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.\"
.IX Title "MIME::WordDecoder 3pm"
.TH MIME::WordDecoder 3pm 2024-04-27 "perl v5.38.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
.\" way too many mistakes in technical documents.
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.nh
.SH NAME
MIME::WordDecoder \- decode RFC 2047 encoded words to a local representation
.PP
WARNING: Most of this module is deprecated and may disappear.  The only
function you should use for MIME decoding is "mime_to_perl_string".
.SH SYNOPSIS
.IX Header "SYNOPSIS"
See MIME::Words for the basics of encoded words.
See "DESCRIPTION" for how this class works.
.PP
.Vb 1
\&    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(\*(AqTo: =?ISO\-8859\-1?Q?Keld_J=F8rn_Simonsen?= <keld>\*(Aq);
\&
\&    ### Decode a string using the default decoder, non\-OO style:
\&    $str = unmime(\*(AqTo: =?ISO\-8859\-1?Q?Keld_J=F8rn_Simonsen?= <keld>\*(Aq);
\&
\&    ### 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(\*(AqTo: =?ISO\-8859\-1?Q?Keld_J=F8rn_Simonsen?= <keld>\*(Aq);
.Ve
.SH DESCRIPTION
.IX Header "DESCRIPTION"
WARNING: 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.
.PP
A MIME::WordDecoder consists, fundamentally, of a hash which maps
a character set name (US-ASCII, ISO\-8859\-1, 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 MIME strings directly to Big5,
that's your own decision.
.PP
The subroutine will be invoked with two arguments: DATA (the data in
the given character set), and CHARSET (the upcased character set name).
.PP
For example:
.PP
.Vb 6
\&    ### Keep 7\-bit characters as\-is, convert 8\-bit characters to \*(Aq#\*(Aq:
\&    sub keep7bit {
\&        local $_ = shift;
\&        tr/\ex00\-\ex7F/#/c;
\&        $_;
\&    }
.Ve
.PP
Here's a decoder which uses that:
.PP
.Vb 6
\&   ### Construct a decoder:
\&   $wd = MIME::WordDecoder\->new({\*(AqUS\-ASCII\*(Aq   => "KEEP",   ### sub { $_[0] }
\&                                 \*(AqISO\-8859\-1\*(Aq => \e&keep7bit,
\&                                 \*(AqISO\-8859\-2\*(Aq => \e&keep7bit,
\&                                 \*(AqBig5\*(Aq       => "WARN",
\&                                 \*(Aq*\*(Aq          => "DIE"});
\&
\&   ### Convert some MIME text to a pure ASCII string...
\&   $ascii = $wd\->decode(\*(AqTo: =?ISO\-8859\-1?Q?Keld_J=F8rn_Simonsen?= <keld>\*(Aq);
\&
\&   ### ...which will now hold: "To: Keld J#rn Simonsen <keld>"
.Ve
.PP
The UTF\-8 built-in decoder decodes everything into Perl's internal
string format, possibly turning on the internal UTF8 flag.  Use it like
this:
.PP
.Vb 3
\&    $wd = supported MIME::WordDecoder \*(AqUTF\-8\*(Aq;
\&    $perl_string = $wd\->decode(\*(AqTo: =?ISO\-8859\-1?Q?Keld_J=F8rn_Simonsen?= <keld>\*(Aq);
\&    # perl_string will be a valid UTF\-8 string with the "UTF8" flag set.
.Ve
.PP
Generally, you should use the UTF\-8 decoder in preference to "unmime".
.SH "PUBLIC INTERFACE"
.IX Header "PUBLIC INTERFACE"
.IP "default [DECODER]" 4
.IX Item "default [DECODER]"
\&\fIClass method.\fR
Get/set the default DECODER object.
.IP "supported CHARSET, [DECODER]" 4
.IX Item "supported CHARSET, [DECODER]"
\&\fIClass method.\fR
If just CHARSET is given, returns a decoder object which maps
data into that character set (the character set is forced to
all-uppercase).
.Sp
.Vb 1
\&    $wd = supported MIME::WordDecoder "ISO\-8859\-1";
.Ve
.Sp
If DECODER is given, installs such an object:
.Sp
.Vb 2
\&    MIME::WordDecoder\->supported("ISO\-8859\-1" =>
\&                                 (new MIME::WordDecoder::ISO_8859 "1"));
.Ve
.Sp
You should not override this method.
.IP "new [\e@HANDLERS]" 4
.IX Item "new [@HANDLERS]"
\&\fIClass method, constructor.\fR
If \e@HANDLERS is given, then \f(CW@HANDLERS\fR is passed to \fBhandler()\fR
to initialize the internal map.
.IP "handler CHARSET=>\e&SUBREF, ..." 4
.IX Item "handler CHARSET=>&SUBREF, ..."
\&\fIInstance method.\fR
Set the handler SUBREF for a given CHARSET, for as many pairs
as you care to supply.
.Sp
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:
.Sp
.Vb 5
\&    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.
.Ve
.Sp
For example:
.Sp
.Vb 5
\&    $wd = new MIME::WordDecoder;
\&    $wd\->handler(\*(AqUS\-ASCII\*(Aq   => "KEEP");
\&    $wd\->handler(\*(AqISO\-8859\-1\*(Aq => \e&handle_latin1,
\&                 \*(AqISO\-8859\-2\*(Aq => \e&handle_latin1,
\&                 \*(Aq*\*(Aq          => "DIE");
.Ve
.Sp
Notice that, much as with \f(CW%SIG\fR, the SUBREF can also be taken from
a set of special keywords:
.Sp
.Vb 4
\&   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\*(Aqt handle character set" message.
.Ve
.Sp
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.
.Sp
The subroutine for the special CHARSET of '*' is used for any
unrecognized character set.  The default action for '*' is WARN.
.IP "decode STRING" 4
.IX Item "decode STRING"
\&\fIInstance method.\fR
Decode a STRING which might contain MIME-encoded components into a
local representation (e.g., UTF\-8, etc.).
.IP "unmime STRING" 4
.IX Item "unmime STRING"
\&\fIFunction, exported.\fR
Decode the given STRING using the \fBdefault()\fR decoder.
See \fBdefault()\fR.
.Sp
You should consider using the UTF\-8 decoder instead.  It decodes
MIME strings into Perl's internal string format.
.IP mime_to_perl_string 4
.IX Item "mime_to_perl_string"
\&\fIFunction, exported.\fR
Decode the given STRING into an internal Perl Unicode string.
You should use this function in preference to all others.
.Sp
The result of mime_to_perl_string is likely to have Perl's
UTF8 flag set.
.SH SUBCLASSES
.IX Header "SUBCLASSES"
.IP MIME::WordDecoder::ISO_8859 4
.IX Item "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.
.Sp
.Vb 2
\&    ### 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);
.Ve
.Sp
According to \fBhttp://czyborra.com/charsets/iso8859.html\fR
(ca. November 2000):
.Sp
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:
.Sp
.Vb 10
\&    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)
.Ve
.Sp
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.
.Sp
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.
.IP MIME::WordDecoder::US_ASCII 4
.IX Item "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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
MIME::Tools
.SH AUTHOR
.IX Header "AUTHOR"
Eryq (\fIeryq@zeegee.com\fR), ZeeGee Software Inc (\fIhttp://www.zeegee.com\fR).
Dianne Skoll (dianne@skoll.ca)