2 * Copyright (c) Meta Platforms, Inc. and affiliates.
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.
14 #if defined (__cplusplus)
18 #include "zstd_compress_internal.h" /* ldmParams_t, U32 */
19 #include "../zstd.h" /* ZSTD_CCtx, size_t */
21 /*-*************************************
22 * Long distance matching
23 ***************************************/
25 #define ZSTD_LDM_DEFAULT_WINDOW_LOG ZSTD_WINDOWLOG_LIMIT_DEFAULT
27 void ZSTD_ldm_fillHashTable(
28 ldmState_t* state, const BYTE* ip,
29 const BYTE* iend, ldmParams_t const* params);
32 * ZSTD_ldm_generateSequences():
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.
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
45 size_t ZSTD_ldm_generateSequences(
46 ldmState_t* ldms, rawSeqStore_t* sequences,
47 ldmParams_t const* params, void const* src, size_t srcSize);
50 * ZSTD_ldm_blockCompress():
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
59 * @return The length of the last literals.
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.
67 size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
68 ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
69 ZSTD_paramSwitch_e useRowMatchFinder,
70 void const* src, size_t srcSize);
73 * ZSTD_ldm_skipSequences():
75 * Skip past `srcSize` bytes worth of sequences in `rawSeqStore`.
76 * Avoids emitting matches less than `minMatch` bytes.
77 * Must be called for data that is not passed to ZSTD_ldm_blockCompress().
79 void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize,
82 /* ZSTD_ldm_skipRawSeqStoreBytes():
83 * Moves forward in rawSeqStore by nbBytes, updating fields 'pos' and 'posInSequence'.
84 * Not to be used in conjunction with ZSTD_ldm_skipSequences().
85 * Must be called for data with is not passed to ZSTD_ldm_blockCompress().
87 void ZSTD_ldm_skipRawSeqStoreBytes(rawSeqStore_t* rawSeqStore, size_t nbBytes);
89 /** ZSTD_ldm_getTableSize() :
90 * Estimate the space needed for long distance matching tables or 0 if LDM is
93 size_t ZSTD_ldm_getTableSize(ldmParams_t params);
95 /** ZSTD_ldm_getSeqSpace() :
96 * Return an upper bound on the number of sequences that can be produced by
97 * the long distance matcher, or 0 if LDM is disabled.
99 size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize);
101 /** ZSTD_ldm_adjustParameters() :
102 * If the params->hashRateLog is not set, set it to its default value based on
103 * windowLog and params->hashLog.
105 * Ensures that params->bucketSizeLog is <= params->hashLog (setting it to
106 * params->hashLog if it is not).
108 * Ensures that the minMatchLength >= targetLength during optimal parsing.
110 void ZSTD_ldm_adjustParameters(ldmParams_t* params,
111 ZSTD_compressionParameters const* cParams);
113 #if defined (__cplusplus)
117 #endif /* ZSTD_FAST_H */