Classes in this File | Line Coverage | Branch Coverage | Complexity | ||||
Base64Decoder |
|
| 7.0;7 |
1 | /* | |
2 | * Licensed to the Apache Software Foundation (ASF) under one or more | |
3 | * contributor license agreements. See the NOTICE file distributed with | |
4 | * this work for additional information regarding copyright ownership. | |
5 | * The ASF licenses this file to You under the Apache License, Version 2.0 | |
6 | * (the "License"); you may not use this file except in compliance with | |
7 | * the License. You may obtain a copy of the License at | |
8 | * | |
9 | * http://www.apache.org/licenses/LICENSE-2.0 | |
10 | * | |
11 | * Unless required by applicable law or agreed to in writing, software | |
12 | * distributed under the License is distributed on an "AS IS" BASIS, | |
13 | * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. | |
14 | * See the License for the specific language governing permissions and | |
15 | * limitations under the License. | |
16 | */ | |
17 | package org.apache.commons.fileupload.util.mime; | |
18 | ||
19 | import java.io.IOException; | |
20 | import java.io.OutputStream; | |
21 | ||
22 | /** | |
23 | * @since 1.3 | |
24 | */ | |
25 | final class Base64Decoder { | |
26 | ||
27 | /** | |
28 | * Decoding table value for invalid bytes. | |
29 | */ | |
30 | private static final int INVALID_BYTE = -1; // must be outside range 0-63 | |
31 | ||
32 | /** | |
33 | * Decoding table value for padding bytes, so can detect PAD afer conversion. | |
34 | */ | |
35 | private static final int PAD_BYTE = -2; // must be outside range 0-63 | |
36 | ||
37 | /** | |
38 | * Mask to treat byte as unsigned integer. | |
39 | */ | |
40 | private static final int MASK_BYTE_UNSIGNED = 0xFF; | |
41 | ||
42 | /** | |
43 | * Number of bytes per encoded chunk - 4 6bit bytes produce 3 8bit bytes on output. | |
44 | */ | |
45 | private static final int INPUT_BYTES_PER_CHUNK = 4; | |
46 | ||
47 | /** | |
48 | * Set up the encoding table. | |
49 | */ | |
50 | 1 | private static final byte[] ENCODING_TABLE = { |
51 | (byte) 'A', (byte) 'B', (byte) 'C', (byte) 'D', (byte) 'E', (byte) 'F', (byte) 'G', | |
52 | (byte) 'H', (byte) 'I', (byte) 'J', (byte) 'K', (byte) 'L', (byte) 'M', (byte) 'N', | |
53 | (byte) 'O', (byte) 'P', (byte) 'Q', (byte) 'R', (byte) 'S', (byte) 'T', (byte) 'U', | |
54 | (byte) 'V', (byte) 'W', (byte) 'X', (byte) 'Y', (byte) 'Z', | |
55 | (byte) 'a', (byte) 'b', (byte) 'c', (byte) 'd', (byte) 'e', (byte) 'f', (byte) 'g', | |
56 | (byte) 'h', (byte) 'i', (byte) 'j', (byte) 'k', (byte) 'l', (byte) 'm', (byte) 'n', | |
57 | (byte) 'o', (byte) 'p', (byte) 'q', (byte) 'r', (byte) 's', (byte) 't', (byte) 'u', | |
58 | (byte) 'v', (byte) 'w', (byte) 'x', (byte) 'y', (byte) 'z', | |
59 | (byte) '0', (byte) '1', (byte) '2', (byte) '3', (byte) '4', (byte) '5', (byte) '6', | |
60 | (byte) '7', (byte) '8', (byte) '9', | |
61 | (byte) '+', (byte) '/' | |
62 | }; | |
63 | ||
64 | /** | |
65 | * The padding byte. | |
66 | */ | |
67 | private static final byte PADDING = (byte) '='; | |
68 | ||
69 | /** | |
70 | * Set up the decoding table; this is indexed by a byte converted to an unsigned int, | |
71 | * so must be at least as large as the number of different byte values, | |
72 | * positive and negative and zero. | |
73 | */ | |
