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Date: Mon, 06 Jun 2011 13:16:03 +0200
From: Georg Bauhaus <rm.dash-bauhaus@futureapps.de>
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Subject: Re: Reading the while standard input into a String
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Date: 2011-06-06T13:16:04+02:00
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On 05.06.11 18:20, Natasha Kerensikova wrote:
> Hello,
> 
> I have encountered what was a very easily solved problem in C: dump the
> whole contents of the standard input into some place in memory, in order
> to process it afterwards.

To use something like C's fread(1), I'd do the same in Ada with
Streams and Storage_Element_Array.  Like fread, which has void*
arguments, the Ada equivalent will read storage elements (bytes,
likely octets).

Very likely, the storage elements can be converted to Character
without check, i.e. using an instance of Unchecked_Conversion,
or simple the 'Address attribute.  So no copying is involved
at this stage.

When processing Input character by character, no I/O is
performed.


I define an index for the characters in the storage area
so filled:

declare
    Buffer : Storage_Element_Array (...);
    Input : String (Buffer'Range);
    pragma Import (Ada, Input);
    for Input'Address use Buffer'Address;

    Last : Natural;  -- index of last octed
    Pos : Positive;  -- points to current character

begin
    --  have standard input flow into Buffer from a text stream
    --  ...
    for Pos in Input'First .. Last loop
       Process (Input (Pos));
       pos := pos + 1;
    end loop;
end;