Wireshark · Wireshark-dev: Re: [Wireshark-dev] [Wireshark-commits] rev 39149: /trunk/epan/dissectors/ /trunk/epan/dissectors/:

[Anders Broman <a.broman@xxxxxxxxxxxx>]

Jeff Morriss skrev 2011-09-27 21:56:
> Anders Broman wrote:
> > Anders Broman skrev 2011-09-26 18:25:
> > > Stig Bjørlykke skrev 2011-09-26 18:14:
> > > > On Mon, Sep 26, 2011 at 4:51 PM,<etxrab@xxxxxxxxxxxxx>  wrote:
> > > > > Log:
> > > > >   Get rid of check_col, while at it set ENC.
> > > > >
> > > > > Directory: /trunk/epan/dissectors/
> > > > >   Changes    Path                      Action
> > > > >   +35 -37    packet-dmp.c              Modified
> > > > The remaining check_col in packet-dmp.c was left on purpose, because
> > > > we do not need this calculations if not having COL_INFO.
> > > >
> > > > Should we really remove all occurrences of check_col?
> > > Perhaps not, but how often isn't the info column present?
> > Thinking about it this raises the question
> > - is check_col deprecated or not?
> > Should lengthy code to compute column info be protected in some other 
> > manner?
> >  fd->visited? (!tree)? We only fill in the column info on the first 
> > pass before the tree is built, right?
>
> Actually a quick test indicates that we only build the column info on 
> the 2nd pass (for those frames which are currently displayed).
>
> In other words, if you've got 10,000 frames of which 25 are displayed 
> in your Wireshark window, your dissector is called 10,000 times with 
> check_col(COL_INFO)==0 and 25 times with check_col(COL_INFO)==1.  As 
> you scroll down the dissector is called again for the newly-visible 
> frames with check_col(COL_INFO)==1.  (It does appear that Wireshark 
> does cache the column information; scrolling back or clicking on 
> earlier packets does not result in the column info being rebuilt, even 
> if the dissector is called again.)
>
> Actually another case when column info won't be present is tshark when 
> doing statistics, etc., but not printing the packet details.
>
> This suggests that check_col()'s should be left in--at least if they 
> are protecting us from doing some work, including val_to_str()'s.
Even though the check_col is built into the function calls them self s?
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