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 * 35 * $FreeBSD$ 36 */ 37 38 #if defined(LIBC_SCCS) && !defined(lint) 39 static 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 #include "un-namespace.h" 48 49 #ifdef TEST 50 #include <stdio.h> 51 #endif /* TEST */ 52 53 static int 54 do_rand(unsigned long *ctx) 55 { 56 #ifdef USE_WEAK_SEEDING 57 /* 58 * Historic implementation compatibility. 59 * The random sequences do not vary much with the seed, 60 * even with overflowing. 61 */ 62 return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1)); 63 #else /* !USE_WEAK_SEEDING */ 64 /* 65 * Compute x = (7^5 * x) mod (2^31 - 1) 66 * wihout overflowing 31 bits: 67 * (2^31 - 1) = 127773 * (7^5) + 2836 68 * From "Random number generators: good ones are hard to find", 69 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 70 * October 1988, p. 1195. 71 */ 72 long hi, lo, x; 73 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 *ctx = do_rand(&val); 89 return (int) *ctx; 90 } 91 92 93 static u_long next = 1; 94 95 int 96 rand() 97 { 98 return do_rand(&next); 99 } 100 101 void 102 srand(seed) 103 u_int seed; 104 { 105 next = seed; 106 } 107 108 109 /* 110 * sranddev: 111 * 112 * Many programs choose the seed value in a totally predictable manner. 113 * This often causes problems. We seed the generator using the much more 114 * secure random(4) interface. 115 */ 116 void 117 sranddev() 118 { 119 int fd, done; 120 121 done = 0; 122 fd = _open("/dev/random", O_RDONLY, 0); 123 if (fd >= 0) { 124 if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next)) 125 done = 1; 126 _close(fd); 127 } 128 129 if (!done) { 130 struct timeval tv; 131 unsigned long junk; 132 133 gettimeofday(&tv, NULL); 134 next = (getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk; 135 } 136 } 137 138 139 #ifdef TEST 140 141 main() 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