Re: Header folding

* David A Golden ([email protected]) [040818 22:26]:
> Wow.  Given the documentation, that's definitely unexpected behavior.  It 
> looks like the default wrapping never gets set properly. Here's some code 
> that's a workaround:
> 
> __BEGIN__
> #!/usr/bin/perl
> use Mail::Message;
> 
> my $msg = Mail::Message->read(\*STDIN);
> $_->setWrapLength(78) for $msg->head->orderedFields;
> $msg->print;
> __END__
> 
> Mark -- this looks like a bug, but I'm stumped trying to track it down 
> through the class hierarchy and overloadings.

I do not know where this is documented that way, but it will surely
be a left-over from old behavior.  Old behavior was copied from
Mail::Internet, but has been modified to comply with the RFCs.

According to RFC2822:

   The more conservative 78 character recommendation is to accommodate
   the many implementations of user interfaces that display these
   messages which may truncate, or disastrously wrap, the display of
   more than 78 characters per line, in spite of the fact that such
   implementations are non-conformant to the intent of this
   specification (and that of [RFC2821] if they actually cause
   information to be lost). Again, even though this limitation is put on
   messages, it is encumbant upon implementations which display messages
   to handle an arbitrarily large number of characters in a line
   (certainly at least up to the 998 character limit) for the sake of
   robustness.

As you see, folding is a recommendation, not a MUST.
The disadvantage on automatic folding fields are plenty:
 - applications, like SpamAssassin, may wish the exact folding regardless
   how long the lines are.
 - messages will change in size (added/removed \n)
 - some messages have a reason to fold in certain short lines, for instance
   if they want to show a postal address. You don't want to break that.
 - after folding, the message in memory is different from the message
   in the folder file.
 - refolding will require quite a lot of processing power.

Especially the last point made me decide that folding should be kept
in-tact, unless explicitly (knowingly) re-folded.  But when you wish
it to happen it should be simple, and that was a missing library feature.
So, in the next release Mail::Message::Head::Complete will contain:

 =method wrap INTEGER
 Re-fold all fields from the header to contain at most INTEGER number of
 characters per line.
                                                                                
 =example re-folding a header
  $msg->head->wrap(78);
 =cut
                                                                                
 sub wrap($)
 {   my ($self, $length) = @_;
     $_->setWrapLength($length) foreach $self->orderedFields;
 }

-- 
Thanks,
               MarkOv

------------------------------------------------------------------------
drs Mark A.C.J. Overmeer                                MARKOV Solutions
       [email protected]                          [email protected]
http://Mark.Overmeer.net                   http://solutions.overmeer.net