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author | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2021-08-12 17:35:37 +0200 |
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committer | Andreas Rheinhardt <andreas.rheinhardt@outlook.com> | 2021-08-20 12:52:33 +0200 |
commit | d53d48c7993fe2e9ffcc4a638ebd2f4c5273c144 (patch) | |
tree | 198576c72a2f125c777cb6d197938b1c62b15993 | |
parent | c83a7dd25fdf9636e7e5da3fad5e0d82035b9c86 (diff) | |
download | ffmpeg-d53d48c7993fe2e9ffcc4a638ebd2f4c5273c144.tar.gz |
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 <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
-rw-r--r-- | fftools/cmdutils.c | 4 |
1 files changed, 3 insertions, 1 deletions
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)); |