async_result.hpp

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//
// Copyright (c) 2016-2017 Vinnie Falco (vinnie dot falco at gmail 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)
//
// Official repository: https://github.com/boostorg/beast
//

#ifndef BOOST_BEAST_ASYNC_COMPLETION_HPP
#define BOOST_BEAST_ASYNC_COMPLETION_HPP

#include <boost/beast/config.hpp>
#include <boost/beast/core/type_traits.hpp>
#include <boost/asio/async_result.hpp>
#include <boost/asio/handler_type.hpp>
#include <type_traits>
#include <utility>

namespace boost {
namespace beast {

template<class CompletionToken, class Signature>
class async_result
{
    BOOST_STATIC_ASSERT(
        ! std::is_reference<CompletionToken>::value);

    boost::asio::async_result<typename
        boost::asio::handler_type<CompletionToken,
            Signature>::type> impl_;

    async_result(async_result const&) = delete;
    async_result& operator=(async_result const&) = delete;

public:
    using completion_handler_type =
        typename boost::asio::handler_type<
            CompletionToken, Signature>::type;

    using return_type =
        typename boost::asio::async_result<
            completion_handler_type>::type;

    explicit
    async_result(completion_handler_type& h)
        : impl_(h)
    {
    }

    return_type
    get()
    {
        return impl_.get();
    }
};

template<class CompletionToken, class Signature>
struct async_completion
{
    using completion_handler_type = typename async_result<
        typename std::decay<CompletionToken>::type,
            Signature>::completion_handler_type;

    explicit
    async_completion(CompletionToken& token)
        : completion_handler(static_cast<typename std::conditional<
            std::is_same<CompletionToken, completion_handler_type>::value,
                completion_handler_type&, CompletionToken&&>::type>(token))
        , result(completion_handler)
    {
        // CompletionToken is not invokable with the given signature
        static_assert(is_completion_handler<
                completion_handler_type, Signature>::value,
            "CompletionToken requirements not met: signature mismatch");
    }

    typename std::conditional<std::is_same<
        CompletionToken, completion_handler_type>::value,
            completion_handler_type&,
            completion_handler_type
                >::type completion_handler;

    async_result<typename std::decay<
        CompletionToken>::type, Signature> result;
};

template<class CompletionToken, typename Signature>
using handler_type = typename beast::async_result<
    typename std::decay<CompletionToken>::type,
        Signature>::completion_handler_type;

template<class CompletionToken, typename Signature>
using async_return_type = typename beast::async_result<
    typename std::decay<CompletionToken>::type,
        Signature>::return_type;

} // beast
} // boost

#endif