583 lines
18 KiB
C++
583 lines
18 KiB
C++
//
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// async_result.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_ASYNC_RESULT_HPP
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#define ASIO_ASYNC_RESULT_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 "asio/detail/type_traits.hpp"
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#include "asio/detail/variadic_templates.hpp"
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#include "asio/detail/push_options.hpp"
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namespace asio {
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#if defined(ASIO_HAS_CONCEPTS) \
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&& defined(ASIO_HAS_VARIADIC_TEMPLATES) \
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&& defined(ASIO_HAS_DECLTYPE)
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namespace detail {
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template <typename T>
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struct is_completion_signature : false_type
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{
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};
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template <typename R, typename... Args>
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struct is_completion_signature<R(Args...)> : true_type
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{
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};
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template <typename T, typename... Args>
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ASIO_CONCEPT callable_with = requires(T t, Args&&... args)
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{
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t(static_cast<Args&&>(args)...);
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};
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template <typename T, typename Signature>
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struct is_completion_handler_for : false_type
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{
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};
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template <typename T, typename R, typename... Args>
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struct is_completion_handler_for<T, R(Args...)>
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: integral_constant<bool, (callable_with<T, Args...>)>
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{
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};
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} // namespace detail
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template <typename T>
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ASIO_CONCEPT completion_signature =
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detail::is_completion_signature<T>::value;
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#define ASIO_COMPLETION_SIGNATURE \
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::asio::completion_signature
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template <typename T, typename Signature>
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ASIO_CONCEPT completion_handler_for =
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detail::is_completion_signature<Signature>::value
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&& detail::is_completion_handler_for<T, Signature>::value;
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#define ASIO_COMPLETION_HANDLER_FOR(s) \
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::asio::completion_handler_for<s>
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#else // defined(ASIO_HAS_CONCEPTS)
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// && defined(ASIO_HAS_VARIADIC_TEMPLATES)
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// && defined(ASIO_HAS_DECLTYPE)
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#define ASIO_COMPLETION_SIGNATURE typename
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#define ASIO_COMPLETION_HANDLER_FOR(s) typename
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#endif // defined(ASIO_HAS_CONCEPTS)
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// && defined(ASIO_HAS_VARIADIC_TEMPLATES)
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// && defined(ASIO_HAS_DECLTYPE)
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/// An interface for customising the behaviour of an initiating function.
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/**
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* The async_result traits class is used for determining:
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*
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* @li the concrete completion handler type to be called at the end of the
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* asynchronous operation;
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*
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* @li the initiating function return type; and
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*
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* @li how the return value of the initiating function is obtained.
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*
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* The trait allows the handler and return types to be determined at the point
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* where the specific completion handler signature is known.
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*
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* This template may be specialised for user-defined completion token types.
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* The primary template assumes that the CompletionToken is the completion
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* handler.
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*/
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template <typename CompletionToken, ASIO_COMPLETION_SIGNATURE Signature>
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class async_result
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{
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public:
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/// The concrete completion handler type for the specific signature.
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typedef CompletionToken completion_handler_type;
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/// The return type of the initiating function.
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typedef void return_type;
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/// Construct an async result from a given handler.
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/**
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* When using a specalised async_result, the constructor has an opportunity
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* to initialise some state associated with the completion handler, which is
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* then returned from the initiating function.
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*/
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explicit async_result(completion_handler_type& h)
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{
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(void)h;
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}
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/// Obtain the value to be returned from the initiating function.
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return_type get()
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{
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}
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#if defined(GENERATING_DOCUMENTATION)
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/// Initiate the asynchronous operation that will produce the result, and
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/// obtain the value to be returned from the initiating function.
