antlr-3.4/runtime/CSharp2/Sources/Antlr3.Runtime/Antlr.Runtime.Debug/ParseTreeBuilder.cs

/*
 * [The "BSD licence"]
 * Copyright (c) 2005-2008 Terence Parr
 * All rights reserved.
 *
 * Conversion to C#:
 * Copyright (c) 2008-2009 Sam Harwell, Pixel Mine, Inc.
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

namespace Antlr.Runtime.Debug {
    using System.Collections.Generic;
    using ParseTree = Antlr.Runtime.Tree.ParseTree;

    /** <summary>
     *  This parser listener tracks rule entry/exit and token matches
     *  to build a simple parse tree using ParseTree nodes.
     *  </summary>
     */
    public class ParseTreeBuilder : BlankDebugEventListener {
        public const string EPSILON_PAYLOAD = "<epsilon>";

        Stack<ParseTree> callStack = new Stack<ParseTree>();
        List<IToken> hiddenTokens = new List<IToken>();
        int backtracking = 0;

        public ParseTreeBuilder(string grammarName) {
            ParseTree root = Create("<grammar " + grammarName + ">");
            callStack.Push(root);
        }

        public virtual ParseTree GetTree() {
            var enumerator = callStack.GetEnumerator();
            enumerator.MoveNext();
            return enumerator.Current;
        }

        /** <summary>
         *  What kind of node to create.  You might want to override
         *  so I factored out creation here.
         *  </summary>
         */
        public virtual ParseTree Create(object payload) {
            return new ParseTree(payload);
        }

        public virtual ParseTree EpsilonNode() {
            return Create(EPSILON_PAYLOAD);
        }

        /** <summary>Backtracking or cyclic DFA, don't want to add nodes to tree</summary> */
        public override void EnterDecision(int d, bool couldBacktrack) {
            backtracking++;
        }
        public override void ExitDecision(int i) {
            backtracking--;
        }

        public override void EnterRule(string filename, string ruleName) {
            if (backtracking > 0)
                return;
            ParseTree parentRuleNode = callStack.Peek();
            ParseTree ruleNode = Create(ruleName);
            parentRuleNode.AddChild(ruleNode);
            callStack.Push(ruleNode);
        }

        public override void ExitRule(string filename, string ruleName) {
            if (backtracking > 0)
                return;
            ParseTree ruleNode = callStack.Peek();
            if (ruleNode.ChildCount == 0) {
                ruleNode.AddChild(EpsilonNode());
            }
            callStack.Pop();
        }

        public override void ConsumeToken(IToken token) {
            if (backtracking > 0)
                return;
            ParseTree ruleNode = callStack.Peek();
            ParseTree elementNode = Create(token);
            elementNode.hiddenTokens = this.hiddenTokens;
            this.hiddenTokens = new List<IToken>();
            ruleNode.AddChild(elementNode);
        }

        public override void ConsumeHiddenToken(IToken token) {
            if (backtracking > 0)
                return;
            hiddenTokens.Add(token);
        }

        public override void RecognitionException(RecognitionException e) {
            if (backtracking > 0)
                return;
            ParseTree ruleNode = callStack.Peek();
            ParseTree errorNode = Create(e);
            ruleNode.AddChild(errorNode);
        }
    }
}