Provided by: libmail-message-perl_3.012-1_all 
NAME
Mail::Message::Head - the header of one message
INHERITANCE
Mail::Message::Head
is a Mail::Reporter
Mail::Message::Head is extended by
Mail::Message::Head::Complete
Mail::Message::Head::Delayed
Mail::Message::Head::Subset
SYNOPSIS
my $head = Mail::Message::Head->new;
$head->add('From: me@localhost');
$head->add(From => 'me@localhost');
$head->add(Mail::Message::Field->new(From => 'me'));
my $subject = $head->get('subject');
my @rec = $head->get('received');
$head->delete('From');
DESCRIPTION
"Mail::Message::Head" MIME headers are part of Mail::Message messages, which are grouped
in Mail::Box folders.
ATTENTION!!! most functionality about e-mail headers is described in
Mail::Message::Head::Complete, which is a matured header object. Other kinds of headers
will be translated to that type when time comes.
On this page, the general methods which are available on any header are described. Read
about differences in the sub-class specific pages.
Extends "DESCRIPTION" in Mail::Reporter.
OVERLOADED
overload: ""
(stringifaction) The header, when used as string, will format as if
Mail::Message::Head::Complete::string() was called, so return a nicely folder full
header. An exception is made for Carp, which will get a simplified string to avoid
unreadible messages from "croak" and "confess".
example: using a header object as string
print $head; # implicit stringification by print
$head->print; # the same
print "$head"; # explicit stringication
overload: bool
When the header does not contain any lines (which is illegal, according to the RFCs),
false is returned. In all other cases, a true value is produced.
METHODS
Extends "METHODS" in Mail::Reporter.
Constructors
Extends "Constructors" in Mail::Reporter.
Mail::Message::Head->build( [PAIR|$field]-LIST )
A fast way to construct a header with many lines. The PAIRs are "(name, content)"
pairs of the header, but it is also possible to pass Mail::Message::Field objects. A
Mail::Message::Head::Complete header is created by simply calling
Mail::Message::Head::Complete::build(), and then each field is added. Double field
names are permitted.
example:
my $subject = Mail::Message::Field->new(Subject => 'xyz');
my $head = Mail::Message::Head->build
( From => 'me@example.com'
, To => 'you@anywhere.aq'
, $subject
, Received => 'one'
, Received => 'two'
);
print ref $head;
# --> Mail::Message::Head::Complete
Mail::Message::Head->new(%options)
Create a new message header object. The object will store all the fields of a header.
When you get information from the header, it will be returned to you as
Mail::Message::Field objects, although the fields may be stored differently
internally.
If you try to instantiate a Mail::Message::Head, you will automatically be upgraded to
a Mail::Message::Head::Complete --a full head.
-Option --Defined in --Default
field_type Mail::Message::Field::Fast
log Mail::Reporter 'WARNINGS'
message undef
modified <false>
trace Mail::Reporter 'WARNINGS'
field_type => CLASS
The type of objects that all the fields will have. This must be an extension of
Mail::Message::Field.
log => LEVEL
message => MESSAGE
The MESSAGE where this header belongs to. Usually, this is not known at creation of
the header, but sometimes it is. If not, call the message() method later to set it.
modified => BOOLEAN
trace => LEVEL
The header
$obj->isDelayed()
Headers may only be partially read, in which case they are called delayed. This
method returns true if some header information still needs to be read. Returns false
if all header data has been read. Will never trigger completion.
$obj->isEmpty()
Are there any fields defined in the current header? Be warned that the header will
not be loaded for this: delayed headers will return true in any case.
$obj->isModified()
Returns whether the header has been modified after being read.
example:
if($head->isModified) { ... }
$obj->knownNames()
Like Mail::Message::Head::Complete::names(), but only returns the known header fields,
which may be less than "names" for header types which are partial. "names()" will
trigger completion, where "knownNames()" does not.
$obj->message( [$message] )
Get (after setting) the message where this header belongs to. This does not trigger
completion.
$obj->modified( [BOOLEAN] )
Sets the modified flag to BOOLEAN. Without value, the current setting is returned,
but in that case you can better use isModified(). Changing this flag will not trigger
header completion.
example:
$head->modified(1);
if($head->modified) { ... }
if($head->isModified) { ... }
$obj->orderedFields()
Returns the fields ordered the way they were read or added.
Access to the header
$obj->get( $name, [$index] )
Get the data which is related to the field with the $name. The case of the characters
in $name does not matter.
If there is only one data element defined for the $name, or if there is an $index
specified as the second argument, only the specified element will be returned. If the
field $name matches more than one header the return value depends on the context. In
LIST context, all values will be returned in the order they are read. In SCALAR
context, only the last value will be returned.
example:
my $head = Mail::Message::Head->new;
$head->add('Received: abc');
$head->add('Received: xyz');
$head->add('Subject: greetings');
my @rec_list = $head->get('Received');
my $rec_scalar = $head->get('Received');
print ",@rec_list,$rec_scalar," # ,abc xyz, xyz,
print $head->get('Received', 0); # abc
my @sub_list = $head->get('Subject');
my $sub_scalar = $head->get('Subject');
print ",@sub_list,$sub_scalar," # ,greetings, greetings,
$obj->study( $name, [$index] )
Like get(), but puts more effort in understanding the contents of the field.
