boost/asio/async_result.hpp
// // async_result.hpp // ~~~~~~~~~~~~~~~~ // // Copyright (c) 2003-2024 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 BOOST_ASIO_ASYNC_RESULT_HPP #define BOOST_ASIO_ASYNC_RESULT_HPP #if defined(_MSC_VER) && (_MSC_VER >= 1200) # pragma once #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) #include <boost/asio/detail/config.hpp> #include <boost/asio/detail/type_traits.hpp> #include <boost/asio/detail/push_options.hpp> namespace boost { namespace asio { namespace detail { template <typename T> struct is_completion_signature : false_type { }; template <typename R, typename... Args> struct is_completion_signature<R(Args...)> : true_type { }; template <typename R, typename... Args> struct is_completion_signature<R(Args...) &> : true_type { }; template <typename R, typename... Args> struct is_completion_signature<R(Args...) &&> : true_type { }; # if defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename R, typename... Args> struct is_completion_signature<R(Args...) noexcept> : true_type { }; template <typename R, typename... Args> struct is_completion_signature<R(Args...) & noexcept> : true_type { }; template <typename R, typename... Args> struct is_completion_signature<R(Args...) && noexcept> : true_type { }; # endif // defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename... T> struct are_completion_signatures : false_type { }; template <> struct are_completion_signatures<> : true_type { }; template <typename T0> struct are_completion_signatures<T0> : is_completion_signature<T0> { }; template <typename T0, typename... TN> struct are_completion_signatures<T0, TN...> : integral_constant<bool, ( is_completion_signature<T0>::value && are_completion_signatures<TN...>::value)> { }; } // namespace detail #if defined(BOOST_ASIO_HAS_CONCEPTS) namespace detail { template <typename T, typename... Args> BOOST_ASIO_CONCEPT callable_with = requires(T&& t, Args&&... args) { static_cast<T&&>(t)(static_cast<Args&&>(args)...); }; template <typename T, typename... Signatures> struct is_completion_handler_for : false_type { }; template <typename T, typename R, typename... Args> struct is_completion_handler_for<T, R(Args...)> : integral_constant<bool, (callable_with<decay_t<T>, Args...>)> { }; template <typename T, typename R, typename... Args> struct is_completion_handler_for<T, R(Args...) &> : integral_constant<bool, (callable_with<decay_t<T>&, Args...>)> { }; template <typename T, typename R, typename... Args> struct is_completion_handler_for<T, R(Args...) &&> : integral_constant<bool, (callable_with<decay_t<T>&&, Args...>)> { }; # if defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename T, typename R, typename... Args> struct is_completion_handler_for<T, R(Args...) noexcept> : integral_constant<bool, (callable_with<decay_t<T>, Args...>)> { }; template <typename T, typename R, typename... Args> struct is_completion_handler_for<T, R(Args...) & noexcept> : integral_constant<bool, (callable_with<decay_t<T>&, Args...>)> { }; template <typename T, typename R, typename... Args> struct is_completion_handler_for<T, R(Args...) && noexcept> : integral_constant<bool, (callable_with<decay_t<T>&&, Args...>)> { }; # endif // defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename T, typename Signature0, typename... SignatureN> struct is_completion_handler_for<T, Signature0, SignatureN...> : integral_constant<bool, ( is_completion_handler_for<T, Signature0>::value && is_completion_handler_for<T, SignatureN...>::value)> { }; } // namespace detail template <typename T> BOOST_ASIO_CONCEPT completion_signature = detail::is_completion_signature<T>::value; #define BOOST_ASIO_COMPLETION_SIGNATURE \ ::boost::asio::completion_signature template <typename T, typename... Signatures> BOOST_ASIO_CONCEPT completion_handler_for = detail::are_completion_signatures<Signatures...>::value && detail::is_completion_handler_for<T, Signatures...