String.unpack endianess issue?


#1

In irb 0.9 (ruby 1.8.2) in cygwin/WindowsXP:

a = [0, 0, 0, 6]
=> [0, 0, 0, 6]
x = a.pack(“C*”)
=> “\000\000\000\006”
x.unpack(“I”)
=> [100663296]
x.unpack(“V”)
=> [100663296]

I would have though that at least one of “I” or “V” in the unpack call
would have given me the correct answer, 6. I’m reading this data out
of a binary file, stored in big-endian, but neither handles this.

I managed to get the right answer by doing:

x.unpack(“C*”).reverse.pack(“C*”).unpack(“I”)

But that seems rather silly. So I guess I’m asking:

  1. Is unpack broken, or is there a big-endian option I missed?
  2. Is there a more generic module/library for reading binary files?
  3. Is there an existing modules/lib for reading MIDI files?

thanks…


#2

Matthew M. wrote:

  1. Is unpack broken, or is there a big-endian option I missed?
  2. Is there a more generic module/library for reading binary files?
  3. Is there an existing modules/lib for reading MIDI files?

thanks…

irb(main):001:0> a = [0, 0, 0, 6]
=> [0, 0, 0, 6]
irb(main):002:0> x = a.pack(“C*”)
=> “\000\000\000\006”
irb(main):003:0> x.unpack “N”
=> [6]

For convenience, I wrote a set of object-oriented wrappers around
pack/unpack. See bit-struct on raa.


#3

irb(main):001:0> a = [0, 0, 0, 6]
=> [0, 0, 0, 6]
irb(main):002:0> x = a.pack(“C*”)
=> “\000\000\000\006”
irb(main):003:0> x.unpack “N”
=> [6]

For convenience, I wrote a set of object-oriented wrappers around
pack/unpack. See bit-struct on raa.

Ah, thanks. I noticed the “V” as I searched for “endian” in the docs,
but I missed the “N”. Should have searched on “byte order”. Thanks…