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      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     using Console = System.Console;
     35 
     36     public class TreeRewriter<TTree> : TreeParser {
     37         protected ITokenStream originalTokenStream;
     38         protected ITreeAdaptor originalAdaptor;
     39 
     40         System.Func<IAstRuleReturnScope<TTree>> topdown_func;
     41         System.Func<IAstRuleReturnScope<TTree>> bottomup_func;
     42 
     43         public TreeRewriter(ITreeNodeStream input)
     44             : this(input, new RecognizerSharedState()) {
     45         }
     46         public TreeRewriter(ITreeNodeStream input, RecognizerSharedState state)
     47             : base(input, state) {
     48             originalAdaptor = input.TreeAdaptor;
     49             originalTokenStream = input.TokenStream;
     50             topdown_func = () => Topdown();
     51             bottomup_func = () => Bottomup();
     52         }
     53 
     54         public virtual object ApplyOnce(object t, System.Func<IAstRuleReturnScope<TTree>> whichRule) {
     55             if (t == null)
     56                 return null;
     57 
     58             try {
     59                 // share TreeParser object but not parsing-related state
     60                 state = new RecognizerSharedState();
     61                 input = new CommonTreeNodeStream(originalAdaptor, t);
     62                 ((CommonTreeNodeStream)input).TokenStream = originalTokenStream;
     63                 BacktrackingLevel = 1;
     64                 IAstRuleReturnScope<TTree> r = whichRule();
     65                 BacktrackingLevel = 0;
     66                 if (Failed)
     67                     return t;
     68 
     69                 if (typeof(CommonTree).IsAssignableFrom(typeof(TTree))) {
     70                     if (r != null && !t.Equals(r.Tree) && r.Tree != null) {
     71                         // show any transformations
     72                         Console.Out.WriteLine(((CommonTree)t).ToStringTree() + " -> " +
     73                                            ((CommonTree)(object)r.Tree).ToStringTree());
     74                     }
     75                 }
     76 
     77                 if (r != null && r.Tree != null)
     78                     return r.Tree;
     79                 else
     80                     return t;
     81             } catch (RecognitionException) {
     82             }
     83             return t;
     84         }
     85 
     86         public virtual object ApplyRepeatedly(object t, System.Func<IAstRuleReturnScope<TTree>> whichRule) {
     87             bool treeChanged = true;
     88             while (treeChanged) {
     89                 object u = ApplyOnce(t, whichRule);
     90                 treeChanged = !t.Equals(u);
     91                 t = u;
     92             }
     93             return t;
     94         }
     95 
     96         public virtual object Downup(object t) {
     97             TreeVisitor v = new TreeVisitor(new CommonTreeAdaptor());
     98             t = v.Visit(t, (o) => ApplyOnce(o, topdown_func), (o) => ApplyRepeatedly(o, bottomup_func));
     99             return t;
    100         }
    101 
    102         // methods the downup strategy uses to do the up and down rules.
    103         // to override, just define tree grammar rule topdown and turn on
    104         // filter=true.
    105         public virtual IAstRuleReturnScope<TTree> Topdown() {
    106             return null;
    107         }
    108 
    109         public virtual IAstRuleReturnScope<TTree> Bottomup() {
    110             return null;
    111         }
    112     }
    113 }
    114