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template <typename Initiation, typename RawCompletionToken, typename... Args>
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static return_type initiate(
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ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_MOVE_ARG(RawCompletionToken) token,
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ASIO_MOVE_ARG(Args)... args);
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#elif defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename Initiation,
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ASIO_COMPLETION_HANDLER_FOR(Signature) RawCompletionToken,
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typename... Args>
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static return_type initiate(
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ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_MOVE_ARG(RawCompletionToken) token,
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ASIO_MOVE_ARG(Args)... args)
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{
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ASIO_MOVE_CAST(Initiation)(initiation)(
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ASIO_MOVE_CAST(RawCompletionToken)(token),
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ASIO_MOVE_CAST(Args)(args)...);
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}
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#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename Initiation,
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ASIO_COMPLETION_HANDLER_FOR(Signature) RawCompletionToken>
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static return_type initiate(
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ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_MOVE_ARG(RawCompletionToken) token)
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{
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ASIO_MOVE_CAST(Initiation)(initiation)(
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ASIO_MOVE_CAST(RawCompletionToken)(token));
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}
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#define ASIO_PRIVATE_INITIATE_DEF(n) \
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template <typename Initiation, \
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ASIO_COMPLETION_HANDLER_FOR(Signature) RawCompletionToken, \
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ASIO_VARIADIC_TPARAMS(n)> \
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static return_type initiate( \
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ASIO_MOVE_ARG(Initiation) initiation, \
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ASIO_MOVE_ARG(RawCompletionToken) token, \
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ASIO_VARIADIC_MOVE_PARAMS(n)) \
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{ \
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ASIO_MOVE_CAST(Initiation)(initiation)( \
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ASIO_MOVE_CAST(RawCompletionToken)(token), \
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ASIO_VARIADIC_MOVE_ARGS(n)); \
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} \
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/**/
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ASIO_VARIADIC_GENERATE(ASIO_PRIVATE_INITIATE_DEF)
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#undef ASIO_PRIVATE_INITIATE_DEF
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#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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private:
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async_result(const async_result&) ASIO_DELETED;
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async_result& operator=(const async_result&) ASIO_DELETED;
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};
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#if !defined(GENERATING_DOCUMENTATION)
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template <ASIO_COMPLETION_SIGNATURE Signature>
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class async_result<void, Signature>
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{
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// Empty.
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};
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#endif // !defined(GENERATING_DOCUMENTATION)
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/// Helper template to deduce the handler type from a CompletionToken, capture
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/// a local copy of the handler, and then create an async_result for the
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/// handler.
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template <typename CompletionToken, ASIO_COMPLETION_SIGNATURE Signature>
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struct async_completion
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{
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/// The real handler type to be used for the asynchronous operation.
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typedef typename asio::async_result<
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typename decay<CompletionToken>::type,
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Signature>::completion_handler_type completion_handler_type;
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#if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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/// Constructor.
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/**
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* The constructor creates the concrete completion handler and makes the link
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* between the handler and the asynchronous result.
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*/
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explicit async_completion(CompletionToken& token)
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: completion_handler(static_cast<typename conditional<
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is_same<CompletionToken, completion_handler_type>::value,
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completion_handler_type&, CompletionToken&&>::type>(token)),
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result(completion_handler)
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{
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}
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#else // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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explicit async_completion(typename decay<CompletionToken>::type& token)
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: completion_handler(token),
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result(completion_handler)
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{
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}
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explicit async_completion(const typename decay<CompletionToken>::type& token)
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: completion_handler(token),
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result(completion_handler)
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{
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}
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#endif // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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/// A copy of, or reference to, a real handler object.
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#if defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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typename conditional<
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is_same<CompletionToken, completion_handler_type>::value,
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completion_handler_type&, completion_handler_type>::type completion_handler;
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#else // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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completion_handler_type completion_handler;
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#endif // defined(ASIO_HAS_MOVE) || defined(GENERATING_DOCUMENTATION)
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/// The result of the asynchronous operation's initiating function.
