Re: [AD] signed/unsigned issue ? geta32()

[Peter Wang <tjaden@xxxxxxxxxx>]

aj wrote:

> 32bit ARGB 8888 .. how can it work.. what happens to the MSB (bit 31)
>
> allegro docs:
> int geta32(int c);
>
> signed/unsigned issue ?


No issue.  The code is:

AL_INLINE(int, geta32, (int c),
{
  return ((c >> _rgb_a_shift_32) & 0xFF);
})

Let c = 0xfe123456, _rgb_a_shift_32 = 24.
(c >> _rgb_a_shift_32) = 0xfffffffe (assuming sign extension)
0xfffffffe & 0xFF = 0xfe

Peter