| /* |
| [The "BSD license"] |
| Copyright (c) 2005-2009 Terence Parr |
| 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. |
| */ |
| |
| package org.antlr.runtime.tree; |
| |
| /** Do a depth first walk of a tree, applying pre() and post() actions |
| * as we discover and finish nodes. |
| */ |
| public class TreeVisitor { |
| protected TreeAdaptor adaptor; |
| |
| public TreeVisitor(TreeAdaptor adaptor) { |
| this.adaptor = adaptor; |
| } |
| public TreeVisitor() { this(new CommonTreeAdaptor()); } |
| |
| /** Visit every node in tree t and trigger an action for each node |
| * before/after having visited all of its children. |
| * Execute both actions even if t has no children. |
| * If a child visit yields a new child, it can update its |
| * parent's child list or just return the new child. The |
| * child update code works even if the child visit alters its parent |
| * and returns the new tree. |
| * |
| * Return result of applying post action to this node. |
| */ |
| public Object visit(Object t, TreeVisitorAction action) { |
| // System.out.println("visit "+((Tree)t).toStringTree()); |
| boolean isNil = adaptor.isNil(t); |
| if ( action!=null && !isNil ) { |
| t = action.pre(t); // if rewritten, walk children of new t |
| } |
| for (int i=0; i<adaptor.getChildCount(t); i++) { |
| Object child = adaptor.getChild(t, i); |
| Object visitResult = visit(child, action); |
| Object childAfterVisit = adaptor.getChild(t, i); |
| if ( visitResult != childAfterVisit ) { // result & child differ? |
| adaptor.setChild(t, i, visitResult); |
| } |
| } |
| if ( action!=null && !isNil ) t = action.post(t); |
| return t; |
| } |
| } |