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From: Anton Gibbs <agibbs@dera.gov.uk>
Subject: Re: Use of C.Strings.Value Function Considered Harmful
Date: 1999/12/06
Message-ID: <384B907C.6583@dera.gov.uk>#1/1
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References: <3847E5CE.4F9E@dera.gov.uk> <829115$b6h$1@hobbes2.crc.com>
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Date: 1999-12-06T00:00:00+00:00
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David C. Hoos, Sr. wrote:

> You can use the function Interfaces.C.To_Ada, to convert the char_array
> result of the function from B.3.1 (35) to an Ada String.

> Read the manual??

I am just baffled by how unhelpful the Length parameter is in:

     function Value( Item : in chars_ptr; Length : in size_t )
              return String;  -- B3.1(39)

As far as I can tell (from reading the manual, funny enough), if the
designated string contains fewer than `Length' characters before its
first null, then it returns a string of length < `Length' otherwise it
raises Terminator_Error.

What I have ended up doing (as David C. Hoos, Sr. suggests) is to call:

     function Value (Item : in chars_ptr; Length : in size_t)
              return char_array;  -- B3.1(35)

and then append a (sometimes superfluous) ASCII.nul before calling
C_To_Ada with Trim_Null set to True. I would have liked a single call to
Value to do all this for me; afterall, what I am trying to do here is
not that unusual is it ?

Thanks.

Best -- Anton.

-- 
Civil Air Traffic Management Group
Defence Evaluation and Research Agency
Bedford, UK

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