCallback() {
this._timer = null;
try {
aCallback();
} catch(e) {
Cu.reportError(e);
}
}.bind(this);
this._delay = aDelay;
}
DeferredTask.prototype = {
/* Callback */
_callback: null,
/* Delay */
_delay: null,
/* Timer */
_timer: null,
/**
* Check the current task state.
* @returns true if pending, false otherwise.
*/
get isPending() {
return (this._timer != null);
},
/**
* Start (or postpone) task.
*/
start: function DeferredTask_start() {
if (this._timer) {
this._timer.cancel();
}
this._timer = Cc["@mozilla.org/timer;1"].createInstance(Ci.nsITimer);
this._timer.initWithCallback(
this._callback, this._delay, Ci.nsITimer.TYPE_ONE_SHOT);
},
/**
* Perform any postponed task immediately.
*/
flush: function DeferredTask_flush() {
if (this._timer) {
this.cancel();
this._callback();
}
},
/**
* Cancel any pending task.
*/
cancel: function DeferredTask_cancel() {
if (this._timer) {
this._timer.cancel();
this._timer = null;
}
}
};