001/*
002 * Copyright (C) 2009-2011 Mathias Doenitz
003 *
004 * Licensed under the Apache License, Version 2.0 (the "License");
005 * you may not use this file except in compliance with the License.
006 * You may obtain a copy of the License at
007 *
008 * http://www.apache.org/licenses/LICENSE-2.0
009 *
010 * Unless required by applicable law or agreed to in writing, software
011 * distributed under the License is distributed on an "AS IS" BASIS,
012 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
013 * See the License for the specific language governing permissions and
014 * limitations under the License.
015 */
016
017package org.parboiled.matchers;
018
019import org.parboiled.MatcherContext;
020import org.parboiled.Rule;
021import org.parboiled.matchervisitors.MatcherVisitor;
022
023import static org.parboiled.common.Preconditions.checkArgNotNull;
024
025/**
026 * A special {@link Matcher} not actually matching any input but rather trying its submatcher against the current input
027 * position. Succeeds if the submatcher would fail.
028 */
029public class TestNotMatcher extends CustomDefaultLabelMatcher<TestNotMatcher> {
030    public final Matcher subMatcher;
031
032    public TestNotMatcher(Rule subRule) {
033        super(checkArgNotNull(subRule, "subRule"), "TestNot");
034        this.subMatcher = getChildren().get(0);
035    }
036
037    public boolean match(MatcherContext context) {
038        int lastIndex = context.getCurrentIndex();
039        Object valueStackSnapshot = context.getValueStack().takeSnapshot();
040
041        if (subMatcher.getSubContext(context).runMatcher()) return false;
042
043        // reset location, Test matchers never advance
044        context.setCurrentIndex(lastIndex);
045
046        // erase all value stack changes the the submatcher could have made
047        context.getValueStack().restoreSnapshot(valueStackSnapshot);
048        return true;
049    }
050
051    public <R> R accept(MatcherVisitor<R> visitor) {
052        checkArgNotNull(visitor, "visitor");
053        return visitor.visit(this);
054    }
055
056}