diff options
| -rw-r--r-- | lib/lz4hc.c | 20 |
1 files changed, 18 insertions, 2 deletions
diff --git a/lib/lz4hc.c b/lib/lz4hc.c index 132673e..6c50db5 100644 --- a/lib/lz4hc.c +++ b/lib/lz4hc.c @@ -1099,6 +1099,7 @@ LZ4HC_FindLongestMatch (LZ4HC_CCtx_internal* hc4, int nbAttempts = maxNbAttempts; U32 const pattern = LZ4_read32(ip); U32 matchIndex; + int fromMStart = 0; DEBUGLOG(7, "LZ4HC_InsertAndGetWiderMatch"); /* First Match */ @@ -1132,8 +1133,8 @@ LZ4HC_FindLongestMatch (LZ4HC_CCtx_internal* hc4, } /* while ((matchIndex>=lowestMatchIndex) && (nbAttempts)) */ assert(longest > MINMATCH); - while ((matchIndex>=lowestMatchIndex) && (nbAttempts)) { - const BYTE* const matchPtr = base + matchIndex; + while ((matchIndex-fromMStart>=lowestMatchIndex) && (nbAttempts)) { + const BYTE* const matchPtr = base + matchIndex - fromMStart; assert(matchIndex < ipIndex); assert(matchIndex >= dictLimit); assert(matchPtr >= lowPrefixPtr); @@ -1146,6 +1147,21 @@ LZ4HC_FindLongestMatch (LZ4HC_CCtx_internal* hc4, if (mlt > longest) { longest = mlt; *matchpos = matchPtr; + matchIndex -= fromMStart; /* beginning of match */ + if (1 && matchIndex + longest <= ipIndex) { + U32 distanceToNextMatch = 1; + int pos; + for (pos = 0; pos <= longest - MINMATCH; pos++) { + U32 const candidateDist = DELTANEXTU16(chainTable, matchIndex + pos); + if (candidateDist > distanceToNextMatch) { + distanceToNextMatch = candidateDist; + fromMStart = pos; + } + } + if (distanceToNextMatch > matchIndex) break; /* avoid overflow */ + matchIndex -= distanceToNextMatch - fromMStart; + continue; + } } } } { U32 const nextOffset = DELTANEXTU16(chainTable, matchIndex); |