Duff's device - Fast way to copy in chunks in C

Duffs_device.c

register n = (count + 7) / 8;    /* count > 0 assumed */
        switch (count % 8)
        {
        case 0:    do {    *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);