Base64


1   /*
2    *  SSL-Explorer
3    *
4    *  Copyright (C) 2003-2006 3SP LTD. All Rights Reserved
5    *
6    *  This program is free software; you can redistribute it and/or
7    *  modify it under the terms of the GNU General Public License
8    *  as published by the Free Software Foundation; either version 2 of
9    *  the License, or (at your option) any later version.
10   *  This program is distributed in the hope that it will be useful,
11   *  but WITHOUT ANY WARRANTY; without even the implied warranty of
12   *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
13   *  GNU General Public License for more details.
14   *
15   *  You should have received a copy of the GNU General Public
16   *  License along with this program; if not, write to the Free Software
17   *  Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
18   */
19              
20  package com.maverick.crypto.encoders;
21  
22  import java.io.ByteArrayOutputStream  ;
23  import java.io.IOException  ;
24  import java.io.OutputStream  ;
25  
26  public class Base64
27  {
28      private static final byte[] encodingTable =
29          {
30              (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
31              (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
32              (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
33              (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
34              (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
35              (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
36              (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
37              (byte)'v',
38              (byte)'w', (byte)'x', (byte)'y', (byte)'z',
39              (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
40              (byte)'7', (byte)'8', (byte)'9',
41              (byte)'+', (byte)'/'
42          };
43  
44      /**
45       * encode the input data producing a base 64 encoded byte array.
46       *
47       * @return a byte array containing the base 64 encoded data.
48       */
49      public static byte[] encode(
50          byte[]  data)
51      {
52          byte[]  bytes;
53  
54          int modulus = data.length % 3;
55          if (modulus == 0)
56          {
57              bytes = new byte[4 * data.length / 3];
58          }
59          else
60          {
61              bytes = new byte[4 * ((data.length / 3) + 1)];
62          }
63  
64          int dataLength = (data.length - modulus);
65          int a1, a2, a3;
66          for (int i = 0, j = 0; i < dataLength; i += 3, j += 4)
67          {
68              a1 = data[i] & 0xff;
69              a2 = data[i + 1] & 0xff;
70              a3 = data[i + 2] & 0xff;
71  
72              bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
73              bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
74              bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
75              bytes[j + 3] = encodingTable[a3 & 0x3f];
76          }
77  
78          /*
79           * process the tail end.
80           */
81          int b1, b2, b3;
82          int d1, d2;
83  
84          switch (modulus)
85          {
86          case 0:     /* nothing left to do */
87              break;
88          case 1:
89              d1 = data[data.length - 1] & 0xff;
90              b1 = (d1 >>> 2) & 0x3f;
91              b2 = (d1 << 4) & 0x3f;
92  
93              bytes[bytes.length - 4] = encodingTable[b1];
94              bytes[bytes.length - 3] = encodingTable[b2];
95              bytes[bytes.length - 2] = (byte)'=';
96              bytes[bytes.length - 1] = (byte)'=';
97              break;
98          case 2:
99              d1 = data[data.length - 2] & 0xff;
100             d2 = data[data.length - 1] & 0xff;
101 
102             b1 = (d1 >>> 2) & 0x3f;
103             b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
104             b3 = (d2 << 2) & 0x3f;
105 
106             bytes[bytes.length - 4] = encodingTable[b1];
107             bytes[bytes.length - 3] = encodingTable[b2];
108             bytes[bytes.length - 2] = encodingTable[b3];
109             bytes[bytes.length - 1] = (byte)'=';
110             break;
111         }
112 
113         return bytes;
114     }
115 
116     /*
117      * set up the decoding table.
118      */
119     private static final byte[] decodingTable;
120 
121     static
122     {
123         decodingTable = new byte[128];
124 
125         for (int i = 'A'; i <= 'Z'; i++)
126         {
127             decodingTable[i] = (byte)(i - 'A');
128         }
129 
130         for (int i = 'a'; i <= 'z'; i++)
131         {
132             decodingTable[i] = (byte)(i - 'a' + 26);
133         }
134 
135         for (int i = '0'; i <= '9'; i++)
136         {
137             decodingTable[i] = (byte)(i - '0' + 52);
138         }
139 
140         decodingTable['+'] = 62;
141         decodingTable['/'] = 63;
142     }
143 
144     /**
145      * decode the base 64 encoded input data. It is assumed the input data is valid.
146      *
147      * @return a byte array representing the decoded data.
