[FFmpeg-devel] [PATCH 1/3] avcodec/utils: av_register_codec & hwaccel() that work in O(1) time

[Michael Niedermayer]

On Mon, Dec 16, 2013 at 05:01:47PM +0100, Stefano Sabatini wrote:
> On date Sunday 2013-12-08 03:55:21 +0100, Michael Niedermayer encoded:
> > Its possible to implement this with a few lines less code but it then
> > would flip the order of the list and require registration of external
> > codecs to be done first, also it could break user applications due to
> > this. Thus to maintain ABI this slighty more complex solution is
> > used.
> > 
> > Signed-off-by: Michael Niedermayer <michaelni at gmx.at>
> > ---
> >  libavcodec/utils.c |    8 ++++++--
> >  1 file changed, 6 insertions(+), 2 deletions(-)
> > 
> > diff --git a/libavcodec/utils.c b/libavcodec/utils.c
> > index 102a049..8d96bd0 100644
> > --- a/libavcodec/utils.c
> > +++ b/libavcodec/utils.c
> > @@ -169,6 +169,7 @@ void av_fast_padded_mallocz(void *ptr, unsigned int *size, size_t min_size)
> >  
> >  /* encoder management */
> >  static AVCodec *first_avcodec = NULL;
> > +static AVCodec **last_avcodec = &first_avcodec;
> >  
> >  AVCodec *av_codec_next(const AVCodec *c)
> >  {
> > @@ -204,11 +205,12 @@ av_cold void avcodec_register(AVCodec *codec)
> >  {
> >      AVCodec **p;
> >      avcodec_init();
> > -    p = &first_avcodec;
> > +    p = last_avcodec;
> >      codec->next = NULL;
> >  
> >      while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, codec))
> >          p = &(*p)->next;
> > +    last_avcodec = &codec->next;
> >  
> >      if (codec->init_static_data)
> >          codec->init_static_data(codec);
> > @@ -3187,13 +3189,15 @@ FF_ENABLE_DEPRECATION_WARNINGS
> >  #endif /* FF_API_MISSING_SAMPLE */
> >  
> >  static AVHWAccel *first_hwaccel = NULL;
> > +static AVHWAccel **last_hwaccel = &first_hwaccel;
> >  
> >  void av_register_hwaccel(AVHWAccel *hwaccel)
> >  {
> > -    AVHWAccel **p = &first_hwaccel;
> > +    AVHWAccel **p = last_hwaccel;
> >      hwaccel->next = NULL;
> >      while(*p || avpriv_atomic_ptr_cas((void * volatile *)p, NULL, hwaccel))
> >          p = &(*p)->next;
> > +    last_hwaccel = &hwaccel->next;
> >  }
> 
> LGTM.

applied

thanks

[...]
-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

The misfortune of the wise is better than the prosperity of the fool.
-- Epicurus
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