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      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 {
     36         public Object rule() throws RecognitionException;
     37     }
     38 
     39     protected boolean showTransformations = false;
     40 
     41     protected TokenStream originalTokenStream;
     42     protected TreeAdaptor originalAdaptor;
     43 
     44     public TreeRewriter(TreeNodeStream input) {
     45         this(input, new RecognizerSharedState());
     46     }
     47     public TreeRewriter(TreeNodeStream input, RecognizerSharedState state) {
     48         super(input, state);
     49         originalAdaptor = input.getTreeAdaptor();
     50         originalTokenStream = input.getTokenStream();
     51     }
     52 
     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 
     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 
     86     public Object downup(Object t) { return downup(t, false); }
     87 
     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             public Object pre(Object t)  { return applyOnce(t, topdown_fptr); }
     93             public Object post(Object t) { return applyRepeatedly(t, bottomup_ftpr); }
     94         };
     95         t = v.visit(t, actions);
     96         return t;
     97     }
     98 
     99     /** Override this if you need transformation tracing to go somewhere
    100      *  other than stdout or if you're not using Tree-derived trees.
    101      */
    102     public void reportTransformation(Object oldTree, Object newTree) {
    103         System.out.println(((Tree)oldTree).toStringTree()+" -> "+
    104                            ((Tree)newTree).toStringTree());
    105     }
    106 
    107     fptr topdown_fptr = new fptr() {
    108         public Object rule() throws RecognitionException { return topdown(); }
    109     };
    110 
    111     fptr bottomup_ftpr = new fptr() {
    112         public Object rule() throws RecognitionException { return bottomup(); }
    113     };
    114 
    115     // methods the downup strategy uses to do the up and down rules.
    116     // to override, just define tree grammar rule topdown and turn on
    117     // filter=true.
    118     public Object topdown() throws RecognitionException { return null; }
    119     public Object bottomup() throws RecognitionException { return null; }
    120 }
    121