IPAddr#_reverse

# File tmp/rubies/ruby-3.1.3/lib/ipaddr.rb, line 708
def _reverse
  case @family
  when Socket::AF_INET
    return (0..3).map { |i|
      (@addr >> (8 * i)) & 0xff
    }.join('.')
  when Socket::AF_INET6
    return ("%.32x" % @addr).reverse!.gsub!(/.(?!$)/, '\&.')
  else
    raise AddressFamilyError, "unsupported address family"
  end
end