Merge branch 'dev' into constCDict

lib/zstd.h

@@ -974,10 +974,20 @@ typedef enum {
     ZSTD_p_dictIDFlag,       /* When applicable, dictionary's ID is written into frame header (default:1) */
 
     /* multi-threading parameters */
+    /* These parameters are only useful if multi-threading is enabled (ZSTD_MULTITHREAD).
+     * They return an error otherwise. */
     ZSTD_p_nbThreads=400,    /* Select how many threads a compression job can spawn (default:1)
                               * 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,  /* Single thread mode is by default "blocking" :
+                              * 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. */
     ZSTD_p_jobSize,          /* Size of a compression job. This value is only enforced in streaming (non-blocking) mode.
                               * 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.