Background: I'm working on reformating .mbox files to convert email archives to HTML and to PDA compatible text. I'm running into problems with the MIME types "multipart/mixed" and "multipart/related". These are umbrella types that can hold an assortment of simple types, like "text/plain", and "image/jpg". However they can also hold other multipart types, which can happen when someone backquotes the entirety of a previous multipart message.
There is also the "multipart/alternative" type, but these are always collections of simple types where the user agent chooses one and ignores the rest-- they are never re-entrant.
My code is something like this (following is simplified to keep it short and on point):
sub handleBody {
my ($type, $body) = @_;
my $superbody = '';
if ( $type =~ m{multipart}i ) {
my ( @parts ) = splitOnBoundary($type, $body);
if ( $type =~ m{alternative}i ) {
# code to find the $best of the alternatives in @parts
($type, $body) = handlePart($parts[$best])
processSimpleType($type, $body);
return $body;
}
else { # PLACE WHERE MY HEAD HURTS
foreach (@parts) {
$superbody .= handleBody(handlePart($_) );
}
return $superbody;
}
}
else { # handle a simple type
processSimpleType($type, $body)
return $body
}
}sub handlePart {
my $part = shift;
my ($head, $body) = split /^$/m, $part, 2;
# treat exceptions as a type of its own:
my $type = '[NONE STATED]';
if ( $head =~ m{^Content-Type: (.*)$}mi ) {
$type = $1;
}
return ($type, $body);
}Hmm, as I wrote this, I discovered the apparent need for $superbody, and I think I may have solved my logic problem. So the first of my two questions:
1) Does the above code look right?
A major difficulty is that I'm dealing with archives where some of the messages aren't fully compliant with the MIME standard and I can't tell whether the bugs I've got are in the logic or because I need to tweak the regexes to handle the special cases. Which brings me to the other, more important, question:
2) Is there a better tool for designing re-entrant code other than pseudocode? How do people who do a lot of this kind of thing work out the design?
-- Will
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