rem: len = uread(fd, buf+total, count-total);
add: len = uread(fd, (char*)buf+total, count-total);
context: readall(int fd, void *buf, size_t count){    int len, total;    for (len=0, total=0; count-total>0; total+=len) {        len = uread(fd, buf+total, count-total);        if (len == -1) {            return -1;        }        if (len == 0) {            break;        }    }    return total;}