001 /*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements. See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership. The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 * http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018 /*
019 * $Id: HasPositionalPredChecker.java 468655 2006-10-28 07:12:06Z minchau $
020 */
021 package org.apache.xpath.axes;
022
023 import org.apache.xpath.Expression;
024 import org.apache.xpath.ExpressionOwner;
025 import org.apache.xpath.XPathVisitor;
026 import org.apache.xpath.functions.FuncLast;
027 import org.apache.xpath.functions.FuncPosition;
028 import org.apache.xpath.functions.Function;
029 import org.apache.xpath.objects.XNumber;
030 import org.apache.xpath.operations.Div;
031 import org.apache.xpath.operations.Minus;
032 import org.apache.xpath.operations.Mod;
033 import org.apache.xpath.operations.Mult;
034 import org.apache.xpath.operations.Plus;
035 import org.apache.xpath.operations.Quo;
036 import org.apache.xpath.operations.Variable;
037
038 public class HasPositionalPredChecker extends XPathVisitor
039 {
040 private boolean m_hasPositionalPred = false;
041 private int m_predDepth = 0;
042
043 /**
044 * Process the LocPathIterator to see if it contains variables
045 * or functions that may make it context dependent.
046 * @param path LocPathIterator that is assumed to be absolute, but needs checking.
047 * @return true if the path is confirmed to be absolute, false if it
048 * may contain context dependencies.
049 */
050 public static boolean check(LocPathIterator path)
051 {
052 HasPositionalPredChecker hppc = new HasPositionalPredChecker();
053 path.callVisitors(null, hppc);
054 return hppc.m_hasPositionalPred;
055 }
056
057 /**
058 * Visit a function.
059 * @param owner The owner of the expression, to which the expression can
060 * be reset if rewriting takes place.
061 * @param func The function reference object.
062 * @return true if the sub expressions should be traversed.
063 */
064 public boolean visitFunction(ExpressionOwner owner, Function func)
065 {
066 if((func instanceof FuncPosition) ||
067 (func instanceof FuncLast))
068 m_hasPositionalPred = true;
069 return true;
070 }
071
072 // /**
073 // * Visit a variable reference.
074 // * @param owner The owner of the expression, to which the expression can
075 // * be reset if rewriting takes place.
076 // * @param var The variable reference object.
077 // * @return true if the sub expressions should be traversed.
078 // */
079 // public boolean visitVariableRef(ExpressionOwner owner, Variable var)
080 // {
081 // m_hasPositionalPred = true;
082 // return true;
083 // }
084
085 /**
086 * Visit a predicate within a location path. Note that there isn't a
087 * proper unique component for predicates, and that the expression will
088 * be called also for whatever type Expression is.
089 *
090 * @param owner The owner of the expression, to which the expression can
091 * be reset if rewriting takes place.
092 * @param pred The predicate object.
093 * @return true if the sub expressions should be traversed.
094 */
095 public boolean visitPredicate(ExpressionOwner owner, Expression pred)
096 {
097 m_predDepth++;
098
099 if(m_predDepth == 1)
100 {
101 if((pred instanceof Variable) ||
102 (pred instanceof XNumber) ||
103 (pred instanceof Div) ||
104 (pred instanceof Plus) ||
105 (pred instanceof Minus) ||
106 (pred instanceof Mod) ||
107 (pred instanceof Quo) ||
108 (pred instanceof Mult) ||
109 (pred instanceof org.apache.xpath.operations.Number) ||
110 (pred instanceof Function))
111 m_hasPositionalPred = true;
112 else
113 pred.callVisitors(owner, this);
114 }
115
116 m_predDepth--;
117
118 // Don't go have the caller go any further down the subtree.
119 return false;
120 }
121
122
123 }
124