samerand/samerand.c

#include <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/stat.h>
#include <sys/types.h>

uint32_t xorshift32(uint32_t x)
{
	/* Algorithm "xor" from p. 4 of Marsaglia, "Xorshift RNGs" */
	x = x ^ (x << 13);
	x = x ^ (x >> 17);
	x = x ^ (x << 5);
	return x;
}

uint32_t get_rand(uint32_t x) {
    uint32_t out = 0;
    int i;
    for (i = 0; i < 32; i++) {
        x = xorshift32(x);
        if ((x & 1) == 1)
            out = out | (1<< i);
    }
    return out;
}

int main(int argc, char **argv) {
    int i;

    int fd = open("rom.bin", O_WRONLY | O_CREAT | O_TRUNC, 0777);
    uint32_t init = 1;
    for (i = 0; i < 2048; i++) {
        init = get_rand(init);
        // printf("%08x\n", init);
        write(fd, &init, sizeof(init));
    }

    return 0;
}