text: //
  // detail/reactive_socket_recvfrom_op.hpp
  // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  //
  // Copyright (c) 2003-2011 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_REACTIVE_SOCKET_RECVFROM_OP_HPP
  #define BOOST_ASIO_DETAIL_REACTIVE_SOCKET_RECVFROM_OP_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/utility/addressof.hpp>
  #include <boost/asio/detail/bind_handler.hpp>
  #include <boost/asio/detail/buffer_sequence_adapter.hpp>
  #include <boost/asio/detail/fenced_block.hpp>
  #include <boost/asio/detail/reactor_op.hpp>
  #include <boost/asio/detail/socket_ops.hpp>
  
  #include <boost/asio/detail/push_options.hpp>
  
  namespace boost {
  namespace asio {
  namespace detail {
  
  template <typename MutableBufferSequence, typename Endpoint>
  class reactive_socket_recvfrom_op_base : public reactor_op
  {
  public:
    reactive_socket_recvfrom_op_base(socket_type socket, int protocol_type,
        const MutableBufferSequence& buffers, Endpoint& endpoint,
        socket_base::message_flags flags, func_type complete_func)
      : reactor_op(&reactive_socket_recvfrom_op_base::do_perform, complete_func),
        socket_(socket),
        protocol_type_(protocol_type),
        buffers_(buffers),
        sender_endpoint_(endpoint),
        flags_(flags)
    {
    }
  
    static bool do_perform(reactor_op* base)
    {
      reactive_socket_recvfrom_op_base* o(
          static_cast<reactive_socket_recvfrom_op_base*>(base));
  
      buffer_sequence_adapter<boost::asio::mutable_buffer,
          MutableBufferSequence> bufs(o->buffers_);
  
      std::size_t addr_len = o->sender_endpoint_.capacity();
      bool result = socket_ops::non_blocking_recvfrom(o->socket_,
          bufs.buffers(), bufs.count(), o->flags_,
          o->sender_endpoint_.data(), &addr_len,
          o->ec_, o->bytes_transferred_);
  
      if (result && !o->ec_)
        o->sender_endpoint_.resize(addr_len);
  
      return result;
    }
  
  private:
    socket_type socket_;
    int protocol_type_;
    MutableBufferSequence buffers_;
    Endpoint& sender_endpoint_;
    socket_base::message_flags flags_;
  };
  
  template <typename MutableBufferSequence, typename Endpoint, typename Handler>
  class reactive_socket_recvfrom_op :
    public reactive_socket_recvfrom_op_base<MutableBufferSequence, Endpoint>
  {
  public:
    BOOST_ASIO_DEFINE_HANDLER_PTR(reactive_socket_recvfrom_op);
  
    reactive_socket_recvfrom_op(socket_type socket, int protocol_type,
        const MutableBufferSequence& buffers, Endpoint& endpoint,
        socket_base::message_flags flags, Handler& handler)
      : reactive_socket_recvfrom_op_base<MutableBufferSequence, Endpoint>(
          socket, protocol_type, buffers, endpoint, flags,
          &reactive_socket_recvfrom_op::do_complete),
        handler_(BOOST_ASIO_MOVE_CAST(Handler)(handler))
    {
    }
  
    static void do_complete(io_service_impl* owner, operation* base,
        const boost::system::error_code& /*ec*/,
        std::size_t /*bytes_transferred*/)
    {
      // Take ownership of the handler object.
      reactive_socket_recvfrom_op* o(
          static_cast<reactive_socket_recvfrom_op*>(base));
      ptr p = { boost::addressof(o->handler_), o, o };
  
      BOOST_ASIO_HANDLER_COMPLETION((o));
  
      // 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.
      detail::binder2<Handler, boost::system::error_code, std::size_t>
        handler(o->handler_, o->ec_, o->bytes_transferred_);
      p.h = boost::addressof(handler.handler_);
      p.reset();
  
      // Make the upcall if required.
      if (owner)
      {
        fenced_block b(fenced_block::half);
        BOOST_ASIO_HANDLER_INVOCATION_BEGIN((handler.arg1_, handler.arg2_));
        boost_asio_handler_invoke_helpers::invoke(handler, handler.handler_);
        BOOST_ASIO_HANDLER_INVOCATION_END;
      }
    }
  
  private:
    Handler handler_;
  };
  
  } // namespace detail
  } // namespace asio
  } // namespace boost
  
  #include <boost/asio/detail/pop_options.hpp>
  
  #endif // BOOST_ASIO_DETAIL_REACTIVE_SOCKET_RECVFROM_OP_HPP
  