matchingiterator.java

java1.6众多例子参考

/*
 * Copyright 2001-2004 The Apache Software Foundation.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
/*
 * $Id: MatchingIterator.java,v 1.2.4.1 2005/09/06 09:22:07 pvedula Exp $
 */

package com.sun.org.apache.xalan.internal.xsltc.dom;

import com.sun.org.apache.xalan.internal.xsltc.runtime.BasisLibrary;
import com.sun.org.apache.xml.internal.dtm.DTMAxisIterator;
import com.sun.org.apache.xml.internal.dtm.ref.DTMAxisIteratorBase;

/**
 * This is a special kind of iterator that takes a source iterator and a 
 * node N. If initialized with a node M (the parent of N) it computes the 
 * position of N amongst the children of M. This position can be obtained 
 * by calling getPosition().
 * It is an iterator even though next() will never be called. It is used to
 * match patterns with a single predicate like:
 *
 *    BOOK[position() = last()]
 *
 * In this example, the source iterator will return elements of type BOOK, 
 * a call to position() will return the position of N. Notice that because 
 * of the way the pattern matching is implemented, N will always be a node 
 * in the source since (i) it is a BOOK or the test sequence would not be 
 * considered and (ii) the source iterator is initialized with M which is 
 * the parent of N. Also, and still in this example, a call to last() will 
 * return the number of elements in the source (i.e. the number of BOOKs).
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 */
public final class MatchingIterator extends DTMAxisIteratorBase {

    /**
     * A reference to a source iterator.
     */
    private DTMAxisIterator _source;

    /**
     * The node to match.
     */
    private final int _match;

    public MatchingIterator(int match, DTMAxisIterator source) {
	_source = source;
	_match = match;
    }


    public void setRestartable(boolean isRestartable) {
	_isRestartable = isRestartable;
	_source.setRestartable(isRestartable);
    }

    public DTMAxisIterator cloneIterator() {

	try {
	    final MatchingIterator clone = (MatchingIterator) super.clone();
	    clone._source = _source.cloneIterator();
	    clone._isRestartable = false;
	    return clone.reset();
	}
	catch (CloneNotSupportedException e) {
	    BasisLibrary.runTimeError(BasisLibrary.ITERATOR_CLONE_ERR,
				      e.toString());
	    return null;
	}
    }
    
    public DTMAxisIterator setStartNode(int node) {
	if (_isRestartable) {
	    // iterator is not a clone
	    _source.setStartNode(node);

	    // Calculate the position of the node in the set
	    _position = 1;
	    while ((node = _source.next()) != END && node != _match) {
		_position++;
	    }
	}
	return this;
    }

    public DTMAxisIterator reset() {
	_source.reset();
	return resetPosition();
    }
    
    public int next() {
	return _source.next();
    }
	
    public int getLast() {
        if (_last == -1) {
            _last = _source.getLast();
        }
        return _last;
    }

    public int getPosition() {
	return _position;
    }

    public void setMark() {
	_source.setMark();
    }

    public void gotoMark() {
	_source.gotoMark();
    }
}