supported.pod

视频监控网络部分的协议ddns,的模块的实现代码,请大家大胆指正.

=head1 NAME

Encode::Supported -- Encodings supported by Encode

=head1 DESCRIPTION

=head2 Encoding Names

Encoding names are case insensitive. White space in names
is ignored.  In addition, an encoding may have aliases.
Each encoding has one "canonical" name.  The "canonical"
name is chosen from the names of the encoding by picking
the first in the following sequence (with a few exceptions).

=over 2

=item *

The name used by the Perl community.  That includes 'utf8' and 'ascii'.
Unlike aliases, canonical names directly reach the method so such
frequently used words like 'utf8' don't need to do alias lookups.

=item *

The MIME name as defined in IETF RFCs.  This includes all "iso-"s.

=item * 

The name in the IANA registry.

=item *

The name used by the organization that defined it.

=back

In case I<de jure> canonical names differ from that of the Encode
module, they are always aliased if it ever be implemented.  So you can
safely tell if a given encoding is implemented or not just by passing 
the canonical name.

Because of all the alias issues, and because in the general case 
encodings have state, "Encode" uses an encoding object internally 
once an operation is in progress.

=head1 Supported Encodings

As of Perl 5.8.0, at least the following encodings are recognized.
Note that unless otherwise specified, they are all case insensitive
(via alias) and all occurrence of spaces are replaced with '-'.
In other words, "ISO 8859 1" and "iso-8859-1" are identical.

Encodings are categorized and implemented in several different modules
but you don't have to C<use Encode::XX> to make them available for
most cases.  Encode.pm will automatically load those modules on demand.

=head2 Built-in Encodings

The following encodings are always available.

  Canonical     Aliases                      Comments & References
  ----------------------------------------------------------------
  ascii         US-ascii ISO-646-US                         [ECMA]
  ascii-ctrl			                  Special Encoding
  iso-8859-1    latin1                                       [ISO]
  null				                  Special Encoding
  utf8          UTF-8                                    [RFC2279]
  ----------------------------------------------------------------

I<null> and I<ascii-ctrl> are special.  "null" fails for all character
so when you set fallback mode to PERLQQ, HTMLCREF or XMLCREF, ALL
CHARACTERS will fall back to character references.  Ditto for
"ascii-ctrl" except for control characters.  For fallback modes, see
L<Encode>.

=head2 Encode::Unicode -- other Unicode encodings

Unicode coding schemes other than native utf8 are supported by
Encode::Unicode, which will be autoloaded on demand.

  ----------------------------------------------------------------
  UCS-2BE       UCS-2, iso-10646-1                      [IANA, UC]
  UCS-2LE                                                     [UC]
  UTF-16                                                      [UC]
  UTF-16BE                                                    [UC]
  UTF-16LE                                                    [UC]
  UTF-32                                                      [UC]
  UTF-32BE	UCS-4                                         [UC]
  UTF-32LE                                                    [UC]
  UTF-7                                                  [RFC2152]
  ----------------------------------------------------------------

To find how (UCS-2|UTF-(16|32))(LE|BE)? differ from one another,
see L<Encode::Unicode>. 

UTF-7 is a special encoding which "re-encodes" UTF-16BE into a 7-bit
encoding.  It is implemented seperately by Encode::Unicode::UTF7.

=head2 Encode::Byte -- Extended ASCII

Encode::Byte implements most single-byte encodings except for
Symbols and EBCDIC. The following encodings are based on single-byte
encodings implemented as extended ASCII.  Most of them map
\x80-\xff (upper half) to non-ASCII characters.

=over 2

=item ISO-8859 and corresponding vendor mappings

Since there are so many, they are presented in table format with
languages and corresponding encoding names by vendors.  Note that
the table is sorted in order of ISO-8859 and the corresponding vendor
mappings are slightly different from that of ISO.  See
L<http://czyborra.com/charsets/iso8859.html> for details.

