ref: ec73849b6936d839410ccb239d14b2f7c7ca3d6f
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; }