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#!/usr/bin/perl
#
# Construct a checksum for isolinux*.bin, compatible
# with an mkisofs boot-info-table
#
use bytes;
use integer;
($file) = @ARGV;
open(FILE, '+<', $file) or die "$0: Cannot open $file: $!\n";
binmode FILE;
if ( !seek(FILE,64,0) ) {
die "$0: Cannot seek past header\n";
}
$csum = 0;
$bytes = 64;
while ( ($n = read(FILE, $dw, 4)) > 0 ) {
$dw .= "\0\0\0\0"; # Pad to at least 32 bits
($v) = unpack("V", $dw);
$csum = ($csum + $v) & 0xffffffff;
$bytes += $n;
}
if ( !seek(FILE,16,0) ) {
die "$0: Cannot seek to header\n";
}
print FILE pack("VV", $bytes, $csum);
close(FILE);
exit 0;
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