>::value; #define BOOST_ASIO_COMPLETION_HANDLER_FOR(sig) \ ::boost::asio::completion_handler_for<sig> #define BOOST_ASIO_COMPLETION_HANDLER_FOR2(sig0, sig1) \ ::boost::asio::completion_handler_for<sig0, sig1> #define BOOST_ASIO_COMPLETION_HANDLER_FOR3(sig0, sig1, sig2) \ ::boost::asio::completion_handler_for<sig0, sig1, sig2> #else // defined(BOOST_ASIO_HAS_CONCEPTS) #define BOOST_ASIO_COMPLETION_SIGNATURE typename #define BOOST_ASIO_COMPLETION_HANDLER_FOR(sig) typename #define BOOST_ASIO_COMPLETION_HANDLER_FOR2(sig0, sig1) typename #define BOOST_ASIO_COMPLETION_HANDLER_FOR3(sig0, sig1, sig2) typename #endif // defined(BOOST_ASIO_HAS_CONCEPTS) namespace detail { template <typename T> struct is_lvalue_completion_signature : false_type { }; template <typename R, typename... Args> struct is_lvalue_completion_signature<R(Args...) &> : true_type { }; # if defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename R, typename... Args> struct is_lvalue_completion_signature<R(Args...) & noexcept> : true_type { }; # endif // defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename... Signatures> struct are_any_lvalue_completion_signatures : false_type { }; template <typename Sig0> struct are_any_lvalue_completion_signatures<Sig0> : is_lvalue_completion_signature<Sig0> { }; template <typename Sig0, typename... SigN> struct are_any_lvalue_completion_signatures<Sig0, SigN...> : integral_constant<bool, ( is_lvalue_completion_signature<Sig0>::value || are_any_lvalue_completion_signatures<SigN...>::value)> { }; template <typename T> struct is_rvalue_completion_signature : false_type { }; template <typename R, typename... Args> struct is_rvalue_completion_signature<R(Args...) &&> : true_type { }; # if defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename R, typename... Args> struct is_rvalue_completion_signature<R(Args...) && noexcept> : true_type { }; # endif // defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename... Signatures> struct are_any_rvalue_completion_signatures : false_type { }; template <typename Sig0> struct are_any_rvalue_completion_signatures<Sig0> : is_rvalue_completion_signature<Sig0> { }; template <typename Sig0, typename... SigN> struct are_any_rvalue_completion_signatures<Sig0, SigN...> : integral_constant<bool, ( is_rvalue_completion_signature<Sig0>::value || are_any_rvalue_completion_signatures<SigN...>::value)> { }; template <typename T> struct simple_completion_signature; template <typename R, typename... Args> struct simple_completion_signature<R(Args...)> { typedef R type(Args...); }; template <typename R, typename... Args> struct simple_completion_signature<R(Args...) &> { typedef R type(Args...); }; template <typename R, typename... Args> struct simple_completion_signature<R(Args...) &&> { typedef R type(Args...); }; # if defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename R, typename... Args> struct simple_completion_signature<R(Args...) noexcept> { typedef R type(Args...); }; template <typename R, typename... Args> struct simple_completion_signature<R(Args...) & noexcept> { typedef R type(Args...); }; template <typename R, typename... Args> struct simple_completion_signature<R(Args...) && noexcept> { typedef R type(Args...); }; # endif // defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE) template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures> class completion_handler_async_result { public: typedef CompletionToken completion_handler_type; typedef void return_type; explicit completion_handler_async_result(completion_handler_type&) { } return_type get() { } template <typename Initiation, BOOST_ASIO_COMPLETION_HANDLER_FOR(Signatures...) RawCompletionToken, typename... Args> static return_type initiate(Initiation&& initiation, RawCompletionToken&& token, Args&&... args) { static_cast<Initiation&&>(initiation)( static_cast<RawCompletionToken&&>(token), static_cast<Args&&>(args)...); } private: completion_handler_async_result( const completion_handler_async_result&) = delete; completion_handler_async_result& operator=( const completion_handler_async_result&) = delete; }; } // namespace detail #if defined(GENERATING_DOCUMENTATION) /// An interface for customising the behaviour of an initiating function. /** * The async_result traits class is used for determining: * * @li the concrete completion handler type to be called at the end of the * asynchronous operation; * * @li the initiating function return type; and * * @li how the return value of the initiating function is obtained. * * The trait allows the handler and return types to be determined at the point * where the specific completion handler signature is known. * * This template may be specialised for user-defined completion token types. * The primary template assumes that the CompletionToken is