code: function polymod(pre) {
    const b = pre >>> 25;
    return ((pre & 0x1ffffff) << 5)
      ^ (-((b >> 0) & 1) & 0x3b6a57b2)
      ^ (-((b >> 1) & 1) & 0x26508e6d)
      ^ (-((b >> 2) & 1) & 0x1ea119fa)
      ^ (-((b >> 3) & 1) & 0x3d4233dd)
      ^ (-((b >> 4) & 1) & 0x2a1462b3);
  }
docs: Update checksum.
  @ignore
  @param {Number} chk
  @returns {Number}