Re: Help with Copying Shared Memory to Local

["John Cupak" <Jcupak744@attbi.com>]

Jeffrey,

What a refreshing solution!

I don't know why they're using pointers or addresses, either. Probably, as
you noted, a C-hacker
trying to write Ada.

I've forwarded your suggested solution to the maintenance programmer who
brought the problem
to my attention. Let's see if it flys.

Thanks again - Occam's razor strikes again!

John
"Jeffrey Carter" <jrcarter@acm.org> wrote in message
news:3CED51CF.39E26FC6@acm.org...
> John Cupak wrote:
> >
> > A colleague asked me to help him solve an memory copy problem.
> >
> > The source memory location is in a "shared" area, and the
> > destination memory location is "local" to the application.
> >
> > The original code, written in Ada83, works by copying two bytes
> > at a time. Evidently, the hardware crashes if they try to access
> > a single byte.
> >
> > Here's the Ada 95 version of the original Ada83 code:
> >
> > -- Assumed visibility of Project_Types
> > procedure Copy_Double_Byte(Destination : in System.Address;
> >                            Source      : in System.Address;
> >                            Length      : in Natural) is
>
> There's about a 9 out of 10 chance that this system does not need to be
> dealing with addresses; that this way of doing things was dreamed up by
> a C person who lacked the necessary familiarity with Ada 83 to be
> competent to create this specification. I have seen this kind of misuse
> of the language far too many times for it to be likely that this case is
> different.
>
> You rarely need to use addresses in Ada; this particular example almost
> certainly did not need to use addresses even in Ada 83. Maybe you're
> stuck with it, in which case you can probably do
>
> Storage_Length : constant Storage_Count :=
>    Storage_Count ( (8 * Length + Storage_Unit - 1) / Storage_Unit);
> -- Convert Length (in 8-bit bytes) to work with Storage_Elements
>
> A : Storage_Array (1 .. Storage_Length);
> for A'Address use Destination;
> pragma Import (Ada, A);
>
> B : Storage_Array (1 .. Storage_Length);
> for B'Address use Source;
> pragma Import (Ada, B);
>
> ...
>
> A := B;
>
> --
> Jeff Carter
> "We call your door-opening request a silly thing."
> Monty Python & the Holy Grail