*/
  private fun String.asciiToLowercase(): String =
    when {
      isAscii() -> lowercase(Locale.US) // This is an ASCII string.
      else -> this
    }

  /** Returns true if the [String] is ASCII encoded (0-127). */
  private fun String.isAscii() = length == utf8Size().toInt()

  /**
   * Returns true if [hostname] matches the domain name [pattern].
   *