Mail::Message::Field(3User Contributed Perl DocumentatiMail::Message::Field(3)NAMEMail::Message::Field - one line of a message header
INHERITANCEMail::Message::Field
is a Mail::Reporter
Mail::Message::Field is extended by
Mail::Message::Field::Fast
Mail::Message::Field::Flex
Mail::Message::Field::Full
SYNOPSIS
my $field = Mail::Message::Field->new(From => 'fish@tux.aq');
print $field->name;
print $field->body;
print $field->comment;
print $field->content; # body & comment
$field->print(\*OUT);
print $field->string;
print "$field\n";
print $field->attribute('charset') || 'us-ascii';
DESCRIPTION
This implementation follows the guidelines of rfc2822 as close as
possible, and may there produce a different output than implementations
based on the obsolete rfc822. However, the old output will still be
accepted.
These objects each store one header line, and facilitates access
routines to the information hidden in it. Also, you may want to have a
look at the added methods of a message:
my @from = $message->from;
my $sender = $message->sender;
my $subject = $message->subject;
my $msgid = $message->messageId;
my @to = $message->to;
my @cc = $message->cc;
my @bcc = $message->bcc;
my @dest = $message->destinations;
my $other = $message->get('Reply-To');
OVERLOADED
overload: ""
(stringification) produces the unfolded body of the field, which
may be what you expect. This is what makes what the field object
seems to be a simple string. The string is produced by
unfoldedBody().
example:
print $msg->get('subject'); # via overloading
print $msg->get('subject')->unfoldedBody; # same
my $subject = $msg->get('subject') || 'your mail';
print "Re: $subject\n";
overload: +0
(numification) When the field is numeric, the value will be
returned. The result is produced by toInt(). If the value is not
correct, a 0 is produced, to simplify calculations.
overload: <=>
(numeric comparison) Compare the integer field contents with
something else.
example:
if($msg->get('Content-Length') > 10000) ...
if($msg->size > 10000) ... ; # same, but better
overload: bool
Always true, to make it possible to say "if($field)".
overload: cmp
(string comparison) Compare the unfolded body of a field with an
other field or a string, using the buildin "cmp".
METHODS
Constructors
$obj->clone
Create a copy of this field object.
Mail::Message::Field->new(DATA)
See Mail::Message::Field::Fast::new(),
Mail::Message::Field::Flex::new(), and
Mail::Message::Field::Full::new(). By default, a "Fast" field is
produced.
-Option--Defined in --Default
log Mail::Reporter 'WARNINGS'
trace Mail::Reporter 'WARNINGS'
log => LEVEL
trace => LEVEL
The field
$obj->isStructured
Mail::Message::Field->isStructured
Some fields are described in the RFCs as being structured: having a
well described syntax. These fields have common ideas about
comments and the like, what they do not share with unstructured
fields, like the "Subject" field.
example:
my $field = Mail::Message::Field->new(From => 'me');
if($field->isStructured)
Mail::Message::Field->isStructured('From');
$obj->length
Returns the total length of the field in characters, which includes
the field's name, body and folding characters.
$obj->nrLines
Returns the number of lines needed to display this header-line.
$obj->print([FILEHANDLE])
Print the whole header-line to the specified file-handle. One line
may result in more than one printed line, because of the folding of
long lines. The FILEHANDLE defaults to the selected handle.
$obj->size
Returns the number of bytes needed to display this header-line,
Same as length().
$obj->string([WRAP])
Returns the field as string. By default, this returns the same as
folded(). However, the optional WRAP will cause to re-fold to take
place (without changing the folding stored inside the field).
$obj->toDisclose
Returns whether this field can be disclosed to other people, for
instance when sending the message to an other party. Returns a
"true" or "false" condition. See also
Mail::Message::Head::Complete::printUndisclosed().
Access to the name
$obj->Name
Returns the name of this field in original casing. See name() as
well.
$obj->name
Returns the name of this field, with all characters lower-cased for
ease of comparison. See Name() as well.
