Base64Converter


1   /*
2    *  Licensed to the Apache Software Foundation (ASF) under one or more
3    *  contributor license agreements.  See the NOTICE file distributed with
4    *  this work for additional information regarding copyright ownership.
5    *  The ASF licenses this file to You under the Apache License, Version 2.0
6    *  (the "License"); you may not use this file except in compliance with
7    *  the License.  You may obtain a copy of the License at
8    *
9    *      http://www.apache.org/licenses/LICENSE-2.0
10   *
11   *  Unless required by applicable law or agreed to in writing, software
12   *  distributed under the License is distributed on an "AS IS" BASIS,
13   *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
14   *  See the License for the specific language governing permissions and
15   *  limitations under the License.
16   *
17   */
18  package org.apache.tools.ant.util;
19  
20  /**
21   * BASE 64 encoding of a String or an array of bytes.
22   *
23   * Based on RFC 1421.
24   *
25   **/
26  public class Base64Converter {
27  
28      private static final char[] ALPHABET = {
29          'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H',  //  0 to  7
30          'I', 'J', 'K', 'L', 'M', 'N', 'O', 'P',  //  8 to 15
31          'Q', 'R', 'S', 'T', 'U', 'V', 'W', 'X',  // 16 to 23
32          'Y', 'Z', 'a', 'b', 'c', 'd', 'e', 'f',  // 24 to 31
33          'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',  // 32 to 39
34          'o', 'p', 'q', 'r', 's', 't', 'u', 'v',  // 40 to 47
35          'w', 'x', 'y', 'z', '0', '1', '2', '3',  // 48 to 55
36          '4', '5', '6', '7', '8', '9', '+', '/'}; // 56 to 63
37  
38      // CheckStyle:ConstantNameCheck OFF - bc
39      /** Provided for BC purposes */
40      public static final char[] alphabet = ALPHABET;
41      // CheckStyle:ConstantNameCheck ON
42  
43  
44      /**
45       * Encode a string into base64 encoding.
46       * @param s the string to encode.
47       * @return the encoded string.
48       */
49      public String   encode(String   s) {
50          return encode(s.getBytes());
51      }
52  
53      /**
54       * Encode a byte array into base64 encoding.
55       * @param octetString the byte array to encode.
56       * @return the encoded string.
57       */
58      public String   encode(byte[] octetString) {
59          int bits24;
60          int bits6;
61  
62          char[] out = new char[((octetString.length - 1) / 3 + 1) * 4];
63          int outIndex = 0;
64          int i = 0;
65  
66          while ((i + 3) <= octetString.length) {
67              // store the octets
68              bits24 = (octetString[i++] & 0xFF) << 16;
69              bits24 |= (octetString[i++] & 0xFF) << 8;
70              bits24 |= octetString[i++];
71  
72              bits6 = (bits24 & 0x00FC0000) >> 18;
73              out[outIndex++] = ALPHABET[bits6];
74              bits6 = (bits24 & 0x0003F000) >> 12;
75              out[outIndex++] = ALPHABET[bits6];
76              bits6  = (bits24 & 0x00000FC0) >> 6;
77              out[outIndex++] = ALPHABET[bits6];
78              bits6 = (bits24 & 0x0000003F);
79              out[outIndex++] = ALPHABET[bits6];
80          }
81          if (octetString.length - i == 2) {
82              // store the octets
83              bits24 = (octetString[i] & 0xFF) << 16;
84              bits24 |= (octetString[i + 1] & 0xFF) << 8;
85              bits6 = (bits24 & 0x00FC0000) >> 18;
86              out[outIndex++] = ALPHABET[bits6];
87              bits6 = (bits24 & 0x0003F000) >> 12;
88              out[outIndex++] = ALPHABET[bits6];
89              bits6 = (bits24 & 0x00000FC0) >> 6;
90              out[outIndex++] = ALPHABET[bits6];
91  
92              // padding
93              out[outIndex++] = '=';
94          } else if (octetString.length - i == 1) {
95              // store the octets
96              bits24 = (octetString[i] & 0xFF) << 16;
97              bits6 = (bits24 & 0x00FC0000) >> 18;
98              out[outIndex++] = ALPHABET[bits6];
99              bits6 = (bits24 & 0x0003F000) >> 12;
100             out[outIndex++] = ALPHABET[bits6];
101 
102             // padding
103             out[outIndex++] = '=';
104             out[outIndex++] = '=';
105         }
106         return new String  (out);
107     }
108 }
109
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