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/*-
* Copyright (c) 1990, 1993
* The Regents of the University of California. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by the University of
* California, Berkeley and its contributors.
* 4. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*
* Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>.
*
* $FreeBSD$
*/
#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93";
#endif /* LIBC_SCCS and not lint */
#include <sys/time.h> /* for sranddev() */
#include <sys/types.h>
#include <fcntl.h> /* for sranddev() */
#include <stdlib.h>
#include <unistd.h> /* for sranddev() */
#ifdef TEST
#include <stdio.h>
#endif /* TEST */
static int
do_rand(unsigned long *ctx)
{
#ifdef USE_WEAK_SEEDING
/*
* Historic implementation compatibility.
* The random sequences do not vary much with the seed,
* even with overflowing.
*/
return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));
#else /* !USE_WEAK_SEEDING */
/*
* Compute x = (7^5 * x) mod (2^31 - 1)
* wihout overflowing 31 bits:
* (2^31 - 1) = 127773 * (7^5) + 2836
* From "Random number generators: good ones are hard to find",
* Park and Miller, Communications of the ACM, vol. 31, no. 10,
* October 1988, p. 1195.
*/
long hi, lo, x;
hi = *ctx / 127773;
lo = *ctx % 127773;
x = 16807 * lo - 2836 * hi;
if (x <= 0)
x += 0x7fffffff;
return ((*ctx = x) % ((u_long)RAND_MAX + 1));
#endif /* !USE_WEAK_SEEDING */
}
int
rand_r(unsigned int *ctx)
{
u_long val = (u_long) *ctx;
*ctx = do_rand(&val);
return (int) *ctx;
}
static u_long next = 1;
int
rand()
{
return do_rand(&next);
}
void
srand(seed)
u_int seed;
{
next = seed;
}
/*
* sranddev:
*
* Many programs choose the seed value in a totally predictable manner.
* This often causes problems. We seed the generator using the much more
* secure urandom(4) interface.
*/
void
sranddev()
{
int fd, done;
done = 0;
fd = _open("/dev/urandom", O_RDONLY, 0);
if (fd >= 0) {
if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next))
done = 1;
_close(fd);
}
if (!done) {
struct timeval tv;
unsigned long junk;
gettimeofday(&tv, NULL);
next = (getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk;
}
}
#ifdef TEST
main()
{
int i;
unsigned myseed;
printf("seeding rand with 0x19610910: \n");
srand(0x19610910);
printf("generating three pseudo-random numbers:\n");
for (i = 0; i < 3; i++)
{
printf("next random number = %d\n", rand());
}
printf("generating the same sequence with rand_r:\n");
myseed = 0x19610910;
for (i = 0; i < 3; i++)
{
printf("next random number = %d\n", rand_r(&myseed));
}
return 0;
}
#endif /* TEST */
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