On 04/08/2017 03:05 AM, Jeremiah Breeden wrote: > I was trying to figure out how Connection_Data is handled with respect to > Task > safety. In particular, if I have two Action_Event handlers and in each of > the I > do something like: > > My_App : My_App_Access := My_App_Access(Object.Connection_Data); > > And then proceed to use it in both action event handlers, how does Gnoga > prevent > the two handlers from having concurrency issues with what My_App points to?
This is only an issue if the events are both from the same connection. If the events are from different connections, then the pointers are different and you don't have to worry about it. Multi-connect programs would be difficult to implement if this wasn't the case. Since events are really user interactions with the Gnoga GUI, and computers are much faster than people, this is not a concern for most programs. However, Gnoga seems to respond to a user interaction by creating a task which calls the appropriate event handler. If the processing of one event can take long enough that the user can generate another event, then this can become an issue. I encountered this when porting Mine_Detector to Gnoga. The responses to some events at some points in the game took seconds, and it was easy to generate a 2nd event which would interfere with the 1st and result in an invalid game state. My solution was for all event handlers to call a protected entry, serializing the event handling. I used an entry with a barrier of True rather than a protected procedure so the calls would be queued and handled in the correct order. My solution is really for the singleton case, though. In the multi-connect version, all the event handlers are going through the same entry, so an event has to wait for all other players' events to complete before being processed. The multi-connect version should really have a protected object per connection. You can see the Mine_Detector code in Gnoga's demo directory. -- Jeff Carter "C++ is vast and dangerous, a sort of Mordor of programming languages." Jason R. Fruit 120 ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Gnoga-list mailing list Gnoga-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/gnoga-list
