001/*-------------------------------------------------------------------------+
002|                                                                          |
003| Copyright 2005-2011 the ConQAT Project                                   |
004|                                                                          |
005| Licensed under the Apache License, Version 2.0 (the "License");          |
006| you may not use this file except in compliance with the License.         |
007| You may obtain a copy of the License at                                  |
008|                                                                          |
009|    http://www.apache.org/licenses/LICENSE-2.0                            |
010|                                                                          |
011| Unless required by applicable law or agreed to in writing, software      |
012| distributed under the License is distributed on an "AS IS" BASIS,        |
013| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
014| See the License for the specific language governing permissions and      |
015| limitations under the License.                                           |
016+-------------------------------------------------------------------------*/
017package eu.cqse.check.framework.util.tokens;
018
019/**
020 * Base class for patterns that check a condition but do not advance the token
021 * stream.
022 */
023public abstract class ZeroLengthTokenPatternBase extends TokenPatternBase {
024
025        /** {@inheritDoc} */
026        @Override
027        protected TokenPatternMatch matchesLocally(TokenStream stream) {
028                int beforePosition = stream.getPosition();
029                boolean success = conditionApplies(stream);
030                stream.setPosition(beforePosition);
031                if (success) {
032                        return createMatch(stream);
033                }
034                return null;
035        }
036
037        /**
038         * Returns <code>true</code> if this pattern applies at the current position
039         * of the stream. May modify the stream's position.
040         */
041        protected abstract boolean conditionApplies(TokenStream stream);
042
043}