external/ibm-public/postfix/dist/src/util/rand_sleep.c

   1 /*      $NetBSD$        */
   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