base64.js

(function(f) {

  'use strict';

  /* istanbul ignore else */
  if (typeof exports === 'object' && exports != null &&
      typeof exports.nodeType !== 'number') {
    module.exports = f ();
  } else if (typeof define === 'function' && define.amd != null) {
    define ([], f);
  } else {
    var base64 = f ();
    var global = typeof self !== 'undefined' ? self : $.global;
    if (typeof global.btoa !== 'function') global.btoa = base64.btoa;
    if (typeof global.atob !== 'function') global.atob = base64.atob;
  }

} (function() {

  'use strict';

  var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

  function InvalidCharacterError(message) {
    this.message = message;
  }
  InvalidCharacterError.prototype = new Error ();
  InvalidCharacterError.prototype.name = 'InvalidCharacterError';

  // encoder
  function btoa(input) {
    var data = String (input), o1, o2, o3, bits, i = 0, acc = '';

    while (i < data.length) {
      // pack three octets into four hextets
      o1 = data.charCodeAt (i++);
      o2 = data.charCodeAt (i++);
      o3 = data.charCodeAt (i++);

      if (o1 > 255 || o2 > 255 || o3 > 255) {
        throw new InvalidCharacterError ("'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.");
      }

      bits = (o1 << 16) | (o2 << 8) | o3;
      // use hextets to index into b64, and append result to encoded string
      acc += chars.charAt ((bits >> 18) & 0x3F) +
             chars.charAt ((bits >> 12) & 0x3F) +
             chars.charAt ((bits >>  6) & 0x3F) +
             chars.charAt ((bits)       & 0x3F);
    }

    switch (data.length % 3) {
      case 0: return acc;
      case 1: return acc.slice (0, -2) + '==';
      case 2: return acc.slice (0, -1) + '=';
    }
  }

  // decoder
  // [https://gist.github.com/1020396] by [https://github.com/atk]
  function atob(input) {
    var str = (String (input)).replace (/[=]+$/, ''); // #31: ExtendScript bad parse of /=
    if (str.length % 4 === 1) {
      throw new InvalidCharacterError ("'atob' failed: The string to be decoded is not correctly encoded.");
    }
    for (
      // initialize result and counters
      var bc = 0, bs, buffer, idx = 0, output = '';
      // get next character
      buffer = str.charAt (idx++); // eslint-disable-line no-cond-assign
      // character found in table? initialize bit storage and add its ascii value;
      ~buffer && (bs = bc % 4 ? bs * 64 + buffer : buffer,
        // and if not first of each 4 characters,
        // convert the first 8 bits to one ascii character
        bc++ % 4) ? output += String.fromCharCode (255 & bs >> (-2 * bc & 6)) : 0
    ) {
      // try to find character in table (0-63, not found => -1)
      buffer = chars.indexOf (buffer);
    }
    return output;
  }

  return {btoa: btoa, atob: atob};

}));