2 * Copyright (c) 2020 PANTHEON.tech, s.r.o. and others. All rights reserved.
4 * This program and the accompanying materials are made available under the
5 * terms of the Eclipse Public License v1.0 which accompanies this distribution,
6 * and is available at http://www.eclipse.org/legal/epl-v10.html
8 package org.opendaylight.mdsal.binding.dom.codec.impl;
10 import static com.google.common.base.Verify.verify;
11 import static java.util.Objects.requireNonNull;
13 import com.google.common.annotations.VisibleForTesting;
14 import java.lang.invoke.MethodHandles;
15 import java.lang.invoke.VarHandle;
16 import java.util.AbstractList;
17 import java.util.Collection;
18 import java.util.Comparator;
19 import java.util.List;
20 import java.util.RandomAccess;
21 import java.util.function.UnaryOperator;
22 import org.eclipse.jdt.annotation.NonNull;
23 import org.opendaylight.yangtools.concepts.Immutable;
24 import org.opendaylight.yangtools.yang.binding.DataObject;
25 import org.opendaylight.yangtools.yang.data.api.schema.DistinctNodeContainer;
26 import org.opendaylight.yangtools.yang.data.api.schema.NormalizedNodeContainer;
27 import org.slf4j.Logger;
28 import org.slf4j.LoggerFactory;
31 * Lazily-populated List implementation backed by NormalizedNodes. This implementation defers creating Binding objects
32 * until they are actually needed, caching them in a pre-allocated array.
35 * The cost of this deferred instantiation is two-fold:
37 * <li>each access issues a {@link VarHandle#getAcquire(Object...)} load and a class equality check</li>
38 * <li>initial load additionally incurs a {@link VarHandle#compareAndExchangeRelease(Object...)} store</li>
41 * @param <E> the type of elements in this list
43 final class LazyBindingList<E extends DataObject> extends AbstractList<E> implements Immutable, RandomAccess {
44 // Object array access variable handle
45 static final VarHandle OBJ_AA = MethodHandles.arrayElementVarHandle(Object[].class);
47 private static final Logger LOG = LoggerFactory.getLogger(LazyBindingList.class);
48 private static final String LAZY_CUTOFF_PROPERTY =
49 "org.opendaylight.mdsal.binding.dom.codec.impl.LazyBindingList.max-eager-elements";
50 private static final int DEFAULT_LAZY_CUTOFF = 16;
53 static final int LAZY_CUTOFF;
56 final int value = Integer.getInteger(LAZY_CUTOFF_PROPERTY, DEFAULT_LAZY_CUTOFF);
58 LOG.info("Lazy population of lists disabled");
59 LAZY_CUTOFF = Integer.MAX_VALUE;
61 LOG.info("Using lazy population for lists larger than {} element(s)", value);
66 private final ListNodeCodecContext<E> codec;
67 private final Object[] objects;
69 private LazyBindingList(final ListNodeCodecContext<E> codec,
70 final Collection<? extends NormalizedNodeContainer<?>> entries) {
71 this.codec = requireNonNull(codec);
72 objects = entries.toArray();
75 static <E extends DataObject> @NonNull List<E> create(final ListNodeCodecContext<E> codec, final int size,
76 final Collection<? extends DistinctNodeContainer<?, ?>> entries) {
78 // Do not bother with lazy instantiation in case of a singleton
79 return List.of(codec.createBindingProxy(entries.iterator().next()));
81 return size > LAZY_CUTOFF ? new LazyBindingList<>(codec, entries) : eagerList(codec, size, entries);
84 private static <E extends DataObject> @NonNull List<E> eagerList(final ListNodeCodecContext<E> codec,
85 final int size, final Collection<? extends DistinctNodeContainer<?, ?>> entries) {
86 @SuppressWarnings("unchecked")
87 final E[] objs = (E[]) new DataObject[size];
89 for (DistinctNodeContainer<?, ?> node : entries) {
90 objs[offset++] = codec.createBindingProxy(node);
92 verify(offset == objs.length);
98 return objects.length;
102 public E get(final int index) {
103 final Object obj = OBJ_AA.getAcquire(objects, index);
104 // Check whether the object has been converted. The object is always non-null, but it can either be in DOM form
105 // (either a MapEntryNode or UnkeyedListEntryNode) or in Binding form. We know the exact class for the latter,
106 // as we are creating it via codec -- hence we can perform a direct comparison.
108 // We could do a Class.isInstance() check here, but since the implementation is not marked as final (yet) we
109 // would be at the mercy of CHA being able to prove this invariant.
110 return obj.getClass() == codec.generatedClass() ? (E) obj : load(index, (DistinctNodeContainer<?, ?>) obj);
113 private @NonNull E load(final int index, final DistinctNodeContainer<?, ?> node) {
114 final E ret = codec.createBindingProxy(node);
115 final Object witness;
116 return (witness = OBJ_AA.compareAndExchangeRelease(objects, index, node, ret)) == node ? ret : (E) witness;
120 @SuppressWarnings("checkstyle:parameterName")
121 public boolean remove(final Object o) {
126 @SuppressWarnings("checkstyle:parameterName")
127 public boolean addAll(final Collection<? extends E> c) {
132 @SuppressWarnings("checkstyle:parameterName")
133 public boolean addAll(final int index, final Collection<? extends E> c) {
138 @SuppressWarnings("checkstyle:parameterName")
139 public boolean removeAll(final Collection<?> c) {
144 @SuppressWarnings("checkstyle:parameterName")
145 public boolean retainAll(final Collection<?> c) {
150 @SuppressWarnings("checkstyle:parameterName")
151 public void sort(final Comparator<? super E> c) {
156 public void replaceAll(final UnaryOperator<E> operator) {
161 protected void removeRange(final int fromIndex, final int toIndex) {
165 private static UnsupportedOperationException uoe() {
166 return new UnsupportedOperationException("Modification not supported");