ASTIterator


1   // $Id: ASTIterator.java,v 1.1 2005/07/12 20:27:17 steveebersole Exp $
2   package org.hibernate.hql.ast.util;
3   
4   import java.util.Iterator  ;
5   import java.util.LinkedList  ;
6   
7   import antlr.collections.AST;
8   
9   /**
10   * Depth first iteration of an ANTLR AST.
11   *
12   * @author josh Sep 25, 2004 7:44:39 AM
13   */
14  public class ASTIterator implements Iterator   {
15      private AST next, current;
16      private LinkedList   parents = new LinkedList  ();
17  
18      public void remove() {
19          throw new UnsupportedOperationException  ( "remove() is not supported" );
20      }
21  
22      public boolean hasNext() {
23          return next != null;
24      }
25  
26      public Object   next() {
27          return nextNode();
28      }
29  
30      public ASTIterator(AST tree) {
31          next = tree;
32          down();
33      }
34  
35      public AST nextNode() {
36          current = next;
37          if ( next != null ) {
38              AST nextSibling = next.getNextSibling();
39              if ( nextSibling == null ) {
40                  next = pop();
41              }
42              else {
43                  next = nextSibling;
44                  down();
45              }
46          }
47          return current;
48      }
49  
50      private void down() {
51          while ( next != null && next.getFirstChild() != null ) {
52              push( next );
53              next = next.getFirstChild();
54          }
55      }
56  
57      private void push(AST parent) {
58          parents.addFirst( parent );
59      }
60  
61      private AST pop() {
62          if ( parents.size() == 0 ) {
63              return null;
64          }
65          else {
66              return ( AST ) parents.removeFirst();
67          }
68      }
69  
70  }
71
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