converts CIDR to regexp

cidr2regex

#!/usr/bin/env perl

use Number::Range::Regex;
Number::Range::Regex->init({'comment'=>0, 'no_leading_zeroes'=>1, 'no_sign'=>1});


$rr0_255 = range(0, 255);
$rr0_32 = range(0, 32);

$union_range = range(-1, -1);


sub hn2dotdec
{
        return join '.', unpack 'C4', pack 'N', $_[0];
}
sub dotdec2hn
{
        return unpack 'N', pack 'C4', split /\./, $_[0];
}

sub range2regex
{
        my $min = shift;
        my $max = shift;

        my $ddmin = hn2dotdec $min;
        my $ddmax = hn2dotdec $max;
        my @ddmin = split /\./, $ddmin;
        my @ddmax = split /\./, $ddmax;
        my @octets;

        for my $octet (0..3)
        {
                if($ddmin[$octet] == $ddmax[$octet])
                {
                        push @octets, $ddmin[$octet];
                }
                elsif($ddmin[$octet] == 0 and $ddmax[$octet] == $octet_max)
                {
                        push @octets, '';
                        last;
                }
                else
                {
                        push @octets, range($ddmin[$octet], $ddmax[$octet])->regex;
                }
        }

        return '^' . join('\.', @octets) . ($octets[-1] eq '' ? '' : '$');
}


while(<>)
{
        s/[\r\n]+$//;
        my $cidr = $_;

        if($cidr !~ /^($rr0_255\.$rr0_255\.$rr0_255\.$rr0_255)\/($rr0_32)$/)
        {
                warn "not a cidr: $cidr\n";
                next;
        }

        my ($netip, $mask) = ($1, $2);
        my $af_length = 32;
        my $octet_max = 255;

        my $min = dotdec2hn($netip) & (0xFFFFFFFF << ($af_length - $mask));
        my $max = $min + 2**($af_length - $mask) - 1;
        #my $bmin = reverse pack('I', $min);
        #my $bmax = reverse pack('I', $max);

        $union_range = $union_range->union(range($min, $max));

        my $re = range2regex($min, $max);
        print $re, "\n";
}


print STDERR "Merged ranges:\n";
$ranges_str = substr $union_range, 3;
for my $range (split /,/, $ranges_str)
{
        my ($min, $max) = $range =~ /(\d+)\.\.(\d+)/;
        print range2regex($min, $max), "\n";
}