|
MIME::Body - the body of a MIME message |
MIME::Body - the body of a MIME message
Before reading further, you should see the MIME::Tools manpage 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...
### Get the bodyhandle of a MIME::Entity object: $body = $entity->bodyhandle;
### Create a body which stores data in a disk file: $body = new MIME::Body::File "/path/to/file";
### Create a body which stores data in an in-core array: $body = new MIME::Body::InCore \@strings;
### Write data to the body:
$IO = $body->open("w") || die "open body: $!";
$IO->print($message);
$IO->close || die "close I/O handle: $!";
### Read data from the body (in this case, line by line):
$IO = $body->open("r") || die "open body: $!";
while (defined($_ = $IO->getline)) {
### do stuff
}
$IO->close || die "close I/O handle: $!";
### Dump the ENCODED body data to a filehandle: $body->print(\*STDOUT);
### Slurp all the UNENCODED data in, and put it in a scalar: $string = $body->as_string;
### Slurp all the UNENCODED data in, and put it in an array of lines: @lines = $body->as_lines;
### Where's the data?
if (defined($body->path)) { ### data is on disk:
print "data is stored externally, in ", $body->path;
}
else { ### data is in core:
print "data is already in core, and is...\n", $body->as_string;
}
### Get rid of anything on disk: $body->purge;
MIME messages can be very long (e.g., tar files, MPEGs, etc.) or very short (short textual notes, as in ordinary mail). Long messages are best stored in files, while short ones are perhaps best stored in core.
This class is an attempt to define a common interface for objects which contain message data, regardless of how the data is physically stored. The lifespan of a ``body'' object usually looks like this:
new() is invoked. (For example: if the body data is going to
a file, then it is at this point that the class MIME::Body::File,
and the filename, is chosen).
open("w"). This will trash any
previous contents, and return an ``I/O handle'' opened for writing.
Data is written to this I/O handle, via print().
Then the I/O handle is closed, via close().
open("r").
This will return an ``I/O handle'' opened for reading.
Data is read from the I/O handle, via read(), getline(), or getlines().
Then the I/O handle is closed, via close().
You can write your own subclasses, as long as they follow the interface described below. Implementers of subclasses should assume that steps 2 and 3 may be repeated any number of times, and in different orders (e.g., 1-2-2-3-2-3-3-3-3-3-2-4).
In any case, once a MIME::Body has been created, you ask to open it for reading or writing, which gets you an ``i/o handle'': you then use the same mechanisms for reading from or writing to that handle, no matter what class it is.
Beware: unless you know for certain what kind of body you have, you should not assume that the body has an underlying filehandle.
new(), with the arguments given
to new(). The arguments are optional, and entirely up to the
subclass. The default method does nothing,
Note: the default method gets the data via
repeated getline() calls; your subclass might wish to override this.
Note: the default method uses print(), which gets the data via
repeated read() calls; your subclass might wish to override this.
open() should return an I/O handle
which has binmode() activated. With no argument, just returns the
current value.
Beware: external data in bodyhandles is not copied to new files! Changing the data in one body's data file, or purging that body, will affect its duplicate. Bodies with in-core data probably need not worry.
This method is expected to return an ``I/O handle'' object on success, and undef on error. An I/O handle can be any object that supports a small set of standard methods for reading/writing data. See the IO::Handle class for an example.
Where appropriate, the path should be a simple string, like a filename. With argument, sets the PATH, which should be undef if there is none.
path() should return undef to indicate
that the external data is no longer available.
The following built-in classes are provided:
Body Stores body When open()ed, class: data in: returns: -------------------------------------------------------- MIME::Body::File disk file IO::Handle MIME::Body::Scalar scalar IO::Scalar MIME::Body::InCore scalar array IO::ScalarArray
A body class that stores the data in a disk file. The I/O handle is a wrapped filehandle. Invoke the constructor as:
$body = new MIME::Body::File "/path/to/file";
In this case, the path() method would return the given path,
so you could say:
if (defined($body->path)) {
open BODY, $body->path or die "open: $!";
while (<BODY>) {
### do stuff
}
close BODY;
}
But you're best off not doing this.
A body class that stores the data in-core, in a simple scalar. Invoke the constructor as:
$body = new MIME::Body::Scalar \$string;
A single scalar argument sets the body to that value, exactly as though you'd opened for the body for writing, written the value, and closed the body again:
$body = new MIME::Body::Scalar "Line 1\nLine 2\nLine 3";
A single array reference sets the body to the result of joining all the elements of that array together:
$body = new MIME::Body::Scalar ["Line 1\n",
"Line 2\n",
"Line 3"];
Uses IO::Scalar as the I/O handle.
A body class that stores the data in-core. Invoke the constructor as:
$body = new MIME::Body::InCore \$string;
$body = new MIME::Body::InCore $string;
$body = new MIME::Body::InCore \@stringarray
A simple scalar argument sets the body to that value, exactly as though you'd opened for the body for writing, written the value, and closed the body again:
$body = new MIME::Body::InCore "Line 1\nLine 2\nLine 3";
A single array reference sets the body to the concatenation of all scalars that it holds:
$body = new MIME::Body::InCore ["Line 1\n",
"Line 2\n",
"Line 3"];
Uses IO::ScalarArray as the I/O handle.
So you're not happy with files and scalar-arrays?
No problem: just define your own MIME::Body subclass, and make a subclass
of MIME::Parser or MIME::ParserBase which returns an instance of your
body class whenever appropriate in the new_body_for(head) method.
Your ``body'' class must inherit from MIME::Body (or some subclass of it), and it must either provide (or inherit the default for) the following methods...
The default inherited method should suffice for all these:
new
binmode [ONOFF]
path
The default inherited method may suffice for these, but perhaps there's a better implementation for your subclass.
init ARGS...
as_lines
as_string
dup
print
purge
The default inherited method will probably not suffice for these:
open
One reason I didn't just use FileHandle or IO::Handle objects for message bodies was that I wanted a ``body'' object to be a form of completely encapsulated program-persistent storage; that is, I wanted users to be able to write code like this...
### Get body handle from this MIME message, and read its data:
$body = $entity->bodyhandle;
$IO = $body->open("r");
while (defined($_ = $IO->getline)) {
print STDOUT $_;
}
$IO->close;
...without requiring that they know anything more about how the $body object is actually storing its data (disk file, scalar variable, array variable, or whatever).
Storing the body of each MIME message in a persistently-open IO::Handle was a possibility, but it seemed like a bad idea, considering that a single multipart MIME message could easily suck up all the available file descriptors on some systems. This risk increases if the user application is processing more than one MIME entity at a time.
Eryq (eryq@zeegee.com), ZeeGee Software Inc (http://www.zeegee.com). David F. Skoll (dfs@roaringpenguin.com) http://www.roaringpenguin.com
All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
Thanks to Achim Bohnet for suggesting that MIME::Parser not be restricted to the use of FileHandles.
$Revision: 1.8 $ $Date: 2005/01/13 19:23:15 $
|
MIME::Body - the body of a MIME message |