NAME

IMAP::BodyStructure - IMAP4-compatible BODYSTRUCTURE and ENVELOPE parser

SYNOPSIS

use IMAP::BodyStructure;

# $imap is a low-level IMAP-client with an ability to fetch items
# by message uids

my $bs = new IMAP::BodyStructure
    $imap->imap_fetch($msg_uid,
            'BODYSTRUCTURE', 1)->[0]->{BODYSTRUCTURE};

print "[UID:$msg_uid] message is in Russian. Sure.\n"
    if $bs->charset =~ /(?:koi8-r|windows-1251)/i;

my $part = $bs->part_at('1.3');
$part->type =~ m#^image/#
    and print "The 3rd part is an image named \""
        . $part->filename . "\"\n";

DESCRIPTION

An IMAP4-compatible IMAP server MUST include a full MIME-parser which parses the messages inside IMAP mailboxes and is accessible via BODYSTRUCTURE fetch item. This module provides a Perl interface to parse the output of IMAP4 MIME-parser. Hope no one will have problems with parsing this doc.

It is a rather straightforward m/\G.../gc-style parser and is therefore much, much faster then the venerable Mail::IMAPClient::BodyStructure which is based on a Parse::RecDescent grammar. I believe it is also more correct when parsing nested multipart message/rfc822 parts. See testsuite if interested.

I'd also like to emphasize that this module does not contain IMAP4 client! You will need to employ one from CPAN, there are many. A section with examples of getting to a BODYSTRUCTURE fetch item with various Perl IMAP clients available on CPAN would greatly enhance this document.

INTERFACE

METHODS

• new($)

  The constructor does most of the work here. It initializes the hierarchial data structure representing all the message parts and their properties. It takes one argument which should be a string returned by IMAP server in reply to a FETCH command with BODYSTRUCTURE item.

  All the parts on all the levels are represented by IMAP::BodyStructure objects and that enables the uniform access to them. It is a direct implementation of the Composite Design Pattern.

• type()

  Returns the MIME type of the part. Expect something like text/plain or application/octet-stream.

• encoding()

  Returns the MIME encoding of the part. This is usually one of '7bit', '8bit', 'base64' or 'quoted-printable'.

• size()

  Returns the size of the part in octets. It is NOT the size of the data in the part, which may be encoded as quoted-printable leaving us without an obvious method of calculating the exact size of original data.

• disp()

  Returns the content-disposition of the part. One of 'inline' or 'attachment', usually. Defaults to inline, but you should remember that if there IS a disposition but you cannot recognize it than act as if it's 'attachment'. And use case-insensitive comparisons.

• charset()

  Returns the charset of the part OR the charset of the first nested part. This looks like a good heuristic really. Charset is something resembling 'UTF-8', 'US-ASCII', 'ISO-8859-13' or 'KOI8-R'. The standard does not say it should be uppercase, by the way.

  Can be undefined.

• filename()

  Returns the filename specified as a part of Content-Disposition header.

  Can be undefined.

• description()

  Returns the description of the part.

• parts(;$)

  This sub acts differently depending on whether you pass it an argument or not.

  Without any arguments it returns a list of parts in list context and the number in scalar context.

  Specifying a scalar argument allows you to get an individual part with that index.

  Remember, all the parts I talk here about are not actual message data, files etc. but IMAP::BodyStructure objects containing information about the message parts which was extracted from parsing BODYSTRUCTURE IMAP response!

• part_at($)

  This method returns a message part by its path. A path to a part in the hierarchy is a dot-separated string of part indices. See "SYNOPSIS" for an example. A nested message/rfc822 does not add a hierarchy level UNLESS it is a single part of another message/rfc822 part (with no multipart/* levels in between). Instead, it has an additional .TEXT part which refers to the internal IMAP::BodyStructure object. Look, here is an outline of an example message structure with part paths alongside each part.

    multipart/mixed                   1
        text/plain                    1.1
        application/msword            1.2
        message/rfc822                1.3
            multipart/alternative     1.3.TEXT
                text/plain            1.3.1
                multipart/related     1.3.2
                    text/html         1.3.2.1
                    image/png         1.3.2.2
                    image/png         1.3.2.3
  

  This is a text email with two attachments, one being an MS Word document, and the other is itself a message (probably a forward) which is composed in a graphical MUA and contains two alternative representations, one plain text fallback and one HTML with images (bundled as a multipart/related).

