common/macro_trick.h

/******************************************************************************
 * @file     macro_trick.h
 *
 * @brief    for TLSR chips
 *
 * @author   public@telink-semi.com;
 * @date     Sep. 30, 2010
 *
 * @attention
 *
 *  Copyright (C) 2019-2020 Telink Semiconductor (Shanghai) Co., Ltd.
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 *
 *****************************************************************************/

#pragma once

/////////////////  variadic macro  ////////////////////////

#if 1
// a little more complex version that works with GCC and visual studio

///   http://stackoverflow.com/questions/9183993/msvc-variadic-macro-expansion
#define COUNT_ARGS_IMPL2(_1, _2, _3, _4, _5, _6, _7, _8 , _9, _10, _11, _12, _13, _14, _15, _16, _17, _18, _19, _20, N, ...) N
#define COUNT_ARGS_IMPL(args)   COUNT_ARGS_IMPL2 args
#define COUNT_ARGS(...)            COUNT_ARGS_IMPL((__VA_ARGS__, 20, 19, 18, 17, 16, 15, 14, 13, 12, 11, 10, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0))

#define MACRO_CHOOSE_HELPER2(base, count)     base##count
#define MACRO_CHOOSE_HELPER1(base, count)     MACRO_CHOOSE_HELPER2(base, count)
#define MACRO_CHOOSE_HELPER(base, count)     MACRO_CHOOSE_HELPER1(base, count)

#define MACRO_GLUE(x, y) x y
#define VARARG(base, ...)                    MACRO_GLUE(MACRO_CHOOSE_HELPER(base, COUNT_ARGS(__VA_ARGS__)),(__VA_ARGS__))
// usage
/*
    #define  fun1(a)        xxxx
    #define  fun2(a, b)        xxxx
    #define  fun3(a, b, c)    xxxx

    #define fun(...)        VARARG(fun,  __VA_ARGS__)

    int main(){
        fun(1);            // calls fun1(1)
        fun(1, 2);            // calls fun2(1,2)
        fun(1, 2, 3);        // calls fun3(1,2,3)
    }

*/


#else
// a concise version that only works with GCC

///   http://stackoverflow.com/questions/2124339/c-preprocessor-va-args-number-of-arguments

#define VA_NARGS_IMPL(_1, _2, _3, _4, _5, _6, _7, _8 , _9, _10, N, ...) N
#define VA_NARGS(...) VA_NARGS_IMPL(X,##__VA_ARGS__, 9, 8, 7, 6, 5, 4, 3, 2, 1, 0)
#define VARARG_IMPL2(base, count, ...) base##count(__VA_ARGS__)
#define VARARG_IMPL(base, count, ...) VARARG_IMPL2(base, count, __VA_ARGS__)
#define VARARG(base, ...) VARARG_IMPL(base, VA_NARGS(__VA_ARGS__), __VA_ARGS__)

#endif
// #define NUMARGS(...)  (sizeof((int[]){__VA_ARGS__})/sizeof(int))

/////////////////  end of variadic macro  //////////////////////