From: William FRANCK <william.franck@free.fr>
Subject: Re: How to transfer Class-Wide object to a Task ?
Date: Mon, 14 Oct 2019 22:21:48 +0200
Date: 2019-10-14T22:21:48+02:00 [thread overview]
Message-ID: <5da4d8dc$0$20339$426a74cc@news.free.fr> (raw)
In-Reply-To: 5da4cf81$0$20312$426a74cc@news.free.fr
On 2019-10-14 19:41:53 +0000, William FRANCK said:
> Hey all !
> Here is a nice issue I have with Ada (GNAT 2012) when trying to do OO
> dispatching with streams in different tasks ...
>
> Here it is :
> I'd like to get from a task RdV (Entry-Access) an object which could be
> any subclass of a root'Class, and pass it to another task
>
> Context : read (Root'Class'Input() ) tagged records from an input
> stream, and send them to anther task which will write
> (Root'Class'Output() ) the given records to another output stream.
>
> I'm stuck with task memory isolation with does NOT allow to pass any
> access object to a Root'Class.
>
> Should I try to use a protected object ?
> (not shore this solves the passing of a Class-wide object ...)
>
> Thanks for your feed-back,
> William
Here is some code to illustrate
(code needs soem fixings)
with
Ada.Text_io;
procedure main_ClassWide_to_2Task is
type Geo2D is tagged record
Y, X : integer;
Name : String(1..6) := "Object";
end record;
type Circle is new Geo2D with record
Radius : integer;
end record;
myObject : access Geo2D'Class;
-- ==============================
task reading is
entry Object(This : in out Geo2D'Class);
entry Stop;
end reading;
task writing is
entry Object(This : in Geo2D'Class);
entry Stop;
end writing;
-- ==============================
task body reading is
O2D : access Geo2D'Class;
begin
loop
select
accept Object(This : in out Geo2D'Class);
declare
-- (shortcut to simulate real case) :: Object :
constant Geo2D'Class := Dispatching_Input (Ada.Tags.Internal_Tag
(External_Tag), Stream);
begin
O2D := new Circle'(0,0,"Cercle",10);
Ada.Text_io.Put_line("Reading 2D Object: " & O2D.Name);
-- debug trace
-- This.all := O2D.all; --Compiler error : "This" is undefined
end;
or
accept Stop;
exit;
end select;
end loop;
end reading;
-- ==============================
task body writing is
myObject : access Geo2D'Class;
begin
loop
select
accept Object(This : in Geo2D'Class) do
myObject := This'Access;
end Object;
Ada.Text_io.Put_line("Writing 2D Object: " & This.Name); --
debug trace
or
accept Stop;
exit;
end select;
end loop;
end writing;
-- ==============================
begin
reading.Object(myObject.all);
writing.Object(myObject.all);
reading.Stop;
writing.Stop;
end main_ClassWide_to_2Task;
next prev parent reply other threads:[~2019-10-14 20:21 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-14 19:41 How to transfer Class-Wide object to a Task ? William FRANCK
2019-10-14 19:55 ` Shark8
2019-10-14 20:48 ` William FRANCK
2019-10-14 22:01 ` Shark8
2019-10-15 5:13 ` William FRANCK
2019-10-14 19:58 ` Dmitry A. Kazakov
2019-10-14 20:58 ` William FRANCK
2019-10-15 4:40 ` Per Sandberg
2019-10-15 5:40 ` William FRANCK
2019-10-16 20:04 ` William FRANCK
2019-10-16 23:43 ` Anh Vo
2019-10-17 9:28 ` William FRANCK
2019-10-17 10:00 ` Dmitry A. Kazakov
2019-10-17 10:45 ` William FRANCK
2019-10-15 7:21 ` Dmitry A. Kazakov
2019-10-15 14:31 ` Optikos
2019-10-15 19:41 ` William FRANCK
2019-10-15 20:03 ` Shark8
2019-10-14 20:21 ` William FRANCK [this message]
2019-10-14 20:32 ` Dmitry A. Kazakov
2019-10-14 21:04 ` William FRANCK
2019-10-14 21:57 ` Shark8
2019-10-15 5:43 ` William FRANCK
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