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MIME::Body(3)
NAME
MIME::Body - the body of a MIME message
SYNOPSIS
Before reading further, you should see MIME::Tools 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...
Obtaining bodies
### 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;
Opening, closing, and using IO handles
### 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: $!";
Other I/O
### 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 = $body->as_lines;
Working directly with paths to underlying files
### Where's the data?
if (defined($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;
DESCRIPTION
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:
1. Body object is created by a MIME::Parser during parsing. It's at this
point that the actual MIME::Body subclass is chosen, and 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).
2. Data is written to the body (usually by the MIME parser) like this: The
body is opened for writing, via "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().
3. Data is read from the body (usually by the user application) like this:
The body is opened for reading by a user application, via "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().
4. Body object is destructed.
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.
PUBLIC INTERFACE
new ARGS...
Class method, constructor. Create a new body. Any ARGS are sent to
init().
init ARGS...
Instance method, abstract, initiallizer. This is called automatically
by "new()", with the arguments given to "new()". The arguments are
optional, and entirely up to the subclass. The default method does
nothing,
as_lines
Instance method. Return the contents of the body as an array of lines
(each terminated by a newline, with the possible exception of the final
one). Returns empty on failure (NB: indistinguishable from an empty
body!).
Note: the default method gets the data via repeated getline() calls;
your subclass might wish to override this.
as_string
Instance method. Return the body data as a string (slurping it into
core if necessary). Best not to do this unless you're sure that the
body is reasonably small! Returns empty string for an empty body, and
undef on failure.
Note: the default method uses print(), which gets the data via repeated
read() calls; your subclass might wish to override this.
binmode [ONOFF]
Instance method. With argument, flags whether or not open() should
return an I/O handle which has binmode() activated. With no argument,
just returns the current value.
dup Instance method. Duplicate the bodyhandle.
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.
open READWRITE
Instance method, abstract. This should do whatever is necessary to open
the body for either writing (if READWRITE is "w") or reading (if mode
is "r").
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.
path [PATH]
Instance method. If you're storing the body data externally (e.g., in a
disk file), you'll want to give applications the ability to get at that
data, for cleanup. This method should return the path to the data, or
undef if there is none.
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.
print FILEHANDLE
Instance method. Output the body data to the given filehandle, or to
the currently-selected one if none is given.
purge
Instance method, abstract. Remove any data which resides external to
the program (e.g., in disk files). Immediately after a purge(), the
path() should return undef to indicate that the external data is no
longer available.
SUBCLASSES
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
MIME::Body::File
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.
MIME::Body::Scalar
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.
MIME::Body::InCore
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.
Defining your own subclasses
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
NOTES
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.
AUTHOR
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.
VERSION
$Revision: 1.8 $ $Date: 2005/01/13 19:23:15 $
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