randutils.c

/*
 * General purpose random utilities
 *
 * Based on libuuid code.
 *
 * This file may be redistributed under the terms of the
 * GNU Lesser General Public License.
 */
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>

#if defined(HAVE_SYS_RANDOM_H)
#include <sys/random.h>
#endif

#if defined(HAVE_SYS_TIME_H)
#include <sys/time.h>
#endif

#if defined(__linux__) && defined(HAVE_SYS_SYSCALL_H)
#include <sys/syscall.h>
#endif

#include "randutils.h"

#ifdef HAVE_TLS
#define THREAD_LOCAL static __thread
#else
#define THREAD_LOCAL static
#endif

#if defined(__linux__) && defined(__NR_gettid) && defined(HAVE_JRAND48)
#define DO_JRAND_MIX
THREAD_LOCAL unsigned short ul_jrand_seed[3];
#endif

void random_get_bytes(void *buf, size_t nbytes)
{
#if defined(HAVE_SYS_RANDOM_H) && defined(HAVE_GETRANDOM)
	size_t n = 0;

	while (n != nbytes) {
		ssize_t r = getrandom((char *)buf + n, nbytes - n, 0);
		if (r < 0) {
			if (errno == EINTR || errno == EAGAIN)
				continue;
			break;
		}
		n += r;
	}
#else
	size_t i, n = nbytes;
	int lose_counter = 0;
	unsigned char *cp = (unsigned char *)buf;

	for (cp = buf, i = 0; i < nbytes; i++)
		*cp++ ^= (rand() >> 7) & 0xFF;

#ifdef DO_JRAND_MIX
	{
		unsigned short tmp_seed[3];

		memcpy(tmp_seed, ul_jrand_seed, sizeof(tmp_seed));
		ul_jrand_seed[2] = ul_jrand_seed[2] ^ syscall(__NR_gettid);
		for (cp = buf, i = 0; i < nbytes; i++)
			*cp++ ^= (jrand48(tmp_seed) >> 7) & 0xFF;
		memcpy(ul_jrand_seed, tmp_seed, sizeof(ul_jrand_seed) - sizeof(unsigned short));
	}
#endif
#endif
	return;
}

#ifdef TEST_PROGRAM
int main(int argc __attribute__((__unused__)), char *argv[] __attribute__((__unused__)))
{
	unsigned int v, i;

	/* generate and print 10 random numbers */
	for (i = 0; i < 10; i++) {
		random_get_bytes(&v, sizeof(v));
		printf("%d\n", v);
	}

	return EXIT_SUCCESS;
}
#endif /* TEST_PROGRAM */