avfilter/avfilter: Add numbers of (in|out)pads directly to AVFilter

Up until now, an AVFilter's lists of input and output AVFilterPads
were terminated by a sentinel and the only way to get the length
of these lists was by using avfilter_pad_count(). This has two
drawbacks: first, sizeof(AVFilterPad) is not negligible
(i.e. 64B on 64bit systems); second, getting the size involves
a function call instead of just reading the data.

This commit therefore changes this. The sentinels are removed and new
private fields nb_inputs and nb_outputs are added to AVFilter that
contain the number of elements of the respective AVFilterPad array.

Given that AVFilter.(in|out)puts are the only arrays of zero-terminated
AVFilterPads an API user has access to (AVFilterContext.(in|out)put_pads
are not zero-terminated and they already have a size field) the argument
to avfilter_pad_count() is always one of these lists, so it just has to
find the filter the list belongs to and read said number. This is slower
than before, but a replacement function that just reads the internal numbers
that users are expected to switch to will be added soon; and furthermore,
avfilter_pad_count() is probably never called in hot loops anyway.

This saves about 49KiB from the binary; notice that these sentinels are
not in .bss despite being zeroed: they are in .data.rel.ro due to the
non-sentinels.

Reviewed-by: Nicolas George <george@nsup.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>

1 files changed, 4 insertions, 8 deletions

diff --git a/libavfilter/af_afade.c b/libavfilter/af_afade.c
index f39c0e45b6..a55d5d72c3 100644
--- a/libavfilter/af_afade.c
+++ b/libavfilter/af_afade.c
@@ -340,7 +340,6 @@ static const AVFilterPad avfilter_af_afade_inputs[] = {
         .type         = AVMEDIA_TYPE_AUDIO,
         .filter_frame = filter_frame,
     },
-    { NULL }
 };
 
 static const AVFilterPad avfilter_af_afade_outputs[] = {
@@ -349,7 +348,6 @@ static const AVFilterPad avfilter_af_afade_outputs[] = {
         .type         = AVMEDIA_TYPE_AUDIO,
         .config_props = config_output,
     },
-    { NULL }
 };
 
 const AVFilter ff_af_afade = {
@@ -358,8 +356,8 @@ const AVFilter ff_af_afade = {
     .query_formats = query_formats,
     .priv_size     = sizeof(AudioFadeContext),
     .init          = init,
-    .inputs        = avfilter_af_afade_inputs,
-    .outputs       = avfilter_af_afade_outputs,
+    FILTER_INPUTS(avfilter_af_afade_inputs),
+    FILTER_OUTPUTS(avfilter_af_afade_outputs),
     .priv_class    = &afade_class,
     .process_command = process_command,
     .flags         = AVFILTER_FLAG_SUPPORT_TIMELINE_GENERIC,
@@ -628,7 +626,6 @@ static const AVFilterPad avfilter_af_acrossfade_inputs[] = {
         .name         = "crossfade1",
         .type         = AVMEDIA_TYPE_AUDIO,
     },
-    { NULL }
 };
 
 static const AVFilterPad avfilter_af_acrossfade_outputs[] = {
@@ -637,7 +634,6 @@ static const AVFilterPad avfilter_af_acrossfade_outputs[] = {
         .type          = AVMEDIA_TYPE_AUDIO,
         .config_props  = acrossfade_config_output,
     },
-    { NULL }
 };
 
 const AVFilter ff_af_acrossfade = {
@@ -647,8 +643,8 @@ const AVFilter ff_af_acrossfade = {
     .priv_size     = sizeof(AudioFadeContext),
     .activate      = activate,
     .priv_class    = &acrossfade_class,
-    .inputs        = avfilter_af_acrossfade_inputs,
-    .outputs       = avfilter_af_acrossfade_outputs,
+    FILTER_INPUTS(avfilter_af_acrossfade_inputs),
+    FILTER_OUTPUTS(avfilter_af_acrossfade_outputs),
 };
 
 #endif /* CONFIG_ACROSSFADE_FILTER */