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/. */

 "use strict";

 module.metadata = {

   "stability": "unstable"

 };

 const { Cu } = require("chrome");

 // Passing an empty object as second argument to avoid scope's pollution

 const { atob, btoa } = Cu.import("resource://gre/modules/Services.jsm", {});

 function isUTF8(charset) {

   let type = typeof charset;

   if (type === "undefined")

     return false;

   if (type === "string" && charset.toLowerCase() === "utf-8")

     return true;

   throw new Error("The charset argument can be only 'utf-8'");

 }

 exports.decode = function (data, charset) {

   if (isUTF8(charset))

 		return decodeURIComponent(escape(atob(data)))

 	return atob(data);

 }

 exports.encode = function (data, charset) {

   if (isUTF8(charset))

     return btoa(unescape(encodeURIComponent(data)))

 	return btoa(data);

 }