#!/usr/bin/perl
# isohybrid-acritox - written by Andreas Loibl <andreas@andreas-loibl.de>
# 
# Post-process a hybrid-ISO-image generated with isohybrid-bg2
# by injecting an "Apple Partition Map" into the image and appending a HFS+-partiton
# and using a FAT-partition embedded as file into the ISO9660 to allow "hybrid booting"
# as CD-ROM (EFI or El Torito) or as a hard-drive on Intel-Macs (EFI) and PCs (EFI or MBR).

$bs=0x0200; $block0='45520200eb5f90'; #  512  -  add    (%eax),%al
$bs=0x0400; $block0='45520400eb5f90'; # 1024  -  add    $0x0,%al
$bs=0x0800; $block0='45520800eb5f90'; # 2048  -  or     %al,(%bx,%si)

# Apple Partition Map entries:
$pm1='504d000000000003000000010000000f4170706c650000000000000000000000000000000000000000000000000000004170706c655f706172746974696f6e5f6d617000000000000000000000000000000000000000000f00000003'; # Apple_partition_map
$pm2='504d00000000000300000400000005006469736b20696d616765000000000000000000000000000000000000000000004170706c655f4846530000000000000000000000000000000000000000000000000000000000040040000033'; # Apple_HFS
$pm3='504d00000000000300000001000004004b414e4f5449585f454649000000000000000000000000000000000000000000444f535f4641545f313200000000000000000000000000000000000000000000000000000000040040000033'; # DOS_FAT_12

die "Usage: $0 <isohybrid-bg2.iso> <HFS+-image> <FAT-image-filename>\n" if $#ARGV != 2;

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

open(PART, "< $part\0") or die "$0: cannot open $part: $!\n";
binmode PART;

# Check if image has already been "patched" (i.e. it has the APM signature from $block0)
seek(FILE, 0, SEEK_SET) or die "$0: $file: $!\n";
read(FILE, $test, 2) == 2 or die "$0: $file: read error\n";
die "$file seems to have an APM signature already...\n" if($test eq 'ER');

# Check if image is a isohybrid-bg2 image (i.e. it has GRUB in its MBR)
seek(FILE, 0x180, SEEK_SET) or die "$0: $file: $!\n";
read(FILE, $test, 4) == 4 or die "$0: $file: read error\n";
die "$file seems not to have GRUB in its MBR (is this a isohybrid-bg2 image?)\n" if($test ne 'GRUB');

# Check if partition contains a HFS+ filesystem
seek(PART, 0x400, SEEK_SET) or die "$0: $file: $!\n";
read(PART, $test, 2) == 2 or die "$0: $file: read error\n";
die "$part doesn't seem to contain a HFS+ filesystem\n" if($test ne 'H+');

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

# 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";
}
# Target image size: round up to a multiple of $bs*512
$cylsize = $bs*512;
$frac = $imgsize % $cylsize;
$padding = ($frac > 0) ? $cylsize - $frac : 0;
$imgsize += $padding;

# Get the total size of the partiton
(@partstat = stat(PART)) or die "$0: $part: $!\n";
$partsize = $partstat[7];
if (!$partsize) {
    die "$0: $part: cannot determine length of file\n";
}

seek(FILE, 0, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('H*',$block0);
seek(FILE, $bs*1, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('H*',$pm1);
seek(FILE, $bs*2, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('H*',$pm2);
seek(FILE, $bs*3, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('H*',$pm3);

# Pad the image to a fake cylinder boundary
seek(FILE, $imgstat[7], SEEK_SET) or die "$0: $file: $!\n";
if ($padding) {
    print FILE "\0" x $padding;
}

# Append partition to image
seek(PART, 0, SEEK_SET) or die "$0: $file: $!\n";
read PART, $partition, $partsize;
print FILE $partition;

# Pad the partition to a fake cylinder boundary
$frac = $partsize % $cylsize;
$padding = ($frac > 0) ? $cylsize - $frac : 0;
if ($padding) {
    print FILE "\0" x $padding;
}
$partsize += $padding;

use integer;
$lba = $start*4;
$psize = $imgsize/512 - $lba;

# Adjust $pm2 (Apple_HFS)
# "physical block start" and "physical block count" of partition:
seek(FILE, $bs*2+8, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('NN', $imgsize/$bs, $partsize/$bs);
# "logical block start" and "logical block count" of partition:
seek(FILE, $bs*2+80, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('NN', 0, $partsize/$bs);

# Adjust $pm3 (DOS_FAT_12)
# "physical block start" and "physical block count" of partition:
seek(FILE, $bs*3+8, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('NN', $lba*512/$bs, $psize*512/$bs);
# "logical block start" and "logical block count" of partition:
seek(FILE, $bs*3+80, SEEK_SET) or die "$0: $file: $!\n";
print FILE pack('NN', 0, $psize*512/$bs);

$imgsize += $partsize;
seek(FILE, $imgsize, SEEK_SET) or die "$0: $file: $!\n";

# Target image size: round up to a multiple of 1MB
$cylsize = 64*32*512; # 1MB
$frac = $imgsize % $cylsize;
$padding = ($frac > 0) ? $cylsize - $frac : 0;
$imgsize += $padding;
if ($padding) {
    print FILE "\0" x $padding;
}

# Done...
close(PART);

# Calculate partiton table (MBR)
$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);

# Done...
close(FILE);

exit 0;