Date: Thu, 3 Mar 2011 21:50:10 +0100 From: Erik Trulsson <ertr1013@student.uu.se> To: Frank Solensky <frank@solensky.org> Cc: freebsd-questions@freebsd.org Subject: Re: Bit order == byte order?? Message-ID: <20110303205010.GA47653@owl.midgard.homeip.net> In-Reply-To: <910E776A-D865-4F78-8BE5-E974326636D0@solensky.org> References: <910E776A-D865-4F78-8BE5-E974326636D0@solensky.org>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, Mar 03, 2011 at 11:26:12AM -0500, Frank Solensky wrote: > In sys/netinet/ip.h, the first octet of the ip header structure tests > the byte ordering to determine the ordering of the header length > (ip_hl) and version (ip_v) fields. > > My question: that always works? While my reading of the language > specification document leaves both the ordering of the bits within a > byte and the bytes within a longer field as implementation choices, > the two are independent of each other. > > I haven't run into a CPU where this assumption was proven incorrect. > It just surprised me to see that recently Unless you have a CPU where memory is addressed bit-by-bit rather than byte-by-byte the ordering of bits within a byte is not only completely irrelevant, it is also pretty much impossible to determine programatically. -- <Insert your favourite quote here.> Erik Trulsson ertr1013@student.uu.se
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20110303205010.GA47653>