ref: c5393d612fd2a0e4ff3f9557dcb6adb2ad27391f
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; }