From: Brian Candler <B.Candler@...>
Date: 2003-04-06T17:39:13+09:00
Subject: Re: parsing/decoding mail/news headers

On Sun, Apr 06, 2003 at 10:45:02AM +0900, Martin Pirker wrote:
> [some hours later]
> 
> my quick&dirty hack:
> 
> def decode(str)
>   str = str.gsub(/=\?iso-8859-(1|15)\?q\?(.*?)\?=/i){|x|
>           x.gsub(/=\?iso-8859-(1|15)\?q\?/i,"") [0..-3].unpack("M*").to_s.tr("_"," ")}
>   str = str.gsub(/=\?iso-8859-(1|15)\?b\?(.*?)\?=/i){|x|
>           x.gsub(/=\?iso-8859-(1|15)\?b\?/i,"") [0..-3].unpack("m*").to_s.tr("_"," ")}
>   str
> end
> 
> not a perfect conversion, but at least -1 and -15, Q and B cases
> are readable and that's good enough for me
> 
> the Ruby experts may suggest now a way to roll both into one ;-)

I still don't class myself as a Ruby expert :-) But I do notice the
duplicated gsubs which are easy to remove because $2 contains whatever
string matched the second parenthesised expression:

  str = str.gsub(/=\?iso-8859-(1|15)\?q\?(.*?)\?=/i){|x|
    $2.unpack("M*").to_s.tr("_"," ")
  }

Then you can combine the two if you like by selecting the appropriate value
for unpack:

  RFC2047_UNPACK = { 'q' => 'M*', 'b' => 'm*' }
  def decode(str)
    str.gsub(/=\?iso-8859-(1|15)\?(b|q)\?(.*?)\?=/i){|x|
      $3.unpack(RFC2047_UNPACK[$2.downcase]).to_s.tr("_"," ")
    }
  end

Regards,

Brian.