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 #define NSHUFF 100 /* to drop part of seed -> 1st value correlation */ 55 56 static int 57 do_rand(unsigned long *ctx) 58 { 59 #ifdef USE_WEAK_SEEDING 60 /* 61 * Historic implementation compatibility. 62 * The random sequences do not vary much with the seed, 63 * even with overflowing. 64 */ 65 return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1)); 66 #else /* !USE_WEAK_SEEDING */ 67 /* 68 * Compute x = (7^5 * x) mod (2^31 - 1) 69 * wihout overflowing 31 bits: 70 * (2^31 - 1) = 127773 * (7^5) + 2836 71 * From "Random number generators: good ones are hard to find", 72 * Park and Miller, Communications of the ACM, vol. 31, no. 10, 73 * October 1988, p. 1195. 74 */ 75 long hi, lo, x; 76 77 /* Can't be initialized with 0, so use another value. */ 78 if (*ctx == 0) 79 *ctx = 123459876; 80 hi = *ctx / 127773; 81 lo = *ctx % 127773; 82 x = 16807 * lo - 2836 * hi; 83 if (x < 0) 84 x += 0x7fffffff; 85 return ((*ctx = x) % ((u_long)RAND_MAX + 1)); 86 #endif /* !USE_WEAK_SEEDING */ 87 } 88 89 90 int 91 rand_r(unsigned int *ctx) 92 { 93 u_long val = (u_long) *ctx; 94 int r = do_rand(&val); 95 96 *ctx = (unsigned int) val; 97 return (r); 98 } 99 100 101 static u_long next = 892053144; /* after srand(1), NSHUFF counted */ 102 103 int 104 rand() 105 { 106 return (do_rand(&next)); 107 } 108 109 void 110 srand(seed) 111 u_int seed; 112 { 113 int i; 114 115 next = seed; 116 for (i = 0; i < NSHUFF; i++) 117 (void)rand(); 118 } 119 120 121 /* 122 * sranddev: 123 * 124 * Many programs choose the seed value in a totally predictable manner. 125 * This often causes problems. We seed the generator using the much more 126 * secure random(4) interface. 127 */ 128 void 129 sranddev() 130 { 131 int fd, done; 132 133 done = 0; 134 fd = _open("/dev/random", O_RDONLY, 0); 135 if (fd >= 0) { 136 if (_read(fd, (void *) &next, sizeof(next)) == sizeof(next)) 137 done = 1; 138 _close(fd); 139 } 140 141 if (!done) { 142 struct timeval tv; 143 unsigned long junk; 144 145 gettimeofday(&tv, NULL); 146 srand((getpid() << 16) ^ tv.tv_sec ^ tv.tv_usec ^ junk); 147 } 148 } 149 150 151 #ifdef TEST 152 153 main() 154 { 155 int i; 156 unsigned myseed; 157 158 printf("seeding rand with 0x19610910: \n"); 159 srand(0x19610910); 160 161 printf("generating three pseudo-random numbers:\n"); 162 for (i = 0; i < 3; i++) 163 { 164 printf("next random number = %d\n", rand()); 165 } 166 167 printf("generating the same sequence with rand_r:\n"); 168 myseed = 0x19610910; 169 for (i = 0; i < 3; i++) 170 { 171 printf("next random number = %d\n", rand_r(&myseed)); 172 } 173 174 return 0; 175 } 176 177 #endif /* TEST */ 178 179