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/*
* Copyright (C) 2001-2004 Sistina Software, Inc. All rights reserved.
* Copyright (C) 2004 Red Hat, Inc. All rights reserved.
*
* This file is part of LVM2.
*
* This copyrighted material is made available to anyone wishing to use,
* modify, copy, or redistribute it subject to the terms and conditions
* of the GNU General Public License v.2.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software Foundation,
* Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
#include "random.h"
#include "log.h"
int32_t _a[56];
int32_t *_r;
static inline int32_t _mod_diff(int32_t x, int32_t y)
{
return (x - y) & 0x7fffffff;
}
static int32_t _flip_cycle(void)
{
int32_t *ii, *jj;
for (ii = _a + 1, jj = _a + 32; jj <= _a + 55; ii++, jj++)
*ii = _mod_diff(*ii, *jj);
for (jj = _a + 1; ii <= _a + 55; ii++, jj++)
*ii = _mod_diff(*ii, *jj);
_r = _a + 54;
return _a[55];
}
static void rand_init(int32_t seed)
{
int64_t i;
int64_t prev = seed, next = 1;
seed = prev = _mod_diff(prev, 0); /* strip the sign */
_a[55] = prev;
for (i = 21; i; i = (i + 21) % 55) {
_a[i] = next;
next = _mod_diff(prev, next);
if(seed & 1)
seed = 0x40000000L + (seed >> 1);
else
seed >>= 1;
next = _mod_diff(next, seed);
prev = _a[i];
}
_flip_cycle();
_flip_cycle();
_flip_cycle();
_flip_cycle();
_flip_cycle();
}
/*
* FIXME: move this to be an inline in the
* header.
*/
int32_t rand_get(void)
{
return (*_r >= 0) ? *_r-- : _flip_cycle();
}
/*
* just used by rand_check
*/
#define t31 0x80000000
static int32_t _uniform(int32_t m)
{
uint32_t t = t31 - (t31 % m);
int32_t r;
do
r = next_rand(sc);
while (t <= (uint32_t) r);
return r % m;
}
/*
* Checks I've copied the code correctly.
*/
int rand_check(void)
{
int j;
rand_init(-314159L);
if (next_rand(sc) != 119318998) {
log_err("Random number generator failed check 1");
return 0;
}
for(j = 1; j <= 133; j++)
rand_get();
if (_uniform(0x55555555L) != 748103812) {
log_err("Random number generator failed check 2");
return 0;
}
return 1;
}
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