From d53d48c7993fe2e9ffcc4a638ebd2f4c5273c144 Mon Sep 17 00:00:00 2001 From: Andreas Rheinhardt Date: Thu, 12 Aug 2021 17:35:37 +0200 Subject: [PATCH] fftools/cmdutils: Use avfilter_pad_count() for AVFilter's number of pads 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. Reviewed-by: Nicolas George Signed-off-by: Andreas Rheinhardt --- fftools/cmdutils.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) 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));