// // associated_allocator.hpp // ~~~~~~~~~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2018 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 ASIO_ASSOCIATED_ALLOCATOR_HPP #define ASIO_ASSOCIATED_ALLOCATOR_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include "asio/detail/config.hpp" #include <memory> #include "asio/detail/type_traits.hpp" #include "asio/detail/push_options.hpp" namespace asio { namespace detail { template <typename> struct associated_allocator_check { typedef void type; }; template <typename T, typename E, typename = void> struct associated_allocator_impl { typedef E type; static type get(const T&, const E& e) ASIO_NOEXCEPT { return e; } }; template <typename T, typename E> struct associated_allocator_impl<T, E, typename associated_allocator_check<typename T::allocator_type>::type> { typedef typename T::allocator_type type; static type get(const T& t, const E&) ASIO_NOEXCEPT { return t.get_allocator(); } }; } // 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. * * @li Provide a noexcept static member function named @c get, callable as @c * get(t,a) and with return type @c type. */ template <typename T, typename Allocator = std::allocator<void> > struct associated_allocator { /// If @c T has a nested type @c allocator_type, <tt>T::allocator_type</tt>. /// Otherwise @c Allocator. #if defined(GENERATING_DOCUMENTATION) typedef see_below type; #else // defined(GENERATING_DOCUMENTATION) typedef typename detail::associated_allocator_impl<T, Allocator>::type type; #endif // defined(GENERATING_DOCUMENTATION) /// If @c T has a nested type @c allocator_type, returns /// <tt>t.get_allocator()</tt>. Otherwise returns @c a. static type get(const T& t, const Allocator& a = Allocator()) ASIO_NOEXCEPT { return detail::associated_allocator_impl<T, Allocator>::get(t, a); } }; /// Helper function to obtain an object's associated allocator. /** * @returns <tt>associated_allocator<T>::get(t)</tt> */ template <typename T> inline typename associated_allocator<T>::type get_associated_allocator(const T& t) ASIO_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> inline typename associated_allocator<T, Allocator>::type get_associated_allocator(const T& t, const Allocator& a) ASIO_NOEXCEPT { return associated_allocator<T, Allocator>::get(t, a); } #if defined(ASIO_HAS_ALIAS_TEMPLATES) template <typename T, typename Allocator = std::allocator<void> > using associated_allocator_t = typename associated_allocator<T, Allocator>::type; #endif // defined(ASIO_HAS_ALIAS_TEMPLATES) } // namespace asio #include "asio/detail/pop_options.hpp" #endif // ASIO_ASSOCIATED_ALLOCATOR_HPP