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refactored greedy

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This commit is contained in:
Yann Collet 2015-11-19 17:28:35 +01:00
parent b3a2af970e
commit c95f899725
1 changed files with 44 additions and 41 deletions
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85
lib/zstd_compress.c
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@ -1218,8 +1218,8 @@ FORCE_INLINE size_t ZSTD_HcFindBestMatch_selectMLS (
/* common lazy function, to be inlined */ /* common lazy function, to be inlined */
FORCE_INLINE FORCE_INLINE
size_t ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx, size_t ZSTD_compressBlock_lazy_generic(ZSTD_CCtx* ctx,
void* dst, size_t maxDstSize, const void* src, size_t srcSize, void* dst, size_t maxDstSize, const void* src, size_t srcSize,
const U32 searchMethod, const U32 deep) /* searchMethod : 0 = hc; 1 = bt */ const U32 searchMethod, const U32 deep) /* 0 : hc; 1 : bt */
{ {
seqStore_t* seqStorePtr = &(ctx->seqStore); seqStore_t* seqStorePtr = &(ctx->seqStore);
const BYTE* const istart = (const BYTE*)src; const BYTE* const istart = (const BYTE*)src;
@ -1389,13 +1389,49 @@ size_t ZSTD_compressBlock_greedy(ZSTD_CCtx* ctx, void* dst, size_t maxDstSize, c
/* Match Loop */ /* Match Loop */
while (ip < ilimit) while (ip < ilimit)
{ {
/* repcode */ size_t matchLength;
if (MEM_read32(ip) == MEM_read32(ip - offset_2)) size_t offset;
/* priority to repcode at ip+1 */
if (MEM_read32(ip+1) == MEM_read32(ip+1 - offset_1))
{
matchLength = ZSTD_count(ip+1+MINMATCH, ip+1+MINMATCH-offset_1, iend) + MINMATCH;
ip ++;
offset = 0;
}
else
{
/* search */
offset = 99999999; /* init to high value */
matchLength = ZSTD_HcFindBestMatch_selectMLS(ctx, ip, iend, &offset, maxSearches, mls);
if (matchLength < MINMATCH)
{
/* not found */
ip += ((ip-anchor) >> g_searchStrength) + 1; /* jump faster over incompressible sections */
continue;
}
/* match found */
while ((ip>anchor) && (ip-offset>ctx->base) && (ip[-1] == ip[-1-offset])) { ip--; matchLength++; } /* catch up */
}
/* store found sequence */
{
size_t litLength = ip-anchor;
offset_2 = offset_1;
if (offset) offset_1 = offset;
ZSTD_storeSeq(seqStorePtr, litLength, anchor, offset, matchLength-MINMATCH);
ip += matchLength;
anchor = ip;
}
/* check immediate repcode */
while ( (ip <= ilimit)
&& (MEM_read32(ip) == MEM_read32(ip - offset_2)) )
{ {
/* store sequence */ /* store sequence */
size_t matchLength = ZSTD_count(ip+MINMATCH, ip+MINMATCH-offset_2, iend);
size_t litLength = ip-anchor; size_t litLength = ip-anchor;
size_t offset = offset_2; matchLength = ZSTD_count(ip+MINMATCH, ip+MINMATCH-offset_2, iend);
offset = offset_2;
offset_2 = offset_1; offset_2 = offset_1;
offset_1 = offset; offset_1 = offset;
ZSTD_storeSeq(seqStorePtr, litLength, anchor, 0, matchLength); ZSTD_storeSeq(seqStorePtr, litLength, anchor, 0, matchLength);
@ -1403,39 +1439,7 @@ size_t ZSTD_compressBlock_greedy(ZSTD_CCtx* ctx, void* dst, size_t maxDstSize, c
anchor = ip; anchor = ip;
continue; continue;
} }
offset_2 = offset_1; /* failed once : necessarily offset_1 now */
/* repcode at ip+1 */
if (MEM_read32(ip+1) == MEM_read32(ip+1 - offset_1))
{
size_t matchLength = ZSTD_count(ip+1+MINMATCH, ip+1+MINMATCH-offset_1, iend);
size_t litLength = ip+1-anchor;
ZSTD_storeSeq(seqStorePtr, litLength, anchor, 0, matchLength);
ip += 1+matchLength+MINMATCH;
anchor = ip;
continue;
}
/* search */
{
size_t offset=999999;
size_t matchLength = ZSTD_HcFindBestMatch_selectMLS(ctx, ip, iend, &offset, maxSearches, mls);
if (matchLength < MINMATCH)
{
ip += ((ip-anchor) >> g_searchStrength) + 1; /* jump faster over incompressible sections */
continue;
}
while ((ip>anchor) && (ip-offset>ctx->base) && (ip[-1] == ip[-1-offset])) { ip--; matchLength++; } /* catch up */
/* store sequence */
{
size_t litLength = ip-anchor;
offset_1 = offset;
ZSTD_storeSeq(seqStorePtr, litLength, anchor, offset_1, matchLength-MINMATCH);
ip += matchLength;
anchor = ip;
}
}
} }
/* Last Literals */ /* Last Literals */
@ -1496,7 +1500,6 @@ static ZSTD_blockCompressor ZSTD_selectBlockCompressor(ZSTD_strategy strat, int
size_t ZSTD_compressBlock(ZSTD_CCtx* ctx, void* dst, size_t maxDstSize, const void* src, size_t srcSize) size_t ZSTD_compressBlock(ZSTD_CCtx* ctx, void* dst, size_t maxDstSize, const void* src, size_t srcSize)
{ {
ZSTD_blockCompressor blockCompressor = ZSTD_selectBlockCompressor(ctx->params.strategy, ctx->lowLimit < ctx->dictLimit); ZSTD_blockCompressor blockCompressor = ZSTD_selectBlockCompressor(ctx->params.strategy, ctx->lowLimit < ctx->dictLimit);
if (srcSize < MIN_CBLOCK_SIZE+3) return 0; /* don't even attempt compression below a certain srcSize */
return blockCompressor(ctx, dst, maxDstSize, src, srcSize); return blockCompressor(ctx, dst, maxDstSize, src, srcSize);
} }
@ -1537,7 +1540,7 @@ static size_t ZSTD_compress_generic (ZSTD_CCtx* ctxPtr,
op[0] = (BYTE)(cSize>>16); op[0] = (BYTE)(cSize>>16);
op[1] = (BYTE)(cSize>>8); op[1] = (BYTE)(cSize>>8);
op[2] = (BYTE)cSize; op[2] = (BYTE)cSize;
op[0] += (BYTE)(bt_compressed << 6); /* is a compressed block */ op[0] += (BYTE)(bt_compressed << 6); /* is a compressed block */
cSize += 3; cSize += 3;
} }