From fe64bf8a39d11f1768fd2bf380c42cfee1edee37 Mon Sep 17 00:00:00 2001
From: Mikael Nordin <kano0049@su.se>
Date: Wed, 23 Mar 2016 10:24:18 +0100
Subject: [PATCH] Initial commit

---
 ipv6expand.pl | 89 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 89 insertions(+)
 create mode 100755 ipv6expand.pl

diff --git a/ipv6expand.pl b/ipv6expand.pl
new file mode 100755
index 0000000..16af512
--- /dev/null
+++ b/ipv6expand.pl
@@ -0,0 +1,89 @@
+#!/usr/bin/env perl
+
+use strict;
+use warnings;
+
+sub count_groups { # See hown many groups we have
+	die "Too many arguments for subroutine" if @_ < 1;
+	die "Too few arguments for subroutine" if @_ > 1;
+	my $address = shift;
+	
+	# Make sure we have just enough double colons and count them if it is all right
+	my $colon_no =  () = $address =~ /::/g;
+	die "Invalid ipv6 address" if $colon_no > 1;
+	my $no =  1;
+	$no += () = $address =~ /:/g;
+	return $no;
+
+}
+
+# If we have one occurence of :: replace with correct amount of zeros and colons
+sub expand_void {
+	die "Too many arguments for subroutine" if @_ < 1;
+	die "Too few arguments for subroutine" if @_ > 1;
+	my $address = shift;
+	my $no_colons = 8 - count_groups($address);
+	my $insert = "0000:0000";
+	for (my $i = 0; $i < $no_colons - 1; $i++) {
+		$insert = $insert . ":0000"
+	}
+	$address =~ s/::/:$insert:/g;
+	return $address;
+
+}
+
+# Fix a single group and padd with zeros
+sub fix_group {
+	die "Too many arguments for subroutine" if @_ < 1;
+	die "Too few arguments for subroutine" if @_ > 1;
+	my $group = shift;
+	my $len = length($group);
+	die "Group has too many digits" if $len > 4;
+	while ($len < 4) {
+		$group = "0$group";
+		$len++;		
+
+	}
+	# Make sure it is a valid hexnumber
+	die "Group is not a hex number" if $group !~ /^[0-9a-fA-F]+$/;
+	return $group;
+	
+}
+
+# Loop all groups and fix them with fix_group
+sub fix_groups {
+	die "Too many arguments for subroutine" if @_ < 1;
+	die "Too few arguments for subroutine" if @_ > 1;
+	my $a = shift;
+	my @groups = split(/:/, $a);
+	my $address = "";
+	foreach my $group (@groups) {
+		$group = fix_group($group);
+		$address = "$address$group:";
+	}
+	
+	$address =~ s/:+$//; 
+	return $address;
+}
+
+# Now put it together
+# Loop through stdin
+while (<>) {
+	chomp; # Remove newline
+	my $addr = $_; # Store address
+
+	if (count_groups($addr) != 8) {
+		$addr = expand_void($addr);
+	}
+	
+	$addr = fix_groups($addr);
+
+	# Double check that we have enough groups one last time
+	die "Not a valid ipv6 address" if count_groups($addr) != 8;
+
+	# Lower case is preffered for ipv6 adresses
+	print lc "$addr\n";
+	
+}
+
+exit 0;