Base64Encoder


1   /*
2    * Copyright � World Wide Web Consortium, (Massachusetts Institute of Technology, 
3    * Institut National de Recherche en Informatique et en Automatique, Keio University).
4    * All Rights Reserved. http://www.w3.org/Consortium/Legal/
5    */
6   package org.w3c.tools.codec;
7   
8   import java.io.ByteArrayInputStream  ;
9   import java.io.ByteArrayOutputStream  ;
10  import java.io.IOException  ;
11  import java.io.InputStream  ;
12  import java.io.OutputStream  ;
13  import java.io.UnsupportedEncodingException  ;
14  
15  /**
16   * BASE64 encoder implementation.
17   * This object takes as parameter an input stream and an output stream. It
18   * encodes the input stream, using the BASE64 encoding rules, as defined
19   * in <a HREF="http://ds.internic.net/rfc/rfc1521.txt">MIME specification</a>
20   * and emit the resulting data to the output stream.
21   * @see org.w3c.tools.codec.Base64Decoder
22   */
23  public class Base64Encoder
24  {
25      private static final int BUFFER_SIZE = 1024;
26      private static byte encoding[] =
27          {
28              (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', (byte) 'H', // 0-7
29              (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', (byte) 'O', (byte) 'P', // 8-15
30              (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', (byte) 'V', (byte) 'W', (byte) 'X', // 16-23
31              (byte) 'Y', (byte) 'Z', (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', // 24-31
32              (byte) 'g', (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', // 32-39
33              (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', (byte) 'v', // 40-47
34              (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', (byte) '0', (byte) '1', (byte) '2', (byte) '3', // 48-55
35              (byte) '4', (byte) '5', (byte) '6', (byte) '7', (byte) '8', (byte) '9', (byte) '+', (byte) '/', // 56-63
36              (byte) '=' // 64
37      };
38  
39      InputStream   in = null;
40      OutputStream   out = null;
41      boolean stringp = false;
42  
43      private final int get1(byte buf[], int off)
44      {
45          return (buf[off] & 0xfc) >> 2;
46      }
47  
48      private final int get2(byte buf[], int off)
49      {
50          return ((buf[off] & 0x3) << 4) | ((buf[off + 1] & 0xf0) >>> 4);
51      }
52  
53      private final int get3(byte buf[], int off)
54      {
55          return ((buf[off + 1] & 0x0f) << 2) | ((buf[off + 2] & 0xc0) >>> 6);
56      }
57  
58      private static final int get4(byte buf[], int off)
59      {
60          return buf[off + 2] & 0x3f;
61      }
62  
63      /**
64       * Process the data: encode the input stream to the output stream.
65       * This method runs through the input stream, encoding it to the output 
66       * stream.
67       * @exception IOException If we weren't able to access the input stream or
68       *    the output stream.
