#!/usr/bin/perl
# xor2.pl - Don Yang (uguu.org)
#
# Encode source by decomposing each character into XOR pairs.
#
# 12/23/07

use strict;

my $code = q{

$l = 23 - 2 * ($a = sin(($c = (time() % 100) / 50) * atan2(0, -1)));
$p = 10.5 + $a;
$q = 6.5 - $a;

if( $c < 1 )
{
   $s = 56 - 33 * $c;
   $x = 2 * $c - 1;
   $t = 11 + $x * $x * 7;
}
else
{
   $s = 23 + 33 * ($c - 1);
   $t = 18;
}

for($y = 0; $y < 24; $y++)
{
   $v = ($y - $t) / ($y < $t ? $p : $q);
   for($x = 0; $x < 79; $x++)
   {
      $u = ($x - $s) / $l;

      $c = $x - int($s);
      $z .=
         chr
         (
            $y == int($t + $q) && abs($x - $s) < 10
            ?  33
            :  (
                  $u * $u + $v * $v > 1 ||
                  ($y > $t - 5 - 2 * $a && $y <= $t - 2 - 2 * $a &&
                   !($c + 6 && $c && $c + 5 && $c - 1))
                  ? 32 : 33
               )
         );
   }
   $z .= "\n";
}

$c = ($z =~ y/!/x/);
$n = '$n=q{' . $n . '#'x($c - length($n) - 26) . '};$n=~s/\s//g;eval$n;';
$y = 0;
foreach $x ($z =~ /./gs)
{
   print 'x' eq $x ? substr($n, $y++, 1) : $x;
}

};

$code =~ s/\s//g;
print "code =\n$code\n";

# Generate dictionary
my %dict;
for(my $i = 33; $i < 127; $i++)
{
   next if chr($i) !~ /[`:;#%&\[\]]/;
   for(my $j = 33; $j < 127; $j++)
   {
      next if chr($j) =~ /['[:alpha:]]/;
      push @{$dict{$i ^ $j}}, chr($i) . chr($j);
   }
}
print "dict =\n";
for(my $i = 33; $i < 127; $i++)
{
   next unless exists $dict{$i};
   print "$i =";
   print " $_" foreach @{$dict{$i}};
   print "\n";
}

# Encode source code pairs
my $p = '';
my $q = '';
my $d = 0;
foreach my $c (unpack 'C*', $code)
{
   # See if we can encode this character using "dango" or "DANGO"
   my $p0 = substr("Dango", $d, 1);
   my $q0 = chr($c) ^ $p0;
   if( ord($q0) > 32 && ord($q0) < 127 && $q0 ne "'" )
   {
      $d = ($d + 1) % 5;
      $p .= $p0;
      $q .= $q0;
      next;
   }
   $p0 = substr("dANGO", $d, 1);
   $q0 = chr($c) ^ $p0;
   if( ord($q0) > 32 && ord($q0) < 127 && $q0 ne "'" )
   {
      $d = ($d + 1) % 5;
      $p .= $p0;
      $q .= $q0;
      next;
   }

   # Select random character pair from dictionary
   die unless exists $dict{$c};
   my $index = int(rand ($#{$dict{$c}} + 1));
   my $pair = ${$dict{$c}}[$index];
   $p .= substr($pair, 0, 1);
   $q .= substr($pair, 1, 1);
}
print "p =\n$p\nq =\n$q\n";