Re: Porting from Modula-2 to Ada

["SteveD" <nospam_steved94@attbi.com>]

"Manuel Collado" <m.collado@lml.ls.fi.upm.es> wrote in message
news:3DAFC542.152C0EE0@lml.ls.fi.upm.es...
[snip]
> So far, my only porting scheme is to replace ARRAY OF BYTE parameters by
> the pair (address, size), as follows:
>
>    procedure Xxx (Raw_Address: System.Address; Raw_Size: Integer) ...
>
>    Num: Integer;
>    ...
>       Xxx (Num'Address, Num'Size);
>    ...
>
> But this requires recoding every call to the procedure. Is there another
> way to pass raw data without having to recode every call?

First: I have translated a significant amount of Pascal code to Ada.  From
this experience I would recommend producing a tool to do most of the
translation.

Making the mapping you just described should be fairly easy for such a tool.

The only alternate for this implementation that comes to mind is to create
arrays of bytes that alias each structure and passing the alias to Xxx.  For
example:

with Interfaces; use interfaces;
with Ada.Text_Io;

procedure testconv is

  type byte_array is array( Natural range <> ) of Unsigned_8;

  type data_rec is
    record
      field_1 : Integer;
      field_2 : String( 1 .. 8 );
    end record;

  procedure Xxx( raw : in out byte_array ) is
  begin
    raw( 0 ) := 2;
    raw( 1 ) := 0;
    raw( 2 ) := 0;
    raw( 3 ) := 0;
  end Xxx;

  data : data_rec;
  data_alias : byte_array( 0 .. data_rec'size / 8 - 1 );
  for data_alias'address use data'address;
begin
  data.field_1 := 1;
  Ada.Text_Io.Put_Line( "field_1 before: " & Integer'IMAGE(
data.field_1 ) );
  Xxx( data_alias );
  Ada.Text_Io.Put_Line( "field_1 after: " & Integer'IMAGE( data.field_1 ) );
end testconv;

This makes the code look more like the original source, but requires an
additional declaration for each parameter passed to Xxx and still requires
the calls to be modified.

Sorry I don't have a better answer,

SteveD
>
> Thanks.
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