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 THREAD_POOL_DELAY_SECONDS = 10;
53
54 static final int MAX_BLOCK_LENGTH = MAX_BLOCK_SIZE * BASE_BLOCK_SIZE;
55
56 /**
57 * Maximum possible Huffman alphabet size.
58 */
59 static final int HUFFMAN_MAX_ALPHABET_SIZE = 258;
60
61 /**
62 * The longest Huffman code length created by the encoder.
63 */
64 static final int HUFFMAN_ENCODE_MAX_CODE_LENGTH = 20;
65
66 /**
67 * The longest Huffman code length accepted by the decoder.
68 */
69 static final int HUFFMAN_DECODE_MAX_CODE_LENGTH = 23;
70
71 /**
72 * Huffman symbols used for run-length encoding.
73 */
74 static final int HUFFMAN_SYMBOL_RUNA = 0;
75 static final int HUFFMAN_SYMBOL_RUNB = 1;
76
77 /**
78 * Huffman symbols range size for Huffman used map.
79 */
80 static final int HUFFMAN_SYMBOL_RANGE_SIZE = 16;
81
82 /**
83 * Maximum length of zero-terminated bit runs of MTF'ed Huffman table.
84 */
85 static final int HUFFMAN_SELECTOR_LIST_MAX_LENGTH = 6;
86
87 /**
88 * Number of symbols decoded after which a new Huffman table is selected.
89 */
90 static final int HUFFMAN_GROUP_RUN_LENGTH = 50;
91
92 /**
93 * Maximum possible number of Huffman table selectors.
94 */
95 static final int MAX_SELECTORS = 2 + 900000 / HUFFMAN_GROUP_RUN_LENGTH; // 18002
96
97 /**
98 * Minimum number of alternative Huffman tables.
99 */
100 static final int HUFFMAN_MINIMUM_TABLES = 2;
101
102 /**
103 * Maximum number of alternative Huffman tables.
104 */
105 static final int HUFFMAN_MAXIMUM_TABLES = 6;
106
107 private Bzip2Constants() { }
108 }