Source for javax.swing.text.ElementIterator

   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: }