  Another one with several levels of message/rfc822. This one is hard to compose in a modern MUA, however.

    multipart/mixed                   1
        text/plain                    1.1
        message/rfc822                1.2
            message/rfc822            1.2.TEXT
                text/plain            1.2.1
  

• part_path()

  Returns the part path to the current part.

DATA MEMBERS

These are additional pieces of information returned by IMAP server and parsed. They are rarely used, though (and rarely defined too, btw), so I chose not to provide access methods for them.

• params

  This is a hashref of MIME parameters. The only interesting param is charset and there's a shortcut method for it.

• lang

  Content language.

• loc

  Content location.

• cid

  Content ID.

• md5

  Content MD5. No one seems to bother with calculating and it is usually undefined.

cid and md5 members exist only in singlepart parts.

• get_enveleope($)

  Parses a string into IMAP::BodyStructure::Envelope object. See below.

IMAP::BodyStructure::Envelope CLASS

Every message on an IMAP server has an envelope. You can get it using ENVELOPE fetch item or, and this is relevant, from BODYSTRUCTURE response in case there are some nested messages (parts with type of message/rfc822). So, if we have a part with such a type then the corresponding IMAP::BodyStructure object always has envelope data member which is, in turn, an object of IMAP::BodyStructure::Envelope.

You can of course use this satellite class on its own, this is very useful when generating meaningful message lists in IMAP folders.

METHODS

• new($)

  The constructor create Envelope object from string which should be an IMAP server respone to a fetch with ENVELOPE item or a substring of BODYSTRUCTURE response for a message with message/rfc822 parts inside.

DATA MEMBERS

• date

  Date of the message as specified in the envelope. Not the IMAP INTERNALDATE, be careful!

• subject

  Subject of the message, may be RFC2047 encoded, of course.

• message_id

• in_reply_to

  Message-IDs of the current message and the message in reply to which this one was composed.

• to, from, cc, bcc, sender, reply_to

  These are the so called address-lists or just arrays of addresses. Remember, a message may be addressed to lots of people.

  Each address is a hash of four elements:

  • name

    The informal part, "A.U.Thor" from "A.U.Thor, <[email protected]>"

  • sroute

    Source-routing information, not used. (By the way, IMAP4r1 spec was born after the last email address with sroute passed away.)

  • account

    The part before @.

  • host

    The part after @.

  • full

    The full address for display purposes.

EXAMPLES

The usual way to determine if an email has some files attached (in order to display a cute little scrap in the message list, e.g.) is to check whether the message is multipart or not. This method tends to give many false positives on multipart/alternative messages with a HTML and plaintext parts and no files. The following sub tries to be a little smarter.

sub _has_files {
    my $bs = shift;

    return 1 if $bs->{type} !~ m#^(?:text|multipart)/#;

    if ($bs->{type} =~ m#^multipart/#) {
        foreach my $part (@{$bs->{parts}}) {
            return 1 if _has_files($part);
        }
    }

    return 0;
}

This snippet selects a rendering routine for a message part.

foreach (
    [ qr{text/plain}            => \&_render_textplain  ],
    [ qr{text/html}             => \&_render_texthtml   ],
    [ qr{multipart/alternative} => \&_render_alt        ],
    [ qr{multipart/mixed}       => \&_render_mixed      ],
    [ qr{multipart/related}     => \&_render_related    ],
    [ qr{image/}                => \&_render_image      ],
    [ qr{message/rfc822}        => \&_render_rfc822     ],
    [ qr{multipart/parallel}    => \&_render_mixed      ],
    [ qr{multipart/report}      => \&_render_mixed      ],
    [ qr{multipart/}            => \&_render_mixed      ],
    [ qr{text/}                 => \&_render_textplain  ],
    [ qr{message/delivery-status}=> \&_render_textplain ],
) {
    $bs->type =~ $_->[0]
        and $renderer = $_->[1]
        and last;
}

BUGS

Shouldn't be any, as this is a simple parser of a standard structure.

AUTHOR

Alex Kapranoff <[email protected]>

ACKNOWLEDGMENTS

Jonas Liljegren contributed support for multivalued "lang" items.

COPYRIGHT AND LICENSE

This software is copyright (C) 2015 by Alex Kapranoff <[email protected]>.

This is free software; you can redistribute it and/or modify it under the terms GNU General Public License version 3.

SEE ALSO

Mail::IMAPClient, Net::IMAP::Simple, RFC3501, RFC2045, RFC2046.