1 /*
2 * Licensed to the Apache Software Foundation (ASF) under one
3 * or more contributor license agreements. See the NOTICE file
4 * distributed with this work for additional information
5 * regarding copyright ownership. The ASF licenses this file
6 * to you under the Apache License, Version 2.0 (the
7 * "License"); you may not use this file except in compliance
8 * with the License. You may obtain a copy of the License at
9 *
10 * http://www.apache.org/licenses/LICENSE-2.0
11 *
12 * Unless required by applicable law or agreed to in writing,
13 * software distributed under the License is distributed on an
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
15 * KIND, either express or implied. See the License for the
16 * specific language governing permissions and limitations
17 * under the License.
18 */
19 package org.eclipse.aether.util.graph.visitor;
20
21 import java.util.IdentityHashMap;
22 import java.util.Map;
23 import java.util.function.Consumer;
24
25 import org.eclipse.aether.graph.DependencyNode;
26 import org.eclipse.aether.graph.DependencyVisitor;
27
28 import static java.util.Objects.requireNonNull;
29
30 /**
31 * Abstract base class for dependency tree traverses that feed {@link Consumer<DependencyNode>}.
32 *
33 * @since 2.0.0
34 */
35 abstract class AbstractDependencyNodeConsumerVisitor implements DependencyVisitor {
36 protected final Consumer<DependencyNode> nodeConsumer;
37
38 private final Map<DependencyNode, Object> visitedNodes;
39
40 protected AbstractDependencyNodeConsumerVisitor(Consumer<DependencyNode> nodeConsumer) {
41 this.nodeConsumer = requireNonNull(nodeConsumer);
42 this.visitedNodes = new IdentityHashMap<>(512);
43 }
44
45 /**
46 * Marks the specified node as being visited and determines whether the node has been visited before.
47 *
48 * @param node The node being visited, must not be {@code null}.
49 * @return {@code true} if the node has not been visited before, {@code false} if the node was already visited.
50 */
51 protected boolean setVisited(DependencyNode node) {
52 return visitedNodes.put(node, Boolean.TRUE) == null;
53 }
54
55 @Override
56 public abstract boolean visitEnter(DependencyNode node);
57
58 @Override
59 public abstract boolean visitLeave(DependencyNode node);
60 }