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 "License"); 7 * you may not use this file except in compliance with the License. 8 * 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, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 /* 19 * $Id: HasPositionalPredChecker.java 468655 2006-10-28 07:12:06Z minchau $ 20 */ 21 package org.apache.xpath.axes; 22 23 import org.apache.xpath.Expression; 24 import org.apache.xpath.ExpressionOwner; 25 import org.apache.xpath.XPathVisitor; 26 import org.apache.xpath.functions.FuncLast; 27 import org.apache.xpath.functions.FuncPosition; 28 import org.apache.xpath.functions.Function; 29 import org.apache.xpath.objects.XNumber; 30 import org.apache.xpath.operations.Div; 31 import org.apache.xpath.operations.Minus; 32 import org.apache.xpath.operations.Mod; 33 import org.apache.xpath.operations.Mult; 34 import org.apache.xpath.operations.Plus; 35 import org.apache.xpath.operations.Quo; 36 import org.apache.xpath.operations.Variable; 37 38 public class HasPositionalPredChecker extends XPathVisitor 39 { 40 private boolean m_hasPositionalPred = false; 41 private int m_predDepth = 0; 42 43 /** 44 * Process the LocPathIterator to see if it contains variables 45 * or functions that may make it context dependent. 46 * @param path LocPathIterator that is assumed to be absolute, but needs checking. 47 * @return true if the path is confirmed to be absolute, false if it 48 * may contain context dependencies. 49 */ 50 public static boolean check(LocPathIterator path) 51 { 52 HasPositionalPredChecker hppc = new HasPositionalPredChecker(); 53 path.callVisitors(null, hppc); 54 return hppc.m_hasPositionalPred; 55 } 56 57 /** 58 * Visit a function. 59 * @param owner The owner of the expression, to which the expression can 60 * be reset if rewriting takes place. 61 * @param func The function reference object. 62 * @return true if the sub expressions should be traversed. 63 */ 64 public boolean visitFunction(ExpressionOwner owner, Function func) 65 { 66 if((func instanceof FuncPosition) || 67 (func instanceof FuncLast)) 68 m_hasPositionalPred = true; 69 return true; 70 } 71 72 // /** 73 // * Visit a variable reference. 74 // * @param owner The owner of the expression, to which the expression can 75 // * be reset if rewriting takes place. 76 // * @param var The variable reference object. 77 // * @return true if the sub expressions should be traversed. 78 // */ 79 // public boolean visitVariableRef(ExpressionOwner owner, Variable var) 80 // { 81 // m_hasPositionalPred = true; 82 // return true; 83 // } 84 85 /** 86 * Visit a predicate within a location path. Note that there isn't a 87 * proper unique component for predicates, and that the expression will 88 * be called also for whatever type Expression is. 89 * 90 * @param owner The owner of the expression, to which the expression can 91 * be reset if rewriting takes place. 92 * @param pred The predicate object. 93 * @return true if the sub expressions should be traversed. 94 */ 95 public boolean visitPredicate(ExpressionOwner owner, Expression pred) 96 { 97 m_predDepth++; 98 99 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 } 124 125
