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From: jsanchor@my-dejanews.com
Subject: Access types
Date: 1998/05/27
Message-ID: <6khbm1$ec1$1@nnrp1.dejanews.com>#1/1
X-Deja-AN: 356871308
Organization: Deja News - The Leader in Internet Discussion
X-Article-Creation-Date: Wed May 27 15:32:17 1998 GMT
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Newsgroups: comp.lang.ada
Date: 1998-05-27T00:00:00+00:00
List-Id: <comp.lang.ada>


HI, I am working with access types and have a challenge at hand which I seem
to be losing. Need some help. I have data in Non Volatile Memory and RAM that
I need to access using access types. The problem is I need to have the same
"types" to work on the data, ie compare them, calculate checksum, etc.
ex. I have a package that looks like this:
-------------NVM--------------------------------------
type Non_Volatile_Type is tagged private;

type Ptr_to_Non_Volatile_Type is access all Non_Volatile_Type'class;

????Ptr_to_Data : access Non_Volatile_Type'Class?????;

type Information_Record_Type is
record
    Tag_Part   : Tag;
    NVM_Access : Ptr_to_Data???;
    RAM_Access : Ptr_to_Data???;
end record;

procedure Compute_Checksum (block : ???Ptr_to_Data);
           or
procedure Compute_Checksum (block : ???access Non_Volatile_Type'Class);

private

   type Non_Volatile_Type is tagged
      record
         checksum : Storage_Element;
      end record;

Somebody trying to use my package will declare a package somewhat like this
---------------------USER Spec------------------------------------
  type List_NVM_Type is new ddNVM.Non_Volatile_Type with
  record
     word1 : INTEGER := 8;
  end record;
---------------------USER Body------------------------------------
   procedure test is
      my_nvm : aliased List_NVM_Type;
   begin

      ddNVM.Compute_checksum(my_nvm'access);
   end test;

Does anybody know of a way. Thanks in advance.

sincerely,
Jay Sanchorawala.










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