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