Chris@16: //
Chris@16: // async_result.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_ASYNC_RESULT_HPP
Chris@16: #define BOOST_ASIO_ASYNC_RESULT_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 <boost/asio/handler_type.hpp>
Chris@16: 
Chris@16: #include <boost/asio/detail/push_options.hpp>
Chris@16: 
Chris@16: namespace boost {
Chris@16: namespace asio {
Chris@16: 
Chris@16: /// An interface for customising the behaviour of an initiating function.
Chris@16: /**
Chris@16:  * This template may be specialised for user-defined handler types.
Chris@16:  */
Chris@16: template <typename Handler>
Chris@16: class async_result
Chris@16: {
Chris@16: public:
Chris@16:   /// The return type of the initiating function.
Chris@16:   typedef void type;
Chris@16: 
Chris@16:   /// Construct an async result from a given handler.
Chris@16:   /**
Chris@16:    * When using a specalised async_result, the constructor has an opportunity
Chris@16:    * to initialise some state associated with the handler, which is then
Chris@16:    * returned from the initiating function.
Chris@16:    */
Chris@16:   explicit async_result(Handler&)
Chris@16:   {
Chris@16:   }
Chris@16: 
Chris@16:   /// Obtain the value to be returned from the initiating function.
Chris@16:   type get()
Chris@16:   {
Chris@16:   }
Chris@16: };
Chris@16: 
Chris@16: namespace detail {
Chris@16: 
Chris@16: // Helper template to deduce the true type of a handler, capture a local copy
Chris@16: // of the handler, and then create an async_result for the handler.
Chris@16: template <typename Handler, typename Signature>
Chris@16: struct async_result_init
Chris@16: {
Chris@16:   explicit async_result_init(BOOST_ASIO_MOVE_ARG(Handler) orig_handler)
Chris@16:     : handler(BOOST_ASIO_MOVE_CAST(Handler)(orig_handler)),
Chris@16:       result(handler)
Chris@16:   {
Chris@16:   }
Chris@16: 
Chris@16:   typename handler_type<Handler, Signature>::type handler;
Chris@16:   async_result<typename handler_type<Handler, Signature>::type> result;
Chris@16: };
Chris@16: 
Chris@16: template <typename Handler, typename Signature>
Chris@16: struct async_result_type_helper
Chris@16: {
Chris@16:   typedef typename async_result<
Chris@16:       typename handler_type<Handler, Signature>::type
Chris@16:     >::type type;
Chris@16: };
Chris@16: 
Chris@16: } // namespace detail
Chris@16: } // namespace asio
Chris@16: } // namespace boost
Chris@16: 
Chris@16: #include <boost/asio/detail/pop_options.hpp>
Chris@16: 
Chris@16: #if defined(GENERATING_DOCUMENTATION)
Chris@16: # define BOOST_ASIO_INITFN_RESULT_TYPE(h, sig) \
Chris@16:   void_or_deduced
Chris@16: #elif defined(_MSC_VER) && (_MSC_VER < 1500)
Chris@16: # define BOOST_ASIO_INITFN_RESULT_TYPE(h, sig) \
Chris@16:   typename ::boost::asio::detail::async_result_type_helper<h, sig>::type
Chris@16: #else
Chris@16: # define BOOST_ASIO_INITFN_RESULT_TYPE(h, sig) \
Chris@16:   typename ::boost::asio::async_result< \
Chris@16:     typename ::boost::asio::handler_type<h, sig>::type>::type
Chris@16: #endif
Chris@16: 
Chris@16: #endif // BOOST_ASIO_ASYNC_RESULT_HPP