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