| // |
| // impl/use_future.hpp |
| // ~~~~~~~~~~~~~~~~~~~ |
| // |
| // Copyright (c) 2003-2012 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_IMPL_USE_FUTURE_HPP |
| #define ASIO_IMPL_USE_FUTURE_HPP |
| |
| #if defined(_MSC_VER) && (_MSC_VER >= 1200) |
| # pragma once |
| #endif // defined(_MSC_VER) && (_MSC_VER >= 1200) |
| |
| #include "asio/detail/config.hpp" |
| #include <future> |
| #include "asio/async_result.hpp" |
| #include "asio/error_code.hpp" |
| #include "asio/handler_type.hpp" |
| #include "asio/system_error.hpp" |
| |
| #include "asio/detail/push_options.hpp" |
| |
| namespace asio { |
| namespace detail { |
| |
| // Completion handler to adapt a promise as a completion handler. |
| template <typename T> |
| class promise_handler |
| { |
| public: |
| // Construct from use_future special value. |
| template <typename Allocator> |
| promise_handler(use_future_t<Allocator> uf) |
| : promise_(std::allocate_shared<std::promise<T> >( |
| uf.get_allocator(), std::allocator_arg, uf.get_allocator())) |
| { |
| } |
| |
| void operator()(T t) |
| { |
| promise_->set_value(t); |
| } |
| |
| void operator()(const asio::error_code& ec, T t) |
| { |
| if (ec) |
| promise_->set_exception( |
| std::make_exception_ptr( |
| asio::system_error(ec))); |
| else |
| promise_->set_value(t); |
| } |
| |
| //private: |
| std::shared_ptr<std::promise<T> > promise_; |
| }; |
| |
| // Completion handler to adapt a void promise as a completion handler. |
| template <> |
| class promise_handler<void> |
| { |
| public: |
| // Construct from use_future special value. Used during rebinding. |
| template <typename Allocator> |
| promise_handler(use_future_t<Allocator> uf) |
| : promise_(std::allocate_shared<std::promise<void> >( |
| uf.get_allocator(), std::allocator_arg, uf.get_allocator())) |
| { |
| } |
| |
| void operator()() |
| { |
| promise_->set_value(); |
| } |
| |
| void operator()(const asio::error_code& ec) |
| { |
| if (ec) |
| promise_->set_exception( |
| std::make_exception_ptr( |
| asio::system_error(ec))); |
| else |
| promise_->set_value(); |
| } |
| |
| //private: |
| std::shared_ptr<std::promise<void> > promise_; |
| }; |
| |
| // Ensure any exceptions thrown from the handler are propagated back to the |
| // caller via the future. |
| template <typename Function, typename T> |
| void asio_handler_invoke(Function f, promise_handler<T>* h) |
| { |
| std::shared_ptr<std::promise<T> > p(h->promise_); |
| try |
| { |
| f(); |
| } |
| catch (...) |
| { |
| p->set_exception(std::current_exception()); |
| } |
| } |
| |
| } // namespace detail |
| |
| #if !defined(GENERATING_DOCUMENTATION) |
| |
| // Handler traits specialisation for promise_handler. |
| template <typename T> |
| class async_result<detail::promise_handler<T> > |
| { |
| public: |
| // The initiating function will return a future. |
| typedef std::future<T> type; |
| |
| // Constructor creates a new promise for the async operation, and obtains the |
| // corresponding future. |
| explicit async_result(detail::promise_handler<T>& h) |
| { |
| value_ = h.promise_->get_future(); |
| } |
| |
| // Obtain the future to be returned from the initiating function. |
| type get() { return std::move(value_); } |
| |
| private: |
| type value_; |
| }; |
| |
| // Handler type specialisation for use_future. |
| template <typename Allocator, typename ReturnType> |
| struct handler_type<use_future_t<Allocator>, ReturnType()> |
| { |
| typedef detail::promise_handler<void> type; |
| }; |
| |
| // Handler type specialisation for use_future. |
| template <typename Allocator, typename ReturnType, typename Arg1> |
| struct handler_type<use_future_t<Allocator>, ReturnType(Arg1)> |
| { |
| typedef detail::promise_handler<Arg1> type; |
| }; |
| |
| // Handler type specialisation for use_future. |
| template <typename Allocator, typename ReturnType> |
| struct handler_type<use_future_t<Allocator>, |
| ReturnType(asio::error_code)> |
| { |
| typedef detail::promise_handler<void> type; |
| }; |
| |
| // Handler type specialisation for use_future. |
| template <typename Allocator, typename ReturnType, typename Arg2> |
| struct handler_type<use_future_t<Allocator>, |
| ReturnType(asio::error_code, Arg2)> |
| { |
| typedef detail::promise_handler<Arg2> type; |
| }; |
| |
| #endif // !defined(GENERATING_DOCUMENTATION) |
| |
| } // namespace asio |
| |
| #include "asio/detail/pop_options.hpp" |
| |
| #endif // ASIO_IMPL_USE_FUTURE_HPP |