module/zstd/lib/compress/zstd_ldm.h

   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
  82 /** ZSTD_ldm_getTableSize() :
  83  *  Estimate the space needed for long distance matching tables or 0 if LDM is
  84  *  disabled.
  85  */
  86 size_t ZSTD_ldm_getTableSize(ldmParams_t params);
  87
  88 /** ZSTD_ldm_getSeqSpace() :
  89  *  Return an upper bound on the number of sequences that can be produced by
  90  *  the long distance matcher, or 0 if LDM is disabled.
  91  */
  92 size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize);
  93
  94 /** ZSTD_ldm_adjustParameters() :
  95  *  If the params->hashRateLog is not set, set it to its default value based on
  96  *  windowLog and params->hashLog.
  97  *
  98  *  Ensures that params->bucketSizeLog is <= params->hashLog (setting it to
  99  *  params->hashLog if it is not).
 100  *
 101  *  Ensures that the minMatchLength >= targetLength during optimal parsing.
 102  */
 103 void ZSTD_ldm_adjustParameters(ldmParams_t* params,
 104                                ZSTD_compressionParameters const* cParams);
 105
 106 #if defined (__cplusplus)
 107 }
 108 #endif
 109
 110 #endif /* ZSTD_FAST_H */