1 /*
2 * Copyright 2014 The Netty Project
3 *
4 * The Netty Project licenses this file to you under the Apache License,
5 * version 2.0 (the "License"); you may not use this file except in compliance
6 * with the License. You may obtain a copy of the License at:
7 *
8 * https://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
12 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
13 * License for the specific language governing permissions and limitations
14 * under the License.
15 */
16 package io.netty.handler.codec.compression;
17
18 /**
19 * Constants for both the {@link Bzip2Encoder} and the {@link Bzip2Decoder}.
20 */
21 final class Bzip2Constants {
22
23 /**
24 * Magic number of Bzip2 stream.
25 */
26 static final int MAGIC_NUMBER = 'B' << 16 | 'Z' << 8 | 'h';
27
28 /**
29 * Block header magic number. Equals to BCD (pi).
30 */
31 static final int BLOCK_HEADER_MAGIC_1 = 0x314159;
32 static final int BLOCK_HEADER_MAGIC_2 = 0x265359;
33
34 /**
35 * End of stream magic number. Equals to BCD sqrt(pi).
36 */
37 static final int END_OF_STREAM_MAGIC_1 = 0x177245;
38 static final int END_OF_STREAM_MAGIC_2 = 0x385090;
39
40 /**
41 * Base block size.
42 */
43 static final int BASE_BLOCK_SIZE = 100000;
44
45 /**
46 * Minimum and maximum size of one block.
47 * Must be multiplied by {@link Bzip2Constants#BASE_BLOCK_SIZE}.
48 */
49 static final int MIN_BLOCK_SIZE = 1;
50 static final int MAX_BLOCK_SIZE = 9;
51
52 static final int MAX_BLOCK_LENGTH = MAX_BLOCK_SIZE * BASE_BLOCK_SIZE;
53
54 /**
55 * Maximum possible Huffman alphabet size.
56 */
57 static final int HUFFMAN_MAX_ALPHABET_SIZE = 258;
58
59 /**
60 * The longest Huffman code length created by the encoder.
61 */
62 static final int HUFFMAN_ENCODE_MAX_CODE_LENGTH = 20;
63
64 /**
65 * The longest Huffman code length accepted by the decoder.
66 */
67 static final int HUFFMAN_DECODE_MAX_CODE_LENGTH = 23;
68
69 /**
70 * Huffman symbols used for run-length encoding.
71 */
72 static final int HUFFMAN_SYMBOL_RUNA = 0;
73 static final int HUFFMAN_SYMBOL_RUNB = 1;
74
75 /**
76 * Huffman symbols range size for Huffman used map.
77 */
78 static final int HUFFMAN_SYMBOL_RANGE_SIZE = 16;
79
80 /**
81 * Maximum length of zero-terminated bit runs of MTF'ed Huffman table.
82 */
83 static final int HUFFMAN_SELECTOR_LIST_MAX_LENGTH = 6;
84
85 /**
86 * Number of symbols decoded after which a new Huffman table is selected.
87 */
88 static final int HUFFMAN_GROUP_RUN_LENGTH = 50;
89
90 /**
91 * Maximum possible number of Huffman table selectors.
92 */
93 static final int MAX_SELECTORS = 2 + 900000 / HUFFMAN_GROUP_RUN_LENGTH; // 18002
94
95 /**
96 * Minimum number of alternative Huffman tables.
97 */
98 static final int HUFFMAN_MINIMUM_TABLES = 2;
99
100 /**
101 * Maximum number of alternative Huffman tables.
102 */
103 static final int HUFFMAN_MAXIMUM_TABLES = 6;
104
105 private Bzip2Constants() { }
106 }
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