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 final class Lz4Constants {
19 /**
20 * Magic number of LZ4 block.
21 */
22 static final long MAGIC_NUMBER = (long) 'L' << 56 |
23 (long) 'Z' << 48 |
24 (long) '4' << 40 |
25 (long) 'B' << 32 |
26 'l' << 24 |
27 'o' << 16 |
28 'c' << 8 |
29 'k';
30
31 /**
32 * Full length of LZ4 block header.
33 */
34 static final int HEADER_LENGTH = 8 + // magic number
35 1 + // token
36 4 + // compressed length
37 4 + // decompressed length
38 4; // checksum
39
40 /**
41 * Offsets of header's parts.
42 */
43 static final int TOKEN_OFFSET = 8;
44
45 static final int COMPRESSED_LENGTH_OFFSET = TOKEN_OFFSET + 1;
46 static final int DECOMPRESSED_LENGTH_OFFSET = COMPRESSED_LENGTH_OFFSET + 4;
47 static final int CHECKSUM_OFFSET = DECOMPRESSED_LENGTH_OFFSET + 4;
48
49 /**
50 * Base value for compression level.
51 */
52 static final int COMPRESSION_LEVEL_BASE = 10;
53
54 /**
55 * LZ4 block sizes.
56 */
57 static final int MIN_BLOCK_SIZE = 64;
58 static final int MAX_BLOCK_SIZE = 1 << COMPRESSION_LEVEL_BASE + 0x0F; // 32 M
59 static final int DEFAULT_BLOCK_SIZE = 1 << 16; // 64 KB
60
61 /**
62 * LZ4 block types.
63 */
64 static final int BLOCK_TYPE_NON_COMPRESSED = 0x10;
65 static final int BLOCK_TYPE_COMPRESSED = 0x20;
66
67 /**
68 * Default seed value for xxhash.
69 */
70 static final int DEFAULT_SEED = 0x9747b28c;
71
72 private Lz4Constants() { }
73 }