Boost C++ Libraries

boost/asio/detail/completion_handler.hpp

//
// completion_handler.hpp
// ~~~~~~~~~~~~~~~~~~~~~~
//
// Copyright (c) 2003-2010 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_COMPLETION_HANDLER_HPP
#define BOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP

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

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

#include <boost/asio/detail/fenced_block.hpp>
#include <boost/asio/detail/handler_alloc_helpers.hpp>
#include <boost/asio/detail/handler_invoke_helpers.hpp>
#include <boost/asio/detail/operation.hpp>

namespace boost {
namespace asio {
namespace detail {

template <typename Handler>
class completion_handler : public operation
{
public:
  completion_handler(Handler h)
    : operation(&completion_handler::do_complete),
      handler_(h)
  {
  }

  static void do_complete(io_service_impl* owner, operation* base,
      boost::system::error_code /*ec*/, std::size_t /*bytes_transferred*/)
  {
    // Take ownership of the handler object.
    completion_handler* h(static_cast<completion_handler*>(base));
    typedef handler_alloc_traits<Handler, completion_handler> alloc_traits;
    handler_ptr<alloc_traits> ptr(h->handler_, h);

    // Make the upcall if required.
    if (owner)
    {
      // 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(h->handler_);
      ptr.reset();
      boost::asio::detail::fenced_block b;
      boost_asio_handler_invoke_helpers::invoke(handler, handler);
    }
  }

private:
  Handler handler_;
};

} // namespace detail
} // namespace asio
} // namespace boost

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

#endif // BOOST_ASIO_DETAIL_COMPLETION_HANDLER_HPP