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[libzstd] Allow compression parameters to be set with a cdict

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The order you set parameters in the advanced API is not supposed to matter.
However, once you call `ZSTD_CCtx_refCDict()` the compression parameters
cannot be changed. Remove that restriction, and document what parameters
are used when using a CDict.

If the CCtx is in dictionary mode, then the CDict's parameters are used.
If the CCtx is not in dictionary mode, then its requested parameters are
used.
This commit is contained in:
Nick Terrell 2019-03-13 15:23:24 -07:00
parent ea3b81f02c
commit 787b76904a
3 changed files with 22 additions and 18 deletions
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20
lib/compress/zstd_compress.c
View File

@ -450,11 +450,12 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)
switch(param)
{
case ZSTD_c_compressionLevel:
RETURN_ERROR_IF(cctx->cdict, stage_wrong,
"compression level is configured in cdict");
case ZSTD_c_nbWorkers:
RETURN_ERROR_IF((value!=0) && cctx->staticSize, parameter_unsupported,
"MT not compatible with static alloc");
break;
case ZSTD_c_compressionLevel:
case ZSTD_c_windowLog:
case ZSTD_c_hashLog:
case ZSTD_c_chainLog:
@ -462,20 +463,7 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)
case ZSTD_c_minMatch:
case ZSTD_c_targetLength:
case ZSTD_c_strategy:
RETURN_ERROR_IF(cctx->cdict, stage_wrong,
"cparams are configured in cdict");
break;
case ZSTD_c_nbWorkers:
RETURN_ERROR_IF((value!=0) && cctx->staticSize, parameter_unsupported,
"MT not compatible with static alloc");
break;
case ZSTD_c_ldmHashRateLog:
RETURN_ERROR_IF(cctx->cdict, stage_wrong,
"LDM hash rate log is configured in cdict");
break;
case ZSTD_c_format:
case ZSTD_c_contentSizeFlag:
case ZSTD_c_checksumFlag:

9
lib/zstd.h
View File

@ -503,7 +503,10 @@ typedef enum { ZSTD_fast=1,
typedef enum {
/* compression parameters */
/* compression parameters
* Note: When compressing with a ZSTD_CDict these parameters are superseded
* by the parameters used to construct the ZSTD_CDict. See ZSTD_CCtx_refCDict()
* for more info (superseded-by-cdict). */
ZSTD_c_compressionLevel=100, /* Update all compression parameters according to pre-defined cLevel table
* Default level is ZSTD_CLEVEL_DEFAULT==3.
* Special: value 0 means default, which is controlled by ZSTD_CLEVEL_DEFAULT.
@ -705,7 +708,9 @@ ZSTDLIB_API size_t ZSTD_CCtx_loadDictionary(ZSTD_CCtx* cctx, const void* dict, s
/*! ZSTD_CCtx_refCDict() :
* Reference a prepared dictionary, to be used for all next compressed frames.
* Note that compression parameters are enforced from within CDict,
* and supercede any compression parameter previously set within CCtx.
* and supersede any compression parameter previously set within CCtx.
* The parameters ignored are labled as "superseded-by-cdict" in the ZSTD_cParameter enum docs.
* The ignored parameters will be used again if the CCtx is returned to no-dictionary mode.
* The dictionary will remain valid for future compressed frames using same CCtx.
* @result : 0, or an error code (which can be tested with ZSTD_isError()).
* Special : Referencing a NULL CDict means "return to no-dictionary mode".

11
tests/fuzzer.c
View File

@ -1294,6 +1294,17 @@ static int basicUnitTests(U32 seed, double compressibility)
}
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3i : ZSTD_CCtx_refCDict() then set parameters : ", testNb++);
{ ZSTD_CDict* const cdict = ZSTD_createCDict(CNBuffer, dictSize, 1);
CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel, 1) );
CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_hashLog, 12 ));
CHECK_Z( ZSTD_CCtx_refCDict(cctx, cdict) );
CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_compressionLevel, 1) );
CHECK_Z( ZSTD_CCtx_setParameter(cctx, ZSTD_c_hashLog, 12 ));
ZSTD_freeCDict(cdict);
}
DISPLAYLEVEL(3, "OK \n");
DISPLAYLEVEL(3, "test%3i : Dictionary with non-default repcodes : ", testNb++);
{ U32 u; for (u=0; u<nbSamples; u++) samplesSizes[u] = sampleUnitSize; }
dictSize = ZDICT_trainFromBuffer(dictBuffer, dictSize,