Andreas Rheinhardt (12021-08-15): > Besides being nicer code this also has the advantage of not making > assumptions about the internal implementation: While it is documented > that the AVFilter.inputs and AVFilter.outputs arrays are terminated > by a zeroed sentinel, one is not allowed to infer that one can just > check avfilter_pad_get_name(padarray, i) to see whether one has reached > the sentinel: > It could be that the pointer to the string is contained > in a different structure than AVFilterPad that needs to be accessed > first: return pad->struct->string. > It could be that for small strings an internal buffer in > AVFilterPad is used (to avoid a relocation) whereas for longer strings > an external string is used; this is useful to avoid relocations: > return pad->string_ptr ? pad->string_ptr : pad->interal_string > Or it could be that the name has a default value: > return pad->name ? pad->name : "default" > (This actually made sense for us because the name of most of our > AVFilterPads is just "default"; doing so would save lots of relocations.) > > The only thing one is allowed to infer from the existence of the > sentinel is that one is allowed to use avfilter_pad_count() to get > the number of pads. Therefore it is used. > > Signed-off-by: Andreas Rheinhardt <andreas.rheinha...@outlook.com> > --- > Unchanged since last time. > > fftools/cmdutils.c | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-)
It means this bit of code will be inefficient for a few commits that
will be pushed at the same time. I am ok with it. I do not maintain
this, but LGTM.
> diff --git a/fftools/cmdutils.c b/fftools/cmdutils.c
> index 6d0bcd6085..96d38803df 100644
> --- a/fftools/cmdutils.c
> +++ b/fftools/cmdutils.c
> @@ -1707,12 +1707,14 @@ int show_filters(void *optctx, const char *opt, const
> char *arg)
> while ((filter = av_filter_iterate(&opaque))) {
> descr_cur = descr;
> for (i = 0; i < 2; i++) {
> + unsigned nb_pads;
> if (i) {
> *(descr_cur++) = '-';
> *(descr_cur++) = '>';
> }
> pad = i ? filter->outputs : filter->inputs;
> - for (j = 0; pad && avfilter_pad_get_name(pad, j); j++) {
> + nb_pads = avfilter_pad_count(pad);
> + for (j = 0; j < nb_pads; j++) {
> if (descr_cur >= descr + sizeof(descr) - 4)
> break;
> *(descr_cur++) =
> get_media_type_char(avfilter_pad_get_type(pad, j));
Regards,
--
Nicolas George
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