| /* |
| * GPL HEADER START |
| * |
| * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 only, |
| * as published by the Free Software Foundation. |
| * |
| * This program is distributed in the hope that it will be useful, but |
| * WITHOUT ANY WARRANTY; without even the implied warranty of |
| * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| * General Public License version 2 for more details (a copy is included |
| * in the LICENSE file that accompanied this code). |
| * |
| * You should have received a copy of the GNU General Public License |
| * version 2 along with this program; If not, see |
| * http://www.gnu.org/licenses/gpl-2.0.html |
| * |
| * GPL HEADER END |
| */ |
| /* |
| * Copyright (c) 2007, 2010, Oracle and/or its affiliates. All rights reserved. |
| * Use is subject to license terms. |
| */ |
| /* |
| * This file is part of Lustre, http://www.lustre.org/ |
| * Lustre is a trademark of Sun Microsystems, Inc. |
| * |
| * libcfs/libcfs/prng.c |
| * |
| * concatenation of following two 16-bit multiply with carry generators |
| * x(n)=a*x(n-1)+carry mod 2^16 and y(n)=b*y(n-1)+carry mod 2^16, |
| * number and carry packed within the same 32 bit integer. |
| * algorithm recommended by Marsaglia |
| */ |
| |
| #include "../../include/linux/libcfs/libcfs.h" |
| |
| /* |
| * From: George Marsaglia <geo@stat.fsu.edu> |
| * Newsgroups: sci.math |
| * Subject: Re: A RANDOM NUMBER GENERATOR FOR C |
| * Date: Tue, 30 Sep 1997 05:29:35 -0700 |
| * |
| * You may replace the two constants 36969 and 18000 by any |
| * pair of distinct constants from this list: |
| * 18000 18030 18273 18513 18879 19074 19098 19164 19215 19584 |
| * 19599 19950 20088 20508 20544 20664 20814 20970 21153 21243 |
| * 21423 21723 21954 22125 22188 22293 22860 22938 22965 22974 |
| * 23109 23124 23163 23208 23508 23520 23553 23658 23865 24114 |
| * 24219 24660 24699 24864 24948 25023 25308 25443 26004 26088 |
| * 26154 26550 26679 26838 27183 27258 27753 27795 27810 27834 |
| * 27960 28320 28380 28689 28710 28794 28854 28959 28980 29013 |
| * 29379 29889 30135 30345 30459 30714 30903 30963 31059 31083 |
| * (or any other 16-bit constants k for which both k*2^16-1 |
| * and k*2^15-1 are prime) |
| */ |
| |
| #define RANDOM_CONST_A 18030 |
| #define RANDOM_CONST_B 29013 |
| |
| static unsigned int seed_x = 521288629; |
| static unsigned int seed_y = 362436069; |
| |
| /** |
| * cfs_rand - creates new seeds |
| * |
| * First it creates new seeds from the previous seeds. Then it generates a |
| * new pseudo random number for use. |
| * |
| * Returns a pseudo-random 32-bit integer |
| */ |
| unsigned int cfs_rand(void) |
| { |
| seed_x = RANDOM_CONST_A * (seed_x & 65535) + (seed_x >> 16); |
| seed_y = RANDOM_CONST_B * (seed_y & 65535) + (seed_y >> 16); |
| |
| return ((seed_x << 16) + (seed_y & 65535)); |
| } |
| EXPORT_SYMBOL(cfs_rand); |
| |
| /** |
| * cfs_srand - sets the initial seed |
| * @seed1 : (seed_x) should have the most entropy in the low bits of the word |
| * @seed2 : (seed_y) should have the most entropy in the high bits of the word |
| * |
| * Replaces the original seeds with new values. Used to generate a new pseudo |
| * random numbers. |
| */ |
| void cfs_srand(unsigned int seed1, unsigned int seed2) |
| { |
| if (seed1) |
| seed_x = seed1; /* use default seeds if parameter is 0 */ |
| if (seed2) |
| seed_y = seed2; |
| } |
| EXPORT_SYMBOL(cfs_srand); |
| |
| /** |
| * cfs_get_random_bytes - generate a bunch of random numbers |
| * @buf : buffer to fill with random numbers |
| * @size: size of passed in buffer |
| * |
| * Fills a buffer with random bytes |
| */ |
| void cfs_get_random_bytes(void *buf, int size) |
| { |
| int *p = buf; |
| int rem, tmp; |
| |
| LASSERT(size >= 0); |
| |
| rem = min((int)((unsigned long)buf & (sizeof(int) - 1)), size); |
| if (rem) { |
| get_random_bytes(&tmp, sizeof(tmp)); |
| tmp ^= cfs_rand(); |
| memcpy(buf, &tmp, rem); |
| p = buf + rem; |
| size -= rem; |
| } |
| |
| while (size >= sizeof(int)) { |
| get_random_bytes(&tmp, sizeof(tmp)); |
| *p = cfs_rand() ^ tmp; |
| size -= sizeof(int); |
| p++; |
| } |
| buf = p; |
| if (size) { |
| get_random_bytes(&tmp, sizeof(tmp)); |
| tmp ^= cfs_rand(); |
| memcpy(buf, &tmp, size); |
| } |
| } |
| EXPORT_SYMBOL(cfs_get_random_bytes); |