100 lines
1.7 KiB
C
100 lines
1.7 KiB
C
/*
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rnd.c
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Generate random numbers
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*/
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#define _POSIX_SOURCE
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#include <stdarg.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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static char *progname;
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static void fatal(char *fmt, ...);
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static void usage(void);
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int main(int argc, char *argv[])
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{
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int c, i, count;
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unsigned long n, v, high, modulus;
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unsigned seed;
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char *check;
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char *c_arg, *m_arg, *s_arg;
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(progname=strrchr(argv[0],'/')) ? progname++ : (progname=argv[0]);
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c_arg= m_arg= s_arg= NULL;
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while (c= getopt(argc, argv, "?c:m:s:"), c != -1)
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{
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switch(c)
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{
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case 'c': c_arg= optarg; break;
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case 'm': m_arg= optarg; break;
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case 's': s_arg= optarg; break;
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default:
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fatal("getopt failed: '%c'", c);
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}
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}
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if (optind != argc)
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usage();
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if (c_arg)
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{
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count= strtol(c_arg, &check, 0);
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if (check[0] != '\0')
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fatal("bad count '%s'", c_arg);
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}
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else
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count= 1;
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if (m_arg)
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{
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modulus= strtoul(m_arg, &check, 0);
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if (check[0] != '\0' || modulus == 0)
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fatal("bad modulus '%s'", m_arg);
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n= 0x80000000UL / modulus;
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if (n == 0)
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fatal("bad modulus %lu (too big)", modulus);
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high= n * modulus;
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}
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else
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modulus= high= 0x80000000UL;
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if (s_arg)
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{
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seed= strtol(s_arg, &check, 0);
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if (check[0] != '\0')
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fatal("bad seed '%s'", s_arg);
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srandom(seed);
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}
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for (i= 0; i<count; i++)
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{
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do
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{
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v= random();
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} while (v > high);
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printf("%lu\n", v % modulus);
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}
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}
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static void fatal(char *fmt, ...)
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{
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va_list ap;
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fprintf(stderr, "%s: ", progname);
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va_start(ap, fmt);
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vfprintf(stderr, fmt, ap);
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va_end(ap);
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fprintf(stderr, "\n");
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exit(1);
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}
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static void usage(void)
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{
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fprintf(stderr, "Usage: rnd [-c <count>] [-m <modulus>] [-s <seed>]\n");
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exit(1);
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}
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