src/org/apache/xalan/xsltc/dom/DupFilterIterator.java

/*
 * @(#)$Id$
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 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 2001 The Apache Software Foundation.  All rights
 * reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 *
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in
 *    the documentation and/or other materials provided with the
 *    distribution.
 *
 * 3. The end-user documentation included with the redistribution,
 *    if any, must include the following acknowledgment:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.apache.org/)."
 *    Alternately, this acknowledgment may appear in the software itself,
 *    if and wherever such third-party acknowledgments normally appear.
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 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
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 * 5. Products derived from this software may not be called "Apache",
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 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
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 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 * ====================================================================
 *
 * This software consists of voluntary contributions made by many
 * individuals on behalf of the Apache Software Foundation and was
 * originally based on software copyright (c) 2001, Sun
 * Microsystems., http://www.sun.com.  For more
 * information on the Apache Software Foundation, please see
 * <http://www.apache.org/>.
 *
 * @author G. Todd Miller 
 *
 */

package org.apache.xalan.xsltc.dom;

import org.apache.xalan.xsltc.DOM;
import org.apache.xalan.xsltc.NodeIterator;
import org.apache.xalan.xsltc.TransletException;

public final class DupFilterIterator extends NodeIteratorBase {

    private final static int INIT_DATA_SIZE = 16;

    private final NodeIterator _source; // the source iterator
    private int[] _data = null;         // cached nodes from the source
    private int _last = 0;              // the number of nodes in this iterator
    private int _current = 0;

    /**
     * Creates a new duplicate filter iterator based on an existing iterator.
     * This iterator should be used with union expressions and other complex
     * iterator combinations (like 'get me the parents of all child node in
     * the dom' sort of thing). The iterator is also used to cache node-sets
     * returned by id() and key() iterators.
     * @param source The iterator this iterator will get its nodes from
     */
    public DupFilterIterator(NodeIterator source) {
	// Save a reference to the source iterator
	_source = source;

	// Cache contents of id() or key() index right away. Necessary for
	// union expressions containing multiple calls to the same index, and
	// correct as well since start-node is irrelevant for id()/key() exrp.
	if (source instanceof KeyIndex) setStartNode(DOM.ROOTNODE);
    }

    /**
     * Returns the next node in this iterator - excludes duplicates.
     * @return The next node in this iterator
     */
    public int next() {
	return _current < _last ? _data[_current++] : END;
    }

    /**
     * Set the start node for this iterator
     * @param node The start node
     * @return A reference to this node iterator
     */
    public NodeIterator setStartNode(int node) {
	// KeyIndex iterators are always relative to the root node, so there
	// is never any point in re-reading the iterator (and we SHOULD NOT).
	if ((_source instanceof KeyIndex) && (_data != null)) return this;

	// If the _data array is populated, and the current start node is
	// equal to the new start node, we know we already have what we need.
	if ((_data == null) || (node != _startNode)) {

	    _startNode = node;
	    _last = 0;
	    _source.setStartNode(node);
	    _data = new int[INIT_DATA_SIZE];

	    // Gather all nodes from the source iterator, eliminate dups
	    while ((node = _source.next()) != END) {
		if (_last == _data.length) {
		    int[] newArray = new int[_data.length * 2];
		    System.arraycopy(_data, 0, newArray, 0, _last);
		    _data = newArray;
		}
		if (!isDup(node)) _data[_last++] = node;
	    }
	}

	_current = 0;  // set to beginning 
	return this;
    }

    /**
     * Check if a node is already in the _data array. The nodes should be in
     * document order or reverse document order, so we may be able to use
     * binary search here.
     */
    private boolean isDup(int node) {
	boolean retval = false;
	int size = _data.length;
	for (int i=0; i<size; i++) {
	    if (_data[i] == node) {
		retval = true; break;
	    }
	}
	return retval;
    }

    /**
     * Returns the current position of the iterator. The position is within the
     * node set covered by this iterator, not within the DOM.
     */
    public int getPosition() {
	return (_current);
    }

    /**
     * Returns the position of the last node in this iterator. The integer
     * returned is equivalent to the number of nodes in this iterator.
     */
    public int getLast() {
	return _last;
    }

    /**
     * Saves the position of this iterator - see gotoMark()
     */
    public void setMark() {
	_source.setMark();
	_markedNode = _current;
    }

    /**
     * Restores the position of this iterator - see setMark()
     */
    public void gotoMark() {
	_source.gotoMark();
	_current = _markedNode;
    }

}