69       */
70      public void process() throws IOException  
71      {
72          byte buffer[] = new byte[BUFFER_SIZE];
73          int got = -1;
74          int off = 0;
75          int count = 0;
76          while ((got = in.read(buffer, off, BUFFER_SIZE - off)) > 0)
77          {
78              if (got >= 3)
79              {
80                  got += off;
81                  off = 0;
82                  while (off + 3 <= got)
83                  {
84                      int c1 = get1(buffer, off);
85                      int c2 = get2(buffer, off);
86                      int c3 = get3(buffer, off);
87                      int c4 = get4(buffer, off);
88                      switch (count)
89                      {
90                          case 73 :
91                              out.write(encoding[c1]);
92                              out.write(encoding[c2]);
93                              out.write(encoding[c3]);
94                              out.write('\n');
95                              out.write(encoding[c4]);
96                              count = 1;
97                              break;
98                          case 74 :
99                              out.write(encoding[c1]);
100                             out.write(encoding[c2]);
101                             out.write('\n');
102                             out.write(encoding[c3]);
103                             out.write(encoding[c4]);
104                             count = 2;
105                             break;
106                         case 75 :
107                             out.write(encoding[c1]);
108                             out.write('\n');
109                             out.write(encoding[c2]);
110                             out.write(encoding[c3]);
111                             out.write(encoding[c4]);
112                             count = 3;
113                             break;
114                         case 76 :
115                             out.write('\n');
116                             out.write(encoding[c1]);
117                             out.write(encoding[c2]);
118                             out.write(encoding[c3]);
119                             out.write(encoding[c4]);
120                             count = 4;
121                             break;
122                         default :
123                             out.write(encoding[c1]);
124                             out.write(encoding[c2]);
125                             out.write(encoding[c3]);
126                             out.write(encoding[c4]);
127                             count += 4;
128                             break;
129                     }
130                     off += 3;
131                 }
132                 // Copy remaining bytes to beginning of buffer:
133                 for (int i = 0; i < 3; i++)
134                     buffer[i] = (i < got - off) ? buffer[off + i] : ((byte) 0);
135                 off = got - off;
136             }
137             else
138             {
139                 // Total read amount is less then 3 bytes:
140                 off += got;
141             }
142         }
143         // Manage the last bytes, from 0 to off:
144         switch (off)
145         {
146             case 1 :
147                 out.write(encoding[get1(buffer, 0)]);
148                 out.write(encoding[get2(buffer, 0)]);
149                 out.write('=');
150                 out.write('=');
151                 break;
152             case 2 :
153                 out.write(encoding[get1(buffer, 0)]);
154                 out.write(encoding[get2(buffer, 0)]);
155                 out.write(encoding[get3(buffer, 0)]);
156                 out.write('=');
157         }
158         return;
159     }
160 
161     /**
162      * Encode the content of this encoder, as a string.
163      * This methods encode the String content, that was provided at creation 
164      * time, following the BASE64 rules, as specified in the rfc1521.
165      * @return A String, reprenting the encoded content of the input String.
166      */
167     public String   processString()
168     {
169         if (!stringp)
170             throw new RuntimeException  (
171                 this.getClass().getName()
172                     + "[processString]"
173                     + "invalid call (not a String)");
174         try
175         {
176             process();
177         }
178         catch (IOException   e)
179         {
180         }
181         return ((ByteArrayOutputStream  ) out).toString();
182     }
183 
184     /**
185      * Create a new Base64 encoder, to encode the given string.
186      * @param input The String to be encoded.
187      */
188     public Base64Encoder(String   input)
189     {
190         byte bytes[];
191         try
192         {
193             bytes = input.getBytes("ISO-8859-1");
194         }
195         catch (UnsupportedEncodingException   ex)
196         {
197             throw new RuntimeException  (
198                 this.getClass().getName()
199                     + "[Constructor] Unable to convert"
200                     + "properly char to bytes");
201         }
202         this.stringp = true;
203         this.in = new ByteArrayInputStream  (bytes);
204         this.out = new ByteArrayOutputStream  ();
205     }
206 
207     /**
208      * Create a new Base64 encoder, encoding input to output.
209      * @param in The input stream to be encoded.
210      * @param out The output stream, to write encoded data to.
211      */
212     public Base64Encoder(InputStream   in, OutputStream   out)
213     {
214         this.in = in;
215         this.out = out;
216         this.stringp = false;
217     }
218 
219     /**
220      * Testing the encoder.
221      * Run with one argument, prints the encoded version of it.
222      */
223     public static void main(String   args[])
224     {
225         if (args.length != 1)
226         {
227             System.out.println("Base64Encoder <string>");
228             System.exit(0);
229         }
230         Base64Encoder b = new Base64Encoder(args[0]);
231         System.out.println("[" + b.processString() + "]");
232         // joe:eoj -> am9lOmVvag==
233         // 12345678:87654321 -> MTIzNDU2Nzg6ODc2NTQzMjE=
234     }
235 }
236
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