DatePatternToRegexUtil.java

/**
 * Logback: the reliable, generic, fast and flexible logging framework.
 * Copyright (C) 1999-2013, QOS.ch. All rights reserved.
 *
 * This program and the accompanying materials are dual-licensed under
 * either the terms of the Eclipse Public License v1.0 as published by
 * the Eclipse Foundation
 *
 *   or (per the licensee's choosing)
 *
 * under the terms of the GNU Lesser General Public License version 2.1
 * as published by the Free Software Foundation.
 */
package ch.qos.logback.core.util;

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.List;

/**
 * This class is concerned with computing a regex corresponding to a date
 * pattern (in {@link SimpleDateFormat} format).
 *
 * @author Ceki Gülcü
 */
public class DatePatternToRegexUtil {

  final String datePattern;
  final int datePatternLength;
  final CharSequenceToRegexMapper regexMapper = new CharSequenceToRegexMapper();

  public DatePatternToRegexUtil(String datePattern) {
    this.datePattern = datePattern;
    datePatternLength = datePattern.length();
  }

  public String toRegex() {
    List<CharSequenceState> charSequenceList = tokenize();
    StringBuilder sb = new StringBuilder();
    for (CharSequenceState seq : charSequenceList) {
      sb.append(regexMapper.toRegex(seq));
    }
    return sb.toString();
  }

  private List<CharSequenceState> tokenize() {
    List<CharSequenceState> sequenceList = new ArrayList<CharSequenceState>();

    CharSequenceState lastCharSequenceState = null;

    for (int i = 0; i < datePatternLength; i++) {
      char t = datePattern.charAt(i);
      if (lastCharSequenceState == null || lastCharSequenceState.c != t) {
        lastCharSequenceState = new CharSequenceState(t);
        sequenceList.add(lastCharSequenceState);
      } else {
        lastCharSequenceState.incrementOccurrences();
      }
    }
    return sequenceList;
  }
}