IPAddr#_to_string

# File tmp/rubies/ruby-3.0.5/lib/ipaddr.rb, line 688
def _to_string(addr)
  case @family
  when Socket::AF_INET
    return (0..3).map { |i|
      (addr >> (24 - 8 * i)) & 0xff
    }.join('.')
  when Socket::AF_INET6
    return (("%.32x" % addr).gsub!(/.{4}(?!$)/, '\&:'))
  else
    raise AddressFamilyError, "unsupported address family"
  end
end