mirror of
https://git.proxmox.com/git/mirror_zfs.git
synced 2024-12-27 03:19:35 +03:00
41 lines
1.2 KiB
C
41 lines
1.2 KiB
C
|
/*
|
||
|
|
* 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);
|
||
|
|
}
|