function.h

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#ifndef CPPCOMMON_FUNCTION_H
#define CPPCOMMON_FUNCTION_H
 
#include <functional>
#include <memory>
 
namespace CppCommon {

template <class, size_t Capacity = 1024>
class Function;


template <class R, class... Args, size_t Capacity>
class Function<R(Args...), Capacity>
{
public:
    Function() noexcept;
    Function(std::nullptr_t) noexcept;
    Function(const Function& function) noexcept;
    Function(Function&& function) noexcept;
    template <class TFunction>
    Function(TFunction&& function) noexcept;
    ~Function() noexcept;
 
    Function& operator=(std::nullptr_t) noexcept;
    Function& operator=(const Function& function) noexcept;
    Function& operator=(Function&& function) noexcept;
    template <typename TFunction>
    Function& operator=(TFunction&& function) noexcept;
    template <typename TFunction>
    Function& operator=(std::reference_wrapper<TFunction> function) noexcept;

    explicit operator bool() const noexcept { return (_manager != nullptr); }

    R operator()(Args... args);

    void swap(Function& function) noexcept;
    template <class UR, class... UArgs, size_t UCapacity>
    friend void swap(Function<UR(UArgs...), UCapacity>& function1, Function<UR(UArgs...), UCapacity>& function2) noexcept;
 
private:
    enum class Operation { Clone, Destroy };
 
    using Invoker = R (*)(void*, Args&&...);
    using Manager = void (*)(void*, void*, Operation);
 
    static const size_t StorageSize = Capacity - sizeof(Invoker) - sizeof(Manager);
    static const size_t StorageAlign = 8;
 
    alignas(StorageAlign) std::byte _data[StorageSize];
    Invoker _invoker;
    Manager _manager;
 
    template <typename TFunction>
    static R Invoke(void* data, Args&&... args) noexcept;
 
    template <typename TFunction>
    static void Manage(void* dst, void* src, Operation op) noexcept;
};

 
} // namespace CppCommon
 
#include "function.inl"
 
#endif // CPPCOMMON_FUNCTION_H