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adding dedicatedDictSearch algorithm

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Bimba Shrestha 2020-06-11 18:54:44 -07:00 committed by W. Felix Handte
parent 31e581bf65
commit 22705f0c93
1 changed files with 44 additions and 4 deletions
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48
lib/compress/zstd_lazy.c
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@ -487,9 +487,9 @@ void ZSTD_lazy_loadDictionary(ZSTD_matchState_t* ms, const BYTE* const ip)
ms->cParams.minMatch) << DD_BLOG; ms->cParams.minMatch) << DD_BLOG;
chainTable[idx & chainMask] = ms->hashTable[h]; chainTable[idx & chainMask] = ms->hashTable[h];
ms->hashTable[h] = idx; ms->hashTable[h] = idx;
/* Same logic as before. But now, just copy the into bucket */ /* Same logic as before. But now, just copy the chain into the bucket */
for (U32 i = 0; i < (1 << DD_BLOG); i++) for (U32 i = 0; i < (1 << DD_BLOG) - 1; i++)
ms->hashTable[h + i] = chainTable[ms->hashTable[h + i] & chainMask]; ms->hashTable[h + i + 1] = chainTable[ms->hashTable[h + i] & chainMask];
} }
ms->nextToUpdate = target; ms->nextToUpdate = target;
} }
@ -550,7 +550,46 @@ size_t ZSTD_HcFindBestMatch_generic (
matchIndex = NEXT_IN_CHAIN(matchIndex, chainMask); matchIndex = NEXT_IN_CHAIN(matchIndex, chainMask);
} }
if (dictMode == ZSTD_dictMatchState) { if (dictMode == ZSTD_dictMatchState && ms->dictMatchState->enableDedicatedDictSearch) {
const ZSTD_matchState_t* const dms = ms->dictMatchState;
const U32 dmsChainSize = (1 << dms->cParams.chainLog);
const U32 dmsChainMask = dmsChainSize - 1;
const U32 dmsLowestIndex = dms->window.dictLimit;
const BYTE* const dmsBase = dms->window.base;
const BYTE* const dmsEnd = dms->window.nextSrc;
const U32 dmsSize = (U32)(dmsEnd - dmsBase);
const U32 dmsIndexDelta = dictLimit - dmsSize;
const U32 dmsMinChain = dmsSize > dmsChainSize ? dmsSize - dmsChainSize : 0;
const U32 bucketSize = (1 << DD_BLOG);
U32 hash = ZSTD_hashPtr(ip, dms->cParams.hashLog - DD_BLOG, mls) << DD_BLOG;
U32 attemptNb = 0;
matchIndex = dms->hashTable[hash];
/* Empty chain */
if (!matchIndex)
return ml;
for ( ; (matchIndex>dmsLowestIndex) & (nbAttempts>0) ; nbAttempts--, attemptNb++) {
size_t currentMl=0;
const BYTE* const match = dmsBase + matchIndex;
assert(match+4 <= dmsEnd);
if (MEM_read32(match) == MEM_read32(ip)) /* assumption : matchIndex <= dictLimit-4 (by table construction) */
currentMl = ZSTD_count_2segments(ip+4, match+4, iLimit, dmsEnd, prefixStart) + 4;
/* save best solution */
if (currentMl > ml) {
ml = currentMl;
*offsetPtr = current - (matchIndex + dmsIndexDelta) + ZSTD_REP_MOVE;
if (ip+currentMl == iLimit) break; /* best possible, avoids read overflow on next attempt */
}
if (matchIndex <= dmsMinChain) break;
if (attemptNb < bucketSize - 1) matchIndex = dms->hashTable[++hash];
else matchIndex = dms->chainTable[matchIndex & dmsChainMask];
}
} else if (dictMode == ZSTD_dictMatchState) {
const ZSTD_matchState_t* const dms = ms->dictMatchState; const ZSTD_matchState_t* const dms = ms->dictMatchState;
const U32* const dmsChainTable = dms->chainTable; const U32* const dmsChainTable = dms->chainTable;
const U32 dmsChainSize = (1 << dms->cParams.chainLog); const U32 dmsChainSize = (1 << dms->cParams.chainLog);
@ -579,6 +618,7 @@ size_t ZSTD_HcFindBestMatch_generic (
} }
if (matchIndex <= dmsMinChain) break; if (matchIndex <= dmsMinChain) break;
matchIndex = dmsChainTable[matchIndex & dmsChainMask]; matchIndex = dmsChainTable[matchIndex & dmsChainMask];
} }
} }