Base64


1   /**
2    * Copyright (C) 2003-2005 Funambol
3    *
4    * This program is free software; you can redistribute it and/or modify
5    * it under the terms of the GNU General Public License as published by
6    * the Free Software Foundation; either version 2 of the License, or
7    * (at your option) any later version.
8    *
9    * This program is distributed in the hope that it will be useful,
10   * but WITHOUT ANY WARRANTY; without even the implied warranty of
11   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12   * GNU General Public License for more details.
13   *
14   * You should have received a copy of the GNU General Public License
15   * along with this program; if not, write to the Free Software
16   * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA 
17   */
18  
19  package sync4j.syncclient.common;
20  
21  /**
22   * $Id: Base64.java,v 1.2 2005/01/19 10:58:31 fabius Exp $
23   *
24   * Just repackaged into sync4j.syncclient.common
25   */
26  public class Base64 {
27      private static final byte[] encodingTable = {
28          (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
29          (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
30          (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
31          (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
32          (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
33          (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
34          (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
35          (byte)'v',
36          (byte)'w', (byte)'x', (byte)'y', (byte)'z',
37          (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
38          (byte)'7', (byte)'8', (byte)'9',
39          (byte)'+', (byte)'/'
40      };
41  
42      /**
43       * encode the input data producong a base 64 encoded byte array.
44       *
45       * @return a byte array containing the base 64 encoded data.
46       */
47      public static byte[] encode(
48      byte[]  data) {
49          byte[]  bytes;
50  
51          int modulus = data.length % 3;
52          if (modulus == 0) {
53              bytes = new byte[4 * data.length / 3];
54          }
55          else {
56              bytes = new byte[4 * ((data.length / 3) + 1)];
57          }
58  
59          int dataLength = (data.length - modulus);
60          int a1, a2, a3;
61          for (int i = 0, j = 0; i < dataLength; i += 3, j += 4) {
62              a1 = data[i] & 0xff;
63              a2 = data[i + 1] & 0xff;
64              a3 = data[i + 2] & 0xff;
65  
66              bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
67              bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
68              bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
69              bytes[j + 3] = encodingTable[a3 & 0x3f];
70          }
71  
72                  /*
73                   * process the tail end.
74                   */
75          int b1, b2, b3;
76          int d1, d2;
77  
78          switch (modulus) {
79              case 0:     /* nothing left to do */
80                  break;
81              case 1:
82                  d1 = data[data.length - 1] & 0xff;
83                  b1 = (d1 >>> 2) & 0x3f;
84                  b2 = (d1 << 4) & 0x3f;
85  
86                  bytes[bytes.length - 4] = encodingTable[b1];
87                  bytes[bytes.length - 3] = encodingTable[b2];
88                  bytes[bytes.length - 2] = (byte)'=';
89                  bytes[bytes.length - 1] = (byte)'=';
90                  break;
91              case 2:
92                  d1 = data[data.length - 2] & 0xff;
93                  d2 = data[data.length - 1] & 0xff;
94  
95                  b1 = (d1 >>> 2) & 0x3f;
96                  b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
97                  b3 = (d2 << 2) & 0x3f;
98  
99                  bytes[bytes.length - 4] = encodingTable[b1];
100                 bytes[bytes.length - 3] = encodingTable[b2];
101                 bytes[bytes.length - 2] = encodingTable[b3];
102                 bytes[bytes.length - 1] = (byte)'=';
103                 break;
104         }
105 
106         return bytes;
107     }
108 
109         /*
110          * set up the decoding table.
111          */
112     private static final byte[] decodingTable;
113 
114     static {
115         decodingTable = new byte[128];
116 
117         for (int i = 'A'; i <= 'Z'; i++) {
118             decodingTable[i] = (byte)(i - 'A');
119         }
120 
121         for (int i = 'a'; i <= 'z'; i++) {
122             decodingTable[i] = (byte)(i - 'a' + 26);
123         }
124 
125         for (int i = '0'; i <= '9'; i++) {
126             decodingTable[i] = (byte)(i - '0' + 52);
127         }
128 
129         decodingTable['+'] = 62;
130         decodingTable['/'] = 63;
131     }
132 
133     /**
134      * decode the base 64 encoded input data.
