commands/swifi/rnd.c

   1 /*
   2 rnd.c
   3
   4 Generate random numbers
   5 */
   6
   7 #define _POSIX_SOURCE
   8
   9 #include <stdarg.h>
  10 #include <stdio.h>
  11 #include <stdlib.h>
  12 #include <string.h>
  13 #include <unistd.h>
  14
  15 static char *progname;
  16
  17 static void fatal(char *fmt, ...);
  18 static void usage(void);
  19
  20 int main(int argc, char *argv[])
  21 {
  22         int c, i, count;
  23         unsigned long n, v, high, modulus;
  24         unsigned seed;
  25         char *check;
  26         char *c_arg, *m_arg, *s_arg;
  27
  28         (progname=strrchr(argv[0],'/')) ? progname++ : (progname=argv[0]);
  29
  30         c_arg= m_arg= s_arg= NULL;
  31         while (c= getopt(argc, argv, "?c:m:s:"), c != -1)
  32         {
  33                 switch(c)
  34                 {
  35                 case 'c': c_arg= optarg; break;
  36                 case 'm': m_arg= optarg; break;
  37                 case 's': s_arg= optarg; break;
  38                 default:
  39                         fatal("getopt failed: '%c'", c);
  40                 }
  41         }
  42         if (optind != argc)
  43                 usage();
  44         if (c_arg)
  45         {
  46                 count= strtol(c_arg, &check, 0);
  47                 if (check[0] != '\0')
  48                         fatal("bad count '%s'", c_arg);
  49         }
  50         else
  51                 count= 1;
  52         if (m_arg)
  53         {
  54                 modulus= strtoul(m_arg, &check, 0);
  55                 if (check[0] != '\0' || modulus == 0)
  56                         fatal("bad modulus '%s'", m_arg);
  57                 n= 0x80000000UL / modulus;
  58                 if (n == 0)
  59                         fatal("bad modulus %lu (too big)", modulus);
  60                 high= n * modulus;
  61         }
  62         else
  63                 modulus= high= 0x80000000UL;
  64         if (s_arg)
  65         {
  66                 seed= strtol(s_arg, &check, 0);
  67                 if (check[0] != '\0')
  68                         fatal("bad seed '%s'", s_arg);
  69                 srandom(seed);
  70         }
  71
  72         for (i= 0; i<count; i++)
  73         {
  74                 do
  75                 {
  76                         v= random();
  77                 } while (v > high);
  78
  79                 printf("%lu\n", v % modulus);
  80         }
  81 }
  82
  83 static void fatal(char *fmt, ...)
  84 {
  85         va_list ap;
  86
  87         fprintf(stderr, "%s: ", progname);
  88         va_start(ap, fmt);
  89         vfprintf(stderr, fmt, ap);
  90         va_end(ap);
  91         fprintf(stderr, "\n");
  92         exit(1);
  93 }
  94
  95 static void usage(void)
  96 {
  97         fprintf(stderr, "Usage: rnd [-c <count>] [-m <modulus>] [-s <seed>]\n");
  98         exit(1);
  99 }