#!/usr/bin/perl
# isohybrid-embeddedfat - written by Andreas Loibl <andreas@andreas-loibl.de>
# 

die "Usage: $0 <isohybrid-bg2.iso> <filename>\n" if $#ARGV != 1;

($file,$filename) = @ARGV;
open(FILE, "+< $file\0") or die "$0: cannot open $file: $!\n";
binmode FILE;

# Get the total size of the image
(@imgstat = stat(FILE)) or die "$0: $file: $!\n";
$imgsize = $imgstat[7];
if (!$imgsize) {
    die "$0: $file: cannot determine length of file\n";
}

$start = `isoinfo -J -s -l -i kanotix64.iso | awk '/$filename/{print \$10}'`;
if (!$start) {
    die "$0: $filename: cannot determine position of file\n";
}

use integer;
$lba = $start*4;
$psize = $imgsize/512 - $lba;
$h = 64; $s = 32;
$hpc = 32; $spt = 63;
$bcyl = $lba / ($spt * $hpc);
$bhead = ($lba / $spt) % $hpc;
$bsect = ($lba % $spt) + 1;
$cylsize = $h*$s*512;
$c = $imgsize/$cylsize;
if ($c > 1024) {
    $cc = 1024;
} else {
    $cc = $c;
}
$ehead   = $h-1;
$esect   = $s + ((($cc-1) & 0x300) >> 2);
$ecyl    = ($cc-1) & 0xff;

# Adjust MBR partition table
$fstype  = 0xEF;
$pentry  = 1;

seek(FILE, 430+16*$pentry, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack("CCCCCCCCVV", 0x80, $bhead, $bsect, $bcyl, $fstype, $ehead, $esect, $ecyl, $lba, $psize);

# Delete other partition entry from MBR-partition-table
seek(FILE, 430+16*2, SEEK_SET) or die "$0: $file: $!\n";
print FILE "\0" x 16;

# Done...
close(PART);
close(FILE);

exit 0;