antlr-3.4/runtime/CSharp2/Sources/Antlr3.Runtime/Antlr.Runtime.Tree/TreeRewriter.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.Tree {
    using Console = System.Console;

    public class TreeRewriter<TTree> : TreeParser {
        protected ITokenStream originalTokenStream;
        protected ITreeAdaptor originalAdaptor;

        System.Func<IAstRuleReturnScope<TTree>> topdown_func;
        System.Func<IAstRuleReturnScope<TTree>> bottomup_func;

        public TreeRewriter(ITreeNodeStream input)
            : this(input, new RecognizerSharedState()) {
        }
        public TreeRewriter(ITreeNodeStream input, RecognizerSharedState state)
            : base(input, state) {
            originalAdaptor = input.TreeAdaptor;
            originalTokenStream = input.TokenStream;
            topdown_func = () => Topdown();
            bottomup_func = () => Bottomup();
        }

        public virtual object ApplyOnce(object t, System.Func<IAstRuleReturnScope<TTree>> whichRule) {
            if (t == null)
                return null;

            try {
                // share TreeParser object but not parsing-related state
                state = new RecognizerSharedState();
                input = new CommonTreeNodeStream(originalAdaptor, t);
                ((CommonTreeNodeStream)input).TokenStream = originalTokenStream;
                BacktrackingLevel = 1;
                IAstRuleReturnScope<TTree> r = whichRule();
                BacktrackingLevel = 0;
                if (Failed)
                    return t;

                if (typeof(CommonTree).IsAssignableFrom(typeof(TTree))) {
                    if (r != null && !t.Equals(r.Tree) && r.Tree != null) {
                        // show any transformations
                        Console.Out.WriteLine(((CommonTree)t).ToStringTree() + " -> " +
                                           ((CommonTree)(object)r.Tree).ToStringTree());
                    }
                }

                if (r != null && r.Tree != null)
                    return r.Tree;
                else
                    return t;
            } catch (RecognitionException) {
            }
            return t;
        }

        public virtual object ApplyRepeatedly(object t, System.Func<IAstRuleReturnScope<TTree>> whichRule) {
            bool treeChanged = true;
            while (treeChanged) {
                object u = ApplyOnce(t, whichRule);
                treeChanged = !t.Equals(u);
                t = u;
            }
            return t;
        }

        public virtual object Downup(object t) {
            TreeVisitor v = new TreeVisitor(new CommonTreeAdaptor());
            t = v.Visit(t, (o) => ApplyOnce(o, topdown_func), (o) => ApplyRepeatedly(o, bottomup_func));
            return t;
        }

        // methods the downup strategy uses to do the up and down rules.
        // to override, just define tree grammar rule topdown and turn on
        // filter=true.
        public virtual IAstRuleReturnScope<TTree> Topdown() {
            return null;
        }

        public virtual IAstRuleReturnScope<TTree> Bottomup() {
            return null;
        }
    }
}