BasicTestIterator.java revision 9f8118474e9513f7a5b7d2a05e4a0fb15d1a6569
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: BasicTestIterator.java 469314 2006-10-30 23:31:59Z minchau $ 20 */ 21package org.apache.xpath.axes; 22 23import org.apache.xml.dtm.DTM; 24import org.apache.xml.dtm.DTMFilter; 25import org.apache.xml.dtm.DTMIterator; 26import org.apache.xml.utils.PrefixResolver; 27import org.apache.xpath.compiler.Compiler; 28import org.apache.xpath.compiler.OpMap; 29 30/** 31 * Base for iterators that handle predicates. Does the basic next 32 * node logic, so all the derived iterator has to do is get the 33 * next node. 34 */ 35public abstract class BasicTestIterator extends LocPathIterator 36{ 37 static final long serialVersionUID = 3505378079378096623L; 38 /** 39 * Create a LocPathIterator object. 40 * 41 * @param nscontext The namespace context for this iterator, 42 * should be OK if null. 43 */ 44 protected BasicTestIterator() 45 { 46 } 47 48 49 /** 50 * Create a LocPathIterator object. 51 * 52 * @param nscontext The namespace context for this iterator, 53 * should be OK if null. 54 */ 55 protected BasicTestIterator(PrefixResolver nscontext) 56 { 57 58 super(nscontext); 59 } 60 61 /** 62 * Create a LocPathIterator object, including creation 63 * of step walkers from the opcode list, and call back 64 * into the Compiler to create predicate expressions. 65 * 66 * @param compiler The Compiler which is creating 67 * this expression. 68 * @param opPos The position of this iterator in the 69 * opcode list from the compiler. 70 * 71 * @throws javax.xml.transform.TransformerException 72 */ 73 protected BasicTestIterator(Compiler compiler, int opPos, int analysis) 74 throws javax.xml.transform.TransformerException 75 { 76 super(compiler, opPos, analysis, false); 77 78 int firstStepPos = OpMap.getFirstChildPos(opPos); 79 int whatToShow = compiler.getWhatToShow(firstStepPos); 80 81 if ((0 == (whatToShow 82 & (DTMFilter.SHOW_ATTRIBUTE 83 | DTMFilter.SHOW_NAMESPACE 84 | DTMFilter.SHOW_ELEMENT 85 | DTMFilter.SHOW_PROCESSING_INSTRUCTION))) 86 || (whatToShow == DTMFilter.SHOW_ALL)) 87 initNodeTest(whatToShow); 88 else 89 { 90 initNodeTest(whatToShow, compiler.getStepNS(firstStepPos), 91 compiler.getStepLocalName(firstStepPos)); 92 } 93 initPredicateInfo(compiler, firstStepPos); 94 } 95 96 /** 97 * Create a LocPathIterator object, including creation 98 * of step walkers from the opcode list, and call back 99 * into the Compiler to create predicate expressions. 100 * 101 * @param compiler The Compiler which is creating 102 * this expression. 103 * @param opPos The position of this iterator in the 104 * opcode list from the compiler. 105 * @param shouldLoadWalkers True if walkers should be 106 * loaded, or false if this is a derived iterator and 107 * it doesn't wish to load child walkers. 108 * 109 * @throws javax.xml.transform.TransformerException 110 */ 111 protected BasicTestIterator( 112 Compiler compiler, int opPos, int analysis, boolean shouldLoadWalkers) 113 throws javax.xml.transform.TransformerException 114 { 115 super(compiler, opPos, analysis, shouldLoadWalkers); 116 } 117 118 119 /** 120 * Get the next node via getNextXXX. Bottlenecked for derived class override. 121 * @return The next node on the axis, or DTM.NULL. 122 */ 123 protected abstract int getNextNode(); 124 125 /** 126 * Returns the next node in the set and advances the position of the 127 * iterator in the set. After a NodeIterator is created, the first call 128 * to nextNode() returns the first node in the set. 129 * 130 * @return The next <code>Node</code> in the set being iterated over, or 131 * <code>null</code> if there are no more members in that set. 132 */ 133 public int nextNode() 134 { 135 if(m_foundLast) 136 { 137 m_lastFetched = DTM.NULL; 138 return DTM.NULL; 139 } 140 141 if(DTM.NULL == m_lastFetched) 142 { 143 resetProximityPositions(); 144 } 145 146 int next; 147 148 org.apache.xpath.VariableStack vars; 149 int savedStart; 150 if (-1 != m_stackFrame) 151 { 152 vars = m_execContext.getVarStack(); 153 154 // These three statements need to be combined into one operation. 155 savedStart = vars.getStackFrame(); 156 157 vars.setStackFrame(m_stackFrame); 158 } 159 else 160 { 161 // Yuck. Just to shut up the compiler! 162 vars = null; 163 savedStart = 0; 164 } 165 166 try 167 { 168 do 169 { 170 next = getNextNode(); 171 172 if (DTM.NULL != next) 173 { 174 if(DTMIterator.FILTER_ACCEPT == acceptNode(next)) 175 break; 176 else 177 continue; 178 } 179 else 180 break; 181 } 182 while (next != DTM.NULL); 183 184 if (DTM.NULL != next) 185 { 186 m_pos++; 187 return next; 188 } 189 else 190 { 191 m_foundLast = true; 192 193 return DTM.NULL; 194 } 195 } 196 finally 197 { 198 if (-1 != m_stackFrame) 199 { 200 // These two statements need to be combined into one operation. 201 vars.setStackFrame(savedStart); 202 } 203 } 204 } 205 206 /** 207 * Get a cloned Iterator that is reset to the beginning 208 * of the query. 209 * 210 * @return A cloned NodeIterator set of the start of the query. 211 * 212 * @throws CloneNotSupportedException 213 */ 214 public DTMIterator cloneWithReset() throws CloneNotSupportedException 215 { 216 217 ChildTestIterator clone = (ChildTestIterator) super.cloneWithReset(); 218 219 clone.resetProximityPositions(); 220 221 return clone; 222 } 223 224 225} 226 227