Changed nbThreads for nbWorkers

This makes it easier to explain that nbWorkers=0 --> single-threaded mode,
while nbWorkers=1 --> asynchronous mode (one mode thread on top of the "main" caller thread).
No need for an additional asynchronous mode flag.
nbWorkers>=2 works the same as nbThreads>=2 previously.

doc/zstd_manual.html

@@ -416,7 +416,7 @@ size_t ZSTD_estimateDCtxSize(void);
   It will also consider src size to be arbitrarily "large", which is worst case.
   If srcSize is known to always be small, ZSTD_estimateCCtxSize_usingCParams() can provide a tighter estimation.
   ZSTD_estimateCCtxSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
-  ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbThreads is > 1.
+  ZSTD_estimateCCtxSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
   Note : CCtx size estimation is only correct for single-threaded compression. 
 </p></pre><BR>
 
@@ -429,7 +429,7 @@ size_t ZSTD_estimateDStreamSize_fromFrame(const void* src, size_t srcSize);
   It will also consider src size to be arbitrarily "large", which is worst case.
   If srcSize is known to always be small, ZSTD_estimateCStreamSize_usingCParams() can provide a tighter estimation.
   ZSTD_estimateCStreamSize_usingCParams() can be used in tandem with ZSTD_getCParams() to create cParams from compressionLevel.
-  ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbThreads is set to a value > 1.
+  ZSTD_estimateCStreamSize_usingCCtxParams() can be used in tandem with ZSTD_CCtxParam_setParameter(). Only single-threaded compression is supported. This function will return an error code if ZSTD_p_nbWorkers is >= 1.
   Note : CStream size estimation is only correct for single-threaded compression.
   ZSTD_DStream memory budget depends on window Size.
   This information can be passed manually, using ZSTD_estimateDStreamSize,
@@ -800,18 +800,11 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
     </b>/* multi-threading parameters */<b>
     </b>/* These parameters are only useful if multi-threading is enabled (ZSTD_MULTITHREAD).<b>
      * They return an error otherwise. */
-    ZSTD_p_nbThreads=400,    </b>/* Select how many threads a compression job can spawn (default:1)<b>
+    ZSTD_p_nbWorkers=400,    </b>/* Select how many threads will be spawned to compress in parallel.<b>
+                              * Triggers asynchronous mode, even with nbWorkers = 1.
+                              * Can only be set to a value >= 1 if ZSTD_MULTITHREAD is enabled.
                               * More threads improve speed, but also increase memory usage.
-                              * Can only receive a value > 1 if ZSTD_MULTITHREAD is enabled.
-                              * Special: value 0 means "do not change nbThreads" */
-    ZSTD_p_nonBlockingMode,  </b>/* Single thread mode is by default "blocking" :<b>
-                              * it finishes its job as much as possible, and only then gives back control to caller.
-                              * In contrast, multi-thread is by default "non-blocking" :
-                              * it takes some input, flush some output if available, and immediately gives back control to caller.
-                              * Compression work is performed in parallel, within worker threads.
-                              * (note : a strong exception to this rule is when first job is called with ZSTD_e_end : it becomes blocking)
-                              * Setting this parameter to 1 will enforce non-blocking mode even when only 1 thread is selected.
-                              * It allows the caller to do other tasks while the worker thread compresses in parallel. */
+                              * Default value is `0`, aka "blocking mode" : no worker is spawned, compression is performed inside Caller's thread */
     ZSTD_p_jobSize,          </b>/* Size of a compression job. This value is only enforced in streaming (non-blocking) mode.<b>
                               * Each compression job is completed in parallel, so indirectly controls the nb of active threads.
                               * 0 means default, which is dynamically determined based on compression parameters.
@@ -823,7 +816,7 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
     </b>/* advanced parameters - may not remain available after API update */<b>
     ZSTD_p_forceMaxWindow=1100, </b>/* Force back-reference distances to remain < windowSize,<b>
                               * even when referencing into Dictionary content (default:0) */
-    ZSTD_p_enableLongDistanceMatching=1200,  </b>/* Enable long distance matching.<b>
