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MIME::Parser::Filer(3)User
NAME
MIME::Parser::Filer - manage file-output of the parser
SYNOPSIS
Before reading further, you should see MIME::Parser to make sure that you
understand where this module fits into the grand scheme of things. Go on,
do it now. I'll wait.
Ready? Ok... now read "DESCRIPTION" below, and everything else should make
sense.
Public interface
### Create a "filer" of the desired class:
my $filer = MIME::Parser::FileInto->new($dir);
my $filer = MIME::Parser::FileUnder->new($basedir);
...
### Want added security? Don't let outsiders name your files:
$filer->ignore_filename(1);
### Prepare for the parsing of a new top-level message:
$filer->init_parse;
### Return the path where this message's data should be placed:
$path = $filer->output_path($head);
Semi-public interface
These methods might be overriden or ignored in some subclasses, so they
don't all make sense in all circumstances:
### Tweak the mapping from content-type to extension:
$emap = $filer->output_extension_map;
$emap->{"text/html"} = ".htm";
DESCRIPTION
How this class is used when parsing
When a MIME::Parser decides that it wants to output a file to disk, it uses
its "Filer" object -- an instance of a MIME::Parser::Filer subclass -- to
determine where to put the file.
Every parser has a single Filer object, which it uses for all parsing. You
can get the Filer for a given $parser like this:
$filer = $parser->filer;
At the beginning of each "parse()", the filer's internal state is reset by
the parser:
$parser->filer->init_parse;
The parser can then get a path for each entity in the message by handing
that entity's header (a MIME::Head) to the filer and having it do the work,
like this:
$new_file = $parser->filer->output_path($head);
Since it's nice to be able to clean up after a parse (especially a failed
parse), the parser tells the filer when it has actually used a path:
$parser->filer->purgeable($new_file);
Then, if you want to clean up the files which were created for a particular
parse (and also any directories that the Filer created), you would do this:
$parser->filer->purge;
Writing your own subclasses
There are two standard "Filer" subclasses (see below):
MIME::Parser::FileInto, which throws all files from all parses into the
same directory, and MIME::Parser::FileUnder (preferred), which creates a
subdirectory for each message. Hopefully, these will be sufficient for
most uses, but just in case...
The only method you have to override is output_path():
$filer->output_path($head);
This method is invoked by MIME::Parser when it wants to put a decoded
message body in an output file. The method should return a path to the
file to create. Failure is indicated by throwing an exception.
The path returned by "output_path()" should be "ready for open()": any
necessary parent directories need to exist at that point. These
directories can be created by the Filer, if course, and they should be
marked as purgeable() if a purge should delete them.
Actually, if your issue is more where the files go than what they're named,
you can use the default output_path() method and just override one of its
components:
$dir = $filer->output_dir($head);
$name = $filer->output_filename($head);
...
PUBLIC INTERFACE
MIME::Parser::Filer
This is the abstract superclass of all "filer" objects.
new INITARGS...
Class method, constructor. Create a new outputter for the given parser.
Any subsequent arguments are given to init(), which subclasses should
override for their own use (the default init does nothing).
results RESULTS
Instance method. Link this filer to a MIME::Parser::Results object
which will tally the messages. Notice that we avoid linking it to the
parser to avoid circular reference!
init_parse
Instance method. Prepare to start parsing a new message. Subclasses
should always be sure to invoke the inherited method.
evil_filename FILENAME
Instance method. Is this an evil filename; i.e., one which should not
be used in generating a disk file name? It is if any of these are
true:
* it is empty
* it is a string of dots: ".", "..", etc.
* it contains characters not in the set: "A" - "Z", "a" - "z",
"0" - "9", "-", "_", "+", "=", ".", ",", "@", "#",
"$", and " ".
* it is too long
If you just want to change this behavior, you should override this
method in the subclass of MIME::Parser::Filer that you use.
Warning: at the time this method is invoked, the FILENAME has already
been unmime'd into the local character set. If you're using any
character set other than ASCII, ISO-8859-*, or UTF-8, the
interpretation of the "path" characters might be very different, and
you will probably need to override this method. See "unmime" in
MIME::WordDecoder for more details.
Note: subclasses of MIME::Parser::Filer which override output_path()
might not consult this method; note, however, that the built-in
subclasses do consult it.
Thanks to Andrew Pimlott for finding a real dumb bug in the original
version. Thanks to Nickolay Saukh for noting that evil is in the eye
of the beholder.
exorcise_filename FILENAME
Instance method. If a given filename is evil (see "evil_filename") we
try to rescue it by performing some basic operations: shortening it,
removing bad characters, etc., and checking each against
evil_filename().
Returns the exorcised filename (which is guaranteed to not be evil), or
undef if it could not be salvaged.
Warning: at the time this method is invoked, the FILENAME has already
been unmime'd into the local character set. If you're using anything
character set other than ASCII, ISO-8859-*, or UTF-8, the
interpretation of the "path" characters might be very very different,
and you will probably need to override this method. See "unmime" in
MIME::WordDecoder for more details.
find_unused_path DIR, FILENAME
Instance method, subclasses only. We have decided on an output
directory and tentative filename, but there is a chance that it might
already exist. Keep adding a numeric suffix "-1", "-2", etc. to the
filename until an unused path is found, and then return that path.
The suffix is actually added before the first "." in the filename is
there is one; for example:
picture.gif archive.tar.gz readme
picture-1.gif archive-1.tar.gz readme-1
picture-2.gif archive-2.tar.gz readme-2
... ... ...
picture-10.gif
...
