lokinet/llarp/util/meta/memfn_traits.hpp
2019-09-03 20:52:28 +01:00

108 lines
3.2 KiB
C++

#ifndef LLARP_UTIL_MEMFN_TRAITS
#define LLARP_UTIL_MEMFN_TRAITS
#include <util/meta/object.hpp>
#include <util/meta/traits.hpp>
#include <functional>
#include <utility>
namespace llarp
{
namespace util
{
template < typename Prototype, typename TestPrototype >
struct MemFnTraitsImpl;
template < typename Prototype >
struct MemFnTraits : public MemFnTraitsImpl< Prototype, Prototype >
{
};
template < typename Prototype, typename Return, typename Type,
typename... Args >
class MemFnTraitsClass
{
using NonCVTag = traits::Tag< 0 >;
using ConstTag = traits::Tag< 1 >;
using VolTag = traits::Tag< 2 >;
using ConstVolTag = traits::Tag< 3 >;
// clang-format off
static constexpr NonCVTag test(Return (Type::*)(Args...));
static constexpr ConstTag test(Return (Type::*)(Args...) const);
static constexpr VolTag test(Return (Type::*)(Args...) volatile);
static constexpr ConstVolTag test(Return (Type::*)(Args...) const volatile);
// clang-format on
public:
static constexpr bool IsConst =
((sizeof((test)((Prototype)0)) - 1) & 1) != 0;
static constexpr bool IsVolatile =
((sizeof((test)((Prototype)0)) - 1) & 2) != 0;
using ctype = std::conditional_t< IsConst, const Type, Type >;
using type = std::conditional_t< IsVolatile, volatile ctype, ctype >;
};
template < typename Prototype, typename Return, typename Type,
typename... Args >
struct MemFnTraitsImpl< Prototype, Return (Type::*)(Args...) >
{
static constexpr bool IsMemFn = true;
using class_type =
typename MemFnTraitsClass< Prototype, Return, Type, Args... >::type;
using result_type = Return;
};
template < typename Prototype, typename Return, typename Type,
typename... Args >
struct MemFnTraitsImpl< Prototype, Return (Type::*)(Args...) const >
{
static constexpr bool IsMemFn = true;
using class_type =
typename MemFnTraitsClass< Prototype, Return, Type, Args... >::type;
using result_type = Return;
};
template < typename Prototype, typename Return, typename Type,
typename... Args >
struct MemFnTraitsImpl< Prototype, Return (Type::*)(Args...) volatile >
{
static constexpr bool IsMemFn = true;
using class_type =
typename MemFnTraitsClass< Prototype, Return, Type, Args... >::type;
using result_type = Return;
};
template < typename Prototype, typename Return, typename Type,
typename... Args >
struct MemFnTraitsImpl< Prototype,
Return (Type::*)(Args...) const volatile >
{
static constexpr bool IsMemFn = true;
using class_type =
typename MemFnTraitsClass< Prototype, Return, Type, Args... >::type;
using result_type = Return;
};
template < typename Prototype, typename TestPrototype >
struct MemFnTraitsImpl
{
static constexpr bool IsMemFn = false;
using result_type = void;
using class_type = void;
};
} // namespace util
} // namespace llarp
#endif