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introduced cycleLog

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This commit is contained in:
Yann Collet 2016-12-12 00:47:30 +01:00
parent c261f71f6a
commit c3a5c4bef8
1 changed files with 13 additions and 6 deletions
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19
lib/compress/zstd_compress.c
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@ -149,6 +149,14 @@ size_t ZSTD_checkCParams(ZSTD_compressionParameters cParams)
}
/** ZSTD_cycleLog() :
* condition for correct operation : hashLog > 1 */
static U32 ZSTD_cycleLog(U32 hashLog, ZSTD_strategy strat)
{
U32 const btScale = ((U32)strat >= (U32)ZSTD_btlazy2);
return hashLog - btScale;
}
/** ZSTD_adjustCParams() :
optimize `cPar` for a given input (`srcSize` and `dictSize`).
mostly downsizing to reduce memory consumption and initialization.
@ -167,9 +175,9 @@ ZSTD_compressionParameters ZSTD_adjustCParams(ZSTD_compressionParameters cPar, u
if (cPar.windowLog > srcLog) cPar.windowLog = srcLog;
} }
if (cPar.hashLog > cPar.windowLog) cPar.hashLog = cPar.windowLog;
{ U32 const btPlus = (cPar.strategy == ZSTD_btlazy2) | (cPar.strategy == ZSTD_btopt) | (cPar.strategy == ZSTD_btopt2);
U32 const maxChainLog = cPar.windowLog+btPlus;
if (cPar.chainLog > maxChainLog) cPar.chainLog = maxChainLog; } /* <= ZSTD_CHAINLOG_MAX */
{ U32 const cycleLog = ZSTD_cycleLog(cPar.chainLog, cPar.strategy);
if (cycleLog > cPar.windowLog) cPar.chainLog -= (cycleLog - cPar.windowLog);
}
if (cPar.windowLog < ZSTD_WINDOWLOG_ABSOLUTEMIN) cPar.windowLog = ZSTD_WINDOWLOG_ABSOLUTEMIN; /* required for frame header */
@ -2276,10 +2284,9 @@ static size_t ZSTD_compress_generic (ZSTD_CCtx* cctx,
/* preemptive overflow correction */
if (cctx->lowLimit > (2U<<30)) {
U32 const btplus = (cctx->params.cParams.strategy == ZSTD_btlazy2) | (cctx->params.cParams.strategy == ZSTD_btopt) | (cctx->params.cParams.strategy == ZSTD_btopt2);
U32 const chainMask = (1 << (cctx->params.cParams.chainLog - btplus)) - 1;
U32 const cycleMask = (1 << ZSTD_cycleLog(cctx->params.cParams.hashLog, cctx->params.cParams.strategy)) - 1;
U32 const current = (U32)(ip - cctx->base);
U32 const newCurrent = (current & chainMask) + (1 << cctx->params.cParams.windowLog);
U32 const newCurrent = (current & cycleMask) + (1 << cctx->params.cParams.windowLog);
U32 const correction = current - newCurrent;
ZSTD_STATIC_ASSERT(ZSTD_WINDOWLOG_MAX_64 <= 30);
ZSTD_reduceIndex(cctx, correction);