+    ZSTD_p_enableLongDistanceMatching=1200, </b>/* Enable long distance matching.<b>
                                          * This parameter is designed to improve the compression
                                          * ratio for large inputs with long distance matches.
                                          * This increases the memory usage as well as window size.
@@ -833,25 +826,29 @@ size_t ZSTD_decodingBufferSize_min(unsigned long long windowSize, unsigned long
                                          * other LDM parameters. Setting the compression level
                                          * after this parameter overrides the window log, though LDM
                                          * will remain enabled until explicitly disabled. */
-    ZSTD_p_ldmHashLog,   </b>/* Size of the table for long distance matching, as a power of 2.<b>
-                          * Larger values increase memory usage and compression ratio, but decrease
-                          * compression speed.
-                          * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
-                          * (default: windowlog - 7). */
-    ZSTD_p_ldmMinMatch,  </b>/* Minimum size of searched matches for long distance matcher.<b>
-                          * Larger/too small values usually decrease compression ratio.
-                          * Must be clamped between ZSTD_LDM_MINMATCH_MIN
-                          * and ZSTD_LDM_MINMATCH_MAX (default: 64). */
-    ZSTD_p_ldmBucketSizeLog,  </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
-                               * Larger values usually improve collision resolution but may decrease
-                               * compression speed.
-                               * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX (default: 3). */
+    ZSTD_p_ldmHashLog,       </b>/* Size of the table for long distance matching, as a power of 2.<b>
+                              * Larger values increase memory usage and compression ratio, but decrease
+                              * compression speed.
+                              * Must be clamped between ZSTD_HASHLOG_MIN and ZSTD_HASHLOG_MAX
+                              * (default: windowlog - 7).
+                              * Special: value 0 means "do not change ldmHashLog". */
+    ZSTD_p_ldmMinMatch,      </b>/* Minimum size of searched matches for long distance matcher.<b>
+                              * Larger/too small values usually decrease compression ratio.
+                              * Must be clamped between ZSTD_LDM_MINMATCH_MIN
+                              * and ZSTD_LDM_MINMATCH_MAX (default: 64).
+                              * Special: value 0 means "do not change ldmMinMatch". */
+    ZSTD_p_ldmBucketSizeLog, </b>/* Log size of each bucket in the LDM hash table for collision resolution.<b>
+                              * Larger values usually improve collision resolution but may decrease
+                              * compression speed.
+                              * The maximum value is ZSTD_LDM_BUCKETSIZELOG_MAX (default: 3).
+                              * note : 0 is a valid value */
     ZSTD_p_ldmHashEveryLog,  </b>/* Frequency of inserting/looking up entries in the LDM hash table.<b>
                               * The default is MAX(0, (windowLog - ldmHashLog)) to
                               * optimize hash table usage.
                               * Larger values improve compression speed. Deviating far from the
                               * default value will likely result in a decrease in compression ratio.
-                              * Must be clamped between 0 and ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN. */
+                              * Must be clamped between 0 and ZSTD_WINDOWLOG_MAX - ZSTD_HASHLOG_MIN.
+                              * note : 0 is a valid value */
 
 } ZSTD_cParameter;
 </b></pre><BR>
@@ -1000,7 +997,7 @@ size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t
 </p></pre><BR>
 
 <pre><b>size_t ZSTD_resetCCtxParams(ZSTD_CCtx_params* params);
-</b><p>  Reset params to default, with the default compression level.
+</b><p>  Reset params to default values.
  
 </p></pre><BR>
 
@@ -1030,7 +1027,7 @@ size_t ZSTD_CCtx_refPrefix_advanced(ZSTD_CCtx* cctx, const void* prefix, size_t
 </b><p>  Apply a set of ZSTD_CCtx_params to the compression context.
   This must be done before the dictionary is loaded.
   The pledgedSrcSize is treated as unknown.
-  Multithreading parameters are applied only if nbThreads > 1.
+  Multithreading parameters are applied only if nbWorkers >= 1.
  
 </p></pre><BR>