fy.c

/* fisher-yates shuffle */
void
shuffle(void *base, long nel, long width)
{
	unsigned char *b, *swap1, *swap2;
	long i, j, k;
	b = base;
	for(i = nel - 1; i > 0; i--){
		j = nrand(i);
		swap1 = &b[i*width];
		swap2 = &b[j*width];
		for(k = 0; k < width; k++){
			*swap1 ^= *swap2;
			*swap2 ^= *swap1;
			*swap1++ ^= *swap2++;
		}
	}
}