snac2/xs_random.h
2024-01-04 09:22:03 +01:00

88 lines
1.8 KiB
C

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