Base64InputStream.java revision 96c5af40d639d629267794f4f0338a267ff94ce5 
1/****************************************************************
2 * Licensed to the Apache Software Foundation (ASF) under one   *
3 * or more contributor license agreements.  See the NOTICE file *
4 * distributed with this work for additional information        *
5 * regarding copyright ownership.  The ASF licenses this file   *
6 * to you under the Apache License, Version 2.0 (the            *
7 * "License"); you may not use this file except in compliance   *
8 * with the License.  You may obtain a copy of the License at   *
9 *                                                              *
10 *   http://www.apache.org/licenses/LICENSE-2.0                 *
11 *                                                              *
12 * Unless required by applicable law or agreed to in writing,   *
13 * software distributed under the License is distributed on an  *
14 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY       *
15 * KIND, either express or implied.  See the License for the    *
16 * specific language governing permissions and limitations      *
17 * under the License.                                           *
18 ****************************************************************/
19
20package org.apache.james.mime4j.decoder;
21
22import java.io.IOException;
23import java.io.InputStream;
24
25import org.apache.commons.logging.Log;
26import org.apache.commons.logging.LogFactory;
27
28/**
29 * Performs Base-64 decoding on an underlying stream.
30 *
31 *
32 * @version $Id: Base64InputStream.java,v 1.3 2004/11/29 13:15:47 ntherning Exp $
33 */
34public class Base64InputStream extends InputStream {
35    private static Log log = LogFactory.getLog(Base64InputStream.class);
36
37    private final InputStream s;
38    private final ByteQueue byteq = new ByteQueue(3);
39    private boolean done = false;
40
41    public Base64InputStream(InputStream s) {
42        this.s = s;
43    }
44
45    /**
46     * Closes the underlying stream.
47     *
48     * @throws IOException on I/O errors.
49     */
50    public void close() throws IOException {
51        s.close();
52    }
53
54    public int read() throws IOException {
55        if (byteq.count() == 0) {
56            fillBuffer();
57            if (byteq.count() == 0) {
58                return -1;
59            }
60        }
61
62        byte val = byteq.dequeue();
63        if (val >= 0)
64            return val;
65        else
66            return val & 0xFF;
67    }
68
69    /**
70     * Retrieve data from the underlying stream, decode it,
71     * and put the results in the byteq.
72     * @throws IOException
73     */
74    private void fillBuffer() throws IOException {
75        byte[] data = new byte[4];
76        int pos = 0;
77
78        int i;
79        while (!done) {
80            switch (i = s.read()) {
81                case -1:
82                    if (pos > 0) {
83                        log.warn("Unexpected EOF in MIME parser, dropping "
84                                + pos + " sextets");
85                    }
86                    return;
87                case '=':
88                    decodeAndEnqueue(data, pos);
89                    done = true;
90                    break;
91                default:
92                    byte sX = TRANSLATION[i];
93                    if (sX < 0)
94                        continue;
95                    data[pos++] = sX;
96                    if (pos == data.length) {
97                        decodeAndEnqueue(data, pos);
98                        return;
99                    }
100                    break;
101            }
102        }
103    }
104
105    private void decodeAndEnqueue(byte[] data, int len) {
106        int accum = 0;
107        accum |= data[0] << 18;
108        accum |= data[1] << 12;
109        accum |= data[2] << 6;
110        accum |= data[3];
111
112        byte b1 = (byte)(accum >>> 16);
113        byteq.enqueue(b1);
114
115        if (len > 2) {
116            byte b2 = (byte)((accum >>> 8) & 0xFF);
117            byteq.enqueue(b2);
118
119            if (len > 3) {
120                byte b3 = (byte)(accum & 0xFF);
121                byteq.enqueue(b3);
122            }
123        }
124    }
125
126    private static byte[] TRANSLATION = {
127        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x00 */
128        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x10 */
129        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, /* 0x20 */
130        52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, /* 0x30 */
131        -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 0x40 */
132        15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, /* 0x50 */
133        -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, /* 0x60 */
134        41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1, /* 0x70 */
135        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x80 */
136        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0x90 */
137        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xA0 */
138        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xB0 */
139        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xC0 */
140        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xD0 */
141        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0xE0 */
142        -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1     /* 0xF0 */
143    };
144
145
146}
147