gomp-20050608-branch/libjava/classpath/javax/swing/text/ElementIterator.java

   1 /* ElementIterator.java --
   2    Copyright (C) 2005 Free Software Foundation, Inc.
   3
   4 This file is part of GNU Classpath.
   5
   6 GNU Classpath is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 2, or (at your option)
   9 any later version.
  10
  11 GNU Classpath is distributed in the hope that it will be useful, but
  12 WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14 General Public License for more details.
  15
  16 You should have received a copy of the GNU General Public License
  17 along with GNU Classpath; see the file COPYING.  If not, write to the
  18 Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  19 02110-1301 USA.
  20
  21 Linking this library statically or dynamically with other modules is
  22 making a combined work based on this library.  Thus, the terms and
  23 conditions of the GNU General Public License cover the whole
  24 combination.
  25
  26 As a special exception, the copyright holders of this library give you
  27 permission to link this library with independent modules to produce an
  28 executable, regardless of the license terms of these independent
  29 modules, and to copy and distribute the resulting executable under
  30 terms of your choice, provided that you also meet, for each linked
  31 independent module, the terms and conditions of the license of that
  32 module.  An independent module is a module which is not derived from
  33 or based on this library.  If you modify this library, you may extend
  34 this exception to your version of the library, but you are not
  35 obligated to do so.  If you do not wish to do so, delete this
  36 exception statement from your version. */
  37
  38 package javax.swing.text;
  39
  40 /**
  41  * This class can be used to iterate over the {@link Element} tree of
  42  * a {@link Document} or an {@link Element}.  This iterator performs
  43  * an "in-order" traversal -- first it visits a node, then each of the
  44  * node's children in order.  No locking is performed during the
  45  * iteration; that is up to the caller.
  46  */
  47 public class ElementIterator implements Cloneable
  48 {
  49   // The root element.
  50   private Element root;
  51   // The current element.
  52   private Element currentElement;
  53   // The depth to which we have descended in the tree.
  54   private int currentDepth;
  55
  56   // This is at least as big as the current depth, and at index N
  57   // contains the index of the child element we're currently
  58   // examining.
  59   private int[] state;
  60
  61   // The previous item.
  62   private Element previousItem;
  63
  64   /**
  65    * Create a new ElementIterator to iterate over the given document.
  66    * @param document the Document over which we iterate
  67    */
  68   public ElementIterator(Document document)
  69   {
  70     this.root = document.getDefaultRootElement();
  71     this.currentElement = root;
  72     this.state = new int[5];
  73   }
  74
  75   /**
  76    * Create a new ElementIterator to iterate over the given document.
  77    * @param root the Document over which we iterate
  78    */
  79   public ElementIterator(Element root)
  80   {
  81     this.root = root;
  82     this.currentElement = root;
  83     this.state = new int[5];
  84   }
  85
  86   /**
  87    * Returns a new ElementIterator which is a clone of this
  88    * ElementIterator.
  89    */
  90   public Object clone()
  91   {
  92     try
  93       {
  94         return super.clone();
  95       }
  96     catch (CloneNotSupportedException _)
  97       {
  98         // Can't happen.
  99         return null;
 100       }
 101   }
 102
 103   /**
 104    * Returns the current element.
 105    */
 106   public Element current()
 107   {
 108     return currentElement;
 109   }
 110
 111   /**
 112    * Returns the depth to which we have descended in the tree.
 113    */
 114   public int depth()
 115   {
 116     return currentDepth;
 117   }
 118
 119   /**
 120    * Returns the first element in the tree.
 121    */
 122   public Element first()
 123   {
 124     // Reset the iterator.
 125     currentElement = root;
 126     currentDepth = 0;
 127     previousItem = null;
 128     return root;
 129   }
 130
 131   /**
 132    * Advance the iterator and return the next element of the tree,
 133    * performing an "in-order" traversal.
 134    */
 135   public Element next()
 136   {
 137     previousItem = currentElement;
 138     if (currentElement == null)
 139       return null;
 140     if (! currentElement.isLeaf())
 141       {
 142         ++currentDepth;
 143         if (currentDepth > state.length)
 144           {
 145             int[] newState = new int[state.length * 2];
 146             System.arraycopy(state, 0, newState, 0, state.length);
 147             state = newState;
 148           }
 149         state[currentDepth] = 0;
 150         currentElement = currentElement.getElement(0);
 151         return currentElement;
 152       }
 153
 154     while (currentDepth > 0)
 155       {
 156         // At a leaf, or done with a non-leaf's children, so go up a
 157         // level.
 158         --currentDepth;
 159         currentElement = currentElement.getParentElement();
 160         ++state[currentDepth];
 161         if (state[currentDepth] < currentElement.getElementCount())
 162           {
 163             currentElement = currentElement.getElement(state[currentDepth]);
 164             return currentElement;
 165           }
 166       }
 167
 168     currentElement = null;
 169     return currentElement;
 170   }
 171
 172   /**
 173    * Returns the previous item.  Does not modify the iterator state.
 174    */
 175   public Element previous()
 176   {
 177     if (currentElement == null || currentElement == root)
 178       return null;
 179     return previousItem;
 180   }
 181 }