base64.js

(function() {

  'use strict';

  var object = (
    // #34: CommonJS
    typeof exports === 'object' && exports != null &&
    typeof exports.nodeType !== 'number' ?
      exports :
    // #8: web workers
    typeof self !== 'undefined' ?
      self :
    // #31: ExtendScript
      $.global
  );

  var chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

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

  // encoder
  // [https://gist.github.com/999166] by [https://github.com/nignag]
  object.btoa || (
  object.btoa = function(input) {
    var str = String (input);
    for (
      // initialize result and counter
      var block, charCode, idx = 0, map = chars, output = '';
      // if the next str index does not exist:
      //   change the mapping table to "="
      //   check if d has no fractional digits
      str.charAt (idx | 0) || (map = '=', idx % 1);
      // "8 - idx % 1 * 8" generates the sequence 2, 4, 6, 8
      output += map.charAt (63 & block >> 8 - idx % 1 * 8)
    ) {
      charCode = str.charCodeAt (idx += 3 / 4);
      if (charCode > 0xFF) {
        throw new InvalidCharacterError ("'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.");
      }
      block = block << 8 | charCode;
    }
    return output;
  });

  // decoder
  // [https://gist.github.com/1020396] by [https://github.com/atk]
  object.atob || (
  object.atob = function(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;
  });

} ());