sortingiterator.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: SortingIterator.java,v 1.2.4.1 2005/09/06 10:23:32 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;

/**
 * @author Jacek Ambroziak
 * @author Santiago Pericas-Geertsen
 * @author Morten Jorgensen
 */
public final class SortingIterator extends DTMAxisIteratorBase {
    private final static int INIT_DATA_SIZE = 16;

    private DTMAxisIterator _source;
    private NodeSortRecordFactory _factory;

    private NodeSortRecord[] _data;
    private int _free = 0;
    private int _current;	// index in _nodes of the next node to try

    public SortingIterator(DTMAxisIterator source, 
			   NodeSortRecordFactory factory) {
	_source = source;
	_factory = factory;
    }

    public int next() {
	return _current < _free ? _data[_current++].getNode() : END;
    }
	
    public DTMAxisIterator setStartNode(int node) {
	try {
	    _source.setStartNode(_startNode = node);
	    _data = new NodeSortRecord[INIT_DATA_SIZE];
	    _free = 0;

	    // gather all nodes from the source iterator
	    while ((node = _source.next()) != END) {
		addRecord(_factory.makeNodeSortRecord(node,_free));
	    }
	    // now sort the records
	    quicksort(0, _free - 1);

	    _current = 0;
	    return this;
	}
	catch (Exception e) {
	    return this;
	}
    }
	
    public int getPosition() {
	return _current == 0 ? 1 : _current;
    }

    public int getLast() {
	return _free;
    }

    public void setMark() {
	_source.setMark();
	_markedNode = _current;
    }

    public void gotoMark() {
	_source.gotoMark();
	_current = _markedNode;
    }
    
    /**
     * Clone a <code>SortingIterator</code> by cloning its source
     * iterator and then sharing the factory and the array of
     * <code>NodeSortRecords</code>.
     */
    public DTMAxisIterator cloneIterator() {
	try {
	    final SortingIterator clone = (SortingIterator) super.clone();
	    clone._source = _source.cloneIterator();  
	    clone._factory = _factory;		// shared between clones
	    clone._data = _data;		// shared between clones
	    clone._free = _free;
	    clone._current = _current;
	    clone.setRestartable(false);
	    return clone.reset();
	}
	catch (CloneNotSupportedException e) {
	    BasisLibrary.runTimeError(BasisLibrary.ITERATOR_CLONE_ERR,
				      e.toString());
	    return null;
	}
    }

    private void addRecord(NodeSortRecord record) {
	if (_free == _data.length) {
	    NodeSortRecord[] newArray = new NodeSortRecord[_data.length * 2];
	    System.arraycopy(_data, 0, newArray, 0, _free);
	    _data = newArray;
	}
	_data[_free++] = record;
    }

    private void quicksort(int p, int r) {
	while (p < r) {
	    final int q = partition(p, r);
	    quicksort(p, q);
	    p = q + 1;
	}
    }
    
    private int partition(int p, int r) {
	final NodeSortRecord x = _data[(p + r) >>> 1];
	int i = p - 1;
	int j = r + 1;
	while (true) {
	    while (x.compareTo(_data[--j]) < 0);
	    while (x.compareTo(_data[++i]) > 0);
	    if (i < j) {
		final NodeSortRecord t = _data[i];
		_data[i] = _data[j];
		_data[j] = t;
	    }
	    else {
		return(j);
	    }
	}
    }
}