001    /*
002     * Licensed to the Apache Software Foundation (ASF) under one or more
003     * contributor license agreements.  See the NOTICE file distributed with
004     * this work for additional information regarding copyright ownership.
005     * The ASF licenses this file to You under the Apache License, Version 2.0
006     * (the "License"); you may not use this file except in compliance with
007     * the License.  You may obtain a copy of the License at
008     *
009     *     http://www.apache.org/licenses/LICENSE-2.0
010     *
011     * Unless required by applicable law or agreed to in writing, software
012     * distributed under the License is distributed on an "AS IS" BASIS,
013     * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
014     * See the License for the specific language governing permissions and
015     * limitations under the License.
016     */
017    package org.apache.commons.jxpath.ri.axes;
018    
019    import org.apache.commons.jxpath.Pointer;
020    import org.apache.commons.jxpath.ri.EvalContext;
021    import org.apache.commons.jxpath.ri.compiler.NodeTest;
022    import org.apache.commons.jxpath.ri.model.NodeIterator;
023    import org.apache.commons.jxpath.ri.model.NodePointer;
024    
025    /**
026     * EvalContext that can walk the "child::", "following-sibling::" and
027     * "preceding-sibling::" axes.
028     *
029     * @author Dmitri Plotnikov
030     * @version $Revision: 652903 $ $Date: 2008-05-02 15:46:32 -0500 (Fri, 02 May 2008) $
031     */
032    public class ChildContext extends EvalContext {
033        private NodeTest nodeTest;
034        private boolean startFromParentLocation;
035        private boolean reverse;
036        private NodeIterator iterator;
037    
038        /**
039         * Create a new ChildContext.
040         * @param parentContext parent EvalContext
041         * @param nodeTest NodeTest
042         * @param startFromParentLocation whether to start from parent location
043         * @param reverse whether to iterate in reverse
044         */
045        public ChildContext(EvalContext parentContext, NodeTest nodeTest,
046                boolean startFromParentLocation, boolean reverse) {
047            super(parentContext);
048            this.nodeTest = nodeTest;
049            this.startFromParentLocation = startFromParentLocation;
050            this.reverse = reverse;
051        }
052    
053        public NodePointer getCurrentNodePointer() {
054            if (position == 0 && !setPosition(1)) {
055                return null;
056            }
057            return iterator == null ? null : iterator.getNodePointer();
058        }
059    
060        /**
061         * This method is called on the last context on the path when only
062         * one value is needed.  Note that this will return the whole property,
063         * even if it is a collection. It will not extract the first element
064         * of the collection.  For example, "books" will return the collection
065         * of books rather than the first book from that collection.
066         * @return Pointer
067         */
068        public Pointer getSingleNodePointer() {
069            if (position == 0) {
070                while (nextSet()) {
071                    prepare();
072                    if (iterator == null) {
073                        return null;
074                    }
075                    // See if there is a property there, singular or collection
076                    NodePointer pointer = iterator.getNodePointer();
077                    if (pointer != null) {
078                        return pointer;
079                    }
080                }
081                return null;
082            }
083            return getCurrentNodePointer();
084        }
085    
086        public boolean nextNode() {
087            return setPosition(getCurrentPosition() + 1);
088        }
089    
090        public void reset() {
091            super.reset();
092            iterator = null;
093        }
094    
095        public boolean setPosition(int position) {
096            int oldPosition = getCurrentPosition();
097            super.setPosition(position);
098            if (oldPosition == 0) {
099                prepare();
100            }
101            return iterator == null ? false : iterator.setPosition(position);
102        }
103    
104        /**
105         * Allocates a PropertyIterator.
106         */
107        private void prepare() {
108            NodePointer parent = parentContext.getCurrentNodePointer();
109            if (parent == null) {
110                return;
111            }
112            NodePointer useParent = startFromParentLocation ? parent.getParent() : parent;
113            iterator = useParent.childIterator(nodeTest, reverse,
114                    startFromParentLocation ? parent : null);
115        }
116    }