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Add CCtx Param Controlling Dict Attachment Behavior

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This commit is contained in:
W. Felix Handte 2018-06-21 17:02:50 -04:00
parent e30f13bde0
commit 01bb1c1016
4 changed files with 47 additions and 1 deletions
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17
lib/compress/zstd_compress.c
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@ -275,6 +275,7 @@ static int ZSTD_isUpdateAuthorized(ZSTD_cParameter param)
case ZSTD_p_ldmMinMatch:
case ZSTD_p_ldmBucketSizeLog:
case ZSTD_p_ldmHashEveryLog:
case ZSTD_p_forceAttachDict:
default:
return 0;
}
@ -319,6 +320,9 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, unsigned v
* default : 0 when using a CDict, 1 when using a Prefix */
return ZSTD_CCtxParam_setParameter(&cctx->requestedParams, param, value);
case ZSTD_p_forceAttachDict:
return ZSTD_CCtxParam_setParameter(&cctx->requestedParams, param, value);
case ZSTD_p_nbWorkers:
if ((value>0) && cctx->staticSize) {
return ERROR(parameter_unsupported); /* MT not compatible with static alloc */
@ -424,6 +428,12 @@ size_t ZSTD_CCtxParam_setParameter(
CCtxParams->forceWindow = (value > 0);
return CCtxParams->forceWindow;
case ZSTD_p_forceAttachDict :
CCtxParams->attachDictPref = value ?
(value > 0 ? ZSTD_dictForceAttach : ZSTD_dictForceCopy) :
ZSTD_dictDefaultAttach;
return CCtxParams->attachDictPref;
case ZSTD_p_nbWorkers :
#ifndef ZSTD_MULTITHREAD
if (value>0) return ERROR(parameter_unsupported);
@ -527,6 +537,9 @@ size_t ZSTD_CCtxParam_getParameter(
case ZSTD_p_forceMaxWindow :
*value = CCtxParams->forceWindow;
break;
case ZSTD_p_forceAttachDict :
*value = CCtxParams->attachDictPref;
break;
case ZSTD_p_nbWorkers :
#ifndef ZSTD_MULTITHREAD
assert(CCtxParams->nbWorkers == 0);
@ -1242,7 +1255,9 @@ static size_t ZSTD_resetCCtx_usingCDict(ZSTD_CCtx* cctx,
256 KB /* ZSTD_btultra */
};
const int attachDict = ( pledgedSrcSize <= attachDictSizeCutoffs[cdict->cParams.strategy]
|| pledgedSrcSize == ZSTD_CONTENTSIZE_UNKNOWN )
|| pledgedSrcSize == ZSTD_CONTENTSIZE_UNKNOWN
|| params.attachDictPref == ZSTD_dictForceAttach )
&& params.attachDictPref != ZSTD_dictForceCopy
&& !params.forceWindow /* dictMatchState isn't correctly
* handled in _enforceMaxDist */
&& cdict->cParams.strategy <= ZSTD_btlazy2

8
lib/compress/zstd_compress_internal.h
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@ -48,6 +48,12 @@ extern "C" {
typedef enum { ZSTDcs_created=0, ZSTDcs_init, ZSTDcs_ongoing, ZSTDcs_ending } ZSTD_compressionStage_e;
typedef enum { zcss_init=0, zcss_load, zcss_flush } ZSTD_cStreamStage;
typedef enum {
ZSTD_dictDefaultAttach = 0,
ZSTD_dictForceAttach = 1,
ZSTD_dictForceCopy = -1,
} ZSTD_dictAttachPref_e;
typedef struct ZSTD_prefixDict_s {
const void* dict;
size_t dictSize;
@ -186,6 +192,8 @@ struct ZSTD_CCtx_params_s {
int forceWindow; /* force back-references to respect limit of
* 1<<wLog, even for dictionary */
ZSTD_dictAttachPref_e attachDictPref;
/* Multithreading: used to pass parameters to mtctx */
unsigned nbWorkers;
unsigned jobSize;

22
lib/zstd.h
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@ -1059,6 +1059,28 @@ typedef enum {
ZSTD_p_forceMaxWindow=1100, /* Force back-reference distances to remain < windowSize,
* even when referencing into Dictionary content (default:0) */
ZSTD_p_forceAttachDict, /* ZSTD supports usage of a CDict in-place
* (avoiding having to copy the compression tables
* from the CDict into the working context). Using
* a CDict in this way saves an initial setup step,
* but comes at the cost of more work per byte of
* input. ZSTD has a simple internal heuristic that
* guesses which strategy will be faster. You can
* use this flag to override that guess.
*
* Note that the by-reference, in-place strategy is
* only used when reusing a compression context
* with compatible compression parameters. (If
* incompatible / uninitialized, the working
* context needs to be cleared anyways, which is
* about as expensive as overwriting it with the
* dictionary context, so there's no savings in
* using the CDict by-ref.)
*
* Values greater than 0 force attaching the dict.
* Values less than 0 force copying the dict.
* 0 selects the default heuristic-guided behavior.
*/
} ZSTD_cParameter;

1
tests/fuzz/zstd_helpers.c
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@ -71,6 +71,7 @@ void FUZZ_setRandomParameters(ZSTD_CCtx *cctx, size_t srcSize, uint32_t *state)
setRand(cctx, ZSTD_p_contentSizeFlag, 0, 1, state);
setRand(cctx, ZSTD_p_checksumFlag, 0, 1, state);
setRand(cctx, ZSTD_p_dictIDFlag, 0, 1, state);
setRand(cctx, ZSTD_p_forceAttachDict, -2, 2, state);
/* Select long distance matchig parameters */
setRand(cctx, ZSTD_p_enableLongDistanceMatching, 0, 1, state);
setRand(cctx, ZSTD_p_ldmHashLog, ZSTD_HASHLOG_MIN, 16, state);