1 /*
2 * Copyright (c) 1995, 2000, 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 */
25 package es.accv.arangi.base.util.base64;
26
27 import java.io.OutputStream;
28 import java.io.PushbackInputStream;
29 import java.io.PrintStream;
30
31 /**
32 * This class implements a BASE64 Character decoder as specified in RFC1521.
33 *
34 * This RFC is part of the MIME specification which is published by the
35 * Internet Engineering Task Force (IETF). Unlike some other encoding
36 * schemes there is nothing in this encoding that tells the decoder
37 * where a buffer starts or stops, so to use it you will need to isolate
38 * your encoded data into a single chunk and then feed them this decoder.
39 * The simplest way to do that is to read all of the encoded data into a
40 * string and then use:
41 * <pre>
42 * byte mydata[];
43 * BASE64Decoder base64 = new BASE64Decoder();
44 *
45 * mydata = base64.decodeBuffer(bufferString);
46 * </pre>
47 * This will decode the String in <i>bufferString</i> and give you an array
48 * of bytes in the array <i>myData</i>.
49 *
50 * On errors, this class throws a CEFormatException with the following detail
51 * strings:
52 * <pre>
53 * "BASE64Decoder: Not enough bytes for an atom."
54 * </pre>
55 *
56 * @author Chuck McManis
57 * @see CharacterEncoder
58 * @see BASE64Decoder
59 */
60
61 public class BASE64Decoder extends CharacterDecoder {
62
63 /** This class has 4 bytes per atom */
64 protected int bytesPerAtom() {
65 return (4);
66 }
67
68 /** Any multiple of 4 will do, 72 might be common */
69 protected int bytesPerLine() {
70 return (72);
71 }
72
73 /**
74 * This character array provides the character to value map
75 * based on RFC1521.
76 */
77 private final static char pem_array[] = {
78 // 0 1 2 3 4 5 6 7
79 'A','B','C','D','E','F','G','H', // 0
80 'I','J','K','L','M','N','O','P', // 1
81 'Q','R','S','T','U','V','W','X', // 2
82 'Y','Z','a','b','c','d','e','f', // 3
83 'g','h','i','j','k','l','m','n', // 4
84 'o','p','q','r','s','t','u','v', // 5
85 'w','x','y','z','0','1','2','3', // 6
86 '4','5','6','7','8','9','+','/' // 7
87 };
88
89 private final static byte pem_convert_array[] = new byte[256];
90
91 static {
92 for (int i = 0; i < 255; i++) {
93 pem_convert_array[i] = -1;
94 }
95 for (int i = 0; i < pem_array.length; i++) {
96 pem_convert_array[pem_array[i]] = (byte) i;
97 }
98 }
99
100 byte decode_buffer[] = new byte[4];
101
102 /**
103 * Decode one BASE64 atom into 1, 2, or 3 bytes of data.
104 */
105 protected void decodeAtom(PushbackInputStream inStream, OutputStream outStream, int rem)
106 throws java.io.IOException
107 {
108 int i;
109 byte a = -1, b = -1, c = -1, d = -1;
110
111 if (rem < 2) {
112 throw new CEFormatException("BASE64Decoder: Not enough bytes for an atom.");
113 }
114 do {
115 i = inStream.read();
116 if (i == -1) {
117 throw new CEStreamExhausted();
118 }
119 } while (i == '\n' || i == '\r');
120 decode_buffer[0] = (byte) i;
121
122 i = readFully(inStream, decode_buffer, 1, rem-1);
123 if (i == -1) {
124 throw new CEStreamExhausted();
125 }
126
127 if (rem > 3 && decode_buffer[3] == '=') {
128 rem = 3;
129 }
130 if (rem > 2 && decode_buffer[2] == '=') {
131 rem = 2;
132 }
133 switch (rem) {
134 case 4:
135 d = pem_convert_array[decode_buffer[3] & 0xff];
136 // NOBREAK
137 case 3:
138 c = pem_convert_array[decode_buffer[2] & 0xff];
139 // NOBREAK
140 case 2:
141 b = pem_convert_array[decode_buffer[1] & 0xff];
142 a = pem_convert_array[decode_buffer[0] & 0xff];
143 break;
144 }
145
146 switch (rem) {
147 case 2:
148 outStream.write( (byte)(((a << 2) & 0xfc) | ((b >>> 4) & 3)) );
149 break;
150 case 3:
151 outStream.write( (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3)) );
152 outStream.write( (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf)) );
153 break;
154 case 4:
155 outStream.write( (byte) (((a << 2) & 0xfc) | ((b >>> 4) & 3)) );
156 outStream.write( (byte) (((b << 4) & 0xf0) | ((c >>> 2) & 0xf)) );
157 outStream.write( (byte) (((c << 6) & 0xc0) | (d & 0x3f)) );
158 break;
159 }
160 return;
161 }
162 }