1/*
2 * Copyright (c) 1995, 1997, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.  Oracle designates this
8 * particular file as subject to the "Classpath" exception as provided
9 * by Oracle in the LICENSE file that accompanied this code.
10 *
11 * This code is distributed in the hope that it will be useful, but WITHOUT
12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
13 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
14 * version 2 for more details (a copy is included in the LICENSE file that
15 * accompanied this code).
16 *
17 * You should have received a copy of the GNU General Public License version
18 * 2 along with this work; if not, write to the Free Software Foundation,
19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
22 * or visit www.oracle.com if you need additional information or have any
23 * questions.
24 */
25package sun.misc;
26
27import java.io.OutputStream;
28import java.io.InputStream;
29import java.io.PrintStream;
30import java.io.IOException;
31
32/**
33 * This class implements a BASE64 Character encoder as specified in RFC1521.
34 * This RFC is part of the MIME specification as published by the Internet
35 * Engineering Task Force (IETF). Unlike some other encoding schemes there
36 * is nothing in this encoding that indicates
37 * where a buffer starts or ends.
38 *
39 * This means that the encoded text will simply start with the first line
40 * of encoded text and end with the last line of encoded text.
41 *
42 * @author      Chuck McManis
43 * @see         CharacterEncoder
44 * @see         BASE64Decoder
45 */
46
47public class BASE64Encoder extends CharacterEncoder {
48
49    /** this class encodes three bytes per atom. */
50    protected int bytesPerAtom() {
51        return (3);
52    }
53
54    /**
55     * this class encodes 57 bytes per line. This results in a maximum
56     * of 57/3 * 4 or 76 characters per output line. Not counting the
57     * line termination.
58     */
59    protected int bytesPerLine() {
60        return (57);
61    }
62
63    /** This array maps the characters to their 6 bit values */
64    private final static char pem_array[] = {
65        //       0   1   2   3   4   5   6   7
66                'A','B','C','D','E','F','G','H', // 0
67                'I','J','K','L','M','N','O','P', // 1
68                'Q','R','S','T','U','V','W','X', // 2
69                'Y','Z','a','b','c','d','e','f', // 3
70                'g','h','i','j','k','l','m','n', // 4
71                'o','p','q','r','s','t','u','v', // 5
72                'w','x','y','z','0','1','2','3', // 6
73                '4','5','6','7','8','9','+','/'  // 7
74        };
75
76    /**
77     * encodeAtom - Take three bytes of input and encode it as 4
78     * printable characters. Note that if the length in len is less
79     * than three is encodes either one or two '=' signs to indicate
80     * padding characters.
81     */
82    protected void encodeAtom(OutputStream outStream, byte data[], int offset, int len)
83        throws IOException {
84        byte a, b, c;
85
86        if (len == 1) {
87            a = data[offset];
88            b = 0;
89            c = 0;
90            outStream.write(pem_array[(a >>> 2) & 0x3F]);
91            outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
92            outStream.write('=');
93            outStream.write('=');
94        } else if (len == 2) {
95            a = data[offset];
96            b = data[offset+1];
97            c = 0;
98            outStream.write(pem_array[(a >>> 2) & 0x3F]);
99            outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
100            outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
101            outStream.write('=');
102        } else {
103            a = data[offset];
104            b = data[offset+1];
105            c = data[offset+2];
106            outStream.write(pem_array[(a >>> 2) & 0x3F]);
107            outStream.write(pem_array[((a << 4) & 0x30) + ((b >>> 4) & 0xf)]);
108            outStream.write(pem_array[((b << 2) & 0x3c) + ((c >>> 6) & 0x3)]);
109            outStream.write(pem_array[c & 0x3F]);
110        }
111    }
112}
113