1 /*
2  * [The "BSD licence"]
3  * Copyright (c) 2005-2008 Terence Parr
4  * All rights reserved.
5  *
6  * Conversion to C#:
7  * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
8  * All rights reserved.
9  *
10  * Redistribution and use in source and binary forms, with or without
11  * modification, are permitted provided that the following conditions
12  * are met:
13  * 1. Redistributions of source code must retain the above copyright
14  *    notice, this list of conditions and the following disclaimer.
15  * 2. Redistributions in binary form must reproduce the above copyright
16  *    notice, this list of conditions and the following disclaimer in the
17  *    documentation and/or other materials provided with the distribution.
18  * 3. The name of the author may not be used to endorse or promote products
19  *    derived from this software without specific prior written permission.
20  *
21  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
22  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
23  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
24  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
25  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
26  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
27  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
28  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
29  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
30  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
31  */
32 
33 namespace Antlr.Runtime.Tree
34 {
35     using Antlr.Runtime.Misc;
36 
37     /** <summary>Do a depth first walk of a tree, applying pre() and post() actions as we go.</summary> */
38     public class TreeVisitor
39     {
40         protected ITreeAdaptor adaptor;
41 
TreeVisitor( ITreeAdaptor adaptor )42         public TreeVisitor( ITreeAdaptor adaptor )
43         {
44             this.adaptor = adaptor;
45         }
TreeVisitor()46         public TreeVisitor()
47             : this( new CommonTreeAdaptor() )
48         {
49         }
50 
51         /** <summary>
52          *  Visit every node in tree t and trigger an action for each node
53          *  before/after having visited all of its children.  Bottom up walk.
54          *  Execute both actions even if t has no children.  Ignore return
55          *  results from transforming children since they will have altered
56          *  the child list of this node (their parent).  Return result of
57          *  applying post action to this node.
58          *  </summary>
59          */
Visit( object t, ITreeVisitorAction action )60         public object Visit( object t, ITreeVisitorAction action )
61         {
62             // System.out.println("visit "+((Tree)t).toStringTree());
63             bool isNil = adaptor.IsNil( t );
64             if ( action != null && !isNil )
65             {
66                 t = action.Pre( t ); // if rewritten, walk children of new t
67             }
68             for ( int i = 0; i < adaptor.GetChildCount(t); i++ )
69             {
70                 object child = adaptor.GetChild( t, i );
71                 Visit( child, action );
72             }
73             if ( action != null && !isNil )
74                 t = action.Post( t );
75             return t;
76         }
77 
Visit( object t, Func<object, object> preAction, Func<object, object> postAction )78         public object Visit( object t, Func<object, object> preAction, Func<object, object> postAction )
79         {
80             return Visit( t, new TreeVisitorAction( preAction, postAction ) );
81         }
82     }
83 }
84