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This is the documentation for a development version of boost.

boost/asio/impl/redirect_error.hpp


// impl/redirect_error.hpp
// ~~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2024 Christopher M. Kohlhoff (chris at kohlhoff 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)
//

#ifndef BOOST_ASIO_IMPL_REDIRECT_ERROR_HPP
#define BOOST_ASIO_IMPL_REDIRECT_ERROR_HPP

#if defined(_MSC_VER) && (_MSC_VER >= 1200)
# pragma once
#endif // defined(_MSC_VER) && (_MSC_VER >= 1200)

#include <boost/asio/detail/config.hpp>
#include <boost/asio/associated_executor.hpp>
#include <boost/asio/associator.hpp>
#include <boost/asio/async_result.hpp>
#include <boost/asio/detail/handler_cont_helpers.hpp>
#include <boost/asio/detail/initiation_base.hpp>
#include <boost/asio/detail/type_traits.hpp>
#include <boost/system/system_error.hpp>

#include <boost/asio/detail/push_options.hpp>

namespace boost {
namespace asio {
namespace detail {

// Class to adapt a redirect_error_t as a completion handler.
template <typename Handler>
class redirect_error_handler
{
public:
  typedef void result_type;

  template <typename CompletionToken>
  redirect_error_handler(redirect_error_t<CompletionToken> e)
    : ec_(e.ec_),
      handler_(static_cast<CompletionToken&&>(e.token_))
  {
  }

  template <typename RedirectedHandler>
  redirect_error_handler(boost::system::error_code& ec,
      RedirectedHandler&& h)
    : ec_(ec),
      handler_(static_cast<RedirectedHandler&&>(h))
  {
  }

  void operator()()
  {
    static_cast<Handler&&>(handler_)();
  }

  template <typename Arg, typename... Args>
  enable_if_t<
    !is_same<decay_t<Arg>, boost::system::error_code>::value
  >
  operator()(Arg&& arg, Args&&... args)
  {
    static_cast<Handler&&>(handler_)(
        static_cast<Arg&&>(arg),
        static_cast<Args&&>(args)...);
  }

  template <typename... Args>
  void operator()(const boost::system::error_code& ec, Args&&... args)
  {
    ec_ = ec;
    static_cast<Handler&&>(handler_)(static_cast<Args&&>(args)...);
  }

//private:
  boost::system::error_code& ec_;
  Handler handler_;
};

template <typename Handler>
inline bool asio_handler_is_continuation(
    redirect_error_handler<Handler>* this_handler)
{
  return boost_asio_handler_cont_helpers::is_continuation(
        this_handler->handler_);
}

template <typename Signature>
struct redirect_error_signature
{
  typedef Signature type;
};

template <typename R, typename... Args>
struct redirect_error_signature<R(boost::system::error_code, Args...)>
{
  typedef R type(Args...);
};

template <typename R, typename... Args>
struct redirect_error_signature<R(const boost::system::error_code&, Args...)>
{
  typedef R type(Args...);
};

template <typename R, typename... Args>
struct redirect_error_signature<R(boost::system::error_code, Args...) &>
{
  typedef R type(Args...) &;
};

template <typename R, typename... Args>
struct redirect_error_signature<R(const boost::system::error_code&, Args...) &>
{
  typedef R type(Args...) &;
};

template <typename R, typename... Args>
struct redirect_error_signature<R(boost::system::error_code, Args...) &&>
{
  typedef R type(Args...) &&;
};

template <typename R, typename... Args>
struct redirect_error_signature<R(const boost::system::error_code&, Args...) &&>
{
  typedef R type(Args...) &&;
};

#if defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE)

template <typename R, typename... Args>
struct redirect_error_signature<
  R(boost::system::error_code, Args...) noexcept>
{
  typedef R type(Args...) & noexcept;
};

template <typename R, typename... Args>
struct redirect_error_signature<
  R(const boost::system::error_code&, Args...) noexcept>
{
  typedef R type(Args...) & noexcept;
};

template <typename R, typename... Args>
struct redirect_error_signature<
  R(boost::system::error_code, Args...) & noexcept>
{
  typedef R type(Args...) & noexcept;
};

template <typename R, typename... Args>
struct redirect_error_signature<
  R(const boost::system::error_code&, Args...) & noexcept>
{
  typedef R type(Args...) & noexcept;
};

template <typename R, typename... Args>
struct redirect_error_signature<
  R(boost::system::error_code, Args...) && noexcept>
{
  typedef R type(Args...) && noexcept;
};

template <typename R, typename... Args>
struct redirect_error_signature<
  R(const boost::system::error_code&, Args...) && noexcept>
{
  typedef R type(Args...) && noexcept;
};

