From 2937f20f6973122c4c43d6b6f0c11e4c687cfbbf Mon Sep 17 00:00:00 2001
From: Andreas Loibl <andreas@andreas-loibl.de>
Date: Mon, 21 May 2012 09:35:17 +0200
Subject: fixed CHS calculation for images < 1GB
---
isohybrid-acritox | 40 +++++++++++++++++++++++++---------------
1 file changed, 25 insertions(+), 15 deletions(-)
diff --git a/isohybrid-acritox b/isohybrid-acritox
index 657f377..68d8206 100755
--- a/isohybrid-acritox
+++ b/isohybrid-acritox
@@ -346,29 +346,39 @@ print "iso_pos: $iso_pos iso_size: $iso_size\n" if($debug);
print "final imgsize: $imgsize\n" if($debug);
# Calculate and write partiton table (MBR)
-$h = 64; $s = 32;
-$hpc = 32; $spt = 63;
-$cc = min(1024, $imgsize/$cylsize);
+sub lba2chs
+{
+ my $lba = @_;
+ my $hpc = 64, $spt = 32, $c, $h, $s;
+ $c = $lba / ($spt * $hpc);
+ $h = ($lba / $spt) % $hpc;
+ $s = ($lba % $spt) + 1;
+ if($c >= 1024)
+ {
+ $c = 1023;
+ $h = 254;
+ $s = 63;
+ }
+ # Head Sect Cyl
+ # <-Byte-> <-Byte-> <-Byte->
+ # 76543210 98543210 76543210
+ # HHHHHHHH CCSSSSSS CCCCCCCC
+ $s += ($c & 0x300) >> 2;
+ $c &= 0xff;
+ return ($c, $h, $s);
+}
$pentry = 1;
$fstype = 0xEF;
-$bcyl = $fat_pos_lba / ($spt * $hpc);
-$bhead = ($fat_pos_lba / $spt) % $hpc;
-$bsect = ($fat_pos_lba % $spt) + 1;
-$ehead = $h-1;
-$esect = $s + ((($cc-1) & 0x300) >> 2);
-$ecyl = ($cc-1) & 0xff;
+($bcyl, $bhead, $bsect) = lba2chs($fat_pos_lba);
+($ecyl, $ehead, $esect) = lba2chs($fat_pos_lba+$fat_size_lba-1);
seek(FIMG, 430+16*$pentry, SEEK_SET) or die "$0: $file: $!\n";
print FIMG pack("CCCCCCCCVV", 0x80, $bhead, $bsect, $bcyl, $fstype, $ehead, $esect, $ecyl, $fat_pos_lba, $fat_size_lba);
$pentry = 2;
$fstype = 0x83;
-$bcyl = $iso_pos_lba / ($spt * $hpc);
-$bhead = ($iso_pos_lba / $spt) % $hpc;
-$bsect = ($iso_pos_lba % $spt) + 1;
-$ehead = $h-1;
-$esect = $s + ((($cc-1) & 0x300) >> 2);
-$ecyl = ($cc-1) & 0xff;
+($bcyl, $bhead, $bsect) = lba2chs($iso_pos_lba);
+($ecyl, $ehead, $esect) = lba2chs($iso_pos_lba+$iso_size_lba-1);
seek(FIMG, 430+16*$pentry, SEEK_SET) or die "$0: $file: $!\n";
print FIMG pack("CCCCCCCCVV", 0x00, $bhead, $bsect, $bcyl, $fstype, $ehead, $esect, $ecyl, $iso_pos_lba, $iso_size_lba);
--
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