#!/usr/bin/perl -w

# Copyright (c) 2004, James O'Gorman
# All rights reserved.
# 
# Redistribution and use in source and binary forms, with or without
# modification, are permitted provided that the following conditions 
# are met:
# 
# 1. Redistributions of source code must retain the above copyright
#    notice, this list of conditions and the following disclaimer.
# 2. Redistributions in binary form must reproduce the above copyright
#    notice, this list of conditions and the following disclaimer in the
#    documentation and/or other materials provided with the distribution.
# 
# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS "AS IS" AND ANY
# EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
# DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE FOR ANY
# DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
# (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
# SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
# CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
# SUCH DAMAGE.

use strict;

if (!defined($ARGV[0])) {
  @ARGV = split(/\s+/, <STDIN>);
}

foreach my $ip (@ARGV) {
  if ($ip =~ /^(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.(25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/) {
    #print "$ip is IPv4\n";
    &arpa($ip, 4);
  }
  elsif ($ip =~ /^([a-zA-Z0-9]{0,4}[:]{1,2})+([a-zA-Z0-9]{0,4})?$/) {
    #print "$ip is IPv6\n";
    &arpa($ip, 6);
  }
  else {
    print "Error in ${ip}\n";
    print "Either IPv4 ('.' notation) or IPv6 (':' notation) must be used\n";
    exit 1;
  } #endif
} #endfor
  
sub arpa($;$) {
  my ($ip, $ver) = @_;
  my $host;
  if ($ver == 6) {
    my @addr = split(/:/, $ip);
    my $pad;
    if ($#addr < 8) {
      $pad = 4 * (8 - $#addr);
    }
    foreach (my $i = $#addr; $i >= 0; $i--) {
      if (length($addr[$i]) == 0) {
        for (my $p = 0; $p < $pad; $p++) {
          $addr[$i] .= "0";
        }
      }
      else {
        while (length($addr[$i]) < 4) {
          $addr[$i] = 0 . $addr[$i];
        }
      }
      $addr[$i] = "$addr[$i]"; # Convert the number to a string
      if (length($addr[$i])-1 == 0) {
      }
      for (my $x = length($addr[$i])-1; $x >= 0; $x--) {
        $a = substr($addr[$i], $x, 1);
        $host .= $a . ".";
      }
    }
    my $domain = $addr[0] eq '3ffe' ? "int" : "arpa";
    $host .= "ip6.$domain.";
  }
  elsif ($ver == 4) {
    my @addr = split(/\./, $ip);
    for (my $i = $#addr; $i >= 0; $i--) {
      $host .= $addr[$i].".";
    }
    $host .= "in-addr.arpa.";
  }
  print "$host\n";
}