text: //
  // detail/completion_handler.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2015 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 AUTOBOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP
  #define AUTOBOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <autoboost/asio/detail/addressof.hpp>
  #include <autoboost/asio/detail/config.hpp>
  #include <autoboost/asio/detail/fenced_block.hpp>
  #include <autoboost/asio/detail/handler_alloc_helpers.hpp>
  #include <autoboost/asio/detail/handler_invoke_helpers.hpp>
  #include <autoboost/asio/detail/operation.hpp>
  
  #include <autoboost/asio/detail/push_options.hpp>
  
  namespace autoboost {
  namespace asio {
  namespace detail {
  
  template <typename Handler>
  class completion_handler : public operation
  {
  public:
    AUTOBOOST_ASIO_DEFINE_HANDLER_PTR(completion_handler);
  
    completion_handler(Handler& h)
      : operation(&completion_handler::do_complete),
        handler_(AUTOBOOST_ASIO_MOVE_CAST(Handler)(h))
    {
    }
  
    static void do_complete(io_service_impl* owner, operation* base,
        const autoboost::system::error_code& /*ec*/,
        std::size_t /*bytes_transferred*/)
    {
      // Take ownership of the handler object.
      completion_handler* h(static_cast<completion_handler*>(base));
      ptr p = { autoboost::asio::detail::addressof(h->handler_), h, h };
  
      AUTOBOOST_ASIO_HANDLER_COMPLETION((h));
  
      // Make a copy of the handler so that the memory can be deallocated before
      // the upcall is made. Even if we're not about to make an upcall, a
      // sub-object of the handler may be the true owner of the memory associated
      // with the handler. Consequently, a local copy of the handler is required
      // to ensure that any owning sub-object remains valid until after we have
      // deallocated the memory here.
      Handler handler(AUTOBOOST_ASIO_MOVE_CAST(Handler)(h->handler_));
      p.h = autoboost::asio::detail::addressof(handler);
      p.reset();
  
      // Make the upcall if required.
      if (owner)
      {
        fenced_block b(fenced_block::half);
        AUTOBOOST_ASIO_HANDLER_INVOCATION_BEGIN(());
        autoboost_asio_handler_invoke_helpers::invoke(handler, handler);
        AUTOBOOST_ASIO_HANDLER_INVOCATION_END;
      }
    }
  
  private:
    Handler handler_;
  };
  
  } // namespace detail
  } // namespace asio
  } // namespace autoboost
  
  #include <autoboost/asio/detail/pop_options.hpp>
  
  #endif // AUTOBOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP
  