the completion * handler. */ template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures> class async_result { public: /// The concrete completion handler type for the specific signature. typedef CompletionToken completion_handler_type; /// The return type of the initiating function. typedef void return_type; /// Construct an async result from a given handler. /** * When using a specalised async_result, the constructor has an opportunity * to initialise some state associated with the completion handler, which is * then returned from the initiating function. */ explicit async_result(completion_handler_type& h); /// Obtain the value to be returned from the initiating function. return_type get(); /// Initiate the asynchronous operation that will produce the result, and /// obtain the value to be returned from the initiating function. template <typename Initiation, typename RawCompletionToken, typename... Args> static return_type initiate( Initiation&& initiation, RawCompletionToken&& token, Args&&... args); private: async_result(const async_result&) = delete; async_result& operator=(const async_result&) = delete; }; #else // defined(GENERATING_DOCUMENTATION) template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures> class async_result : public conditional_t< detail::are_any_lvalue_completion_signatures<Signatures...>::value || !detail::are_any_rvalue_completion_signatures<Signatures...>::value, detail::completion_handler_async_result<CompletionToken, Signatures...>, async_result<CompletionToken, typename detail::simple_completion_signature<Signatures>::type...> > { public: typedef conditional_t< detail::are_any_lvalue_completion_signatures<Signatures...>::value || !detail::are_any_rvalue_completion_signatures<Signatures...>::value, detail::completion_handler_async_result<CompletionToken, Signatures...>, async_result<CompletionToken, typename detail::simple_completion_signature<Signatures>::type...> > base_type; using base_type::base_type; private: async_result(const async_result&) = delete; async_result& operator=(const async_result&) = delete; }; template <BOOST_ASIO_COMPLETION_SIGNATURE... Signatures> class async_result<void, Signatures...> { // Empty. }; #endif // defined(GENERATING_DOCUMENTATION) /// Helper template to deduce the handler type from a CompletionToken, capture /// a local copy of the handler, and then create an async_result for the /// handler. template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures> struct async_completion { /// The real handler type to be used for the asynchronous operation. typedef typename boost::asio::async_result< decay_t<CompletionToken>, Signatures...>::completion_handler_type completion_handler_type; /// Constructor. /** * The constructor creates the concrete completion handler and makes the link * between the handler and the asynchronous result. */ explicit async_completion(CompletionToken& token) : completion_handler(static_cast<conditional_t< is_same<CompletionToken, completion_handler_type>::value, completion_handler_type&, CompletionToken&&>>(token)), result(completion_handler) { } /// A copy of, or reference to, a real handler object. conditional_t< is_same<CompletionToken, completion_handler_type>::value, completion_handler_type&, completion_handler_type> completion_handler; /// The result of the asynchronous operation's initiating function. async_result<decay_t<CompletionToken>, Signatures...> result; }; namespace detail { struct async_result_memfns_base { void initiate(); }; template <typename T> struct async_result_memfns_derived : T, async_result_memfns_base { }; template <typename T, T> struct async_result_memfns_check { }; template <typename> char (&async_result_initiate_memfn_helper(...))[2]; template <typename T> char async_result_initiate_memfn_helper( async_result_memfns_check< void (async_result_memfns_base::*)(), &async_result_memfns_derived<T>::initiate>*); template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures> struct async_result_has_initiate_memfn : integral_constant<bool, sizeof(async_result_initiate_memfn_helper< async_result<decay_t<CompletionToken>, Signatures...