require.hpp
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//
// require.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_REQUIRE_HPP
#define ASIO_REQUIRE_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/is_applicable_property.hpp"
#include "asio/traits/require_member.hpp"
#include "asio/traits/require_free.hpp"
#include "asio/traits/static_require.hpp"
#include "asio/detail/push_options.hpp"
#if defined(GENERATING_DOCUMENTATION)
namespace asio {
/// A customisation point that applies a concept-preserving property to an
/// object.
/**
* The name <tt>require</tt> denotes a customisation point object. The
* expression <tt>asio::require(E, P0, Pn...)</tt> for some
* subexpressions <tt>E</tt> and <tt>P0</tt>, and where <tt>Pn...</tt>
* represents <tt>N</tt> subexpressions (where <tt>N</tt> is 0 or more, and with
* types <tt>T = decay_t<decltype(E)></tt> and <tt>Prop0 =
* decay_t<decltype(P0)></tt>) is expression-equivalent to:
*
* @li If <tt>is_applicable_property_v<T, Prop0> && Prop0::is_requirable</tt> is
* not a well-formed constant expression with value <tt>true</tt>,
* <tt>asio::require(E, P0, Pn...)</tt> is ill-formed.
*
* @li Otherwise, <tt>E</tt> if <tt>N == 0</tt> and the expression
* <tt>Prop0::template static_query_v<T> == Prop0::value()</tt> is a
* well-formed constant expression with value <tt>true</tt>.
*
* @li Otherwise, <tt>(E).require(P0)</tt> if <tt>N == 0</tt> and the expression
* <tt>(E).require(P0)</tt> is a valid expression.
*
* @li Otherwise, <tt>require(E, P0)</tt> if <tt>N == 0</tt> and the expression
* <tt>require(E, P0)</tt> is a valid expression with overload resolution
* performed in a context that does not include the declaration of the
* <tt>require</tt> customization point object.
*
* @li Otherwise,
* <tt>asio::require(asio::require(E, P0), Pn...)</tt>
* if <tt>N > 0</tt> and the expression
* <tt>asio::require(asio::require(E, P0), Pn...)</tt>
* is a valid expression.
*
* @li Otherwise, <tt>asio::require(E, P0, Pn...)</tt> is ill-formed.
*/
inline constexpr unspecified require = unspecified;
/// A type trait that determines whether a @c require expression is well-formed.
/**
* Class template @c can_require is a trait that is derived from
* @c true_type if the expression <tt>asio::require(std::declval<T>(),
* std::declval<Properties>()...)</tt> is well formed; otherwise @c false_type.
*/
template <typename T, typename... Properties>
struct can_require :
integral_constant<bool, automatically_determined>
{
};
/// A type trait that determines whether a @c require expression will not throw.
/**
* Class template @c is_nothrow_require is a trait that is derived from
* @c true_type if the expression <tt>asio::require(std::declval<T>(),
* std::declval<Properties>()...)</tt> is @c noexcept; otherwise @c false_type.
*/
template <typename T, typename... Properties>
struct is_nothrow_require :
integral_constant<bool, automatically_determined>
{
};
/// A type trait that determines the result type of a @c require expression.
/**
* Class template @c require_result is a trait that determines the result
* type of the expression <tt>asio::require(std::declval<T>(),
* std::declval<Properties>()...)</tt>.
*/
template <typename T, typename... Properties>
struct require_result
{
/// The result of the @c require expression.
