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Fix small LZSA2 token reduction inefficiency

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Emmanuel Marty 2019-10-03 16:58:34 +02:00 committed by GitHub
parent 29c6f3b2a3
commit 33327201f7
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1 changed files with 8 additions and 3 deletions
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9
src/shrink_block_v2.c
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@ -417,9 +417,11 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
* matching large regions of identical bytes for instance, where there are too many offsets to be considered by the parser, and when not compressing to favor the * matching large regions of identical bytes for instance, where there are too many offsets to be considered by the parser, and when not compressing to favor the
* ratio (the forward arrivals parser already has this covered). */ * ratio (the forward arrivals parser already has this covered). */
if (i >= nRepMatchOffset && if (i >= nRepMatchOffset &&
(i - nRepMatchOffset + pMatch->length) <= (nEndOffset - LAST_LITERALS) && (i - nRepMatchOffset + pMatch->length) <= (nEndOffset - LAST_LITERALS) &&
!memcmp(pInWindow + i - nRepMatchOffset, pInWindow + i - pMatch->offset, pMatch->length)) !memcmp(pInWindow + i - nRepMatchOffset, pInWindow + i - pMatch->offset, pMatch->length)) {
pMatch->offset = nRepMatchOffset; pMatch->offset = nRepMatchOffset;
nDidReduce = 1;
}
} }
if (pBestMatch[nNextIndex].offset && pMatch->offset != pBestMatch[nNextIndex].offset && nRepMatchOffset != pBestMatch[nNextIndex].offset) { if (pBestMatch[nNextIndex].offset && pMatch->offset != pBestMatch[nNextIndex].offset && nRepMatchOffset != pBestMatch[nNextIndex].offset) {
@ -431,6 +433,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
if (nMaxLen >= pMatch->length) { if (nMaxLen >= pMatch->length) {
/* Replace */ /* Replace */
pMatch->offset = pBestMatch[nNextIndex].offset; pMatch->offset = pBestMatch[nNextIndex].offset;
nDidReduce = 1;
} }
else if (nMaxLen >= 2 && pMatch->offset != nRepMatchOffset) { else if (nMaxLen >= 2 && pMatch->offset != nRepMatchOffset) {
int nPartialSizeBefore, nPartialSizeAfter; int nPartialSizeBefore, nPartialSizeAfter;
@ -452,6 +455,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
pBestMatch[i + j].length = 0; pBestMatch[i + j].length = 0;
} }
pMatch->length = nMaxLen; pMatch->length = nMaxLen;
nDidReduce = 1;
} }
} }
} }
@ -502,6 +506,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
pMatch->length += pBestMatch[i + nMatchLen].length; pMatch->length += pBestMatch[i + nMatchLen].length;
pBestMatch[i + nMatchLen].offset = 0; pBestMatch[i + nMatchLen].offset = 0;
pBestMatch[i + nMatchLen].length = -1; pBestMatch[i + nMatchLen].length = -1;
nDidReduce = 1;
continue; continue;
} }