  Lang/Regions  ISO/Other Std.  DOS     Windows Macintosh  Others
  ----------------------------------------------------------------
  N. America    (ASCII)         cp437        AdobeStandardEncoding
                                cp863 (DOSCanadaF)
  W. Europe     iso-8859-1      cp850   cp1252  MacRoman  nextstep
                                                         hp-roman8
                                cp860 (DOSPortuguese)
  Cntrl. Europe iso-8859-2      cp852   cp1250  MacCentralEurRoman
                                                MacCroatian
                                                MacRomanian
                                                MacRumanian
  Latin3[1]     iso-8859-3      
  Latin4[2]     iso-8859-4              
  Cyrillics     iso-8859-5      cp855   cp1251  MacCyrillic
    (See also next section)     cp866           MacUkrainian
  Arabic        iso-8859-6      cp864   cp1256  MacArabic
                                cp1006          MacFarsi
  Greek         iso-8859-7      cp737   cp1253  MacGreek
                                cp869 (DOSGreek2)
  Hebrew        iso-8859-8      cp862   cp1255  MacHebrew
  Turkish       iso-8859-9      cp857   cp1254  MacTurkish
  Nordics       iso-8859-10     cp865
                                cp861           MacIcelandic
                                                MacSami
  Thai          iso-8859-11[3]  cp874           MacThai
  (iso-8859-12 is nonexistent. Reserved for Indics?)
  Baltics       iso-8859-13     cp775           cp1257
  Celtics       iso-8859-14
  Latin9 [4]    iso-8859-15
  Latin10       iso-8859-16
  Vietnamese    viscii                  cp1258  MacVietnamese
  ----------------------------------------------------------------

  [1] Esperanto, Maltese, and Turkish. Turkish is now on 8859-9.
  [2] Baltics.  Now on 8859-10, except for Latvian.
  [3] TIS 620 +  Non-Breaking Space (0xA0 / U+00A0)
  [4] Nicknamed Latin0; the Euro sign as well as French and Finnish
      letters that are missing from 8859-1 were added.

All cp* are also available as ibm-*, ms-*, and windows-* .  See also
L<http://czyborra.com/charsets/codepages.html>.

Macintosh encodings don't seem to be registered in such entities as
IANA.  "Canonical" names in Encode are based upon Apple's Tech Note
1150.  See L<http://developer.apple.com/technotes/tn/tn1150.html> 
for details.

=item KOI8 - De Facto Standard for the Cyrillic world

Though ISO-8859 does have ISO-8859-5, the KOI8 series is far more
popular in the Net.   L<Encode> comes with the following KOI charsets.
For gory details, see L<http://czyborra.com/charsets/cyrillic.html>

  ----------------------------------------------------------------
  koi8-f                                        
  koi8-r cp878                                           [RFC1489]
  koi8-u                                                 [RFC2319]
  ----------------------------------------------------------------

=back

=head2 gsm0338 - Hentai Latin 1

GSM0338 is for GSM handsets. Though it shares alphanumerals with
ASCII, control character ranges and other parts are mapped very
differently, mainly to store Greek characters.  There are also escape
sequences (starting with 0x1B) to cover e.g. the Euro sign.  

This was once handled by L<Encode::Bytes> but because of all those
unusual specifications, Encode 2.20 has relocated the support to
L<Encode::GSM0338>. See L<Encode::GSM0338> for details.

=over 2

=item gsm0338 support before 2.19

Some special cases like a trailing 0x00 byte or a lone 0x1B byte are not
well-defined and decode() will return an empty string for them.
One possible workaround is

   $gsm =~ s/\x00\z/\x00\x00/;
   $uni = decode("gsm0338", $gsm);
   $uni .= "\xA0" if $gsm =~ /\x1B\z/;

Note that the Encode implementation of GSM0338 does not implement the
reuse of Latin capital letters as Greek capital letters (for example,
the 0x5A is U+005A (LATIN CAPITAL LETTER Z), not U+0396 (GREEK CAPITAL
LETTER ZETA).

