1#include <stdlib.h>
  2#include <stdint.h>
  3#include "lock.h"
  4#include "fork_impl.h"
  5
  6/*
  7this code uses the same lagged fibonacci generator as the
  8original bsd random implementation except for the seeding
  9which was broken in the original
 10*/
 11
 12static uint32_t init[] = {
 130x00000000,0x5851f42d,0xc0b18ccf,0xcbb5f646,
 140xc7033129,0x30705b04,0x20fd5db4,0x9a8b7f78,
 150x502959d8,0xab894868,0x6c0356a7,0x88cdb7ff,
 160xb477d43f,0x70a3a52b,0xa8e4baf1,0xfd8341fc,
 170x8ae16fd9,0x742d2f7a,0x0d1f0796,0x76035e09,
 180x40f7702c,0x6fa72ca5,0xaaa84157,0x58a0df74,
 190xc74a0364,0xae533cc4,0x04185faf,0x6de3b115,
 200x0cab8628,0xf043bfa4,0x398150e9,0x37521657};
 21
 22static int n = 31;
 23static int i = 3;
 24static int j = 0;
 25static uint32_t *x = init+1;
 26static volatile int lock[1];
 27volatile int *const __random_lockptr = lock;
 28
 29static uint32_t lcg31(uint32_t x) {
 30	return (1103515245*x + 12345) & 0x7fffffff;
 31}
 32
 33static uint64_t lcg64(uint64_t x) {
 34	return 6364136223846793005ull*x + 1;
 35}
 36
 37static void *savestate() {
 38	x[-1] = (n<<16)|(i<<8)|j;
 39	return x-1;
 40}
 41
 42static void loadstate(uint32_t *state) {
 43	x = state+1;
 44	n = x[-1]>>16;
 45	i = (x[-1]>>8)&0xff;
 46	j = x[-1]&0xff;
 47}
 48
 49static void __srandom(unsigned seed) {
 50	int k;
 51	uint64_t s = seed;
 52
 53	if (n == 0) {
 54		x[0] = s;
 55		return;
 56	}
 57	i = n == 31 || n == 7 ? 3 : 1;
 58	j = 0;
 59	for (k = 0; k < n; k++) {
 60		s = lcg64(s);
 61		x[k] = s>>32;
 62	}
 63	/* make sure x contains at least one odd number */
 64	x[0] |= 1;
 65}
 66
 67void srandom(unsigned seed) {
 68	LOCK(lock);
 69	__srandom(seed);
 70	UNLOCK(lock);
 71}
 72
 73char *initstate(unsigned seed, char *state, size_t size) {
 74	void *old;
 75
 76	if (size < 8)
 77		return 0;
 78	LOCK(lock);
 79	old = savestate();
 80	if (size < 32)
 81		n = 0;
 82	else if (size < 64)
 83		n = 7;
 84	else if (size < 128)
 85		n = 15;
 86	else if (size < 256)
 87		n = 31;
 88	else
 89		n = 63;
 90	x = (uint32_t*)state + 1;
 91	__srandom(seed);
 92	savestate();
 93	UNLOCK(lock);
 94	return old;
 95}
 96
 97char *setstate(char *state) {
 98	void *old;
 99
100	LOCK(lock);
101	old = savestate();
102	loadstate((uint32_t*)state);
103	UNLOCK(lock);
104	return old;
105}
106
107long random(void) {
108	long k;
109
110	LOCK(lock);
111	if (n == 0) {
112		k = x[0] = lcg31(x[0]);
113		goto end;
114	}
115	x[i] += x[j];
116	k = x[i]>>1;
117	if (++i == n)
118		i = 0;
119	if (++j == n)
120		j = 0;
121end:
122	UNLOCK(lock);
123	return k;
124}