Re: for S'Image use Func??

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On Tue, 11 May 2010 20:56:11 +0000 (UTC), Warren wrote:

> Dmitry A. Kazakov expounded in news:1qfu2ba65pd63$.asc7m201hi6u$.dlg@
> 40tude.net:
> 
>> On Tue, 11 May 2010 17:17:38 +0000 (UTC), Warren wrote:
>> 
>>> =?utf-8?Q?Yannick_Duch=C3=AAne_=28Hibou57?= =?utf-8?Q?=29?= expounded 
> in
>>> news:op.vcig7go1ule2fv@garhos: 
>>> 
>>>> Le Mon, 10 May 2010 22:56:11 +0200, Maciej Sobczak  
>>>> <see.my.homepage@gmail.com> a écrit:
>>>>> Coming back to I/O - what I miss in Ada is the equivalent of fread 
> in
>>>>> C - that is, an operation that reads *up to* the given number of
>>>>> bytes. Or maybe there is something that I didn't notice?
>>> 
>>>> It's there : look at [ARM 2005 13.13.1] which defines the package  
>>>> Ada.Streams, which in turn contains the following :
>>>> 
>>>>     type Root_Stream_Type is abstract tagged limited private;
>>>>     ...
>>>>     type Stream_Element is mod implementation-defined;
>>>>     ...
>>> ...
>>>> Well, to be honest, this is not exactly the same as with C, as  
>>>> Ada.Streams.Stream_Element is implementation defined (which is good,  
>>>> because this is indeed platform dependent), so you will need ..
>>> 
>>> All this is well and good for applications that can work in 
>>> "implementation defined" units of type Stream_Element. A pragma
>>> won't fix the problem should it be different than a byte. Granted,
>>> it will never likely come up on the platforms I have in mind.
>> 
>> If you to read a character stream, just do so:
>> 
>>    Item := Character'Read (S);
>>    Character'Write (S, Item);
>> 
>> For octet streams use Unsigned_8.
> 
> But this has to include seeking in the stream as well.

Repeat reading n times.

> Can you guarantee seeking to an arbitrary "byte boundary"?

On a machine with 13 bis per character? Can you define "byte boundary"? The
point is that if Stream_Element is not 8 bits, and the environment supports
streams of octets, then I see no reason why Ada vendor would implement
Unsigned_8r'Read incompatible with that.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de