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.IX Title "Mail::Message::Head::Subset 3"
.TH Mail::Message::Head::Subset 3 2026-04-11 "perl v5.42.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.nh
.SH NAME
Mail::Message::Head::Subset \- subset of header information of a message
.SH INHERITANCE
.IX Header "INHERITANCE"
.Vb 1
\& Mail::Message::Head::Subset realizes a Mail::Message::Head::Complete
\&
\& Mail::Message::Head::Subset
\&   is a Mail::Message::Head
\&   is a Mail::Reporter
.Ve
.SH SYNOPSIS
.IX Header "SYNOPSIS"
.Vb 4
\&  my $subset = Mail::Message::Head::Subset\->new(...)
\&  $subset\->isa(\*(AqMail::Message::Head\*(Aq)  # true
\&  $subset\->guessBodySize               # integer or undef
\&  $subset\->isDelayed                   # true
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
Some types of folders contain an index file which lists a few lines of
information per messages.  Especially when it is costly to read header lines,
the index speeds\-up access considerably.  For instance, the subjects of
all messages are often wanted, but waiting for a thousand messages of the
folder to be read may imply a thousand network reads (IMAP) or file
openings (MH)
.PP
When you access header fields which are not in the header subset, the whole
header has to be parsed (which may consume considerable time, depending on
the type of folder).
.PP
Extends "DESCRIPTION" in Mail::Message::Head.
.SH OVERLOADED
.IX Header "OVERLOADED"
Extends "OVERLOADED" in Mail::Message::Head.
.IP "overload: \fB""""\fR stringifaction" 4
.IX Item "overload: """" stringifaction"
Inherited, see "OVERLOADED" in Mail::Message::Head
.IP "overload: \fBbool\fR true/false" 4
.IX Item "overload: bool true/false"
Inherited, see "OVERLOADED" in Mail::Message::Head
.SH METHODS
.IX Header "METHODS"
Extends "METHODS" in Mail::Message::Head.
.SS Constructors
.IX Subsection "Constructors"
Extends "Constructors" in Mail::Message::Head.
.ie n .IP "$class\->\fBbuild\fR( [PAIR|$field]\-LIST )" 4
.el .IP "\f(CW$class\fR\->\fBbuild\fR( [PAIR|$field]\-LIST )" 4
.IX Item "$class->build( [PAIR|$field]-LIST )"
Inherited, see "Constructors" in Mail::Message::Head
.ie n .IP $class\->\fBnew\fR(%options) 4
.el .IP \f(CW$class\fR\->\fBnew\fR(%options) 4
.IX Item "$class->new(%options)"
Inherited, see "Constructors" in Mail::Message::Head
.SS Attributes
.IX Subsection "Attributes"
Extends "Attributes" in Mail::Message::Head.
.SS "The header"
.IX Subsection "The header"
Extends "The header" in Mail::Message::Head.
.ie n .IP $obj\->\fBisDelayed\fR() 4
.el .IP \f(CW$obj\fR\->\fBisDelayed\fR() 4
.IX Item "$obj->isDelayed()"
Inherited, see "The header" in Mail::Message::Head
.ie n .IP $obj\->\fBisEmpty\fR() 4
.el .IP \f(CW$obj\fR\->\fBisEmpty\fR() 4
.IX Item "$obj->isEmpty()"
Inherited, see "The header" in Mail::Message::Head
.ie n .IP $obj\->\fBisModified\fR() 4
.el .IP \f(CW$obj\fR\->\fBisModified\fR() 4
.IX Item "$obj->isModified()"
Inherited, see "The header" in Mail::Message::Head
.ie n .IP $obj\->\fBknownNames\fR() 4
.el .IP \f(CW$obj\fR\->\fBknownNames\fR() 4
.IX Item "$obj->knownNames()"
Inherited, see "The header" in Mail::Message::Head
.ie n .IP "$obj\->\fBmessage\fR( [$message] )" 4
.el .IP "\f(CW$obj\fR\->\fBmessage\fR( [$message] )" 4
.IX Item "$obj->message( [$message] )"
Inherited, see "The header" in Mail::Message::Head
.ie n .IP "$obj\->\fBmodified\fR( [BOOLEAN] )" 4
.el .IP "\f(CW$obj\fR\->\fBmodified\fR( [BOOLEAN] )" 4
.IX Item "$obj->modified( [BOOLEAN] )"
Inherited, see "The header" in Mail::Message::Head
.ie n .IP $obj\->\fBorderedFields\fR() 4
.el .IP \f(CW$obj\fR\->\fBorderedFields\fR() 4
.IX Item "$obj->orderedFields()"
Inherited, see "The header" in Mail::Message::Head
.SS "Access to the header"
.IX Subsection "Access to the header"
Extends "Access to the header" in Mail::Message::Head.
.ie n .IP $obj\->\fBcount\fR($name) 4
.el .IP \f(CW$obj\fR\->\fBcount\fR($name) 4
.IX Item "$obj->count($name)"
Count the number of fields with this \f(CW$name\fR.  If the \f(CW$name\fR cannot be found,
the full header get loaded.  In case we find any \f(CW$name\fR field, it is
decided we know all of them, and loading is not needed.
