1 | /* Copyright 2016 Google Inc. All Rights Reserved. |
2 | |
3 | Distributed under MIT license. |
4 | See file LICENSE for detail or copy at https://opensource.org/licenses/MIT |
5 | */ |
6 | |
7 | #ifndef BROTLI_COMMON_CONSTANTS_H_ |
8 | #define BROTLI_COMMON_CONSTANTS_H_ |
9 | |
10 | /* Specification: 7.3. Encoding of the context map */ |
11 | #define BROTLI_CONTEXT_MAP_MAX_RLE 16 |
12 | |
13 | /* Specification: 2. Compressed representation overview */ |
14 | #define BROTLI_MAX_NUMBER_OF_BLOCK_TYPES 256 |
15 | |
16 | /* Specification: 3.3. Alphabet sizes: insert-and-copy length */ |
17 | #define BROTLI_NUM_LITERAL_SYMBOLS 256 |
18 | #define BROTLI_NUM_COMMAND_SYMBOLS 704 |
19 | #define BROTLI_NUM_BLOCK_LEN_SYMBOLS 26 |
20 | #define BROTLI_MAX_CONTEXT_MAP_SYMBOLS (BROTLI_MAX_NUMBER_OF_BLOCK_TYPES + \ |
21 | BROTLI_CONTEXT_MAP_MAX_RLE) |
22 | #define BROTLI_MAX_BLOCK_TYPE_SYMBOLS (BROTLI_MAX_NUMBER_OF_BLOCK_TYPES + 2) |
23 | |
24 | /* Specification: 3.5. Complex prefix codes */ |
25 | #define BROTLI_REPEAT_PREVIOUS_CODE_LENGTH 16 |
26 | #define BROTLI_REPEAT_ZERO_CODE_LENGTH 17 |
27 | #define BROTLI_CODE_LENGTH_CODES (BROTLI_REPEAT_ZERO_CODE_LENGTH + 1) |
28 | /* "code length of 8 is repeated" */ |
29 | #define BROTLI_INITIAL_REPEATED_CODE_LENGTH 8 |
30 | |
31 | /* "Large Window Brotli" */ |
32 | #define BROTLI_LARGE_MAX_DISTANCE_BITS 62U |
33 | #define BROTLI_LARGE_MIN_WBITS 10 |
34 | #define BROTLI_LARGE_MAX_WBITS 30 |
35 | |
36 | /* Specification: 4. Encoding of distances */ |
37 | #define BROTLI_NUM_DISTANCE_SHORT_CODES 16 |
38 | #define BROTLI_MAX_NPOSTFIX 3 |
39 | #define BROTLI_MAX_NDIRECT 120 |
40 | #define BROTLI_MAX_DISTANCE_BITS 24U |
41 | #define BROTLI_DISTANCE_ALPHABET_SIZE(NPOSTFIX, NDIRECT, MAXNBITS) ( \ |
42 | BROTLI_NUM_DISTANCE_SHORT_CODES + (NDIRECT) + \ |
43 | ((MAXNBITS) << ((NPOSTFIX) + 1))) |
44 | /* BROTLI_NUM_DISTANCE_SYMBOLS == 1128 */ |
45 | #define BROTLI_NUM_DISTANCE_SYMBOLS \ |
46 | BROTLI_DISTANCE_ALPHABET_SIZE( \ |
47 | BROTLI_MAX_NDIRECT, BROTLI_MAX_NPOSTFIX, BROTLI_LARGE_MAX_DISTANCE_BITS) |
48 | #define BROTLI_MAX_DISTANCE 0x3FFFFFC |
49 | #define BROTLI_MAX_ALLOWED_DISTANCE 0x7FFFFFFC |
50 | |
51 | /* 7.1. Context modes and context ID lookup for literals */ |
52 | /* "context IDs for literals are in the range of 0..63" */ |
53 | #define BROTLI_LITERAL_CONTEXT_BITS 6 |
54 | |
55 | /* 7.2. Context ID for distances */ |
56 | #define BROTLI_DISTANCE_CONTEXT_BITS 2 |
57 | |
58 | /* 9.1. Format of the Stream Header */ |
59 | /* Number of slack bytes for window size. Don't confuse |
60 | with BROTLI_NUM_DISTANCE_SHORT_CODES. */ |
61 | #define BROTLI_WINDOW_GAP 16 |
62 | #define BROTLI_MAX_BACKWARD_LIMIT(W) (((size_t)1 << (W)) - BROTLI_WINDOW_GAP) |
63 | |
64 | #endif /* BROTLI_COMMON_CONSTANTS_H_ */ |
65 | |