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//
// 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
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