001    /*
002     * Sonar, open source software quality management tool.
003     * Copyright (C) 2008-2012 SonarSource
004     * mailto:contact AT sonarsource DOT com
005     *
006     * Sonar is free software; you can redistribute it and/or
007     * modify it under the terms of the GNU Lesser General Public
008     * License as published by the Free Software Foundation; either
009     * version 3 of the License, or (at your option) any later version.
010     *
011     * Sonar is distributed in the hope that it will be useful,
012     * but WITHOUT ANY WARRANTY; without even the implied warranty of
013     * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014     * Lesser General Public License for more details.
015     *
016     * You should have received a copy of the GNU Lesser General Public
017     * License along with Sonar; if not, write to the Free Software
018     * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02
019     */
020    package org.sonar.channel;
021    
022    import java.util.regex.Matcher;
023    import java.util.regex.Pattern;
024    
025    /**
026     * The RegexChannel can be used to be called each time the next characters in the character stream match a regular expression
027     */
028    public abstract class RegexChannel<OUTPUT> extends Channel<OUTPUT> {
029    
030      private final StringBuilder tmpBuilder = new StringBuilder();
031      private final Matcher matcher;
032      private final String regex;
033    
034      /**
035       * Create a RegexChannel object with the required regular expression
036       * 
037       * @param regex
038       *          regular expression to be used to try matching the next characters in the stream
039       */
040      public RegexChannel(String regex) {
041        matcher = Pattern.compile(regex).matcher("");
042        this.regex = regex;
043      }
044    
045      @Override
046      public final boolean consume(CodeReader code, OUTPUT output) {
047        try {
048          if (code.popTo(matcher, tmpBuilder) > 0) {
049            consume(tmpBuilder, output);
050            tmpBuilder.delete(0, tmpBuilder.length());
051            return true;
052          }
053          return false;
054        } catch (StackOverflowError e) {
055          throw new IllegalArgumentException(
056              "The regular expression "
057                  + regex
058                  + " has led to a stack overflow error. "
059                  + "This error is certainly due to an inefficient use of alternations. See http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=5050507",
060              e);
061        }
062      }
063    
064      /**
065       * The consume method is called each time the regular expression used to create the RegexChannel object matches the next characters in the
066       * character streams.
067       * 
068       * @param token
069       *          the token consumed in the character stream and matching the regular expression
070       * @param the
071       *          OUPUT object which can be optionally fed
072       */
073      protected abstract void consume(CharSequence token, OUTPUT output);
074    }