typedef struct an_extfn_api {
    // arg_handle = a handle to arguments provided by the server
    // arg_num    = argument number  0 ..N,  0 =return value
    // data       = pointer to arg data
    
    // Calling get_value on an OUT argument will simply return the data type
    // of the argument, and will return data as NULL.

    // Must call get_value before get_piece.

    short (SQL_CALLBACK *get_value)(
				    void *          arg_handle,
				    a_sql_uint32    arg_num,
				    an_extfn_value *value
				    );
    short (SQL_CALLBACK *get_piece)(
				    void *          arg_handle,
				    a_sql_uint32    arg_num,
				    an_extfn_value *value,
				    a_sql_uint32    offset
				    );

    // To return a null value, set "data" to NULL in an_extfn_value.
    // The total_len field is ignored on calls to set_value, the data supplied
    // becomes the value of the argument if append is FALSE; otherwise the
    // data is appended to the current value of the argument. It is expected
    // that set_value will be called with append=FALSE for an argument before
    // being called with append=TRUE for the same argument.
    // The append field is ignored for fixed length data types (i.e., all 
    // numeric data types)

    short (SQL_CALLBACK *set_value)(
				    void *          arg_handle,
				    a_sql_uint32    arg_num,
				    an_extfn_value *value,
				    short	    append
				    );
    // The external function should call the following
    // if it expects the server to pass on any interrupts.
    // The cancel_handle will be passed back into the
    // DLL by the server on the extfn_cancel call below 
    void (SQL_CALLBACK *set_cancel)(
				    void *	arg_handle,
				    void *	cancel_handle
				    );
} an_extfn_api;

an_extfn_api = class
   function  get_value(arg_handle : pointer;
                              arg_num    : integer;
                              value        : an_extfn_value):smallint;    
......................    
end;