From: Ilmari Heikkinen <ilmari.heikkinen@...>
Date: 2007-09-24T21:00:59+09:00
Subject: Re: I am new to Ruby and I could use some expert advice as to how I can make this code run faster.

On 9/22/07, Nobuyoshi Nakada <nobu@ruby-lang.org> wrote:
> Hi,
>
> At Fri, 21 Sep 2007 07:05:10 +0900,
> Ruby Maniac wrote in [ruby-talk:270110]:
> > def scramble(fname)
> >     _fname = fname + ".scrambled"
>     File.new(fname, "rb") do |f|
>       File.new(_fname, "wb+") do |ff|
>         ff.write(f.read.tr("\0-\177", "\200-\377"))
>       end
>     end
> > end
>
> --
> Nobu Nakada
>

And the benchmark results for the above code on a 6.7M file:

$ time ruby -rscramble -e 'scramble_original("trace")'

real	0m11.626s
user	0m9.781s
sys	0m1.844s

$ time ruby -rscramble -e 'scramble_nobu("trace")'

real	0m0.099s
user	0m0.044s
sys	0m0.032s

116x speedup and 7 less loc

$ cat scramble.rb
def scramble_original(fname)
   f = File.new(fname, "rb")
   _fname = fname + ".scrambled"
   begin
       File.exist?(_fname) if File.delete(_fname)
   rescue
   end
   ff = File.new(_fname, "wb+")
   for l in f
       l.each_byte{|c| ff.write((c | 0x80).chr) }
   end
   f.close()
   ff.close()
end

def scramble_nobu(fname)
  File.open(fname, 'rb'){|in_f|
    File.open(fname + '.scrambled', 'wb'){|out_f|
      out_f.write(in_f.read.tr("\0-\177", "\200-\377"))
    }
  }
end