code &= 0xFFFFFFFFFFFFFFFFULL;
static int nut_probe(AVProbeData *p){    int i;    uint64_t code;    code = 0xff;    for (i = 0; i < p->buf_size; i++) {        int c = p->buf[i];        code = (code << 8) | c;        code &= 0xFFFFFFFFFFFFFFFFULL;        if (code == MAIN_STARTCODE)            return AVPROBE_SCORE_MAX;    }    return 0;}