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)
16extern "C" {
17#endif
18
19typedef 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
44BROTLI_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 */
55BROTLI_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