1 /*
2  [The "BSD license"]
3  Copyright (c) 2005-2009 Terence Parr
4  All rights reserved.
5 
6  Redistribution and use in source and binary forms, with or without
7  modification, are permitted provided that the following conditions
8  are met:
9  1. Redistributions of source code must retain the above copyright
10      notice, this list of conditions and the following disclaimer.
11  2. Redistributions in binary form must reproduce the above copyright
12      notice, this list of conditions and the following disclaimer in the
13      documentation and/or other materials provided with the distribution.
14  3. The name of the author may not be used to endorse or promote products
15      derived from this software without specific prior written permission.
16 
17  THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
18  IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
19  OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
20  IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
21  INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
22  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23  DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24  THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25  (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
26  THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
27  */
28 package org.antlr.runtime.tree;
29 
30 import org.antlr.runtime.RecognizerSharedState;
31 import org.antlr.runtime.RecognitionException;
32 import org.antlr.runtime.TokenStream;
33 
34 public class TreeRewriter extends TreeParser {
35     public interface fptr {
rule()36         public Object rule() throws RecognitionException;
37     }
38 
39     protected boolean showTransformations = false;
40 
41     protected TokenStream originalTokenStream;
42     protected TreeAdaptor originalAdaptor;
43 
TreeRewriter(TreeNodeStream input)44     public TreeRewriter(TreeNodeStream input) {
45         this(input, new RecognizerSharedState());
46     }
TreeRewriter(TreeNodeStream input, RecognizerSharedState state)47     public TreeRewriter(TreeNodeStream input, RecognizerSharedState state) {
48         super(input, state);
49         originalAdaptor = input.getTreeAdaptor();
50         originalTokenStream = input.getTokenStream();
51     }
52 
applyOnce(Object t, fptr whichRule)53     public Object applyOnce(Object t, fptr whichRule) {
54         if ( t==null ) return null;
55         try {
56             // share TreeParser object but not parsing-related state
57             state = new RecognizerSharedState();
58             input = new CommonTreeNodeStream(originalAdaptor, t);
59             ((CommonTreeNodeStream)input).setTokenStream(originalTokenStream);
60             setBacktrackingLevel(1);
61             TreeRuleReturnScope r = (TreeRuleReturnScope)whichRule.rule();
62             setBacktrackingLevel(0);
63             if ( failed() ) return t;
64             if ( showTransformations &&
65                  r!=null && !t.equals(r.getTree()) && r.getTree()!=null )
66             {
67                 reportTransformation(t, r.getTree());
68             }
69             if ( r!=null && r.getTree()!=null ) return r.getTree();
70             else return t;
71         }
72         catch (RecognitionException e) { ; }
73         return t;
74     }
75 
applyRepeatedly(Object t, fptr whichRule)76     public Object applyRepeatedly(Object t, fptr whichRule) {
77         boolean treeChanged = true;
78         while ( treeChanged ) {
79             Object u = applyOnce(t, whichRule);
80             treeChanged = !t.equals(u);
81             t = u;
82         }
83         return t;
84     }
85 
downup(Object t)86     public Object downup(Object t) { return downup(t, false); }
87 
downup(Object t, boolean showTransformations)88     public Object downup(Object t, boolean showTransformations) {
89         this.showTransformations = showTransformations;
90         TreeVisitor v = new TreeVisitor(new CommonTreeAdaptor());
91         TreeVisitorAction actions = new TreeVisitorAction() {
92 			@Override
93             public Object pre(Object t)  { return applyOnce(t, topdown_fptr); }
94 			@Override
95             public Object post(Object t) { return applyRepeatedly(t, bottomup_ftpr); }
96         };
97         t = v.visit(t, actions);
98         return t;
99     }
100 
101     /** Override this if you need transformation tracing to go somewhere
102      *  other than stdout or if you're not using Tree-derived trees.
103      */
reportTransformation(Object oldTree, Object newTree)104     public void reportTransformation(Object oldTree, Object newTree) {
105         System.out.println(((Tree)oldTree).toStringTree()+" -> "+
106                            ((Tree)newTree).toStringTree());
107     }
108 
109     fptr topdown_fptr = new fptr() {
110 		@Override
111         public Object rule() throws RecognitionException { return topdown(); }
112     };
113 
114     fptr bottomup_ftpr = new fptr() {
115 		@Override
116         public Object rule() throws RecognitionException { return bottomup(); }
117     };
118 
119     // methods the downup strategy uses to do the up and down rules.
120     // to override, just define tree grammar rule topdown and turn on
121     // filter=true.
topdown()122     public Object topdown() throws RecognitionException { return null; }
bottomup()123     public Object bottomup() throws RecognitionException { return null; }
124 }
125