品网站建设公司排名,做推广便宜的网站,经典网站欣赏、,wordpress国外付费主题下载文章目录 功能说明实现示例解析扩展 功能说明
宏检验条件是否成立#xff0c;并返回指定的值
#define TU_VERIFY(...) _GET_3RD_ARG(__VA_ARGS__, TU_VERIFY_2ARGS, TU_VERIFY_1ARGS, UNUSED)(__VA_ARGS__)TU_VERIFY(1) 检验为真#xff0c;啥也不干TU_VERIFY(0) 校验为假并返回指定的值
#define TU_VERIFY(...) _GET_3RD_ARG(__VA_ARGS__, TU_VERIFY_2ARGS, TU_VERIFY_1ARGS, UNUSED)(__VA_ARGS__)TU_VERIFY(1) 检验为真啥也不干TU_VERIFY(0) 校验为假函数返回返回值为 falseTU_VERIFY(87, 1) 检验为真啥也不干TU_VERIFY(0, 100) 检验为假函数返回返回值为 100
实现
// Helper to implement optional parameter for TU_VERIFY Macro family
#define _GET_3RD_ARG(arg1, arg2, arg3, ...) arg3
#define _GET_4TH_ARG(arg1, arg2, arg3, arg4, ...) arg4/*------------- Generator for TU_VERIFY and TU_VERIFY_HDLR -------------*/
#define TU_VERIFY_DEFINE(_cond, _handler, _ret) do \
{ \if ( !(_cond) ) { _handler; return _ret; } \
} while(0)/*------------------------------------------------------------------*/
/* TU_VERIFY* - TU_VERIFY_1ARGS : return false if failed* - TU_VERIFY_2ARGS : return provided value if failed*------------------------------------------------------------------*/
#define TU_VERIFY_1ARGS(_cond) TU_VERIFY_DEFINE(_cond, , false)
#define TU_VERIFY_2ARGS(_cond, _ret) TU_VERIFY_DEFINE(_cond, , _ret)#define TU_VERIFY(...) _GET_3RD_ARG(__VA_ARGS__, TU_VERIFY_2ARGS, TU_VERIFY_1ARGS, UNUSED)(__VA_ARGS__)示例
#include stdio.h
#include stdbool.h// Helper to implement optional parameter for TU_VERIFY Macro family
#define _GET_3RD_ARG(arg1, arg2, arg3, ...) arg3
#define _GET_4TH_ARG(arg1, arg2, arg3, arg4, ...) arg4/*------------- Generator for TU_VERIFY and TU_VERIFY_HDLR -------------*/
#define TU_VERIFY_DEFINE(_cond, _handler, _ret) \do \{ \if (!(_cond)) \{ \_handler; \return _ret; \} \} while (0)/*------------------------------------------------------------------*/
/* TU_VERIFY* - TU_VERIFY_1ARGS : return false if failed* - TU_VERIFY_2ARGS : return provided value if failed*------------------------------------------------------------------*/
#define TU_VERIFY_1ARGS(_cond) TU_VERIFY_DEFINE(_cond, , false)
#define TU_VERIFY_2ARGS(_cond, _ret) TU_VERIFY_DEFINE(_cond, , _ret)#define TU_VERIFY(...) _GET_3RD_ARG(__VA_ARGS__, TU_VERIFY_2ARGS, TU_VERIFY_1ARGS, UNUSED)(__VA_ARGS__)static int verify_func(int cond, int value)
{TU_VERIFY(cond, value);return 0xa5;
}int main(int argc, char *argv[])
{printf(%x \r\n, verify_func(87, 1));printf(%x \r\n, verify_func(0, 100));return 0;
}结果打印
a5
64解析
该宏最少传入一个参数最多传入两个参数__VA_ARGS__ 可以理解为占位符当只有一个参数时该宏展开为 _GET_3RD_ARG(xxx, TU_VERIFY_2ARGS, TU_VERIFY_1ARGS, UNUSED) 得到的就是 TU_VERIFY_1ARGS所以执行的就是 TU_VERIFY_1ARGS(xxx)当有两个参数时该宏展开为 _GET_3RD_ARG(xxx, yyy, TU_VERIFY_2ARGS, TU_VERIFY_1ARGS, UNUSED) 得到的就是 TU_VERIFY_2ARGS所以执行的就是 TU_VERIFY_2ARGS(xxx, yyy)
扩展
带 handler 处理的功能
/*------------------------------------------------------------------*/
/* TU_VERIFY WITH HANDLER* - TU_VERIFY_HDLR_2ARGS : execute handler, return false if failed* - TU_VERIFY_HDLR_3ARGS : execute handler, return provided error if failed*------------------------------------------------------------------*/
#define TU_VERIFY_HDLR_2ARGS(_cond, _handler) TU_VERIFY_DEFINE(_cond, _handler, false)
#define TU_VERIFY_HDLR_3ARGS(_cond, _handler, _ret) TU_VERIFY_DEFINE(_cond, _handler, _ret)#define TU_VERIFY_HDLR(...) _GET_4TH_ARG(__VA_ARGS__, TU_VERIFY_HDLR_3ARGS, TU_VERIFY_HDLR_2ARGS,UNUSED)(__VA_ARGS__)该宏最少传入两个参数最多传入三个参数__VA_ARGS__ 可以理解为占位符当只有一个参数时该宏展开为 _GET_4TH_ARG(xxx, yyy, TU_VERIFY_HDLR_3ARGS, TU_VERIFY_HDLR_2ARGS, UNUSED) 得到的就是 TU_VERIFY_HDLR_2ARGS所以执行的就是 TU_VERIFY_HDLR_2ARGS(xxx, yyy)当有三个参数时该宏展开为 _GET_4TH_ARG(xxx, yyy, zzz, TU_VERIFY_HDLR_3ARGS, TU_VERIFY_HDLR_2ARGS, UNUSED) 得到的就是 TU_VERIFY_HDLR_3ARGS所以执行的就是 TU_VERIFY_HDLR_3ARGS(xxx, yyy, zzz)
