org.antlr.v4.runtime.tree.ParseTreeWalker.java Source code

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Here is the source code for org.antlr.v4.runtime.tree.ParseTreeWalker.java

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/*
 * Copyright (c) 2012-2017 The ANTLR Project. All rights reserved.
 * Use of this file is governed by the BSD 3-clause license that
 * can be found in the LICENSE.txt file in the project root.
 */

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);
    }
}