#endif // defined(BOOST_ASIO_HAS_NOEXCEPT_FUNCTION_TYPE)

} // namespace detail

#if !defined(GENERATING_DOCUMENTATION)

template <typename CompletionToken, typename Signature>
struct async_result<redirect_error_t<CompletionToken>, Signature>
  : async_result<CompletionToken,
      typename detail::redirect_error_signature<Signature>::type>
{
  template <typename Initiation>
  struct init_wrapper : detail::initiation_base<Initiation>
  {
    using detail::initiation_base<Initiation>::initiation_base;

    template <typename Handler, typename... Args>
    void operator()(Handler&& handler,
        boost::system::error_code* ec, Args&&... args) &&
    {
      static_cast<Initiation&&>(*this)(
          detail::redirect_error_handler<decay_t<Handler>>(
            *ec, static_cast<Handler&&>(handler)),
          static_cast<Args&&>(args)...);
    }

    template <typename Handler, typename... Args>
    void operator()(Handler&& handler,
        boost::system::error_code* ec, Args&&... args) const &
    {
      static_cast<const Initiation&>(*this)(
          detail::redirect_error_handler<decay_t<Handler>>(
            *ec, static_cast<Handler&&>(handler)),
          static_cast<Args&&>(args)...);
    }
  };

  template <typename Initiation, typename RawCompletionToken, typename... Args>
  static auto initiate(Initiation&& initiation,
      RawCompletionToken&& token, Args&&... args)
    -> decltype(
      async_initiate<
        conditional_t<
          is_const<remove_reference_t<RawCompletionToken>>::value,
            const CompletionToken, CompletionToken>,
        typename detail::redirect_error_signature<Signature>::type>(
          declval<init_wrapper<decay_t<Initiation>>>(),
          token.token_, &token.ec_, static_cast<Args&&>(args)...))
  {
    return async_initiate<
      conditional_t<
        is_const<remove_reference_t<RawCompletionToken>>::value,
          const CompletionToken, CompletionToken>,
      typename detail::redirect_error_signature<Signature>::type>(
        init_wrapper<decay_t<Initiation>>(
          static_cast<Initiation&&>(initiation)),
        token.token_, &token.ec_, static_cast<Args&&>(args)...);
  }
};

template <template <typename, typename> class Associator,
    typename Handler, typename DefaultCandidate>
struct associator<Associator,
    detail::redirect_error_handler<Handler>, DefaultCandidate>
  : Associator<Handler, DefaultCandidate>
{
  static typename Associator<Handler, DefaultCandidate>::type get(
      const detail::redirect_error_handler<Handler>& h) noexcept
  {
    return Associator<Handler, DefaultCandidate>::get(h.handler_);
  }

  static auto get(const detail::redirect_error_handler<Handler>& h,
      const DefaultCandidate& c) noexcept
    -> decltype(Associator<Handler, DefaultCandidate>::get(h.handler_, c))
  {
    return Associator<Handler, DefaultCandidate>::get(h.handler_, c);
  }
};

template <typename... Signatures>
struct async_result<partial_redirect_error, Signatures...>
{
  template <typename Initiation, typename RawCompletionToken, typename... Args>
  static auto initiate(Initiation&& initiation,
      RawCompletionToken&& token, Args&&... args)
    -> decltype(
      async_initiate<Signatures...>(
        static_cast<Initiation&&>(initiation),
        redirect_error_t<
          default_completion_token_t<associated_executor_t<Initiation>>>(
            default_completion_token_t<associated_executor_t<Initiation>>{},
            token.ec_),
        static_cast<Args&&>(args)...))
  {
    return async_initiate<Signatures...>(
        static_cast<Initiation&&>(initiation),
        redirect_error_t<
          default_completion_token_t<associated_executor_t<Initiation>>>(
            default_completion_token_t<associated_executor_t<Initiation>>{},
            token.ec_),
        static_cast<Args&&>(args)...);
  }
};

#endif // !defined(GENERATING_DOCUMENTATION)

} // namespace asio
} // namespace boost

#include <boost/asio/detail/pop_options.hpp>

#endif // BOOST_ASIO_IMPL_REDIRECT_ERROR_HPP