Unpack problems

[Aaron Patterson]

Hi! I'm having some troubles with unpack that I can't seem to figure
out. My test program looks like this:

foo = "\000\000\022\227"
puts foo.unpack("N")

On linux (ruby 1.8.3 (2005-09-21) [i386-linux]), the test program gives
the following output:

4759

Which is what I expect. However, on OS X (ruby 1.8.2 (2004-12-25)
[powerpc-darwin8.0]), I get the following output:

2534539264

I can't figure out if I'm doing something stupid, or if there is a
problem with ruby. Thanks for the help!

--Aaron

 

[Wilson Bilkovich]

This looks like an endianness issue. Check out what happens when you
reverse it:
puts foo.reverse.unpack("N")

"N" indicates Network byte order (big-endian), but it sounds like you
may want to use system byte-order, which is "L"
I don't have a Mac to test with, unfortunately. Check out page 603 in
the Pickaxe book, if you have it.

--Wilson.

 

[Aaron Patterson]

This looks like an endianness issue. Check out what happens when you
reverse it:
puts foo.reverse.unpack("N")

"N" indicates Network byte order (big-endian), but it sounds like you
may want to use system byte-order, which is "L"
I don't have a Mac to test with, unfortunately. Check out page 603 in
the Pickaxe book, if you have it.

--Wilson.

Looks like it is an endianness issue. Thank you for the help!

--Aaron

 

[Eric Hodel]

Hi! I'm having some troubles with unpack that I can't seem to figure
out. My test program looks like this:

foo = "\000\000\022\227"
puts foo.unpack("N")

On linux (ruby 1.8.3 (2005-09-21) [i386-linux]), the test program
gives
the following output:

4759

Which is what I expect. However, on OS X (ruby 1.8.2 (2004-12-25)
[powerpc-darwin8.0]), I get the following output:

2534539264

I can't figure out if I'm doing something stupid, or if there is a
problem with ruby. Thanks for the help!

Tiger's Ruby's pack/unpack have reversed endianness. You'll have to
build your own Ruby for it to work correctly.