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From rdon...@apache.org
Subject cvs commit: jakarta-commons/digester/src/java/org/apache/commons/digester SimpleRegexMatcher.java
Date Wed, 02 Apr 2003 19:04:42 GMT
rdonkin     2003/04/02 11:04:42

  Added:       digester/src/java/org/apache/commons/digester
                        SimpleRegexMatcher.java
  Log:
  Added new Rule implementation based on a pluggable regex implementation. Also test case
and a simple regex matching implementation
  
  Revision  Changes    Path
  1.1                  jakarta-commons/digester/src/java/org/apache/commons/digester/SimpleRegexMatcher.java
  
  Index: SimpleRegexMatcher.java
  ===================================================================
  /*
   * $Header: /home/cvs/jakarta-commons/digester/src/java/org/apache/commons/digester/SimpleRegexMatcher.java,v
1.1 2003/04/02 19:04:42 rdonkin Exp $
   * $Revision: 1.1 $
   * $Date: 2003/04/02 19:04:42 $
   *
   * ====================================================================
   *
   * The Apache Software License, Version 1.1
   *
   * Copyright (c) 1999-2003 The Apache Software Foundation.  All rights
   * reserved.
   *
   * Redistribution and use in source and binary forms, with or without
   * modification, are permitted provided that the following conditions
   * are met:
   *
   * 1. Redistributions of source code must retain the above copyright
   *    notice, this list of conditions and the following disclaimer.
   *
   * 2. Redistributions in binary form must reproduce the above copyright
   *    notice, this list of conditions and the following disclaimer in
   *    the documentation and/or other materials provided with the
   *    distribution.
   *
   * 3. The end-user documentation included with the redistribution, if
   *    any, must include the following acknowlegement:
   *       "This product includes software developed by the
   *        Apache Software Foundation (http://www.apache.org/)."
   *    Alternately, this acknowlegement may appear in the software itself,
   *    if and wherever such third-party acknowlegements normally appear.
   *
   * 4. The names "The Jakarta Project", "Commons", and "Apache Software
   *    Foundation" must not be used to endorse or promote products derived
   *    from this software without prior written permission. For written
   *    permission, please contact apache@apache.org.
   *
   * 5. Products derived from this software may not be called "Apache"
   *    nor may "Apache" appear in their names without prior written
   *    permission of the Apache Group.
   *
   * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
   * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
   * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
   * DISCLAIMED.  IN NO EVENT SHALL THE APACHE SOFTWARE FOUNDATION OR
   * ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
   * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
   * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
   * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
   * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
   * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
   * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
   * SUCH DAMAGE.
   * ====================================================================
   *
   * This software consists of voluntary contributions made by many
   * individuals on behalf of the Apache Software Foundation.  For more
   * information on the Apache Software Foundation, please see
   * <http://www.apache.org/>.
   *
   */
  
  package org.apache.commons.digester;
  
  import java.util.List;
  
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  
  /**
   * <p>Simple regex pattern matching algorithm.</p>
   * 
   * <p>This uses just two wildcards:
   * <ul>
   * 	<li><code>*</code> matches any sequence of none, one or more characters
   * 	<li><code>?</code> matches any one character 
   * </ul>
   * Escaping these wildcards is not supported .</p>
   *
   * @author Robert Burrell Donkin
   * @version $Revision: 1.1 $ $Date: 2003/04/02 19:04:42 $
   */
  
  public class SimpleRegexMatcher extends RegexMatcher {
      
      // --------------------------------------------------------- Fields
      
      /** Default log (class wide) */
      private static final Log baseLog = LogFactory.getLog(SimpleRegexMatcher.class);
      
      /** Custom log (can be set per object) */
      private Log log = baseLog;
      
      // --------------------------------------------------------- Properties
      
      /** 
       * Gets the <code>Log</code> implementation.
       */
      public Log getLog() {
          return log;
      }
      
      /**
       * Sets the current <code>Log</code> implementation used by this class.
       */
      public void setLog(Log log) {
          this.log = log;
      }
      
      // --------------------------------------------------------- Public Methods
      
      /** 
       * Matches using simple regex algorithm.
       * 
       *
       * @param basePattern the standard digester path representing the element
       * @param regexPattern the regex pattern the path will be tested against
       * @return true if the given pattern matches the given path
       */
      public boolean match(String basePattern, String regexPattern) {
          // check for nulls
          if (basePattern == null || regexPattern == null) {
              return false;
          }
          return match(basePattern, regexPattern, 0, 0);
      }
      
      // --------------------------------------------------------- Implementations Methods
      
      /**
       * Implementation of regex matching algorithm.
       * This calls itself recursively.
       */
      private boolean match(String basePattern, String regexPattern, int baseAt, int regexAt)
{
          if (log.isTraceEnabled()) {
              log.trace("Base: " + basePattern);
              log.trace("Regex: " + regexPattern);
              log.trace("Base@" + baseAt);
              log.trace("Regex@" + regexAt);
          }
          
          // check bounds
          if (regexAt >= regexPattern.length()) {
              // maybe we've got a match
              if (baseAt >= basePattern.length()) {
                  // ok!
                  return true;
              }
              // run out early
              return false;
              
          } else {
              if (baseAt >= basePattern.length()) {
                  // run out early
                  return false;
              }
          }
          
          // ok both within bounds
          char regexCurrent = regexPattern.charAt(regexAt);
          switch (regexCurrent) {
              case '*':
                  // this is the tricky case
                  // check for terminal 
                  if (++regexAt >= regexPattern.length()) {
                      // this matches anything let - so return true
                      return true;
                  }
                  // go through every subsequent apperance of the next character
                  // and so if the rest of the regex matches
                  char nextRegex = regexPattern.charAt(regexAt);
                  if (log.isTraceEnabled()) {
                      log.trace("Searching for next '" + nextRegex + "' char");
                  }
                  int nextMatch = basePattern.indexOf(nextRegex, baseAt);
                  while (nextMatch != -1) {
                      if (log.isTraceEnabled()) {
                          log.trace("Trying '*' match@" + nextMatch);
                      }
                      if (match(basePattern, regexPattern, nextMatch, regexAt)) {
                          return true;
                      }
                      nextMatch = basePattern.indexOf(nextRegex, nextMatch + 1);
                  }
                  log.trace("No matches found.");
                  return false;
                  
              case '?':
                  // this matches anything
                  return match(basePattern, regexPattern, ++baseAt, ++regexAt);
              
              default:
                  if (log.isTraceEnabled()) {
                      log.trace("Camparing " + regexCurrent + " to " + basePattern.charAt(baseAt));
                  }
                  if (regexCurrent == basePattern.charAt(baseAt)) {
                      // still got more to go
                      return match(basePattern, regexPattern, ++baseAt, ++regexAt);
                  }
                  return false;
          }
      }
  }
  
  
  

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