1 /*
2 * ====================================================================
3 * Licensed to the Apache Software Foundation (ASF) under one
4 * or more contributor license agreements. See the NOTICE file
5 * distributed with this work for additional information
6 * regarding copyright ownership. The ASF licenses this file
7 * to you under the Apache License, Version 2.0 (the
8 * "License"); you may not use this file except in compliance
9 * with the License. You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing,
14 * software distributed under the License is distributed on an
15 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
16 * KIND, either express or implied. See the License for the
17 * specific language governing permissions and limitations
18 * under the License.
19 * ====================================================================
20 *
21 * This software consists of voluntary contributions made by many
22 * individuals on behalf of the Apache Software Foundation. For more
23 * information on the Apache Software Foundation, please see
24 * <http://www.apache.org/>.
25 *
26 */
27
28 package org.apache.hc.client5.http.utils;
29
30 import java.net.IDN;
31
32 /**
33 * A collection of utilities relating to Domain Name System.
34 *
35 * @since 4.5
36 */
37 public class DnsUtils {
38
39 private DnsUtils() {
40 }
41
42 private static boolean isUpper(final char c) {
43 return c >= 'A' && c <= 'Z';
44 }
45
46 public static String normalize(final String s) {
47 if (s == null) {
48 return null;
49 }
50 int pos = 0;
51 int remaining = s.length();
52 while (remaining > 0) {
53 if (isUpper(s.charAt(pos))) {
54 break;
55 }
56 pos++;
57 remaining--;
58 }
59 if (remaining > 0) {
60 final StringBuilder buf = new StringBuilder(s.length());
61 buf.append(s, 0, pos);
62 while (remaining > 0) {
63 final char c = s.charAt(pos);
64 if (isUpper(c)) {
65 buf.append((char) (c + ('a' - 'A')));
66 } else {
67 buf.append(c);
68 }
69 pos++;
70 remaining--;
71 }
72 return buf.toString();
73 }
74 return s;
75 }
76
77 /**
78 * Decodes to Unicode and normalizes the given DNS name.
79 * @since 5.5
80 */
81 public static String normalizeUnicode(final String s) {
82 if (s == null) {
83 return null;
84 }
85 String decoded;
86 try {
87 decoded = IDN.toUnicode(s);
88 } catch (final IllegalArgumentException ignore) {
89 decoded = s;
90 }
91 return normalize(decoded);
92 }
93
94 }