typedef automatically_determined type;
};
} // namespace asio
#else // defined(GENERATING_DOCUMENTATION)
namespace asio_require_fn {
using asio::decay;
using asio::declval;
using asio::enable_if;
using asio::is_applicable_property;
using asio::traits::require_free;
using asio::traits::require_member;
using asio::traits::static_require;
void require();
enum overload_type
{
identity,
call_member,
call_free,
two_props,
n_props,
ill_formed
};
template <typename T, typename Properties, typename = void>
struct call_traits
{
ASIO_STATIC_CONSTEXPR(overload_type, overload = ill_formed);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept = false);
typedef void result_type;
};
template <typename T, typename Property>
struct call_traits<T, void(Property),
typename enable_if<
(
is_applicable_property<
typename decay<T>::type,
typename decay<Property>::type
>::value
&&
decay<Property>::type::is_requirable
&&
static_require<T, Property>::is_valid
)
>::type>
{
ASIO_STATIC_CONSTEXPR(overload_type, overload = identity);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept = true);
#if defined(ASIO_HAS_MOVE)
typedef ASIO_MOVE_ARG(T) result_type;
#else // defined(ASIO_HAS_MOVE)
typedef ASIO_MOVE_ARG(typename decay<T>::type) result_type;
#endif // defined(ASIO_HAS_MOVE)
};
template <typename T, typename Property>
struct call_traits<T, void(Property),
typename enable_if<
(
is_applicable_property<
typename decay<T>::type,
typename decay<Property>::type
>::value
&&
decay<Property>::type::is_requirable
&&
!static_require<T, Property>::is_valid
&&
require_member<T, Property>::is_valid
)
>::type> :
require_member<T, Property>
{
ASIO_STATIC_CONSTEXPR(overload_type, overload = call_member);
};
template <typename T, typename Property>
struct call_traits<T, void(Property),
typename enable_if<
(
is_applicable_property<
typename decay<T>::type,
typename decay<Property>::type
>::value
&&
decay<Property>::type::is_requirable
&&
!static_require<T, Property>::is_valid
&&
!require_member<T, Property>::is_valid
&&
require_free<T, Property>::is_valid
)
>::type> :
require_free<T, Property>
{
ASIO_STATIC_CONSTEXPR(overload_type, overload = call_free);
};
template <typename T, typename P0, typename P1>
struct call_traits<T, void(P0, P1),
typename enable_if<
call_traits<T, void(P0)>::overload != ill_formed
&&
call_traits<
typename call_traits<T, void(P0)>::result_type,
void(P1)
>::overload != ill_formed
>::type>
{
ASIO_STATIC_CONSTEXPR(overload_type, overload = two_props);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
(
call_traits<T, void(P0)>::is_noexcept
&&
call_traits<
typename call_traits<T, void(P0)>::result_type,
void(P1)
>::is_noexcept
));
typedef typename decay<
typename call_traits<
typename call_traits<T, void(P0)>::result_type,
void(P1)
>::result_type
>::type result_type;
};
template <typename T, typename P0, typename P1, typename ASIO_ELLIPSIS PN>
struct call_traits<T, void(P0, P1, PN ASIO_ELLIPSIS),
typename enable_if<
call_traits<T, void(P0)>::overload != ill_formed
&&
call_traits<
typename call_traits<T, void(P0)>::result_type,
void(P1, PN ASIO_ELLIPSIS)
>::overload != ill_formed
>::type>
{
ASIO_STATIC_CONSTEXPR(overload_type, overload = n_props);
ASIO_STATIC_CONSTEXPR(bool, is_noexcept =
(
call_traits<T, void(P0)>::is_noexcept
&&
call_traits<
typename call_traits<T, void(P0)>::result_type,
void(P1, PN ASIO_ELLIPSIS)
>::is_noexcept
));
typedef typename decay<
typename call_traits<
typename call_traits<T, void(P0)>::result_type,
void(P1, PN ASIO_ELLIPSIS)
>::result_type
>::type result_type;
};
struct impl
{
template <typename T, typename Property>
ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
call_traits<T, void(Property)>::overload == identity,
typename call_traits<T, void(Property)>::result_type
>::type
operator()(
ASIO_MOVE_ARG(T) t,
ASIO_MOVE_ARG(Property)) const
ASIO_NOEXCEPT_IF((
call_traits<T, void(Property)>::is_noexcept))
{
return ASIO_MOVE_CAST(T)(t);
}
template <typename T, typename Property>
ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
call_traits<T, void(Property)>::overload == call_member,
typename call_traits<T, void(Property)>::result_type
>::type
operator()(
ASIO_MOVE_ARG(T) t,
ASIO_MOVE_ARG(Property) p) const
ASIO_NOEXCEPT_IF((
call_traits<T, void(Property)>::is_noexcept))
{
return ASIO_MOVE_CAST(T)(t).require(
ASIO_MOVE_CAST(Property)(p));
}
template <typename T, typename Property>
ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
call_traits<T, void(Property)>::overload == call_free,
typename call_traits<T, void(Property)>::result_type
>::type
operator()(
ASIO_MOVE_ARG(T) t,
ASIO_MOVE_ARG(Property) p) const
ASIO_NOEXCEPT_IF((
call_traits<T, void(Property)>::is_noexcept))
{
return require(
ASIO_MOVE_CAST(T)(t),
ASIO_MOVE_CAST(Property)(p));
}