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async_result<typename decay<CompletionToken>::type, Signature> result;
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};
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namespace detail {
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template <typename CompletionToken, typename Signature>
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struct async_result_helper
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: async_result<typename decay<CompletionToken>::type, Signature>
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{
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};
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struct async_result_memfns_base
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{
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void initiate();
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};
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template <typename T>
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struct async_result_memfns_derived
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: T, async_result_memfns_base
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{
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};
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template <typename T, T>
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struct async_result_memfns_check
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{
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};
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template <typename>
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char (&async_result_initiate_memfn_helper(...))[2];
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template <typename T>
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char async_result_initiate_memfn_helper(
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async_result_memfns_check<
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void (async_result_memfns_base::*)(),
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&async_result_memfns_derived<T>::initiate>*);
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template <typename CompletionToken, typename Signature>
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struct async_result_has_initiate_memfn
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: integral_constant<bool, sizeof(async_result_initiate_memfn_helper<
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async_result<typename decay<CompletionToken>::type, Signature>
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>(0)) != 1>
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{
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};
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} // namespace detail
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#if defined(GENERATING_DOCUMENTATION)
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# define ASIO_INITFN_RESULT_TYPE(ct, sig) \
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void_or_deduced
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#elif defined(_MSC_VER) && (_MSC_VER < 1500)
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# define ASIO_INITFN_RESULT_TYPE(ct, sig) \
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typename ::asio::detail::async_result_helper< \
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ct, sig>::return_type
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#define ASIO_HANDLER_TYPE(ct, sig) \
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typename ::asio::detail::async_result_helper< \
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ct, sig>::completion_handler_type
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#else
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# define ASIO_INITFN_RESULT_TYPE(ct, sig) \
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typename ::asio::async_result< \
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typename ::asio::decay<ct>::type, sig>::return_type
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#define ASIO_HANDLER_TYPE(ct, sig) \
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typename ::asio::async_result< \
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typename ::asio::decay<ct>::type, sig>::completion_handler_type
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#endif
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#if defined(GENERATING_DOCUMENTATION)
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# define ASIO_INITFN_AUTO_RESULT_TYPE(ct, sig) \
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auto
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#elif defined(ASIO_HAS_RETURN_TYPE_DEDUCTION)
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# define ASIO_INITFN_AUTO_RESULT_TYPE(ct, sig) \
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auto
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#else
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# define ASIO_INITFN_AUTO_RESULT_TYPE(ct, sig) \
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ASIO_INITFN_RESULT_TYPE(ct, sig)
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#endif
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#if defined(GENERATING_DOCUMENTATION)
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# define ASIO_INITFN_DEDUCED_RESULT_TYPE(ct, sig, expr) \
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void_or_deduced
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#elif defined(ASIO_HAS_DECLTYPE)
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# define ASIO_INITFN_DEDUCED_RESULT_TYPE(ct, sig, expr) \
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decltype expr
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#else
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# define ASIO_INITFN_DEDUCED_RESULT_TYPE(ct, sig, expr) \
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ASIO_INITFN_RESULT_TYPE(ct, sig)
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#endif
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#if defined(GENERATING_DOCUMENTATION)
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template <typename CompletionToken,
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completion_signature Signature,
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typename Initiation, typename... Args>
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void_or_deduced async_initiate(
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ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken),
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ASIO_MOVE_ARG(Args)... args);
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#elif defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename CompletionToken,
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ASIO_COMPLETION_SIGNATURE Signature,
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typename Initiation, typename... Args>
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inline typename constraint<
