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From: Stephen Leake <stephen_leake@stephe-leake.org>
Newsgroups: comp.lang.ada
Subject: Re: Return unconstrained types in ZFP
References: <3254b304-ed8b-4601-8a3c-ab3df74d84ad@googlegroups.com>
Date: Mon, 03 Dec 2012 07:25:41 -0500
Message-ID: <85boebuxtm.fsf@stephe-leake.org>
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Date: 2012-12-03T07:25:41-05:00
List-Id: <comp.lang.ada>

"Rego, P." <pvrego@gmail.com> writes:

> I am trying to implement, for an ATmega2560 (Arduino Mega) micro-controller using ZFP in GNAT-AVR, an USART unconstrained Get string like
>       function Get (Port : USART_Port_Type; Size : Unsigned_8) return
>       String_U8;

Is "Size" a maximum here, or is the result expected to be exactly Size
bytes long?

Another alternative is to use a procedure:

      procedure Get 
         (Port      : in USART_Port_Type; 
          Data      :    out String_U8; 
          Data_Last :    out Unsigned_8);

Then the user must allocate space for Data:

declare
   Data      : String_U8 (1 .. Size);
   Data_Last : Unsigned_8;
begin
   Get (Port, Data, Data_Last);
   ... use Data
end;

This way, you don't need to implement the runtime code.

It is more of a burden for the user, but that's the point of ZFP; it's
easier to implement, harder to use.

-- 
-- Stephe