Ubuntu Manpage: MIME::Parser::Filer - manage file-output of the parser

Provided by: libmime-tools-perl_5.514-1_all

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 overridden 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 or entirely whitespace
* it contains leading or trailing whitespace
* 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.

perl v5.38.2                                       2024-02-09                           MIME::Parser::Filer(3pm)

NAME

SYNOPSIS

DESCRIPTION

PUBLIC INTERFACE

SEE ALSO

AUTHOR