2 * Copyright (c) 2015 Cisco Systems, Inc. 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.yangtools.yang.data.util;
10 import com.google.common.annotations.Beta;
11 import com.google.common.base.Preconditions;
12 import com.google.common.collect.Interner;
13 import com.google.common.collect.Interners;
14 import javax.annotation.Nonnull;
15 import javax.annotation.Nullable;
16 import org.opendaylight.yangtools.yang.data.api.schema.LeafNode;
17 import org.opendaylight.yangtools.yang.model.api.LeafSchemaNode;
18 import org.opendaylight.yangtools.yang.model.api.TypeDefinition;
19 import org.opendaylight.yangtools.yang.model.api.type.BooleanTypeDefinition;
20 import org.opendaylight.yangtools.yang.model.api.type.EnumTypeDefinition;
21 import org.opendaylight.yangtools.yang.model.api.type.IdentityrefTypeDefinition;
22 import org.slf4j.Logger;
23 import org.slf4j.LoggerFactory;
26 * Utility class for sharing instances of {@link LeafNode}s which have low cardinality-- e.g. those which hold
27 * boolean or enumeration values. Instances containing attributes are not interned.
29 * Such objects have cardinality which is capped at the product of QNAMES * TYPE_CARDINALITY, where QNAMES is the total
30 * number of different QNames where the type is used and TYPE_CARDINALITY is the number of possible values for the type.
31 * Boolean has cardinality of 2, enumerations have cardinality equal to the number of enum statements.
33 * The theory here is that we tend to have a large number (100K+) of entries in a few places, which could end up hogging
34 * the heap retained via the DataTree with duplicate objects (same QName, same value, different object). Using this
35 * utility, such objects will end up reusing the same object, preventing this overhead.
38 public final class LeafInterner {
39 private static final Logger LOG = LoggerFactory.getLogger(LeafInterner.class);
40 private static final Interner<Object> INTERNER = Interners.newWeakInterner();
42 private LeafInterner() {
43 throw new UnsupportedOperationException();
46 private static <T extends LeafNode<?>> T intern(final T sample) {
47 if (sample.getAttributes().isEmpty()) {
48 @SuppressWarnings("unchecked")
49 final T ret = (T) INTERNER.intern(sample);
50 LOG.trace("Interned object {} to {}", sample, ret);
53 // Non-empty attributes, do not intern
59 * Return a {@link LeafInterner} for a particular schema. Interner instances must not be reused for leaves of
60 * different types, otherwise they may produce unexpected results.
62 * @param schema The leaf node's schema
63 * @return An interner instance
65 @Nonnull public static <T extends LeafNode<?>> Interner<T> forSchema(@Nullable final LeafSchemaNode schema) {
67 final TypeDefinition<?> type = schema.getType();
68 if (type instanceof BooleanTypeDefinition || type instanceof EnumTypeDefinition ||
69 type instanceof IdentityrefTypeDefinition) {
70 return LeafInterner::intern;
74 return Preconditions::checkNotNull;