change experimental parameter name

from ZSTD_c_useBlockSplitter to ZSTD_c_splitAfterSequences.

lib/compress/zstd_compress.c

@@ -598,7 +598,7 @@ ZSTD_bounds ZSTD_cParam_getBounds(ZSTD_cParameter param)
         bounds.upperBound = 1;
         return bounds;
 
-    case ZSTD_c_useBlockSplitter:
+    case ZSTD_c_splitAfterSequences:
         bounds.lowerBound = (int)ZSTD_ps_auto;
         bounds.upperBound = (int)ZSTD_ps_disable;
         return bounds;
@@ -701,7 +701,7 @@ static int ZSTD_isUpdateAuthorized(ZSTD_cParameter param)
     case ZSTD_c_stableOutBuffer:
     case ZSTD_c_blockDelimiters:
     case ZSTD_c_validateSequences:
-    case ZSTD_c_useBlockSplitter:
+    case ZSTD_c_splitAfterSequences:
     case ZSTD_c_useRowMatchFinder:
     case ZSTD_c_deterministicRefPrefix:
     case ZSTD_c_prefetchCDictTables:
@@ -760,7 +760,7 @@ size_t ZSTD_CCtx_setParameter(ZSTD_CCtx* cctx, ZSTD_cParameter param, int value)
     case ZSTD_c_stableOutBuffer:
     case ZSTD_c_blockDelimiters:
     case ZSTD_c_validateSequences:
-    case ZSTD_c_useBlockSplitter:
+    case ZSTD_c_splitAfterSequences:
     case ZSTD_c_blockSplitterLevel:
     case ZSTD_c_useRowMatchFinder:
     case ZSTD_c_deterministicRefPrefix:
@@ -982,8 +982,8 @@ size_t ZSTD_CCtxParams_setParameter(ZSTD_CCtx_params* CCtxParams,
         CCtxParams->validateSequences = value;
         return (size_t)CCtxParams->validateSequences;
 
-    case ZSTD_c_useBlockSplitter:
-        BOUNDCHECK(ZSTD_c_useBlockSplitter, value);
+    case ZSTD_c_splitAfterSequences:
+        BOUNDCHECK(ZSTD_c_splitAfterSequences, value);
         CCtxParams->postBlockSplitter = (ZSTD_paramSwitch_e)value;
         return CCtxParams->postBlockSplitter;
 
@@ -1147,7 +1147,7 @@ size_t ZSTD_CCtxParams_getParameter(
     case ZSTD_c_validateSequences :
         *value = (int)CCtxParams->validateSequences;
         break;
-    case ZSTD_c_useBlockSplitter :
+    case ZSTD_c_splitAfterSequences :
         *value = (int)CCtxParams->postBlockSplitter;
         break;
     case ZSTD_c_blockSplitterLevel :

lib/zstd.h

@@ -491,12 +491,12 @@ typedef enum {
      * ZSTD_c_stableOutBuffer
      * ZSTD_c_blockDelimiters
      * ZSTD_c_validateSequences
-     * ZSTD_c_useBlockSplitter
+     * ZSTD_c_blockSplitterLevel
+     * ZSTD_c_splitAfterSequences
      * ZSTD_c_useRowMatchFinder
      * ZSTD_c_prefetchCDictTables
      * ZSTD_c_enableSeqProducerFallback
      * ZSTD_c_maxBlockSize
-     * ZSTD_c_blockSplitterLevel
      * Because they are not stable, it's necessary to define ZSTD_STATIC_LINKING_ONLY to access them.
      * note : never ever use experimentalParam? names directly;
      *        also, the enums values themselves are unstable and can still change.
@@ -2150,8 +2150,32 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
  */
 #define ZSTD_c_validateSequences ZSTD_c_experimentalParam12
 
-/* ZSTD_c_useBlockSplitter
- * Controlled with ZSTD_paramSwitch_e enum.
+/* ZSTD_c_blockSplitterLevel
+ * note: this parameter only influences the first splitter stage,
+ *       which is active before producing the sequences.
+ *       ZSTD_c_splitAfterSequences controls the next splitter stage,
+ *       which is active after sequence production.
+ *       Note that both can be combined.
+ * Allowed values are between 0 and ZSTD_BLOCKSPLITTER_LEVEL_MAX included.
+ * 0 means "auto", which will select a value depending on current ZSTD_c_strategy.
+ * 1 means no splitting.
+ * Then, values from 2 to 6 are sorted in increasing cpu load order.
+ *
+ * Note that currently the first block is never split,
+ * to ensure expansion guarantees in presence of incompressible data.
+ */
+#define ZSTD_BLOCKSPLITTER_LEVEL_MAX 6
+#define ZSTD_c_blockSplitterLevel ZSTD_c_experimentalParam20
+
+/* ZSTD_c_splitAfterSequences
+ * This is a stronger splitter algorithm,
+ * based on actual sequences previously produced by the selected parser.
+ * It's also slower, and as a consequence, mostly used for high compression levels.
+ * While the post-splitter does overlap with the pre-splitter,
+ * both can nonetheless be combined,
+ * notably with ZSTD_c_blockSplitterLevel at ZSTD_BLOCKSPLITTER_LEVEL_MAX,
+ * resulting in higher compression ratio than just one of them.
+ *
  * Default is ZSTD_ps_auto.
  * Set to ZSTD_ps_disable to never use block splitter.
  * Set to ZSTD_ps_enable to always use block splitter.
@@ -2159,7 +2183,7 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
  * By default, in ZSTD_ps_auto, the library will decide at runtime whether to use
  * block splitting based on the compression parameters.
  */
-#define ZSTD_c_useBlockSplitter ZSTD_c_experimentalParam13
+#define ZSTD_c_splitAfterSequences ZSTD_c_experimentalParam13
 
 /* ZSTD_c_useRowMatchFinder
  * Controlled with ZSTD_paramSwitch_e enum.
@@ -2265,23 +2289,6 @@ ZSTDLIB_STATIC_API size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const vo
  */
 #define ZSTD_c_searchForExternalRepcodes ZSTD_c_experimentalParam19
 
-/* ZSTD_c_blockSplitterLevel
- * note: this parameter only influences the first splitter stage,
- *       which is active before producing the sequences.
- *       ZSTD_c_useBlockSplitter influence the next splitter stage,
- *       which is active after sequence production,
- *       and is more accurate but also slower.
- *       Both can be combined.
- * Allowed values are between 0 and 6.
- * 0 means "auto", which will select a value depending on current ZSTD_c_strategy.
- * 1 means no splitting.
- * Then, values from 2 to 6 are sorted in increasing cpu load order.
- *
- * Note that currently the first block is never split,
- * to ensure expansion guarantees in presence of incompressible data.
- */
-#define ZSTD_BLOCKSPLITTER_LEVEL_MAX 6
-#define ZSTD_c_blockSplitterLevel ZSTD_c_experimentalParam20
 
 /*! ZSTD_CCtx_getParameter() :
  *  Get the requested compression parameter value, selected by enum ZSTD_cParameter,