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/*
* Xorshift Pseudo Random Number Generator based on work by David Blackman
* and Sebastiano Vigna (vigna@acm.org).
*
* "Further scramblings of Marsaglia's xorshift generators"
* http://vigna.di.unimi.it/ftp/papers/xorshiftplus.pdf
* http://prng.di.unimi.it/xoroshiro128plusplus.c
*
* To the extent possible under law, the author has dedicated all copyright
* and related and neighboring rights to this software to the public domain
* worldwide. This software is distributed without any warranty.
*
* See <http://creativecommons.org/publicdomain/zero/1.0/>.
*
* This is xoroshiro128++ 1.0, one of our all-purpose, rock-solid,
* small-state generators. It is extremely (sub-ns) fast and it passes all
* tests we are aware of, but its state space is large enough only for
* mild parallelism.
*/
#include <sys/vdev_draid.h>
static inline uint64_t rotl(const uint64_t x, int k)
{
return (x << k) | (x >> (64 - k));
}
uint64_t
vdev_draid_rand(uint64_t *s)
{
const uint64_t s0 = s[0];
uint64_t s1 = s[1];
const uint64_t result = rotl(s0 + s1, 17) + s0;
s1 ^= s0;
s[0] = rotl(s0, 49) ^ s1 ^ (s1 << 21); // a, b
s[1] = rotl(s1, 28); // c
return (result);
}
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