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

[Jeff Morriss <jeff.morriss.ws@xxxxxxxxx>]

This bit me (again?) today so I've checked in your proposed text 
(modified slightly): rev 22293.

Jaap Keuter wrote:
> 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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