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Java > Open Source Codes > gnu > mail > util > Base64OutputStream


1 /*
2  * Base64OuputStream.java
3  * Copyright (C) 2002 The Free Software Foundation
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation; either
8  * version 2 of the License, or (at your option) any later version.
9  *
10  * This library 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 GNU
13  * Lesser General Public License for more details.
14  *
15  * You should have received a copy of the GNU Lesser General Public
16  * License along with this library; if not, write to the Free Software
17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
18  */
19
20 package gnu.mail.util;
21
22 import java.io.*;
23
24 /**
25  * A Base64 content transfer encoding filter stream.
26  * <p>
27  * From RFC 2045, section 6.8:
28  * <p>
29  * The Base64 Content-Transfer-Encoding is designed to represent
30  * arbitrary sequences of octets in a form that need not be humanly
31  * readable. The encoding and decoding algorithms are simple, but the
32  * encoded data are consistently only about 33 percent larger than the
33  * unencoded data.
34  *
35  * @author <a HREF="mailto:dog@gnu.org">Chris Burdess</a>
36  */
37 public class Base64OutputStream
38   extends FilterOutputStream
39 {
40
41   private byte buffer[];
42   private int buflen;
43   private int count;
44   private int lineLength;
45   
46   private static final char src[] =
47   {
48     'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',
49     'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',
50     'U', 'V', 'W', 'X', 'Y', 'Z', 'a', 'b', 'c', 'd',
51     'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',
52     'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x',
53     'y', 'z', '0', '1', '2', '3', '4', '5', '6', '7',
54     '8', '9', '+', '/'
55   };
56   
57   private static final int LF = 10, CR = 13, EQ = 61;
58   
59   /**
60    * Default constructor.
61    * This constructs a Base64OutputStream with a line length of 76.
62    */
63   public Base64OutputStream(OutputStream out)
64   {
65     this(out, 76);
66   }
67   
68   /**
69    * Constructor.
70    * @param out the underlying output stream to encode
71    * @param lineLength the line length
72    */
73   public Base64OutputStream(OutputStream out, int lineLength)
74   {
75     super(out);
76     buffer = new byte[3];
77     this.lineLength = lineLength;
78   }
79
80   /**
81    * Writes the specified byte to this output stream.
82    */
83   public void write(int c)
84     throws IOException
85   {
86     buffer[buflen++] = (byte)c;
87     if (buflen==3) {
88       encode();
89       buflen = 0;
90     }
91   }
92   
93   /**
94    * Writes <code>b.length</code> bytes from the specified byte array
95    * to this output stream.
96    */
97   public void write(byte b[])
98     throws IOException
99   {
100     write(b, 0, b.length);
101   }
102   
103   /**
104    * Writes <code>len</code> bytes from the specified byte array
105    * starting at offset <code>off</code> to this output stream.
106    */
107   public void write(byte b[], int off, int len)
108     throws IOException
109   {
110     for (int i=0; i<len; i++)
111       write(b[off+i]);
112   }
113   
114   /**
115    * Flushes this output stream and forces any buffered output bytes to be
116    * written out.
117    */
118   public void flush()
119     throws IOException
120   {
121     if (buflen>0) {
122       encode();
123       buflen = 0;
124     }
125     out.flush();
126   }
127   
128   /**
129    * Closes this output stream and releases any system resources
130    * associated with this stream.
131    */
132   public void close()
133     throws IOException
134   {
135     flush();
136     out.close();
137   }
138   
139   private void encode()
140     throws IOException
141   {
142     if ((count+4)>lineLength)
143     {
144       out.write(CR);
145       out.write(LF);
146       count = 0;
147     }
148     if (buflen==1)
149     {
150       byte b = buffer[0];
151       int i = 0;
152       boolean flag = false;
153       out.write(src[b>>>2 & 0x3f]);
154       out.write(src[(b<<4 & 0x30) + (i>>>4 & 0xf)]);
155       out.write(EQ);
156       out.write(EQ);
157     }
158     else if (buflen==2)
159     {
160       byte b1 = buffer[0], b2 = buffer[1];
161       int i = 0;
162       out.write(src[b1>>>2 & 0x3f]);
163       out.write(src[(b1<<4 & 0x30) + (b2>>>4 & 0xf)]);
164       out.write(src[(b2<<2 & 0x3c) + (i>>>6 & 0x3)]);
165       out.write(EQ);
166     }
167     else
168     {
169       byte b1 = buffer[0], b2 = buffer[1], b3 = buffer[2];
170       out.write(src[b1>>>2 & 0x3f]);
171       out.write(src[(b1<<4 & 0x30) + (b2>>>4 & 0xf)]);
172       out.write(src[(b2<<2 & 0x3c) + (b3>>>6 & 0x3)]);
173       out.write(src[b3 & 0x3f]);
174     }
175     count += 4;
176   }
177
178 }
179
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