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detail::async_result_has_initiate_memfn<CompletionToken, Signature>::value,
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ASIO_INITFN_DEDUCED_RESULT_TYPE(CompletionToken, Signature,
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(async_result<typename decay<CompletionToken>::type,
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Signature>::initiate(declval<ASIO_MOVE_ARG(Initiation)>(),
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declval<ASIO_MOVE_ARG(CompletionToken)>(),
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declval<ASIO_MOVE_ARG(Args)>()...)))>::type
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async_initiate(ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken) token,
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ASIO_MOVE_ARG(Args)... args)
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{
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return async_result<typename decay<CompletionToken>::type,
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Signature>::initiate(ASIO_MOVE_CAST(Initiation)(initiation),
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ASIO_MOVE_CAST(CompletionToken)(token),
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ASIO_MOVE_CAST(Args)(args)...);
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}
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template <typename CompletionToken,
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ASIO_COMPLETION_SIGNATURE Signature,
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typename Initiation, typename... Args>
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inline typename constraint<
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!detail::async_result_has_initiate_memfn<CompletionToken, Signature>::value,
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ASIO_INITFN_RESULT_TYPE(CompletionToken, Signature)>::type
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async_initiate(ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken) token,
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ASIO_MOVE_ARG(Args)... args)
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{
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async_completion<CompletionToken, Signature> completion(token);
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ASIO_MOVE_CAST(Initiation)(initiation)(
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ASIO_MOVE_CAST(ASIO_HANDLER_TYPE(CompletionToken,
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Signature))(completion.completion_handler),
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ASIO_MOVE_CAST(Args)(args)...);
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return completion.result.get();
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}
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#else // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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template <typename CompletionToken,
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ASIO_COMPLETION_SIGNATURE Signature,
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typename Initiation>
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inline typename constraint<
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detail::async_result_has_initiate_memfn<CompletionToken, Signature>::value,
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ASIO_INITFN_DEDUCED_RESULT_TYPE(CompletionToken, Signature,
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(async_result<typename decay<CompletionToken>::type,
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Signature>::initiate(declval<ASIO_MOVE_ARG(Initiation)>(),
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declval<ASIO_MOVE_ARG(CompletionToken)>())))>::type
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async_initiate(ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken) token)
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{
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return async_result<typename decay<CompletionToken>::type,
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Signature>::initiate(ASIO_MOVE_CAST(Initiation)(initiation),
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ASIO_MOVE_CAST(CompletionToken)(token));
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}
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template <typename CompletionToken,
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ASIO_COMPLETION_SIGNATURE Signature,
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typename Initiation>
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inline typename constraint<
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!detail::async_result_has_initiate_memfn<CompletionToken, Signature>::value,
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ASIO_INITFN_RESULT_TYPE(CompletionToken, Signature)>::type
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async_initiate(ASIO_MOVE_ARG(Initiation) initiation,
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken) token)
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{
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async_completion<CompletionToken, Signature> completion(token);
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ASIO_MOVE_CAST(Initiation)(initiation)(
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ASIO_MOVE_CAST(ASIO_HANDLER_TYPE(CompletionToken,
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Signature))(completion.completion_handler));
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return completion.result.get();
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}
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#define ASIO_PRIVATE_INITIATE_DEF(n) \
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template <typename CompletionToken, \
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ASIO_COMPLETION_SIGNATURE Signature, \
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typename Initiation, ASIO_VARIADIC_TPARAMS(n)> \
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inline typename constraint< \
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detail::async_result_has_initiate_memfn< \
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CompletionToken, Signature>::value, \
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ASIO_INITFN_DEDUCED_RESULT_TYPE(CompletionToken, Signature, \
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(async_result<typename decay<CompletionToken>::type, \
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Signature>::initiate(declval<ASIO_MOVE_ARG(Initiation)>(), \
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declval<ASIO_MOVE_ARG(CompletionToken)>(), \
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ASIO_VARIADIC_MOVE_DECLVAL(n))))>::type \
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async_initiate(ASIO_MOVE_ARG(Initiation) initiation, \
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken) token, \
