Add ZSTD_defaultCLevel() function to public API

lib/compress/zstd_compress.c

@@ -5054,6 +5054,7 @@ size_t ZSTD_endStream(ZSTD_CStream* zcs, ZSTD_outBuffer* output)
 #define ZSTD_MAX_CLEVEL     22
 int ZSTD_maxCLevel(void) { return ZSTD_MAX_CLEVEL; }
 int ZSTD_minCLevel(void) { return (int)-ZSTD_TARGETLENGTH_MAX; }
+int ZSTD_defaultCLevel(void) { return ZSTD_CLEVEL_DEFAULT; }
 
 static const ZSTD_compressionParameters ZSTD_defaultCParameters[4][ZSTD_MAX_CLEVEL+1] = {
 {   /* "default" - for any srcSize > 256 KB */

lib/zstd.h

@@ -1918,6 +1918,10 @@ ZSTDLIB_API size_t ZSTD_compressStream2_simpleArgs (
                       const void* src, size_t srcSize, size_t* srcPos,
                             ZSTD_EndDirective endOp);
 
+/*! ZSTD_defaultCLevel() :
+ * Returns the default compression level, specified by ZSTD_CLEVEL_DEFAULT
+ */
+ZSTDLIB_API int ZSTD_defaultCLevel(void);
 
 /***************************************
 *  Advanced decompression functions