Re: WineD3D: better pixelformat selection code

[H. Verbeet]

On 09/08/07, Roderick Colenbrander  wrote:
> Hi,
>
> This code lets WineD3D use the pixelformat of the D3D device. The code helps
> on Windows where OpenGL offers multiple pixelformats.

The stencil column is probably useful for determining if we need an
stencil attachment for FBOs as well.
> +int count_bits(int mask)
> +{
> - int i, count=0;
> - for(i=0; i<32; i++)
> - {
> -
>    if(mask & (1<<i))
> -
>        count++;
> - }
> - return count;
>
> +}

The "classical" way to do that would be something like this:

unsigned int count_bits(unsigned int mask)
{
    unsigned int count;
    for (count = 0; mask; ++count)
    {
        mask &= mask - 1;
    }
    return count;
}

Ie, simply mask out the set bits one by one until none are set, rather
than looping over all of them.