This post originated from an RSS feed registered with .NET Buzz by Brad Wilson. Original Post: Creating a GUID from Ruby/Windows Feed Title: The .NET Guy Feed URL: /error.aspx?aspxerrorpath=/dotnetguy/Rss.aspx Feed Description: A personal blog about technology in general, .NET in specific, and when all else fails, the real world. Latest .NET Buzz Posts Latest .NET Buzz Posts by Brad Wilson Latest Posts From The .NET Guy

I was surprised that there was no native GUID functionality in Ruby. There is a library that can be downloaded, but I like to limit my team's tool scripts to what's available by default with the Win32 one-click installer. I need to be able to generate GUIDs for a script I'm writing that auto-generates Visual Studio 2005 project files.

So I fired up MSDN help for UuidCreate, and wrote this little bit of Ruby instead:

require 'Win32API'

@uuid_create = Win32API.new('rpcrt4', 'UuidCreate', 'P', 'L')

def new_guid
  result = ' ' * 16
  @uuid_create.call(result)
  a, b, c, d, e, f, g, h = result.unpack('SSSSSSSS')
  sprintf('{%04X%04X-%04X-%04X-%04X-%04X%04X%04X}', a, b, c, d, e, f, g, h)
end

The Win32API wrapper in Ruby is very simplistic, so translating the call was also pretty easy. It expects a pointer to a UUID structure, which will be filled out. The UUID structure is 16 bytes long, so we pre-allocate a string with 16 spaces and pass it that. Then the unpack method on the string is used to convert each 16-bit number into a Ruby Fixednum. Finally, sprintf provides me with the Microsoft-style formatted GUID in string form.

Wrapping it all up in a Guid class is left as an exercise for the reader. :)