favorDecSpeed feature can be triggered from lz4frame

and lz4hc.

4 files changed, 27 insertions, 11 deletions

diff --git a/lib/lz4frame.c b/lib/lz4frame.c
index b616463..06a0f7b 100644
--- a/lib/lz4frame.c
+++ b/lib/lz4frame.c
@@ -612,6 +612,9 @@ size_t LZ4F_compressBegin_usingCDict(LZ4F_cctx* cctxPtr,
         /* frame init only for blockLinked : blockIndependent will be init at each block */
         LZ4F_applyCDict(cctxPtr->lz4CtxPtr, cdict, cctxPtr->prefs.compressionLevel);
     }
+    if (preferencesPtr->compressionLevel >= LZ4HC_CLEVEL_MIN) {
+          LZ4_favorDecompressionSpeed(cctxPtr->lz4CtxPtr, preferencesPtr->favorDecSpeed);
+    }
 
     /* Magic Number */
     LZ4F_writeLE32(dstPtr, LZ4F_MAGICNUMBER);
diff --git a/lib/lz4frame.h b/lib/lz4frame.h
index bd715bd..fb434ff 100644
--- a/lib/lz4frame.h
+++ b/lib/lz4frame.h
@@ -173,13 +173,14 @@ typedef struct {
 
 /*! LZ4F_preferences_t :
  *  makes it possible to supply detailed compression parameters to the stream interface.
- *  It's not required to set all fields, as long as the structure was initially memset() to zero.
+ *  Structure is presumed initially memset() to zero, representing default settings.
  *  All reserved fields must be set to zero. */
 typedef struct {
   LZ4F_frameInfo_t frameInfo;
-  int      compressionLevel;       /* 0: default (fast mode); values > LZ4HC_CLEVEL_MAX count as LZ4HC_CLEVEL_MAX; values < 0 trigger "fast acceleration" */
-  unsigned autoFlush;              /* 1 == always flush, to reduce usage of internal buffers */
-  unsigned reserved[4];            /* must be zero for forward compatibility */
+  int      compressionLevel;    /* 0: default (fast mode); values > LZ4HC_CLEVEL_MAX count as LZ4HC_CLEVEL_MAX; values < 0 trigger "fast acceleration" */
+  unsigned autoFlush;           /* 1: always flush, to reduce usage of internal buffers */
+  unsigned favorDecSpeed;       /* 1: parser favors decompression speed vs compression ratio. Only works for high compression modes (>= LZ4LZ4HC_CLEVEL_OPT_MIN) */  /* >= v1.8.2 */
+  unsigned reserved[3];         /* must be zero for forward compatibility */
 } LZ4F_preferences_t;
 
 LZ4FLIB_API int LZ4F_compressionLevel_max(void);
diff --git a/lib/lz4hc.c b/lib/lz4hc.c
index 3593da7..b90d60b 100644
--- a/lib/lz4hc.c
+++ b/lib/lz4hc.c
@@ -876,6 +876,11 @@ void LZ4_setCompressionLevel(LZ4_streamHC_t* LZ4_streamHCPtr, int compressionLev
     LZ4_streamHCPtr->internal_donotuse.compressionLevel = compressionLevel;
 }
 
+void LZ4_favorDecompressionSpeed(LZ4_streamHC_t* LZ4_streamHCPtr, int favor)
+{
+    LZ4_streamHCPtr->internal_donotuse.favorDecSpeed = (favor!=0);
+}
+
 int LZ4_loadDictHC (LZ4_streamHC_t* LZ4_streamHCPtr, const char* dictionary, int dictSize)
 {
     LZ4HC_CCtx_internal* const ctxPtr = &LZ4_streamHCPtr->internal_donotuse;
@@ -1120,7 +1125,7 @@ static int LZ4HC_compress_optimal (
     const limitedOutput_directive limit,
     int const fullUpdate,
     const dictCtx_directive dict,
-    HCfavor_e favorDecSpeed
+    const HCfavor_e favorDecSpeed
     )
 {
 #define TRAILING_LITERALS 3
@@ -1136,7 +1141,6 @@ 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 */
diff --git a/lib/lz4hc.h b/lib/lz4hc.h
index 28e2528..bb5e073 100644
--- a/lib/lz4hc.h
+++ b/lib/lz4hc.h
@@ -152,7 +152,8 @@ struct LZ4HC_CCtx_internal
     uint32_t   dictLimit;       /* below that point, need extDict */
     uint32_t   lowLimit;        /* below that point, no more dict */
     uint32_t   nextToUpdate;    /* index from which to continue dictionary update */
-    int        compressionLevel;
+    short      compressionLevel;
+    short      favorDecSpeed;
     const LZ4HC_CCtx_internal* dictCtx;
 };
 
@@ -169,7 +170,8 @@ struct LZ4HC_CCtx_internal
     unsigned int   dictLimit;        /* below that point, need extDict */
     unsigned int   lowLimit;         /* below that point, no more dict */
     unsigned int   nextToUpdate;     /* index from which to continue dictionary update */
-    int            compressionLevel;
+    short          compressionLevel;
+    short          favorDecSpeed;
     const LZ4HC_CCtx_internal* dictCtx;
 };
 
@@ -253,9 +255,9 @@ LZ4_DEPRECATED("use LZ4_resetStreamHC() instead") LZ4LIB_API  int   LZ4_resetStr
  * `srcSizePtr` : value will be updated to indicate how much bytes were read from `src`
  */
 int LZ4_compress_HC_destSize(void* LZ4HC_Data,
-                            const char* src, char* dst,
-                            int* srcSizePtr, int targetDstSize,
-                            int compressionLevel);
+                             const char* src, char* dst,
+                             int* srcSizePtr, int targetDstSize,
+                             int compressionLevel);
 
 /*! LZ4_compress_HC_continue_destSize() : v1.8.0 (experimental)
  *  Similar as LZ4_compress_HC_continue(),
@@ -275,6 +277,12 @@ int LZ4_compress_HC_continue_destSize(LZ4_streamHC_t* LZ4_streamHCPtr,
  */
 void LZ4_setCompressionLevel(LZ4_streamHC_t* LZ4_streamHCPtr, int compressionLevel);
 
+/*! LZ4_favorDecompressionSpeed() : v1.8.2 (experimental)
+ *  Parser will select decisions favoring decompression over compression ratio.
+ *  Only work at highest compression settings (level >= LZ4HC_CLEVEL_OPT_MIN)
+ */
+void LZ4_favorDecompressionSpeed(LZ4_streamHC_t* LZ4_streamHCPtr, int favor);
+
 /*! LZ4_resetStreamHC_fast() :
  *  When an LZ4_streamHC_t is known to be in a internally coherent state,
  *  it can often be prepared for a new compression with almost no work, only