util/rand_xor: add missing include statements
[mesa.git] / src / util / rand_xor.c
1 /*
2 * Copyright 2017 Timothy Arceri
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining a
5 * copy of this software and associated documentation files (the "Software"),
6 * to deal in the Software without restriction, including without limitation
7 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
8 * and/or sell copies of the Software, and to permit persons to whom the
9 * Software is furnished to do so, subject to the following conditions:
10 *
11 * The above copyright notice and this permission notice (including the next
12 * paragraph) shall be included in all copies or substantial portions of the
13 * Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
16 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
17 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
18 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
20 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
21 * SOFTWARE.
22 *
23 */
24
25 #if defined(__linux__)
26 #include <sys/file.h>
27 #include <unistd.h>
28 #include <fcntl.h>
29 #else
30 #include <time.h>
31 #endif
32
33 #include "rand_xor.h"
34
35 /* Super fast random number generator.
36 *
37 * This rand_xorshift128plus function by Sebastiano Vigna belongs
38 * to the public domain.
39 */
40 uint64_t
41 rand_xorshift128plus(uint64_t *seed)
42 {
43 uint64_t *s = seed;
44
45 uint64_t s1 = s[0];
46 const uint64_t s0 = s[1];
47 s[0] = s0;
48 s1 ^= s1 << 23;
49 s[1] = s1 ^ s0 ^ (s1 >> 18) ^ (s0 >> 5);
50
51 return s[1] + s0;
52 }
53
54 void
55 s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed)
56 {
57 if (!randomised_seed)
58 goto fixed_seed;
59
60 #if defined(__linux__)
61 int fd = open("/dev/urandom", O_RDONLY);
62 if (fd < 0)
63 goto fixed_seed;
64
65 size_t seed_size = sizeof(uint64_t) * 2;
66 if (read(fd, seed, seed_size) != seed_size) {
67 close(fd);
68 goto fixed_seed;
69 }
70
71 close(fd);
72 return;
73
74 #else
75 seed[0] = 0x3bffb83978e24f88;
76 seed[1] = time(NULL);
77
78 return;
79 #endif
80
81 fixed_seed:
82
83 /* Fallback to a fixed seed */
84 seed[0] = 0x3bffb83978e24f88;
85 seed[1] = 0x9238d5d56c71cd35;
86 }