[Mesa-dev] [PATCH v3 3/8] mesa: glGet: simplify the 'enum not found' condition

[Oliver McFadden]

On Mon, Oct 01, 2012 at 01:38:00PM +0300, Imre Deak wrote:
> When traversing the hash table looking up an enum that is invalid we
> eventually reach the first element in the descriptor array. By looking
> at the type of that element, which is always TYPE_API_MASK, we know that
> we can stop the search and return error. Since this element is always
> the first it's enough to check for its index being 0 without looking at
> its type.
> 
> Later in this patchset, when we generate the hash tables during build
> time, this will allow us to remove the TYPE_API_MASK and related flags
> completly.
> 
> Signed-off-by: Imre Deak <imre.deak at intel.com>
> Reviewed-by: Brian Paul <brianp at vmware.com>
Reviewed-by: Oliver McFadden <oliver.mcfadden at linux.intel.com>
> ---
>  src/mesa/main/get.c |    8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/src/mesa/main/get.c b/src/mesa/main/get.c
> index b46492c..e09147b 100644
> --- a/src/mesa/main/get.c
> +++ b/src/mesa/main/get.c
> @@ -2004,16 +2004,18 @@ find_value(const char *func, GLenum pname, void **p, union value *v)
>     mask = Elements(table[api]) - 1;
>     hash = (pname * prime_factor);
>     while (1) {
> -      d = &values[table[api][hash & mask]];
> +      int idx = table[api][hash & mask];
>  
>        /* If the enum isn't valid, the hash walk ends with index 0,
> -       * which is the API mask entry at the beginning of values[]. */
> -      if (unlikely(d->type == TYPE_API_MASK)) {
> +       * pointing to the first entry of values[] which doesn't hold
> +       * any valid enum. */
> +      if (unlikely(idx == 0)) {
>           _mesa_error(ctx, GL_INVALID_ENUM, "%s(pname=%s)", func,
>                 _mesa_lookup_enum_by_nr(pname));
>           return &error_value;
>        }
>  
> +      d = &values[idx];
>        if (likely(d->pname == pname))
>           break;
>  
> -- 
> 1.7.9.5
> 

-- 
Oliver McFadden.