[MacRuby] UTF-8 to MacRoman conversion

I need to convert a String from UTF-8 to MacRoman, MacRuby makes use of
a "special" iconv.rb.

When doing a Mac Roman to UTF-8 converions no prob however when doing
reversal from UTF-8 to MacRoman the String is still in UTF-8.

Here is my code :
puts "UTF-8 back to MacRoman :"
mcr = Iconv.iconv('macintosh', 'utf-8',
str_utf8).split(/#{LF}/).join(CR)
puts "#{mcr.size} chars, #{mcr.encoding}"

giving :
# => 34 chars, UTF-8

the icon.rb file (from MacRuby) being :

···

------------------------------------------------------------------------
  def iconv(str, start=0, length=-1)
    # Not sure if it's the right thing to do...
    data = CFStringCreateExternalRepresentation(nil, str, @to_enc, 0)
    if data.nil?
      raise "can't retrieve data from `#{str}'"
    end
    dest = CFStringCreateFromExternalRepresentation(nil, data, @to_enc)
    if dest.nil?
      raise "can't convert data from `#{str}'"
    end
    CFRelease(data)
    CFRelease(dest)
    dest.mutableCopy
  end
------------------------------------------------------------------------

which seems to work from "some encoding" to UTF-8 but not the reverse...

I'd like to help the designer but i'm lost in Apple's documentation
about CFStringxyz !
--
« Si l'on sait exactement ce qu'on va faire,
   à quoi bon le faire ? »
   (Pablo Picasso)