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base: add Xoroshiro PRNG utility to base/internal

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Norman Feske 2024-03-07 11:14:42 +01:00 committed by Christian Helmuth
parent 3dbe398252
commit 3e46cf5664
1 changed files with 66 additions and 0 deletions
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repos/base/src/include/base/internal/xoroshiro.h Normal file
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/*
* \brief Xoroshiro pseudo random-number generator
* \author Josef Soentgen
* \date 2022-05-19
*
* Based on Xoroshiro128+ written in 2014-2016 by Sebastiano Vigna (vigna@acm.org)
*
* (see http://xoroshiro.di.unimi.it/xorshift128plus.c and
* http://xoroshiro.di.unimi.it/splitmix64.c)
*/
/*
* Copyright (C) 2022 Genode Labs GmbH
*
* This file is part of the Genode OS framework, which is distributed
* under the terms of the GNU Affero General Public License version 3.
*/
#ifndef _INCLUDE__BASE__INTERNAL__XOROSHIRO_H_
#define _INCLUDE__BASE__INTERNAL__XOROSHIRO_H_
#include <base/stdint.h>
namespace Genode { class Xoroshiro_128_plus; }
class Genode::Xoroshiro_128_plus
{
private:
uint64_t _seed;
uint64_t _s[2] { _splitmix64(), _splitmix64() };
uint64_t _splitmix64()
{
uint64_t z = (_seed += __UINT64_C(0x9E3779B97F4A7C15));
z = (z ^ (z >> 30)) * __UINT64_C(0xBF58476D1CE4E5B9);
z = (z ^ (z >> 27)) * __UINT64_C(0x94D049BB133111EB);
return z ^ (z >> 31);
}
static uint64_t _rotl(uint64_t const x, int const k)
{
return (x << k) | (x >> (64 - k));
}
public:
Xoroshiro_128_plus(uint64_t seed) : _seed(seed) { }
uint64_t value()
{
uint64_t const s0 = _s[0];
uint64_t s1 = _s[1];
uint64_t const result = s0 + s1;
s1 ^= s0;
_s[0] = _rotl(s0, 55) ^ s1 ^ (s1 << 14);
_s[1] = _rotl(s1, 36);
return result;
}
};
#endif /* _INCLUDE__BASE__INTERNAL__XOROSHIRO_H_ */