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 * 4. 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 32 #if defined(LIBC_SCCS) && !defined(lint) 33 static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93"; 34 #endif /* LIBC_SCCS and not lint */ 35 #include <sys/cdefs.h> 36 __FBSDID("$FreeBSD$"); 37 38 #include "namespace.h" 39 #include <sys/time.h> /* for sranddev() */ 40 #include <sys/types.h> 41 #include <fcntl.h> /* for sranddev() */ 42 #include <stdlib.h> 43 #include <unistd.h> /* for sranddev() */ 44 #include "un-namespace.h" 45 46 #ifdef TEST 47 #include <stdio.h> 48 #endif /* TEST */ 49 50 static int 51 do_rand(unsigned long *ctx) 52 { 53 #ifdef USE_WEAK_SEEDING 54 /* 55 * Historic implementation compatibility. 56 * The random sequences do not vary much with the seed, 57 * even with overflowing. 58 */ 59 return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1)); 60 #else /* !USE_WEAK_SEEDING */ 61 /* 62 * Compute x = (7^5 * x) mod (2^31 - 1) 63 * without overflowing 31 bits: 64 * (2^31 - 1) = 127773 * (7^5) + 2836 65 * From "Random number generators: good ones are hard to find", 66 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 67 * October 1988, p. 1195. 68 */ 69 long hi, lo, x; 70 71 /* Can't be initialized with 0, so use another value. */ 72 if (*ctx == 0) 73 *ctx = 123459876; 74 hi = *ctx / 127773; 75 lo = *ctx % 127773; 76 x = 16807 * lo - 2836 * hi; 77 if (x < 0) 78 x += 0x7fffffff; 79 return ((*ctx = x) % ((u_long)RAND_MAX + 1)); 80 #endif /* !USE_WEAK_SEEDING */ 81 } 82 83 84 int 85 rand_r(unsigned int *ctx) 86 { 87 u_long val = (u_long) *ctx; 88 int r = do_rand(&val); 89 90 *ctx = (unsigned int) val; 91 return (r); 92 } 93 94 95 static u_long next = 1; 96 97 int 98 rand() 99 { 100 return (do_rand(&next)); 101 } 102 103 void 104 srand(seed) 105 u_int seed; 106 { 107 next = seed; 108 } 109 110 111 /* 112 * sranddev: 113 * 114 * Many programs choose the seed value in a totally predictable manner. 115 * This often causes problems. We seed the generator using the much more 116 * secure random(4) interface. 117 */ 118 void 119 sranddev() 120 { 121 int fd, done; 122 123 done = 0; 124 fd = _open("/dev/random", O_RDONLY | O_CLOEXEC, 0); 125 if (fd >= 0) { 126 if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next)) 127 done = 1; 128 _close(fd); 129 } 130 131 if (!done) { 132 struct timeval tv; 133 134 gettimeofday(&tv, NULL); 135 srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec); 136 } 137 } 138 139 140 #ifdef TEST 141 142 main() 143 { 144 int i; 145 unsigned myseed; 146 147 printf("seeding rand with 0x19610910: \n"); 148 srand(0x19610910); 149 150 printf("generating three pseudo-random numbers:\n"); 151 for (i = 0; i < 3; i++) 152 { 153 printf("next random number = %d\n", rand()); 154 } 155 156 printf("generating the same sequence with rand_r:\n"); 157 myseed = 0x19610910; 158 for (i = 0; i < 3; i++) 159 { 160 printf("next random number = %d\n", rand_r(&myseed)); 161 } 162 163 return 0; 164 } 165 166 #endif /* TEST */ 167 168