Galois Field Reciprocal in PERL

gf_math.pl

#!/usr/bin/perl
$modulo = 0x1f9;
$order  = msb($modulo);
sub gf_add {
	return $_[0] ^ $_[1];
}
sub msb {
	if ($_[0] == 0) { return -1;}
	my $i = 0; $_ = $_[0];
	while ($_ != 1) {
		$i++;
		$_ = $_ >> 1;
	}
	return $i;
}
sub poly_div_mod {
	my $current_number = $_[0]; my $modulo = $_[1];
	my $current_order = msb($current_number);
	my $order         = msb($modulo);
	my $quotient      = 0;
	while ($current_order >= $order) {
		$quotient        = $quotient ^ (1 << ($current_order - $order));
		$current_number  = $current_number  ^ ($modulo << ($current_order - $order));
		$current_order   = msb($current_number );
	}
	return ($quotient,$current_number);
}
sub poly_multiply {
	my $a = $_[0]; my $b = $_[1];
	my $result;
	while ($b > 0) {
		if ($b & 1) {
			$result = $result ^ $a;
		}
		$b = $b >> 1;
		$a = $a << 1;
	}
	return $result;
}
sub gf_multiply {
	my $q;
	($_,$q) = poly_div_mod(poly_multiply($_[0],$_[1]),$modulo);
	return $q;
}
sub gf_invert {
	my $a     = $modulo;
	my $b     = $_[0];
	if ($b == 0) {return -1;}
	my $aux_2 = 0;
	my $aux_1 = 1;
	my $aux_0;
	my $remainder; my $quotient;
	while ($b != 1) {
		($quotient,$remainder) = poly_div_mod($a,$b);
		$aux_0 = gf_multiply($aux_1,$quotient) ^ $aux_2;
		$a = $b; $b = $remainder;
		$aux_2 = $aux_1; $aux_1 = $aux_0; 
	}
	return $aux_0;
}
for (my $i = 2; $i < 256; $i++) {
	printf ("0x%02x\n", gf_multiply($i,gf_invert ($i)));
}
my @primes = (2,3);
outer_loop: for (my $i=4;$i<512;$i++) { 
#Incidentally this is much faster than the HAskell version I did
	inner_loop: foreach my $prime (@primes) {

		my $q; my $r;
		($q,$r) = poly_div_mod($i,$prime);
		if ($r == 0) {next outer_loop;}
	}
	push @primes, $i;
	printf ("0x%04x\n", $i);
}