Re: Adding offset to 'Address

["Randy Brukardt" <randy@rrsoftware.com>]

"Kim Rostgaard Christensen" <krc@greenpc.dk> wrote in message 
news:gaqhs6$690$1@jacob-sparre.dk...
> tmoran@acm.org wrote:
>>>  Raw_Bytes : access Unsigned_Char
>>>  for Ethernet_Header'Address use Raw_Bytes.all'Address;
>>>
>>> and additionally need something like:
>>>  for IP_Packet'Address use Raw_Bytes.all'Address + Ethernet_Header'Size;
>>
>> It's not clear to me exactly what problem you are trying to get past.
>
> The problem was basically to perform arithmethics on system addresses

No, that's a (bad) solution to some problem, not a problem by itself. The 
problem seems to be how to access the data bytes without accessing the 
header, and Tom suggests a good solution for that. (We use versions of it in 
Claw.)

IMHO, the use of Address in Ada 95 or newer code (other than to specify raw, 
absolute machine addresses) is never necessary and represents bad 
programming. I see it fairly often here, and it makes me ill. I much prefer 
general access types and possibly Unchecked_Conversions, because you lose 
much less strong typing that way (and the code is better without the need 
for heroic efforts on the part of the compiler).

                                 Randy.


                                          Randy.