TreeRewriter.cs revision 324c4644fee44b9898524c09511bd33c3f12e2df 
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
33namespace Antlr.Runtime.Tree
34{
35    using Antlr.Runtime.Misc;
36
37    using Console = System.Console;
38
39    public class TreeRewriter : TreeParser
40    {
41        protected bool showTransformations;
42
43        protected ITokenStream originalTokenStream;
44        protected ITreeAdaptor originalAdaptor;
45
46        Func<IAstRuleReturnScope> topdown_func;
47        Func<IAstRuleReturnScope> bottomup_func;
48
49        public TreeRewriter( ITreeNodeStream input )
50            : this( input, new RecognizerSharedState() )
51        {
52        }
53        public TreeRewriter( ITreeNodeStream input, RecognizerSharedState state )
54            : base( input, state )
55        {
56            originalAdaptor = input.TreeAdaptor;
57            originalTokenStream = input.TokenStream;
58            topdown_func = () => Topdown();
59            bottomup_func = () => Bottomup();
60        }
61
62        public virtual object ApplyOnce( object t, Func<IAstRuleReturnScope> whichRule )
63        {
64            if ( t == null )
65                return null;
66
67            try
68            {
69                // share TreeParser object but not parsing-related state
70                state = new RecognizerSharedState();
71                input = new CommonTreeNodeStream( originalAdaptor, t );
72                ( (CommonTreeNodeStream)input ).TokenStream = originalTokenStream;
73                BacktrackingLevel = 1;
74                IAstRuleReturnScope r = whichRule();
75                BacktrackingLevel = 0;
76                if ( Failed )
77                    return t;
78
79                if (showTransformations && r != null && !t.Equals(r.Tree) && r.Tree != null)
80                    ReportTransformation(t, r.Tree);
81
82                if ( r != null && r.Tree != null )
83                    return r.Tree;
84                else
85                    return t;
86            }
87            catch ( RecognitionException )
88            {
89            }
90
91            return t;
92        }
93
94        public virtual object ApplyRepeatedly( object t, Func<IAstRuleReturnScope> whichRule )
95        {
96            bool treeChanged = true;
97            while ( treeChanged )
98            {
99                object u = ApplyOnce( t, whichRule );
100                treeChanged = !t.Equals( u );
101                t = u;
102            }
103            return t;
104        }
105
106        public virtual object Downup( object t )
107        {
108            return Downup( t, false );
109        }
110
111        public virtual object Downup( object t, bool showTransformations )
112        {
113            this.showTransformations = showTransformations;
114            TreeVisitor v = new TreeVisitor( new CommonTreeAdaptor() );
115            t = v.Visit( t, ( o ) => ApplyOnce( o, topdown_func ), ( o ) => ApplyRepeatedly( o, bottomup_func ) );
116            return t;
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.
122        public virtual IAstRuleReturnScope Topdown()
123        {
124            return null;
125        }
126
127        public virtual IAstRuleReturnScope Bottomup()
128        {
129            return null;
130        }
131
132        /** Override this if you need transformation tracing to go somewhere
133         *  other than stdout or if you're not using ITree-derived trees.
134         */
135        protected virtual void ReportTransformation(object oldTree, object newTree)
136        {
137            ITree old = oldTree as ITree;
138            ITree @new = newTree as ITree;
139            string oldMessage = old != null ? old.ToStringTree() : "??";
140            string newMessage = @new != null ? @new.ToStringTree() : "??";
141            Console.WriteLine("{0} -> {1}", oldMessage, newMessage);
142        }
143    }
144}
145