From: james@sandy.mcci-arl-va.com (Scott James)
Subject: Asynchronous communication between protected types
Date: 1998/07/21
Date: 1998-07-21T00:00:00+00:00 [thread overview]
Message-ID: <6p2cvs$u2$1@client2.news.psi.net> (raw)
I'm trying to connect concurrent objects via an asynchronous
message. I was hoping to do this entirely with protected objects,
however, cannot seem to do so. The difficulty I have is that even if I
put the receiver into a loop (waiting on a send entry) it seems that
*some* task has to start the receiver, so I will still need one (Ada)
task per (active) receiver.
About the best I can come up is the following code.
This is acceptable for my purposes but I was curious if I
could trick this into working using only protected types.
(and without the distribution annex's Asynchronous Pragma
either :-)
(some code snippets borrowed from _Concurrency in Ada (95)_)
-----------------------------------------------------------
with Ada.Text_IO;
procedure Test_Persistent is
type Messages is (Run, Die);
protected type Persistent_Signals is
procedure Send (Message: Messages);
entry Wait (Message: out Messages);
private
Message: Messages;
Signal_Arrived: Boolean:=False;
end Persistent_Signals;
protected body Persistent_Signals is
procedure Send (Message: Messages) is
begin
Persistent_Signals.Message:=Message;
Signal_Arrived:=True;
end Send;
entry Wait (Message: out messages) when Signal_Arrived is
begin
Signal_Arrived:=False;
Message:=Persistent_Signals.Message;
end Wait;
end Persistent_Signals;
type Access_To_Persistent_Signals is access Persistent_Signals;
task type Processes is
entry Initialize (With_Signal: Access_To_Persistent_Signals);
end Processes;
task body Processes is
Message: Messages;
Signal: Access_To_Persistent_Signals;
begin
accept Initialize (With_Signal: Access_To_Persistent_Signals) do
Signal:=With_Signal;
end Initialize;
loop
Signal.Wait (Message);
case Message is
when Run =>
Ada.Text_IO.Put_Line ("I'm running");
when Die =>
exit;
end case;
end loop;
end Processes;
Process: Processes;
Signal: Access_To_Persistent_Signals;
begin
Signal:=new Persistent_Signals;
Process.Initialize (Signal);
for I in 1 .. 4 loop
Signal.Send (Run);
delay 0.5;
end loop;
Signal.Send (Die);
end Test_Persistent;
--
Dr. Scott James james@mcci-arl-va.com
next reply other threads:[~1998-07-21 0:00 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-07-21 0:00 Scott James [this message]
1998-07-22 0:00 ` Asynchronous communication between protected types Anonymous
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox