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 const uint8_t size_bits_by_length[32]; 31 32 /* assert(offset[i + 1] == offset[i] + (bits[i] ? (i << bits[i]) : 0)) */ 33 const uint32_t offsets_by_length[32]; 34 35 /* assert(data_size == offsets_by_length[31]) */ 36 const 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 extern 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
