c/c++:for each遍历 __VA_ARGS__ 中的每一个元素

╰+攻爆jí腚メ 2022-05-21 20:09 115阅读 0赞

因为项目需要，要大量定义类似的枚举类型。

typedef enum test{
    	test_1,test_2,test3....
    }test;

手工写实在太多了，而且容易出错，于考虑用可变参数宏:`__VA_ARGS__` 来实现，关键就是要实现对`__VA_ARGS__`中每个参数元素的遍历。  
下面是现实代码，真正调用的宏只有一个`FL_FOREACH`，  
`FL_FOREACH`实现对`__VA_ARGS__`中的每个参数执行指定的函数宏`fun`，`fun`允许有一个外部输入参数`funarg`  
类似于C++11 STL库中的`for_each`函数

> 代码中用到的`FL_ARG_COUNT`宏参见前一篇博客[《c/c++:计算可变参数宏 `__VA_ARGS__` 的参数个数》][c_c_ _VA_ARGS_]

// 参数拼接
    #define FL_CONCAT_(l, r) l ## r
    
    #define FL_CONCAT(l, r) FL_CONCAT_(l, r)
    
    #define FL_DOARG0(s,f,a,o)
    #define FL_DOARG1(s,f,a,v,...) f(a,v)
    #define FL_DOARG2(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG1(s,f,a,__VA_ARGS__)
    #define FL_DOARG3(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG2(s,f,a,__VA_ARGS__)
    #define FL_DOARG4(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG3(s,f,a,__VA_ARGS__)
    #define FL_DOARG5(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG4(s,f,a,__VA_ARGS__)
    #define FL_DOARG6(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG5(s,f,a,__VA_ARGS__)
    #define FL_DOARG7(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG6(s,f,a,__VA_ARGS__)
    #define FL_DOARG8(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG7(s,f,a,__VA_ARGS__)
    #define FL_DOARG9(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG8(s,f,a,__VA_ARGS__)
    #define FL_DOARG10(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG9(s,f,a,__VA_ARGS__)
    #define FL_DOARG11(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG10(s,f,a,__VA_ARGS__)
    #define FL_DOARG12(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG11(s,f,a,__VA_ARGS__)
    #define FL_DOARG13(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG12(s,f,a,__VA_ARGS__)
    #define FL_DOARG14(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG13(s,f,a,__VA_ARGS__)
    #define FL_DOARG15(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG14(s,f,a,__VA_ARGS__)
    #define FL_DOARG16(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG15(s,f,a,__VA_ARGS__)
    #define FL_DOARG17(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG16(s,f,a,__VA_ARGS__)
    #define FL_DOARG18(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG17(s,f,a,__VA_ARGS__)
    #define FL_DOARG19(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG18(s,f,a,__VA_ARGS__)
    #define FL_DOARG20(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG19(s,f,a,__VA_ARGS__)
    #define FL_DOARG21(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG20(s,f,a,__VA_ARGS__)
    #define FL_DOARG22(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG21(s,f,a,__VA_ARGS__)
    #define FL_DOARG23(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG22(s,f,a,__VA_ARGS__)
    #define FL_DOARG24(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG23(s,f,a,__VA_ARGS__)
    #define FL_DOARG25(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG24(s,f,a,__VA_ARGS__)
    #define FL_DOARG26(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG25(s,f,a,__VA_ARGS__)
    #define FL_DOARG27(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG26(s,f,a,__VA_ARGS__)
    #define FL_DOARG28(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG27(s,f,a,__VA_ARGS__)
    #define FL_DOARG29(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG28(s,f,a,__VA_ARGS__)
    #define FL_DOARG30(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG29(s,f,a,__VA_ARGS__)
    #define FL_DOARG31(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG30(s,f,a,__VA_ARGS__)
    #define FL_DOARG32(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG31(s,f,a,__VA_ARGS__)
    #define FL_DOARG33(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG32(s,f,a,__VA_ARGS__)
    #define FL_DOARG34(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG33(s,f,a,__VA_ARGS__)
    #define FL_DOARG35(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG34(s,f,a,__VA_ARGS__)
    #define FL_DOARG36(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG35(s,f,a,__VA_ARGS__)
    #define FL_DOARG37(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG36(s,f,a,__VA_ARGS__)
    #define FL_DOARG38(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG37(s,f,a,__VA_ARGS__)
    #define FL_DOARG39(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG38(s,f,a,__VA_ARGS__)
    #define FL_DOARG40(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG39(s,f,a,__VA_ARGS__)
    #define FL_DOARG41(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG40(s,f,a,__VA_ARGS__)
    #define FL_DOARG42(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG41(s,f,a,__VA_ARGS__)
    #define FL_DOARG43(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG42(s,f,a,__VA_ARGS__)
    #define FL_DOARG44(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG43(s,f,a,__VA_ARGS__)
    #define FL_DOARG45(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG44(s,f,a,__VA_ARGS__)
    #define FL_DOARG46(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG45(s,f,a,__VA_ARGS__)
    #define FL_DOARG47(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG46(s,f,a,__VA_ARGS__)
    #define FL_DOARG48(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG47(s,f,a,__VA_ARGS__)
    #define FL_DOARG49(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG48(s,f,a,__VA_ARGS__)
    #define FL_DOARG50(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG49(s,f,a,__VA_ARGS__)
    #define FL_DOARG51(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG50(s,f,a,__VA_ARGS__)
    #define FL_DOARG52(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG51(s,f,a,__VA_ARGS__)
    #define FL_DOARG53(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG52(s,f,a,__VA_ARGS__)
    #define FL_DOARG54(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG53(s,f,a,__VA_ARGS__)
    #define FL_DOARG55(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG54(s,f,a,__VA_ARGS__)
    #define FL_DOARG56(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG55(s,f,a,__VA_ARGS__)
    #define FL_DOARG57(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG56(s,f,a,__VA_ARGS__)
    #define FL_DOARG58(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG57(s,f,a,__VA_ARGS__)
    #define FL_DOARG59(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG58(s,f,a,__VA_ARGS__)
    #define FL_DOARG60(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG59(s,f,a,__VA_ARGS__)
    #define FL_DOARG61(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG60(s,f,a,__VA_ARGS__)
    #define FL_DOARG62(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG61(s,f,a,__VA_ARGS__)
    #define FL_DOARG63(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG62(s,f,a,__VA_ARGS__)
    #define FL_DOARG64(s,f,a,v,...) FL_DOARG1(s,f,a,v) s FL_DOARG63(s,f,a,__VA_ARGS__)
    
