NAME

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

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

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.

METHODS

Constructors

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                             C<'us-ascii'>
 language                            undef        
 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 possiblity 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.

. 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

The attribute

$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.

Attribute encoding

$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 in this attribute. This is needed when components of the same attribute are created separately. Merging is required by the field parsing.

Error handling

This class does not extend Mail::Reporter for obvious performance reasons: there is no logging or tracing available.

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: Too late to merge: value already changed.

REFERENCES

See the MailBox website at http://perl.overmeer.net/mailbox/ for more details.

COPYRIGHTS

Distribution version 2.059. Written by Mark Overmeer (mark@overmeer.net) See the ChangeLog for other contributors.

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