The GSM0338 is also covered in Encode::Byte even though it is not
an "extended ASCII" encoding.

=back

=head2 CJK: Chinese, Japanese, Korean (Multibyte)

Note that Vietnamese is listed above.  Also read "Encoding vs Charset"
below.  Also note that these are implemented in distinct modules by
countries, due to the size concerns (simplified Chinese is mapped
to 'CN', continental China, while traditional Chinese is mapped to
'TW', Taiwan).  Please refer to their respective documentation pages.

=over 2

=item Encode::CN -- Continental China

  Standard      DOS/Win Macintosh                Comment/Reference
  ----------------------------------------------------------------
  euc-cn [1]            MacChineseSimp
  (gbk)         cp936 [2]
  gb12345-raw                      { GB12345 without CES }
  gb2312-raw                       { GB2312  without CES }
  hz
  iso-ir-165
  ----------------------------------------------------------------

  [1] GB2312 is aliased to this.  See L<Microsoft-related naming mess>
  [2] gbk is aliased to this.  See L<Microsoft-related naming mess>

=item Encode::JP -- Japan

  Standard      DOS/Win Macintosh                Comment/Reference
  ----------------------------------------------------------------
  euc-jp
  shiftjis      cp932   macJapanese
  7bit-jis
  iso-2022-jp                                            [RFC1468]
  iso-2022-jp-1                                          [RFC2237]
  jis0201-raw  { JIS X 0201 (roman + halfwidth kana) without CES }
  jis0208-raw  { JIS X 0208 (Kanji + fullwidth kana) without CES }
  jis0212-raw  { JIS X 0212 (Extended Kanji)         without CES }
  ----------------------------------------------------------------

=item Encode::KR -- Korea

  Standard      DOS/Win Macintosh                Comment/Reference
  ----------------------------------------------------------------
  euc-kr                MacKorean                        [RFC1557]
                cp949 [1]                    
  iso-2022-kr                                            [RFC1557]
  johab                                  [KS X 1001:1998, Annex 3]
  ksc5601-raw                              { KSC5601 without CES }
  ----------------------------------------------------------------

  [1] ks_c_5601-1987, (x-)?windows-949, and uhc are aliased to this.
  See below.

=item Encode::TW -- Taiwan

  Standard      DOS/Win Macintosh                Comment/Reference
  ----------------------------------------------------------------
  big5-eten     cp950   MacChineseTrad {big5 aliased to big5-eten}
  big5-hkscs                              
  ----------------------------------------------------------------

=item Encode::HanExtra -- More Chinese via CPAN

Due to the size concerns, additional Chinese encodings below are
distributed separately on CPAN, under the name Encode::HanExtra.

  Standard      DOS/Win Macintosh                Comment/Reference
  ----------------------------------------------------------------
  big5ext                                   CMEX's Big5e Extension
  big5plus                                  CMEX's Big5+ Extension
  cccii         Chinese Character Code for Information Interchange
  euc-tw                             EUC (Extended Unix Character)
  gb18030                          GBK with Traditional Characters
  ----------------------------------------------------------------

=item Encode::JIS2K -- JIS X 0213 encodings via CPAN

Due to size concerns, additional Japanese encodings below are
distributed separately on CPAN, under the name Encode::JIS2K.

  Standard      DOS/Win Macintosh                Comment/Reference
  ----------------------------------------------------------------
  euc-jisx0213
  shiftjisx0123
  iso-2022-jp-3
  jis0213-1-raw
  jis0213-2-raw
  ----------------------------------------------------------------

=back

=head2 Miscellaneous encodings

=over 2

=item Encode::EBCDIC

See L<perlebcdic> for details.

  ----------------------------------------------------------------
  cp37
  cp500  
  cp875  
  cp1026  
  cp1047  
  posix-bc
  ----------------------------------------------------------------

=item Encode::Symbols

For symbols  and dingbats.

