#include <stdint.h>
#include <stdio.h>
#include <time.h>

struct xorshift32_state {
    uint32_t a;
};

/* The state must be initialized to non-zero */
uint32_t xorshift32(struct xorshift32_state *state) {
    /* Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs" */
    uint32_t x = state->a;
    x ^= x << 13;
    x ^= x >> 17;
    x ^= x << 5;
    return state->a = x;
}

struct xorshift64_state {
    uint64_t a;
};

/* The state must be initialized to non-zero */
uint64_t xorshift64(struct xorshift64_state *state) {
    uint64_t x = state->a;
    x ^= x << 13;
    x ^= x >> 7;
    x ^= x << 17;
    return state->a = x;
}

/* struct xorshift128_state can alternatively be defined as a pair
   of uint64_t or a uint128_t where supported */
struct xorshift128_state {
    uint32_t x[4];
};

/* The state must be initialized to non-zero */
uint32_t xorshift128(struct xorshift128_state *state) {
    /* Algorithm "xor128" from p. 5 of Marsaglia, "Xorshift RNGs" */
    uint32_t t = state->x[3];

    uint32_t s = state->x[0]; /* Perform a contrived 32-bit shift. */
    state->x[3] = state->x[2];
    state->x[2] = state->x[1];
    state->x[1] = s;

    t ^= t << 11;
    t ^= t >> 8;
    return state->x[0] = t ^ s ^ (s >> 19);
}

int main(void) {
    struct xorshift32_state s = {};
    s.a = time(0);

    for (int a = 0; a < 10; a++) {
        printf("Number %d: %d\n", a, xorshift32(&s));
    }
}