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.Debug
34 {
35     using System.Collections.Generic;
36     using ParseTree = Antlr.Runtime.Tree.ParseTree;
37 
38     /** <summary>
39      *  This parser listener tracks rule entry/exit and token matches
40      *  to build a simple parse tree using ParseTree nodes.
41      *  </summary>
42      */
43     public class ParseTreeBuilder : BlankDebugEventListener
44     {
45         public const string EPSILON_PAYLOAD = "<epsilon>";
46 
47         Stack<ParseTree> callStack = new Stack<ParseTree>();
48         List<IToken> hiddenTokens = new List<IToken>();
49         int backtracking = 0;
50 
ParseTreeBuilder( string grammarName )51         public ParseTreeBuilder( string grammarName )
52         {
53             ParseTree root = Create( "<grammar " + grammarName + ">" );
54             callStack.Push( root );
55         }
56 
57         public virtual ParseTree Tree
58         {
59             get
60             {
61                 ParseTree[] stack = callStack.ToArray();
62                 return stack[stack.Length - 1];
63             }
64         }
65 
66         /** <summary>
67          *  What kind of node to create.  You might want to override
68          *  so I factored out creation here.
69          *  </summary>
70          */
Create( object payload )71         public virtual ParseTree Create( object payload )
72         {
73             return new ParseTree( payload );
74         }
75 
EpsilonNode()76         public virtual ParseTree EpsilonNode()
77         {
78             return Create( EPSILON_PAYLOAD );
79         }
80 
81         /** <summary>Backtracking or cyclic DFA, don't want to add nodes to tree</summary> */
EnterDecision( int d, bool couldBacktrack )82         public override void EnterDecision( int d, bool couldBacktrack )
83         {
84             backtracking++;
85         }
ExitDecision( int i )86         public override void ExitDecision( int i )
87         {
88             backtracking--;
89         }
90 
EnterRule( string filename, string ruleName )91         public override void EnterRule( string filename, string ruleName )
92         {
93             if ( backtracking > 0 )
94                 return;
95             ParseTree parentRuleNode = callStack.Peek();
96             ParseTree ruleNode = Create( ruleName );
97             parentRuleNode.AddChild( ruleNode );
98             callStack.Push( ruleNode );
99         }
100 
ExitRule( string filename, string ruleName )101         public override void ExitRule( string filename, string ruleName )
102         {
103             if ( backtracking > 0 )
104                 return;
105             ParseTree ruleNode = callStack.Peek();
106             if ( ruleNode.ChildCount == 0 )
107             {
108                 ruleNode.AddChild( EpsilonNode() );
109             }
110             callStack.Pop();
111         }
112 
ConsumeToken( IToken token )113         public override void ConsumeToken( IToken token )
114         {
115             if ( backtracking > 0 )
116                 return;
117             ParseTree ruleNode = callStack.Peek();
118             ParseTree elementNode = Create( token );
119             elementNode.hiddenTokens = this.hiddenTokens;
120             this.hiddenTokens = new List<IToken>();
121             ruleNode.AddChild( elementNode );
122         }
123 
ConsumeHiddenToken( IToken token )124         public override void ConsumeHiddenToken( IToken token )
125         {
126             if ( backtracking > 0 )
127                 return;
128             hiddenTokens.Add( token );
129         }
130 
RecognitionException( RecognitionException e )131         public override void RecognitionException( RecognitionException e )
132         {
133             if ( backtracking > 0 )
134                 return;
135             ParseTree ruleNode = callStack.Peek();
136             ParseTree errorNode = Create( e );
137             ruleNode.AddChild( errorNode );
138         }
139     }
140 }
141