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}