$obj->wellformedName([STRING])
(Instance method class method) As instance method, the current
field's name is correctly formatted and returned. When a STRING is
used, that one is formatted.
example:
print Mail::Message::Field->Name('content-type')
# --> Content-Type
my $field = $head->get('date');
print $field->Name;
# --> Date
Access to the body
$obj->body
This method may be what you want, but usually, the foldedBody() and
unfoldedBody() are what you are looking for. This method is
cultural heritage, and should be avoided.
Returns the body of the field. When this field is structured, it
will be stripped from everything what is behind the first semi-
color (";"). In any case, the string is unfolded. Whether the
field is structured is defined by isStructured().
$obj->folded
Returns the folded version of the whole header. When the header is
shorter than the wrap length, a list of one line is returned.
Otherwise more lines will be returned, all but the first starting
with at least one blank. See also foldedBody() to get the same
information without the field's name.
In scalar context, the lines are delived into one string, which is
a little faster because that's the way they are stored
internally...
example:
my @lines = $field->folded;
print $field->folded;
print scalar $field->folded; # faster
$obj->foldedBody([BODY])
Returns the body as a set of lines. In scalar context, this will be
one line containing newlines. Be warned about the newlines when
you do pattern-matching on the result of thie method.
The optional BODY argument changes the field's body. The folding
of the argument must be correct.
$obj->stripCFWS([STRING])
Mail::Message::Field->stripCFWS([STRING])
Remove the comments and folding white spaces from the STRING.
Without string and only as instance method, the unfoldedBody() is
being stripped and returned.
WARNING: This operation is only allowed for structured header
fields (which are defined by the various RFCs as being so. You
don't want parts within braces which are in the Subject header line
to be removed, to give an example.
$obj->unfoldedBody([BODY, [WRAP]])
Returns the body as one single line, where all folding information
(if available) is removed. This line will also NOT end on a new-
line.
The optional BODY argument changes the field's body. The right
folding is performed before assignment. The WRAP may be specified
to enforce a folding size.
example:
my $body = $field->unfoldedBody;
print "$field"; # via overloading
Access to the content
$obj->addresses
Returns a list of Mail::Address objects, which represent the e-mail
addresses found in this header line.
example:
my @addr = $message->head->get('to')->addresses;
my @addr = $message->to;
$obj->attribute(NAME [, VALUE])
Get the value of an attribute, optionally after setting it to a new
value. Attributes are part of some header lines, and hide
themselves in the comment field. If the attribute does not exist,
then "undef" is returned. The attribute is still encoded.
example:
my $field = Mail::Message::Field->new(
'Content-Type: text/plain; charset="us-ascii"');
print $field->attribute('charset');
# --> us-ascii
print $field->attribute('bitmap') || 'no'
# --> no
$field->atrribute(filename => '/tmp/xyz');
$field->print;
# --> Content-Type: text/plain; charset="us-ascii";
# filename="/tmp/xyz"
# Automatically folded, and no doubles created.
$obj->attributes
Returns a list of key-value pairs, where the values are not yet
decoded.
example:
my %attributes = $head->get('Content-Disposition')->attributes;
$obj->comment([STRING])
Returns the unfolded comment (part after a semi-colon) in a
structureed header-line. optionally after setting it to a new
STRING first. When "undef" is specified as STRING, the comment is
removed. Whether the field is structured is defined by
isStructured().
The comment part of a header field often contains "attributes".
Often it is preferred to use attribute() on them.
$obj->study
Study the header field in detail: turn on the full parsing and
detailed understanding of the content of the fields.
Mail::Message::Field::Fast and Mail::Message::Field::Fast objects
will be transformed into any Mail::Message::Field::Full object.
example:
my $subject = $msg->head->get('subject')->study;
my $subject = $msg->head->study('subject'); # same
my $subject = $msg->study('subject'); # same
$obj->toDate([TIME])
Mail::Message::Field->toDate([TIME])
Convert a timestamp into an rfc2822 compliant date format. This
differs from the default output of "localtime" in scalar context.
Without argument, the "localtime" is used to get the current time.
