Re: allocation of an array

["Davide" <ppp@ppp.it>]

Robert I. Eachus wrote:

> For an Ada beginner, you ask pretty subtle questions!  There are three
> answers to your question.  The first is that yes, you can always count
> on an Ada array being an array, where the data elements are evenly
> spaced.  Beyond that it gets tricky.

[CUT]

> I hope this answer is not overwhelming.  In practice you can ignore all
> of it unless you have to interface with hardware, or with code in some
> other language.

Thank you very much for your exhaustive response, Robert.

I hope not to bother you if I try to explain a little bit better why my
question arose.

First of all I must use the SPARK Ada subset (so no access types, no
unconstrained arrays,...quite nothing...).
My machine is a Power-PC with 32-bit alignment. My compiler is AdaMulti.
I must download long messages composed of 16-bit integers items from a FIFO
memory device.
In my implementation I store them into arrays of 16 bit-integers.
Then I have to filter those buffered messages, extracting a subset of items.
I chosen to use a constant array of offsets for each message (an offset
index for each item to extract).
Then I go through the array extracting items at the specified indexes.
This is my solution, but now I'm wondering if I could have done better if I
had "mapped" a record
to each of those arrays, with 16-bit fields corresponding to the message
items and copying the relevant items to "filtered" records.
That's why I was asking about the array allocation, that is therefore
essential to this solution.

I still hope that the first solution could be preferable...since I have done
a lot of code...  :-) ...what do you think, also in terms of portability and
reusability (i.e independence from platform and compiler, which I like to
take into account)?

Sorry for my bad english,
and thank you for your patience,

Dave