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. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * Posix rand_r function added May 1999 by Wes Peters <wes@softweyr.com>. 30 * 31 * @(#)rand.c 8.1 (Berkeley) 6/14/93 32 * $FreeBSD: src/lib/libc/stdlib/rand.c,v 1.17 2007/12/11 20:39:32 ache Exp $ 33 * $DragonFly: src/lib/libc/stdlib/rand.c,v 1.6 2005/11/20 14:58:40 swildner Exp $ 34 */ 35 36 #include "namespace.h" 37 #include <sys/time.h> /* for sranddev() */ 38 #include <sys/types.h> 39 #include <fcntl.h> /* for sranddev() */ 40 #include <stdlib.h> 41 #include <unistd.h> /* for sranddev() */ 42 #include "un-namespace.h" 43 44 #ifdef TEST 45 #include <stdio.h> 46 #endif /* TEST */ 47 48 static int 49 do_rand(unsigned long *ctx) 50 { 51 #ifdef USE_WEAK_SEEDING 52 /* 53 * Historic implementation compatibility. 54 * The random sequences do not vary much with the seed, 55 * even with overflowing. 56 */ 57 return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1)); 58 #else /* !USE_WEAK_SEEDING */ 59 /* 60 * Compute x = (7^5 * x) mod (2^31 - 1) 61 * without overflowing 31 bits: 62 * (2^31 - 1) = 127773 * (7^5) + 2836 63 * From "Random number generators: good ones are hard to find", 64 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 65 * October 1988, p. 1195. 66 */ 67 long hi, lo, x; 68 69 /* Can't be initialized with 0, so use another value. */ 70 if (*ctx == 0) 71 *ctx = 123459876; 72 hi = *ctx / 127773; 73 lo = *ctx % 127773; 74 x = 16807 * lo - 2836 * hi; 75 if (x < 0) 76 x += 0x7fffffff; 77 return ((*ctx = x) % ((u_long)RAND_MAX + 1)); 78 #endif /* !USE_WEAK_SEEDING */ 79 } 80 81 82 int 83 rand_r(unsigned int *ctx) 84 { 85 u_long val = (u_long) *ctx; 86 int r = do_rand(&val); 87 88 *ctx = (unsigned int) val; 89 return (r); 90 } 91 92 93 static u_long next = 1; 94 95 int 96 rand(void) 97 { 98 return (do_rand(&next)); 99 } 100 101 void 102 srand(u_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 random(4) interface. 114 */ 115 void 116 sranddev(void) 117 { 118 int fd, done; 119 120 done = 0; 121 fd = _open("/dev/random", 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; /* XXX left uninitialized on purpose */ 131 132 gettimeofday(&tv, NULL); 133 srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk); 134 } 135 } 136 137 138 #ifdef TEST 139 140 int 141 main(int argc __unused, char *argv[] __unused) 142 { 143 int i; 144 unsigned myseed; 145 146 printf("seeding rand with 0x19610910: \n"); 147 srand(0x19610910); 148 149 printf("generating three pseudo-random numbers:\n"); 150 for (i = 0; i < 3; i++) 151 { 152 printf("next random number = %d\n", rand()); 153 } 154 155 printf("generating the same sequence with rand_r:\n"); 156 myseed = 0x19610910; 157 for (i = 0; i < 3; i++) 158 { 159 printf("next random number = %d\n", rand_r(&myseed)); 160 } 161 162 return 0; 163 } 164 165 #endif /* TEST */ 166 167