Wireshark-dev: Re: [Wireshark-dev] Filtering
From: "Maynard, Chris" <[email protected]>
Date: Tue, 31 Mar 2009 17:21:17 -0400
Well, I'm not entirely sure what you're trying to do and don't really have the time to dig into it, but let me give it a quick shot using your "time" example below ...

It looks like maybe you're trying to add a time field of some length starting at offset 0 from your tvbuff.  If it's just a string, either NULL-terminated or with a preceding length field, you might be able to use either proto_tree_add_string(), or proto_tree_add_item() but just set your hf's FT_ appropriately, i.e., FT_STRING, FT_STRINGZ, or FT_UINT_STRING.  Or maybe you can make use of proto_tree_add_time() with your hf_'s FT_ set to FT_ABSOLUTE_TIME or FT_RELATIVE_TIME.  I have no idea what the format of your time field is so I don't know which one, if any of these, would work best for you.  Take a look at epan/ftypes/ftypes.h for a complete list of the FT_'s ... and as always, the README.developer lists them all too, along with a description, and again, there are plenty of examples of dissectors using all these types in epan/dissectors/packet-xyz.c.

As a quick example, let me assume your time field is just a Pascal-style string containing a single byte that indicates the length of the string, followed by the string itself.  The following pseudo-code is a rough example of how you might add it to your tree and have it be a filterable field:

static int hf_icom_time = -1;

dissect_icom(...) {

    proto_tree_add_item(icom_message_tree, hf_icom_time, tvb, 0, 1, FALSE);



    { &hf_icom_time,
        { "Timestamp", "icom.time", FT_UINT_STRING, BASE_NONE,
        NULL, 0x00, "", HFILL }

That's pretty much it.  OK, so maybe you have to massage the string first through your _GetMsgTime() function.  No problem, maybe the proto_tree_add_string_format() function call is worth a look.  There are other proto_tree_add_xyz_format() calls as well that might also be of interest to you.

Not sure if that helps or not, but that's all I have time for today :)
- Chris

> -----Original Message-----
> From: [email protected] [mailto:[email protected]]
> Sent: Tuesday, March 31, 2009 4:20 PM
> To: Developer support list for Wireshark
> Cc: Maynard, Chris
> Subject: Re: [Wireshark-dev] Filtering
> I have read through both of those, though i probably should do it again
> now that i know more. But maybe I'm just confused on how the others are
> outputted. right now i add to the tree with:
> time = (_GetMsgTime)();
> pi = proto_tree_add_text(icom_message_tree, tvb, 0, 0, "Time: %s",
> time);
> where time is a char *. in the other proto_tree_add_'s, does it go to
> the hf_icom_* in proto register? and output from there? That's how i
> output the first message:
> { &hf_icom_bnp_type,
> 	{ "ICom BNP Type", "icom.type",
> 	VALS(bnp_type_names), 0x0,
>          },
> would there be a way to put my function somewhere in these calls? such
> as:
> { &hf_icom_message,
> 	{"Message", "icom.message",
> 	(function call here?), 0x0,
> 	}
> or maybe in a value_string? all functions return a char * or int as
> their only types. Maybe i dont have a very understanding of how the
> proto_tree_add and hf[] array works and all.
> Greg
> ---- "Maynard wrote:
> =============
> I would suggest reading through doc/README.developer and
> epan/proto.[h|c] and choosing the best proto_tree_add_xyz() call that
> meets your needs.  Maybe something like proto_tree_add_bytes() or
> proto_tree_add_item() will work for you, I don't know.  There are quite
> a number of them to choose from, so I'm pretty sure you'll find one
> that works for you.  And don't forget to look at other dissectors in
> epan/dissectors/ for some helpful examples.

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