/*  Written in 2018 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 "xoshiro128.h"

/* This is xoshiro128** 1.1, one of our 32-bit all-purpose, rock-solid
   generators. It has excellent speed, a state size (128 bits) that is
   large enough for mild parallelism, and it passes all tests we are aware
   of.

   Note that version 1.0 had mistakenly state->s[0] instead of state->s[1] as state
   word passed to the scrambler.

   For generating just single-precision (i.e., 32-bit) floating-point
   numbers, xoshiro128+ is even faster.

   The state must be seeded so that it is not everywhere zero. */


static inline u32 rotl(const u32 x, i32 k) {
    return (x << k) | (x >> (32 - k));
}

u32 xoshiro128starstar_next(void* _state){    
    xoshiro128_state* state=_state;
    const u32 result = rotl(state->s[1] * 5, 7) * 9;

    const u32 t = state->s[1] << 9;

    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], 11);

    return result;
}