checksumiso.pl

   1 #!/usr/bin/perl
   2 #
   3 # Construct a checksum for isolinux*.bin, compatible
   4 # with an mkisofs boot-info-table
   5 #
   6
   7 use bytes;
   8 use integer;
   9
  10 ($file) = @ARGV;
  11
  12 open(FILE, '+<', $file) or die "$0: Cannot open $file: $!\n";
  13 binmode FILE;
  14
  15 if ( !seek(FILE,64,0) ) {
  16     die "$0: Cannot seek past header\n";
  17 }
  18
  19 $csum  = 0;
  20 $bytes = 64;
  21 while ( ($n = read(FILE, $dw, 4)) > 0 ) {
  22     $dw .= "\0\0\0\0";          # Pad to at least 32 bits
  23     ($v) = unpack("V", $dw);
  24     $csum  = ($csum + $v) & 0xffffffff;
  25     $bytes += $n;
  26 }
  27
  28 if ( !seek(FILE,16,0) ) {
  29     die "$0: Cannot seek to header\n";
  30 }
  31
  32 print FILE pack("VV", $bytes, $csum);
  33
  34 close(FILE);
  35
  36 exit 0;