Rather than allow the "Katamari" (as Guy once fittingly referred to pinfo as) to grow even more by my earlier quick suggestion of adding a field to indicate the number of bytes consumed by the sub-dissector, might there instead be some value in adding some new-style dissector_try_port/heuristic() functions that return the number of bytes dissected rather than simply TRUE or FALSE?
- Chris
-----Original Message-----
From: wireshark-dev-bounces@xxxxxxxxxxxxx [mailto:wireshark-dev-bounces@xxxxxxxxxxxxx] On Behalf Of Stephen Fisher
Sent: Tuesday, April 27, 2010 8:09 PM
To: Developer support list for Wireshark
Subject: Re: [Wireshark-dev] Parsing variable length protocol trailer
On Tue, Apr 27, 2010 at 12:22:14PM -0700, Edgar, Thomas wrote:
> Is there a way to determine how many bytes the subdissectors actually
> used or how many bytes are left unused after a return from
> dissector_try_port/heuristic?
If you were using call_dissector(), which lets you call a
(sub-)dissector after looking up its handle by name, it will return the
number of bytes dissected for new style dissectors (see
call_dissector_work in epan/packet.c) or the length of the tvbuff for
old style dissectors. New style dissectors are registered with
new_create_dissector_handle().
As for dissector_try_port(), it only returns TRUE if the dissector was
found and FALSE if it wasn't. The dissector_try_heuristic() function
works in a similar fashion, returning TRUE if the packet was accepted by
a dissector and FALSE if not.
--
Steve
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