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

/*
 * @(#)$Id$
 *
 * The Apache Software License, Version 1.1
 *
 *
 * Copyright (c) 2001-2003 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.
 *
 * 4. The names "Xalan" and "Apache Software Foundation" must
 *    not be used to endorse or promote products derived from this
 *    software without prior written permission. For written
 *    permission, please contact apache@apache.org.
 *
 * 5. Products derived from this software may not be called "Apache",
 *    nor may "Apache" appear in their name, without prior written
 *    permission of the Apache Software Foundation.
 *
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
 * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * 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 Santiago Pericas-Geertsen
 *
 */

package org.apache.xalan.xsltc.dom;

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

/**
 * This iterator is a wrapper that always returns the position of
 * a node in document order. It is needed for the case where 
 * a call to position() occurs in the context of an XSLT element
 * such as xsl:for-each, xsl:apply-templates, etc. 
 *
 * The getPosition() methods in DTMAxisIterators defined
 * in DTMDefaultBaseIterators always return the position
 * in document order, which is backwards for XPath in the
 * case of the ancestor, ancestor-or-self, previous and
 * previous-sibling.
 *
 * XSLTC implements position() with the
 * BasisLibrary.positionF() method, and uses the
 * DTMAxisIterator.isReverse() method to determine
 * whether the result of getPosition() should be
 * interpreted as being equal to position().
 * But when the expression appears in apply-templates of
 * for-each, the position() function operates in document
 * order.
 *
 * The only effect of the ForwardPositionIterator is to force
 * the result of isReverse() to false, so that
 * BasisLibrary.positionF() calculates position() in a way
 * that's consistent with the context in which the
 * iterator is being used."
 *
 * (Apparently the correction of isReverse() occurs
 * implicitly, by inheritance. This class also appears
 * to maintain its own position counter, which seems
 * redundant.)
 */
public final class ForwardPositionIterator extends DTMAxisIteratorBase {

    private DTMAxisIterator _source;

    public ForwardPositionIterator(DTMAxisIterator source) {
	_source = source;
    }

    public DTMAxisIterator cloneIterator() {
	try {
	    final ForwardPositionIterator clone = 
		(ForwardPositionIterator) 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 int next() {
	return returnNode(_source.next());
    }
	
    public DTMAxisIterator setStartNode(int node) {
	_source.setStartNode(node);
	return this;
    }

    public DTMAxisIterator reset() {
	_source.reset();
	return resetPosition();
    }

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

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