1 /* 2 * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc. 3 * All rights reserved. 4 * 5 * This source code is licensed under both the BSD-style license (found in the 6 * LICENSE file in the root directory of this source tree) and the GPLv2 (found 7 * in the COPYING file in the root directory of this source tree). 8 * You may select, at your option, one of the above-listed licenses. 9 */ 10 11 #ifndef ZSTD_LDM_H 12 #define ZSTD_LDM_H 13 14 #if defined (__cplusplus) 15 extern "C" { 16 #endif 17 18 #include "zstd_compress_internal.h" /* ldmParams_t, U32 */ 19 #include "../zstd.h" /* ZSTD_CCtx, size_t */ 20 21 /*-************************************* 22 * Long distance matching 23 ***************************************/ 24 25 #define ZSTD_LDM_DEFAULT_WINDOW_LOG ZSTD_WINDOWLOG_LIMIT_DEFAULT 26 27 void ZSTD_ldm_fillHashTable( 28 ldmState_t* state, const BYTE* ip, 29 const BYTE* iend, ldmParams_t const* params); 30 31 /** 32 * ZSTD_ldm_generateSequences(): 33 * 34 * Generates the sequences using the long distance match finder. 35 * Generates long range matching sequences in `sequences`, which parse a prefix 36 * of the source. `sequences` must be large enough to store every sequence, 37 * which can be checked with `ZSTD_ldm_getMaxNbSeq()`. 38 * @returns 0 or an error code. 39 * 40 * NOTE: The user must have called ZSTD_window_update() for all of the input 41 * they have, even if they pass it to ZSTD_ldm_generateSequences() in chunks. 42 * NOTE: This function returns an error if it runs out of space to store 43 * sequences. 44 */ 45 size_t ZSTD_ldm_generateSequences( 46 ldmState_t* ldms, rawSeqStore_t* sequences, 47 ldmParams_t const* params, void const* src, size_t srcSize); 48 49 /** 50 * ZSTD_ldm_blockCompress(): 51 * 52 * Compresses a block using the predefined sequences, along with a secondary 53 * block compressor. The literals section of every sequence is passed to the 54 * secondary block compressor, and those sequences are interspersed with the 55 * predefined sequences. Returns the length of the last literals. 56 * Updates `rawSeqStore.pos` to indicate how many sequences have been consumed. 57 * `rawSeqStore.seq` may also be updated to split the last sequence between two 58 * blocks. 59 * @return The length of the last literals. 60 * 61 * NOTE: The source must be at most the maximum block size, but the predefined 62 * sequences can be any size, and may be longer than the block. In the case that 63 * they are longer than the block, the last sequences may need to be split into 64 * two. We handle that case correctly, and update `rawSeqStore` appropriately. 65 * NOTE: This function does not return any errors. 66 */ 67 size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore, 68 ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM], 69 void const* src, size_t srcSize); 70 71 /** 72 * ZSTD_ldm_skipSequences(): 73 * 74 * Skip past `srcSize` bytes worth of sequences in `rawSeqStore`. 75 * Avoids emitting matches less than `minMatch` bytes. 76 * Must be called for data with is not passed to ZSTD_ldm_blockCompress(). 77 */ 78 void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize, 79 U32 const minMatch); 80 81 /* ZSTD_ldm_skipRawSeqStoreBytes(): 82 * Moves forward in rawSeqStore by nbBytes, updating fields 'pos' and 'posInSequence'. 83 * Not to be used in conjunction with ZSTD_ldm_skipSequences(). 84 * Must be called for data with is not passed to ZSTD_ldm_blockCompress(). 85 */ 86 void ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore_t* rawSeqStore, size_t nbBytes); 87 88 /** ZSTD_ldm_getTableSize() : 89 * Estimate the space needed for long distance matching tables or 0 if LDM is 90 * disabled. 91 */ 92 size_t ZSTD_ldm_getTableSize(ldmParams_t params); 93 94 /** ZSTD_ldm_getSeqSpace() : 95 * Return an upper bound on the number of sequences that can be produced by 96 * the long distance matcher, or 0 if LDM is disabled. 97 */ 98 size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize); 99 100 /** ZSTD_ldm_adjustParameters() : 101 * If the params->hashRateLog is not set, set it to its default value based on 102 * windowLog and params->hashLog. 103 * 104 * Ensures that params->bucketSizeLog is <= params->hashLog (setting it to 105 * params->hashLog if it is not). 106 * 107 * Ensures that the minMatchLength >= targetLength during optimal parsing. 108 */ 109 void ZSTD_ldm_adjustParameters(ldmParams_t* params, 110 ZSTD_compressionParameters const* cParams); 111 112 #if defined (__cplusplus) 113 } 114 #endif 115 116 #endif /* ZSTD_FAST_H */ 117