packed_ptr_fwd.h

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#pragma once
 
#include <cstddef>
#include <type_traits>
 
namespace ktl
{
    namespace detail
    {
        template<typename T>
        constexpr T min_range(size_t bits)
        {
            if constexpr (std::is_unsigned_v<T> || std::is_enum_v<T>)
                return static_cast<T>(0ULL);
            else
                return static_cast<T>(-(1LL << (bits - 1LL)));
        }
 
        template<typename T>
        constexpr T max_range(size_t bits)
        {
            if constexpr (std::is_unsigned_v<T> || std::is_enum_v<T>)
                return static_cast<T>((1ULL << bits) - 1ULL);
            else
                return static_cast<T>(((1LL << bits) - 1LL) - (1LL << (bits - 1LL)));
        }
 
 
        // Function pointer types
        template<typename T, typename = void>
        struct is_function_pointer : std::false_type {};
 
        template<typename R, typename... Ts>
        struct is_function_pointer<R(*)(Ts...), std::void_t<R(*)(Ts...)>> : std::true_type {};
 
        template<typename T>
        constexpr bool is_function_pointer_v = is_function_pointer<T>::value;
 
 
        // Get underlying type for alignment
        template<typename T, typename = void>
        struct underlying_type
        {
            using type = T;
        };
 
        // Enum types
        template<typename T>
        struct underlying_type<T, std::enable_if_t<std::is_enum_v<T>>>
        {
            using type = std::underlying_type_t<T>;
        };
 
        // Pointer types, but not function pointers
        template<typename T>
        struct underlying_type<T, std::enable_if_t<std::is_pointer_v<T> && !is_function_pointer_v<T>>>
        {
            using type = std::remove_pointer_t<T>;
        };
 
        template<typename T>
        using underlying_type_t = typename underlying_type<T>::type;
    }
 
    template<
        typename PtrT,
        typename IntT,
        IntT Min = detail::min_range<IntT>(detail::log2(alignof(detail::underlying_type_t<PtrT>))),
        IntT Max = detail::max_range<IntT>(detail::log2(alignof(detail::underlying_type_t<PtrT>))),
        size_t Alignment = alignof(detail::underlying_type_t<PtrT>)>
    class packed_ptr;
}