func readuint8(pos int64) uint8 {
	var retval uint8
	data := make([]byte, 1)
	_, err := f.ReadAt(data, pos - 1)
	if err != nil {
		fmt.Println("File read failed:", err)
	}
	retval = data[0]
	return retval
}
func readuint8(pos int64) uint8 {
	var retval uint8
	data := make([]byte, 1)
	_, err := f.ReadAt(data, pos - 1)
	if err != nil {
		fmt.Println("File read failed:", err)
	}
	retval = data[0]
	return retval
}
// read byte