XORShift

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

static uint32_t rs [4];

void seedrand (uint32_t seed)
{
    rs [0] = seed;
    rs [1] = seed << 1;
    rs [2] = seed & rs [1];
    rs [3] = rs [1] & ~rs [2];

    printf ("Using %u, %u, %u, and %u as seeds.\n", rs [0], rs [1], rs [2], rs [3]);
    return;
}

uint32_t getrand (void)
{
    uint32_t tmp;

    tmp = rs [0] ^ (rs [0] << 5);

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

    return rs [3] = (rs [3] ^ (rs [3] >> 12)) ^ (tmp ^ (tmp >> 16));
}

int results [16];

int main (void)
{
    int i;

    printf ("Testing random number generator\n");
    seedrand (time (NULL));

    for (i = 0; i < 700000; i++)
        results [getrand () & 15] ++;

    for (i = 0; i < 16; i++)
        printf ("%i: %i\n", i, results [i]);

    return 0;
}