forked from freifunk-franken/firmware
84 lines
1.9 KiB
C
84 lines
1.9 KiB
C
// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Simple random tool, used to get a random value
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* 2017-07-02
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* Tim Niemeyer
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <errno.h>
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static int parse_int(char *str) {
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char *endptr = NULL;
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errno = 0;
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long val = strtol(str, &endptr, 10);
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if (errno != 0) {
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perror("strtol");
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exit(EXIT_FAILURE);
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}
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if (endptr == str) {
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fprintf(stderr, "No digits were found\n");
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exit(EXIT_FAILURE);
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}
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if (*endptr != '\0') {
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fprintf(stderr, "Further characters were found after number: \"%s\"\n", endptr);
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exit(EXIT_FAILURE);
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}
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int retVal = (int) val;
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if (val != retVal) {
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fprintf(stderr, "Given number is out of range\n");
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exit(EXIT_FAILURE);
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}
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return retVal;
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}
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int main(int argc, char **argv)
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{
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int from = 0;
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int to = 100;
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int diff = 1;
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FILE *f = 0;
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unsigned int r = 0;
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if (argc != 1 && argc != 3)
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{
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fprintf(stderr, "%s <from> <to>\n", argv[0]);
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return -1;
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}
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else if (argc == 3)
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{
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from = parse_int(argv[1]);
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to = parse_int(argv[2]);
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}
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diff = to - from;
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if (diff <= 0)
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{
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fprintf(stderr, "Bad from/to\n");
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return -1;
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}
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f = fopen("/dev/urandom", "r");
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if (!f)
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{
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fprintf(stderr, "Can't open /dev/urandom\n");
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return -1;
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}
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if (1U != fread(&r, sizeof(unsigned int), 1U, f))
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{
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fprintf(stderr, "Can't read /dev/urandom\n");
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fclose(f);
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return -1;
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}
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printf("%u\n", (r % (diff +1 )) + from);
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fclose(f);
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return 0;
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}
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