  ----------------------------------------------------------------
  symbol
  dingbats
  MacDingbats
  AdobeZdingbat
  AdobeSymbol
  ----------------------------------------------------------------

=item Encode::MIME::Header

Strictly speaking, MIME header encoding documented in RFC 2047 is more
of encapsulation than encoding.  However, their support in modern
world is imperative so they are supported.

  ----------------------------------------------------------------
  MIME-Header                                            [RFC2047]
  MIME-B                                                 [RFC2047]
  MIME-Q                                                 [RFC2047]
  ----------------------------------------------------------------

=item Encode::Guess

This one is not a name of encoding but a utility that lets you pick up
the most appropriate encoding for a data out of given I<suspects>.  See
L<Encode::Guess> for details.

=back

=head1 Unsupported encodings

The following encodings are not supported as yet; some because they
are rarely used, some because of technical difficulties.  They may
be supported by external modules via CPAN in the future, however.

=over 2

=item   ISO-2022-JP-2 [RFC1554]

Not very popular yet.  Needs Unicode Database or equivalent to
implement encode() (because it includes JIS X 0208/0212, KSC5601, and
GB2312 simultaneously, whose code points in Unicode overlap.  So you
need to lookup the database to determine to what character set a given
Unicode character should belong). 

=item ISO-2022-CN [RFC1922]

Not very popular.  Needs CNS 11643-1 and -2 which are not available in
this module.  CNS 11643 is supported (via euc-tw) in Encode::HanExtra.
Autrijus Tang may add support for this encoding in his module in future.

=item Various HP-UX encodings

The following are unsupported due to the lack of mapping data.

  '8'  - arabic8, greek8, hebrew8, kana8, thai8, and turkish8
  '15' - japanese15, korean15, and roi15

=item Cyrillic encoding ISO-IR-111

Anton Tagunov doubts its usefulness.

=item ISO-8859-8-1 [Hebrew]

None of the Encode team knows Hebrew enough (ISO-8859-8, cp1255 and
MacHebrew are supported because and just because there were mappings
available at L<http://www.unicode.org/>).  Contributions welcome.

=item ISIRI 3342, Iran System, ISIRI 2900 [Farsi]

Ditto.

=item Thai encoding TCVN

Ditto.

=item Vietnamese encodings VPS

Though Jungshik Shin has reported that Mozilla supports this encoding,
it was too late before 5.8.0 for us to add it.  In the future, it
may be available via a separate module.  See
L<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.uf>
and
L<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.ut>
if you are interested in helping us.

=item Various Mac encodings

The following are unsupported due to the lack of mapping data. 

  MacArmenian,  MacBengali,   MacBurmese,   MacEthiopic
  MacExtArabic, MacGeorgian,  MacKannada,   MacKhmer
  MacLaotian,   MacMalayalam, MacMongolian, MacOriya
  MacSinhalese, MacTamil,     MacTelugu,    MacTibetan
  MacVietnamese

The rest which are already available are based upon the vendor mappings
at L<http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/> .

=item (Mac) Indic encodings

The maps for the following are available at L<http://www.unicode.org/>
but remain unsupport because those encodings need algorithmical
approach, currently unsupported by F<enc2xs>:

  MacDevanagari
  MacGurmukhi
  MacGujarati

For details, please see C<Unicode mapping issues and notes:> at
L<http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/DEVANAGA.TXT> .

I believe this issue is prevalent not only for Mac Indics but also in
other Indic encodings, but the above were the only Indic encodings
maps that I could find at L<http://www.unicode.org/> .

=back

=head1 Encoding vs. Charset -- terminology

We are used to using the term (character) I<encoding> and I<character
set> interchangeably.  But just as confusing the terms byte and
character is dangerous and the terms should be differentiated when
needed, we need to differentiate I<encoding> and I<character set>.

To understand that, here is a description of how we make computers
grok our characters.

=over 2

=item *