ref: a9d09ee1f1eccc3d8cef3f6fe593f96bec8f855f
dir: /sys/src/ape/lib/bsd/ffs.c/
/* Find the first set bit
* i.e. least signifigant 1 bit:
* 0 => 0
* 1 => 1
* 2 => 2
* 3 => 1
* 4 => 3
*/
int
ffs(unsigned int mask)
{
int i;
if (!mask)
return 0;
i = 1;
while (!(mask & 1)){
i++;
mask = mask >> 1;
}
return i;
}