> >(0)) != 1> { }; } // namespace detail #if defined(GENERATING_DOCUMENTATION) # define BOOST_ASIO_INITFN_RESULT_TYPE(ct, sig) \ void_or_deduced # define BOOST_ASIO_INITFN_RESULT_TYPE2(ct, sig0, sig1) \ void_or_deduced # define BOOST_ASIO_INITFN_RESULT_TYPE3(ct, sig0, sig1, sig2) \ void_or_deduced #else # define BOOST_ASIO_INITFN_RESULT_TYPE(ct, sig) \ typename ::boost::asio::async_result< \ typename ::boost::asio::decay<ct>::type, sig>::return_type # define BOOST_ASIO_INITFN_RESULT_TYPE2(ct, sig0, sig1) \ typename ::boost::asio::async_result< \ typename ::boost::asio::decay<ct>::type, sig0, sig1>::return_type # define BOOST_ASIO_INITFN_RESULT_TYPE3(ct, sig0, sig1, sig2) \ typename ::boost::asio::async_result< \ typename ::boost::asio::decay<ct>::type, sig0, sig1, sig2>::return_type #define BOOST_ASIO_HANDLER_TYPE(ct, sig) \ typename ::boost::asio::async_result< \ typename ::boost::asio::decay<ct>::type, sig>::completion_handler_type #define BOOST_ASIO_HANDLER_TYPE2(ct, sig0, sig1) \ typename ::boost::asio::async_result< \ typename ::boost::asio::decay<ct>::type, \ sig0, sig1>::completion_handler_type #define BOOST_ASIO_HANDLER_TYPE3(ct, sig0, sig1, sig2) \ typename ::boost::asio::async_result< \ typename ::boost::asio::decay<ct>::type, \ sig0, sig1, sig2>::completion_handler_type #endif #if defined(GENERATING_DOCUMENTATION) # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ct, sig) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE2(ct, sig0, sig1) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE3(ct, sig0, sig1, sig2) \ auto #elif defined(BOOST_ASIO_HAS_RETURN_TYPE_DEDUCTION) # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ct, sig) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE2(ct, sig0, sig1) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE3(ct, sig0, sig1, sig2) \ auto #else # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE(ct, sig) \ BOOST_ASIO_INITFN_RESULT_TYPE(ct, sig) # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE2(ct, sig0, sig1) \ BOOST_ASIO_INITFN_RESULT_TYPE2(ct, sig0, sig1) # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE3(ct, sig0, sig1, sig2) \ BOOST_ASIO_INITFN_RESULT_TYPE3(ct, sig0, sig1, sig2) #endif #if defined(GENERATING_DOCUMENTATION) # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ct, sig) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX2(ct, sig0, sig1) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX3(ct, sig0, sig1, sig2) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX(expr) #elif defined(BOOST_ASIO_HAS_RETURN_TYPE_DEDUCTION) # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ct, sig) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX2(ct, sig0, sig1) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX3(ct, sig0, sig1, sig2) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX(expr) #else # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX(ct, sig) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX2(ct, sig0, sig1) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_PREFIX3(ct, sig0, sig1, sig2) \ auto # define BOOST_ASIO_INITFN_AUTO_RESULT_TYPE_SUFFIX(expr) -> decltype expr #endif #if defined(GENERATING_DOCUMENTATION) # define BOOST_ASIO_INITFN_DEDUCED_RESULT_TYPE(ct, sig, expr) \ void_or_deduced # define BOOST_ASIO_INITFN_DEDUCED_RESULT_TYPE2(ct, sig0, sig1, expr) \ void_or_deduced # define BOOST_ASIO_INITFN_DEDUCED_RESULT_TYPE3(ct, sig0, sig1, sig2, expr) \ void_or_deduced #else # define BOOST_ASIO_INITFN_DEDUCED_RESULT_TYPE(ct, sig, expr) \ decltype expr # define BOOST_ASIO_INITFN_DEDUCED_RESULT_TYPE2(ct, sig0, sig1, expr) \ decltype expr # define BOOST_ASIO_INITFN_DEDUCED_RESULT_TYPE3(ct, sig0, sig1, sig2, expr) \ decltype expr #endif #if defined(GENERATING_DOCUMENTATION) template <typename CompletionToken, completion_signature... Signatures, typename Initiation, typename... Args> void_or_deduced async_initiate( Initiation&& initiation, type_identity_t<CompletionToken>& token, Args&&... args); #else // defined(GENERATING_DOCUMENTATION) template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures, typename Initiation, typename... Args> inline auto async_initiate(Initiation&& initiation, type_identity_t<CompletionToken>& token, Args&&... args) -> decltype(enable_if_t< enable_if_t< detail::are_completion_signatures<Signatures...>::value, detail::async_result_has_initiate_memfn< CompletionToken, Signatures...>>::value, async_result<decay_t<CompletionToken>, Signatures...>>::initiate( static_cast<Initiation&&>(initiation), static_cast<CompletionToken&&>(token), static_cast<Args&&>(args)...)) { return async_result<decay_t<CompletionToken>, Signatures...