1 ///////////////////////////////////////////////////////////////////////////////////////////////
2 // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
3 // Copyright (C) 2001-2024 the original author or authors.
4 //
5 // This library is free software; you can redistribute it and/or
6 // modify it under the terms of the GNU Lesser General Public
7 // License as published by the Free Software Foundation; either
8 // version 2.1 of the License, or (at your option) any later version.
9 //
10 // This library is distributed in the hope that it will be useful,
11 // but WITHOUT ANY WARRANTY; without even the implied warranty of
12 // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 // Lesser General Public License for more details.
14 //
15 // You should have received a copy of the GNU Lesser General Public
16 // License along with this library; if not, write to the Free Software
17 // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18 ///////////////////////////////////////////////////////////////////////////////////////////////
19
20 package com.puppycrawl.tools.checkstyle.xpath.iterators;
21
22 import java.util.LinkedList;
23 import java.util.Queue;
24
25 import net.sf.saxon.om.AxisInfo;
26 import net.sf.saxon.om.NodeInfo;
27 import net.sf.saxon.tree.iter.AxisIterator;
28 import net.sf.saxon.tree.iter.SingleNodeIterator;
29
30 /**
31 * Recursive-free implementation of the descendant axis iterator.
32 */
33 public class DescendantIterator implements AxisIterator {
34
35 /**
36 * Enum defines starting node for iterator.
37 */
38 public enum StartWith {
39 /** Start with current node. */
40 CURRENT_NODE,
41 /** Omit current node and start with child nodes. */
42 CHILDREN,
43 }
44
45 /**
46 * Queue for sibling nodes.
47 */
48 private final Queue<NodeInfo> queue = new LinkedList<>();
49 /**
50 * Descendant axis iterator.
51 */
52 private AxisIterator descendantEnum;
53
54 /**
55 * Create an iterator over the "descendant" axis.
56 *
57 * @param start the initial context node.
58 * @param startWith mode of the iterator, see {@link StartWith}.
59 */
60 public DescendantIterator(NodeInfo start, StartWith startWith) {
61 if (startWith == StartWith.CURRENT_NODE) {
62 descendantEnum = SingleNodeIterator.makeIterator(start);
63 }
64 else if (startWith == StartWith.CHILDREN) {
65 descendantEnum = start.iterateAxis(AxisInfo.CHILD);
66 }
67 }
68
69 /**
70 * Get the next item in the sequence.
71 *
72 * @return the next Item. If there are no more nodes, return null.
73 */
74 @Override
75 public NodeInfo next() {
76 NodeInfo result = null;
77 do {
78 if (descendantEnum == null) {
79 if (queue.isEmpty()) {
80 break;
81 }
82 descendantEnum = queue.poll().iterateAxis(AxisInfo.CHILD);
83 }
84 else {
85 result = descendantEnum.next();
86 if (result == null) {
87 descendantEnum = null;
88 }
89 }
90 } while (result == null);
91
92 if (result != null) {
93 queue.add(result);
94 }
95 return result;
96 }
97 }