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Free, tiny LZSA2 ratio increase for some files

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Emmanuel Marty 2021-11-26 11:24:44 +01:00 committed by GitHub
parent a48db51134
commit 6389895e41
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 4 additions and 4 deletions
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8
src/shrink_block_v2.c
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@ -200,7 +200,7 @@ static void lzsa_insert_forward_match_v2(lzsa_compressor *pCompressor, const uns
if (nRepLen >= MIN_MATCH_SIZE_V2) {
const int nRepPos = arrival[j].rep_pos;
if (nRepPos > nMatchOffset &&
if (nRepPos >= nMatchOffset &&
(nRepPos + nRepLen) <= nEndOffset) {
if (visited[nRepPos].offset != nMatchOffset || visited[nRepPos].length > nRepLen) {
@ -763,7 +763,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
/* Check if we can change the current match's offset to be the same as the previous match's offset, and get an extra repmatch. This will occur when
* 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). */
if (i > nRepMatchOffset &&
if (i >= nRepMatchOffset &&
(i - nRepMatchOffset + pMatch->length) <= nEndOffset &&
!memcmp(pInWindow + i - nRepMatchOffset, pInWindow + i - pMatch->offset, pMatch->length)) {
pMatch->offset = nRepMatchOffset;
@ -773,7 +773,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
if (pBestMatch[nNextIndex].offset && pMatch->offset != pBestMatch[nNextIndex].offset && nRepMatchOffset != pBestMatch[nNextIndex].offset) {
/* Otherwise, try to gain a match forward as well */
if (i > pBestMatch[nNextIndex].offset && (i - pBestMatch[nNextIndex].offset + pMatch->length) <= nEndOffset) {
if (i >= pBestMatch[nNextIndex].offset && (i - pBestMatch[nNextIndex].offset + pMatch->length) <= nEndOffset) {
int nMaxLen = 0;
while (nMaxLen < pMatch->length && pInWindow[i - pBestMatch[nNextIndex].offset + nMaxLen] == pInWindow[i - pMatch->offset + nMaxLen])
nMaxLen++;
@ -828,7 +828,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
nReducedCommandSize += (pBestMatch[nNextIndex].offset <= 32) ? 4 : ((pBestMatch[nNextIndex].offset <= 512) ? 8 : ((pBestMatch[nNextIndex].offset <= (8192 + 512)) ? 12 : 16));
int nReplaceRepOffset = 0;
if (nRepMatchOffset && nRepMatchOffset != nPrevRepMatchOffset && nRepMatchLen >= MIN_MATCH_SIZE_V2 && nRepMatchOffset != pBestMatch[nNextIndex].offset && nRepIndex > pBestMatch[nNextIndex].offset &&
if (nRepMatchOffset && nRepMatchOffset != nPrevRepMatchOffset && nRepMatchLen >= MIN_MATCH_SIZE_V2 && nRepMatchOffset != pBestMatch[nNextIndex].offset && nRepIndex >= pBestMatch[nNextIndex].offset &&
(nRepIndex - pBestMatch[nNextIndex].offset + nRepMatchLen) <= nEndOffset &&
!memcmp(pInWindow + nRepIndex - nRepMatchOffset, pInWindow + nRepIndex - pBestMatch[nNextIndex].offset, nRepMatchLen)) {
/* Replacing this match command by literals would let us create a repmatch */