c62ff2800b
It serves no useful purpose and wasn't as popular as its equally meritless cousin, srandomdev(3). Setting aside the problems with rand(3) in general, the problem with this interface is that the seed isn't shared with the caller (other than by attacking the output of the generator, which is trivial, but not a hallmark of pleasant API design). The (arguable) utility of rand(3) or random(3) is as a semi-fast simulation generator which produces consistent results from a given seed. These are mutually at odd. Furthermore, sometimes people got the mistaken impression that a high quality random seed meant a weak generator like rand(3) or random(3) could be used for things like cryptographic key generation. This is absolutely not so. The API was never part of a standard and was not widely used in tree. Existing in-tree uses have all been removed. Possible replacement in out of tree codebases: char buf[3]; time_t t; time(t); strftime(buf, sizeof(buf), "%S", gmtime(&t)); srand(atoi(buf)); Relnotes: yes
149 lines
3.6 KiB
C
149 lines
3.6 KiB
C
/*-
|
|
* SPDX-License-Identifier: BSD-3-Clause
|
|
*
|
|
* 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. 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>.
|
|
*/
|
|
|
|
#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/cdefs.h>
|
|
__FBSDID("$FreeBSD$");
|
|
|
|
#include "namespace.h"
|
|
#include <sys/param.h>
|
|
#include <sys/sysctl.h>
|
|
#include <stdbool.h>
|
|
#include <stdlib.h>
|
|
#include <syslog.h>
|
|
#include "un-namespace.h"
|
|
|
|
#ifdef TEST
|
|
#include <stdio.h>
|
|
#endif /* TEST */
|
|
|
|
static int
|
|
do_rand(unsigned long *ctx)
|
|
{
|
|
/*
|
|
* Compute x = (7^5 * x) mod (2^31 - 1)
|
|
* without 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;
|
|
|
|
/* Transform to [1, 0x7ffffffe] range. */
|
|
x = (*ctx % 0x7ffffffe) + 1;
|
|
hi = x / 127773;
|
|
lo = x % 127773;
|
|
x = 16807 * lo - 2836 * hi;
|
|
if (x < 0)
|
|
x += 0x7fffffff;
|
|
/* Transform to [0, 0x7ffffffd] range. */
|
|
x--;
|
|
*ctx = x;
|
|
return (x);
|
|
}
|
|
|
|
|
|
int
|
|
rand_r(unsigned *ctx)
|
|
{
|
|
u_long val;
|
|
int r;
|
|
|
|
val = *ctx;
|
|
r = do_rand(&val);
|
|
*ctx = (unsigned)val;
|
|
return (r);
|
|
}
|
|
|
|
|
|
static u_long next = 1;
|
|
|
|
int
|
|
rand(void)
|
|
{
|
|
return (do_rand(&next));
|
|
}
|
|
|
|
void
|
|
srand(unsigned seed)
|
|
{
|
|
next = seed;
|
|
}
|
|
|
|
|
|
void __sranddev_fbsd12(void);
|
|
void
|
|
__sranddev_fbsd12(void)
|
|
{
|
|
static bool warned = false;
|
|
|
|
if (!warned) {
|
|
syslog(LOG_DEBUG, "Deprecated function sranddev() called");
|
|
warned = true;
|
|
}
|
|
}
|
|
__sym_compat(sranddev, __sranddev_fbsd12, FBSD_1.0);
|
|
|
|
|
|
#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 */
|
|
|