Wireshark · Wireshark-dev: Re: [Wireshark-dev] What do you use to get a boolean

[Jaap Keuter <jaap.keuter@xxxxxxxxx>]

Hi,

Reading from README.developer it states:
<quote>
For proto_tree_add_boolean(), the 'value' argument is a 32-bit integer;
zero means "false", and non-zero means "true".
</quote>
That is misleading. You have to take into account the field info to
determine the interpretation of this value (see epan/proto.c :
proto_tree_set_uint() ). You can define a mask of the relevant bit(s) and
this will be applied (mask AND shift) before adding the value to the tree.
So how about this text for README.developer:
<quote>
For proto_tree_add_boolean(), the 'value' argument is a 32-bit integer.
It is masked and shifted as defined by the field info, then zero means
"false", and non-zero means "true".
</quote>

Thanx,
Jaap

On Mon, 26 Feb 2007, Hal Lander wrote:

> Steve,
>
> Its more what the documentation does not say that caused me the problem.
>
> The function is called 'add_boolean' and it has a parameter 'value'.
> I had assumed, incorrectly, that 'value' would be a 1 or a 0.
> It is not, it is the value of the packet byte that requires to be masked and
> shifted to get the boolean. It would be helpful if the documentation defined
> 'value' more explicitly.
>
> Also Wireshark has functions which do the masking and shifting to get the
> boolean value.
> It would be helpful if these functions were exposed in the API so that
> dissector writers can use them. If I want to find the actual boolean value
> of the field I have to write my own functions for masking and shifting. That
> is not a big issue, but it is duplicating existing code, requires testing
> and is another source of bugs - better to use the Wireshark functions if
> they could be made available.
>
> I hope this is helpful, the effort required to generate documentation is
> much appreciated and how Wireshark works is gradually starting to clik into
> place in my mind.
>
> Hal.
>
>
> >From: Stephen Fisher <stephentfisher@xxxxxxxxx>
> >Reply-To: Developer support list for Wireshark
> ><wireshark-dev@xxxxxxxxxxxxx>
> >To: Developer support list for Wireshark <wireshark-dev@xxxxxxxxxxxxx>
> >Subject: Re: [Wireshark-dev] What do you use to get a boolean
> >Date: Wed, 21 Feb 2007 23:25:44 -0800
> >
> >On Mon, Feb 12, 2007 at 06:15:43AM -0900, Hal Lander wrote:
> > > It does look like the value you pass to
> > > proto_tree_add_boolean(tree, id, tvb, start, length, value);
> > > is not a 1 or a 0 it is the raw data byte containing the boolean at the
> > > position defined by the mask.
> > >
> > > If I am correct this makes the documentation a bit missleading.
> >
> >As Guy said, you have to do the masking yourself.  What part of the
> >documentation did you find misleading?  I ask so that we can take a look
> >at improving it.
> >
> >
> >Steve
> >
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>
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