.ie n .IP "$obj\->\fBget\fR( $name, [$index] )" 4
.el .IP "\f(CW$obj\fR\->\fBget\fR( \f(CW$name\fR, [$index] )" 4
.IX Item "$obj->get( $name, [$index] )"
Get the data which is related to the field with the \f(CW$name\fR.  The case of the
characters in \f(CW$name\fR does not matter.  When a \f(CW$name\fR is used which is not known
yet, realization will take place.
Improves base, see "Access to the header" in Mail::Message::Head
.ie n .IP "$obj\->\fBstudy\fR( $name, [$index] )" 4
.el .IP "\f(CW$obj\fR\->\fBstudy\fR( \f(CW$name\fR, [$index] )" 4
.IX Item "$obj->study( $name, [$index] )"
Inherited, see "Access to the header" in Mail::Message::Head
.SS "About the body"
.IX Subsection "About the body"
Extends "About the body" in Mail::Message::Head.
.ie n .IP $obj\->\fBguessBodySize\fR() 4
.el .IP \f(CW$obj\fR\->\fBguessBodySize\fR() 4
.IX Item "$obj->guessBodySize()"
The body size is defined in the \f(CW\*(C`Content\-Length\*(C'\fR field.  However, this
field may not be known.  In that case, a guess is made based on the known
\&\f(CW\*(C`Lines\*(C'\fR field.  When also that field is not known yet, \f(CW\*(C`undef\*(C'\fR is returned.
Improves base, see "About the body" in Mail::Message::Head
.ie n .IP $obj\->\fBisMultipart\fR() 4
.el .IP \f(CW$obj\fR\->\fBisMultipart\fR() 4
.IX Item "$obj->isMultipart()"
Inherited, see "About the body" in Mail::Message::Head
.SS Internals
.IX Subsection "Internals"
Extends "Internals" in Mail::Message::Head.
.ie n .IP $obj\->\fBaddNoRealize\fR($field) 4
.el .IP \f(CW$obj\fR\->\fBaddNoRealize\fR($field) 4
.IX Item "$obj->addNoRealize($field)"
Inherited, see "Internals" in Mail::Message::Head
.ie n .IP $obj\->\fBaddOrderedFields\fR($fields) 4
.el .IP \f(CW$obj\fR\->\fBaddOrderedFields\fR($fields) 4
.IX Item "$obj->addOrderedFields($fields)"
Inherited, see "Internals" in Mail::Message::Head
.ie n .IP $obj\->\fBfileLocation\fR() 4
.el .IP \f(CW$obj\fR\->\fBfileLocation\fR() 4
.IX Item "$obj->fileLocation()"
Inherited, see "Internals" in Mail::Message::Head
.ie n .IP $obj\->\fBload\fR() 4
.el .IP \f(CW$obj\fR\->\fBload\fR() 4
.IX Item "$obj->load()"
Inherited, see "Internals" in Mail::Message::Head
.ie n .IP $obj\->\fBmoveLocation\fR($distance) 4
.el .IP \f(CW$obj\fR\->\fBmoveLocation\fR($distance) 4
.IX Item "$obj->moveLocation($distance)"
Inherited, see "Internals" in Mail::Message::Head
.ie n .IP $obj\->\fBread\fR($parser) 4
.el .IP \f(CW$obj\fR\->\fBread\fR($parser) 4
.IX Item "$obj->read($parser)"
Inherited, see "Internals" in Mail::Message::Head
.ie n .IP $obj\->\fBsetNoRealize\fR($field) 4
.el .IP \f(CW$obj\fR\->\fBsetNoRealize\fR($field) 4
.IX Item "$obj->setNoRealize($field)"
Inherited, see "Internals" in Mail::Message::Head
.SS "Error handling"
.IX Subsection "Error handling"
Extends "Error handling" in Mail::Message::Head.
.ie n .IP $obj\->\fBAUTOLOAD\fR() 4
.el .IP \f(CW$obj\fR\->\fBAUTOLOAD\fR() 4
.IX Item "$obj->AUTOLOAD()"
Inherited, see "Error handling" in Mail::Reporter
.ie n .IP $obj\->\fBnotImplemented\fR() 4
.el .IP \f(CW$obj\fR\->\fBnotImplemented\fR() 4
.IX Item "$obj->notImplemented()"
Inherited, see "Error handling" in Mail::Reporter
.SS Cleanup
.IX Subsection "Cleanup"
Extends "Cleanup" in Mail::Message::Head.
.ie n .IP $obj\->\fBDESTROY\fR() 4
.el .IP \f(CW$obj\fR\->\fBDESTROY\fR() 4
.IX Item "$obj->DESTROY()"
Inherited, see "Cleanup" in Mail::Reporter
.SH DETAILS
.IX Header "DETAILS"
Extends "DETAILS" in Mail::Message::Head.
.SH DIAGNOSTICS
.IX Header "DIAGNOSTICS"
.ie n .IP "Error: class $package does not implement method $method." 4
.el .IP "Error: class \f(CW$package\fR does not implement method \f(CW$method\fR." 4
.IX Item "Error: class $package does not implement method $method."
Fatal error: the specific \f(CW$package\fR (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.
Cast by \f(CWnotImplemented()\fR
.SH "SEE ALSO"
.IX Header "SEE ALSO"
This module is part of Mail\-Box version 4.02,
built on April 10, 2026. Website: \fIhttp://perl.overmeer.net/CPAN/\fR
.SH LICENSE
.IX Header "LICENSE"
For contributors see file ChangeLog.
.PP
This software is copyright (c) 2001\-2026 by Mark Overmeer.
.PP
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.