TIME can be specified as one numeric (like the result of "time()")
and as list (like produced by c<localtime()> in list context).
Be sure to have your timezone set right, especially when this
script runs automatically.
example:
my $now = time;
Mail::Message::Field->toDate($now);
Mail::Message::Field->toDate(time);
Mail::Message::Field->toDate(localtime);
Mail::Message::Field->toDate; # same
# returns someting like:
# Wed, 28 Aug 2002 10:40:25 +0200
$obj->toInt
Returns the value which is related to this field as integer. A
check is performed whether this is right.
Other methods
$obj->dateToTimestamp(STRING)
Mail::Message::Field->dateToTimestamp(STRING)
Convert a STRING which represents and RFC compliant time string
into a timestamp like is produced by the "time" function.
Internals
$obj->consume(LINE | (NAME,BODY|OBJECTS))
Accepts a whole field LINE, or a pair with the field's NAME and
BODY. In the latter case, the BODY data may be specified as array
of OBJECTS which are stringified. Returned is a nicely formatted
pair of two strings: the field's name and a folded body.
This method is called by new(), and usually not by an application
program. The details about converting the OBJECTS to a field
content are explained in "Specifying field data".
$obj->defaultWrapLength([LENGTH])
Any field from any header for any message will have this default
wrapping. This is maintained in one global variable. Without a
specified LENGTH, the current value is returned. The default is
78.
$obj->fold(NAME, BODY, [MAXCHARS])
Mail::Message::Field->fold(NAME, BODY, [MAXCHARS])
Make the header field with NAME fold into multiple lines. Wrapping
is performed by inserting newlines before a blanks in the BODY,
such that no line exceeds the MAXCHARS and each line is as long as
possible.
The RFC requests for folding on nice spots, but this request is
mainly ignored because it would make folding too slow.
$obj->setWrapLength([LENGTH])
Force the wrapping of this field to the specified LENGTH
characters. The wrapping is performed with fold() and the results
stored within the field object.
example: refolding the field
$field->setWrapLength(99);
$obj->stringifyData(STRING|ARRAY|OBJECTS)
This method implements the translation of user supplied objects
into ascii fields. The process is explained in "Specifying field
data".
$obj->unfold(STRING)
The reverse action of fold(): all lines which form the body of a
field are joined into one by removing all line terminators (even
the last). Possible leading blanks on the first line are removed
as well.
Error handling
$obj->AUTOLOAD
See "Error handling" in Mail::Reporter
$obj->addReport(OBJECT)
See "Error handling" in Mail::Reporter
$obj->defaultTrace([LEVEL]|[LOGLEVEL, TRACELEVEL]|[LEVEL, CALLBACK])
Mail::Message::Field->defaultTrace([LEVEL]|[LOGLEVEL,
TRACELEVEL]|[LEVEL, CALLBACK])
See "Error handling" in Mail::Reporter
$obj->errors
See "Error handling" in Mail::Reporter
$obj->log([LEVEL [,STRINGS]])
Mail::Message::Field->log([LEVEL [,STRINGS]])
See "Error handling" in Mail::Reporter
$obj->logPriority(LEVEL)
Mail::Message::Field->logPriority(LEVEL)
See "Error handling" in Mail::Reporter
$obj->logSettings
See "Error handling" in Mail::Reporter
$obj->notImplemented
See "Error handling" in Mail::Reporter
$obj->report([LEVEL])
See "Error handling" in Mail::Reporter
$obj->reportAll([LEVEL])
See "Error handling" in Mail::Reporter
$obj->trace([LEVEL])
See "Error handling" in Mail::Reporter
$obj->warnings
See "Error handling" in Mail::Reporter
Cleanup
$obj->DESTROY
See "Cleanup" in Mail::Reporter
$obj->inGlobalDestruction
See "Cleanup" in Mail::Reporter
DETAILS
Field syntax
Folding fields
Fields which are long can be folded to span more than one line. The
real limit for lines in messages is only at 998 characters, however
such long lines are not easy to read without support of an application.
