context.hpp
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//
// execution/context.hpp
// ~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2020 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_EXECUTION_CONTEXT2_HPP
#define ASIO_EXECUTION_CONTEXT2_HPP
#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
#include "asio/detail/config.hpp"
#include "asio/detail/type_traits.hpp"
#include "asio/execution/executor.hpp"
#include "asio/execution/scheduler.hpp"
#include "asio/execution/sender.hpp"
#include "asio/is_applicable_property.hpp"
#include "asio/traits/query_static_constexpr_member.hpp"
#include "asio/traits/static_query.hpp"
#if defined(ASIO_HAS_STD_ANY)
# include <any>
#endif // defined(ASIO_HAS_STD_ANY)
#include "asio/detail/push_options.hpp"
namespace asio {
#if defined(GENERATING_DOCUMENTATION)
namespace execution {
/// A property that is used to obtain the execution context that is associated
/// with an executor.
struct context_t
{
/// The context_t property applies to executors, senders, and schedulers.
template <typename T>
static constexpr bool is_applicable_property_v =
is_executor_v<T> || is_sender_v<T> || is_scheduler_v<T>;
/// The context_t property cannot be required.
static constexpr bool is_requirable = false;
/// The context_t property cannot be preferred.
static constexpr bool is_preferable = false;
/// The type returned by queries against an @c any_executor.
typedef std::any polymorphic_query_result_type;
};
/// A special value used for accessing the context_t property.
constexpr context_t context;
} // namespace execution
#else // defined(GENERATING_DOCUMENTATION)
namespace execution {
namespace detail {
template <int I = 0>
struct context_t
{
#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
template <typename T>
ASIO_STATIC_CONSTEXPR(bool,
is_applicable_property_v = is_executor<T>::value
|| is_sender<T>::value || is_scheduler<T>::value);
#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
ASIO_STATIC_CONSTEXPR(bool, is_requirable = false);
ASIO_STATIC_CONSTEXPR(bool, is_preferable = false);
#if defined(ASIO_HAS_STD_ANY)
typedef std::any polymorphic_query_result_type;
#endif // defined(ASIO_HAS_STD_ANY)
ASIO_CONSTEXPR context_t()
{
}
#if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
&& defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
template <typename T>
static ASIO_CONSTEXPR
typename traits::query_static_constexpr_member<T, context_t>::result_type
static_query()
ASIO_NOEXCEPT_IF((
traits::query_static_constexpr_member<T, context_t>::is_noexcept))
{
return traits::query_static_constexpr_member<T, context_t>::value();
}
template <typename E, typename T = decltype(context_t::static_query<E>())>
static ASIO_CONSTEXPR const T static_query_v
= context_t::static_query<E>();
#endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
// && defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
#if !defined(ASIO_HAS_CONSTEXPR)
static const context_t instance;
#endif // !defined(ASIO_HAS_CONSTEXPR)
};
#if defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
&& defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
template <int I> template <typename E, typename T>
const T context_t<I>::static_query_v;
#endif // defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
// && defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
#if !defined(ASIO_HAS_CONSTEXPR)
template <int I>
const context_t<I> context_t<I>::instance;
#endif
} // namespace detail
typedef detail::context_t<> context_t;
#if defined(ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION)
constexpr context_t context;
#else // defined(ASIO_HAS_CONSTEXPR) || defined(GENERATING_DOCUMENTATION)
namespace { static const context_t& context = context_t::instance; }
#endif
} // namespace execution
#if !defined(ASIO_HAS_VARIABLE_TEMPLATES)
template <typename T>
struct is_applicable_property<T, execution::context_t>
: integral_constant<bool,
execution::is_executor<T>::value
|| execution::is_sender<T>::value
|| execution::is_scheduler<T>::value>
{
};
#endif // !defined(ASIO_HAS_VARIABLE_TEMPLATES)
namespace traits {
#if !defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT) \
|| !defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
template <typename T>
struct static_query<T, execution::context_t,
typename enable_if<
traits::query_static_constexpr_member<T,
execution::context_t>::is_valid
>::type>
{
ASIO_STATIC_CONSTEXPR(bool, is_valid = true);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
typedef typename traits::query_static_constexpr_member<T,
execution::context_t>::result_type result_type;
static ASIO_CONSTEXPR result_type value()
{
return traits::query_static_constexpr_member<T,
execution::context_t>::value();
}
};
#endif // !defined(ASIO_HAS_DEDUCED_STATIC_QUERY_TRAIT)
// || !defined(ASIO_HAS_SFINAE_VARIABLE_TEMPLATES)
} // namespace traits
#endif // defined(GENERATING_DOCUMENTATION)
} // namespace asio
#include "asio/detail/pop_options.hpp"
#endif // ASIO_EXECUTION_CONTEXT2_HPP