>::initiate( static_cast<Initiation&&>(initiation), static_cast<CompletionToken&&>(token), static_cast<Args&&>(args)...); } template < BOOST_ASIO_COMPLETION_SIGNATURE... Signatures, typename CompletionToken, typename Initiation, typename... Args> inline auto async_initiate(Initiation&& initiation, CompletionToken&& token, Args&&... args) -> decltype(enable_if_t< enable_if_t< detail::are_completion_signatures<Signatures...>::value, detail::async_result_has_initiate_memfn< CompletionToken, Signatures...>>::value, async_result<decay_t<CompletionToken>, Signatures...>>::initiate( static_cast<Initiation&&>(initiation), static_cast<CompletionToken&&>(token), static_cast<Args&&>(args)...)) { return async_result<decay_t<CompletionToken>, Signatures...>::initiate( static_cast<Initiation&&>(initiation), static_cast<CompletionToken&&>(token), static_cast<Args&&>(args)...); } template <typename CompletionToken, BOOST_ASIO_COMPLETION_SIGNATURE... Signatures, typename Initiation, typename... Args> inline typename enable_if_t< !enable_if_t< detail::are_completion_signatures<Signatures...>::value, detail::async_result_has_initiate_memfn< CompletionToken, Signatures...>>::value, async_result<decay_t<CompletionToken>, Signatures...> >::return_type async_initiate(Initiation&& initiation, type_identity_t<CompletionToken>& token, Args&&... args) { async_completion<CompletionToken, Signatures...> completion(token); static_cast<Initiation&&>(initiation)( static_cast< typename async_result<decay_t<CompletionToken>, Signatures...>::completion_handler_type&&>( completion.completion_handler), static_cast<Args&&>(args)...); return completion.result.get(); } template <BOOST_ASIO_COMPLETION_SIGNATURE... Signatures, typename CompletionToken, typename Initiation, typename... Args> inline typename enable_if_t< !enable_if_t< detail::are_completion_signatures<Signatures...>::value, detail::async_result_has_initiate_memfn< CompletionToken, Signatures...>>::value, async_result<decay_t<CompletionToken>, Signatures...> >::return_type async_initiate(Initiation&& initiation, CompletionToken&& token, Args&&... args) { async_completion<CompletionToken, Signatures...> completion(token); static_cast<Initiation&&>(initiation)( static_cast< typename async_result<decay_t<CompletionToken>, Signatures...>::completion_handler_type&&>( completion.completion_handler), static_cast<Args&&>(args)...); return completion.result.get(); } #endif // defined(GENERATING_DOCUMENTATION) #if defined(BOOST_ASIO_HAS_CONCEPTS) namespace detail { template <typename... Signatures> struct initiation_archetype { template <completion_handler_for<Signatures...> CompletionHandler> void operator()(CompletionHandler&&) const { } }; } // namespace detail template <typename T, typename... Signatures> BOOST_ASIO_CONCEPT completion_token_for = detail::are_completion_signatures<Signatures...>::value && requires(T&& t) { async_initiate<T, Signatures...>( detail::initiation_archetype<Signatures...>{}, t); }; #define BOOST_ASIO_COMPLETION_TOKEN_FOR(sig) \ ::boost::asio::completion_token_for<sig> #define BOOST_ASIO_COMPLETION_TOKEN_FOR2(sig0, sig1) \ ::boost::asio::completion_token_for<sig0, sig1> #define BOOST_ASIO_COMPLETION_TOKEN_FOR3(sig0, sig1, sig2) \ ::boost::asio::completion_token_for<sig0, sig1, sig2> #else // defined(BOOST_ASIO_HAS_CONCEPTS) #define BOOST_ASIO_COMPLETION_TOKEN_FOR(sig) typename #define BOOST_ASIO_COMPLETION_TOKEN_FOR2(sig0, sig1) typename #define BOOST_ASIO_COMPLETION_TOKEN_FOR3(sig0, sig1, sig2) typename #endif // defined(BOOST_ASIO_HAS_CONCEPTS) namespace detail { struct async_operation_probe {}; struct async_operation_probe_result {}; template <typename Call, typename = void> struct is_async_operation_call : false_type { }; template <typename Call> struct is_async_operation_call<Call, void_t< enable_if_t< is_same< result_of_t<Call>, async_operation_probe_result >::value > > > : true_type { }; } // namespace detail #if !defined(GENERATING_DOCUMENTATION) template <typename... Signatures> class async_result<detail::async_operation_probe, Signatures...