drivers/filesystems/btrfs/zstd/zstd_ldm.h

   1 /*
   2  * Copyright (c) 2016-present, 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  */
   9
  10 #ifndef ZSTD_LDM_H
  11 #define ZSTD_LDM_H
  12
  13 #if defined (__cplusplus)
  14 extern "C" {
  15 #endif
  16
  17 #include "zstd_compress_internal.h"   /* ldmParams_t, U32 */
  18 #include "zstd.h"   /* ZSTD_CCtx, size_t */
  19
  20 /*-*************************************
  21 *  Long distance matching
  22 ***************************************/
  23
  24 #define ZSTD_LDM_DEFAULT_WINDOW_LOG ZSTD_WINDOWLOG_DEFAULTMAX
  25
  26 /**
  27  * ZSTD_ldm_generateSequences():
  28  *
  29  * Generates the sequences using the long distance match finder.
  30  * Generates long range matching sequences in `sequences`, which parse a prefix
  31  * of the source. `sequences` must be large enough to store every sequence,
  32  * which can be checked with `ZSTD_ldm_getMaxNbSeq()`.
  33  * @returns 0 or an error code.
  34  *
  35  * NOTE: The user must have called ZSTD_window_update() for all of the input
  36  * they have, even if they pass it to ZSTD_ldm_generateSequences() in chunks.
  37  * NOTE: This function returns an error if it runs out of space to store
  38  *       sequences.
  39  */
  40 size_t ZSTD_ldm_generateSequences(
  41             ldmState_t* ldms, rawSeqStore_t* sequences,
  42             ldmParams_t const* params, void const* src, size_t srcSize);
  43
  44 /**
  45  * ZSTD_ldm_blockCompress():
  46  *
  47  * Compresses a block using the predefined sequences, along with a secondary
  48  * block compressor. The literals section of every sequence is passed to the
  49  * secondary block compressor, and those sequences are interspersed with the
  50  * predefined sequences. Returns the length of the last literals.
  51  * Updates `rawSeqStore.pos` to indicate how many sequences have been consumed.
  52  * `rawSeqStore.seq` may also be updated to split the last sequence between two
  53  * blocks.
  54  * @return The length of the last literals.
  55  *
  56  * NOTE: The source must be at most the maximum block size, but the predefined
  57  * sequences can be any size, and may be longer than the block. In the case that
  58  * they are longer than the block, the last sequences may need to be split into
  59  * two. We handle that case correctly, and update `rawSeqStore` appropriately.
  60  * NOTE: This function does not return any errors.
  61  */
  62 size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
  63             ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
  64             void const* src, size_t srcSize);
  65
  66 /**
  67  * ZSTD_ldm_skipSequences():
  68  *
  69  * Skip past `srcSize` bytes worth of sequences in `rawSeqStore`.
  70  * Avoids emitting matches less than `minMatch` bytes.
  71  * Must be called for data with is not passed to ZSTD_ldm_blockCompress().
  72  */
  73 void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize,
  74     U32 const minMatch);
  75
  76
  77 /** ZSTD_ldm_getTableSize() :
  78  *  Estimate the space needed for long distance matching tables or 0 if LDM is
  79  *  disabled.
  80  */
  81 size_t ZSTD_ldm_getTableSize(ldmParams_t params);
  82
  83 /** ZSTD_ldm_getSeqSpace() :
  84  *  Return an upper bound on the number of sequences that can be produced by
  85  *  the long distance matcher, or 0 if LDM is disabled.
  86  */
  87 size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize);
  88
  89 /** ZSTD_ldm_getTableSize() :
  90  *  Return prime8bytes^(minMatchLength-1) */
  91 U64 ZSTD_ldm_getHashPower(U32 minMatchLength);
  92
  93 /** ZSTD_ldm_adjustParameters() :
  94  *  If the params->hashEveryLog is not set, set it to its default value based on
  95  *  windowLog and params->hashLog.
  96  *
  97  *  Ensures that params->bucketSizeLog is <= params->hashLog (setting it to
  98  *  params->hashLog if it is not).
  99  *
 100  *  Ensures that the minMatchLength >= targetLength during optimal parsing.
 101  */
 102 void ZSTD_ldm_adjustParameters(ldmParams_t* params,
 103                                ZSTD_compressionParameters const* cParams);
 104
 105 #if defined (__cplusplus)
 106 }
 107 #endif
 108
 109 #endif /* ZSTD_FAST_H */