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.http.conn.util;
29
30 /**
31 * A collection of utilities relating to Domain Name System.
32 *
33 * @since 4.5
34 */
35 public class DnsUtils {
36
37 private DnsUtils() {
38 }
39
40 private static boolean isUpper(final char c) {
41 return c >= 'A' && c <= 'Z';
42 }
43
44 public static String normalize(final String s) {
45 if (s == null) {
46 return null;
47 }
48 int pos = 0;
49 int remaining = s.length();
50 while (remaining > 0) {
51 if (isUpper(s.charAt(pos))) {
52 break;
53 }
54 pos++;
55 remaining--;
56 }
57 if (remaining > 0) {
58 final StringBuilder buf = new StringBuilder(s.length());
59 buf.append(s, 0, pos);
60 while (remaining > 0) {
61 final char c = s.charAt(pos);
62 if (isUpper(c)) {
63 buf.append((char) (c + ('a' - 'A')));
64 } else {
65 buf.append(c);
66 }
67 pos++;
68 remaining--;
69 }
70 return buf.toString();
71 } else {
72 return s;
73 }
74 }
75
76 }