projects/pwm

view rand-dev-random.c @ 26:5bdea77d0c1d

Add pwm-clip utility for setting the X11 CLIPBOARD selection
author Guido Berhoerster <guido+pwm@berhoerster.name>
date Thu Sep 21 09:45:59 2017 +0200 (2017-09-21)
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1 /*
2 * Copyright (C) 2017 Guido Berhoerster <guido+pwm@berhoerster.name>
3 *
4 * Permission is hereby granted, free of charge, to any person obtaining
5 * a copy of this software and associated documentation files (the
6 * "Software"), to deal in the Software without restriction, including
7 * without limitation the rights to use, copy, modify, merge, publish,
8 * distribute, sublicense, and/or sell copies of the Software, and to
9 * permit persons to whom the Software is furnished to do so, subject to
10 * the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included
13 * in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
18 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
19 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
20 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
21 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
22 */
24 #include "compat.h"
26 #ifdef HAVE_ERR_H
27 #include <err.h>
28 #endif /* HAVE_ERR_H */
29 #include <errno.h>
30 #include <fcntl.h>
31 #include <sys/stat.h>
32 #include <unistd.h>
34 #include "rand.h"
36 #ifdef __linux__
37 #define PATH_DEV_RANDOM "/dev/urandom"
38 #else
39 #define PATH_DEV_RANDOM "/dev/random"
40 #endif /* __linux__ */
42 void
43 rand_buf(void *buf, size_t buf_size)
44 {
45 unsigned char *p = buf;
46 int fd;
47 ssize_t nread;
48 size_t nsize = buf_size;
50 do {
51 fd = open(PATH_DEV_RANDOM, O_RDONLY);
52 } while ((fd < 0) && (errno == EINTR));
53 if (fd < 0) {
54 err(1, "open");
55 }
57 while (nsize > 0) {
58 nread = read(fd, p, nsize);
59 if (nread < 0) {
60 if (errno == EINTR) {
61 continue;
62 }
63 err(1, "read");
64 }
65 p += nread;
66 nsize -= nread;
67 }
69 while ((close(fd) < 0) && (errno == EINTR));
70 }
72 uint32_t
73 rand_random(void)
74 {
75 uint32_t x;
77 rand_buf(&x, sizeof (x));
79 return (x);
80 }
82 /* random number between 0 and upper_bound - 1 without modulo bias */
83 uint32_t
84 rand_uniform(uint32_t upper_bound)
85 {
86 uint32_t r;
87 /* (2^32 - upper_bound) % upper_bound */
88 uint32_t threshold = -upper_bound % upper_bound;
90 do {
91 r = rand_random();
92 } while (r < threshold);
94 return (r % upper_bound);
95 }