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package Encode::MIME::Header;
use strict;
# use warnings;
our $VERSION = do { my @r = (q$Revision: 2.1 $ =~ /\d+/g); sprintf "%d."."%02d" x $#r, @r };
use Encode qw(find_encoding encode_utf8 decode_utf8);
use MIME::Base64;
use Carp;
my %seed =
(
decode_b => '1', # decodes 'B' encoding ?
decode_q => '1', # decodes 'Q' encoding ?
encode => 'B', # encode with 'B' or 'Q' ?
bpl => 75, # bytes per line
);
$Encode::Encoding{'MIME-Header'} =
bless {
%seed,
Name => 'MIME-Header',
} => __PACKAGE__;
$Encode::Encoding{'MIME-B'} =
bless {
%seed,
decode_q => 0,
Name => 'MIME-B',
} => __PACKAGE__;
$Encode::Encoding{'MIME-Q'} =
bless {
%seed,
decode_q => 1,
encode => 'Q',
Name => 'MIME-Q',
} => __PACKAGE__;
use base qw(Encode::Encoding);
sub needs_lines { 1 }
sub perlio_ok{ 0 };
sub decode($$;$){
use utf8;
my ($obj, $str, $chk) = @_;
# zap spaces between encoded words
$str =~ s/\?=\s+=\?/\?==\?/gos;
# multi-line header to single line
$str =~ s/(:?\r|\n|\r\n)[ \t]//gos;
$str =~
s{
=\? # begin encoded word
([0-9A-Za-z\-_]+) # charset (encoding)
\?([QqBb])\? # delimiter
(.*?) # Base64-encodede contents
\?= # end encoded word
}{
if (uc($2) eq 'B'){
$obj->{decode_b} or croak qq(MIME "B" unsupported);
decode_b($1, $3);
}elsif(uc($2) eq 'Q'){
$obj->{decode_q} or croak qq(MIME "Q" unsupported);
decode_q($1, $3);
}else{
croak qq(MIME "$2" encoding is nonexistent!);
}
}egox;
$_[1] = '' if $chk;
return $str;
}
sub decode_b{
my $enc = shift;
my $d = find_encoding($enc) or croak qq(Unknown encoding "$enc");
my $db64 = decode_base64(shift);
return $d->name eq 'utf8' ?
Encode::decode_utf8($db64) : $d->decode($db64, Encode::FB_PERLQQ);
}
sub decode_q{
my ($enc, $q) = @_;
my $d = find_encoding($enc) or croak qq(Unknown encoding "$enc");
$q =~ s/_/ /go;
$q =~ s/=([0-9A-Fa-f]{2})/pack("C", hex($1))/ego;
return $d->name eq 'utf8' ?
Encode::decode_utf8($q) : $d->decode($q, Encode::FB_PERLQQ);
}
my $especials =
join('|' =>
map {quotemeta(chr($_))}
unpack("C*", qq{()<>@,;:\"\'/[]?.=}));
my $re_encoded_word =
qr{
(?:
=\? # begin encoded word
(?:[0-9A-Za-z\-_]+) # charset (encoding)
\?(?:[QqBb])\? # delimiter
(?:.*?) # Base64-encodede contents
\?= # end encoded word
)
}xo;
my $re_especials = qr{$re_encoded_word|$especials}xo;
sub encode($$;$){
my ($obj, $str, $chk) = @_;
my @line = ();
for my $line (split /\r|\n|\r\n/o, $str){
my (@word, @subline);
for my $word (split /($re_especials)/o, $line){
if ($word =~ /[^\x00-\x7f]/o or $word =~ /^$re_encoded_word$/o){
push @word, $obj->_encode($word);
}else{
push @word, $word;
}
}
my $subline = '';
for my $word (@word){
use bytes ();
if (bytes::length($subline) + bytes::length($word) > $obj->{bpl}){
push @subline, $subline;
$subline = '';
}
$subline .= $word;
}
$subline and push @subline, $subline;
push @line, join("\n " => @subline);
}
$_[1] = '' if $chk;
return join("\n", @line);
}
use constant HEAD => '=?UTF-8?';
use constant TAIL => '?=';
use constant SINGLE => { B => \&_encode_b, Q => \&_encode_q, };
sub _encode{
my ($o, $str) = @_;
my $enc = $o->{encode};
my $llen = ($o->{bpl} - length(HEAD) - 2 - length(TAIL));
# to coerce a floating-point arithmetics, the following contains
# .0 in numbers -- dankogai
$llen *= $enc eq 'B' ? 3.0/4.0 : 1.0/3.0;
my @result = ();
my $chunk = '';
while(length(my $chr = substr($str, 0, 1, ''))){
use bytes ();
if (bytes::length($chunk) + bytes::length($chr) > $llen){
push @result, SINGLE->{$enc}($chunk);
$chunk = '';
}
$chunk .= $chr;
}
$chunk and push @result, SINGLE->{$enc}($chunk);
return @result;
}
sub _encode_b{
HEAD . 'B?' . encode_base64(encode_utf8(shift), '') . TAIL;
}
sub _encode_q{
my $chunk = shift;
$chunk =~ s{
([^0-9A-Za-z])
}{
join("" => map {sprintf "=%02X", $_} unpack("C*", $1))
}egox;
return decode_utf8(HEAD . 'Q?' . $chunk . TAIL);
}
1;
__END__
=head1 NAME
Encode::MIME::Header -- MIME 'B' and 'Q' header encoding
=head1 SYNOPSIS
use Encode qw/encode decode/;
$utf8 = decode('MIME-Header', $header);
$header = encode('MIME-Header', $utf8);
=head1 ABSTRACT
This module implements RFC 2047 Mime Header Encoding. There are 3
variant encoding names; C<MIME-Header>, C<MIME-B> and C<MIME-Q>. The
difference is described below
decode() encode()
----------------------------------------------
MIME-Header Both B and Q =?UTF-8?B?....?=
MIME-B B only; Q croaks =?UTF-8?B?....?=
MIME-Q Q only; B croaks =?UTF-8?Q?....?=
=head1 DESCRIPTION
When you decode(=?I<encoding>?I<X>?I<ENCODED WORD>?=), I<ENCODED WORD>
is extracted and decoded for I<X> encoding (B for Base64, Q for
Quoted-Printable). Then the decoded chunk is fed to
decode(I<encoding>). So long as I<encoding> is supported by Encode,
any source encoding is fine.
When you encode, it just encodes UTF-8 string with I<X> encoding then
quoted with =?UTF-8?I<X>?....?= . The parts that RFC 2047 forbids to
encode are left as is and long lines are folded within 76 bytes per
line.
=head1 BUGS
It would be nice to support encoding to non-UTF8, such as =?ISO-2022-JP?
and =?ISO-8859-1?= but that makes the implementation too complicated.
These days major mail agents all support =?UTF-8? so I think it is
just good enough.
Due to popular demand, 'MIME-Header-ISO_2022_JP' was introduced by
Makamaka. Thre are still too many MUAs especially cellular phone
handsets which does not grok UTF-8.
=head1 SEE ALSO
L<Encode>
RFC 2047, L<http://www.faqs.org/rfcs/rfc2047.html> and many other
locations.
=cut
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