This can be a costly operation, and risky if you don't want files
renamed, so it is in your best interest to minimize situations where
these kinds of collisions occur. Unfortunately, if a multipart message
gives all of its parts the same recommended filename, and you are
placing them all in the same directory, this method might be
unavoidable.
ignore_filename [YESNO]
Instance method. Return true if we should always ignore recommended
filenames in messages, choosing instead to always generate our own
filenames. With argument, sets this value.
Note: subclasses of MIME::Parser::Filer which override output_path()
might not honor this setting; note, however, that the built-in
subclasses honor it.
output_dir HEAD
Instance method. Return the output directory for the given header. The
default method returns ".".
output_filename HEAD
Instance method, subclasses only. A given recommended filename was
either not given, or it was judged to be evil. Return a fake name,
possibly using information in the message HEADer. Note that this is
just the filename, not the full path.
Used by output_path(). If you're using the default "output_path()",
you probably don't need to worry about avoiding collisions with
existing files; we take care of that in find_unused_path().
output_prefix [PREFIX]
Instance method. Get the short string that all filenames for extracted
body-parts will begin with (assuming that there is no better
"recommended filename"). The default is "msg".
If PREFIX is not given, the current output prefix is returned. If
PREFIX is given, the output prefix is set to the new value, and the
previous value is returned.
Used by output_filename().
Note: subclasses of MIME::Parser::Filer which override output_path() or
output_filename() might not honor this setting; note, however, that the
built-in subclasses honor it.
output_type_ext
Instance method. Return a reference to the hash used by the default
output_filename() for mapping from content-types to extensions when
there is no default extension to use.
$emap = $filer->output_typemap;
$emap->{'text/plain'} = '.txt';
$emap->{'text/html'} = '.html';
$emap->{'text/*'} = '.txt';
$emap->{'*/*'} = '.dat';
Note: subclasses of MIME::Parser::Filer which override output_path() or
output_filename() might not consult this hash; note, however, that the
built-in subclasses consult it.
output_path HEAD
Instance method, subclasses only. Given a MIME head for a file to be
extracted, come up with a good output pathname for the extracted file.
This is the only method you need to worry about if you are building a
custom filer.
The default implementation does a lot of work; subclass implementers
really should try to just override its components instead of the whole
thing. It works basically as follows:
$directory = $self->output_dir($head);
$filename = $head->recommended_filename();
if (!$filename or
$self->ignore_filename() or
$self->evil_filename($filename)) {
$filename = $self->output_filename($head);
}
return $self->find_unused_path($directory, $filename);
Note: There are many, many, many ways you might want to control the
naming of files, based on your application. If you don't like the
behavior of this function, you can easily define your own subclass of
MIME::Parser::Filer and override it there.
Note: Nickolay Saukh pointed out that, given the subjective nature of
what is "evil", this function really shouldn't warn about an evil
filename, but maybe just issue a debug message. I considered that, but
then I thought: if debugging were off, people wouldn't know why (or
even if) a given filename had been ignored. In mail robots that depend
on externally-provided filenames, this could cause hard-to-diagnose
problems. So, the message is still a warning.
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.
purge
Instance method, final. Purge all files/directories created by the last
parse. This method simply goes through the purgeable list in reverse
order (see "purgeable") and removes all existing files/directories in
it. You should not need to override this method.
purgeable [FILE]
Instance method, final. Add FILE to the list of "purgeable"
files/directories (those which will be removed if you do a "purge()").
You should not need to override this method.
If FILE is not given, the "purgeable" list is returned. This may be
used for more-sophisticated purging.
As a special case, invoking this method with a FILE that is an arrayref
will replace the purgeable list with a copy of the array's contents, so
[] may be used to clear the list.
Note that the "purgeable" list is cleared when a parser begins a new
parse; therefore, if you want to use purge() to do cleanup, you must do
so before starting a new parse!
MIME::Parser::FileInto
This concrete subclass of MIME::Parser::Filer supports filing into a given
directory.
init DIRECTORY
Instance method, initiallizer. Set the directory where all files will
go.
MIME::Parser::FileUnder
This concrete subclass of MIME::Parser::Filer supports filing under a given
directory, using one subdirectory per message, but with all message parts
in the same directory.
init BASEDIR, OPTSHASH...
Instance method, initiallizer. Set the base directory which will
contain the message directories. If used, then each parse of begins by
creating a new subdirectory of BASEDIR where the actual parts of the
message are placed. OPTSHASH can contain the following:
DirName
Explicitly set the name of the subdirectory which is created. The
default is to use the time, process id, and a sequence number, but
you might want a predictable directory.
Purge
Automatically purge the contents of the directory (including all
subdirectories) before each parse. This is really only needed if
using an explicit DirName, and is provided as a convenience only.
Currently we use the 1-arg form of File::Path::rmtree; you should
familiarize yourself with the caveats therein.
The output_dir() will return the path to this message-specific
directory until the next parse is begun, so you can do this:
use File::Path;
$parser->output_under("/tmp");
$ent = eval { $parser->parse_open($msg); }; ### parse
if (!$ent) { ### parse failed
rmtree($parser->output_dir);
die "parse failed: $@";
}
else { ### parse succeeded
...do stuff...
}
AUTHOR
Eryq (eryq@zeegee.com), ZeeGee Software Inc (http://www.zeegee.com).
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: 1.5 $
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