126 lines
3.6 KiB
C++
126 lines
3.6 KiB
C++
//
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// associated_allocator.hpp
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// ~~~~~~~~~~~~~~~~~~~~~~~~
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//
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// Copyright (c) 2003-2021 Christopher M. Kohlhoff (chris at kohlhoff dot com)
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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#ifndef ASIO_ASSOCIATED_ALLOCATOR_HPP
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#define ASIO_ASSOCIATED_ALLOCATOR_HPP
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#if defined(_MSC_VER) && (_MSC_VER >= 1200)
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# pragma once
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#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
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#include "asio/detail/config.hpp"
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#include <memory>
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#include "asio/detail/type_traits.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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namespace detail {
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template <typename T, typename E, typename = void>
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struct associated_allocator_impl
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{
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typedef E type;
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static type get(const T&, const E& e) ASIO_NOEXCEPT
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{
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return e;
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}
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};
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template <typename T, typename E>
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struct associated_allocator_impl<T, E,
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typename void_type<typename T::allocator_type>::type>
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{
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typedef typename T::allocator_type type;
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static type get(const T& t, const E&) ASIO_NOEXCEPT
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{
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return t.get_allocator();
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}
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};
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} // namespace detail
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/// Traits type used to obtain the allocator associated with an object.
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/**
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* A program may specialise this traits type if the @c T template parameter in
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* the specialisation is a user-defined type. The template parameter @c
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* Allocator shall be a type meeting the Allocator requirements.
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*
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* Specialisations shall meet the following requirements, where @c t is a const
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* reference to an object of type @c T, and @c a is an object of type @c
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* Allocator.
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*
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* @li Provide a nested typedef @c type that identifies a type meeting the
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* Allocator requirements.
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*
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* @li Provide a noexcept static member function named @c get, callable as @c
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* get(t) and with return type @c type.
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*
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* @li Provide a noexcept static member function named @c get, callable as @c
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* get(t,a) and with return type @c type.
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*/
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template <typename T, typename Allocator = std::allocator<void> >
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struct associated_allocator
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{
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/// If @c T has a nested type @c allocator_type, <tt>T::allocator_type</tt>.
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/// Otherwise @c Allocator.
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#if defined(GENERATING_DOCUMENTATION)
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typedef see_below type;
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#else // defined(GENERATING_DOCUMENTATION)
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typedef typename detail::associated_allocator_impl<T, Allocator>::type type;
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#endif // defined(GENERATING_DOCUMENTATION)
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/// If @c T has a nested type @c allocator_type, returns
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/// <tt>t.get_allocator()</tt>. Otherwise returns @c a.
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static type get(const T& t,
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const Allocator& a = Allocator()) ASIO_NOEXCEPT
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{
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return detail::associated_allocator_impl<T, Allocator>::get(t, a);
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}
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};
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/// Helper function to obtain an object's associated allocator.
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/**
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* @returns <tt>associated_allocator<T>::get(t)</tt>
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*/
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template <typename T>
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inline typename associated_allocator<T>::type
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get_associated_allocator(const T& t) ASIO_NOEXCEPT
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{
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return associated_allocator<T>::get(t);
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}
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/// Helper function to obtain an object's associated allocator.
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/**
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* @returns <tt>associated_allocator<T, Allocator>::get(t, a)</tt>
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*/
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template <typename T, typename Allocator>
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inline typename associated_allocator<T, Allocator>::type
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get_associated_allocator(const T& t, const Allocator& a) ASIO_NOEXCEPT
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{
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return associated_allocator<T, Allocator>::get(t, a);
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}
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#if defined(ASIO_HAS_ALIAS_TEMPLATES)
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template <typename T, typename Allocator = std::allocator<void> >
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using associated_allocator_t
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= typename associated_allocator<T, Allocator>::type;
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#endif // defined(ASIO_HAS_ALIAS_TEMPLATES)
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} // namespace asio
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#include "asio/detail/pop_options.hpp"
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#endif // ASIO_ASSOCIATED_ALLOCATOR_HPP
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