introduced ability to parse for decompression speed

triggered through an enum.

Now, it's still necessary to properly expose this capability
all the way up to the cli.

1 files changed, 34 insertions, 19 deletions

diff --git a/lib/lz4hc.c b/lib/lz4hc.c
index 4126ef8..3593da7 100644
--- a/lib/lz4hc.c
+++ b/lib/lz4hc.c
@@ -199,6 +199,7 @@ LZ4HC_reverseCountPattern(const BYTE* ip, const BYTE* const iLow, U32 pattern)
 }
 
 typedef enum { rep_untested, rep_not, rep_confirmed } repeat_state_e;
+typedef enum { favorCompressionRatio=0, favorDecompressionSpeed } HCfavor_e;
 
 LZ4_FORCE_INLINE int
 LZ4HC_InsertAndGetWiderMatch (
@@ -211,7 +212,8 @@ LZ4HC_InsertAndGetWiderMatch (
     const BYTE** startpos,
     const int maxNbAttempts,
     const int patternAnalysis,
-    const dictCtx_directive dict)
+    const dictCtx_directive dict,
+    const HCfavor_e favorDecSpeed)
 {
     U16* const chainTable = hc4->chainTable;
     U32* const HashTable = hc4->hashTable;
@@ -240,7 +242,10 @@ LZ4HC_InsertAndGetWiderMatch (
     while ((matchIndex>=lowLimit) && (nbAttempts)) {
         DEBUGLOG(7, "remaining attempts : %i", nbAttempts);
         nbAttempts--;
-        if (matchIndex >= dictLimit) {
+        assert(matchIndex < ipIndex);
+        if (favorDecSpeed && (ipIndex - matchIndex < 8)) {
+            /* do nothing */
+        } else if (matchIndex >= dictLimit) {
             const BYTE* const matchPtr = base + matchIndex;
             assert(longest >= 1);
             if (LZ4_read16(iLowLimit + longest - 1) == LZ4_read16(matchPtr - delta + longest - 1)) {
@@ -326,14 +331,12 @@ LZ4HC_InsertAndGetWiderMatch (
                 }
             }
 
-            {
-                U32 const nextOffset = DELTANEXTU16(dictCtx->chainTable, dictMatchIndex);
+            {   U32 const nextOffset = DELTANEXTU16(dictCtx->chainTable, dictMatchIndex);
                 dictMatchIndex -= nextOffset;
                 matchIndex -= nextOffset;
             }
         }
     }
-
     return longest;
 }
 
@@ -349,7 +352,7 @@ int LZ4HC_InsertAndFindBestMatch(LZ4HC_CCtx_internal* const hc4,   /* Index tabl
     /* note : LZ4HC_InsertAndGetWiderMatch() is able to modify the starting position of a match (*startpos),
      * but this won't be the case here, as we define iLowLimit==ip,
      * so LZ4HC_InsertAndGetWiderMatch() won't be allowed to search past ip */
-    return LZ4HC_InsertAndGetWiderMatch(hc4, ip, ip, iLimit, MINMATCH-1, matchpos, &uselessPtr, maxNbAttempts, patternAnalysis, dict);
+    return LZ4HC_InsertAndGetWiderMatch(hc4, ip, ip, iLimit, MINMATCH-1, matchpos, &uselessPtr, maxNbAttempts, patternAnalysis, dict, favorCompressionRatio);
 }
 
 
@@ -484,7 +487,7 @@ _Search2:
         if (ip+ml <= mflimit)
             ml2 = LZ4HC_InsertAndGetWiderMatch(ctx,
                             ip + ml - 2, ip + 0, matchlimit, ml, &ref2, &start2,
-                            maxNbAttempts, patternAnalysis, dict);
+                            maxNbAttempts, patternAnalysis, dict, favorCompressionRatio);
         else
             ml2 = ml;
 
@@ -531,7 +534,7 @@ _Search3:
         if (start2 + ml2 <= mflimit)
             ml3 = LZ4HC_InsertAndGetWiderMatch(ctx,
                             start2 + ml2 - 3, start2, matchlimit, ml2, &ref3, &start3,
-                            maxNbAttempts, patternAnalysis, dict);
+                            maxNbAttempts, patternAnalysis, dict, favorCompressionRatio);
         else
             ml3 = ml2;
 
@@ -651,12 +654,14 @@ _dest_overflow:
     return 0;
 }
 
+
 static int LZ4HC_compress_optimal( LZ4HC_CCtx_internal* ctx,
     const char* const source, char* dst,
     int* srcSizePtr, int dstCapacity,
     int const nbSearches, size_t sufficient_len,
     const limitedOutput_directive limit, int const fullUpdate,
-    const dictCtx_directive dict);
+    const dictCtx_directive dict,
+    HCfavor_e favorDecSpeed);
 
 
 LZ4_FORCE_INLINE int LZ4HC_compress_generic_internal (
@@ -711,7 +716,9 @@ LZ4_FORCE_INLINE int LZ4HC_compress_generic_internal (
         return LZ4HC_compress_optimal(ctx,
                             src, dst, srcSizePtr, dstCapacity,
                             cParam.nbSearches, cParam.targetLength, limit,
-                            cLevel == LZ4HC_CLEVEL_MAX, dict);  /* ultra mode */
+                            cLevel == LZ4HC_CLEVEL_MAX,   /* ultra mode */
+                            dict,
+                            favorDecompressionSpeed);
     }
 }
 
