mysql/detail/intermediate_handler.hpp

0001 //
0002 // Copyright (c) 2019-2025 Ruben Perez Hidalgo (rubenperez038 at gmail dot com)
0003 //
0004 // Distributed under the Boost Software License, Version 1.0. (See accompanying
0005 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
0006 //
0007
0008 #ifndef BOOST_MYSQL_DETAIL_INTERMEDIATE_HANDLER_HPP
0009 #define BOOST_MYSQL_DETAIL_INTERMEDIATE_HANDLER_HPP
0010
0011 #include <boost/asio/associator.hpp>
0012
0013 #include <utility>
0014
0015 namespace boost {
0016 namespace mysql {
0017 namespace detail {
0018
0019 // An intermediate handler that propagates associated characteristics.
0020 // HandlerFn must be a function void(Handler&&, args...) that calls the handler
0021 template <class HandlerFn, class FinalHandler>
0022 struct intermediate_handler
0023 {
0024     HandlerFn fn;
0025     FinalHandler handler;
0026
0027     template <class... Args>
0028     void operator()(Args&&... args)
0029     {
0030         fn(std::move(handler), std::forward<Args>(args)...);
0031     }
0032 };
0033
0034 template <class HandlerFn, class FinalHandler>
0035 intermediate_handler<typename std::decay<HandlerFn>::type, typename std::decay<FinalHandler>::type> make_intermediate_handler(
0036     HandlerFn&& fn,
0037     FinalHandler&& handler
0038 )
0039 {
0040     return {std::forward<HandlerFn>(fn), std::forward<FinalHandler>(handler)};
0041 }
0042
0043 }  // namespace detail
0044 }  // namespace mysql
0045
0046 namespace asio {
0047
0048 template <
0049     template <typename, typename>
0050     class Associator,
0051     class HandlerFn,
0052     class FinalHandler,
0053     typename DefaultCandidate>
0054 struct associator<Associator, mysql::detail::intermediate_handler<HandlerFn, FinalHandler>, DefaultCandidate>
0055     : Associator<FinalHandler, DefaultCandidate>
0056 {
0057     static typename Associator<FinalHandler, DefaultCandidate>::type get(
0058         const mysql::detail::intermediate_handler<HandlerFn, FinalHandler>& h
0059     ) noexcept
0060     {
0061         return Associator<FinalHandler, DefaultCandidate>::get(h.handler);
0062     }
0063
0064     static auto get(
0065         const mysql::detail::intermediate_handler<HandlerFn, FinalHandler>& h,
0066         const DefaultCandidate& c
0067     ) noexcept -> decltype(Associator<FinalHandler, DefaultCandidate>::get(h.handler, c))
0068     {
0069         return Associator<FinalHandler, DefaultCandidate>::get(h.handler, c);
0070     }
0071 };
0072
0073 }  // namespace asio
0074
0075 }  // namespace boost
0076
0077 #endif