Re: gcc and little/big endian

FROM : Greg Parker
DATE : Thu Jan 30 12:39:01 2003

> According to what I'v read, the PowerPC is supposed to
> be able to handle both little and big endian data
> formats.
>
> Has anyone managed to compile in little endian on the
> mac (I'd like to be able to natively treat
> little-endian network packets without going through
> the hasle of converting every second field...)?


The PowerPC can do two things with little-endian data:

* The CPU itself can do everything in little-endian mode. This
  doesn't help you because it needs OS support that Mac OS X
  doesn't have. (I don't know whether the OS needs to be little-
  endian or whether the OS can switch the CPU's endianness on
  the fly for different processes. In any case, Mac OS X doesn't
  do either.)

* When in big-endian mode, there are special load and store
  instructions that byte-swap the data as it comes in. If you
  really need the speed, you could write parts of your packet
  handler in assembly and use those instructions directly.


--
Greg Parker    <email_removed>