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      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 
     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 
     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