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From: mheaney@on2.com (Matthew Heaney)
Newsgroups: comp.lang.ada
Subject: Re: dynamic multithreading
Date: 20 Nov 2002 10:20:11 -0800
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"Grein, Christoph" <christoph.grein@eurocopter.com> wrote in message news:<mailman.1037689022.2833.comp.lang.ada@ada.eu.org>...
> > http://www.adapower.com/alg/smartp.html
> 
> There is another implementation of referece counted pointers, Safe_Pointers, in my home 
> page. This has been published in Ada Letters some years ago.
> 
> See http://home.T-Online.de/home/Christ-Usch.Grein/Ada/

The package Charles.Access_Control provides an abstraction very
similar to an auto_ptr in C++.

The idea is that someone always "owns" a pointer, and it's up to the
owner to Free the object.

In the case of Access_Control, the Pointer_Type can be used as an
owner, presumably in a temporary scope.  This means that no matter how
you exit the scope (say, an unhandled exception), you have a guarantee
that the memory get free'd.

For example:

function Factory_Function return T_Access is

   Pointer : T_Access_Control.Pointer_Type;
   
begin
   
   Initialize (Pointer, new T);

   --do some stuff that might raise an exception, etc

   --ok, we're all done, transfer ownership to caller
   return Release (Pointer);

end Factory_Function;


I put up a new version (20021119) of Charles last night (I added a
bounded vector container, and generalized the Access_Control package):

http://home.earthlink.net/~matthewjheaney/charles/index.html