    #define FL_FOREACH_(sepatator,fun,funarg,...) \
    		FL_CONCAT(FL_DOARG,FL_ARG_COUNT(__VA_ARGS__))(sepatator,fun,funarg,__VA_ARGS__)
    #define FL_FOREACH(sepatator,fun,funarg,...) \
    		FL_FOREACH_(sepatator,fun,funarg,__VA_ARGS__)
    // 为动态参数 __VA_ARGS__ 每一个参数调用 fun 宏,最大支持64个参数
    // sepatator 分隔符
    // fun 函数宏
    // funarg 函数宏的参数

有了`FL_FOREACH`，就可以实现前述的需求了：

#define enum_elem(p,n) p##n,
    
    // 定义一个名为clsName的枚举类型,动态参数提供枚举类型的元素，最多支持64个元素
    // clsName##_为元素名前缀
    #define FL_DEF_ENUM(clsName,...)\
    enum _##clsName{\
    FL_FOREACH(,enum_elem,clsName##_,__VA_ARGS__)\
    	/* must be last position,for competing enum's number  */\
    	clsName##_LAST_ID \
    }clsName;

调用示例：

// 定义4个元素
    FL_DEF_ENUM(FL_TEST0, 0, 1, 2, 4)

宏展开代码 (eclipse视图)：  
![这里写图片描述][70]

// 定义10个元素
    FL_DEF_ENUM(FL_TEST, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9)
    
    // 最大64个
    FL_DEF_ENUM(FL_TEST2,\
    		 0, 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\
    		)

`FL_TEST`类型(eclipse视图)  
![这里写图片描述][70 1]

[c_c_ _VA_ARGS_]: https://blog.csdn.net/10km/article/details/80760533
[70]: /images/20220522/64c4553ff80d41769b191ef44d257462.png
[70 1]: /images/20220522/9d8a4914c7374d629a24e31c06aff68c.png