Re: Ada.Storage_IO. Anyone use it?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Sat, 9 Jun 2012 01:06:35 -0700 (PDT), Micronian Coder wrote:

> I was looking through the Ada RM and came across the generic package
> Ada.Storage_IO. I'm not sure what the benefits are to using it. It states
> that it could automatically flatten out the data representation if
> necessary. For example, say a discriminant record has an array field that
> is sized based on the discriminant value:
> 
> type Buffer(Length : Positive) is
>     record
>        Bytes: Byte_Array(1 .. Length);
>     end record;

You cannot instantiate Ada.Storage_IO with this type, because Buffer is
indefinite. But since Ada.Storage_IO look totally useless (see A.9(11),
too!) anyway...
 
> Did anyone find this package useful in practice rather than define their
> own IO routines (e.g. define stream operations to read and write their
> data)?

1. For specifically storage I/O I am using memory pools. Instead of Write I
do "new", instead of Read I use an access type. This is cleaner, more
efficient, and no generics involved.

   = Pool, backed by a container, e.g. a segmented memory stack

2. For data exchange I am using streams. I always redefine stream
operations because built-in ones are unusable for data exchange, which
dictates certain representation. Again, no generics, no any limitations of
elements, reusable with different stream backends.

   = Stream, backed by a container.

It is worth to mention that there are three major distinct cases, which get
permanently confused in the context of I/O:

A. Marshaling objects (true I/O, persistency, serialization)
B. Formatted I/O and rendering (dealing with human readable
representations)
C. Garbage collection of objects (e.g. arena allocators etc)

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de