boost/beast/core/detail/bind_handler.hpp
// // Copyright (c) 2016-2019 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_DETAIL_BIND_HANDLER_HPP #define BOOST_BEAST_DETAIL_BIND_HANDLER_HPP #include <boost/beast/core/error.hpp> #include <boost/beast/core/detail/tuple.hpp> #include <boost/asio/associator.hpp> #include <boost/asio/handler_continuation_hook.hpp> #include <boost/core/ignore_unused.hpp> #include <boost/mp11/integer_sequence.hpp> #include <boost/bind/std_placeholders.hpp> #include <boost/is_placeholder.hpp> #include <functional> #include <type_traits> #include <utility> namespace boost { namespace beast { namespace detail { //------------------------------------------------------------------------------ // // bind_handler // //------------------------------------------------------------------------------ template<class Handler, class... Args> class bind_wrapper { using args_type = detail::tuple<Args...>; Handler h_; args_type args_; template <template <typename, typename> class Associator, typename T, typename DefaultCandidate> friend struct net::associator; template<class Arg, class Vals> static typename std::enable_if< std::is_placeholder<typename std::decay<Arg>::type>::value == 0 && boost::is_placeholder<typename std::decay<Arg>::type>::value == 0, Arg&&>::type extract(Arg&& arg, Vals&& vals) { boost::ignore_unused(vals); return std::forward<Arg>(arg); } template<class Arg, class Vals> static typename std::enable_if< std::is_placeholder<typename std::decay<Arg>::type>::value != 0, tuple_element<std::is_placeholder< typename std::decay<Arg>::type>::value - 1, Vals>>::type&& extract(Arg&&, Vals&& vals) { return detail::get<std::is_placeholder< typename std::decay<Arg>::type>::value - 1>( std::forward<Vals>(vals)); } template<class Arg, class Vals> static typename std::enable_if< boost::is_placeholder<typename std::decay<Arg>::type>::value != 0 && std::is_placeholder<typename std::decay<Arg>::type>::value == 0, tuple_element<boost::is_placeholder< typename std::decay<Arg>::type>::value - 1, Vals>>::type&& extract(Arg&&, Vals&& vals) { return detail::get<boost::is_placeholder< typename std::decay<Arg>::type>::value - 1>( std::forward<Vals>(vals)); } template<class ArgsTuple, std::size_t... S> static void invoke( Handler& h, ArgsTuple& args, tuple<>&&, mp11::index_sequence<S...>) { boost::ignore_unused(args); h(detail::get<S>(std::move(args))...); } template< class ArgsTuple, class ValsTuple, std::size_t... S> static void invoke( Handler& h, ArgsTuple& args, ValsTuple&& vals, mp11::index_sequence<S...>) { boost::ignore_unused(args); boost::ignore_unused(vals); h(extract(detail::get<S>(std::move(args)), std::forward<ValsTuple>(vals))...); } public: using result_type = void; // asio needs this bind_wrapper(bind_wrapper&&) = default; bind_wrapper(bind_wrapper const&) = default; template< class DeducedHandler, class... Args_> explicit bind_wrapper( DeducedHandler&& handler, Args_&&... args) : h_(std::forward<DeducedHandler>(handler)) , args_(std::forward<Args_>(args)...) { } template<class... Values> void operator()(Values&&... values) { invoke(h_, args_, tuple<Values&&...>( std::forward<Values>(values)...), mp11::index_sequence_for<Args...>()); } // friend bool asio_handler_is_continuation( bind_wrapper* op) { using boost::asio::asio_handler_is_continuation; return asio_handler_is_continuation( std::addressof(op->h_)); } }; template<class Handler, class... Args> class bind_back_wrapper; template<class Handler, class... Args> class bind_front_wrapper; //------------------------------------------------------------------------------ // // bind_front // //------------------------------------------------------------------------------ template<class Handler, class... Args> class bind_front_wrapper { Handler h_; detail::tuple<Args...> args_; template <template <typename, typename> class Associator, typename T, typename DefaultCandidate> friend struct net::associator; template<std::size_t... I, class... Ts> void invoke( std::false_type, mp11::index_sequence<I...>, Ts&&... ts) { h_( detail::get<I>(std::move(args_))..., std::forward<Ts>(ts)...); } template<std::size_t... I, class... Ts> void invoke( std::true_type, mp11::index_sequence<I...>, Ts&&... ts) { std::mem_fn(h_)( detail::get<I>(std::move(args_))..., std::forward<Ts>(ts)...); } public: using result_type = void; // asio needs this bind_front_wrapper(bind_front_wrapper&&) = default; bind_front_wrapper(bind_front_wrapper const&) = default; template<class Handler_, class... Args_> bind_front_wrapper( Handler_&& handler, Args_&&... args) : h_(std::forward<Handler_>(handler)) , args_(std::forward<Args_>(args)...) { } template<class... Ts> void operator()(Ts&&... ts) { invoke( std::is_member_function_pointer<Handler>{}, mp11::index_sequence_for<Args...>{}, std::forward<Ts>(ts)...); } // friend bool asio_handler_is_continuation( bind_front_wrapper* op) { using boost::asio::asio_handler_is_continuation; return asio_handler_is_continuation( std::addressof(op->h_)); } }; } // detail } // beast } // boost //------------------------------------------------------------------------------ namespace boost { namespace asio { template <template <typename, typename> class Associator, typename Handler, typename... Args, typename DefaultCandidate> struct associator<Associator, beast::detail::bind_wrapper<Handler, Args...>, DefaultCandidate> : Associator<Handler, DefaultCandidate> { static typename Associator<Handler, DefaultCandidate>::type get( const beast::detail::bind_wrapper<Handler, Args...>& h) noexcept { return Associator<Handler, DefaultCandidate>::get(h.h_); } static auto get(const beast::detail::bind_wrapper<Handler, Args...>& h, const DefaultCandidate& c) noexcept -> decltype(Associator<Handler, DefaultCandidate>::get(h.h_, c)) { return Associator<Handler, DefaultCandidate>::get(h.h_, c); } }; template <template <typename, typename> class Associator, typename Handler, typename... Args, typename DefaultCandidate> struct associator<Associator, beast::detail::bind_front_wrapper<Handler, Args...>, DefaultCandidate> : Associator<Handler, DefaultCandidate> { static typename Associator<Handler, DefaultCandidate>::type get( const beast::detail::bind_front_wrapper<Handler, Args...>& h) noexcept { return Associator<Handler, DefaultCandidate>::get(h.h_); } static auto get(const beast::detail::bind_front_wrapper<Handler, Args...>& h, const DefaultCandidate& c) noexcept -> decltype(Associator<Handler, DefaultCandidate>::get(h.h_, c)) { return Associator<Handler, DefaultCandidate>::get(h.h_, c); } }; } // asio } // boost //------------------------------------------------------------------------------ namespace std { // VFALCO Using std::bind on a completion handler will // cause undefined behavior later, because the executor // associated with the handler is not propagated to the // wrapper returned by std::bind; these overloads are // deleted to prevent mistakes. If this creates a problem // please contact me. template<class Handler, class... Args> void bind(boost::beast::detail::bind_wrapper< Handler, Args...>, ...) = delete; template<class Handler, class... Args> void bind(boost::beast::detail::bind_front_wrapper< Handler, Args...>, ...) = delete; } // std //------------------------------------------------------------------------------ #endif