#!/usr/bin/perl

my $sum1 = 0;     # That I declare my variables at the top of the script
my $sum2 = 0;     # demonstrates that I spend more time writing C code.
my $tracknum = 1; # these days.
my %discinfo;

if ($ARGV[0])
{
	# If an alternate file is specified on the command line, use it.
	open(DISCINFO, $ARGV[0]) or die "error opening $ARGV[0]: $!";
}
else
{
	# Otherwise, use the default file location.
	open(DISCINFO, "/CDROM/info.disc") or die "error opening /CDROM/info.disc: $!";
}

while (<DISCINFO>) # Damn I love parsing text files in Perl.
{
	# Amazing how three lines of Perl can turn these files into an easily
	# accessed set of variables, isn't it?
	($key, $value) = split(/: /, $_);
	chomp($value);
	$discinfo{$key} = $value;
}

close(DISCINFO);

# This section generates the checksum (though I'm not sure it can really be called
# a checksum) that is the first element of the ID string.  I don't know why they
# do it this way, I suppose they figure this is the best way.  But, whatever works.
while ($tracknum <= $discinfo{"album.tracks"})
{
	$sum1 += &calculate_sum(&to_seconds($discinfo{"track$tracknum.start"}));
	++$tracknum;
}

$sum2 = &to_seconds($discinfo{"album.duration"}) - &to_seconds($discinfo{"track1.start"});
printf("%08x ", $sum1 % 255 << 24 | $sum2 << 8 | $discinfo{"album.tracks"});

# Next comes the number of tracks on the CD.
print $discinfo{"album.tracks"}, " ";

# Reset this variable back to 1 so I can re-use it.  Hey, I believe in recycling.
$tracknum = 1;

while ($tracknum <= $discinfo{"album.tracks"})
{
	# This converts each track offset to frames and then prints it out.
	print &to_frames($discinfo{"track$tracknum.start"}), " ";
	++$tracknum;
}

# Last element of the ID string, the album duration in seconds.  For some reason 
# the info.disc files always list the albums as 2 seconds longer than the discid.c
# source did, so I just subtract 2 from this to make them conform to what CDDB wants.
print (&to_seconds($discinfo{"album.duration"}) - 2);
print "\n";
exit(0);

# Subroutine to generate the checksums for the first ID element.
sub calculate_sum
{
	my $seconds = shift(@_);
	my $retval = 0;

	while ($seconds > 0)
	{
		$retval += $seconds % 10;
		$seconds /= 10;
	}
	return($retval);
}

# Subroutine to convert the minutes:seconds:frames strings to just frames.
sub to_frames
{
	my $dirty = shift @_;
	my $minutes = 0;
	my $seconds = 0;
	my $frames = 0;
	
	($minutes, $seconds, $frames) = split(/:/, $dirty);
	$frames += (($minutes * 60) + $seconds) * 75;
	return($frames);
}

# Subroutine to convert the minutes:seconds:frames strings to just seconds.
# Note that the extra frames are truncated by this; it's supposed to be
# like that in order to return values like what CDDB wants.
sub to_seconds
{
	my $dirty = shift @_;
	my $minutes = 0;
	my $seconds = 0;
	
	($minutes, $seconds) = split(/:/, $dirty);
	$seconds += $minutes * 60;
	return($seconds);
}