1/*- 2 * Copyright (c) 1990, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>. 34 *
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35 * $FreeBSD: head/lib/libc/stdlib/rand.c 75845 2001-04-23 02:29:10Z ache $
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35 * $FreeBSD: head/lib/libc/stdlib/rand.c 75862 2001-04-23 10:14:28Z ache $ |
36 */ 37 38#if defined(LIBC_SCCS) && !defined(lint) 39static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93"; 40#endif /* LIBC_SCCS and not lint */ 41 42#include <sys/time.h> /* for sranddev() */ 43#include <sys/types.h> 44#include <fcntl.h> /* for sranddev() */ 45#include <stdlib.h> 46#include <unistd.h> /* for sranddev() */ 47 48#ifdef TEST 49#include <stdio.h> 50#endif /* TEST */ 51 52static int 53do_rand(unsigned long *ctx) 54{ 55#ifdef USE_WEAK_SEEDING 56/* 57 * Historic implementation compatibility. 58 * The random sequences do not vary much with the seed, 59 * even with overflowing. 60 */ 61 return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1)); 62#else /* !USE_WEAK_SEEDING */ 63/* 64 * Compute x = (7^5 * x) mod (2^31 - 1) 65 * wihout overflowing 31 bits: 66 * (2^31 - 1) = 127773 * (7^5) + 2836 67 * From "Random number generators: good ones are hard to find", 68 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 69 * October 1988, p. 1195. 70 */ 71 long hi, lo, x; 72 73 hi = *ctx / 127773; 74 lo = *ctx % 127773; 75 x = 16807 * lo - 2836 * hi; 76 if (x <= 0) 77 x += 0x7fffffff; 78 return ((*ctx = x) % ((u_long)RAND_MAX + 1)); 79#endif /* !USE_WEAK_SEEDING */ 80} 81 82 83int 84rand_r(unsigned int *ctx) 85{ 86 u_long val = (u_long) *ctx; 87 *ctx = do_rand(&val); 88 return (int) *ctx; 89} 90 91 92static u_long next = 1; 93 94int 95rand() 96{ 97 return do_rand(&next); 98} 99 100void 101srand(seed) 102u_int seed; 103{ 104 next = seed; 105} 106 107 108/* 109 * sranddev: 110 * 111 * Many programs choose the seed value in a totally predictable manner. 112 * This often causes problems. We seed the generator using the much more 113 * secure urandom(4) interface. 114 */ 115void 116sranddev() 117{ 118 int fd, done; 119 120 done = 0; 121 fd = _open("/dev/urandom", O_RDONLY, 0); 122 if (fd >= 0) { 123 if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next)) 124 done = 1; 125 _close(fd); 126 } 127 128 if (!done) { 129 struct timeval tv; 130 unsigned long junk; 131 132 gettimeofday(&tv, NULL);
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133 next = getpid() ^ tv.tv_sec ^ tv.tv_usec ^ junk;
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133 next = (getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk; |
134 } 135} 136 137 138#ifdef TEST 139 140main() 141{ 142 int i; 143 unsigned myseed; 144 145 printf("seeding rand with 0x19610910: \n"); 146 srand(0x19610910); 147 148 printf("generating three pseudo-random numbers:\n"); 149 for (i = 0; i < 3; i++) 150 { 151 printf("next random number = %d\n", rand()); 152 } 153 154 printf("generating the same sequence with rand_r:\n"); 155 myseed = 0x19610910; 156 for (i = 0; i < 3; i++) 157 { 158 printf("next random number = %d\n", rand_r(&myseed)); 159 } 160 161 return 0; 162} 163 164#endif /* TEST */ 165
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