1. /*

  2.  * The Apache Software License, Version 1.1

  3.  *

  4.  *

  5.  * Copyright (c) 1999 The Apache Software Foundation.  All rights 

  6.  * reserved.

  7.  *

  8.  * Redistribution and use in source and binary forms, with or without

  9.  * modification, are permitted provided that the following conditions

  10.  * are met:

  11.  *

  12.  * 1. Redistributions of source code must retain the above copyright

  13.  *    notice, this list of conditions and the following disclaimer. 

  14.  *

  15.  * 2. Redistributions in binary form must reproduce the above copyright

  16.  *    notice, this list of conditions and the following disclaimer in

  17.  *    the documentation and/or other materials provided with the

  18.  *    distribution.

  19.  *

  20.  * 3. The end-user documentation included with the redistribution,

  21.  *    if any, must include the following acknowledgment:  

  22.  *       "This product includes software developed by the

  23.  *        Apache Software Foundation (http://www.apache.org/)."

  24.  *    Alternately, this acknowledgment may appear in the software itself,

  25.  *    if and wherever such third-party acknowledgments normally appear.

  26.  *

  27.  * 4. The names "Xalan" and "Apache Software Foundation" must

  28.  *    not be used to endorse or promote products derived from this

  29.  *    software without prior written permission. For written 

  30.  *    permission, please contact apache@apache.org.

  31.  *

  32.  * 5. Products derived from this software may not be called "Apache",

  33.  *    nor may "Apache" appear in their name, without prior written

  34.  *    permission of the Apache Software Foundation.

  35.  *

  36.  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED

  37.  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES

  38.  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE

  39.  * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR

  40.  * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,

  41.  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT

  42.  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF

  43.  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND

  44.  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,

  45.  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT

  46.  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF

  47.  * SUCH DAMAGE.

  48.  * ====================================================================

  49.  *

  50.  * This software consists of voluntary contributions made by many

  51.  * individuals on behalf of the Apache Software Foundation and was

  52.  * originally based on software copyright (c) 1999, Lotus

  53.  * Development Corporation., http://www.lotus.com.  For more

  54.  * information on the Apache Software Foundation, please see

  55.  * <http://www.apache.org/>.

  56.  */

  57. package org.apache.xml.dtm;

  58. 

  59. /**

  60.  * A class that implements traverses DTMAxisTraverser interface can traverse

  61.  * a set of nodes, usually as defined by an XPath axis.  It is different from

  62.  * an iterator, because it does not need to hold state, and, in fact, must not

  63.  * hold any iteration-based state.  It is meant to be implemented as an inner

  64.  * class of a DTM, and returned by the getAxisTraverser(final int axis)

  65.  * function.

  66.  *

  67.  * <p>A DTMAxisTraverser can probably not traverse a reverse axis in

  68.  * document order.</p>

  69.  *

  70.  * <p>Typical usage:</p>

  71.  * <pre><code>

  72.  * for(int nodeHandle=myTraverser.first(myContext);

  73.  *     nodeHandle!=DTM.NULL;

  74.  *     nodeHandle=myTraverser.next(myContext,nodeHandle))

  75.  * { ... processing for node indicated by nodeHandle goes here ... }

  76.  * </code></pre>

  77.  *

  78.  * @author Scott Boag

  79.  */

  80. public abstract class DTMAxisTraverser

  81. {

  82. 

  83.   /**

  84.    * By the nature of the stateless traversal, the context node can not be

  85.    * returned or the iteration will go into an infinate loop.  So to traverse 

  86.    * an axis, the first function must be used to get the first node.

  87.    *

  88.    * <p>This method needs to be overloaded only by those axis that process

  89.    * the self node. <\p>

  90.    *

  91.    * @param context The context node of this traversal. This is the point

  92.    * that the traversal starts from.

  93.    * @return the first node in the traversal.

  94.    */

  95.   public int first(int context)

  96.   {

  97.     return next(context, context);

  98.   }

  99. 

  100.   /**

  101.    * By the nature of the stateless traversal, the context node can not be

  102.    * returned or the iteration will go into an infinate loop.  So to traverse 

  103.    * an axis, the first function must be used to get the first node.

  104.    *

  105.    * <p>This method needs to be overloaded only by those axis that process

  106.    * the self node. <\p>

  107.    *

  108.    * @param context The context node of this traversal. This is the point

  109.    * of origin for the traversal -- its "root node" or starting point.

  110.    * @param extendedTypeID The extended type ID that must match.

  111.    *

  112.    * @return the first node in the traversal.

  113.    */

  114.   public int first(int context, int extendedTypeID)

  115.   {

  116.     return next(context, context, extendedTypeID);

  117.   }

  118. 

  119.   /**

  120.    * Traverse to the next node after the current node.

  121.    *

  122.    * @param context The context node of this traversal. This is the point

  123.    * of origin for the traversal -- its "root node" or starting point.

  124.    * @param current The current node of the traversal. This is the last known

  125.    * location in the traversal, typically the node-handle returned by the

  126.    * previous traversal step. For the first traversal step, context

  127.    * should be set equal to current. Note that in order to test whether

  128.    * context is in the set, you must use the first() method instead.

  129.    *

  130.    * @return the next node in the iteration, or DTM.NULL.

  131.    * @see first(int)

  132.    */

  133.   public abstract int next(int context, int current);

  134. 

  135.   /**

  136.    * Traverse to the next node after the current node that is matched

  137.    * by the extended type ID.

  138.    *

  139.    * @param context The context node of this traversal. This is the point

  140.    * of origin for the traversal -- its "root node" or starting point.

  141.    * @param current The current node of the traversal. This is the last known

  142.    * location in the traversal, typically the node-handle returned by the

  143.    * previous traversal step. For the first traversal step, context

  144.    * should be set equal to current. Note that in order to test whether

  145.    * context is in the set, you must use the first() method instead.

  146.    * @param extendedTypeID The extended type ID that must match.

  147.    *

  148.    * @return the next node in the iteration, or DTM.NULL.

  149.    * @see first(int,int)

  150.    */

  151.   public abstract int next(int context, int current, int extendedTypeID);

  152. }