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Speed up LZSA2 compression

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Emmanuel Marty 2019-10-08 09:39:18 +02:00 committed by GitHub
parent 39e2a90f81
commit bfb383befd
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GPG Key ID: 4AEE18F83AFDEB23
1 changed files with 24 additions and 13 deletions
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31
src/shrink_block_v2.c
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@ -221,6 +221,7 @@ static void lzsa_optimize_forward_v2(lzsa_compressor *pCompressor, const unsigne
n++) {
if (arrival[((i + 1) << MATCHES_PER_OFFSET_SHIFT) + n].rep_offset == arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].rep_offset) {
exists = 1;
break;
}
}
@ -254,31 +255,41 @@ static void lzsa_optimize_forward_v2(lzsa_compressor *pCompressor, const unsigne
int nMatchOffset = match[m].offset;
int nNoRepmatchOffsetCost = (nMatchOffset <= 32) ? 4 : ((nMatchOffset <= 512) ? 8 : ((nMatchOffset <= (8192 + 512)) ? 12 : 16));
int nStartingMatchLen, k;
int nMaxRepLen[NMATCHES_PER_OFFSET];
if ((i + nMatchLen) > (nEndOffset - LAST_LITERALS))
nMatchLen = nEndOffset - LAST_LITERALS - i;
if (nMatchLen >= LEAVE_ALONE_MATCH_SIZE)
nStartingMatchLen = nMatchLen;
else
nStartingMatchLen = nMinMatchSize;
for (j = 0; j < NMATCHES_PER_OFFSET && arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].from_slot; j++) {
const int nPrevCost = arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].cost;
int nRepOffset = arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].rep_offset;
int nMaxRepLen = 0;
int nCurMaxRepLen = 0;
if (nMatchOffset != nRepOffset &&
nRepOffset &&
i >= nRepOffset &&
(i - nRepOffset + nMatchLen) <= (nEndOffset - LAST_LITERALS)) {
while (nMaxRepLen < nMatchLen && pInWindow[i - nRepOffset + nMaxRepLen] == pInWindow[i - nMatchOffset + nMaxRepLen])
nMaxRepLen++;
while (nCurMaxRepLen < nMatchLen && pInWindow[i - nRepOffset + nCurMaxRepLen] == pInWindow[i - nMatchOffset + nCurMaxRepLen])
nCurMaxRepLen++;
}
nMaxRepLen[j] = nCurMaxRepLen;
}
while (j < NMATCHES_PER_OFFSET)
nMaxRepLen[j++] = 0;
if (nMatchLen >= LEAVE_ALONE_MATCH_SIZE)
nStartingMatchLen = nMatchLen;
else
nStartingMatchLen = nMinMatchSize;
for (k = nStartingMatchLen; k <= nMatchLen; k++) {
int nMatchLenCost = lzsa_get_match_varlen_size_v2(k - MIN_MATCH_SIZE_V2);
lzsa_arrival *pDestSlots = &arrival[(i + k) << MATCHES_PER_OFFSET_SHIFT];
for (j = 0; j < NMATCHES_PER_OFFSET && arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].from_slot; j++) {
const int nPrevCost = arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].cost;
int nRepOffset = arrival[(i << MATCHES_PER_OFFSET_SHIFT) + j].rep_offset;
int nMatchOffsetCost = (nMatchOffset == nRepOffset) ? 0 : nNoRepmatchOffsetCost;
int nCodingChoiceCost = nPrevCost + 8 /* token */ /* the actual cost of the literals themselves accumulates up the chain */ + nMatchOffsetCost + nMatchLenCost;
int exists = 0;
@ -322,7 +333,7 @@ static void lzsa_optimize_forward_v2(lzsa_compressor *pCompressor, const unsigne
* matchfinder offer the offset in the first place, or have too many choices with the same cost to retain the repmatchable offset) when compressing regions
* of identical bytes, for instance. Checking for this provides a big compression win on some files. */
if (i >= nRepOffset && nMaxRepLen >= k) {
if (nMaxRepLen[j] >= k) {
/* A match is possible at the rep offset; insert the extra coding choice. */
nCodingChoiceCost = nPrevCost + 8 /* token */ /* the actual cost of the literals themselves accumulates up the chain */ + /* rep match - no offset cost */ nMatchLenCost;
@ -411,7 +422,7 @@ static int lzsa_optimize_command_count_v2(lzsa_compressor *pCompressor, const un
/* This command is a match, is followed by 'nNextLiterals' literals and then by another match */
if (nRepMatchOffset && pMatch->offset != nRepMatchOffset && (pBestMatch[nNextIndex].offset != pMatch->offset || pBestMatch[nNextIndex].offset == nRepMatchOffset ||
((pMatch->offset <= 32) ? 4 : ((pMatch->offset <= 512) ? 8 : ((pMatch->offset <= (8192 + 512)) ? 12 : 16))) >=
((pMatch->offset <= 32) ? 4 : ((pMatch->offset <= 512) ? 8 : ((pMatch->offset <= (8192 + 512)) ? 12 : 16))) >
((pBestMatch[nNextIndex].offset <= 32) ? 4 : ((pBestMatch[nNextIndex].offset <= 512) ? 8 : ((pBestMatch[nNextIndex].offset <= (8192 + 512)) ? 12 : 16))))) {
/* 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