1 /**
2 * collectd - src/utils_random.c
3 * Copyright (C) 2013 Florian Forster
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be included in
13 * all copies or substantial portions of the 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 THE
18 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
19 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
20 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
21 * DEALINGS IN THE SOFTWARE.
22 *
23 * Authors:
24 * Florian Forster <octo at collectd.org>
25 **/
27 #include "collectd.h"
29 #include "utils_time.h"
30 #include "utils_random.h"
32 #include <pthread.h>
35 static pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
36 static _Bool have_seed = 0;
37 static unsigned short seed[3];
39 static void cdrand_seed (void)
40 {
41 cdtime_t t;
43 if (have_seed)
44 return;
46 t = cdtime();
48 seed[0] = (unsigned short) t;
49 seed[1] = (unsigned short) (t >> 16);
50 seed[2] = (unsigned short) (t >> 32);
52 have_seed = 1;
53 }
55 double cdrand_d (void)
56 {
57 double r;
59 pthread_mutex_lock (&lock);
60 cdrand_seed ();
61 r = erand48 (seed);
62 pthread_mutex_unlock (&lock);
64 return (r);
65 }
67 long cdrand_range (long min, long max)
68 {
69 long range;
70 long r;
72 range = 1 + max - min;
74 r = (long) (0.5 + (cdrand_d () * range));
75 r += min;
77 return (r);
78 }