template <typename T, typename P0, typename P1>
ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
call_traits<T, void(P0, P1)>::overload == two_props,
typename call_traits<T, void(P0, P1)>::result_type
>::type
operator()(
ASIO_MOVE_ARG(T) t,
ASIO_MOVE_ARG(P0) p0,
ASIO_MOVE_ARG(P1) p1) const
ASIO_NOEXCEPT_IF((
call_traits<T, void(P0, P1)>::is_noexcept))
{
return (*this)(
(*this)(
ASIO_MOVE_CAST(T)(t),
ASIO_MOVE_CAST(P0)(p0)),
ASIO_MOVE_CAST(P1)(p1));
}
template <typename T, typename P0, typename P1,
typename ASIO_ELLIPSIS PN>
ASIO_NODISCARD ASIO_CONSTEXPR typename enable_if<
call_traits<T, void(P0, P1, PN ASIO_ELLIPSIS)>::overload == n_props,
typename call_traits<T, void(P0, P1, PN ASIO_ELLIPSIS)>::result_type
>::type
operator()(
ASIO_MOVE_ARG(T) t,
ASIO_MOVE_ARG(P0) p0,
ASIO_MOVE_ARG(P1) p1,
ASIO_MOVE_ARG(PN) ASIO_ELLIPSIS pn) const
ASIO_NOEXCEPT_IF((
call_traits<T, void(P0, P1, PN ASIO_ELLIPSIS)>::is_noexcept))
{
return (*this)(
(*this)(
ASIO_MOVE_CAST(T)(t),
ASIO_MOVE_CAST(P0)(p0)),
ASIO_MOVE_CAST(P1)(p1),
ASIO_MOVE_CAST(PN)(pn) ASIO_ELLIPSIS);
}
};
template <typename T = impl>
struct static_instance
{
static const T instance;
};
template <typename T>
const T static_instance<T>::instance = {};
} // namespace asio_require_fn
namespace asio {
namespace {
static ASIO_CONSTEXPR const asio_require_fn::impl&
require = asio_require_fn::static_instance<>::instance;
} // namespace
#if defined(ASIO_HAS_VARIADIC_TEMPLATES)
template <typename T, typename... Properties>
struct can_require :
integral_constant<bool,
asio_require_fn::call_traits<T, void(Properties...)>::overload
!= asio_require_fn::ill_formed>
{
};
#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
template <typename T, typename P0 = void,
typename P1 = void, typename P2 = void>
struct can_require :
integral_constant<bool,
asio_require_fn::call_traits<T, void(P0, P1, P2)>::overload
!= asio_require_fn::ill_formed>
{
};
template <typename T, typename P0, typename P1>
struct can_require<T, P0, P1> :
integral_constant<bool,
asio_require_fn::call_traits<T, void(P0, P1)>::overload
!= asio_require_fn::ill_formed>
{
};
template <typename T, typename P0>
struct can_require<T, P0> :
integral_constant<bool,
asio_require_fn::call_traits<T, void(P0)>::overload
!= asio_require_fn::ill_formed>
{
};
template <typename T>
struct can_require<T> :
false_type
{
};
#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
template <typename T, typename ASIO_ELLIPSIS Properties>
constexpr bool can_require_v
= can_require<T, Properties ASIO_ELLIPSIS>::value;
#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
#if defined(ASIO_HAS_VARIADIC_TEMPLATES)
template <typename T, typename... Properties>
struct is_nothrow_require :
integral_constant<bool,
asio_require_fn::call_traits<T, void(Properties...)>::is_noexcept>
{
};
#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
template <typename T, typename P0 = void,
typename P1 = void, typename P2 = void>
struct is_nothrow_require :
integral_constant<bool,
asio_require_fn::call_traits<T, void(P0, P1, P2)>::is_noexcept>
{
};
template <typename T, typename P0, typename P1>
struct is_nothrow_require<T, P0, P1> :
integral_constant<bool,
asio_require_fn::call_traits<T, void(P0, P1)>::is_noexcept>
{
};
template <typename T, typename P0>
struct is_nothrow_require<T, P0> :
integral_constant<bool,
asio_require_fn::call_traits<T, void(P0)>::is_noexcept>
{
};
template <typename T>
struct is_nothrow_require<T> :
false_type
{
};
#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
#if defined(ASIO_HAS_VARIABLE_TEMPLATES)
template <typename T, typename ASIO_ELLIPSIS Properties>
constexpr bool is_nothrow_require_v
= is_nothrow_require<T, Properties ASIO_ELLIPSIS>::value;
#endif // defined(ASIO_HAS_VARIABLE_TEMPLATES)
#if defined(ASIO_HAS_VARIADIC_TEMPLATES)
template <typename T, typename... Properties>
struct require_result
{
typedef typename asio_require_fn::call_traits<
T, void(Properties...)>::result_type type;
};
#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
template <typename T, typename P0 = void,
typename P1 = void, typename P2 = void>
struct require_result
{
typedef typename asio_require_fn::call_traits<
T, void(P0, P1, P2)>::result_type type;
};
template <typename T, typename P0, typename P1>
struct require_result<T, P0, P1>
{
typedef typename asio_require_fn::call_traits<
T, void(P0, P1)>::result_type type;
};
template <typename T, typename P0>
struct require_result<T, P0>
{
typedef typename asio_require_fn::call_traits<
T, void(P0)>::result_type type;
};
template <typename T>
struct require_result<T>
{
};
#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
} // namespace asio
#endif // defined(GENERATING_DOCUMENTATION)
#include "asio/detail/pop_options.hpp"
#endif // ASIO_REQUIRE_HPP