ru_bits
p->ru_seed = arc4random() & (~0U >> (32 - p->ru_bits + 1));
p->ru_seed2 = arc4random() & (~0U >> (32 - p->ru_bits + 1));
p->ru_b = (arc4random() & (~0U >> (32 - p->ru_bits))) | 1;
(arc4random() & (~0U >> (32 - p->ru_bits))) & (~1U), p->ru_m);
p->ru_msb = p->ru_msb ? 0 : (1U << (p->ru_bits - 1));