private void checkForFinale() {
if ($gate.isPermanentlyEmpty()) {
// give our listener a chance to notice our final drain.
// set our listener to null at the same time. this prevents possibly awkward loops if one
// tries to readAllNow() in a listener before checking isExhausted().
Listener<ReadHead<$T>> $del = $el;
$el =
null; /* we can't do this set after invoking the listener because it could potentially cause the whole loop we're trying to block here. */
invokeListener($del);
}
}