148      */
149     public static byte[] decode(
150         byte[]  data)
151     {
152         byte[]  bytes;
153         byte    b1, b2, b3, b4;
154 
155         if (data[data.length - 2] == '=')
156         {
157             bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
158         }
159         else if (data[data.length - 1] == '=')
160         {
161             bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
162         }
163         else
164         {
165             bytes = new byte[((data.length / 4) * 3)];
166         }
167 
168         for (int i = 0, j = 0; i < data.length - 4; i += 4, j += 3)
169         {
170             b1 = decodingTable[data[i]];
171             b2 = decodingTable[data[i + 1]];
172             b3 = decodingTable[data[i + 2]];
173             b4 = decodingTable[data[i + 3]];
174 
175             bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
176             bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
177             bytes[j + 2] = (byte)((b3 << 6) | b4);
178         }
179 
180         if (data[data.length - 2] == '=')
181         {
182             b1 = decodingTable[data[data.length - 4]];
183             b2 = decodingTable[data[data.length - 3]];
184 
185             bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
186         }
187         else if (data[data.length - 1] == '=')
188         {
189             b1 = decodingTable[data[data.length - 4]];
190             b2 = decodingTable[data[data.length - 3]];
191             b3 = decodingTable[data[data.length - 2]];
192 
193             bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
194             bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
195         }
196         else
197         {
198             b1 = decodingTable[data[data.length - 4]];
199             b2 = decodingTable[data[data.length - 3]];
200             b3 = decodingTable[data[data.length - 2]];
201             b4 = decodingTable[data[data.length - 1]];
202 
203             bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
204             bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
205             bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
206         }
207 
208         return bytes;
209     }
210 
211     private static boolean ignore(
212         char    c)
213     {
214         return (c == '\n' || c =='\r' || c == '\t' || c == ' ');
215     }
216 
217     /**
218      * decode the base 64 encoded String data - whitespace will be ignored.
219      *
220      * @return a byte array representing the decoded data.
221      */
222     public static byte[] decode(
223         String    data)
224     {
225         ByteArrayOutputStream     bOut = new ByteArrayOutputStream  ();
226 
227         try
228         {
229             decode(data, bOut);
230         }
231         catch (IOException   e)
232         {
233             throw new RuntimeException  ("exception decoding base64 string: " + e);
234         }
235 
236         return bOut.toByteArray();
237     }
238 
239     /**
240      * decode the base 64 encoded String data writing it to the given output stream,
241      * whitespace characters will be ignored.
242      *
243      * @return the number of bytes produced.
244      */
245     public static int decode(
246         String                data,
247         OutputStream      out)
248         throws IOException  
249     {
250         byte[]  bytes;
251         byte    b1, b2, b3, b4;
252         int     length = 0;
253 
254         int     end = data.length();
255 
256         while (end > 0)
257         {
258             if (!ignore(data.charAt(end - 1)))
259             {
260                 break;
261             }
262 
263             end--;
264         }
265 
266         for (int i = 0; i < end - 4; i += 4)
267         {
268             if (ignore(data.charAt(i)))
269             {
270                 continue;
271             }
272 
273             b1 = decodingTable[data.charAt(i)];
274             b2 = decodingTable[data.charAt(i + 1)];
275             b3 = decodingTable[data.charAt(i + 2)];
276             b4 = decodingTable[data.charAt(i + 3)];
277 
278             out.write((b1 << 2) | (b2 >> 4));
279             out.write((b2 << 4) | (b3 >> 2));
280             out.write((b3 << 6) | b4);
281 
282             length += 3;
283         }
284 
285         if (data.charAt(end - 2) == '=')
286         {
287             b1 = decodingTable[data.charAt(end - 4)];
288             b2 = decodingTable[data.charAt(end - 3)];
289 
290             out.write((b1 << 2) | (b2 >> 4));
291 
292             length += 1;
293         }
294         else if (data.charAt(end - 1) == '=')
295         {
296             b1 = decodingTable[data.charAt(end - 4)];
297             b2 = decodingTable[data.charAt(end - 3)];
298             b3 = decodingTable[data.charAt(end - 2)];
299 
300             out.write((b1 << 2) | (b2 >> 4));
301             out.write((b2 << 4) | (b3 >> 2));
302 
303             length += 2;
304         }
305         else
306         {
307             b1 = decodingTable[data.charAt(end - 4)];
308             b2 = decodingTable[data.charAt(end - 3)];
309             b3 = decodingTable[data.charAt(end - 2)];
310             b4 = decodingTable[data.charAt(end - 1)];
311 
312             out.write((b1 << 2) | (b2 >> 4));
313             out.write((b2 << 4) | (b3 >> 2));
314             out.write((b3 << 6) | b4);
315 
316             length += 3;
317         }
318 
319         return length;
320     }
321 }
322
A to Z: JavaDoc & Examples Daily Java News & Articles Open Source Projects Open Source Codes Free Computer Books Remove Frame
Popular Tags