private final YangInstanceIdentifier nodeId;
private final Collection<Node> nodes;
- private final Map<DataChangeListenerRegistration<?>, Builder> subBuilders = new HashMap<>();
- private final Map<DataChangeListenerRegistration<?>, Builder> oneBuilders = new HashMap<>();
- private final Map<DataChangeListenerRegistration<?>, Builder> baseBuilders = new HashMap<>();
+ private final Map<DataChangeListenerRegistration<?>, Builder> subBuilders;
+ private final Map<DataChangeListenerRegistration<?>, Builder> oneBuilders;
+ private final Map<DataChangeListenerRegistration<?>, Builder> baseBuilders;
private ResolveDataChangeState(final YangInstanceIdentifier nodeId,
final Iterable<Builder> inheritedSub, final Collection<Builder> inheritedOne,
/*
* Collect the nodes which need to be propagated from us to the child.
*/
+ final Map<DataChangeListenerRegistration<?>, Builder> sub = new HashMap<>();
+ final Map<DataChangeListenerRegistration<?>, Builder> one = new HashMap<>();
+ final Map<DataChangeListenerRegistration<?>, Builder> base = new HashMap<>();
for (Node n : nodes) {
for (DataChangeListenerRegistration<?> l : n.getListeners()) {
final Builder b = DOMImmutableDataChangeEvent.builder(DataChangeScope.BASE);
switch (l.getScope()) {
case BASE:
- baseBuilders.put(l, b);
+ base.put(l, b);
break;
case ONE:
- oneBuilders.put(l, b);
+ one.put(l, b);
break;
case SUBTREE:
- subBuilders.put(l, b);
+ sub.put(l, b);
break;
}
}
}
+
+ baseBuilders = maybeEmpty(base);
+ oneBuilders = maybeEmpty(one);
+ subBuilders = maybeEmpty(sub);
+ }
+
+ private static <K, V> Map<K, V> maybeEmpty(final Map<K, V> map) {
+ if (map.isEmpty()) {
+ return Collections.emptyMap();
+ }
+ return map;
}
/**
*/
public ResolveDataChangeState child(final PathArgument childId) {
/*
- * We instantiate a concatenation only when needed, otherwise
- * we reuse the collection. This speeds up Iterables.isEmpty()
- * in needsProcessing().
+ * We instantiate a concatenation only when needed:
+ *
+ * 1) If our collection is empty, we reuse the parent's. This is typically the case
+ * for intermediate node, which should be the vast majority.
+ * 2) If the parent's iterable is a Collection and it is empty, reuse our collection.
+ * This is the case for the first node which defines a subtree listener in a
+ * particular subtree.
+ * 3) Concatenate the two collections. This happens when we already have some
+ * subtree listeners and we encounter a node which adds a few more.
+ *
+ * This allows us to lower number of objects allocated and also
+ * speeds up Iterables.isEmpty() in needsProcessing().
+ *
+ * Note that the check for Collection in 2) relies on precisely this logic, which
+ * ensures that we simply cannot see an empty concatenation, but rather start off with
+ * an empty collection, then switch to a non-empty collection and finally switch to
+ * a concatenation. This saves us from instantiating iterators, which a trivial
+ * Iterables.isEmpty() would do as soon as we cross case 3).
*/
final Iterable<Builder> sb;
- if (subBuilders.isEmpty()) {
- sb = inheritedSub;
+ if (!subBuilders.isEmpty()) {
+ if (inheritedSub instanceof Collection && ((Collection<?>) inheritedSub).isEmpty()) {
+ sb = subBuilders.values();
+ } else {
+ sb = Iterables.concat(inheritedSub, subBuilders.values());
+ }
} else {
- sb = Iterables.concat(inheritedSub, subBuilders.values());
+ sb = inheritedSub;
}
return new ResolveDataChangeState(nodeId.node(childId), sb,
if (!inheritedOne.isEmpty()) {
return true;
}
- // Have SUBTREE listeners
- if (!Iterables.isEmpty(inheritedSub)) {
- return true;
+
+ /*
+ * Have SUBTREE listeners
+ *
+ * This is slightly magical replacement for !Iterables.isEmpty(inheritedSub).
+ * It relies on the logic in child(), which gives us the guarantee that when
+ * inheritedSub is not a Collection, it is guaranteed to be non-empty (which
+ * means we need to process). If it is a collection, we still need to check
+ * it for emptiness.
+ *
+ * Unlike Iterables.isEmpty() this code does not instantiate any temporary
+ * objects and is thus more efficient.
+ */
+ if (inheritedSub instanceof Collection) {
+ return !((Collection<?>) inheritedSub).isEmpty();
}
- return false;
+ // Non-Collection => non-empty => have to process
+ return true;
}
/**