At Fri, 30 Sep 2005 07:58:22 +1000, Telford Tendys wrote:
> How about writing a network protocol stack. You get a packet and all
> you know about it is that here is a block of memory. You then have
> to figure out what sort of packet it is, how long it is and what
> structure to give it. C handles this very nicely with pointers to
> structures that can be cast into whatever you need.
Since you dared me, here's some (untested) perl5 code that will parse
a TCP header, including network byte order conversions and bitfields:
my ($source, $dest, $seq, $ack_seq,
$off, undef, undef, $urg, $ack, $psh, $rst, $syn, $fin,
$window, $check, $urg_ptr) = unpack 'n2 N2 C B8 n3', $tcpdata;
$off &= 0x0F;
(this is fun ;)
--
- Gus
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