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utils: Helper macros to define overloaded macros based on number of arguments

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This commit is contained in:
Tobias Brunner 2014-06-25 17:44:14 +02:00
parent ba2805c106
commit e79dbda390
1 changed files with 26 additions and 0 deletions
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src/libstrongswan/utils/utils.h
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@ -277,6 +277,32 @@ static inline void *memset_noop(void *s, int c, size_t n)
static typeof(_cb_##name) *name = (typeof(_cb_##name)*)_cb_##name; \
static ret _cb_##name(param1, ##__VA_ARGS__)
/**
* This macro allows counting the number of arguments passed to a macro.
* Combined with the VA_ARGS_DISPATCH() macro this can be used to implement
* macro overloading based on the number of arguments.
* 0 to 10 arguments are currently supported.
*/
#define VA_ARGS_NUM(...) _VA_ARGS_NUM(0,##__VA_ARGS__,10,9,8,7,6,5,4,3,2,1,0)
#define _VA_ARGS_NUM(_0,_1,_2,_3,_4,_5,_6,_7,_8,_9,_10,NUM,...) NUM
/**
* This macro can be used to dispatch a macro call based on the number of given
* arguments, for instance:
*
* @code
* #define MY_MACRO(...) VA_ARGS_DISPATCH(MY_MACRO, __VA_ARGS__)(__VA_ARGS__)
* #define MY_MACRO1(arg) one_arg(arg)
* #define MY_MACRO2(arg1,arg2) two_args(arg1,arg2)
* @endcode
*
* MY_MACRO() can now be called with either one or two arguments, which will
* resolve to one_arg(arg) or two_args(arg1,arg2), respectively.
*/
#define VA_ARGS_DISPATCH(func, ...) _VA_ARGS_DISPATCH(func, VA_ARGS_NUM(__VA_ARGS__))
#define _VA_ARGS_DISPATCH(func, num) __VA_ARGS_DISPATCH(func, num)
#define __VA_ARGS_DISPATCH(func, num) func ## num
/**
* Architecture independent bitfield definition helpers (at least with GCC).
*