Older/ToolKit/Util/function_traits.h
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add ZLMediaKit code for learning.
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C++

#ifndef SRC_UTIL_FUNCTION_TRAITS_H_
#define SRC_UTIL_FUNCTION_TRAITS_H_
#include <tuple>
#include <functional>
namespace toolkit {
template<typename T>
struct function_traits;
//普通函数
template<typename Ret, typename... Args>
struct function_traits<Ret(Args...)>
{
public:
enum { arity = sizeof...(Args) };
typedef Ret function_type(Args...);
typedef Ret return_type;
using stl_function_type = std::function<function_type>;
typedef Ret(*pointer)(Args...);
template<size_t I>
struct args
{
static_assert(I < arity, "index is out of range, index must less than sizeof Args");
using type = typename std::tuple_element<I, std::tuple<Args...> >::type;
};
};
//函数指针
template<typename Ret, typename... Args>
struct function_traits<Ret(*)(Args...)> : function_traits<Ret(Args...)>{};
//std::function
template <typename Ret, typename... Args>
struct function_traits<std::function<Ret(Args...)>> : function_traits<Ret(Args...)>{};
//member function
#define FUNCTION_TRAITS(...) \
template <typename ReturnType, typename ClassType, typename... Args>\
struct function_traits<ReturnType(ClassType::*)(Args...) __VA_ARGS__> : function_traits<ReturnType(Args...)>{}; \
FUNCTION_TRAITS()
FUNCTION_TRAITS(const)
FUNCTION_TRAITS(volatile)
FUNCTION_TRAITS(const volatile)
//函数对象
template<typename Callable>
struct function_traits : function_traits<decltype(&Callable::operator())>{};
} /* namespace toolkit */
#endif /* SRC_UTIL_FUNCTION_TRAITS_H_ */