[FFmpeg-devel] [PATCH 2/3] avfilter/avfilter: avfilter_register() that works in O(1) time

[Stefano Sabatini]

On date Sunday 2013-12-08 03:55:22 +0100, Michael Niedermayer encoded:
> This also flips the order of the list
> avfilters should be unique and thus the order should not matter
> 
> Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> ---
>  libavfilter/avfilter.c |    8 +++-----
>  1 file changed, 3 insertions(+), 5 deletions(-)
> 
> diff --git a/libavfilter/avfilter.c b/libavfilter/avfilter.c
> index 2567ce9..c564b45 100644
> --- a/libavfilter/avfilter.c
> +++ b/libavfilter/avfilter.c
> @@ -476,7 +476,6 @@ AVFilter *avfilter_get_by_name(const char *name)
>  
>  int avfilter_register(AVFilter *filter)
>  {
> -    AVFilter **f = &first_filter;
>      int i;
>  
>      /* the filter must select generic or internal exclusively */
> @@ -488,10 +487,9 @@ int avfilter_register(AVFilter *filter)
>                      || (!input->start_frame && !input->end_frame));
>      }
>  
> -    filter->next = NULL;
> -
> -    while(*f || avpriv_atomic_ptr_cas((void * volatile *)f, NULL, filter))
> -        f = &(*f)->next;

> +    do {
> +        filter->next = first_filter;
> +    } while (filter->next != avpriv_atomic_ptr_cas((void * volatile *)&first_filter, filter->next, filter));

why do you need a loop for this?

Also, will the order in ffmpeg -filters remain the same (I suppose not).
-- 
FFmpeg = Fantastic and Fundamental Miracolous Philosofic Exuberant Gladiator