Re: Stream_Element_Array

[Alexander Korolev <antonovkablog@gmail.com>]

On Sep 15, 12:20 pm, "Dmitry A. Kazakov" <mail...@dmitry-kazakov.de>
wrote:
> On Wed, 14 Sep 2011 14:29:41 -0700 (PDT), Alexander Korolev wrote:
> > "In your case the other end is not the memory but the wire"
> > I am not sure I undestand you complitly. What's wrong, at least for
> > now, to build \ construct in memory the Buffer (Stream_Element_Array)
> > with full command (according the format I posted) inside and after
> > that send it over any stream (including GNAT.Serial, Socket etc)
> > derived from Root_Stream_Type. Basicly, I don't need even a Type -
> > I am using it just get Unsigned_16 serialized into Stream Elements.
>
> Yes, but in most cases it does not work so straightforwardly. You usually
> need headers, checksums etc. The point is that you have more layers of the
> protocol than just raw values over stream of octets. This is why you use
> stream rather as a transport for packets/messages and often more upper
> levels too (state machine etc). The idea is to always encapsulate each
> level into a data type. It saves much time later.
>
> > That's it. It's kind of hadcrafting. I also can override My_Type'Write
> > attribute and send to Serial port ... Your approach is to create a new
> > stream actully, which will take into account the PROTOCOL specifics.
> > Absolutly agree with that. But what is wrong with manual approach I am
> > implementing.
>
> It is not wrong, it is just might not work because protocols are more
> complex (layered) than this simple model.
>
> --
> Regards,
> Dmitry A. Kazakovhttp://www.dmitry-kazakov.de

1. Can not disagree again - layers, state machines is "must" part.
2. So far got some interim results with serialization of the Type
   in Volatile Stream. The Last set to 3? It looks I am getting
   there but no confidence so far.


type Message_Length is
      record
         Lenght:Interfaces.Unsigned_16 :=
Interfaces.Unsigned_16(256);
      end record;
-------------

procedure length_test is
   V1  : aliased Volatile_Streams.Memory_Resident_Stream (Size =>
1024);
   Temp_Stream_Element        :Stream_Element;
   Message_Length_Instance   :Message_Length;
   Message_Lenght_Elements :Stream_Element_Array(1..4);

   begin
   Message_Length'Write(V1'Access,Message_Length_Instance);
   -- Write into and serialize into in - memory stream
Message_Length_Instance
   read (V1, Message_Lenght_Elements, Last);
   -- Read  out in-memry stream. Assigns  Message_Lenght and Last
   for J in Message_Lenght_Elements'First .. Last loop
      Temp_Stream_Element   := Message_Lenght_Elements(J);
       Put_Line( Temp_Stream_Element'Img);
   end loop;
   Put_Line( "Last");
   Put_line (Last'Img);
   -- print out the Last
end;

with Lenght:Interfaces.Unsigned_16 :=    Interfaces.Unsigned_16(255);
-- output
../development/projects/length_test
 255
 0
 0
Last
 3
[2011-09-15 11:26:32] process terminated successfully (elapsed time:
00.13s)

with Lenght:Interfaces.Unsigned_16 :=    Interfaces.Unsigned_16(256);
--output
../development/projects/length_test
 0
 1
 0
Last
 3
[2011-09-15 11:43:12] process terminated successfully (elapsed time:
00.13s)