Re: converting - adasockets

[James Rogers <jimmaureenrogers@worldnet.att.net>]

James Rogers wrote:
> 
> Gerald Kasner wrote:
> >
> > "David C. Hoos, Sr." schrieb:
> > >
> > > Assuming the following Ada declarations,
> > > S : String [1 .. 10];
> >
> > This is not an Ada declaration ! (Pascal,Modula-2,Oberon-2...??)
> >
> > > I : Integer;
> > >
> > Why unchecked conversion ?
> 
> Unchecked Conversion is necessary because the data is not a string
> representation of an integer, but an integer value returned as
> a string.  For instance, if the integer is represented as 32 bits,
> the string will be returned as a four byte string. Those four bytes
> need to be interpreted as an integer instead of as a string.
> 
> Ada provides two approaches for solving this problem.
> 
> The first is to use unchecked conversion as described by Mr.
> Hoos. The second is to define a string and an integer to occupy
> the same address. Simply copy the string from Adasockets into
> the overlayed string, then read the value as an integer.
> 
> The C code example used by the original poster showed the C
> equivalent of viewing a string as an integer. There was no conversion
> of values as would occur using the 'value attribute.

A simple example of defining an integer and a string to occupy the
same address follows:

-- Coversion between String and Integer when the string merely contains
-- the bit pattern for the integer, not the character representation
-- of the integer.
--
with Ada.Text_Io;

procedure Memory_Overlay is
   String_Rep : String(1..4);
   Integer_Rep : Integer;
   Num : Integer;

   for String_Rep'Address use Integer_Rep'Address;
begin
   Num := 0;
   while Num < 1024 loop
      Integer_Rep := Num;
      Ada.Text_Io.Put_Line("Integer_Rep:" & Integer'Image(Integer_Rep));
      Ada.Text_Io.Put_Line("String_Rep: " & String_Rep);
      Num := Num + 100;
   end loop;
end Memory_Overlay;

Jim Rogers
Colorado Springs, Colorado USA