1 #include <stdlib.h>
2 #include <stdint.h>
3 #include "lock.h"
4
5 /*
6 this code uses the same lagged fibonacci generator as the
7 original bsd random implementation except for the seeding
8 which was broken in the original
9 */
10
11 static uint32_t init[] = {
12 0x00000000,0x5851f42d,0xc0b18ccf,0xcbb5f646,
13 0xc7033129,0x30705b04,0x20fd5db4,0x9a8b7f78,
14 0x502959d8,0xab894868,0x6c0356a7,0x88cdb7ff,
15 0xb477d43f,0x70a3a52b,0xa8e4baf1,0xfd8341fc,
16 0x8ae16fd9,0x742d2f7a,0x0d1f0796,0x76035e09,
17 0x40f7702c,0x6fa72ca5,0xaaa84157,0x58a0df74,
18 0xc74a0364,0xae533cc4,0x04185faf,0x6de3b115,
19 0x0cab8628,0xf043bfa4,0x398150e9,0x37521657};
20
21 static int n = 31;
22 static int i = 3;
23 static int j = 0;
24 static uint32_t *x = init+1;
25 static volatile int lock[1];
26
lcg31(uint32_t x)27 static uint32_t lcg31(uint32_t x) {
28 return (1103515245*x + 12345) & 0x7fffffff;
29 }
30
lcg64(uint64_t x)31 static uint64_t lcg64(uint64_t x) {
32 return 6364136223846793005ull*x + 1;
33 }
34
savestate()35 static void *savestate() {
36 x[-1] = (n<<16)|(i<<8)|j;
37 return x-1;
38 }
39
loadstate(uint32_t * state)40 static void loadstate(uint32_t *state) {
41 x = state+1;
42 n = x[-1]>>16;
43 i = (x[-1]>>8)&0xff;
44 j = x[-1]&0xff;
45 }
46
__srandom(unsigned seed)47 static void __srandom(unsigned seed) {
48 int k;
49 uint64_t s = seed;
50
51 if (n == 0) {
52 x[0] = s;
53 return;
54 }
55 i = n == 31 || n == 7 ? 3 : 1;
56 j = 0;
57 for (k = 0; k < n; k++) {
58 s = lcg64(s);
59 x[k] = s>>32;
60 }
61 /* make sure x contains at least one odd number */
62 x[0] |= 1;
63 }
64
srandom(unsigned seed)65 void srandom(unsigned seed) {
66 LOCK(lock);
67 __srandom(seed);
68 UNLOCK(lock);
69 }
70
initstate(unsigned seed,char * state,size_t size)71 char *initstate(unsigned seed, char *state, size_t size) {
72 void *old;
73
74 if (size < 8)
75 return 0;
76 LOCK(lock);
77 old = savestate();
78 if (size < 32)
79 n = 0;
80 else if (size < 64)
81 n = 7;
82 else if (size < 128)
83 n = 15;
84 else if (size < 256)
85 n = 31;
86 else
87 n = 63;
88 x = (uint32_t*)state + 1;
89 __srandom(seed);
90 savestate();
91 UNLOCK(lock);
92 return old;
93 }
94
setstate(char * state)95 char *setstate(char *state) {
96 void *old;
97
98 LOCK(lock);
99 old = savestate();
100 loadstate((uint32_t*)state);
101 UNLOCK(lock);
102 return old;
103 }
104
random(void)105 long random(void) {
106 long k;
107
108 LOCK(lock);
109 if (n == 0) {
110 k = x[0] = lcg31(x[0]);
111 goto end;
112 }
113 x[i] += x[j];
114 k = x[i]>>1;
115 if (++i == n)
116 i = 0;
117 if (++j == n)
118 j = 0;
119 end:
120 UNLOCK(lock);
121 return k;
122 }
123