Mail::Message::Field::study() will be called for the field with the specified
FIELDNAME, which returns Mail::Message::Field::Full objects. In scalar context only
the last field with that name is returned. When an $index is specified, that element
is returned.
About the body
$obj->guessBodySize()
Try to estimate the size of the body of this message, but without parsing the header
or body. The result might be "undef" or a few percent of the real size. It may even
be very far of the real value, that's why this is a guess.
$obj->isMultipart()
Returns whether the body of the related message is a multipart body. May trigger
completion, when the "Content-Type" field is not defined.
Internals
$obj->addNoRealize($field)
Add a field, like Mail::Message::Head::Complete::add() does, but avoid the loading of
a possibly partial header. This method does not test the validity of the argument,
nor flag the header as changed. This does not trigger completion.
$obj->addOrderedFields($fields)
$obj->fileLocation()
Returns the location of the header in the file, as a pair begin and end. The begin is
the first byte of the header. The end is the first byte after the header.
$obj->load()
Be sure that the header is loaded. This returns the loaded header object.
$obj->moveLocation($distance)
Move the registration of the header in the file.
$obj->read($parser)
Read the header information of one message into this header structure. This method is
called by the folder object (some Mail::Box sub-class), which passes the $parser as an
argument.
$obj->setNoRealize($field)
Set a field, but avoid the loading of a possibly partial header as set() does. This
method does not test the validity of the argument, nor flag the header as changed.
This does not trigger completion.
Error handling
Extends "Error handling" in Mail::Reporter.
$obj->AUTOLOAD()
Inherited, see "Error handling" in Mail::Reporter
$obj->addReport($object)
Inherited, see "Error handling" in Mail::Reporter
$obj->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
Mail::Message::Head->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
Inherited, see "Error handling" in Mail::Reporter
$obj->errors()
Inherited, see "Error handling" in Mail::Reporter
$obj->log( [$level, [$strings]] )
Mail::Message::Head->log( [$level, [$strings]] )
Inherited, see "Error handling" in Mail::Reporter
$obj->logPriority($level)
Mail::Message::Head->logPriority($level)
Inherited, see "Error handling" in Mail::Reporter
$obj->logSettings()
Inherited, see "Error handling" in Mail::Reporter
$obj->notImplemented()
Inherited, see "Error handling" in Mail::Reporter
$obj->report( [$level] )
Inherited, see "Error handling" in Mail::Reporter
$obj->reportAll( [$level] )
Inherited, see "Error handling" in Mail::Reporter
$obj->trace( [$level] )
Inherited, see "Error handling" in Mail::Reporter
$obj->warnings()
Inherited, see "Error handling" in Mail::Reporter
Cleanup
Extends "Cleanup" in Mail::Reporter.
$obj->DESTROY()
Inherited, see "Cleanup" in Mail::Reporter
DETAILS
Ordered header fields
Many Perl implementations make a big mistake by disturbing the order of header fields.
For some fields (especially the resent groups, see Mail::Message::Head::ResentGroup) the
order shall be maintained.
MailBox will keep the order of the fields as they were found in the source. When your add
a new field, it will be added at the end. If your replace a field with a new value, it
will stay in the original order.
Head class implementation
The header of a MIME message object contains a set of lines, which are called fields (by
default represented by Mail::Message::Field objects). Dependent on the situation, the
knowledge about the fields can be in one of three situations, each represented by a sub-
class of this module:
• Mail::Message::Head::Complete
In this case, it is sure that all knowledge about the header is available. When you
get() information from the header and it is not there, it will never be there.
• Mail::Message::Head::Subset
There is no certainty whether all header lines are known (probably not). This may be
caused as result of reading a fast index file, as described in Mail::Box::MH::Index.
The object is automatically transformed into a Mail::Message::Head::Complete when all
header lines must be known.
• Mail::Message::Head::Partial
A partial header is like a subset header: probably the header is incomplete. The
means that you are not sure whether a get() for a field fails because the field is not
a part of the message or that it fails because it is not yet known to the program.
Where the subset header knows where to get the other fields, the partial header does
not know it. It cannot hide its imperfection.
• Mail::Message::Head::Delayed
In this case, there is no single field known. Access to this header will always
trigger the loading of the full header.
Subsets of header fields
Message headers can be quite large, and therefore MailBox provides simplified access to
some subsets of information. You can grab these sets of fields together, create and
delete them as group.
On the moment, the following sets are defined:
• Mail::Message::Head::ResentGroup
A resent group is a set of fields which is used to log one step in the transmission of
the message from the original sender to the destination.
Each step adds a set of headers to indicate when the message was received and how it
was forwarded (without modification). These fields are best created using
Mail::Message::bounce().
• Mail::Message::Head::ListGroup
Fields which are used to administer and log mailing list activity. Mailing list
software has to play trics with the original message to be able to get the reply on
that message back to the mailing list. Usually a large number of lines are added.
• Mail::Message::Head::SpamGroup
A set of fields which contains header fields which are produced by spam detection
software. You may want to remove these fields when you store a message for a longer
period of time.
DIAGNOSTICS
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-Message distribution version 3.012, built on February 11,
2022. Website: http://perl.overmeer.net/CPAN/
LICENSE
Copyrights 2001-2022 by [Mark Overmeer <markov@cpan.org>]. 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://dev.perl.org/licenses/