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=0.4 required=5.0 tests=BAYES_00,FORGED_MUA_MOZILLA
	autolearn=no autolearn_force=no version=3.4.4
X-Google-Thread: 103376,d778a4f52acd9d43
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Received: by 10.68.189.194 with SMTP id gk2mr16629941pbc.3.1324888390306;
        Mon, 26 Dec 2011 00:33:10 -0800 (PST)
Path: 
 lh20ni65679pbb.0!nntp.google.com!news2.google.com!volia.net!news2.volia.net!feed-A.news.volia.net!fu-berlin.de!uni-berlin.de!individual.net!not-for-mail
From: Niklas Holsti <niklas.holsti@tidorum.invalid>
Newsgroups: comp.lang.ada
Subject: Re: Representation clauses for base-64 encoding
Date: Mon, 26 Dec 2011 10:33:08 +0200
Organization: Tidorum Ltd
Message-ID: <9lqpq5Ft05U1@mid.individual.net>
References: <slrnjf5uol.1lme.lithiumcat@sigil.instinctive.eu>
 <9lgi3jFhaU1@mid.individual.net> <jd0lje$3gv$1@munin.nbi.dk>
Mime-Version: 1.0
X-Trace: individual.net HjecI/MgOH926zD/6TB4nAqwc1yLwERdfrp8YmU0sOiOVgLRCc
Cancel-Lock: sha1:pU4yF/lt9qtahuvmMgt2PWOyhAs=
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.6;
 rv:8.0) Gecko/20111105 Thunderbird/8.0
In-Reply-To: <jd0lje$3gv$1@munin.nbi.dk>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Date: 2011-12-26T10:33:08+02:00
List-Id: <comp.lang.ada>

On 11-12-23 03:30 , Randy Brukardt wrote:
> "Niklas Holsti"<niklas.holsti@tidorum.invalid>  wrote in message
> news:9lgi3jFhaU1@mid.individual.net...
>> On 11-12-22 11:41 , Natasha Kerensikova wrote:
> ...
>>>      type Octet_Block is array (1 .. 3) of Octet;
>>>      pragma Pack (Octet_Block);
>>
>> I would add the following, to check that packing is effective:
>>
>>        for Octet_Block'Size use 24;
>
> I think it would probably be better to forget Pack and actually say what you
> mean here:
>
>      type Octet_Block is array (1 .. 3) of Octet;
>      for Octet_Block'Component_Size use 8;
>
> "Pack" should be reserved for cases where you don't care about the exact
> layout, you just want to save space. Here you do care about the exact
> layout, so use a Component_Size.

Fine adjustment: when Component_Size is not a factor or multiple of the 
word size, RM 13.3(73) says that the array may also have to be packed in 
order to eliminate gaps between components.

Of course, a Component_Size of 8 bits is usually a factor of the word 
size. But perhaps not always.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .