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편집 파일: associated_allocator.hpp

// // associated_allocator.hpp // ~~~~~~~~~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2024 Christopher M. Kohlhoff (chris at kohlhoff dot com) // // 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_ASIO_ASSOCIATED_ALLOCATOR_HPP #define BOOST_ASIO_ASSOCIATED_ALLOCATOR_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include <boost/asio/detail/config.hpp> #include <memory> #include <boost/asio/associator.hpp> #include <boost/asio/detail/functional.hpp> #include <boost/asio/detail/type_traits.hpp> #include <boost/asio/detail/push_options.hpp> namespace boost { namespace asio { template <typename T, typename Allocator> struct associated_allocator; namespace detail { template <typename T, typename = void> struct has_allocator_type : false_type { }; template <typename T> struct has_allocator_type<T, void_t<typename T::allocator_type>> : true_type { }; template <typename T, typename A, typename = void, typename = void> struct associated_allocator_impl { typedef void asio_associated_allocator_is_unspecialised; typedef A type; static type get(const T&) noexcept { return type(); } static const type& get(const T&, const A& a) noexcept { return a; } }; template <typename T, typename A> struct associated_allocator_impl<T, A, void_t<typename T::allocator_type>> { typedef typename T::allocator_type type; static auto get(const T& t) noexcept -> decltype(t.get_allocator()) { return t.get_allocator(); } static auto get(const T& t, const A&) noexcept -> decltype(t.get_allocator()) { return t.get_allocator(); } }; template <typename T, typename A> struct associated_allocator_impl<T, A, enable_if_t< !has_allocator_type<T>::value >, void_t< typename associator<associated_allocator, T, A>::type >> : associator<associated_allocator, T, A> { }; } // namespace detail /// Traits type used to obtain the allocator associated with an object. /** * A program may specialise this traits type if the @c T template parameter in * the specialisation is a user-defined type. The template parameter @c * Allocator shall be a type meeting the Allocator requirements. * * Specialisations shall meet the following requirements, where @c t is a const * reference to an object of type @c T, and @c a is an object of type @c * Allocator. * * @li Provide a nested typedef @c type that identifies a type meeting the * Allocator requirements. * * @li Provide a noexcept static member function named @c get, callable as @c * get(t) and with return type @c type or a (possibly const) reference to @c * type. * * @li Provide a noexcept static member function named @c get, callable as @c * get(t,a) and with return type @c type or a (possibly const) reference to @c * type. */ template <typename T, typename Allocator = std::allocator<void>> struct associated_allocator #if !defined(GENERATING_DOCUMENTATION) : detail::associated_allocator_impl<T, Allocator> #endif // !defined(GENERATING_DOCUMENTATION) { #if defined(GENERATING_DOCUMENTATION) /// If @c T has a nested type @c allocator_type, <tt>T::allocator_type</tt>. /// Otherwise @c Allocator. typedef see_below type; /// If @c T has a nested type @c allocator_type, returns /// <tt>t.get_allocator()</tt>. Otherwise returns @c type(). static decltype(auto) get(const T& t) noexcept; /// If @c T has a nested type @c allocator_type, returns /// <tt>t.get_allocator()</tt>. Otherwise returns @c a. static decltype(auto) get(const T& t, const Allocator& a) noexcept; #endif // defined(GENERATING_DOCUMENTATION) }; /// Helper function to obtain an object's associated allocator. /** * @returns <tt>associated_allocator<T>::get(t)</tt> */ template <typename T> BOOST_ASIO_NODISCARD inline typename associated_allocator<T>::type get_associated_allocator(const T& t) noexcept { return associated_allocator<T>::get(t); } /// Helper function to obtain an object's associated allocator. /** * @returns <tt>associated_allocator<T, Allocator>::get(t, a)</tt> */ template <typename T, typename Allocator> BOOST_ASIO_NODISCARD inline auto get_associated_allocator( const T& t, const Allocator& a) noexcept -> decltype(associated_allocator<T, Allocator>::get(t, a)) { return associated_allocator<T, Allocator>::get(t, a); } template <typename T, typename Allocator = std::allocator<void>> using associated_allocator_t = typename associated_allocator<T, Allocator>::type; namespace detail { template <typename T, typename A, typename = void> struct associated_allocator_forwarding_base { }; template <typename T, typename A> struct associated_allocator_forwarding_base<T, A, enable_if_t< is_same< typename associated_allocator<T, A>::asio_associated_allocator_is_unspecialised, void >::value >> { typedef void asio_associated_allocator_is_unspecialised; }; } // namespace detail /// Specialisation of associated_allocator for @c std::reference_wrapper. template <typename T, typename Allocator> struct associated_allocator<reference_wrapper<T>, Allocator> #if !defined(GENERATING_DOCUMENTATION) : detail::associated_allocator_forwarding_base<T, Allocator> #endif // !defined(GENERATING_DOCUMENTATION) { /// Forwards @c type to the associator specialisation for the unwrapped type /// @c T. typedef typename associated_allocator<T, Allocator>::type type; /// Forwards the request to get the allocator to the associator specialisation /// for the unwrapped type @c T. static type get(reference_wrapper<T> t) noexcept { return associated_allocator<T, Allocator>::get(t.get()); } /// Forwards the request to get the allocator to the associator specialisation /// for the unwrapped type @c T. static auto get(reference_wrapper<T> t, const Allocator& a) noexcept -> decltype(associated_allocator<T, Allocator>::get(t.get(), a)) { return associated_allocator<T, Allocator>::get(t.get(), a); } }; } // namespace asio } // namespace boost #include <boost/asio/detail/pop_options.hpp> #endif // BOOST_ASIO_ASSOCIATED_ALLOCATOR_HPP