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https://codeberg.org/grunfink/snac2.git
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87 lines
1.8 KiB
C
87 lines
1.8 KiB
C
/* copyright (c) 2022 - 2024 grunfink et al. / MIT license */
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#ifndef _XS_RANDOM_H
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#define _XS_RANDOM_H
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unsigned int xs_rnd_int32_d(unsigned int *seed);
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void *xs_rnd_buf(void *buf, int size);
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#ifdef XS_IMPLEMENTATION
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#include <stdio.h>
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#include <sys/time.h>
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#include <unistd.h>
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#include <stdlib.h>
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unsigned int xs_rnd_int32_d(unsigned int *seed)
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/* returns a deterministic random integer. If seed is NULL, uses a static one */
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{
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static unsigned int s = 0;
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if (seed == NULL)
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seed = &s;
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if (*seed == 0) {
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struct timeval tv;
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gettimeofday(&tv, NULL);
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*seed = tv.tv_sec ^ tv.tv_usec ^ getpid();
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}
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/* Linear congruential generator by Numerical Recipes */
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*seed = (*seed * 1664525) + 1013904223;
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return *seed;
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}
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void *xs_rnd_buf(void *buf, int size)
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/* fills buf with random data */
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{
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#ifdef __OpenBSD__
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/* available since OpenBSD 2.2 */
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arc4random_buf(buf, size);
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#else
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FILE *f;
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int done = 0;
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if ((f = fopen("/dev/urandom", "r")) != NULL) {
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/* fill with great random data from the system */
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if (fread(buf, size, 1, f) == 1)
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done = 1;
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fclose(f);
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}
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if (!done) {
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/* fill the buffer with poor quality, deterministic data */
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unsigned int s = 0;
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unsigned char *p = (unsigned char *)buf;
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int n = size / sizeof(s);
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/* fill with full integers */
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while (n--) {
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xs_rnd_int32_d(&s);
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p = memcpy(p, &s, sizeof(s)) + sizeof(s);
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}
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if ((n = size % sizeof(s))) {
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/* fill the remaining */
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xs_rnd_int32_d(&s);
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memcpy(p, &s, n);
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}
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}
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#endif /* __OpenBSD__ */
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return buf;
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}
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#endif /* XS_IMPLEMENTATION */
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#endif /* XS_RANDOM_H */
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