Experimental Physics and
Industrial Control System

[...]
Here is the the first thing I am seriously stumbling over:

static void db_queue_event_log (evSubscrip *pevent, db_field_log *pLog)
{
    ...
    /*
     * if we have an event on the queue and both the last
     * event on the queue and the current event are emtpy
     * (i.e. of type dbfl_type_rec), simply ignore duplicate
     * events (saving empty events serves no purpose)
     */
    if (pevent->npend > 0u &&
        (*pevent->pLastLog)->type == dbfl_type_rec &&
        pLog->type == dbfl_type_rec) {
        db_delete_field_log(pLog);
        UNLOCKEVQUE (ev_que);
        return;
    }
    ...
}

I don't quite get the logic here. What is (the definition of) an empty
event? And why does dbfl_type_rec indicate that the event is empty?