74 | 1 | private static final byte[] DECODING_TABLE = new byte[Byte.MAX_VALUE - Byte.MIN_VALUE + 1]; |
75 | ||
76 | static { | |
77 | // Initialise as all invalid characters | |
78 | 257 | for (int i = 0; i < DECODING_TABLE.length; i++) { |
79 | 256 | DECODING_TABLE[i] = INVALID_BYTE; |
80 | } | |
81 | // set up valid characters | |
82 | 65 | for (int i = 0; i < ENCODING_TABLE.length; i++) { |
83 | 64 | DECODING_TABLE[ENCODING_TABLE[i]] = (byte) i; |
84 | } | |
85 | // Allow pad byte to be easily detected after conversion | |
86 | 1 | DECODING_TABLE[PADDING] = PAD_BYTE; |
87 | 1 | } |
88 | ||
89 | /** | |
90 | * Hidden constructor, this class must not be instantiated. | |
91 | */ | |
92 | 0 | private Base64Decoder() { |
93 | // do nothing | |
94 | 0 | } |
95 | ||
96 | /** | |
97 | * Decode the base 64 encoded byte data writing it to the given output stream, | |
98 | * whitespace characters will be ignored. | |
99 | * | |
100 | * @param data the buffer containing the Base64-encoded data | |
101 | * @param out the output stream to hold the decoded bytes | |
102 | * | |
103 | * @return the number of bytes produced. | |
104 | * @throws IOException thrown when the padding is incorrect or the input is truncated. | |
105 | */ | |
106 | public static int decode(byte[] data, OutputStream out) throws IOException { | |
107 | 28 | int outLen = 0; |
108 | 28 | byte [] cache = new byte[INPUT_BYTES_PER_CHUNK]; |
109 | 28 | int cachedBytes = 0; |
110 | ||
111 | 418 | for (byte b : data) { |
112 | 393 | final byte d = DECODING_TABLE[MASK_BYTE_UNSIGNED & b]; |
113 | 393 | if (d == INVALID_BYTE) { |
114 | 14 | continue; // Ignore invalid bytes |
115 | } | |
116 | 379 | cache[cachedBytes++] = d; |
117 | 379 | if (cachedBytes == INPUT_BYTES_PER_CHUNK) { |
118 | // CHECKSTYLE IGNORE MagicNumber FOR NEXT 4 LINES | |
119 | 92 | final byte b1 = cache[0]; |
120 | 92 | final byte b2 = cache[1]; |
121 | 92 | final byte b3 = cache[2]; |
122 | 92 | final byte b4 = cache[3]; |
123 | 92 | if (b1 == PAD_BYTE || b2 == PAD_BYTE) { |
124 | 2 | throw new IOException("Invalid Base64 input: incorrect padding, first two bytes cannot be padding"); |
125 | } | |
126 | // Convert 4 6-bit bytes to 3 8-bit bytes | |
127 | // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE | |
128 | 90 | out.write((b1 << 2) | (b2 >> 4)); // 6 bits of b1 plus 2 bits of b2 |
129 | 90 | outLen++; |
130 | 90 | if (b3 != PAD_BYTE) { |
131 | // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE | |
132 | 82 | out.write((b2 << 4) | (b3 >> 2)); // 4 bits of b2 plus 4 bits of b3 |
133 | 82 | outLen++; |
134 | 82 | if (b4 != PAD_BYTE) { |
135 | // CHECKSTYLE IGNORE MagicNumber FOR NEXT 1 LINE | |
136 | 72 | out.write((b3 << 6) | b4); // 2 bits of b3 plus 6 bits of b4 |
137 | 72 | outLen++; |
138 | } | |
139 | 8 | } else if (b4 != PAD_BYTE) { // if byte 3 is pad, byte 4 must be pad too |
140 | 1 | throw new // line wrap to avoid 120 char limit |
141 | IOException("Invalid Base64 input: incorrect padding, 4th byte must be padding if 3rd byte is"); | |
142 | } | |
143 | 89 | cachedBytes = 0; |
144 | } | |
145 | } | |
146 | // Check for anything left over | |
147 | 25 | if (cachedBytes != 0) { |
148 | 6 | throw new IOException("Invalid Base64 input: truncated"); |
149 | } | |
150 | 19 | return outLen; |
151 | } | |
152 | } |