001/////////////////////////////////////////////////////////////////////////////////////////////// 002// checkstyle: Checks Java source code and other text files for adherence to a set of rules. 003// Copyright (C) 2001-2023 the original author or authors. 004// 005// This library is free software; you can redistribute it and/or 006// modify it under the terms of the GNU Lesser General Public 007// License as published by the Free Software Foundation; either 008// version 2.1 of the License, or (at your option) any later version. 009// 010// This library is distributed in the hope that it will be useful, 011// but WITHOUT ANY WARRANTY; without even the implied warranty of 012// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 013// Lesser General Public License for more details. 014// 015// You should have received a copy of the GNU Lesser General Public 016// License along with this library; if not, write to the Free Software 017// Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA 018/////////////////////////////////////////////////////////////////////////////////////////////// 019 020package com.puppycrawl.tools.checkstyle.xpath.iterators; 021 022import net.sf.saxon.om.AxisInfo; 023import net.sf.saxon.om.NodeInfo; 024import net.sf.saxon.tree.iter.AxisIterator; 025 026/** 027 * Recursive-free implementation of the preceding axis iterator. 028 */ 029public class PrecedingIterator implements AxisIterator { 030 /** 031 * Ancestor axis iterator. 032 */ 033 private final AxisIterator ancestorEnum; 034 /** 035 * Preceding-sibling axis iterator. 036 */ 037 private AxisIterator previousSiblingEnum; 038 /** 039 * Descendant axis iterator. 040 */ 041 private AxisIterator descendantEnum; 042 043 /** 044 * Create an iterator over the "preceding" axis. 045 * 046 * @param start the initial context node. 047 */ 048 public PrecedingIterator(NodeInfo start) { 049 ancestorEnum = start.iterateAxis(AxisInfo.ANCESTOR); 050 previousSiblingEnum = start.iterateAxis(AxisInfo.PRECEDING_SIBLING); 051 descendantEnum = null; 052 } 053 054 /** 055 * Get the next item in the sequence. 056 * 057 * @return the next Item. If there are no more nodes, return null. 058 */ 059 @Override 060 public NodeInfo next() { 061 NodeInfo result = null; 062 063 while (result == null) { 064 if (descendantEnum != null) { 065 result = descendantEnum.next(); 066 } 067 068 if (result == null && previousSiblingEnum != null) { 069 result = previousSiblingEnum.next(); 070 if (result == null) { 071 previousSiblingEnum = null; 072 } 073 else { 074 descendantEnum = new ReverseDescendantIterator(result); 075 } 076 } 077 078 if (result == null) { 079 result = ancestorEnum.next(); 080 if (result == null) { 081 break; 082 } 083 previousSiblingEnum = result.iterateAxis(AxisInfo.PRECEDING_SIBLING); 084 } 085 } 086 return result; 087 } 088}