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From: "Chad R. Meiners" <crmeiners@hotmail.com>
Newsgroups: comp.lang.ada
Subject: Re: C array to Ada pointer to unconstrained array
 withoutcopyingmemory
Date: Wed, 8 Oct 2003 12:16:34 -0400
Organization: Michigan State University
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"Duncan Sands" <duncan.sands@math.u-psud.fr> wrote in message
news:mailman.49.1065604749.25614.comp.lang.ada@ada-france.org...
> On Wednesday 08 October 2003 00:52, Chad R. Meiners wrote:
> > "Chad R. Meiners" <crmeiners@hotmail.com> wrote in message
> > news:blvfo6$q6s$1@msunews.cl.msu.edu...
> >
> > > declare
> > >     C_Data_Ptr       :  Systems.Address := To_Address(My_C_Ptr);
> > >     C_Data_Length :  Natural   := ...;
> > >
> > >     type My_Ada_Type_Element is ...;
> > >     type My_Ada_Array is array(Natural range <>) of
My_Ada_Type_Element;
> > >
> > >     subtype My_C_Data_As_An_Ada_Array_Type is
> > > My_Ada_Array(1..C_Data_Length);
> > >     package My_Converter is new
> > > Address_To_Access_Conversions(My_C_Data_As_An_Ada_Array_Type);
> > >     C_Data_In_Ada : My_Ada_Array renames
> > > My_Converter.To_Pointer(C_Data_Ptr).all;
> > >     -- No copying of the array done, but the array dope that you want
is
> > > built from the subtype information.
> > > begin
> > > ...
> > > end;
> >
> > I should probably add that you can just get the pointer with
> >
> > My_Ada_Array_Ptr : My_Converter.Object_Pointer :=
> > My_Converter.To_Pointer(C_Data_Ptr);
> >
> > I believe that this satisfies your needs?
>
> Not in the slightest.  Once you leave this local block, the pointer is
> unusable because the array dope, stored as a local variable of the
> block, will disappear.  The data continues to hang around of course.

So do the declare at the library level.

-CRM.