From: Robert Klemme <shortcutter@...>
Date: 2007-03-09T07:10:06+09:00
Subject: Re: generate UUID

On 08.03.2007 22:44, Aaron Smith wrote:
> Anyone have a fast way of generating a verson 4 UUID?
> 
> I have found some libraries to do this, but it seems like it could be
> done in about 8 lines of code. Any faster approches?
> 
> what about this?
> 
> def rand_hex(l)
>     validChars = ("A".."F").to_a + ("0".."9").to_a
>     length = validChars.size
>     hexCode = ""
>     1.upto(l) do |i|
>       hexCode << validChars[rand(length-1)]
>     end
>     hexCode
> end
> 
> r =
> "#{rand_hex(8)}-#{rand_hex(4)}-#{rand_hex(4)}-#{rand_hex(4)}-#{rand_hex(12)}"
> puts r

Make validChars and length constants declared outside the method.  And 
also, use rand(length) otherwise you never get a "9".  You could also 
use ?A..?F and ?0..?9 - no idea whether that makes a performance diff.

But I guess this one is even faster:

def rand_hex_2(l)
   rand(1 << (l*4)).to_a(16)
end

Kind regards

	robert