Therefore rfc2822 (which defines the message syntax) specifies
explicitly that field lines can be re-formatted into multiple sorter
lines without change of meaning, by adding new-line characters to any
field before any blank or tab.
Usually, the lines are reformatted to create lines which are 78
characters maximum. Some applications try harder to fold on nice spots,
like before attributes. Especially the "Received" field is often
manually folded into some nice layout. In most cases however, it is
preferred to produce lines which are as long as possible but max 78.
BE WARNED that all fields can be subjected to folding, and that you
usually want the unfolded value.
Structured fields
The rfc2822 describes a large number of header fields explicitly.
These fields have a defined meaning. For some of the fields, like the
"Subject" field, the meaning is straight forward the contents itself.
These fields are the Unstructured Fields.
Other fields have a well defined internal syntax because their content
is needed by e-mail applications. For instance, the "To" field contains
addresses which must be understood by all applications in the same way.
These are the Structured Fields, see isStructured().
Comments in fields
Stuctured fields can contain comments, which are pieces of text
enclosed in parenthesis. These comments can be placed close to
anywhere in the line and must be ignored be the application. Not all
applications are capable of handling comments correctly in all
circumstances.
Fields are stored in the header of a message, which are represented by
Mail::Message::Head objects. A field is a combination of a name, body,
and attributes. Especially the term "body" is cause for confusion:
sometimes the attributes are considered to be part of the body.
The name of the field is followed by a colon ("":"", not preceded by
blanks, but followed by one blank). Each attribute is preceded by a
separate semi-colon ("";""). Names of fields are case-insensitive and
cannot contain blanks.
Getting a field
Using get() field
The "get()" interface is copied from other Perl modules which can
handle e-mail messages. Many applications which simply replace
Mail::Internet objects by Mail::Message objects will work without
modification.
There is more than one get method. The exact results depend on which
get you use. When Mail::Message::get() is called, you will get the
unfolded, stripped from comments, stripped from attributes contents of
the field as string. Character-set encodings will still be in the
string. If the same fieldname appears more than once in the header,
only the last value is returned.
When Mail::Message::Head::get() is called in scalar context, the last
field with the specified name is returned as field object. This object
strinigfies into the unfolded contents of the field, including
attributes and comments. In list context, all appearances of the field
in the header are returned as objects.
BE WARNED that some lines seem unique, but are not according to the
official rfc. For instance, "To" fields can appear more than once. If
your program calls "get('to')" in scalar context, some information is
lost.
Using study() field
As the name "study" already implies, this way of accessing the fields
is much more thorough but also slower. The "study" of a field is like
a "get", but provides easy access to the content of the field and
handles character-set decoding correctly.
The Mail::Message::study() method will only return the last field with
that name as object. Mail::Message::Head::study() and
Mail::Message::Field::study() return all fields when used in list
context.
Using resent groups
Some fields belong together in a group of fields. For instance, a set
of lines is used to define one step in the mail transport process.
Each step adds a "Received" line, and optionally some "Resent-*" lines
and "Return-Path". These groups of lines shall stay together and in
order when the message header is processed.
The "Mail::Message::Head::ResentGroup" object simplifies the access to
these related fields. These resent groups can be deleted as a whole,
or correctly constructed.
As many programs as there are handling e-mail, as many variations on
accessing the header information are requested. Be careful which way
you access the data: read the variations described here and decide
which solution suites your needs best.
The field's data
Access to the field
· string()
Returns the text of the body exactly as will be printed to file
when print() is called, so name, main body, and attributes.
· foldedBody()
Returns the text of the body, like string(), but without the name
of the field.
· unfoldedBody()
Returns the text of the body, like foldedBody(), but then with all
new-lines removed. This is the normal way to get the content of
unstructured fields. Character-set encodings will still be in
place. Fields are stringified into their unfolded representation.
· stripCFWS()
Returns the text of structured fields, where new-lines and comments
are removed from the string. This is a good start for parsing the
field, for instance to find e-mail addresses in them.
