Duff's Template

template <class T>
void
duff(T* to, T* from, T count) {
  T n = (count+7)/8;
  switch (count % 8) {
    do {
    case 0: *to = *from++;
    case 7: *to = *from++;
    case 6: *to = *from++;
    case 5: *to = *from++;
    case 4: *to = *from++;
    case 3: *to = *from++;
    case 2: *to = *from++;
    case 1: *to = *from++;
    } while (--n > 0);
  }
}