135      *
136      * @return a byte array representing the decoded data.
137      */
138     public static byte[] decode(
139     byte[]  data) {
140         byte[]  bytes;
141         byte    b1, b2, b3, b4;
142 
143         if (data[data.length - 2] == '=') {
144             bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
145         }
146         else if (data[data.length - 1] == '=') {
147             bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
148         }
149         else {
150             bytes = new byte[((data.length / 4) * 3)];
151         }
152 
153         for (int i = 0, j = 0; i < data.length - 4; i += 4, j += 3) {
154             b1 = decodingTable[data[i]];
155             b2 = decodingTable[data[i + 1]];
156             b3 = decodingTable[data[i + 2]];
157             b4 = decodingTable[data[i + 3]];
158 
159             bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
160             bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
161             bytes[j + 2] = (byte)((b3 << 6) | b4);
162         }
163 
164         if (data[data.length - 2] == '=') {
165             b1 = decodingTable[data[data.length - 4]];
166             b2 = decodingTable[data[data.length - 3]];
167 
168             bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
169         }
170         else if (data[data.length - 1] == '=') {
171             b1 = decodingTable[data[data.length - 4]];
172             b2 = decodingTable[data[data.length - 3]];
173             b3 = decodingTable[data[data.length - 2]];
174 
175             bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
176             bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
177         }
178         else {
179             b1 = decodingTable[data[data.length - 4]];
180             b2 = decodingTable[data[data.length - 3]];
181             b3 = decodingTable[data[data.length - 2]];
182             b4 = decodingTable[data[data.length - 1]];
183 
184             bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
185             bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
186             bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
187         }
188 
189         return bytes;
190     }
191 
192     /**
193      * decode the base 64 encoded String data.
194      *
195      * @return a byte array representing the decoded data.
196      */
197     public static byte[] decode(
198     String    data) {
199         byte[]  bytes;
200         byte    b1, b2, b3, b4;
201 
202         if (data.charAt(data.length() - 2) == '=') {
203             bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
204         }
205         else if (data.charAt(data.length() - 1) == '=') {
206             bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
207         }
208         else {
209             bytes = new byte[((data.length() / 4) * 3)];
210         }
211 
212         for (int i = 0, j = 0; i < data.length() - 4; i += 4, j += 3) {
213             b1 = decodingTable[data.charAt(i)];
214             b2 = decodingTable[data.charAt(i + 1)];
215             b3 = decodingTable[data.charAt(i + 2)];
216             b4 = decodingTable[data.charAt(i + 3)];
217 
218             bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
219             bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
220             bytes[j + 2] = (byte)((b3 << 6) | b4);
221         }
222 
223         if (data.charAt(data.length() - 2) == '=') {
224             b1 = decodingTable[data.charAt(data.length() - 4)];
225             b2 = decodingTable[data.charAt(data.length() - 3)];
226 
227             bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
228         }
229         else if (data.charAt(data.length() - 1) == '=') {
230             b1 = decodingTable[data.charAt(data.length() - 4)];
231             b2 = decodingTable[data.charAt(data.length() - 3)];
232             b3 = decodingTable[data.charAt(data.length() - 2)];
233 
234             bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
235             bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
236         }
237         else {
238             b1 = decodingTable[data.charAt(data.length() - 4)];
239             b2 = decodingTable[data.charAt(data.length() - 3)];
240             b3 = decodingTable[data.charAt(data.length() - 2)];
241             b4 = decodingTable[data.charAt(data.length() - 1)];
242 
243             bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
244             bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
245             bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
246         }
247 
248         return bytes;
249     }
250 }
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