From: John Joyce <dangerwillrobinsondanger@...>
Date: 2007-09-21T11:16:39+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 Sep 20, 2007, at 8:50 PM, Brian Adkins wrote:

> On Sep 20, 6:02 pm, Ruby Maniac <raych...@hotmail.com> wrote:
>> I am new to Ruby and I could use some expert advice as to how I can
>> make this code run faster.
>
> Write a C extension. Seriously, Ruby is pretty darn slow at iterating
> over each byte of a file. The I/O is reasonable, but the byte
> iteration is terrible. You might get a small speedup by using
> File#read instead of File#each_byte:
>
>   while (buffer = f.read(BUF_SIZE))
>     buffer.each_byte {|b| ... }
>   end
>
> I got about a 5% speedup using an 8K buffer.
>
> You also may want to consider the idiom:
>
> File.open(filename) do |f|
>    ...
> end
>
> This will automatically close the file at the end of the block.
>
>> def scramble(fname)
>>     f = File.new(fname, "rb")
>>     _fname = fname + ".scrambled"
>>     begin
>>         File.exist?(_fname) if File.delete(_fname)
>
> You may want to double check the previous line.
>
>>     rescue
>>     end
>>     ff = File.new(_fname, "wb+")
>>     for l in f
>>         l.each_byte{|c| ff.write((c | 0x80).chr) }
>
> So you don't need to get the original file data back, right? If you
> do, you may want to use xor instead, and if you don't, then why not
> just write zeros?
>
>>     end
>>     f.close()
>>     ff.close()
>> end
>
>
>
Benchmark it so you can find the bottlenecks.