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From: "Nick Roberts" <Nick.Roberts@dial.pipex.com>
Subject: Re: question re Ada equivalent of C function
Date: 1998/02/22
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References: <34EEFF9C.1D01FA5D@stellar1.com>
 <6cnj5d$bjq$1@usenet.rational.com>
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Date: 1998-02-22T00:00:00+00:00
List-Id: <comp.lang.ada>


Again, this kind of technique is specific to those architectures with
memory-mapped ports, and even so, there could well be further ramifications
(e.g. access rights, interference, etc.).

It also assumes that an access value is the same as an address: this is not
always so! For fooling around in memory, you're better off using the
facilities provided by the standard packages System.Storage_Elements (RM
13.7.1) and System.Address_To_Access_Conversions (RM 13.7.2).

(I always think it's slightly biblical, quoting chapter-and-verse like that
;-)


== Nick Roberts ================================================
== Croydon, UK                       ===========================
==                                              ================
== Proprietor, ThoughtWing Software                   ==========
== Independent Software Development Consultant            ======
== Nick.Roberts@dial.pipex.com                              ====
== Voicemail & Fax +44 181-405 1124                          ===
==                                                            ==
==           I live not in myself, but I become               ==
===          Portion of that around me; and to me             ==
====         High mountains are a feeling, but the hum        ==
=======      Of human cities torture.
===========                             -- Byron [Childe Harold]


Corey Ashford <yeroca7@rocketmail.com> wrote in article
<6cnj5d$bjq$1@usenet.rational.com>...
> 
> David Fisher wrote in message <34EEFF9C.1D01FA5D@stellar1.com>...
> >Sorry if this is a bit basic, but learning Ada on one's own can be, er,
> >challenging.
> >
> >What are the Ada equivalents of the C functions, inp and outp, used to
> >read a byte from or send one to a memory address?
> >
> >Thanks!
> >
> >David Fisher
> >Fisher Research Corporation
> >
> 
> There are a number of ways to do this in Ada.  Here's one fairly simple
one:
> 
> with unchecked_conversion;
> with system;
> 
> type byte is mod 2*8;
> type byte_access is access byte;
> function to_byte_access is new unchecked_conversion(system.address,
> byte_access);
> 
> function inp(addr: system.address) return byte is
> begin
>     return to_byte_access(addr).all;
> end inp;
> 
> procedure outp(addr: system.address; value: byte) is
> begin
>     to_byte_access(addr).all := value;
> end outp;