From: "Peña, Botp" <botp@...>
Date: 2008-07-02T19:35:38+09:00
Subject: Re: Problem with unpack

From: Rafael [mailto:mayoral.rafael@gmail.com] 
# strhex = str.unpack("H*")

you assume the return value is a string :)

botp@botp-desktop:~$ qri string.unpack
---------------------------------------------------------- String#unpack
     str.unpack(format)   => anArray
------------------------------------------------------------------------
     Decodes str (which may contain binary data) according to the
     format string, returning an array of each value extracted. The
     format string consists of a sequence ....

verify it by using #class method
eg,

  p strhex.class

 
# and look for the desired group within this "transformed" string
# if (strhex.include?("02001000")) == true then

c/c++-ism ;) lose the "== true" portion,

  if strhex[0].include?("02001000")

or much better,

  strhex = str.unpack("H*")[0]  #<---note the index for 1st elem
  if strhex.include?("02001000")
     puts "The tag was found"
  ....


or something like that


# As I said, this doesn't work (it reports the tag was not found!) and I
# wonder whether it has something to do with the fact that
# 
# strhex.length # -> 1

you got a hint there.  should have check it further ;)

 
# By the way, if after unpacking I do
# puts strhex

try,

  p strhex


# then I get the correct string, that is exactly the same as hexdump
# shows me on the left-hand side.
# So strhex seems to contain what I need, but still there is some kind
# of problem.

that implies that you are very close to your objective ...

hth.

kind regards -botp