How can I programatically determine the Endian-ness of the CPU?

ton has asked for the wisdom of the Perl Monks concerning the following question:

Fellow monks,

I've written a Blowfish encyption module using Inline::C, and had pretty good results with it. I am currently using this module to encrypt data streams sent from one computer to another. However, I've run into a problem in transmitting data between machines with different architectures: the endien-ness of the CPU affects the encryption results. I got around this through a _ByteReverse function that is used if some compile-time flag is set, and I set that compile time flag ($bigEndian) within the BEGIN section of the package. So far, so good.

My problem lies in determining whether or not $bigEndian should be true. I know I can check $^O for the OS type, and this lets me cheat a bit: Windows and Linux systems are usually Little-Endian, while HPUX is usually Big-Endian. But sparc machines can be either, and Linux _could_ be installed on a machine not using an Intel or AMD CPU.

Is there some perl function that can give me the endian-ness of the CPU? Or some subroutine I can write to have the package determine this on its own? Or am I stuck with my OS-type hack?

Any help is appreciated,

-Ton
-----
Be bloody, bold, and resolute; laugh to scorn
The power of man...

Comment on How can I programatically determine the Endian-ness of the CPU?

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Re: How can I programatically determine the Endian-ness of the CPU?
by grep (Monsignor) on Jan 26, 2002 at 05:07 UTC

Config

$Config{byteorder}

byteorder

From byteorder.U:


This variable holds the byte order. In the following, larger digits
indicate more significance. The variable byteorder is either 4321 on a
big-endian machine, or 1234 on a little-endian, or 87654321 on a Cray 
+...
or 3412 with weird order !
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determine endian

search is your friend

grep

grep> cd pub grep> more beer

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Re: How can I programatically determine the Endian-ness of the CPU?
by wog (Curate) on Jan 26, 2002 at 05:14 UTC

Config

grep

perlport

If you need to distinguish between endian architectures you could use either of the variables set like so:
  $is_big_endian   = unpack("h*", pack("s", 1)) =~ /01/;
  $is_little_endian = unpack("h*", pack("s", 1)) =~ /^1/;
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