Re: C-style 'union' in Ada?

["Brian Catlin" <briancatlin@mindspring.com>]

"David Brown" <davidb@davidb.org> wrote in message news:WUXe7.15629$ZM2.1376965@newsread2.prod.itd.earthlink.net...
> Ted Dennison <dennison@telepath.com> wrote:
> > In article <9l7qon$d78$1@nntp9.atl.mindspring.net>, Brian Catlin says...
> >>
> >>I'm still trying to get both lobes around the Ada paradigm.  I have a
> >>record that I want to hold a pointer to a buffer which is either a String
> >>or Wide_String, but I don't want to statically declare which, so using a
> >>variant record won't work (at least given my understanding).  Likewise, I
> >>don't want to have two record definitions, one for String, and one for
> >>Wide_String.  In the package I'm designing, I don't care whether it is a
> >>String or Wide_String, I will just pass it to the file I/O packages
> >>(stream, in this case).  In C, I would:
>
[...snip...]
>
> I have recently encountered a concrete example of the need for something
> like this.  The application is storing variable sized data fields in fixed
> length records (say disk sectors).  The block is defined as a large string.
> The beginning of the block contains lengths for each of the variable sized
> fields.  The data items start at the end of the record and work their way
> backward.
>
> Basically, there are two different views of the block and the boundary
> between them depends on the sizes of the data items.
>
> Unchecked conversions of access values seems to be the easiest way to deal
> with this.

This is very similar to what I'm doing.  I was trying to avoid unchecked conversion.  I had assumed that there would be a better
way.

 -Brian