001/* URLDecoder.java -- Class to decode URL's from encoded form.
002   Copyright (C) 1998, 1999, 2000, 2001 Free Software Foundation, Inc.
003
004This file is part of GNU Classpath.
005
006GNU Classpath is free software; you can redistribute it and/or modify
007it under the terms of the GNU General Public License as published by
008the Free Software Foundation; either version 2, or (at your option)
009any later version.
010
011GNU Classpath is distributed in the hope that it will be useful, but
012WITHOUT ANY WARRANTY; without even the implied warranty of
013MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
014General Public License for more details.
015
016You should have received a copy of the GNU General Public License
017along with GNU Classpath; see the file COPYING.  If not, write to the
018Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
01902110-1301 USA.
020
021Linking this library statically or dynamically with other modules is
022making a combined work based on this library.  Thus, the terms and
023conditions of the GNU General Public License cover the whole
024combination.
025
026As a special exception, the copyright holders of this library give you
027permission to link this library with independent modules to produce an
028executable, regardless of the license terms of these independent
029modules, and to copy and distribute the resulting executable under
030terms of your choice, provided that you also meet, for each linked
031independent module, the terms and conditions of the license of that
032module.  An independent module is a module which is not derived from
033or based on this library.  If you modify this library, you may extend
034this exception to your version of the library, but you are not
035obligated to do so.  If you do not wish to do so, delete this
036exception statement from your version. */
037
038package java.net;
039
040import gnu.java.lang.CPStringBuilder;
041
042import java.io.UnsupportedEncodingException;
043
044
045/**
046 * This utility class contains static methods that converts a
047 * string encoded in the x-www-form-urlencoded format to the original
048 * text.  The x-www-form-urlencoded format replaces certain disallowed
049 * characters with encoded equivalents.  All upper case and lower case
050 * letters in the US alphabet remain as is, the space character (' ')
051 * is replaced with '+' sign, and all other characters are converted to a
052 * "%XX" format where XX is the hexadecimal representation of that character
053 * in a given character encoding (default is "UTF-8").
054 * <p>
055 * This method is very useful for decoding strings sent to CGI scripts
056 *
057 * Written using on-line Java Platform 1.2/1.4 API Specification.
058 * Status:  Believed complete and correct.
059 *
060 * @since 1.2
061 *
062 * @author Warren Levy (warrenl@cygnus.com)
063 * @author Aaron M. Renn (arenn@urbanophile.com) (documentation comments)
064 * @author Mark Wielaard (mark@klomp.org)
065 */
066public class URLDecoder
067{
068  /**
069   * Public contructor. Note that this class has only static methods.
070   */
071  public URLDecoder()
072  {
073  }
074
075  /**
076   * This method translates the passed in string from x-www-form-urlencoded
077   * format using the default encoding "UTF-8" to decode the hex encoded
078   * unsafe characters.
079   *
080   * @param s the String to convert
081   *
082   * @return the converted String
083   *
084   * @deprecated
085   */
086  public static String decode(String s)
087  {
088    try
089      {
090        return decode(s, "UTF-8");
091      }
092    catch (UnsupportedEncodingException uee)
093      {
094        // Should never happen since UTF-8 encoding should always be supported
095        return s;
096      }
097  }
098
099  /**
100   * This method translates the passed in string from x-www-form-urlencoded
101   * format using the given character encoding to decode the hex encoded
102   * unsafe characters.
103   *
104   * This implementation will decode the string even if it contains
105   * unsafe characters (characters that should have been encoded) or if the
106   * two characters following a % do not represent a hex encoded byte.
107   * In those cases the unsafe character or the % character will be added
108   * verbatim to the decoded result.
109   *
110   * @param s the String to convert
111   * @param encoding the character encoding to use the decode the hex encoded
112   *        unsafe characters
113   *
114   * @return the converted String
115   *
116   * @exception UnsupportedEncodingException If the named encoding is not
117   * supported
118   *
119   * @since 1.4
120   */
121  public static String decode(String s, String encoding)
122    throws UnsupportedEncodingException
123  {
124    // First convert all '+' characters to spaces.
125    String str = s.replace('+', ' ');
126
127    // Then go through the whole string looking for byte encoded characters
128    int i;
129    int start = 0;
130    byte[] bytes = null;
131    int length = str.length();
132    CPStringBuilder result = new CPStringBuilder(length);
133    while ((i = str.indexOf('%', start)) >= 0)
134      {
135        // Add all non-encoded characters to the result buffer
136        result.append(str.substring(start, i));
137        start = i;
138
139        // Get all consecutive encoded bytes
140        while ((i + 2 < length) && (str.charAt(i) == '%'))
141          i += 3;
142
143        // Decode all these bytes
144        if ((bytes == null) || (bytes.length < ((i - start) / 3)))
145          bytes = new byte[((i - start) / 3)];
146
147        int index = 0;
148        try
149          {
150            while (start < i)
151              {
152                String sub = str.substring(start + 1, start + 3);
153                bytes[index] = (byte) Integer.parseInt(sub, 16);
154                index++;
155                start += 3;
156              }
157          }
158        catch (NumberFormatException nfe)
159          {
160            // One of the hex encoded strings was bad
161          }
162
163        // Add the bytes as characters according to the given encoding
164        result.append(new String(bytes, 0, index, encoding));
165
166        // Make sure we skip to just after a % sign
167        // There might not have been enough encoded characters after the %
168        // or the hex chars were not actually hex chars (NumberFormatException)
169        if (start < length && s.charAt(start) == '%')
170          {
171            result.append('%');
172            start++;
173          }
174      }
175
176    // Add any characters left
177    if (start < str.length())
178      result.append(str.substring(start));
179
180    return result.toString();
181  }
182} // class URLDecoder