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Added support for forcing new CDict behavior and updated enum

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This commit is contained in:
Sen Huang 2019-10-20 14:03:09 -04:00
parent 9294f4826b
commit e4de8b098a
2 changed files with 8 additions and 2 deletions
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3
lib/compress/zstd_compress.c
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@ -2908,7 +2908,8 @@ static size_t ZSTD_compressBegin_internal(ZSTD_CCtx* cctx,
assert(!((dict) && (cdict))); /* either dict or cdict, not both */ assert(!((dict) && (cdict))); /* either dict or cdict, not both */
if ( (cdict) if ( (cdict)
&& (cdict->dictContentSize > 0) && (cdict->dictContentSize > 0)
&& (pledgedSrcSize < ZSTD_USE_CDICT_PARAMS_CUTOFF || cdict->compressionLevel == 0) ) { && (pledgedSrcSize < ZSTD_USE_CDICT_PARAMS_CUTOFF || cdict->compressionLevel == 0)
&& (params->attachDictPref != ZSTD_dictForceInputParams) ) {
return ZSTD_resetCCtx_usingCDict(cctx, cdict, params, pledgedSrcSize, zbuff); return ZSTD_resetCCtx_usingCDict(cctx, cdict, params, pledgedSrcSize, zbuff);
} }

7
lib/zstd.h
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@ -1149,7 +1149,7 @@ typedef enum {
* to evolve and should be considered only in the context of extremely * to evolve and should be considered only in the context of extremely
* advanced performance tuning. * advanced performance tuning.
* *
* Zstd currently supports the use of a CDict in two ways: * Zstd currently supports the use of a CDict in three ways:
* *
* - The contents of the CDict can be copied into the working context. This * - The contents of the CDict can be copied into the working context. This
* means that the compression can search both the dictionary and input * means that the compression can search both the dictionary and input
@ -1165,6 +1165,10 @@ typedef enum {
* working context's tables can be reused). For small inputs, this can be * working context's tables can be reused). For small inputs, this can be
* faster than copying the CDict's tables. * faster than copying the CDict's tables.
* *
* - The CDict's tables are not used at all, and instead we use the working
* context alone to determine how our tables are initialized. This method
* should be used when using a small dictionary to compress a large input.
*
* Zstd has a simple internal heuristic that selects which strategy to use * Zstd has a simple internal heuristic that selects which strategy to use
* at the beginning of a compression. However, if experimentation shows that * at the beginning of a compression. However, if experimentation shows that
* Zstd is making poor choices, it is possible to override that choice with * Zstd is making poor choices, it is possible to override that choice with
@ -1173,6 +1177,7 @@ typedef enum {
ZSTD_dictDefaultAttach = 0, /* Use the default heuristic. */ ZSTD_dictDefaultAttach = 0, /* Use the default heuristic. */
ZSTD_dictForceAttach = 1, /* Never copy the dictionary. */ ZSTD_dictForceAttach = 1, /* Never copy the dictionary. */
ZSTD_dictForceCopy = 2, /* Always copy the dictionary. */ ZSTD_dictForceCopy = 2, /* Always copy the dictionary. */
ZSTD_dictForceInputParams = 3, /* Always use input to determine tables */
} ZSTD_dictAttachPref_e; } ZSTD_dictAttachPref_e;
typedef enum { typedef enum {