@@ -1082,23 +1089,26 @@ LZ4_FORCE_INLINE LZ4HC_match_t
 LZ4HC_FindLongerMatch(LZ4HC_CCtx_internal* const ctx,
                       const BYTE* ip, const BYTE* const iHighLimit,
                       int minLen, int nbSearches,
-                      const dictCtx_directive dict)
+                      const dictCtx_directive dict,
+                      const HCfavor_e favorDecSpeed)
 {
     LZ4HC_match_t match = { 0 , 0 };
     const BYTE* matchPtr = NULL;
     /* note : LZ4HC_InsertAndGetWiderMatch() is able to modify the starting position of a match (*startpos),
      * but this won't be the case here, as we define iLowLimit==ip,
      * so LZ4HC_InsertAndGetWiderMatch() won't be allowed to search past ip */
-    int const matchLength = LZ4HC_InsertAndGetWiderMatch(ctx,
+    int matchLength = LZ4HC_InsertAndGetWiderMatch(ctx,
                                 ip, ip, iHighLimit, minLen, &matchPtr, &ip,
-                                nbSearches, 1 /* patternAnalysis */, dict);
+                                nbSearches, 1 /* patternAnalysis */, dict, favorDecSpeed);
     if (matchLength <= minLen) return match;
+    if (favorDecSpeed) {
+        if ((matchLength>18) & (matchLength<=36)) matchLength=18;   /* favor shortcut */
+    }
     match.len = matchLength;
     match.off = (int)(ip-matchPtr);
     return match;
 }
 
-
 static int LZ4HC_compress_optimal (
     LZ4HC_CCtx_internal* ctx,
     const char* const source,
@@ -1109,7 +1119,8 @@ static int LZ4HC_compress_optimal (
     size_t sufficient_len,
     const limitedOutput_directive limit,
     int const fullUpdate,
-    const dictCtx_directive dict
+    const dictCtx_directive dict,
+    HCfavor_e favorDecSpeed
     )
 {
 #define TRAILING_LITERALS 3
@@ -1125,6 +1136,7 @@ static int LZ4HC_compress_optimal (
     BYTE* oend = op + dstCapacity;
 
     /* init */
+    favorDecSpeed = favorCompressionRatio;
     DEBUGLOG(5, "LZ4HC_compress_optimal");
     *srcSizePtr = 0;
     if (limit == limitedDestSize) oend -= LASTLITERALS;   /* Hack for support LZ4 format restriction */
@@ -1137,7 +1149,7 @@ static int LZ4HC_compress_optimal (
          int best_mlen, best_off;
          int cur, last_match_pos = 0;
 
-         LZ4HC_match_t const firstMatch = LZ4HC_FindLongerMatch(ctx, ip, matchlimit, MINMATCH-1, nbSearches, dict);
+         LZ4HC_match_t const firstMatch = LZ4HC_FindLongerMatch(ctx, ip, matchlimit, MINMATCH-1, nbSearches, dict, favorDecSpeed);
          if (firstMatch.len==0) { ip++; continue; }
 
          if ((size_t)firstMatch.len > sufficient_len) {
@@ -1207,10 +1219,10 @@ static int LZ4HC_compress_optimal (
 
              DEBUGLOG(7, "search at rPos:%u", cur);
              if (fullUpdate)
-                 newMatch = LZ4HC_FindLongerMatch(ctx, curPtr, matchlimit, MINMATCH-1, nbSearches, dict);
+                 newMatch = LZ4HC_FindLongerMatch(ctx, curPtr, matchlimit, MINMATCH-1, nbSearches, dict, favorDecSpeed);
              else
                  /* only test matches of minimum length; slightly faster, but misses a few bytes */
-                 newMatch = LZ4HC_FindLongerMatch(ctx, curPtr, matchlimit, last_match_pos - cur, nbSearches, dict);
+                 newMatch = LZ4HC_FindLongerMatch(ctx, curPtr, matchlimit, last_match_pos - cur, nbSearches, dict, favorDecSpeed);
              if (!newMatch.len) continue;
 
              if ( ((size_t)newMatch.len > sufficient_len)
@@ -1258,7 +1270,10 @@ static int LZ4HC_compress_optimal (
                          price = opt[cur].price + LZ4HC_sequencePrice(0, ml);
                      }
 
-                     if (pos > last_match_pos+TRAILING_LITERALS || price <= opt[pos].price) {
+                    assert(opt[pos].price > 1);
+                    assert((U32)favorDecSpeed <= 1);
+                     if (pos > last_match_pos+TRAILING_LITERALS
+                      || price <= opt[pos].price - (int)favorDecSpeed) {
                          DEBUGLOG(7, "rPos:%3i => price:%3i (matchlen=%i)",
                                      pos, price, ml);
                          assert(pos < LZ4_OPT_NUM);