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;
 26#if defined(__wasilibc_unmodified_upstream) || defined(_REENTRANT)
 27static volatile int lock[1];
 28volatile int *const __random_lockptr = lock;
 29#endif
 30
 31static uint32_t lcg31(uint32_t x) {
 32	return (1103515245*x + 12345) & 0x7fffffff;
 33}
 34
 35static uint64_t lcg64(uint64_t x) {
 36	return 6364136223846793005ull*x + 1;
 37}
 38
 39static void *savestate() {
 40	x[-1] = (n<<16)|(i<<8)|j;
 41	return x-1;
 42}
 43
 44static void loadstate(uint32_t *state) {
 45	x = state+1;
 46	n = x[-1]>>16;
 47	i = (x[-1]>>8)&0xff;
 48	j = x[-1]&0xff;
 49}
 50
 51static void __srandom(unsigned seed) {
 52	int k;
 53	uint64_t s = seed;
 54
 55	if (n == 0) {
 56		x[0] = s;
 57		return;
 58	}
 59	i = n == 31 || n == 7 ? 3 : 1;
 60	j = 0;
 61	for (k = 0; k < n; k++) {
 62		s = lcg64(s);
 63		x[k] = s>>32;
 64	}
 65	/* make sure x contains at least one odd number */
 66	x[0] |= 1;
 67}
 68
 69void srandom(unsigned seed) {
 70	LOCK(lock);
 71	__srandom(seed);
 72	UNLOCK(lock);
 73}
 74
 75char *initstate(unsigned seed, char *state, size_t size) {
 76	void *old;
 77
 78	if (size < 8)
 79		return 0;
 80	LOCK(lock);
 81	old = savestate();
 82	if (size < 32)
 83		n = 0;
 84	else if (size < 64)
 85		n = 7;
 86	else if (size < 128)
 87		n = 15;
 88	else if (size < 256)
 89		n = 31;
 90	else
 91		n = 63;
 92	x = (uint32_t*)state + 1;
 93	__srandom(seed);
 94	savestate();
 95	UNLOCK(lock);
 96	return old;
 97}
 98
 99char *setstate(char *state) {
100	void *old;
101
102	LOCK(lock);
103	old = savestate();
104	loadstate((uint32_t*)state);
105	UNLOCK(lock);
106	return old;
107}
108
109long random(void) {
110	long k;
111
112	LOCK(lock);
113	if (n == 0) {
114		k = x[0] = lcg31(x[0]);
115		goto end;
116	}
117	x[i] += x[j];
118	k = x[i]>>1;
119	if (++i == n)
120		i = 0;
121	if (++j == n)
122		j = 0;
123end:
124	UNLOCK(lock);
125	return k;
126}