Chris@16: //
Chris@16: // impl/use_future.hpp
Chris@16: // ~~~~~~~~~~~~~~~~~~~
Chris@16: //
Chris@101: // Copyright (c) 2003-2015 Christopher M. Kohlhoff (chris at kohlhoff dot com)
Chris@16: //
Chris@16: // Distributed under the Boost Software License, Version 1.0. (See accompanying
Chris@16: // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
Chris@16: //
Chris@16: 
Chris@16: #ifndef BOOST_ASIO_IMPL_USE_FUTURE_HPP
Chris@16: #define BOOST_ASIO_IMPL_USE_FUTURE_HPP
Chris@16: 
Chris@16: #if defined(_MSC_VER) && (_MSC_VER >= 1200)
Chris@16: # pragma once
Chris@16: #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
Chris@16: 
Chris@16: #include <boost/asio/detail/config.hpp>
Chris@16: #include <future>
Chris@16: #include <boost/asio/async_result.hpp>
Chris@16: #include <boost/system/error_code.hpp>
Chris@16: #include <boost/asio/handler_type.hpp>
Chris@16: #include <boost/system/system_error.hpp>
Chris@16: 
Chris@16: #include <boost/asio/detail/push_options.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace asio {
Chris@16: namespace detail {
Chris@16: 
Chris@16:   // Completion handler to adapt a promise as a completion handler.
Chris@16:   template <typename T>
Chris@16:   class promise_handler
Chris@16:   {
Chris@16:   public:
Chris@16:     // Construct from use_future special value.
Chris@16:     template <typename Allocator>
Chris@16:     promise_handler(use_future_t<Allocator> uf)
Chris@16:       : promise_(std::allocate_shared<std::promise<T> >(
Chris@16:             uf.get_allocator(), std::allocator_arg, uf.get_allocator()))
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     void operator()(T t)
Chris@16:     {
Chris@16:       promise_->set_value(t);
Chris@16:     }
Chris@16: 
Chris@16:     void operator()(const boost::system::error_code& ec, T t)
Chris@16:     {
Chris@16:       if (ec)
Chris@16:         promise_->set_exception(
Chris@16:             std::make_exception_ptr(
Chris@16:               boost::system::system_error(ec)));
Chris@16:       else
Chris@16:         promise_->set_value(t);
Chris@16:     }
Chris@16: 
Chris@16:   //private:
Chris@16:     std::shared_ptr<std::promise<T> > promise_;
Chris@16:   };
Chris@16: 
Chris@16:   // Completion handler to adapt a void promise as a completion handler.
Chris@16:   template <>
Chris@16:   class promise_handler<void>
Chris@16:   {
Chris@16:   public:
Chris@16:     // Construct from use_future special value. Used during rebinding.
Chris@16:     template <typename Allocator>
Chris@16:     promise_handler(use_future_t<Allocator> uf)
Chris@16:       : promise_(std::allocate_shared<std::promise<void> >(
Chris@16:             uf.get_allocator(), std::allocator_arg, uf.get_allocator()))
Chris@16:     {
Chris@16:     }
Chris@16: 
Chris@16:     void operator()()
Chris@16:     {
Chris@16:       promise_->set_value();
Chris@16:     }
Chris@16: 
Chris@16:     void operator()(const boost::system::error_code& ec)
Chris@16:     {
Chris@16:       if (ec)
Chris@16:         promise_->set_exception(
Chris@16:             std::make_exception_ptr(
Chris@16:               boost::system::system_error(ec)));
Chris@16:       else
Chris@16:         promise_->set_value();
Chris@16:     }
Chris@16: 
Chris@16:   //private:
Chris@16:     std::shared_ptr<std::promise<void> > promise_;
Chris@16:   };
Chris@16: 
Chris@16:   // Ensure any exceptions thrown from the handler are propagated back to the
Chris@16:   // caller via the future.
Chris@16:   template <typename Function, typename T>
Chris@16:   void asio_handler_invoke(Function f, promise_handler<T>* h)
Chris@16:   {
Chris@16:     std::shared_ptr<std::promise<T> > p(h->promise_);
Chris@16:     try
Chris@16:     {
Chris@16:       f();
Chris@16:     }
Chris@16:     catch (...)
Chris@16:     {
Chris@16:       p->set_exception(std::current_exception());
Chris@16:     }
Chris@16:   }
Chris@16: 
Chris@16: } // namespace detail
Chris@16: 
Chris@16: #if !defined(GENERATING_DOCUMENTATION)
Chris@16: 
Chris@16: // Handler traits specialisation for promise_handler.
Chris@16: template <typename T>
Chris@16: class async_result<detail::promise_handler<T> >
Chris@16: {
Chris@16: public:
Chris@16:   // The initiating function will return a future.
Chris@16:   typedef std::future<T> type;
Chris@16: 
Chris@16:   // Constructor creates a new promise for the async operation, and obtains the
Chris@16:   // corresponding future.
Chris@16:   explicit async_result(detail::promise_handler<T>& h)
Chris@16:   {
Chris@16:     value_ = h.promise_->get_future();
Chris@16:   }
Chris@16: 
Chris@16:   // Obtain the future to be returned from the initiating function.
Chris@16:   type get() { return std::move(value_); }
Chris@16: 
Chris@16: private:
Chris@16:   type value_;
Chris@16: };
Chris@16: 
Chris@16: // Handler type specialisation for use_future.
Chris@16: template <typename Allocator, typename ReturnType>
Chris@16: struct handler_type<use_future_t<Allocator>, ReturnType()>
Chris@16: {
Chris@16:   typedef detail::promise_handler<void> type;
Chris@16: };
Chris@16: 
Chris@16: // Handler type specialisation for use_future.
Chris@16: template <typename Allocator, typename ReturnType, typename Arg1>
Chris@16: struct handler_type<use_future_t<Allocator>, ReturnType(Arg1)>
Chris@16: {
Chris@16:   typedef detail::promise_handler<Arg1> type;
Chris@16: };
Chris@16: 
Chris@16: // Handler type specialisation for use_future.
Chris@16: template <typename Allocator, typename ReturnType>
Chris@16: struct handler_type<use_future_t<Allocator>,
Chris@16:     ReturnType(boost::system::error_code)>
Chris@16: {
Chris@16:   typedef detail::promise_handler<void> type;
Chris@16: };
Chris@16: 
Chris@16: // Handler type specialisation for use_future.
Chris@16: template <typename Allocator, typename ReturnType, typename Arg2>
Chris@16: struct handler_type<use_future_t<Allocator>,
Chris@16:     ReturnType(boost::system::error_code, Arg2)>
Chris@16: {
Chris@16:   typedef detail::promise_handler<Arg2> type;
Chris@16: };
Chris@16: 
Chris@16: #endif // !defined(GENERATING_DOCUMENTATION)
Chris@16: 
Chris@16: } // namespace asio
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/asio/detail/pop_options.hpp>
Chris@16: 
Chris@16: #endif // BOOST_ASIO_IMPL_USE_FUTURE_HPP