diff options
Diffstat (limited to 'lib/lz4hc.c')
| -rw-r--r-- | lib/lz4hc.c | 74 |
1 files changed, 47 insertions, 27 deletions
diff --git a/lib/lz4hc.c b/lib/lz4hc.c index 29288a5..b8ff72a 100644 --- a/lib/lz4hc.c +++ b/lib/lz4hc.c @@ -151,6 +151,19 @@ int LZ4HC_countBack(const BYTE* const ip, const BYTE* const match, return back; } +#if defined(_MSC_VER) +# define LZ4HC_rotl32(x,r) _rotl(x,r) +#else +# define LZ4HC_rotl32(x,r) ((x << r) | (x >> (32 - r))) +#endif + + +static U32 LZ4HC_rotatePattern(size_t const length, U32 const pattern) +{ + size_t const bitsToRotate = (length & (sizeof(pattern) - 1)) << 3; + return LZ4HC_rotl32(pattern, (int)bitsToRotate); +} + /* LZ4HC_countPattern() : * pattern32 must be a sample of repetitive pattern of length 1, 2 or 4 (but not 3!) */ static unsigned @@ -313,34 +326,41 @@ LZ4HC_InsertAndGetWiderMatch ( } else { repeat = rep_not; } } - if ( (repeat == rep_confirmed) - && (matchCandidateIdx >= dictLimit) ) { /* same segment only */ - const BYTE* const matchPtr = base + matchCandidateIdx; + if ( (repeat == rep_confirmed) && (matchCandidateIdx >= lowestMatchIndex) ) { + const int extDict = matchCandidateIdx < dictLimit; + const BYTE* const matchPtr = (extDict ? dictBase : base) + matchCandidateIdx; if (LZ4_read32(matchPtr) == pattern) { /* good candidate */ - size_t const forwardPatternLength = LZ4HC_countPattern(matchPtr+sizeof(pattern), iHighLimit, pattern) + sizeof(pattern); - const BYTE* const lowestMatchPtr = (lowPrefixPtr + LZ4_DISTANCE_MAX >= ip) ? lowPrefixPtr : ip - LZ4_DISTANCE_MAX; - size_t const backLength = LZ4HC_reverseCountPattern(matchPtr, lowestMatchPtr, pattern); - size_t const currentSegmentLength = backLength + forwardPatternLength; - - if ( (currentSegmentLength >= srcPatternLength) /* current pattern segment large enough to contain full srcPatternLength */ - && (forwardPatternLength <= srcPatternLength) ) { /* haven't reached this position yet */ - matchIndex = matchCandidateIdx + (U32)forwardPatternLength - (U32)srcPatternLength; /* best position, full pattern, might be followed by more match */ - } else { - matchIndex = matchCandidateIdx - (U32)backLength; /* farthest position in current segment, will find a match of length currentSegmentLength + maybe some back */ - if (lookBackLength==0) { /* no back possible */ - size_t const maxML = MIN(currentSegmentLength, srcPatternLength); - if ((size_t)longest < maxML) { - assert(base + matchIndex < ip); - if (ip - (base+matchIndex) > LZ4_DISTANCE_MAX) break; - assert(maxML < 2 GB); - longest = (int)maxML; - *matchpos = base + matchIndex; /* virtual pos, relative to ip, to retrieve offset */ - *startpos = ip; - } - { U32 const distToNextPattern = DELTANEXTU16(chainTable, matchIndex); - if (distToNextPattern > matchIndex) break; /* avoid overflow */ - matchIndex -= distToNextPattern; - } } } + const BYTE* const dictStart = dictBase + hc4->lowLimit; + const BYTE* const iLimit = extDict ? dictBase + dictLimit : iHighLimit; + size_t forwardPatternLength = LZ4HC_countPattern(matchPtr+sizeof(pattern), iLimit, pattern) + sizeof(pattern); + if (extDict && ip + forwardPatternLength == iLimit) { + U32 const rotatedPattern = LZ4HC_rotatePattern(forwardPatternLength, pattern); + forwardPatternLength += LZ4HC_countPattern(lowPrefixPtr, iHighLimit, rotatedPattern); + } + { const BYTE* const lowestMatchPtr = extDict ? dictStart : lowPrefixPtr; + size_t const backLengthRaw = LZ4HC_reverseCountPattern(matchPtr, lowestMatchPtr, pattern); + size_t const backLength = matchCandidateIdx - MAX(matchCandidateIdx - (U32)backLengthRaw, lowestMatchIndex); + size_t const currentSegmentLength = backLength + forwardPatternLength; + + if ( (currentSegmentLength >= srcPatternLength) /* current pattern segment large enough to contain full srcPatternLength */ + && (forwardPatternLength <= srcPatternLength) ) { /* haven't reached this position yet */ + matchIndex = matchCandidateIdx + (U32)forwardPatternLength - (U32)srcPatternLength; /* best position, full pattern, might be followed by more match */ + } else { + matchIndex = matchCandidateIdx - (U32)backLength; /* farthest position in current segment, will find a match of length currentSegmentLength + maybe some back */ + if (lookBackLength==0) { /* no back possible */ + size_t const maxML = MIN(currentSegmentLength, srcPatternLength); + if ((size_t)longest < maxML) { + assert(base + matchIndex < ip); + if (ip - (base+matchIndex) > LZ4_DISTANCE_MAX) break; + assert(maxML < 2 GB); + longest = (int)maxML; + *matchpos = base + matchIndex; /* virtual pos, relative to ip, to retrieve offset */ + *startpos = ip; + } + { U32 const distToNextPattern = DELTANEXTU16(chainTable, matchIndex); + if (distToNextPattern > matchIndex) break; /* avoid overflow */ + matchIndex -= distToNextPattern; + } } } } continue; } } } } /* PA optimization */ |