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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  }