1 package org.eclipse.aether.util.graph.visitor;
2
3 /*
4 * Licensed to the Apache Software Foundation (ASF) under one
5 * or more contributor license agreements. See the NOTICE file
6 * distributed with this work for additional information
7 * regarding copyright ownership. The ASF licenses this file
8 * to you under the Apache License, Version 2.0 (the
9 * "License"); you may not use this file except in compliance
10 * with the License. You may obtain a copy of the License at
11 *
12 * http://www.apache.org/licenses/LICENSE-2.0
13 *
14 * Unless required by applicable law or agreed to in writing,
15 * software distributed under the License is distributed on an
16 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
17 * KIND, either express or implied. See the License for the
18 * specific language governing permissions and limitations
19 * under the License.
20 */
21
22 import org.eclipse.aether.graph.DependencyNode;
23
24 /**
25 * Generates a sequence of dependency nodes from a dependeny graph by traversing the graph in postorder. This visitor
26 * visits each node exactly once regardless how many paths within the dependency graph lead to the node such that the
27 * resulting node sequence is free of duplicates.
28 */
29 public final class PostorderNodeListGenerator
30 extends AbstractDepthFirstNodeListGenerator
31 {
32
33 private final Stack<Boolean> visits;
34
35 /**
36 * Creates a new postorder list generator.
37 */
38 public PostorderNodeListGenerator()
39 {
40 visits = new Stack<>();
41 }
42
43 @Override
44 public boolean visitEnter( DependencyNode node )
45 {
46 boolean visited = !setVisited( node );
47
48 visits.push( visited );
49
50 if ( visited )
51 {
52 return false;
53 }
54
55 return true;
56 }
57
58 @Override
59 public boolean visitLeave( DependencyNode node )
60 {
61 Boolean visited = visits.pop();
62
63 if ( visited )
64 {
65 return true;
66 }
67
68 if ( node.getDependency() != null )
69 {
70 nodes.add( node );
71 }
72
73 return true;
74 }
75
76 }