#!/usr/bin/perl -w
# reverse_xxd.pl - Don Yang (uguu.org)
#
# This script is for people who don't have xxd installed, otherwise it
# does mostly the same thing as "xxd -r".
#
# Reads text data from stdin and writes binary data to stdout.
#
# 2013-06-05

use strict;

while( my $line = <> )
{
   next unless $line =~ /^\d+:([[:xdigit:] ]*)/;
   my $digits = $1;

   # Decode 2 bytes at a time
   my $output = "";
   while( $digits =~ s/^ ([[:xdigit:]]{2})([[:xdigit:]]{2})(.*)/$3/ )
   {
      $output .= chr(hex($1)) . chr(hex($2));
   }

   # Decode the last byte
   if( $digits =~ /^ ([[:xdigit:]]{2})/ )
   {
      $output .= chr(hex($1));
   }
   print $output;
}