Daffodil parsing generates event callbacks to an InfosetOutputter, which is analogous to a SAX event handler.
Drill is expecting an iterator style of calling next() to advance through the input, i.e., Drill has the control thread and expects to do pull parsing. At least from the code I studied in the format-xml contrib. Is there any alternative? Before I dig into creating another one of these co-routine-style control inversions (which have proven to be problematic for performance.
