lib/zstd/compress/zstd_ldm.h

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