#!/web/usr/perl/bin/perl

use Getopt::Long;

GetOptions("i|image=s" => \$image, "q|quiet" => \$quiet);
if(!$image) {
	print STDERR "Usage: $0 -i /path/to/image.jpg";
	exit 2;
}

open(JPEG, "$image") or die "Unable to open $image: $!\n";
binmode(JPEG);
read(JPEG, $s, 2);
if($s eq "\xFF\xD8") {
	while(1) {
		my($ff, $mark) = unpack("CC", jpeg_groper(2));
		last if($ff != 0xFF);
		next if(($mark == 0xDA) || ($mark == 0xD9));
		my $len = unpack("n", jpeg_groper(2));
		last if($len < 0);
		$len -= 2;
		if($len < 0) {
			qprint("CORRUPT JPEG: Bad Field Length");
			exit 1;
		}
		jpeg_groper($len) if($len);
	}
} else {
	qprint("CORRUPT JPEG: Invalid Magic Number");
	exit 1;
}
close(JPEG);
qprint("JPEG OK");
exit 0;

sub jpeg_groper {
	my $b;
	my $n = read(JPEG, $b, @_[0]);
	if(!defined $n) {
		qprint("CORRUPT JPEG: Read Failed");
		return -1;
	} elsif ($n != @_[0]) {
		qprint("CORRUPT JPEG: Short Read (@_[0] of $n)");
		return -1;
	}
	return $b;
}

sub qprint {
	print @_[0] . "\n" if(!$quiet);
}