source: genesis/dns/zone2rev.pl@ 4028

#!/usr/bin/perl
#
open STDIN,shift @ARGV
        or die "Cannot open $_:$!" 
                if @ARGV;

$domain = '.';

while(<STDIN>) {

        if (m/\$ORIGIN\s+([\w\-\.]+)/) {
                $domain = lc $1;
                next;
        };
        next 
                unless m/^\s*([\w\-\.]+)\s+(IN\s+)?A\s+([\d\.]+)/i;

        my ($host,$ip) = (lc $1,lc $3);

        $host .= '.'.$domain 
                unless $host =~ m/\.$/;

        warn "A-Resource defined in two places\n\tfor $ip/$host at line $. and $line{$ip}\n"
                if defined $host{$ip} and $host{$ip} eq $host;

        warn "A-Resource Conflict - there should be just one.\n\t$ip used for $host and $host{$ip} at line $. and $line{$ip}\n"
                if defined $host{$ip};

        warn "Resource defined in two places\n\t$host at $ip{$host} at line $. and $line{$host}.\n"
                if defined $ip{$host} and $ip eq $ip{$host};

        warn "Resource conflict - there should be just one.\n\t$host at $ip{$host} and $ip at line $. and $line{$host}\n"
                if defined $ip{$host};

        $host{$ip} = $host;
        $ip{$host} = $ip;
        $line{$ip} = $line{$host} = $.;

        print "$ip\t$host\n";
};