// Copyright 2019 Hans Dembinski // // Distributed under the Boost Software License, Version 1.0. // (See accompanying file LICENSE_1_0.txt // or copy at http://www.boost.org/LICENSE_1_0.txt) #ifndef BOOST_HISTOGRAM_DETAIL_TRY_CAST_HPP #define BOOST_HISTOGRAM_DETAIL_TRY_CAST_HPP #include <boost/config.hpp> // BOOST_NORETURN #include <boost/throw_exception.hpp> #include <type_traits> namespace boost { namespace histogram { namespace detail { template <class T, class U> constexpr T* ptr_cast(U*) noexcept { return nullptr; } template <class T> constexpr T* ptr_cast(T* p) noexcept { return p; } template <class T> constexpr const T* ptr_cast(const T* p) noexcept { return p; } template <class T, class E, class U> BOOST_NORETURN T try_cast_impl(std::false_type, std::false_type, U&&) { BOOST_THROW_EXCEPTION(E("type cast error")); } // converting cast template <class T, class E, class U> T try_cast_impl(std::false_type, std::true_type, U&& u) noexcept { return static_cast<T>(u); // cast to avoid warnings } // pass-through cast template <class T, class E> T&& try_cast_impl(std::true_type, std::true_type, T&& t) noexcept { return std::forward<T>(t); } // cast fails at runtime with exception E instead of compile-time, T must be a value template <class T, class E, class U> T try_cast(U&& u) noexcept(std::is_convertible<U, T>::value) { return try_cast_impl<T, E>(std::is_same<U, T>{}, std::is_convertible<U, T>{}, std::forward<U>(u)); } } // namespace detail } // namespace histogram } // namespace boost #endif