A lot of data has to be exchanged between the user and the crypto
engine, like plaintext messages, ciphertext, signatures and
information about the keys. The technical details about exchanging
the data information are completely abstracted by GPGME.
The user provides and receives the data via gpgme_data_t objects,
regardless of the communication protocol between GPGME and
the crypto engine in use.
The
gpgme_data_ttype is a handle for a container for generic data, which is used by GPGME to exchange data with the user.
gpgme_data_t objects do not provide notifications on events.
It is assumed that read and write operations are blocking until data
is available. If this is undesirable, the application must ensure
that all GPGME data operations always have data available, for example
by using memory buffers or files rather than pipes or sockets. This
might be relevant, for example, if the external event loop mechanism
is used.