Splitmix64.h

#ifndef SPLITMIX64__H__
#define SPLITMIX64__H__

#include <cstdint>

constexpr uint64_t splitmix64_stateless(uint64_t previous_state) noexcept
{
	uint64_t z = previous_state + 0x9E3779B97F4A7C15ull;
	z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9ull;
	z = (z ^ (z >> 27)) * 0x94D049BB133111EBull;
	return z ^ (z >> 31);
}

class Splitmix64
{
public:
	Splitmix64() noexcept = default;
	Splitmix64(uint64_t seed) noexcept : state_(seed) {}

	uint64_t next() noexcept
	{
		state_ += 0x9E3779B97F4A7C15ull;
		uint64_t z = state_;
		z = (z ^ (z >> 30)) * 0xBF58476D1CE4E5B9ull;
		z = (z ^ (z >> 27)) * 0x94D049BB133111EBull;
		return z ^ (z >> 31);
	}


private:
	uint64_t state_ = 0;
};

#endif // #ifndef SPLITMIX64__H__