clean up

src/common/tusb_common.h

@@ -102,6 +102,37 @@
 #define __be2n_16(u16)  __n2be_16(u16)
 #endif
 
+
+/*------------------------------------------------------------------*/
+/* Count number of arguments of __VA_ARGS__
+ * - reference https://groups.google.com/forum/#!topic/comp.std.c/d-6Mj5Lko_s
+ * - _GET_NTH_ARG() takes args >= N (64) but only expand to Nth one (64th)
+ * - _RSEQ_N() is reverse sequential to N to add padding to have
+ * Nth position is the same as the number of arguments
+ * - ##__VA_ARGS__ is used to deal with 0 paramerter (swallows comma)
+ *------------------------------------------------------------------*/
+#ifndef VA_ARGS_NUM_
+
+#define VA_ARGS_NUM_(...) 	 NARG_(_0, ##__VA_ARGS__,_RSEQ_N())
+#define NARG_(...)        _GET_NTH_ARG(__VA_ARGS__)
+#define _GET_NTH_ARG( \
+          _1, _2, _3, _4, _5, _6, _7, _8, _9,_10, \
+         _11,_12,_13,_14,_15,_16,_17,_18,_19,_20, \
+         _21,_22,_23,_24,_25,_26,_27,_28,_29,_30, \
+         _31,_32,_33,_34,_35,_36,_37,_38,_39,_40, \
+         _41,_42,_43,_44,_45,_46,_47,_48,_49,_50, \
+         _51,_52,_53,_54,_55,_56,_57,_58,_59,_60, \
+         _61,_62,_63,N,...) N
+#define _RSEQ_N() \
+         62,61,60,                      \
+         59,58,57,56,55,54,53,52,51,50, \
+         49,48,47,46,45,44,43,42,41,40, \
+         39,38,37,36,35,34,33,32,31,30, \
+         29,28,27,26,25,24,23,22,21,20, \
+         19,18,17,16,15,14,13,12,11,10, \
+         9,8,7,6,5,4,3,2,1,0
+#endif
+
 //--------------------------------------------------------------------+
 // INLINE FUNCTION
 //--------------------------------------------------------------------+