On Mon, 04 Nov 2013 21:35:45 +0100
Anton Khirnov <an...@khirnov.net> wrote:
>
> On Mon, 4 Nov 2013 21:02:02 +0100, wm4 <nfx...@googlemail.com> wrote:
> > On Sun, 3 Nov 2013 23:27:48 +0100
> > Anton Khirnov <an...@khirnov.net> wrote:
> >
> > > We will likely want to add new fields to it in the future, so this is
> > > needed to avoid breaking ABI.
> > > ---
> > > doc/APIchanges | 2 ++
> > > libavcodec/vdpau.c | 5 +++++
> > > libavcodec/vdpau.h | 11 +++++++++++
> > > 3 files changed, 18 insertions(+)
> > >
> > > diff --git a/doc/APIchanges b/doc/APIchanges
> > > index 93d1608..db30bb9 100644
> > > --- a/doc/APIchanges
> > > +++ b/doc/APIchanges
> > > @@ -15,6 +15,8 @@ API changes, most recent first:
> > >
> > > 2013-11-xx - xxxxxxx - lavc 55.25.0 - vdpau.h
> > > Add av_vdpau_get_profile().
> > > + Add av_vdpau_alloc_context(). This function must from now on be
> > > + used for allocating AVVDPAUContext.
> > >
> > > 2013-08-xx - xxxxxxx - lavu 52.17.0 - avframe.h
> > > Add AVFrame.flags and AV_FRAME_FLAG_CORRUPT.
> > > diff --git a/libavcodec/vdpau.c b/libavcodec/vdpau.c
> > > index 5cabb7e..ba11195 100644
> > > --- a/libavcodec/vdpau.c
> > > +++ b/libavcodec/vdpau.c
> > > @@ -127,4 +127,9 @@ int av_vdpau_get_profile(AVCodecContext *avctx)
> > > return AVERROR(EINVAL);
> > > }
> > >
> > > +AVVDPAUContext *av_vdpau_alloc_context(void)
> > > +{
> > > + return av_mallocz(sizeof(AVVDPAUContext));
> > > +}
> > > +
> > > /* @}*/
> > > diff --git a/libavcodec/vdpau.h b/libavcodec/vdpau.h
> > > index 49ca6f0..16547e4 100644
> > > --- a/libavcodec/vdpau.h
> > > +++ b/libavcodec/vdpau.h
> > > @@ -72,6 +72,10 @@ union AVVDPAUPictureInfo {
> > > * during initialization or through each AVCodecContext.get_buffer()
> > > * function call. In any case, they must be valid prior to calling
> > > * decoding functions.
> > > + *
> > > + * This size of this structure is not a part of the public ABI and must
> > > not
> > > + * be used outside of libavcodec. Use av_vdpau_alloc_context() to
> > > allocate an
> > > + * AVVDPAUContext.
> > > */
> > > typedef struct AVVDPAUContext {
> > > /**
> > > @@ -125,6 +129,13 @@ typedef struct AVVDPAUContext {
> > > } AVVDPAUContext;
> > >
> > > /**
> > > + * Allocate an AVVDPAUContext.
> > > + *
> > > + * @return newly allocated AVVDPAUContext or NULL on failure.
> > > + */
> > > +AVVDPAUContext *av_vdpau_alloc_context(void);
> > > +
> > > +/**
> > > * Get a decoder profile that should be used for initializing a VDPAU
> > > decoder.
> > > * Should be called from the AVCodecContext.get_format() callback.
> > > *
> >
> > As far as I'm aware, the only fields the user has to access are decoder
> > and render. If you're going to change the API, maybe make this struct
> > non-public, let libavcodec allocate it, and add setters for the
> > decoder/render fields.
>
> Those are also the only fields that exist in that struct. The whole point of
> it
Plus a bunch of deprecated stuff.
> is that it's all public. Non-public parts are hidden deeper in lavc.
>
> So I really don't see any advantage to making it opaque.
I don't think having public fields in structs ever worked out well in
libav*. It's an endless cycle of deprecations, ABI hacks, and working
around bad ABI properties of structs (like adding a constructor
function).
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