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 }