Hello,

I've written a little script and it is working. My input is a hexstream. It is constructed as follows:

• once a null terminated string, i.e. Z*
• many repetitions of: id, offset, size, path, crc32 (n n N A<offset-4> N) x ?

The problem is that there is a string with variable length (path). The length of the path is the value of the offset-4.

The following script is working.

#!/usr/bin/perl

use strict;
use warnings;

my $mem = "";
my ($section, $load_id, $offset_to_next_load, $load_size, $load_path, 
+$crc32_load_path);

my $hex_data = "54424c004100001300000BAD2F62696E2F7465737432302E64666C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";

# put hex data into memory
$mem = pack('H*', $hex_data );

# unpack null terminated section name from memory
$section = unpack('Z*', $mem);
$mem = substr($mem, length($section) + 1 );

# print section name
print $section . ":\n";
for (1 .. length($section) + 1){print "-"}
print "\n\n";

# unpack and print load id, offset, size, path (length of path is "off
+set - 4") and crc32 of each load entry
while (length($mem) > 0)
{
    ($load_id, $offset_to_next_load, $load_size) = unpack('n n N', $me
+m);
    $mem = substr($mem, 8);

    print "Load ID             : " . $load_id . "\n";
    print "Offset to next load : " . $offset_to_next_load . "\n";
    print "Load Size           : " . $load_size . "\n";

    ($load_path, $crc32_load_path) = unpack('A' . ($offset_to_next_loa
+d-4) . 'N', $mem);
    $mem = substr($mem, $offset_to_next_load);

    print "Load Path           : " . $load_path . "\n";
    print "CRC32 of Load Path  : " . $crc32_load_path . "\n";

    print "\n\n";
}
[download]

It would be very interesting for me if it is possible to read the hex data with one elegant unpack command. I tried it but because of the variable length of the path I did not get a solution. And of course due to the repetitions the following variables would have to be arrays instead of scalars ($load_id, $offset_to_next_load, $load_size). But I think that I could handle this with a map command within the unpack command. My main problem is the variable length of the path.

Thank you for your help.

Dirk

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