· Mail::Message::Field::Full::decodedBody()
Studied fields can produce the unfolded text decoded into utf8
strings. This is an expensive process, but the only correct way to
get the field's data. More useful for people who are not living in
ASCII space.
· Studied fields
Studied fields have powerful methods to provide ways to access and
produce the contents of (structured) fields exactly as the involved
rfcs prescribe.
Using simplified field access
Some fields are accessed that often that there are support methods to
provide simplified access. All these methods are called upon a message
directly.
Specifying field data
Field data can be anything, strongly dependent on the type of field at
hand. If you decide to contruct the fields very carefully via some
Mail::Message::Field::Full extension (like via
Mail::Message::Field::Addresses objects), then you will have protection
build-in. However, you can bluntly create any Mail::Message::Field
object based on some data.
When you create a field, you may specify a string, object, or an array
of strings and objects. On the moment, objects are only used to help
the construction on e-mail addresses, however you may add some of your
own.
The following rules (implemented in stringifyData()) are obeyed given
the argument is:
· a string
The string must be following the (complicated) rules of the
rfc2822, and is made field content as specified. When the string
is not terminated by a new-line ("\n") it will be folded according
to the standard rules.
· a Mail::Address object
The most used Perl object to parse and produce address lines. This
object does not understand character set encodings in phrases.
· a Mail::Identity object
As part of the User::Identity distribution, this object has full
understanding of the meaning of one e-mail address, related to a
person. All features defined by rfc2822 are implemented.
· a User::Identity object
A person is specified, which may have more than one
Mail::Identity's defined. Some methods, like
Mail::Message::reply() and Mail::Message::forward() try to select
the right e-mail address smart (see their method descriptions), but
in other cases the first e-mail address found is used.
· a User::Identity::Collection::Emails object
All Mail::Identity objects in the collection will be included in
the field as a group carying the name of the collection.
· any other object
For all other objects, the stringification overload is used to
produce the field content.
· an ARRAY
You may also specify an array with a mixture of any of the above.
The elements will be joined as comma-separated list. If you do not
want comma's inbetween, you will have to process the array
yourself.
There are many ways to get the fields info as object, and there are
also many ways to process this data within the field.
Field class implementation
For performance reasons only, there are three types of fields: the
fast, the flexible, and the full understander:
· Mail::Message::Field::Fast
"Fast" objects are not derived from a "Mail::Reporter". The
consideration is that fields are so often created, and such a small
objects at the same time, that setting-up a logging for each of the
objects is relatively expensive and not really useful. The fast
field implementation uses an array to store the data: that will be
faster than using a hash. Fast fields are not easily inheritable,
because the object creation and initiation is merged into one
method.
· Mail::Message::Field::Flex
The flexible implementation uses a hash to store the data. The
new() and "init" methods are split, so this object is extensible.
· Mail::Message::Field::Full
With a full implementation of all applicable RFCs (about 5), the
best understanding of the fields is reached. However, this comes
with a serious memory and performance penalty. These objects are
created from fast or flex header fields when study() is called.
DIAGNOSTICS
Warning: Field content is not numerical: $content
The numeric value of a field is requested (for instance the "Lines"
or "Content-Length" fields should be numerical), however the data
contains weird characters.
Warning: Illegal character in field name $name
A new field is being created which does contain characters not
permitted by the RFCs. Using this field in messages may break
other e-mail clients or transfer agents, and therefore mutulate or
extinguish your message.
Error: Package $package does not implement $method.
Fatal error: the specific package (or one of its superclasses) does
not implement this method where it should. This message means that
some other related classes do implement this method however the
class at hand does not. Probably you should investigate this and
probably inform the author of the package.
SEE ALSO
This module is part of Mail-Box distribution version 2.097, built on
January 26, 2011. Website: http://perl.overmeer.net/mailbox/
LICENSE
Copyrights 2001-2011 by Mark Overmeer. For other contributors see
ChangeLog.
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself. See
http://www.perl.com/perl/misc/Artistic.html
perl v5.14.1 2011-01-26 Mail::Message::Field(3)
