function_ref.hpp

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#pragma once

 
#include <functional>
#include <memory>
#include <type_traits>
#include <utility>
 
namespace orrery::core {
 
template<typename Signature> class FunctionRef;

template<typename Result, typename... Args> class FunctionRef<Result(Args...)> {
public:
    template<typename Callable, typename Erased = std::remove_reference_t<Callable>>
        requires(!std::is_same_v<Erased, FunctionRef> && !std::is_const_v<Erased> &&
                 std::is_invocable_r_v<Result, Erased&, Args...>)
    // NOLINTNEXTLINE(bugprone-forwarding-reference-overload,cppcoreguidelines-missing-std-forward)
    constexpr FunctionRef(Callable&& callable) noexcept
        : object_(std::addressof(callable)), invoke_(&invoke_erased<Erased>) {}
 
    constexpr Result operator()(Args... args) const {
        return invoke_(object_, std::forward<Args>(args)...);
    }
 
private:
    template<typename Erased> static Result invoke_erased(void* object, Args... args) {
        return std::invoke(*static_cast<Erased*>(object), std::forward<Args>(args)...);
    }
 
    void* object_;
    Result (*invoke_)(void*, Args...);
};
 
} // namespace orrery::core