Date: Fri, 1 Feb 2002 04:14:12 +0100 From: Cliff Sarginson <cliff@raggedclown.net> To: freebsd-questions@freebsd.org Subject: Re: unsigned char portability Message-ID: <20020201031412.GA1950@raggedclown.net> In-Reply-To: <a3cdi5$19e5$1@kemoauc.mips.inka.de> References: <F74DyNdauuNi4kysRWz00010abe@hotmail.com> <a3cdi5$19e5$1@kemoauc.mips.inka.de>
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On Thu, Jan 31, 2002 at 09:39:17PM +0000, Christian Weisgerber wrote: > June Carey <carey_june@hotmail.com> wrote: > > > I have a question I was hoping someone could answer. > > Does the "unsigned char" C type have any machine architecture portability > > problems ? > > For one thing, you don't know its size. I'm told there are C > implementations on DSPs and such that have 32-bit chars, simply > because those processors don't support other datasizes or byte > addressing. Now whether you care about portability to such platforms > is a different matter. > That doesn't matter, as long as you don't take liberties on it's assumed size, i.e. if it matters use "sizeof", don't fiddle with it inside an aggregate like a struct except as a member of that struct, you can always treat is an unsigned 8 bit quantity even on a Risc machine, where it's "real" size will probably not be 8 bits (it is irrelevant whether the OS is FreeBSD or not). > As far as FreeBSD is concerned, i.e. any platform FreeBSD is likely > to be ported to, you can assume an unsigned char to refer to an > unsigned 8-bit integer. > > > I rather suspect the answer is NO, since I seem to recall that "The Design > > and Implementation of the 4.4BSD Operating System" book mentions that > > bytes/octets are network portable in their native bit-ordering. > > Just like memory, networks tend to treat the octet as the atomic > unit of transmission. Of course you need to worry about bit-ordering > any time you serialize an octet, but that is usually handled in > hardware. > > -- > Christian "naddy" Weisgerber naddy@mips.inka.de > > > To Unsubscribe: send mail to majordomo@FreeBSD.org > with "unsubscribe freebsd-questions" in the body of the message -- Regards Cliff To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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