Re: [Corelinux-public] Endianess

[Jim K. <jrk...@at...>]

On Thu, 9 Dec 1999, Frank V. Castellucci wrote:

> > Is endian-ness an issue in Linux?  If a data file is created by a
> > Linux/Intel application, can it be read by the Linux/PowerPC version of
> > that application?
> >
> > Should CoreLinux provide some facility for conversion of endian-ness in
> > cross-platform data?
> >
> > Jim Koontz
> > jrk...@us...
> 
> Data Files
> --------------
> There is an issue that has to be addressed by the applications persistence
> implementation or any persistence that the library provides. From a numeric
> stand point using network byte order consistently should avoid that, or of
> course characters.
> 
> Source Files
> ------------------
> There is an issue, I know bitfields and unions may be targets for analysis,
> there may be more (I have been corrupted for too long by little-endianess)
> but avoiding bit manipulation and unions is part of the CoreLinux standards.
> 
> Binary Libraries and Apps
> ------------------------------------
> Big issue, I don't know of solutions.
> 
> 
> I'm hoping there are some who are running on both type of Linux
> implementations (big and little) that we can test/verify against early on in
> the development stages.
> 
As far as the binary libraries and apps go, I think the only solution is
to build them on each platform. 

The way that I have seen endian-ness resolved in other operating systems
is to either save in one format, and provide code that does bit flipping
if the platform reading is opposite-endian, or to save in a canonical
format, that contains a flag field indicating the source platform.  If the
platform reading is opposite-endian from the platform that saved the data,
the bit flipping takes place.  In either case, macros that test for
endian-ness and perform the bit-flipping are provided as part of the
API.

Jim Koontz
jrk...@so...