code: function str2buf (str, enc) {
    if (!str || str.constructor !== String) return str
    if (!enc && isHex(str)) enc = 'hex'
    if (!enc && isBase64(str)) enc = 'base64'
    return Buffer.from(str, enc)
  }
docs: Convert a string to a Buffer.  If encoding is not specified, hex-encoding
  will be used if the input is valid hex.  If the input is valid base64 but
  not valid hex, base64 will be used.  Otherwise, utf8 will be used.
  @param {string} str String to be converted.
  @param {string=} enc Encoding of the input string (optional).
  @return {buffer} Buffer (bytearray) containing the input data.