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.collect.Interner;
12 import com.google.common.collect.Interners;
13 import java.util.Optional;
14 import org.eclipse.jdt.annotation.NonNull;
15 import org.eclipse.jdt.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.EmptyTypeDefinition;
21 import org.opendaylight.yangtools.yang.model.api.type.EnumTypeDefinition;
22 import org.opendaylight.yangtools.yang.model.api.type.IdentityrefTypeDefinition;
23 import org.opendaylight.yangtools.yang.model.api.type.Int8TypeDefinition;
24 import org.opendaylight.yangtools.yang.model.api.type.Uint8TypeDefinition;
25 import org.slf4j.Logger;
26 import org.slf4j.LoggerFactory;
29 * Utility class for sharing instances of {@link LeafNode}s which have low cardinality-- e.g. those which hold
30 * boolean or enumeration values. Instances containing attributes are not interned.
33 * Such objects have cardinality which is capped at the product of QNAMES * TYPE_CARDINALITY, where QNAMES is the total
34 * number of different QNames where the type is used and TYPE_CARDINALITY is the number of possible values for the type.
35 * Boolean has cardinality of 2, enumerations have cardinality equal to the number of enum statements.
38 * The theory here is that we tend to have a large number (100K+) of entries in a few places, which could end up hogging
39 * the heap retained via the DataTree with duplicate objects (same QName, same value, different object). Using this
40 * utility, such objects will end up reusing the same object, preventing this overhead.
43 public final class LeafInterner {
44 private static final Logger LOG = LoggerFactory.getLogger(LeafInterner.class);
45 private static final Interner<Object> INTERNER = Interners.newWeakInterner();
47 private LeafInterner() {
51 private static <T extends LeafNode<?>> T intern(final T sample) {
52 @SuppressWarnings("unchecked")
53 final T ret = (T) INTERNER.intern(sample);
54 LOG.trace("Interned object {} to {}", sample, ret);
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, if applicable
65 public static <T extends LeafNode<?>> @NonNull Optional<Interner<T>> forSchema(
66 final @Nullable LeafSchemaNode schema) {
67 if (schema != null && isLowCardinality(schema.getType())) {
68 return Optional.of(LeafInterner::intern);
71 return Optional.empty();
74 private static boolean isLowCardinality(final TypeDefinition<?> type) {
75 return type instanceof BooleanTypeDefinition
76 || type instanceof EmptyTypeDefinition
77 || type instanceof EnumTypeDefinition
78 || type instanceof IdentityrefTypeDefinition
79 || type instanceof Int8TypeDefinition
80 || type instanceof Uint8TypeDefinition;