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bind_handler.hpp
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bind_handler.hpp
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//
// 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