content: /*
  * Conditions Of Use 
  * 
  * This software was developed by employees of the National Institute of
  * Standards and Technology (NIST), an agency of the Federal Government.
  * Pursuant to title 15 Untied States Code Section 105, works of NIST
  * employees are not subject to copyright protection in the United States
  * and are considered to be in the public domain.  As a result, a formal
  * license is not needed to use the software.
  * 
  * This software is provided by NIST as a service and is expressly
  * provided "AS IS."  NIST MAKES NO WARRANTY OF ANY KIND, EXPRESS, IMPLIED
  * OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTY OF
  * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT
  * AND DATA ACCURACY.  NIST does not warrant or make any representations
  * regarding the use of the software or the results thereof, including but
  * not limited to the correctness, accuracy, reliability or usefulness of
  * the software.
  * 
  * Permission to use this software is contingent upon your acceptance
  * of the terms of this agreement
  *  
  * .
  * 
  */
  package gov2.nist.javax2.sip.address;
  
  import java.io.UnsupportedEncodingException;
  
  /**
   * Copied from Apache Excalibur project.
   * Source code available at http://www.google.com/codesearch?hl=en&q=+excalibur+decodePath+show:sK_gDY0W5Rw:OTjCHAiSuF0:th3BdHtpX20&sa=N&cd=1&ct=rc&cs_p=http://apache.edgescape.com/excalibur/excalibur-sourceresolve/source/excalibur-sourceresolve-1.1-src.zip&cs_f=excalibur-sourceresolve-1.1/src/java/org/apache/excalibur/source/SourceUtil.java
   * @author <A HREF="mailto:jean.deruelle@gmail.com">Jean Deruelle</A> 
   *
   */
  public class RFC2396UrlDecoder {
  
      /**
       * Decode a path.
       *
       * <p>Interprets %XX (where XX is hexadecimal number) as UTF-8 encoded bytes.
       * <p>The validity of the input path is not checked (i.e. characters that
       * were not encoded will not be reported as errors).
       * <p>This method differs from URLDecoder.decode in that it always uses UTF-8
       * (while URLDecoder uses the platform default encoding, often ISO-8859-1),
       * and doesn't translate + characters to spaces.
       *
       * @param uri the path to decode
       * @return the decoded path
       */
      public static String decode(String uri) {
          StringBuffer translatedUri = new StringBuffer(uri.length());
          byte[] encodedchars = new byte[uri.length() / 3];
          int i = 0;
          int length = uri.length();
          int encodedcharsLength = 0;
          while (i < length) {
              if (uri.charAt(i) == '%') {
                  //we must process all consecutive %-encoded characters in one go, because they represent
                  //an UTF-8 encoded string, and in UTF-8 one character can be encoded as multiple bytes
                  while (i < length && uri.charAt(i) == '%') {
                      if (i + 2 < length) {
                          try {
                              byte x = (byte)Integer.parseInt(uri.substring(i + 1, i + 3), 16);
                              encodedchars[encodedcharsLength] = x;
                          } catch (NumberFormatException e) {
                              throw new IllegalArgumentException("Illegal hex characters in pattern %" + uri.substring(i + 1, i + 3));
                          }
                          encodedcharsLength++;
                          i += 3;
                      } else {
                          throw new IllegalArgumentException("% character should be followed by 2 hexadecimal characters.");
                      }
                  }
                  try {
                      String translatedPart = new String(encodedchars, 0, encodedcharsLength, "UTF-8");
                      translatedUri.append(translatedPart);
                  } catch (UnsupportedEncodingException e) {
                      //the situation that UTF-8 is not supported is quite theoretical, so throw a runtime exception
                      throw new RuntimeException("Problem in decodePath: UTF-8 encoding not supported.");
                  }
                  encodedcharsLength = 0;
              } else {
                  //a normal character
                  translatedUri.append(uri.charAt(i));
                  i++;
              }
          }
          return translatedUri.toString();
      }
  }