[Cogl] [PATCH 1/5] Use ffs to calculate the GL_{UN, }PACK_ALIGNMENT

[Robert Bragg]

Reviewed-by: Robert Bragg <robert at linux.intel.com>

On Tue, Mar 27, 2012 at 5:56 PM, Neil Roberts <neil at linux.intel.com> wrote:
> Instead of having a series of if-statements this adds an inline
> function to calculate the alignment directly using ffs which is
> probably slightly faster. Admittedly this is a pointless
> micro-optimisation but I think it makes the code looks a bit neater
> anyway.
> ---
>  cogl/cogl-texture.c |   28 ++++++++++++----------------
>  1 files changed, 12 insertions(+), 16 deletions(-)
>
> diff --git a/cogl/cogl-texture.c b/cogl/cogl-texture.c
> index ab07f91..df4fdcc 100644
> --- a/cogl/cogl-texture.c
> +++ b/cogl/cogl-texture.c
> @@ -255,19 +255,21 @@ _cogl_texture_prepare_for_upload (CoglBitmap      *src_bmp,
>   return dst_bmp;
>  }
>
> +static inline int
> +calculate_alignment (int rowstride)
> +{
> +  int alignment = 1 << (_cogl_util_ffs (rowstride) - 1);
> +
> +  return MIN (alignment, 8);
> +}
> +
>  void
>  _cogl_texture_prep_gl_alignment_for_pixels_upload (int pixels_rowstride)
>  {
>   _COGL_GET_CONTEXT (ctx, NO_RETVAL);
>
> -  if (!(pixels_rowstride & 0x7))
> -    GE( ctx, glPixelStorei (GL_UNPACK_ALIGNMENT, 8) );
> -  else if (!(pixels_rowstride & 0x3))
> -    GE( ctx, glPixelStorei (GL_UNPACK_ALIGNMENT, 4) );
> -  else if (!(pixels_rowstride & 0x1))
> -    GE( ctx, glPixelStorei (GL_UNPACK_ALIGNMENT, 2) );
> -  else
> -    GE( ctx, glPixelStorei (GL_UNPACK_ALIGNMENT, 1) );
> +  GE( ctx, glPixelStorei (GL_UNPACK_ALIGNMENT,
> +                          calculate_alignment (pixels_rowstride)) );
>  }
>
>  void
> @@ -275,14 +277,8 @@ _cogl_texture_prep_gl_alignment_for_pixels_download (int pixels_rowstride)
>  {
>   _COGL_GET_CONTEXT (ctx, NO_RETVAL);
>
> -  if (!(pixels_rowstride & 0x7))
> -    GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT, 8) );
> -  else if (!(pixels_rowstride & 0x3))
> -    GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT, 4) );
> -  else if (!(pixels_rowstride & 0x1))
> -    GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT, 2) );
> -  else
> -    GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT, 1) );
> +  GE( ctx, glPixelStorei (GL_PACK_ALIGNMENT,
> +                          calculate_alignment (pixels_rowstride)) );
>  }
>
>  /* FIXME: wrap modes should be set on pipelines not textures */
> --
> 1.7.3.16.g9464b
>
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