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
} 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 */