#include "xorshift.h"

#include <assert.h>
#include <string.h>

static uint32_t xorshift128_seed[4]     = {1, 1, 1, 1};
static uint64_t xorshift128plus_seed[2] = {1, 1};

void set_xorshift128_seed(uint32_t seed[4])
{
    for (size_t i = 0; i < 4; ++i) {

        assert(seed[i] != (uint32_t)0);
        xorshift128_seed[i] = seed[i];
    }
}

uint32_t xorshift128()
{
    uint32_t t = xorshift128_seed[0];

    t ^= t << 11;
    t ^= t >> 8;

    xorshift128_seed[0] = xorshift128_seed[1];
    xorshift128_seed[1] = xorshift128_seed[2];
    xorshift128_seed[2] = xorshift128_seed[3];

    xorshift128_seed[3] ^= xorshift128_seed[3] >> 19;
    xorshift128_seed[3] ^= t;
    return xorshift128_seed[3];
}


void set_xorshift128plus_seed(uint64_t seed[2])
{
    for (size_t i = 0; i < 2; ++i) {

        assert(seed[i] != (uint64_t)0);
        xorshift128plus_seed[i] = seed[i];
    }
}

uint64_t xorshift128plus()
{
    uint64_t x = xorshift128plus_seed[0];
    uint64_t const y = xorshift128plus_seed[1];

    xorshift128plus_seed[0] = y;
    x ^= x << 23;
    xorshift128plus_seed[1] = x ^ y ^ (x >> 17) ^ (y >> 26);

    return xorshift128plus_seed[1] + y;
}