reader.go
func OpenReader(name, password string) (*ReadCloser, error) {
	v, err := openVolume(name, password)
	if err != nil {
		return nil, err
	}
	rc := new(ReadCloser)
	rc.v = v
	rc.Reader.init(v)
	return rc, nil
}
func OpenReader(name, password string) (*ReadCloser, error) {
	v, err := openVolume(name, password)
	if err != nil {
		return nil, err
	}
	rc := new(ReadCloser)
	rc.v = v
	rc.Reader.init(v)
	return rc, nil
}
// OpenReader opens a RAR archive specified by the name and returns a ReadCloser.