From: Erik Veenstra <erikveen@...>
Date: 2007-01-30T05:46:15+09:00
Subject: Re: "a string".xor("another string")

THANK YOU!

I added a bit of code to detect the presence of this narray. It
falls back to the Ruby implementation if narray isn't installed.

gegroet,
Erik V. - http://www.erikveen.dds.nl/

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 class String
   def xor_slow(other)
     if other.empty?
       self
     else
       a1        = self.unpack("c*")
       a2        = other.unpack("c*")

       a2 *= a1.length/a2.length + 1

       a1.zip(a2).collect{|c1,c2| c1^c2}.pack("c*")
     end
   end

   def xor_fast(other)
     if other.empty?
       self
     else
       if other.length < self.length
         div, mod        = self.length.divmod(other.length)
         other           = other * div + other[0, mod]
       end

       a1        = NArray.to_na(self, "byte")
       a2        = NArray.to_na(other, "byte")

       (a1 ^ a2).to_s
     end
   end

   begin
     require "narray"

     alias :xor :xor_fast
   rescue LoadError
     if $VERBOSE
       $stderr.puts "I strongly advise to install the library 
'narray'."
     end

     alias :xor :xor_slow
   end
 end

----------------------------------------------------------------