> { public: typedef detail::async_operation_probe_result return_type; template <typename Initiation, typename... InitArgs> static return_type initiate(Initiation&&, detail::async_operation_probe, InitArgs&&...) { return return_type(); } }; #endif // !defined(GENERATING_DOCUMENTATION) #if defined(GENERATING_DOCUMENTATION) /// The is_async_operation trait detects whether a type @c T and arguments /// @c Args... may be used to initiate an asynchronous operation. /** * Class template @c is_async_operation is a trait is derived from @c true_type * if the expression <tt>T(Args..., token)</tt> initiates an asynchronous * operation, where @c token is an unspecified completion token type. Otherwise, * @c is_async_operation is derived from @c false_type. */ template <typename T, typename... Args> struct is_async_operation : integral_constant<bool, automatically_determined> { }; #else // defined(GENERATING_DOCUMENTATION) template <typename T, typename... Args> struct is_async_operation : detail::is_async_operation_call< T(Args..., detail::async_operation_probe)> { }; #endif // defined(GENERATING_DOCUMENTATION) #if defined(BOOST_ASIO_HAS_CONCEPTS) template <typename T, typename... Args> BOOST_ASIO_CONCEPT async_operation = is_async_operation<T, Args...>::value; #define BOOST_ASIO_ASYNC_OPERATION \ ::boost::asio::async_operation #define BOOST_ASIO_ASYNC_OPERATION1(a0) \ ::boost::asio::async_operation<a0> #define BOOST_ASIO_ASYNC_OPERATION2(a0, a1) \ ::boost::asio::async_operation<a0, a1> #define BOOST_ASIO_ASYNC_OPERATION3(a0, a1, a2) \ ::boost::asio::async_operation<a0, a1, a2> #else // defined(BOOST_ASIO_HAS_CONCEPTS) #define BOOST_ASIO_ASYNC_OPERATION typename #define BOOST_ASIO_ASYNC_OPERATION1(a0) typename #define BOOST_ASIO_ASYNC_OPERATION2(a0, a1) typename #define BOOST_ASIO_ASYNC_OPERATION3(a0, a1, a2) typename #endif // defined(BOOST_ASIO_HAS_CONCEPTS) namespace detail { struct completion_signature_probe {}; template <typename... T> struct completion_signature_probe_result { template <template <typename...> class Op> struct apply { typedef Op<T...> type; }; }; template <typename T> struct completion_signature_probe_result<T> { typedef T type; template <template <typename...> class Op> struct apply { typedef Op<T> type; }; }; template <> struct completion_signature_probe_result<void> { template <template <typename...> class Op> struct apply { typedef Op<> type; }; }; } // namespace detail #if !defined(GENERATING_DOCUMENTATION) template <typename... Signatures> class async_result<detail::completion_signature_probe, Signatures...> { public: typedef detail::completion_signature_probe_result<Signatures...> return_type; template <typename Initiation, typename... InitArgs> static return_type initiate(Initiation&&, detail::completion_signature_probe, InitArgs&&...) { return return_type(); } }; template <typename Signature> class async_result<detail::completion_signature_probe, Signature> { public: typedef detail::completion_signature_probe_result<Signature> return_type; template <typename Initiation, typename... InitArgs> static return_type initiate(Initiation&&, detail::completion_signature_probe, InitArgs&&...) { return return_type(); } }; #endif // !defined(GENERATING_DOCUMENTATION) #if defined(GENERATING_DOCUMENTATION) /// The completion_signature_of trait determines the completion signature /// of an asynchronous operation. /** * Class template @c completion_signature_of is a trait with a member type * alias @c type that denotes the completion signature of the asynchronous * operation initiated by the expression <tt>T(Args..., token)</tt> operation, * where @c token is an unspecified completion token type. If the asynchronous * operation does not have exactly one completion signature, the instantion of * the trait is well-formed but the member type alias @c type is omitted. If * the expression <tt>T(Args..., token)</tt> is not an asynchronous operation * then use of the trait is ill-formed. */ template <typename T, typename... Args> struct completion_signature_of { typedef automatically_determined type; }; #else // defined(GENERATING_DOCUMENTATION) template <typename T, typename... Args> struct completion_signature_of : result_of_t<T(Args..., detail::completion_signature_probe)> { }; #endif // defined(GENERATING_DOCUMENTATION) template <typename T, typename... Args> using completion_signature_of_t = typename completion_signature_of<T, Args...>::type; } // namespace asio } // namespace boost #include <boost/asio/detail/pop_options.hpp> #include <boost/asio/default_completion_token.hpp> #endif // BOOST_ASIO_ASYNC_RESULT_HPP