MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)NAMEMIME::Parser - split MIME mail into decoded components
WARNING: This code is in an evaluation phase until 1
August 1996. Depending on any comments/complaints
received before this cutoff date, the interface may change
in a non-backwards-compatible manner.
DESCRIPTION
Where it all begins. This is how you'll parse MIME
streams to obtain MIME::Entity objects.
SYNOPSIS
use MIME::Parser;
# Create a new parser object:
my $parser = new MIME::Parser;
# Optional: set up parameters that will affect how it extracts
# documents from the input stream:
$parser->output_dir("$ENV{HOME}/mimemail");
# Parse an input stream:
$entity = $parser->read(\*STDIN) or die "couldn't parse MIME stream";
# Congratulations: you now have a (possibly multipart) MIME entity!
$entity->dump_skeleton; # for debugging
WARNINGS
The organization of the output_path() code changed in
version 1.11 of this module. If you are upgrading from a
previous version, and you use inheritance to override the
output_path() method, please take a moment to familiarize
yourself with the new code. Everything should still work,
but ya never know...
New, untested binmode() calls were added in module version
1.11... if binmode() is not a NOOP on your system, please
pay careful attention to your output, and report any
anomalies. It is possible that "make test" will fail on
such systems, since some of the tests involve checking the
sizes of the output files. That doesn't necessarily
indicate a problem.
PUBLIC INTERFACE
new Create a new parser object. You can then set up
various parameters before doing the actual parsing:
my $parser = new MIME::Parser;
$parser->output_dir("/tmp");
$parser->output_prefix("msg1");
my $entity = $parser->read(\*STDIN);
28/Aug/1996 perl 5.005, patch 03 1
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)
output_dir [DIRECTORY]
Get/set the output directory for the parsing
operation. This is the directory where the extracted
and decoded body parts will go. The default is ".".
If DIRECTORY is not given, the current output
directory is returned. If DIRECTORY is given, the
output directory is set to the new value, and the
previous value is returned.
output_path HEAD
Utility method. Given a MIME head for a file to be
extracted, come up with a good output pathname for the
extracted file.
o You'll probably never need to invoke this method
directly. As of version 1.11, this method is
provided so that your output_path_hook() function
(or your MIME::Parser subclass) can have clean
access to the original algorithm. This method no
longer attempts to run the user hook function.
Normally, the "directory" portion of the returned
path will be the output_dir(), and the "filename"
portion will be the recommended filename
extracted from the MIME header (or some simple
temporary file name, starting with the
output_prefix(), if the header does not specify a
filename).
If there is a recommended filename, but it is
judged to be evil (if it is empty, or if it
contains "/"s or ".."s or non-ASCII characters),
then a warning is issued and the temporary file
name is used in its place. This may be overly
restrictive, so...
NOTE: If you don't like the behavior of this
function, you can override it with your own
routine. See output_path_hook() for details.
If you want to be OOish about it, you could
instead define your own subclass of MIME::Parser
and override it there:
28/Aug/1996 perl 5.005, patch 03 2
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)
package MIME::MyParser;
require 5.002; # for SUPER
use strict;
use package MIME::Parser;
@MIME::MyParser::ISA = ('MIME::Parser');
sub output_path {
my ($self, $head) = @_;
# Your code here; FOR EXAMPLE...
if (i_have_a_preference) {
return my_custom_path;
}
else { # return the default path:
return $self->SUPER::output_path($head);
}
}
1;
Thanks to Laurent Amon for pointing out problems
with the original implementation, and for making
some good suggestions. Thanks also to Achim
Bohnet for pointing out that there should be a
hookless, OO way of overriding the output_path.
output_path_hook SUBREF
Install a different function to generate the output
filename for extracted message data. Declare it like
this:
sub my_output_path_hook {
my $parser = shift; # this MIME::Parser
my $head = shift; # the MIME::Head for the current message
# Your code here: it must return a path that can be
# open()ed for writing. Remember that you can ask the
# $parser about the output_dir, and you can ask the
# $head about the recommended_filename!
}
And install it immediately before parsing the input
stream, like this:
# Create a new parser object, and install my own output_path hook:
my $parser = new MIME::Parser;
$parser->output_path_hook(\&my_output_path_hook);
# NOW we can parse an input stream:
$entity = $parser->read(\*STDIN);
This method is intended for people who are squeamish
about creating subclasses. See the output_path()28/Aug/1996 perl 5.005, patch 03 3
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)
documentation for a cleaner, OOish way to do this.
output_prefix [PREFIX]
Get/set the output prefix for the parsing operation.
This is a short string that all filenames for
extracted and decoded body parts will begin with. The
default is "msg".
If PREFIX is not given, the current output prefix is
returned. If PREFIX is given, the output directory is
set to the new value, and the previous value is
returned.
parse_two HEADFILE BODYFILE
Convenience front-end onto read(), intended for
programs running under mail-handlers like deliver,
which splits the incoming mail message into a header
file and a body file.
Simply give this method the paths to the respective
files. These must be pathnames: Perl "open-able"
expressions won't work, since the pathnames are shell-
quoted for safety.
WARNING: it is assumed that, once the files are cat'ed
together, there will be a blank line separating the
head part and the body part.
read FILEHANDLE
Takes a MIME-stream and splits it into its component
entities, each of which is decoded and placed in a
separate file in the splitter's output_dir().
The stream should be given as a glob ref to a readable
FILEHANDLE; e.g., \*STDIN.
Returns a MIME::Entity, which may be a single entity,
or an arbitrarily-nested multipart entity. Returns
undef on failure.
