Base64.js

/*
* The MIT License (MIT)
*
* Copyright (c) 2018 Richard Backhouse
*
* Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
* DEALINGS IN THE SOFTWARE.
*/

const chars = 'ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=';

export default {
  btoa: (input:string = '')  => {
    let str = input;
    let output = '';

    for (let block = 0, charCode, i = 0, map = chars;
    str.charAt(i | 0) || (map = '=', i % 1);
    output += map.charAt(63 & block >> 8 - i % 1 * 8)) {

      charCode = str.charCodeAt(i += 3/4);

      if (charCode > 0xFF) {
        throw new Error("'btoa' failed: The string to be encoded contains characters outside of the Latin1 range.");
      }

      block = block << 8 | charCode;
    }

    return output;
  },

  atob: (input:string = '') => {
    let str = input.replace(/=+$/, '');
    let output = '';

    if (str.length % 4 == 1) {
      throw new Error("'atob' failed: The string to be decoded is not correctly encoded.");
    }
    for (let bc = 0, bs = 0, buffer, i = 0;
      buffer = str.charAt(i++);

      ~buffer && (bs = bc % 4 ? bs * 64 + buffer : buffer,
        bc++ % 4) ? output += String.fromCharCode(255 & bs >> (-2 * bc & 6)) : 0
    ) {
      buffer = chars.indexOf(buffer);
    }

    return output;
  }
}