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 36 #if defined(LIBC_SCCS) && !defined(lint) 37 static char sccsid[] = "@(#)rand.c 8.1 (Berkeley) 6/14/93"; 38 #endif /* LIBC_SCCS and not lint */ 39 #include <sys/cdefs.h> 40 __FBSDID("$FreeBSD$"); 41 42 #include "namespace.h" 43 #include <sys/time.h> /* for sranddev() */ 44 #include <sys/types.h> 45 #include <fcntl.h> /* for sranddev() */ 46 #include <stdlib.h> 47 #include <unistd.h> /* for sranddev() */ 48 #include "un-namespace.h" 49 50 #ifdef TEST 51 #include <stdio.h> 52 #endif /* TEST */ 53 54 static int 55 do_rand(unsigned long *ctx) 56 { 57 #ifdef USE_WEAK_SEEDING 58 /* 59 * Historic implementation compatibility. 60 * The random sequences do not vary much with the seed, 61 * even with overflowing. 62 */ 63 return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1)); 64 #else /* !USE_WEAK_SEEDING */ 65 /* 66 * Compute x = (7^5 * x) mod (2^31 - 1) 67 * wihout overflowing 31 bits: 68 * (2^31 - 1) = 127773 * (7^5) + 2836 69 * From "Random number generators: good ones are hard to find", 70 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 71 * October 1988, p. 1195. 72 */ 73 long hi, lo, x; 74 75 hi = *ctx / 127773; 76 lo = *ctx % 127773; 77 x = 16807 * lo - 2836 * hi; 78 if (x <= 0) 79 x += 0x7fffffff; 80 return ((*ctx = x) % ((u_long)RAND_MAX + 1)); 81 #endif /* !USE_WEAK_SEEDING */ 82 } 83 84 85 int 86 rand_r(unsigned int *ctx) 87 { 88 u_long val = (u_long) *ctx; 89 *ctx = do_rand(&val); 90 return (int) *ctx; 91 } 92 93 94 static u_long next = 1; 95 96 int 97 rand() 98 { 99 return do_rand(&next); 100 } 101 102 void 103 srand(seed) 104 u_int seed; 105 { 106 next = seed; 107 } 108 109 110 /* 111 * sranddev: 112 * 113 * Many programs choose the seed value in a totally predictable manner. 114 * This often causes problems. We seed the generator using the much more 115 * secure random(4) interface. 116 */ 117 void 118 sranddev() 119 { 120 int fd, done; 121 122 done = 0; 123 fd = _open("/dev/random", O_RDONLY, 0); 124 if (fd >= 0) { 125 if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next)) 126 done = 1; 127 _close(fd); 128 } 129 130 if (!done) { 131 struct timeval tv; 132 unsigned long junk; 133 134 gettimeofday(&tv, NULL); 135 next = (getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk; 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