Re: Challenge Problem: Merging Network Addresses

[gbarr]

After some discussion with merlyn on IRC, I came up with the following.

use Socket;

my $str = "";

while(<>) {
  chomp;
  my ($ip,$bits) = m,^(\d+(?:\.\d+){3})/(\d+)$, or next;
  $str .= ";" . unpack("B*",inet_aton($ip));
  substr($str,-$bits) = "#" x $bits if $bits = 32 - $bits;
}
$str .= ";";
1 while $str =~ s/;([01]+)0(#*);\1.\2;/;${1}#${2};/g;

my @blocks = $str =~ /[10#]+/g;

foreach my $block (@blocks) {
  my $bits = 32 - ($block =~ tr/#/0/);
  print inet_ntoa(pack("B*", $block)),"/$bits\n";
}

Which actually, I think, shows some errors in 3 .out files on your site

--- nm3b.out    Thu Oct 11 21:54:06 2001
+++ nm3b.xx     Sat Oct 13 00:08:51 2001
@@ -1,4 +1,3 @@
-130.91.7.0/31
-130.91.7.2/31
+130.91.7.0/30
 255.255.255.254/31
 255.255.255.255/32
--- nm7.out     Thu Oct 11 21:54:07 2001
+++ nm7.xx      Sat Oct 13 00:09:10 2001
@@ -1,4 +1,3 @@
-1.2.3.0/28
-1.2.3.16/28
+1.2.3.0/27
 6.6.6.0/27
 6.6.7.0/26
--- nm8.out     Thu Oct 11 21:54:07 2001
+++ nm8.xx      Sat Oct 13 00:09:10 2001
@@ -1,5 +1,4 @@
-1.2.3.0/28
-1.2.3.16/28
-5.4.3.1/31
+1.2.3.0/27
+5.4.3.0/31
 6.6.6.0/27
 6.6.7.0/26

Update:

That code does not handle the following case

101.33.45.27/30
101.33.34.0/24

use Socket;

my @blocks;

while(<DATA>) {
  chomp;
  my ($ip,$bits) = m,^(\d+(?:\.\d+){3})/(\d+)$, or next;
  push @blocks, unpack("B*",inet_aton($ip));
  substr($blocks[-1],-$bits) = "#" x $bits
    if $bits = 32 - $bits;
}

my $str = ";" . join(";", sort @blocks) . ";";
1 while $str =~ s/;([01]+)(#*);\1[01#]*;/;${1}${2};/g;
1 while $str =~ s/;([01]+)0(#*);\1.\2;/;${1}#${2};/g;

my @blocks = $str =~ /[10#]+/g;

foreach my $block (@blocks) {
  my $bits = 32 - ($block =~ tr/#/0/);
  print inet_ntoa(pack("B*", $block)),"/$bits\n";
}