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From: joseph_kwan@greenlime.com (Joseph Kwan)
Newsgroups: comp.lang.ada
Subject: Re: How to convert record?
Date: 28 Oct 2001 17:42:41 -0800
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"David C. Hoos" <david.c.hoos.sr@ada95.com> wrote in message news:<mailman.1004014002.9071.comp.lang.ada@ada.eu.org>...
> Presumably, you know the size of the record.  In your original post
> you showed a record with 8 bytes.
> 
> So, you would declare a constrained string subtype of the correct size
> e.g., subtype Record_String is POSIX.POSIX_String (1 .. 8);
> 
> Now you can instantiate Unchecked_Conversion from the Record to
> Record_String,   because Record_String is constrained.
> 
> A Record_String is a valid buffer to pass to POSIX.IO.Read.


So, it must be a constrained type/subtype. This solve my problems.
Thanks.

OTOH, I read about 13.13.2 Stream-Oriented Attributes in LRM. Can I
use 'Read and 'Write or 'Input and 'Output for [this] purpose?

Can someone please explain in details (an example of the
implementation will be of great help) how to implement these
attributes? Please forgive my stupidity because I can't find a good
examples of such implementation in books and LRM and certainly am
unable to figure it out.

Thank you.





> >
> > I thought that would work too but theoretically,
> > Ada.Unchecked_Conversion will not work in converting record to
> > POSIX.IO.IO_Buffer which is a string of characters (See spec in
> > florist's implementation).
> >
> > Anyhow I tried to do Unchecked_Conversion and gnat gave me error
> > message:
> >
> > "unchecked conversion to unconstrained array not allowed".