xref: /openbsd-src/lib/libc/stdlib/rand.c (revision e34cb67ca6a03d6ed8f381b6dd30bd8428efd463)

/*	$OpenBSD: rand.c,v 1.18 2017/11/28 06:55:49 tb Exp $ */
/*-
 * Copyright (c) 1990 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.
 */

#include <sys/types.h>
#include <stdlib.h>

static int rand_deterministic;
static u_int next = 1;

int
rand_r(u_int *seed)
{
	*seed = *seed * 1103515245 + 12345;
	return (*seed & RAND_MAX);
}
DEF_WEAK(rand_r);

#if defined(APIWARN)
__warn_references(rand_r,
    "rand_r() is not random, it is deterministic.");
#endif

int
rand(void)
{
	if (rand_deterministic == 0)
		return (arc4random() & RAND_MAX);
	return (rand_r(&next));
}

#if defined(APIWARN)
__warn_references(rand,
    "rand() may return deterministic values, is that what you want?");
#endif

void
srand(u_int seed)
{
	rand_deterministic = 0;
}

void
srand_deterministic(u_int seed)
{
	rand_deterministic = 1;
	next = seed;
}