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Diffstat (limited to 'drivers/staging/lustre/lnet/libcfs/prng.c')
| -rw-r--r-- | drivers/staging/lustre/lnet/libcfs/prng.c | 140 |
1 files changed, 140 insertions, 0 deletions
diff --git a/drivers/staging/lustre/lnet/libcfs/prng.c b/drivers/staging/lustre/lnet/libcfs/prng.c new file mode 100644 index 000000000000..c75ae9a68e76 --- /dev/null +++ b/drivers/staging/lustre/lnet/libcfs/prng.c @@ -0,0 +1,140 @@ +/* + * 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.sun.com/software/products/lustre/docs/GPLv2.pdf + * + * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + * 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); |