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 javax.annotation.Nonnull;
14 import javax.annotation.Nullable;
15 import org.opendaylight.yangtools.yang.data.api.schema.LeafSetEntryNode;
16 import org.opendaylight.yangtools.yang.model.api.LeafListSchemaNode;
17 import org.opendaylight.yangtools.yang.model.api.TypeDefinition;
18 import org.opendaylight.yangtools.yang.model.api.type.BooleanTypeDefinition;
19 import org.opendaylight.yangtools.yang.model.api.type.EnumTypeDefinition;
20 import org.opendaylight.yangtools.yang.model.api.type.IdentityrefTypeDefinition;
21 import org.slf4j.Logger;
22 import org.slf4j.LoggerFactory;
25 * Utility class for sharing instances of {@link LeafSetEntryNode}s which have low cardinality -- e.g. those which hold
26 * 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.
34 * The theory here is that we tend to have a large number (100K+) of entries in a few places, which could end up hogging
35 * the heap retained via the DataTree with duplicate objects (same QName, same value, different object). Using this
36 * utility, such objects will end up reusing the same object, preventing this overhead.
39 public final class LeafsetEntryInterner {
40 private static final Logger LOG = LoggerFactory.getLogger(LeafsetEntryInterner.class);
41 private static final LeafsetEntryInterner INSTANCE = new LeafsetEntryInterner();
42 private static final Interner<Object> INTERNER = Interners.newWeakInterner();
44 private LeafsetEntryInterner() {
48 @SuppressWarnings("static-method")
49 public <T extends LeafSetEntryNode<?>> T intern(@Nonnull final T sample) {
50 if (!sample.getAttributes().isEmpty()) {
51 // Non-empty attributes, do not intern
56 * We do not perform type checks here as they are implied by #forSchema(LeafListSchemaNode). Any misuse can
57 * result in inappropriate candidates being interned, but the alternative would be quite a bit slower.
59 @SuppressWarnings("unchecked")
60 final T ret = (T) INTERNER.intern(sample);
61 LOG.trace("Interned object {} to {}", sample, ret);
66 * Return a {@link LeafsetEntryInterner} for a particular schema. Interner instances must be used only for leafset
67 * entries for that particular schema, otherwise they may produce unexpected results.
69 * @param schema Schema of the parent leaf set
70 * @return An interner instance, or null if the leafset's type should not be interned.
72 @Nullable public static LeafsetEntryInterner forSchema(@Nullable final LeafListSchemaNode schema) {
74 final TypeDefinition<?> type = schema.getType();
75 if (type instanceof BooleanTypeDefinition || type instanceof EnumTypeDefinition
76 || type instanceof IdentityrefTypeDefinition) {