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Newsgroups: comp.lang.ada
Subject: Re: Interfacing to C: big structures
References: 
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 <wccskzgob43.fsf@shell01.TheWorld.com>
From: Stephen Leake <stephen_leake@stephe-leake.org>
Date: Tue, 26 Feb 2008 08:53:14 -0500
Message-ID: <uhcfvvn79.fsf@stephe-leake.org>
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Date: 2008-02-26T08:53:14-05:00
List-Id: <comp.lang.ada>

Robert A Duff <bobduff@shell01.TheWorld.com> writes:

> Maciej Sobczak <see.my.homepage@gmail.com> writes:
>
>> Consider the C API that contains some structure S and a couple of
>> functions that operate on the state that is stored in the Struct. A
>> typical usage in C might be:
>>
>> struct S s;
>>
>> init(&s);
>> foo(&s);
>> bar(&s);
>> baz(&s);
>>
>> Above, s is created with automatic storage duration.
>>
>> How to interface to this from Ada? I see two options:
>
> Something like:
>
>     type S is record ... end record;
>     pragma Convention (C, S);
>     
>     X : aliased S;
>     init (X'Access); -- or possibly 'Unchecked_Access
>     foo (X'Access); -- or ...

Why not:

procedure Init (X : in out S);
procedure Foo (X : in out S);

begin
    init (X);
    foo (X);
end;

-- 
-- Stephe