UNDER THE HOOD
RFC-1521 gives us the following BNF grammar for the body
of a multipart MIME message:
multipart-body := preamble 1*encapsulation close-delimiter epilogue
encapsulation := delimiter body-part CRLF
delimiter := "--" boundary CRLF
; taken from Content-Type field.
; There must be no space between "--"
; and boundary.
28/Aug/1996 perl 5.005, patch 03 4
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)
close-delimiter := "--" boundary "--" CRLF
; Again, no space by "--"
preamble := discard-text
; to be ignored upon receipt.
epilogue := discard-text
; to be ignored upon receipt.
discard-text := *(*text CRLF)
body-part := <"message" as defined in RFC 822, with all
header fields optional, and with the specified
delimiter not occurring anywhere in the message
body, either on a line by itself or as a substring
anywhere. Note that the semantics of a part
differ from the semantics of a message, as
described in the text.>
From this we glean the following algorithm for parsing a
MIME stream:
28/Aug/1996 perl 5.005, patch 03 5
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)
PROCEDURE parse
INPUT
A FILEHANDLE for the stream.
An optional end-of-stream OUTER_BOUND (for a nested multipart message).
RETURNS
The (possibly-multipart) ENTITY that was parsed.
A STATE indicating how we left things: "END" or "ERROR".
BEGIN
LET OUTER_DELIM = "--OUTER_BOUND".
LET OUTER_CLOSE = "--OUTER_BOUND--".
LET ENTITY = a new MIME entity object.
LET STATE = "OK".
Parse the (possibly empty) header, up to and including the
blank line that terminates it. Store it in the ENTITY.
IF the MIME type is "multipart":
LET INNER_BOUND = get multipart "boundary" from header.
LET INNER_DELIM = "--INNER_BOUND".
LET INNER_CLOSE = "--INNER_BOUND--".
Parse preamble:
REPEAT:
Read (and discard) next line
UNTIL (line is INNER_DELIM) OR we hit EOF (error).
Parse parts:
REPEAT:
LET (PART, STATE) = parse(FILEHANDLE, INNER_BOUND).
Add PART to ENTITY.
UNTIL (STATE != "DELIM").
Parse epilogue:
REPEAT (to parse epilogue):
Read (and discard) next line
UNTIL (line is OUTER_DELIM or OUTER_CLOSE) OR we hit EOF
LET STATE = "EOF", "DELIM", or "CLOSE" accordingly.
ELSE (if the MIME type is not "multipart"):
Open output destination (e.g., a file)
DO:
Read, decode, and output data from FILEHANDLE
UNTIL (line is OUTER_DELIM or OUTER_CLOSE) OR we hit EOF.
LET STATE = "EOF", "DELIM", or "CLOSE" accordingly.
ENDIF
RETURN (ENTITY, STATE).
END
28/Aug/1996 perl 5.005, patch 03 6
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)
For reasons discussed in MIME::Entity, we can't just
discard the "discard text": some mailers actually put data
in the preamble.
QUESTIONABLE PRACTICES
Multipart messages are always read line-by-line
Multipart document parts are read line-by-line, so
that the encapsulation boundaries may easily be
detected. However, bad MIME composition agents (for
example, naive CGI scripts) might return multipart
documents where the parts are, say, unencoded bitmap
files... and, consequently, where such "lines" might
be veeeeeeeeery long indeed.
A better solution for this case would be to set up
some form of state machine for input processing. This
will be left for future versions.
Multipart parts read into temp files before decoding
In my original implementation, the MIME::Decoder
classes had to be aware of encapsulation boundaries in
multipart MIME documents. While this decode-while-
parsing approach obviated the need for temporary
files, it resulted in inflexible and complex decoder
implementations.
The revised implementation uses temporary files (a la
tmpfile()) to hold the encoded portions of MIME
documents. Such files are deleted automatically after
decoding is done, and no more than one such file is
opened at a time, so you should never need to worry
about them.
Fuzzing of CRLF and newline on input
RFC-1521 dictates that MIME streams have lines
terminated by CRLF ("\r\n"). However, it is extremely
likely that folks will want to parse MIME streams
where each line ends in the local newline character
"\n" instead.
An attempt has been made to allow the parser to handle
both CRLF and newline-terminated input.
Fuzzing of CRLF and newline on output
The "7bit" and "8bit" decoders will decode both a "\n"
and a "\r\n" end-of-line sequence into a "\n".
The "binary" decoder (default if no encoding
specified) still outputs stuff verbatim... so a MIME
message with CRLFs and no explicit encoding will be
output as a text file that, on many systems, will have
an annoying ^M at the end of each line... but this is
as it should be.
28/Aug/1996 perl 5.005, patch 03 7
MIME::Parser(3)User Contributed Perl DocumentationMIME::Parser(3)CALL FOR TESTERS
If anyone wants to test out this package's handling of
both binary and textual email on a system where binmode()
is not a NOOP, I would be most grateful. If stuff breaks,
send me the pieces (including the original email that
broke it, and at the very least a description of how the
output was screwed up).
SEE ALSO
MIME::Decoder, MIME::Entity, MIME::Head, MIME::Parser.
AUTHOR
Copyright (c) 1996 by Eryq / eryq@rhine.gsfc.nasa.gov
All rights reserved. This program is free software; you
can redistribute it and/or modify it under the same terms
as Perl itself.
VERSION
$Revision: 1.14 $ $Date: 1996/07/06 05:28:29 $
28/Aug/1996 perl 5.005, patch 03 8