1 | /* Copyright 2013 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 | /* Collection of static dictionary words. */ |
8 | |
9 | #ifndef BROTLI_COMMON_DICTIONARY_H_ |
10 | #define BROTLI_COMMON_DICTIONARY_H_ |
11 | |
12 | #include <brotli/port.h> |
13 | #include <brotli/types.h> |
14 | |
15 | #if defined(__cplusplus) || defined(c_plusplus) |
16 | extern "C" { |
17 | #endif |
18 | |
19 | typedef struct BrotliDictionary { |
20 | /** |
21 | * Number of bits to encode index of dictionary word in a bucket. |
22 | * |
23 | * Specification: Appendix A. Static Dictionary Data |
24 | * |
25 | * Words in a dictionary are bucketed by length. |
26 | * @c 0 means that there are no words of a given length. |
27 | * Dictionary consists of words with length of [4..24] bytes. |
28 | * Values at [0..3] and [25..31] indices should not be addressed. |
29 | */ |
30 | uint8_t size_bits_by_length[32]; |
31 | |
32 | /* assert(offset[i + 1] == offset[i] + (bits[i] ? (i << bits[i]) : 0)) */ |
33 | uint32_t offsets_by_length[32]; |
34 | |
35 | /* assert(data_size == offsets_by_length[31]) */ |
36 | size_t data_size; |
37 | |
38 | /* Data array is not bound, and should obey to size_bits_by_length values. |
39 | Specified size matches default (RFC 7932) dictionary. Its size is |
40 | defined by data_size */ |
41 | const uint8_t* data; |
42 | } BrotliDictionary; |
43 | |
44 | BROTLI_COMMON_API const BrotliDictionary* BrotliGetDictionary(void); |
45 | |
46 | /** |
47 | * Sets dictionary data. |
48 | * |
49 | * When dictionary data is already set / present, this method is no-op. |
50 | * |
51 | * Dictionary data MUST be provided before BrotliGetDictionary is invoked. |
52 | * This method is used ONLY in multi-client environment (e.g. C + Java), |
53 | * to reduce storage by sharing single dictionary between implementations. |
54 | */ |
55 | BROTLI_COMMON_API void BrotliSetDictionaryData(const uint8_t* data); |
56 | |
57 | #define BROTLI_MIN_DICTIONARY_WORD_LENGTH 4 |
58 | #define BROTLI_MAX_DICTIONARY_WORD_LENGTH 24 |
59 | |
60 | #if defined(__cplusplus) || defined(c_plusplus) |
61 | } /* extern "C" */ |
62 | #endif |
63 | |
64 | #endif /* BROTLI_COMMON_DICTIONARY_H_ */ |
65 | |