From: Yann Collet <cyan@fb.com>
Date: Wed, 25 Oct 2017 05:07:08 +0000 (+0200)
Subject: added hash chain with conditional length
X-Git-Tag: upstream/1.9.3~11^2~25^2~32
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=16a433747309d209c2247c5074ff3ac8783548c7;p=platform%2Fupstream%2Flz4.git

added hash chain with conditional length

not a success yet
---

diff --git a/lib/lz4hc.c b/lib/lz4hc.c
index adabd9c..4532ba3 100644
--- a/lib/lz4hc.c
+++ b/lib/lz4hc.c
@@ -195,12 +195,6 @@ LZ4_FORCE_INLINE int LZ4HC_InsertAndGetWiderMatch (
 
     while ((matchIndex>=lowLimit) && (nbAttempts)) {
         nbAttempts--;
-        int trace = 0;
-        if (nbAttempts==0) {
-            trace = 1;
-            DEBUGLOG(2, "reached max nb of attempts ! : %08X => %08X ",
-                pattern, HASH_FUNCTION(pattern));
-        }
         if (matchIndex >= dictLimit) {
             const BYTE* const matchPtr = base + matchIndex;
             if (*(iLowLimit + longest) == *(matchPtr - delta + longest)) {
@@ -249,7 +243,6 @@ LZ4_FORCE_INLINE int LZ4HC_InsertAndGetWiderMatch (
         {   U32 const nextOffset = DELTANEXTU16(chainTable, matchIndex);
             matchIndex -= nextOffset;
             if (1 && (nextOffset==1)) {
-                if (trace) DEBUGLOG(2, "check repeat mode : %u", repeat);
                 /* may be a repeated pattern */
                 if (repeat == rep_untested) {
                     if ((pattern & 0xFFFF) == (pattern >> 16)) {   /* is it enough ? */
@@ -261,13 +254,11 @@ LZ4_FORCE_INLINE int LZ4HC_InsertAndGetWiderMatch (
                 if ( (repeat == rep_confirmed)   /* proven repeated pattern (1-2-4) */
                   && (matchIndex >= dictLimit) ) {   /* same segment only */
                     const BYTE* const matchPtr = base + matchIndex;
-                    if (trace) DEBUGLOG(2, "search direct pattern position");
                     if (LZ4_read32(matchPtr) == pattern) {  /* good candidate */
                         size_t const forwardPatternLength = LZ4HC_countPattern(matchPtr+sizeof(pattern), iHighLimit, pattern) + sizeof(pattern);
                         const BYTE* const maxLowPtr = (lowPrefixPtr + MAX_DISTANCE >= ip) ? lowPrefixPtr : ip - MAX_DISTANCE;
                         size_t const backLength = LZ4HC_reverseCountPattern(matchPtr, maxLowPtr, pattern);
                         size_t const currentSegmentLength = backLength + forwardPatternLength;
-                        if (trace) DEBUGLOG(2, "good start position (match == pattern)");
 
                         if ( (currentSegmentLength >= srcPatternLength)   /* current pattern segment large enough to contain full srcPatternLength */
                           && (forwardPatternLength <= srcPatternLength) ) { /* haven't reached this position yet */
diff --git a/lib/lz4opt.h b/lib/lz4opt.h
index ef7b725..bd956ee 100644
--- a/lib/lz4opt.h
+++ b/lib/lz4opt.h
@@ -213,7 +213,7 @@ LZ4_FORCE_INLINE int LZ4HC_HashChain_GetAllMatches (
 {
     const BYTE* matchPtr;
     int matchLength = LZ4HC_FindLongerMatch(ctx, ip, iHighLimit, (int)best_mlen, &matchPtr, ctx->searchNum);
-    if (matchLength < MINMATCH) return 0;
+    if ((size_t)matchLength <= best_mlen) return 0;
     assert(matches != NULL);
     matches[0].len = matchLength;
     matches[0].off = (int)(ip-matchPtr);
@@ -327,6 +327,7 @@ static int LZ4HC_compress_optimal (
 
             //nb_matches = LZ4HC_BinTree_GetAllMatches(ctx, curPtr, matchlimit, MINMATCH-1, matches, fullUpdate);
             nb_matches = LZ4HC_HashChain_GetAllMatches(ctx, curPtr, matchlimit, MINMATCH-1, matches, fullUpdate);
+            //nb_matches = LZ4HC_HashChain_GetAllMatches(ctx, curPtr, matchlimit, last_match_pos - cur + 1, matches, fullUpdate);   /* only works if last_match_pos is really the last match pos */
             if ((nb_matches > 0) && (size_t)matches[nb_matches-1].len > sufficient_len) {
                 /* immediate encoding */
                 best_mlen = matches[nb_matches-1].len;