FreeBSD/Linux Kernel Cross Reference
sys/contrib/openzfs/module/zstd/lib/compress/zstd_ldm.h

     /*
      * Copyright (c) 2016-2020, Yann Collet, Facebook, Inc.
      * All rights reserved.
      *
      * This source code is licensed under both the BSD-style license (found in the
      * LICENSE file in the root directory of this source tree) and the GPLv2 (found
      * in the COPYING file in the root directory of this source tree).
      * You may select, at your option, one of the above-listed licenses.
      */
    
    #ifndef ZSTD_LDM_H
    #define ZSTD_LDM_H
    
    #if defined (__cplusplus)
    extern "C" {
    #endif
    
    #include "zstd_compress_internal.h"   /* ldmParams_t, U32 */
    #include "../zstd.h"   /* ZSTD_CCtx, size_t */
    
    /*-*************************************
    *  Long distance matching
    ***************************************/
    
    #define ZSTD_LDM_DEFAULT_WINDOW_LOG ZSTD_WINDOWLOG_LIMIT_DEFAULT
    
    void ZSTD_ldm_fillHashTable(
                ldmState_t* state, const BYTE* ip,
                const BYTE* iend, ldmParams_t const* params);
    
    /**
     * ZSTD_ldm_generateSequences():
     *
     * Generates the sequences using the long distance match finder.
     * Generates long range matching sequences in `sequences`, which parse a prefix
     * of the source. `sequences` must be large enough to store every sequence,
     * which can be checked with `ZSTD_ldm_getMaxNbSeq()`.
     * @returns 0 or an error code.
     *
     * NOTE: The user must have called ZSTD_window_update() for all of the input
     * they have, even if they pass it to ZSTD_ldm_generateSequences() in chunks.
     * NOTE: This function returns an error if it runs out of space to store
     *       sequences.
     */
    size_t ZSTD_ldm_generateSequences(
                ldmState_t* ldms, rawSeqStore_t* sequences,
                ldmParams_t const* params, void const* src, size_t srcSize);
    
    /**
     * ZSTD_ldm_blockCompress():
     *
     * Compresses a block using the predefined sequences, along with a secondary
     * block compressor. The literals section of every sequence is passed to the
     * secondary block compressor, and those sequences are interspersed with the
     * predefined sequences. Returns the length of the last literals.
     * Updates `rawSeqStore.pos` to indicate how many sequences have been consumed.
     * `rawSeqStore.seq` may also be updated to split the last sequence between two
     * blocks.
     * @return The length of the last literals.
     *
     * NOTE: The source must be at most the maximum block size, but the predefined
     * sequences can be any size, and may be longer than the block. In the case that
     * they are longer than the block, the last sequences may need to be split into
     * two. We handle that case correctly, and update `rawSeqStore` appropriately.
     * NOTE: This function does not return any errors.
     */
    size_t ZSTD_ldm_blockCompress(rawSeqStore_t* rawSeqStore,
                ZSTD_matchState_t* ms, seqStore_t* seqStore, U32 rep[ZSTD_REP_NUM],
                void const* src, size_t srcSize);
    
    /**
     * ZSTD_ldm_skipSequences():
     *
     * Skip past `srcSize` bytes worth of sequences in `rawSeqStore`.
     * Avoids emitting matches less than `minMatch` bytes.
     * Must be called for data with is not passed to ZSTD_ldm_blockCompress().
     */
    void ZSTD_ldm_skipSequences(rawSeqStore_t* rawSeqStore, size_t srcSize,
        U32 const minMatch);
    
    
    /** ZSTD_ldm_getTableSize() :
     *  Estimate the space needed for long distance matching tables or 0 if LDM is
     *  disabled.
     */
    size_t ZSTD_ldm_getTableSize(ldmParams_t params);
    
    /** ZSTD_ldm_getSeqSpace() :
     *  Return an upper bound on the number of sequences that can be produced by
     *  the long distance matcher, or 0 if LDM is disabled.
     */
    size_t ZSTD_ldm_getMaxNbSeq(ldmParams_t params, size_t maxChunkSize);
    
    /** ZSTD_ldm_adjustParameters() :
     *  If the params->hashRateLog is not set, set it to its default value based on
     *  windowLog and params->hashLog.
     *
     *  Ensures that params->bucketSizeLog is <= params->hashLog (setting it to
     *  params->hashLog if it is not).
    *
    *  Ensures that the minMatchLength >= targetLength during optimal parsing.
    */
   void ZSTD_ldm_adjustParameters(ldmParams_t* params,
                                  ZSTD_compressionParameters const* cParams);
   
   #if defined (__cplusplus)
   }
   #endif
   
   #endif /* ZSTD_FAST_H */

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