[FFmpeg-devel] [RFC] av_tree enumeration

[Stefano Sabatini]

On date Saturday 2009-11-14 12:22:58 +0100, Michael Niedermayer encoded:
> On Sat, Nov 14, 2009 at 03:00:58PM +1100, Peter Ross wrote:
> > On Sat, Nov 14, 2009 at 01:41:17AM +0100, Stefano Sabatini wrote:
> > > Hi all,
> > > 
> > > I'm considering to use av_tree for storing elements of FFmpeg,
> > > e.g. filters, codecs etc.
> > [...]
> > 
> > > Could someone explain how to use that function, and if it can be used
> > > to do this? I could try some guesswork, but it's faster if someone can
> > > give some hints about it.
> > 
> > Um, call av_tree_enumerate with pointer to the tree and a callback
> > function. The callback function is invoked for every item in the tree.
> > 
> > Example:
> > 
> >    int print_item(void *cntx, void *elem) {
> >       Datatype *s = elem;  
> >       printf("%s\n", s->name);
> >       return 0;
> >    } 
> >    
> >    av_tree_enumerate(tree, cntx, print_item);
> > 
> > I am using a copy of tree.c/h in another project, and have made the following 
> > (trivial) fixes to av_tree_enumerate().
> > 
> > - enumerate the tree in ascending/left-to-right order
> 
> suggestion implemented
> 
> 
> > - stop enumerating if the callback function returns < 0.
> 
> I think that can be done through use of cmp() and opaque in my code with
> the advantage that if its not needed no extra return checks are needed

Further suggestion:

* Fix crash when t == NULL (see attached patch).

* There is no point into having the enu function return something, so
  I'd say to change it from int enu(...) to void enu(...).

Regards.
-- 
FFmpeg = Funny and Forgiving Mystic Programmable Enchanting God
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