@deftypefun {void} {gnutls_db_set_retrieve_function} (gnutls_session_t @var{session}, gnutls_db_retr_func @var{retr_func})
@var{session}: is a @code{gnutls_session_t}  type.

@var{retr_func}: is the function.

Sets the function that will be used to retrieve data from the
resumed sessions database.  This function must return a
gnutls_datum_t containing the data on success, or a gnutls_datum_t
containing null and 0 on failure.

The datum's data must be allocated using the function
@code{gnutls_malloc()} .

The first argument to  @code{retr_func} will be null unless
@code{gnutls_db_set_ptr()}  has been called.
@end deftypefun