Class basic_future

extern/boost/boost/thread/future.hpp:1330–1522

      /// Common implementation for future and shared_future.
      template <typename R>
      class basic_future : public base_future
      {
      protected:
      public:

        typedef boost::shared_ptr<detail::shared_state<R> > future_ptr;
        typedef typename detail::shared_state<R>::move_dest_type move_dest_type;

        static //BOOST_CONSTEXPR
        future_ptr make_exceptional_future_ptr(exceptional_ptr const& ex) {
          return future_ptr(new detail::shared_state<R>(ex));
        }

        future_ptr future_;

        basic_future(future_ptr a_future):
          future_(a_future)
        {
        }

      public:
        typedef future_state::state state;

        BOOST_THREAD_MOVABLE_ONLY(basic_future)
        basic_future(): future_() {}


        //BOOST_CONSTEXPR
        basic_future(exceptional_ptr const& ex)
          : future_(make_exceptional_future_ptr(ex))
        {
        }

        ~basic_future() {
        }

        basic_future(BOOST_THREAD_RV_REF(basic_future) other) BOOST_NOEXCEPT:
        future_(BOOST_THREAD_RV(other).future_)
        {
            BOOST_THREAD_RV(other).future_.reset();
        }
        basic_future& operator=(BOOST_THREAD_RV_REF(basic_future) other) BOOST_NOEXCEPT
        {
            future_=BOOST_THREAD_RV(other).future_;
            BOOST_THREAD_RV(other).future_.reset();
            return *this;
        }
        void swap(basic_future& that) BOOST_NOEXCEPT
        {
          future_.swap(that.future_);
        }
        // functions to check state, and wait for ready
        state get_state(boost::unique_lock<boost::mutex>& lk) const
        {
            if(!future_)
            {
                return future_state::uninitialized;
            }