AuroraMiddleware/lz4
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[lz4hc] Only allow chain swapping forwards

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When the match is very long and found quickly, we can do
matchLength * nbCompares iterations through the chain
swapping, which can really slow down compression.
This commit is contained in:
Nick Terrell 2019-07-30 23:40:58 -07:00
parent be1738aa46
commit 38c3945de3
1 changed files with 1 additions and 1 deletions
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2
lib/lz4hc.c
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@ -314,7 +314,7 @@ LZ4HC_InsertAndGetWiderMatch (
if (matchIndex + (U32)longest <= ipIndex) { if (matchIndex + (U32)longest <= ipIndex) {
U32 distanceToNextMatch = 1; U32 distanceToNextMatch = 1;
int pos; int pos;
for (pos = 0; pos <= longest - MINMATCH; ++pos) { for (pos = matchChainPos; pos <= longest - MINMATCH; ++pos) {
U32 const candidateDist = DELTANEXTU16(chainTable, matchIndex + (U32)pos); U32 const candidateDist = DELTANEXTU16(chainTable, matchIndex + (U32)pos);
if (candidateDist > distanceToNextMatch) { if (candidateDist > distanceToNextMatch) {
distanceToNextMatch = candidateDist; distanceToNextMatch = candidateDist;