On Thu, Nov 20, 2014 at 12:48 AM, Iago Toral <ito...@igalia.com> wrote:
> On Wed, 2014-11-19 at 14:15 -0600, Patrick Baggett wrote:
> >
> >
> > On Tue, Nov 18, 2014 at 3:23 AM, Iago Toral Quiroga
> > <ito...@igalia.com> wrote:
> > We have _mesa_swap{2,4} but these do in-place byte-swapping
> > only. The new
> > functions receive an extra parameter so we can swap bytes on a
> > source
> > input array and store the results in a (possibly different)
> > destination
> > array.
> >
> >
> >
> > If this is being split into an "in-place" and "different pointers"
> > version, I think using the "restrict" keyword would be useful here to
> > improve the performance. Then, the in-place one cannot be implemented
> > as copy(p,p,n), but the code isn't overly complicated.
>
> I did not know about 'restrict', thanks for the tip!.
>
> It kind of defeats the original idea of not duplicating the code but it
> is true that it is not particularly complex anyway, so maybe it is worth
> it if Jason agrees with having two versions of the functions instead of
> just one in the end. Jason, what do you think?
>
The restrict keyword is a C99 thing and I don't think it's supported in
MSVC so that would be a problem. If it won't build with MSVC then it's a
non-starter. If MSVC can handle "restrict", then I don't know that I care
much either way about 2 functions or 4
>
> Iago
>
> >
> >
> > This is useful to implement byte-swapping in pixel uploads,
> > since in this
> > case we need to swap bytes on the src data which is owned by
> > the
> > application so we can't do an in-place byte swap.
> > ---
> > src/mesa/main/image.c | 25 +++++++++++++++++--------
> > src/mesa/main/image.h | 10 ++++++++--
> > 2 files changed, 25 insertions(+), 10 deletions(-)
> >
> > diff --git a/src/mesa/main/image.c b/src/mesa/main/image.c
> > index 4ea5f04..9ad97c5 100644
> > --- a/src/mesa/main/image.c
> > +++ b/src/mesa/main/image.c
> > @@ -41,36 +41,45 @@
> >
> >
> > /**
> > - * Flip the order of the 2 bytes in each word in the given
> > array.
> > + * Flip the order of the 2 bytes in each word in the given
> > array (src) and
> > + * store the result in another array (dst). For in-place
> > byte-swapping this
> > + * function can be called with the same array for src and
> > dst.
> > *
> > - * \param p array.
> > + * \param dst the array where byte-swapped data will be
> > stored.
> > + * \param src the array with the source data we want to
> > byte-swap.
> > * \param n number of words.
> > */
> > void
> > -_mesa_swap2( GLushort *p, GLuint n )
> > +_mesa_swap2_copy( GLushort *dst, GLushort *src, GLuint n )
> > {
> > GLuint i;
> > for (i = 0; i < n; i++) {
> > - p[i] = (p[i] >> 8) | ((p[i] << 8) & 0xff00);
> > + dst[i] = (src[i] >> 8) | ((src[i] << 8) & 0xff00);
> > }
> > }
> >
> >
> >
> > /*
> > - * Flip the order of the 4 bytes in each word in the given
> > array.
> > + * Flip the order of the 4 bytes in each word in the given
> > array (src) and
> > + * store the result in another array (dst). For in-place
> > byte-swapping this
> > + * function can be called with the same array for src and
> > dst.
> > + *
> > + * \param dst the array where byte-swapped data will be
> > stored.
> > + * \param src the array with the source data we want to
> > byte-swap.
> > + * \param n number of words.
> > */
> > void
> > -_mesa_swap4( GLuint *p, GLuint n )
> > +_mesa_swap4_copy( GLuint *dst, GLuint *src, GLuint n )
> > {
> > GLuint i, a, b;
> > for (i = 0; i < n; i++) {
> > - b = p[i];
> > + b = src[i];
> > a = (b >> 24)
> > | ((b >> 8) & 0xff00)
> > | ((b << 8) & 0xff0000)
> > | ((b << 24) & 0xff000000);
> > - p[i] = a;
> > + dst[i] = a;
> > }
> > }
> >
> > diff --git a/src/mesa/main/image.h b/src/mesa/main/image.h
> > index abd84bf..79c6e68 100644
> > --- a/src/mesa/main/image.h
> > +++ b/src/mesa/main/image.h
> > @@ -33,10 +33,16 @@ struct gl_context;
> > struct gl_pixelstore_attrib;
> >
> > extern void
> > -_mesa_swap2( GLushort *p, GLuint n );
> > +_mesa_swap2_copy( GLushort *dst, GLushort *src, GLuint n );
> >
> > extern void
> > -_mesa_swap4( GLuint *p, GLuint n );
> > +_mesa_swap4_copy( GLuint *dst, GLuint *src, GLuint n );
> > +
> > +static inline void
> > +_mesa_swap2( GLushort *p, GLuint n ) { _mesa_swap2_copy(p, p,
> > n); }
> > +
> > +static inline void
> > +_mesa_swap4( GLuint *p, GLuint n ) { _mesa_swap4_copy(p, p,
> > n); }
> >
> > extern GLintptr
> > _mesa_image_offset( GLuint dimensions,
> > --
> > 1.9.1
> >
> > _______________________________________________
> > mesa-dev mailing list
> > mesa-dev@lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/mesa-dev
> >
> >
>
>
>
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