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, 2 insertions, 4 deletions

diff --git a/libavfilter/vf_program_opencl.c b/libavfilter/vf_program_opencl.c
index 502d797154..d80aa9be04 100644
--- a/libavfilter/vf_program_opencl.c
+++ b/libavfilter/vf_program_opencl.c
@@ -359,7 +359,6 @@ static const AVFilterPad program_opencl_outputs[] = {
         .type         = AVMEDIA_TYPE_VIDEO,
         .config_props = &program_opencl_config_output,
     },
-    { NULL }
 };
 
 const AVFilter ff_vf_program_opencl = {
@@ -374,7 +373,7 @@ const AVFilter ff_vf_program_opencl = {
     .query_formats  = &ff_opencl_filter_query_formats,
     .activate       = &program_opencl_activate,
     .inputs         = NULL,
-    .outputs        = program_opencl_outputs,
+    FILTER_OUTPUTS(program_opencl_outputs),
     .flags_internal = FF_FILTER_FLAG_HWFRAME_AWARE,
 };
 
@@ -413,7 +412,6 @@ static const AVFilterPad openclsrc_outputs[] = {
         .config_props  = &program_opencl_config_output,
         .request_frame = &program_opencl_request_frame,
     },
-    { NULL }
 };
 
 const AVFilter ff_vsrc_openclsrc = {
@@ -425,7 +423,7 @@ const AVFilter ff_vsrc_openclsrc = {
     .uninit         = &program_opencl_uninit,
     .query_formats  = &ff_opencl_filter_query_formats,
     .inputs         = NULL,
-    .outputs        = openclsrc_outputs,
+    FILTER_OUTPUTS(openclsrc_outputs),
     .flags_internal = FF_FILTER_FLAG_HWFRAME_AWARE,
 };