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/* $OpenBSD: shuffle.c,v 1.4 2015/01/22 17:42:09 reyk Exp $ */
/*
* Portions Copyright (C) 2008 Theo de Raadt
*
* Permission to use, copy, modify, and distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND INTERNET SOFTWARE CONSORTIUM
* DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL
* INTERNET SOFTWARE CONSORTIUM BE LIABLE FOR ANY SPECIAL, DIRECT,
* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
* FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
* NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
* WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
/* based on: bind/lib/isc/shuffle.c,v 1.4 2008/07/09 17:07:32 reyk Exp $ */
#include <sys/types.h>
#include <stdlib.h>
#include <assert.h>
#include "relayd.h"
#define VALID_SHUFFLE(x) (x != NULL)
void
shuffle_init(struct shuffle *shuffle)
{
int i, i2;
assert(VALID_SHUFFLE(shuffle));
shuffle->isindex = 0;
/* Initialize using a Knuth shuffle */
for (i = 0; i < 65536; ++i) {
i2 = arc4random_uniform(i + 1);
shuffle->id_shuffle[i] = shuffle->id_shuffle[i2];
shuffle->id_shuffle[i2] = i;
}
}
u_int16_t
shuffle_generate16(struct shuffle *shuffle)
{
u_int32_t si;
u_int16_t r;
int i, i2;
assert(VALID_SHUFFLE(shuffle));
do {
si = arc4random();
i = shuffle->isindex & 0xFFFF;
i2 = (shuffle->isindex - (si & 0x7FFF)) & 0xFFFF;
r = shuffle->id_shuffle[i];
shuffle->id_shuffle[i] = shuffle->id_shuffle[i2];
shuffle->id_shuffle[i2] = r;
shuffle->isindex++;
} while (r == 0);
return (r);
}
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