NB的函数

void fast_memcpy (uint8_t *to, uint8_t *from, size_t count){

　register size_t n = (count + 7) / 8; /* count > 0 assumed */

　uint8_t c = count % 8;

　switch(c){

　　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);

　}
}