Re: Composing tasks and protected objects

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Fri, 05 Aug 2005 19:26:35 +0200, Florian Weimer wrote:

> Suppose I want to write a selective accept which reads messages from a
> queue, and also support a special entry call to reload the
> configuration.
> 
> Conceptually, this would look like this:
> 
>    task Server is
>       entry Reload_Configuration (Config : Config_Template);
>       entry Shut_DOwn;
>    end Server;
> 
>    task body Server is
>       Current_Message : Message;
> 
>    begin
>       loop
>          select
>             Get (Queue, Current_Message);
>             Process_Message (Current_Message);
> 
>          or
>             accept Reload_Configuration (Config : Config_Template) do
>                Process_Reload (Config);
>             end Reload_Configuration;
> 
>          or
>             accept Shut_Down;
>             exit;       -- Premature shut down requested
> 
>          or
>             terminate;  -- Normal shutdown at end of scope
>          end select;
>       end loop;
>    end Server;

You could make "Reload_Configuration" and "Shut_Down" messages rather than
entries. Of course only if you don't need to wait for their completion.
Otherwise you are going to mix synchronous calls with fire-and-forget
messaging. It is always difficult.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de