1/*
2* Conditions Of Use
3*
4* This software was developed by employees of the National Institute of
5* Standards and Technology (NIST), an agency of the Federal Government.
6* Pursuant to title 15 Untied States Code Section 105, works of NIST
7* employees are not subject to copyright protection in the United States
8* and are considered to be in the public domain.  As a result, a formal
9* license is not needed to use the software.
10*
11* This software is provided by NIST as a service and is expressly
12* provided "AS IS."  NIST MAKES NO WARRANTY OF ANY KIND, EXPRESS, IMPLIED
13* OR STATUTORY, INCLUDING, WITHOUT LIMITATION, THE IMPLIED WARRANTY OF
14* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, NON-INFRINGEMENT
15* AND DATA ACCURACY.  NIST does not warrant or make any representations
16* regarding the use of the software or the results thereof, including but
17* not limited to the correctness, accuracy, reliability or usefulness of
18* the software.
19*
20* Permission to use this software is contingent upon your acceptance
21* of the terms of this agreement
22*
23* .
24*
25*/
26package gov.nist.javax.sip.address;
27
28import java.io.UnsupportedEncodingException;
29
30/**
31 * Copied from Apache Excalibur project.
32 * 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
33 * @author <A HREF="mailto:jean.deruelle@gmail.com">Jean Deruelle</A>
34 *
35 */
36public class RFC2396UrlDecoder {
37
38    /**
39     * Decode a path.
40     *
41     * <p>Interprets %XX (where XX is hexadecimal number) as UTF-8 encoded bytes.
42     * <p>The validity of the input path is not checked (i.e. characters that
43     * were not encoded will not be reported as errors).
44     * <p>This method differs from URLDecoder.decode in that it always uses UTF-8
45     * (while URLDecoder uses the platform default encoding, often ISO-8859-1),
46     * and doesn't translate + characters to spaces.
47     *
48     * @param uri the path to decode
49     * @return the decoded path
50     */
51    public static String decode(String uri) {
52        StringBuffer translatedUri = new StringBuffer(uri.length());
53        byte[] encodedchars = new byte[uri.length() / 3];
54        int i = 0;
55        int length = uri.length();
56        int encodedcharsLength = 0;
57        while (i < length) {
58            if (uri.charAt(i) == '%') {
59                //we must process all consecutive %-encoded characters in one go, because they represent
60                //an UTF-8 encoded string, and in UTF-8 one character can be encoded as multiple bytes
61                while (i < length && uri.charAt(i) == '%') {
62                    if (i + 2 < length) {
63                        try {
64                            byte x = (byte)Integer.parseInt(uri.substring(i + 1, i + 3), 16);
65                            encodedchars[encodedcharsLength] = x;
66                        } catch (NumberFormatException e) {
67                            throw new IllegalArgumentException("Illegal hex characters in pattern %" + uri.substring(i + 1, i + 3));
68                        }
69                        encodedcharsLength++;
70                        i += 3;
71                    } else {
72                        throw new IllegalArgumentException("% character should be followed by 2 hexadecimal characters.");
73                    }
74                }
75                try {
76                    String translatedPart = new String(encodedchars, 0, encodedcharsLength, "UTF-8");
77                    translatedUri.append(translatedPart);
78                } catch (UnsupportedEncodingException e) {
79                    //the situation that UTF-8 is not supported is quite theoretical, so throw a runtime exception
80                    throw new RuntimeException("Problem in decodePath: UTF-8 encoding not supported.");
81                }
82                encodedcharsLength = 0;
83            } else {
84                //a normal character
85                translatedUri.append(uri.charAt(i));
86                i++;
87            }
88        }
89        return translatedUri.toString();
90    }
91}