func newArchive50(r *bufio.Reader, password string) fileBlockReader {
	a := new(archive50)
	a.v = r
	a.pass = []byte(password)
	a.buf = make([]byte, 100)
	return a
}
func newArchive50(r *bufio.Reader, password string) fileBlockReader {
	a := new(archive50)
	a.v = r
	a.pass = []byte(password)
	a.buf = make([]byte, 100)
	return a
}
// newArchive50 creates a new fileBlockReader for a Version 5 archive.