#!perl

use warnings; use strict; use CGI;

1 == @ARGV || 2 == @ARGV or die "usage: perl bolddiff.pl file1 file2";
my $two = 2 <= @ARGV;
my ($f0n, $f1n) = @ARGV;
my $key = "BOLDDIFF_" . join("", map { int(rand(10)) } 0..5);
my $H;
if ($two) {
	open $H, "-|", "diff", "-bD", $key, "--", $f1n, $f0n or die;
} else {
	open $H, "<", $f0n or die;
}

print qq{<pre class="clisting">\n};
my $tap = 1; my $diff = 0;
while (<$H>) {
	if (/\b\Q$key\E\b/) {
		if (/\A#ifdef \Q$key\E\b/) {
			$tap = 0; $diff = 1;
		} elsif (/\A#ifndef \Q$key\E\b/) {
			$tap = 1; $diff = 1;
		} elsif (/\A#else \/\* \Q$key\E\b/) {
			$tap = !$tap;
		} elsif (/\A#endif \/\* (! )?\Q$key\E\b/) {
			$tap = 1; $diff = 0;
		} else {
			die "ifdef key unexpected: $_";
		}
	} else {
		if ($tap) {
			s/&/&amp;/g; s/</&lt;/g; s/>/&gt;/g;
			$diff and s/(.*)/<strong>$1<\/strong>/;
			print;
		}
	}
}
print qq{</pre>\n};

__END__