void lock()
            {
                if(try_lock())
                {
                    return;
                }
                long old_count=active_count;
                mark_waiting_and_try_lock(old_count);

                if(old_count&lock_flag_value)
                {
                    bool lock_acquired=false;
                    void* const sem=get_event();

                    do
                    {
                        BOOST_VERIFY(win32::WaitForSingleObject(
                                         sem,::boost::detail::win32::infinite)==0);
                        clear_waiting_and_try_lock(old_count);
                        lock_acquired=!(old_count&lock_flag_value);
                    }
                    while(!lock_acquired);
                }
            }