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/*
* 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 <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);
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