1 /* $NetBSD: rand_sleep.c,v 1.1.1.1 2009/06/23 10:09:00 tron Exp $ */
2
3 /*++
4 /* NAME
5 /* rand_sleep 3
6 /* SUMMARY
7 /* sleep for randomized interval
8 /* SYNOPSIS
9 /* #include <iostuff.h>
10 /*
11 /* void rand_sleep(delay, variation)
12 /* unsigned delay;
13 /* unsigned variation;
14 /* DESCRIPTION
15 /* rand_sleep() blocks the current process for an amount of time
16 /* pseudo-randomly chosen from the interval (delay +- variation/2).
17 /*
18 /* Arguments:
19 /* .IP delay
20 /* Time to sleep in microseconds.
21 /* .IP variation
22 /* Variation in microseconds; must not be larger than delay.
23 /* DIAGNOSTICS
24 /* Panic: interface violation. All system call errors are fatal.
25 /* LICENSE
26 /* .ad
27 /* .fi
28 /* The Secure Mailer license must be distributed with this software.
29 /* AUTHOR(S)
30 /* Wietse Venema
31 /* IBM T.J. Watson Research
32 /* P.O. Box 704
33 /* Yorktown Heights, NY 10598, USA
34 /*--*/
35
36 /* System library. */
37
38 #include <sys_defs.h>
39 #include <stdlib.h>
40 #include <unistd.h>
41 #include <time.h>
42
43 /* Utility library. */
44
45 #include <msg.h>
46 #include <myrand.h>
47 #include <iostuff.h>
48
49 /* rand_sleep - block for random time */
50
rand_sleep(unsigned delay,unsigned variation)51 void rand_sleep(unsigned delay, unsigned variation)
52 {
53 const char *myname = "rand_sleep";
54 unsigned usec;
55
56 /*
57 * Sanity checks.
58 */
59 if (delay == 0)
60 msg_panic("%s: bad delay %d", myname, delay);
61 if (variation > delay)
62 msg_panic("%s: bad variation %d", myname, variation);
63
64 /*
65 * Use the semi-crappy random number generator.
66 */
67 usec = (delay - variation / 2) + variation * (double) myrand() / RAND_MAX;
68 doze(usec);
69 }
70
71 #ifdef TEST
72
73 #include <msg_vstream.h>
74
main(int argc,char ** argv)75 int main(int argc, char **argv)
76 {
77 int delay;
78 int variation;
79
80 msg_vstream_init(argv[0], VSTREAM_ERR);
81 if (argc != 3)
82 msg_fatal("usage: %s delay variation", argv[0]);
83 if ((delay = atoi(argv[1])) <= 0)
84 msg_fatal("bad delay: %s", argv[1]);
85 if ((variation = atoi(argv[2])) < 0)
86 msg_fatal("bad variation: %s", argv[2]);
87 rand_sleep(delay * 1000000, variation * 1000000);
88 exit(0);
89 }
90
91 #endif
92