#!/usr/bin/perl
#
# Creates a blank MS-DOS formatted hard disk image
#

use Fcntl;

%opt = ();
@args = ();

for $a ( @ARGV ) {
    if ( $a =~ /^\-/ ) {
	$opt{$'} = 1;
    } else {
	push(@args, $a);
    }
}

($file,$c,$h,$s) = @args;
$c += 0;  $h += 0;  $s += 0;

if ( !$file || $c < 1 || $c > 1024 ||
     $h < 1 || $h > 256 || $s < 1 || $s > 63 ) {
    print STDERR "Usage: $0 [-o] file c h s (max: 1024 256 63)\n";
    print STDERR "    -o    print filesystem offset to stdout\n";
    exit 1;
}

$cylsize = $h*$s*512;

sysopen(OUTPUT, $file, O_CREAT|O_RDWR|O_TRUNC, 0666)
    or die "$0: Cannot open: $file\n";

# Print the MBR and partition table
$mbr = '';
while ( $line = <DATA> ) {
    chomp $line;
    foreach $byte ( split(/\s+/, $line) ) {
	$mbr .= chr(hex($byte));
    }
}
if ( length($mbr) > 446 ) {
    die "$0: Bad MBR code\n";
}

$mbr .= "\0" x (446 - length($mbr));

print OUTPUT $mbr;

# Print partition table
$psize = $c*$h*$s-$s;
$bhead   = ($h > 1) ? 1 : 0;
$bsect   = 1;
$bcyl    = ($h > 1) ? 0 : 1;
$ehead   = $h;
$esect   = $s + (($c & 0x300) >> 2);
$ecyl    = $c & 0xff;
if ( $psize > 65536 ) {
    $fstype = 0x06;
} else {
    $fstype = 0x04;
}
print OUTPUT pack("CCCCCCCCVV", 0x80, $bhead, $bsect, $bcyl, $fstype,
		  $ehead, $esect, $ecyl, $s, $psize);
print OUTPUT "\0" x 48;
print OUTPUT "\x55\xaa";

# Output blank file
$totalsize = $c*$h*$s;
$tracks    = $c*$h;

$track = "\0" x (512*$s);

# Print fractional track
print OUTPUT "\0" x (512 * ($s-1));

for ( $i = 1 ; $i < $tracks ; $i++ ) {
    print OUTPUT $track;
}

# Print mtools temp file
$tmpfile = "/tmp/mconfig.$$";
$offset = $s*512;
open(MCONFIG, "> ${tmpfile}") or die "$0: Cannot make mtools config\n";
print MCONFIG "drive z:\n";
print MCONFIG "file=\"\Q${file}\E\"\n";
print MCONFIG "cylinders=${c}\n";
print MCONFIG "heads=${h}\n";
print MCONFIG "sectors=${s}\n";
print MCONFIG "offset=${offset}\n";
close(MCONFIG);

# Output the filesystem offset to stdout if appropriate
if ( $opt{'o'} ) {
    print $offset, "\n";
}

$ENV{'MTOOLSRC'} = $tmpfile;
system('mformat', 'z:');

unlink($tmpfile);

seek(OUTPUT, $s*512+0x36, 0);
read(OUTPUT, $fsname, 8);

# FAT12: adjust partition type
if ( $fsname eq 'FAT12   ' ) {
    $fstype = 0x01;
}
seek(OUTPUT, 446+4, 0);
print OUTPUT pack("C", $fstype);

exit 0;
__END__