cashaddrjs-slp/src/base32.js

SLP & Bitcoin Cash cashaddr address format support for Node.js and web browsers.

/**
 * @license
 * https://github.com/bitcoincashjs/cashaddr
 * Copyright (c) 2017-2018 Emilio Almansi
 * Distributed under the MIT software license, see the accompanying
 * file LICENSE or http://www.opensource.org/licenses/mit-license.php.
 */

'use strict';

var validate = require('./validation').validate;

/**
 * Base32 encoding and decoding.
 *
 * @module base32
 */

/**
 * Charset containing the 32 symbols used in the base32 encoding.
 * @private
 */
var CHARSET = 'qpzry9x8gf2tvdw0s3jn54khce6mua7l';

/**
 * Inverted index mapping each symbol into its index within the charset.
 * @private
 */
var CHARSET_INVERSE_INDEX = {
  'q': 0, 'p': 1, 'z': 2, 'r': 3, 'y': 4, '9': 5, 'x': 6, '8': 7,
  'g': 8, 'f': 9, '2': 10, 't': 11, 'v': 12, 'd': 13, 'w': 14, '0': 15,
  's': 16, '3': 17, 'j': 18, 'n': 19, '5': 20, '4': 21, 'k': 22, 'h': 23,
  'c': 24, 'e': 25, '6': 26, 'm': 27, 'u': 28, 'a': 29, '7': 30, 'l': 31,
};

/**
 * Encodes the given array of 5-bit integers as a base32-encoded string.
 *
 * @static
 * @param {Uint8Array} data Array of integers between 0 and 31 inclusive.
 * @returns {string}
 * @throws {ValidationError}
 */
function encode(data) {
  validate(data instanceof Uint8Array, 'Invalid data: ' + data + '.');
  var base32 = '';
  for (var i = 0; i < data.length; ++i) {
    var value = data[i];
    validate(0 <= value && value < 32, 'Invalid value: ' + value + '.');
    base32 += CHARSET[value];
  }
  return base32;
}

/**
 * Decodes the given base32-encoded string into an array of 5-bit integers.
 *
 * @static
 * @param {string} string
 * @returns {Uint8Array}
 * @throws {ValidationError}
 */
function decode(string) {
  validate(typeof string === 'string', 'Invalid base32-encoded string: ' + string + '.');
  var data = new Uint8Array(string.length);
  for (var i = 0; i < string.length; ++i) {
    var value = string[i];
    validate(value in CHARSET_INVERSE_INDEX, 'Invalid value: ' + value + '.');
    data[i] = CHARSET_INVERSE_INDEX[value];
  }
  return data;
}

module.exports = {
  encode: encode,
  decode: decode,
};