/*  Written in 2019 by David Blackman and Sebastiano Vigna (vigna@acm.org)

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/>. */

#include "xoshiro256.h"

/* This is xoshiro256++ 1.0, one of our all-purpose, rock-solid generators.
   It has excellent (sub-ns) speed, a state (256 bits) that is large
   enough for any parallel application, and it passes all tests we are
   aware of.

   For generating just floating-poi32 numbers, xoshiro256+ is even faster.

   The state must be seeded so that it is not everywhere zero. If you have
   a 64-bit seed, we suggest to seed a splitmix64 generator and use its
   output to fill s. */

static inline u64 rotl(const u64 x, i32 k) {
    return (x << k) | (x>>(64 - k));
}

u64 xoshiro256plusplus_next(void* _state) {
    xoshiro256_state* state=_state;
    const u64 result=rotl(state->s[0] + state->s[3], 23) + state->s[0];
    const u64 t=state->s[1] << 17;
    state->s[2] ^= state->s[0];
    state->s[3] ^= state->s[1];
    state->s[1] ^= state->s[2];
    state->s[0] ^= state->s[3];
    state->s[2] ^= t;
    state->s[3]=rotl(state->s[3], 45);
    return result;
}