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ASIO_VARIADIC_MOVE_PARAMS(n)) \
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{ \
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return async_result<typename decay<CompletionToken>::type, \
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Signature>::initiate(ASIO_MOVE_CAST(Initiation)(initiation), \
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ASIO_MOVE_CAST(CompletionToken)(token), \
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ASIO_VARIADIC_MOVE_ARGS(n)); \
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} \
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\
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template <typename CompletionToken, \
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ASIO_COMPLETION_SIGNATURE Signature, \
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typename Initiation, ASIO_VARIADIC_TPARAMS(n)> \
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inline typename constraint< \
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!detail::async_result_has_initiate_memfn< \
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CompletionToken, Signature>::value, \
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ASIO_INITFN_RESULT_TYPE(CompletionToken, Signature)>::type \
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async_initiate(ASIO_MOVE_ARG(Initiation) initiation, \
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ASIO_NONDEDUCED_MOVE_ARG(CompletionToken) token, \
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ASIO_VARIADIC_MOVE_PARAMS(n)) \
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{ \
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async_completion<CompletionToken, Signature> completion(token); \
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\
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ASIO_MOVE_CAST(Initiation)(initiation)( \
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ASIO_MOVE_CAST(ASIO_HANDLER_TYPE(CompletionToken, \
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Signature))(completion.completion_handler), \
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ASIO_VARIADIC_MOVE_ARGS(n)); \
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\
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return completion.result.get(); \
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} \
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/**/
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ASIO_VARIADIC_GENERATE(ASIO_PRIVATE_INITIATE_DEF)
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#undef ASIO_PRIVATE_INITIATE_DEF
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#endif // defined(ASIO_HAS_VARIADIC_TEMPLATES)
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#if defined(ASIO_HAS_CONCEPTS) \
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&& defined(ASIO_HAS_VARIADIC_TEMPLATES) \
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&& defined(ASIO_HAS_DECLTYPE)
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namespace detail {
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template <typename Signature>
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struct initiation_archetype
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{
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template <completion_handler_for<Signature> CompletionHandler>
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void operator()(CompletionHandler&&) const
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|
{
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}
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};
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|
|
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} // namespace detail
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|
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template <typename T, typename Signature>
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|
ASIO_CONCEPT completion_token_for =
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detail::is_completion_signature<Signature>::value
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|
&&
|
|
requires(T&& t)
|
|
{
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|
async_initiate<T, Signature>(detail::initiation_archetype<Signature>{}, t);
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|
};
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|
|
|
#define ASIO_COMPLETION_TOKEN_FOR(s) \
|
|
::asio::completion_token_for<s>
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|
|
|
#else // defined(ASIO_HAS_CONCEPTS)
|
|
// && defined(ASIO_HAS_VARIADIC_TEMPLATES)
|
|
// && defined(ASIO_HAS_DECLTYPE)
|
|
|
|
#define ASIO_COMPLETION_TOKEN_FOR(s) typename
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|
|
|
#endif // defined(ASIO_HAS_CONCEPTS)
|
|
// && defined(ASIO_HAS_VARIADIC_TEMPLATES)
|
|
// && defined(ASIO_HAS_DECLTYPE)
|
|
|
|
namespace detail {
|
|
|
|
template <typename T, typename = void>
|
|
struct default_completion_token_impl
|
|
{
|
|
typedef void type;
|
|
};
|
|
|
|
template <typename T>
|
|
struct default_completion_token_impl<T,
|
|
typename void_type<typename T::default_completion_token_type>::type>
|
|
{
|
|
typedef typename T::default_completion_token_type type;
|
|
};
|
|
|
|
} // namespace detail
|
|
|
|
#if defined(GENERATING_DOCUMENTATION)
|
|
|
|
/// Traits type used to determine the default completion token type associated
|
|
/// with a type (such as an executor).
|
|
/**
|
|
* A program may specialise this traits type if the @c T template parameter in
|
|
* the specialisation is a user-defined type.
|
|
*
|
|
* Specialisations of this trait may provide a nested typedef @c type, which is
|
|
* a default-constructible completion token type.
|
|
*/
|
|
template <typename T>
|
|
struct default_completion_token
|
|
{
|
|
/// If @c T has a nested type @c default_completion_token_type,
|
|
/// <tt>T::default_completion_token_type</tt>. Otherwise the typedef @c type
|
|
/// is not defined.
|
|
typedef see_below type;
|
|
};
|
|
#else
|
|
template <typename T>
|
|
struct default_completion_token
|
|
: detail::default_completion_token_impl<T>
|
|
{
|
|
};
|
|
#endif
|
|
|
|
#if defined(ASIO_HAS_ALIAS_TEMPLATES)
|
|
|
|
template <typename T>
|
|
using default_completion_token_t = typename default_completion_token<T>::type;
|
|
|
|
#endif // defined(ASIO_HAS_ALIAS_TEMPLATES)
|
|
|
|
#if defined(ASIO_HAS_DEFAULT_FUNCTION_TEMPLATE_ARGUMENTS)
|
|
|
|
#define ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(e) \
|
|
= typename ::asio::default_completion_token<e>::type
|
|
#define ASIO_DEFAULT_COMPLETION_TOKEN(e) \
|
|
= typename ::asio::default_completion_token<e>::type()
|
|
|
|
#else // defined(ASIO_HAS_DEFAULT_FUNCTION_TEMPLATE_ARGUMENTS)
|
|
|
|
#define ASIO_DEFAULT_COMPLETION_TOKEN_TYPE(e)
|
|
#define ASIO_DEFAULT_COMPLETION_TOKEN(e)
|
|
|
|
#endif // defined(ASIO_HAS_DEFAULT_FUNCTION_TEMPLATE_ARGUMENTS)
|
|
|
|
} // namespace asio
|
|
|
|
#include "asio/detail/pop_options.hpp"
|
|
|
|
#endif // ASIO_ASYNC_RESULT_HPP
|