MIME::WordDecoder (3)

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NAME

MIME::WordDecoder - decode RFC 2047 encoded words to a local representation

WARNING: Most of this module is deprecated and may disappear. The only function you should use for MIME decoding is "mime_to_perl_string".

SYNOPSIS

See MIME::Words for the basics of encoded words. See `` for how this class works.

    use MIME::WordDecoder;

    ### Get the default word-decoder (used by unmime()):
    $wd = default MIME::WordDecoder;

    ### Get a word-decoder which maps to ISO-8859-1 (Latin1):
    $wd = supported MIME::WordDecoder "ISO-8859-1";

    ### Decode a MIME string (e.g., into Latin1) via the default decoder:
    $str = $wd->decode('To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld>');

    ### Decode a string using the default decoder, non-OO style:
    $str = unmime('To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld>');

    ### Decode a string to an internal Perl string, non-OO style
    ### The result is likely to have the UTF8 flag ON.
    $str = mime_to_perl_string('To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld>');

DESCRIPTION

Most of this module is deprecated and may disappear. It duplicates (badly) the function of the standard 'Encode' module. The only function you should rely on is mime_to_perl_string.

A MIME::WordDecoder consists, fundamentally, of a hash which maps a character set name (US-ASCII,

etc.) to a subroutine which knows how to take bytes in that character set and turn them into the target string representation. Ideally, this target representation would be Unicode, but we don't want to overspecify the translation that takes place: if you want to convert strings directly to Big5, that's your own decision.

The subroutine will be invoked with two arguments:

(the data in the given character set), and (the upcased character set name).

For example:

    ### Keep 7-bit characters as-is, convert 8-bit characters to '#':
    sub keep7bit {
        local $_ = shift;
        tr/\x00-\x7F/#/c;
        $_;
    }

Here's a decoder which uses that:

   ### Construct a decoder:
   $wd = MIME::WordDecoder->new({'US-ASCII'   => "KEEP",   ### sub { $_[0] }
                                 'ISO-8859-1' => \&keep7bit,
                                 'ISO-8859-2' => \&keep7bit,
                                 'Big5'       => "WARN",
                                 '*'          => "DIE"});

   ### Convert some MIME text to a pure ASCII string...
   $ascii = $wd->decode('To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld>');

   ### ...which will now hold: "To: Keld J#rn Simonsen <keld>"

The

built-in decoder decodes everything into Perl's internal string format, possibly turning on the internal flag. Use it like this:

    $wd = supported MIME::WordDecoder 'UTF-8';
    $perl_string = $wd->decode('To: =?ISO-8859-1?Q?Keld_J=F8rn_Simonsen?= <keld>');
    # perl_string will be a valid UTF-8 string with the "UTF8" flag set.

Generally, you should use the

decoder in preference to ``unmime''.

PUBLIC INTERFACE

default [

DECODER

]

Class method. Get/set the default

DECODER

object.

supported

CHARSET,

[

DECODER

]

Class method. If just

CHARSET

is given, returns a decoder object which maps data into that character set (the character set is forced to all-uppercase).

    $wd = supported MIME::WordDecoder "ISO-8859-1";

If

DECODER

is given, installs such an object:

    MIME::WordDecoder->supported("ISO-8859-1" =>
                                 (new MIME::WordDecoder::ISO_8859 "1"));

You should not override this method.

new [\@HANDLERS]

Class method, constructor. If \@HANDLERS is given, then @HANDLERS is passed to handler() to initialize the internal map.

handler CHARSET=>\&SUBREF, ...

Instance method. Set the handler

SUBREF

for a given

CHARSET,

for as many pairs as you care to supply.

When performing the translation of a MIME-encoded string, a given

SUBREF

will be invoked when translating a block of text in character set

CHARSET.

The subroutine will be invoked with the following arguments:

    DATA    - the data in the given character set.
    CHARSET - the upcased character set name, which may prove useful
              if you are using the same SUBREF for multiple CHARSETs.
    DECODER - the decoder itself, if it contains configuration information
              that your handler function needs.

For example:

    $wd = new MIME::WordDecoder;
    $wd->handler('US-ASCII'   => "KEEP");
    $wd->handler('ISO-8859-1' => \&handle_latin1,
                 'ISO-8859-2' => \&handle_latin1,
                 '*'          => "DIE");

Notice that, much as with %SIG, the

SUBREF

can also be taken from a set of special keywords:

   KEEP     Pass data through unchanged.
   IGNORE   Ignore data in this character set, without warning.
   WARN     Ignore data in this character set, with warning.
   DIE      Fatal exception with "can't handle character set" message.

The subroutine for the special

CHARSET

of 'raw' is used for raw (non-MIME-encoded) text, which is supposed to be US-ASCII. The handler for 'raw' defaults to whatever was specified for '

US-ASCII

' at the time of construction.

The subroutine for the special

CHARSET

of '*' is used for any unrecognized character set. The default action for '*' is

WARN.

decode

STRING

Instance method. Decode a

STRING

which might contain MIME-encoded components into a local representation (e.g.,

UTF-8,

etc.).

unmime

STRING

Function, exported. Decode the given

STRING

using the default() decoder. See default().

You should consider using the

UTF-8

decoder instead. It decodes

MIME

strings into Perl's internal string format.

mime_to_perl_string

Function, exported. Decode the given

STRING

into an internal Perl Unicode string. You should use this function in preference to all others.

The result of mime_to_perl_string is likely to have Perl's

UTF8

flag set.

SUBCLASSES

MIME::WordDecoder::ISO_8859

A simple decoder which keeps US-ASCII and the 7-bit characters of

ISO-8859

character sets and

UTF8,

and also keeps 8-bit characters from the indicated character set.

    ### Construct:
    $wd = new MIME::WordDecoder::ISO_8859 2;    ### ISO-8859-2

    ### What to translate unknown characters to (can also use empty):
    ### Default is "?".
    $wd->unknown("?");

    ### Collapse runs of unknown characters to a single unknown()?
    ### Default is false.
    $wd->collapse(1);

According to czyborra.com/charsets/iso8859.html (ca. November 2000):

ISO 8859

is a full series of 10 (and soon even more) standardized multilingual single-byte coded (8bit) graphic character sets for writing in alphabetic languages:

    1. Latin1 (West European)
    2. Latin2 (East European)
    3. Latin3 (South European)
    4. Latin4 (North European)
    5. Cyrillic
    6. Arabic
    7. Greek
    8. Hebrew
    9. Latin5 (Turkish)
   10. Latin6 (Nordic)

The

ISO 8859

charsets are not even remotely as complete as the truly great Unicode but they have been around and usable for quite a while (first registered Internet charsets for use with

MIME

) and have already offered a major improvement over the plain 7bit US-ASCII.

Characters 0 to 127 are always identical with US-ASCII and the positions 128 to 159 hold some less used control characters: the so-called C1 set from

ISO 6429.

MIME::WordDecoder::US_ASCII

A subclass of the

ISO-8859-1

decoder which discards 8-bit characters. You're probably better off using

ISO-8859-1.

SEE ALSO

MIME::Tools

AUTHOR

Eryq (eryq@zeegee.com), ZeeGee Software Inc (www.zeegee.com). Dianne Skoll (dfs@roaringpenguin.com) www.roaringpenguin.com