/*
* [The "BSD license"]
* Copyright (c) 2012 Terence Parr
* Copyright (c) 2012 Sam Harwell
* 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.v4.runtime.tree;
import org.antlr.v4.runtime.ParserRuleContext;
import org.antlr.v4.runtime.RuleContext;
public class ParseTreeWalker {
public static final ParseTreeWalker DEFAULT = new ParseTreeWalker();
public void walk(ParseTreeListener listener, ParseTree t) {
if ( t instanceof ErrorNode) {
listener.visitErrorNode((ErrorNode)t);
return;
}
else if ( t instanceof TerminalNode) {
listener.visitTerminal((TerminalNode)t);
return;
}
RuleNode r = (RuleNode)t;
enterRule(listener, r);
int n = r.getChildCount();
for (int i = 0; i<n; i++) {
walk(listener, r.getChild(i));
}
exitRule(listener, r);
}
/**
* The discovery of a rule node, involves sending two events: the generic
* {@link ParseTreeListener#enterEveryRule} and a
* {@link RuleContext}-specific event. First we trigger the generic and then
* the rule specific. We to them in reverse order upon finishing the node.
*/
protected void enterRule(ParseTreeListener listener, RuleNode r) {
ParserRuleContext ctx = (ParserRuleContext)r.getRuleContext();
listener.enterEveryRule(ctx);
ctx.enterRule(listener);
}
protected void exitRule(ParseTreeListener listener, RuleNode r) {
ParserRuleContext ctx = (ParserRuleContext)r.getRuleContext();
ctx.exitRule(listener);
listener.exitEveryRule(ctx);
}
}