Re: [boost] [asio] some stuff about ipv4::address

From: Martin Bonner (martin.bonner_at_[hidden])
Date: 2006-01-12 11:26:46

----Original Message----
From: Chris Cleeland

> On Fri, 13 Jan 2006, Christopher Kohlhoff wrote:
> 
>> Some thoughts, both for and against:
>> 
>> - Does unsigned char always imply 0..255? 
No.

>>   Might there be a
>>   standards-conforming C++ implementation where char is not 8
>>   bits? 
Yes.  Plausible other values are 9 (for 36-bit word addressed machines),
and 32 (for DSPs where it is just too much heartache to slice a 32-bit
word).

>>   (Admittedly porting a sockets library, which inherently
>>   deals in sequences of octets, to this architecture could be
>>   rather difficult.)
Not as bad as you think.  Each octet must be able to fit into an
unsigned char.  It's just that an unsigned char can hold a value which
doesn't fit in an octet.

> 
> Good question; I know that sizeof(char) == sizeof(unsigned char) ==
> 1, but I don't know that it's guarantee anywhere that something 
> that has a sizeof==1 is exactly 8 bits.

It isn't.  It is defined that unsigned char has AT LEAST 8 bits (because
it can hold 0..255).

-- 
Martin Bonner
Martin.Bonner_at_[hidden]
Pi Technology, Milton Hall, Ely Road, Milton, Cambridge, CB4 6WZ,
ENGLAND Tel: [phone]