XORShift 2

#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] = (rs [0] ^ (rs [0] << 3)) ^ (rs [1] ^ (rs [1] << 16));
	rs [3] = (rs [0] ^ (rs [0] << 6)) ^ (rs [2] ^ (rs [2] << 10));

	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 [256];

int main (void)
{
	int i;

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

	for (i = 0; i < 7000000; i++)
		results [getrand () & 255] ++;

	for (i = 0; i < 256; i++)
		printf ("%i: %i\n", i, results [i]);

	return 0;
}