text: //
  // detail/win_iocp_overlapped_ptr.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2014 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_DETAIL_WIN_IOCP_OVERLAPPED_PTR_HPP
  #define BOOST_ASIO_DETAIL_WIN_IOCP_OVERLAPPED_PTR_HPP
  
  #if defined(_MSC_VER) && (_MSC_VER >= 1200)
  # pragma once
  #endif // defined(_MSC_VER) && (_MSC_VER >= 1200)
  
  #include <boost/asio/detail/config.hpp>
  
  #if defined(BOOST_ASIO_HAS_IOCP)
  
  #include <boost/asio/io_service.hpp>
  #include <boost/asio/detail/addressof.hpp>
  #include <boost/asio/detail/handler_alloc_helpers.hpp>
  #include <boost/asio/detail/noncopyable.hpp>
  #include <boost/asio/detail/win_iocp_overlapped_op.hpp>
  #include <boost/asio/detail/win_iocp_io_service.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace detail {
  
  // Wraps a handler to create an OVERLAPPED object for use with overlapped I/O.
  class win_iocp_overlapped_ptr
    : private noncopyable
  {
  public:
    // Construct an empty win_iocp_overlapped_ptr.
    win_iocp_overlapped_ptr()
      : ptr_(0),
        iocp_service_(0)
    {
    }
  
    // Construct an win_iocp_overlapped_ptr to contain the specified handler.
    template <typename Handler>
    explicit win_iocp_overlapped_ptr(
        boost::asio::io_service& io_service, BOOST_ASIO_MOVE_ARG(Handler) handler)
      : ptr_(0),
        iocp_service_(0)
    {
      this->reset(io_service, BOOST_ASIO_MOVE_CAST(Handler)(handler));
    }
  
    // Destructor automatically frees the OVERLAPPED object unless released.
    ~win_iocp_overlapped_ptr()
    {
      reset();
    }
  
    // Reset to empty.
    void reset()
    {
      if (ptr_)
      {
        ptr_->destroy();
        ptr_ = 0;
        iocp_service_->work_finished();
        iocp_service_ = 0;
      }
    }
  
    // Reset to contain the specified handler, freeing any current OVERLAPPED
    // object.
    template <typename Handler>
    void reset(boost::asio::io_service& io_service, Handler handler)
    {
      typedef win_iocp_overlapped_op<Handler> op;
      typename op::ptr p = { boost::asio::detail::addressof(handler),
        boost_asio_handler_alloc_helpers::allocate(
          sizeof(op), handler), 0 };
      p.p = new (p.v) op(handler);
  
      BOOST_ASIO_HANDLER_CREATION((p.p, "io_service",
            &io_service.impl_, "overlapped"));
  
      io_service.impl_.work_started();
      reset();
      ptr_ = p.p;
      p.v = p.p = 0;
      iocp_service_ = &io_service.impl_;
    }
  
    // Get the contained OVERLAPPED object.
    OVERLAPPED* get()
    {
      return ptr_;
    }
  
    // Get the contained OVERLAPPED object.
    const OVERLAPPED* get() const
    {
      return ptr_;
    }
  
    // Release ownership of the OVERLAPPED object.
    OVERLAPPED* release()
    {
      if (ptr_)
        iocp_service_->on_pending(ptr_);
  
      OVERLAPPED* tmp = ptr_;
      ptr_ = 0;
      iocp_service_ = 0;
      return tmp;
    }
  
    // Post completion notification for overlapped operation. Releases ownership.
    void complete(const boost::system::error_code& ec,
        std::size_t bytes_transferred)
    {
      if (ptr_)
      {
        iocp_service_->on_completion(ptr_, ec,
            static_cast<DWORD>(bytes_transferred));
        ptr_ = 0;
        iocp_service_ = 0;
      }
    }
  
  private:
    win_iocp_operation* ptr_;
    win_iocp_io_service* iocp_service_;
  };
  
  } // namespace detail
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // defined(BOOST_ASIO_HAS_IOCP)
  
  #endif // BOOST_ASIO_DETAIL_WIN_IOCP_OVERLAPPED_PTR_HPP
  