data.go
func NewDataReader(r io.Reader) (*Data, error) {
	d := newData()
	d.r = r
	d.cbs.read = C.gpgme_data_read_cb_t(C.gogpgme_readfunc)
	cbc := callbackAdd(d)
	d.cbc = cbc
	return d, handleError(C.gogpgme_data_new_from_cbs(&d.dh, &d.cbs, C.uintptr_t(cbc)))
}
func NewDataReader(r io.Reader) (*Data, error) {
	d := newData()
	d.r = r
	d.cbs.read = C.gpgme_data_read_cb_t(C.gogpgme_readfunc)
	cbc := callbackAdd(d)
	d.cbc = cbc
	return d, handleError(C.gogpgme_data_new_from_cbs(&d.dh, &d.cbs, C.uintptr_t(cbc)))
}
// NewDataReader returns a new callback based data buffer