| 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: src/lib/libc/stdlib/rand.c,v 1.17 2007/12/11 20:39:32 ache Exp $");␊ |
| 37 | ␊ |
| 38 | #ifdef TEST␊ |
| 39 | #include <stdio.h>␊ |
| 40 | #else␊ |
| 41 | #include "libsaio.h"␊ |
| 42 | #endif /* TEST */␊ |
| 43 | ␊ |
| 44 | static int␊ |
| 45 | do_rand(unsigned long *ctx)␊ |
| 46 | {␊ |
| 47 | #ifdef USE_WEAK_SEEDING␊ |
| 48 | /*␊ |
| 49 | * Historic implementation compatibility.␊ |
| 50 | * The random sequences do not vary much with the seed,␊ |
| 51 | * even with overflowing.␊ |
| 52 | */␊ |
| 53 | ␉return ((*ctx = *ctx * 1103515245 + 12345) % ((u_long)RAND_MAX + 1));␊ |
| 54 | #else /* !USE_WEAK_SEEDING */␊ |
| 55 | /*␊ |
| 56 | * Compute x = (7^5 * x) mod (2^31 - 1)␊ |
| 57 | * without overflowing 31 bits:␊ |
| 58 | * (2^31 - 1) = 127773 * (7^5) + 2836␊ |
| 59 | * From "Random number generators: good ones are hard to find",␊ |
| 60 | * Park and Miller, Communications of the ACM, vol. 31, no. 10,␊ |
| 61 | * October 1988, p. 1195.␊ |
| 62 | */␊ |
| 63 | ␉long hi, lo, x;␊ |
| 64 | ␊ |
| 65 | ␉/* Can't be initialized with 0, so use another value. */␊ |
| 66 | ␉if (*ctx == 0)␊ |
| 67 | ␉␉*ctx = 123459876;␊ |
| 68 | ␉hi = *ctx / 127773;␊ |
| 69 | ␉lo = *ctx % 127773;␊ |
| 70 | ␉x = 16807 * lo - 2836 * hi;␊ |
| 71 | ␉if (x < 0)␊ |
| 72 | ␉␉x += 0x7fffffff;␊ |
| 73 | ␉return ((*ctx = x) % ((u_long)RAND_MAX + 1));␊ |
| 74 | #endif /* !USE_WEAK_SEEDING */␊ |
| 75 | }␊ |
| 76 | ␊ |
| 77 | ␊ |
| 78 | int␊ |
| 79 | rand_r(unsigned int *ctx)␊ |
| 80 | {␊ |
| 81 | ␉u_long val = (u_long) *ctx;␊ |
| 82 | ␉int r = do_rand(&val);␊ |
| 83 | ␊ |
| 84 | ␉*ctx = (unsigned int) val;␊ |
| 85 | ␉return (r);␊ |
| 86 | }␊ |
| 87 | ␊ |
| 88 | ␊ |
| 89 | static u_long next = 1;␊ |
| 90 | ␊ |
| 91 | int␊ |
| 92 | rand()␊ |
| 93 | {␊ |
| 94 | ␉return (do_rand(&next));␊ |
| 95 | }␊ |
| 96 | ␊ |
| 97 | void␊ |
| 98 | srand(seed)␊ |
| 99 | u_int seed;␊ |
| 100 | {␊ |
| 101 | ␉next = seed;␊ |
| 102 | }␊ |
| 103 | ␊ |
| 104 | ␊ |
| 105 | #ifdef TEST␊ |
| 106 | ␊ |
| 107 | main()␊ |
| 108 | {␊ |
| 109 | int i;␊ |
| 110 | unsigned myseed;␊ |
| 111 | ␊ |
| 112 | printf("seeding rand with 0x19610910: \n");␊ |
| 113 | srand(0x19610910);␊ |
| 114 | ␊ |
| 115 | printf("generating three pseudo-random numbers:\n");␊ |
| 116 | for (i = 0; i < 3; i++)␊ |
| 117 | {␊ |
| 118 | printf("next random number = %d\n", rand());␊ |
| 119 | }␊ |
| 120 | ␊ |
| 121 | printf("generating the same sequence with rand_r:\n");␊ |
| 122 | myseed = 0x19610910;␊ |
| 123 | for (i = 0; i < 3; i++)␊ |
| 124 | {␊ |
| 125 | printf("next random number = %d\n", rand_r(&myseed));␊ |
| 126 | }␊ |
| 127 | ␊ |
| 128 | return 0;␊ |
| 129 | }␊ |
| 130 | ␊ |
| 131 | #endif /* TEST */␊ |
| 132 | |
