Data commit

Task/Canonicalize-CIDR/Perl/canonicalize-cidr.pl

@@ -0,0 +1,26 @@
+#!/usr/bin/env perl
+use v5.16;
+use Socket qw(inet_aton inet_ntoa);
+
+# canonicalize a CIDR block: make sure none of the host bits are set
+if (!@ARGV) {
+   chomp(@ARGV = <>);
+}
+
+for (@ARGV) {
+
+  # dotted-decimal / bits in network part
+  my ($dotted, $size) = split m#/#;
+
+  # get IP as binary string
+  my $binary = sprintf "%032b", unpack('N', inet_aton $dotted);
+
+  # Replace the host part with all zeroes
+  substr($binary, $size) = 0 x (32 - $size);
+
+  # Convert back to dotted-decimal
+  $dotted = inet_ntoa(pack 'B32', $binary);
+
+  # And output
+  say "$dotted/$size";
+}