The Tor Browser / file revision

 /* 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 = ["Queue"];

 this.Queue = function Queue() {

   this._queue = [];

   this._index = 0;

 }

 Queue.prototype = {

   getLength: function() { return (this._queue.length - this._index); },

   isEmpty: function() { return (this._queue.length == 0); },

   enqueue: function(item) { this._queue.push(item); },

   dequeue: function() {

     if(this.isEmpty())

       return undefined;

     var item = this._queue[this._index];

     if (++this._index * 2 >= this._queue.length){

       this._queue  = this._queue.slice(this._index);

       this._index = 0;

     }

     return item;

   }

 }