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