From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-0.3 required=5.0 tests=BAYES_00,
	REPLYTO_WITHOUT_TO_CC autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,ddd2479bb7fae4af
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news1.google.com!news4.google.com!news.glorb.com!news.zanker.org!border2.nntp.ams.giganews.com!nntp.giganews.com!lightspeed.eweka.nl!feeder.news-service.com!post.news-service.com!news1.surfino.com!not-for-mail
Message-Id: <2092747.1qBBMuiTJs@linux1.krischik.com>
From: Martin Krischik <martin@krischik.com>
Subject: Re: Bit manipulation
Newsgroups: comp.lang.ada
Reply-To: martin@krischik.com
Date: Mon, 07 Feb 2005 14:20:46 +0100
References: <211db0ae.0502070437.54add641@posting.google.com>
Organization: None
User-Agent: KNode/0.8.0
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Transfer-Encoding: 7Bit
X-Complaints-To: abuse@surfino.com
NNTP-Posting-Host: 83.169.148.166 (83.169.148.166)
NNTP-Posting-Date: Mon, 07 Feb 2005 15:00:10 +0100
X-Trace: be35e4207746af60c310315224
Xref: g2news1.google.com comp.lang.ada:8179
Date: 2005-02-07T14:20:46+01:00
List-Id: <comp.lang.ada>

Maurizio wrote:

> hi, i need two hint:
> 
> i need to acces to a 32 bit word (Interfaces.Unsigned_32).
> how i can do to take the three m.s.bit? (30,31,32)

Have you considered using a packed array?

http://en.wikibooks.org/wiki/Programming:Ada:Types:array#with_aliased_elements

Prehaps on conjunction with Unchecked_Conversion. 

> second, i need to send the 32 bit word over a Tcp connection to a C
> program, but
> socket work with usigned 8 bit word, so i need to split the 32 bit in
> 4 8bit word,
> and when i read from the socket take 4 8bit word and combine in a 32
> word.
> 
> i see that Ada.Unchecked_Conversion work (in an ada client/server test
> program)  but is correct?
> 
> --com_buffer_type is an array of  128 32bit word
> 
> subtype Datas is Ada.Streams.Stream_Element_Array(1..512); --128*4

Stream Elements are normaly not used directly. Ada.Streams only provide a
framework for the 'Read, 'Write, 'Input, and 'Output attributes. If you
know Java: It works a bit like the Serializable interface.

'Read, 'Write are low level - reading and writing raw data.
'Input, and 'Output are high level - storing array bound, object type etc.
pp. as well.

> function To_Raw is
>    new Ada.Unchecked_Conversion
>       (
>       Source => Com_Buffer_Type,  --Interfaces.Unsigned_32
>       Target => Datas);     --Stream_Element is mod 2 **
> Standard'Storage_Unit
>    function From_Raw is
>    new Ada.Unchecked_Conversion
>       (
>       Source => Datas,
>       Target => Com_Buffer_Type);

You should give com_buffer_type'Write (Stream, Datas)  a try.

Martin
-- 
mailto://krischik@users.sourceforge.net
http://www.ada.krischik.com