Mail::Message::Field::Attribute - one attribute of a full field

Description

       Attributes within MIME fields can be quite complex, and therefore be slow and consumes a lot of memory.
       The Mail::Message::Field::Fast and Mail::Message::Field::Flex simplify them the attributes a lot, which
       may result in erroneous behavior in rare cases.  With the increase of non-western languages on Internet,
       the need for the complex headers becomes more and more in demand.

       A "Mail::Message::Field::Attribute" can be found in any structured Mail::Message::Field::Full header
       field.

       Extends "DESCRIPTION" in Mail::Reporter.

Diagnostics

       Warning: Illegal character in parameter name '$name'
           The specified parameter name contains characters which are not permitted by the RFCs.  You can better
           change  the  name  into  something  which  is accepted, or risk applications to corrupt or ignore the
           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.

       Error: Too late to merge: value already changed.

Inheritance

        Mail::Message::Field::Attribute
          is a Mail::Reporter

License

       Copyrights 2001-2025 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/

perl v5.40.1                                       2025-04-25               Mail::Message::Field::Attribute(3pm)

Methods

       Extends "METHODS" in Mail::Reporter.

   Constructors
       Extends "Constructors" in Mail::Reporter.

       Mail::Message::Field::Attribute->new( <$name, [$value] | STRING>, %options )
           Create a new attribute $name with the optional $value.  If no $value is specified, the first argument
           of this method is inspected for an equals sign '='.  If that character is present,  the  argument  is
           taken  as STRING, containing a preformatted attribute which is processed.  Otherwise, the argument is
           taken as name without $value: set the value later with value().

           Whether encoding takes place depends on the %options and the existence of non-ascii characters in the
           $value.  The $name can only contain ascii characters, hence is never encoded.

           To speed things up, attributes are not derived from the Mail::Reporter base-class.

            -Option           --Defined in     --Default
             charset                             'us-ascii'
             language                            undef
             log                Mail::Reporter   'WARNINGS'
             trace              Mail::Reporter   'WARNINGS'
             use_continuations                   <true>

           charset => STRING
             The $value is translated from utf-8 (Perl internal) to this character set, and the resulting string
             is encoded if required.  "us-ascii" is the normal encoding for e-mail.  Valid character sets can be
             found with Encode::encodings(':all').

           language => STRING
             RFC2231 adds the possibility to specify a language with the field.  When no language is  specified,
             none  is  included  in the encoding.  Valid language names are defined by RFC2130.  This module has
             only limited support for this feature.

           log => LEVEL
           trace => LEVEL
           use_continuations => BOOLEAN
             Continuations are used to break-up long  parameters  into  pieces  which  are  no  longer  than  76
             characters. Encodings are specified in RFC2231, but not supported by some Mail User Agents.

           example:

            my $fn    = Mail::Message::Field::Attribute
                           ->new(filename => 'xyz');

            my $fattr = 'Mail::Message::Field::Attribute';  # abbrev
            my $fn    = $fattr->new
              ( filename => "Re\xC7u"
              , charset  => 'iso-8859-15'
              , language => 'nl-BE'
              );
            print $fn;
              # -->  filename*=iso-8859-15'nl-BE'Re%C7u

   Errorhandling
       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, $callback] )
       Mail::Message::Field::Attribute->defaultTrace( [$level]|[$loglevel, $tracelevel]|[$level, $callback] )
           Inherited, see "Error handling" in Mail::Reporter

       $obj->errors()
           Inherited, see "Error handling" in Mail::Reporter

       $obj->log( [$level, [$strings]] )
       Mail::Message::Field::Attribute->log( [$level, [$strings]] )
           Inherited, see "Error handling" in Mail::Reporter

       $obj->logPriority($level)
       Mail::Message::Field::Attribute->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

   Theattribute
       $obj->addComponent(STRING)
           A  component  is  a  parameter  as  defined by RFC2045, optionally using encoding or continuations as
           defined by RFC2231.  Components of an attribute are found when a field is being parsed.  The RFCs are
           very strict on valid characters, but we cannot be: you have to accept what is coming in if you can.

           example:

            my $param = Mail::Message::Field::Attribute->new;
            $param->addComponent("filename*=iso10646'nl-BE'%Re\47u");

       $obj->charset()
           Returns the character set which is used for this parameter.  If any component is added which contains
           character set information, this is directly available.   Be  warned  that  a  character-set  is  case
           insensitive.

       $obj->language()
           Returns  the  language  which  is  defined  in  the  argument.   If no language is defined "undef" is
           returned, which should be interpreted as "ANY"

       $obj->name()
           Returns the name of this attribute.

       $obj->string()
           Returns the parameter as reference to an array of lines.  When only one line is returned, it  may  be
           short enough to fit on the same line with other components of the header field.

       $obj->value( [STRING] )
           Returns the value of this parameter, optionally after setting it first.

   Attributeencoding
       $obj->decode()
           Translate  all  known  continuations  into  a value.  The produced value is returned and may be utf-8
           encoded or a plain string.

       $obj->encode()

   Internals
       $obj->mergeComponent($attribute)
           Merge the components from  the  specified  attribute  into  this  attribute.   This  is  needed  when
           components of the same attribute are created separately.  Merging is required by the field parsing.

Name

       Mail::Message::Field::Attribute - one attribute of a full field

Overloaded

       overload: comparison
           When  the second argument is a field, then both attribute name (case-sensitive) and the decoded value
           must be the same.  Otherwise, the value is compared.

       overload: stringification
           Returns the decoded content of the attribute.

Synopsis

        my $field    = $msg->head->get('Content-Disposition') or return;
        my $full     = $field->study;   # full understanding in unicode
        my $filename = $full->attribute('filename')           or return;

        print ref $filename;     # this class name
        print $filename;         # the attributes content in utf-8
        print $filename->value;  # same
        print $filename->string; # print string as was found in the file
        $filename->print(\*OUT); # print as was found in the file