On Sun, Oct 18, 2015 at 11:12:03AM -0400, Ganesh Ajjanagadde wrote:
> On Sun, Oct 18, 2015 at 11:03 AM, Clément Bœsch <u...@pkh.me> wrote:
> > On Sun, Oct 18, 2015 at 10:47:52AM -0400, Ganesh Ajjanagadde wrote:
> > [...]
> >> diff --git a/libavformat/subtitles.c b/libavformat/subtitles.c
> >> index bb89766..16ab245 100644
> >> --- a/libavformat/subtitles.c
> >> +++ b/libavformat/subtitles.c
> >> @@ -23,6 +23,7 @@
> >> #include "avio_internal.h"
> >> #include "libavutil/avassert.h"
> >> #include "libavutil/avstring.h"
> >> +#include "libavutil/qsort.h"
> >>
> >> void ff_text_init_avio(void *s, FFTextReader *r, AVIOContext *pb)
> >> {
> >> @@ -197,9 +198,12 @@ void ff_subtitles_queue_finalize(void *log_ctx,
> >> FFDemuxSubtitlesQueue *q)
> >> {
> >> int i;
> >>
> >> - qsort(q->subs, q->nb_subs, sizeof(*q->subs),
> >> - q->sort == SUB_SORT_TS_POS ? cmp_pkt_sub_ts_pos
> >> - : cmp_pkt_sub_pos_ts);
> >> + if (q->sort == SUB_SORT_TS_POS) {
> >> + AV_QSORT(q->subs, q->nb_subs, AVPacket, cmp_pkt_sub_ts_pos);
> >> + }
> >> + else
> >> + AV_QSORT(q->subs, q->nb_subs, AVPacket, cmp_pkt_sub_pos_ts);
> >> +
> >
> > Weird style.
>
> There were two reasons for this:
> 1. This ensures inlining of the cmp callback.
> 2. I was not sure whether putting the cmp ternary inside the AV_QSORT
> is safe since it is a macro. Did not want to check that, so used the
> above.
I was referring to the { } in one case but not the other, as well as the
else not being on the same line of }.
>
> >
> > BTW, AV_QSORT() Macro should be replaced with a do { ... } while (0) form
> > to make this kind of code safer.
>
> Maybe, but that is separate from this patch.
>
Depends, it could have a functional impact depending on the way the
if/else is done.
> >
> > Also note that using these macro has an impact on final binary size which
> > might not be worth the trouble in various cases.
>
> So how do you want me to measure binary size impact?
[do changes]
git stash
make libavformat/subtitles.o
ls -l libavformat/subtitles.o
git stash pop
make libavformat/subtitles.o
ls -l libavformat/subtitles.o
> Or more
> concretely: which of the above replacements do you think is not
> worthwhile (e.g due to small array size)?
This code is not really speed relevant.
--
Clément B.
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