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From: tgi@tgi2.dev.netgem.com (Tristan Gingold)
Newsgroups: comp.lang.ada
Subject: Re: Variable length raw-byte data
Date: 13 Dec 2000 08:56:32 GMT
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References: <976563484.10868.0.nnrp-01.c1ed21d4@news.demon.co.uk>
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In article <916h4j$egt$1@nnrp1.deja.com>, Robert Dewar wrote:
>In article
><976563484.10868.0.nnrp-01.c1ed21d4@news.demon.co.uk>,
>  "Julian Morrison" <julian.morrison@virgin.net> wrote:
>> I'm trying to shim to a C library that returns some data as a
>length in
>> bytes and a pointer to the first byte. The length is not known
>at compile
>> time. Is there any way I can morph this into an array of mod
>2**8? I'm
>> using the latest Linux GNAT.
>
>
>
>The important thing is to NEVER use pointers to unconstrained
>arrays in such a case. this is asking for non-portable, peculiar
>behavior.
>
>A good type to use in this case is what we in GNAT-land call
>big arrays:
>
>   type byte is mod 2 ** 8;
>
>   type memory is array (natural) of byte;
>   type memptr is access memory;
>
>Now it is almost certainly safe to use address_to_access
>conversions to go between address and memptr.
AFAIR, address_to_access_conversions has only one generic parameter: the
Object.
So, you need to use the access type defined by the package.
Right or wrong ?

Related question: why it is so ? (why AAC doesn't have the same paramaters
as unchecked_conversion ?)

Tristan.