Encode...pported(3perl) Perl Programmers Reference GuideEncode...pported(3perl)
NAME
Encode::Supported -- Encodings supported by Encode
DESCRIPTION
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).
• 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.
• The MIME name as defined in IETF RFCs. This includes all "iso-"s.
• The name in the IANA registry.
• The name used by the organization that defined it.
In case 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.
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 "use Encode::XX" to make them available for most
cases. Encode.pm will automatically load those modules on demand.
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]
----------------------------------------------------------------
null and 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 Encode.
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
Encode::Unicode.
UTF-7 is a special encoding which "re-encodes" UTF-16BE into a 7-bit
encoding. It is implemented separately by Encode::Unicode::UTF7.
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.
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
<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
<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 <http://developer.apple.com/technotes/tn/tn1150.html> for
details.
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. Encode comes with the following KOI charsets.
For gory details, see <http://czyborra.com/charsets/cyrillic.html>
----------------------------------------------------------------
koi8-f
koi8-r cp878 [RFC1489]
koi8-u [RFC2319]
----------------------------------------------------------------
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 Encode::Bytes but because of all those unusual
specifications, Encode 2.20 has relocated the support to
Encode::GSM0338. See Encode::GSM0338 for details.
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.
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.
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>
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 }
----------------------------------------------------------------
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.
Encode::TW -- Taiwan
Standard DOS/Win Macintosh Comment/Reference
----------------------------------------------------------------
big5-eten cp950 MacChineseTrad {big5 aliased to big5-eten}
big5-hkscs
----------------------------------------------------------------
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
----------------------------------------------------------------
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
----------------------------------------------------------------
Miscellaneous encodings
Encode::EBCDIC
See perlebcdic for details.
----------------------------------------------------------------
cp37
cp500
cp875
cp1026
cp1047
posix-bc
----------------------------------------------------------------
Encode::Symbol
For symbols and dingbats.
----------------------------------------------------------------
symbol
dingbats
MacDingbats
AdobeZdingbat
AdobeSymbol
----------------------------------------------------------------
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]
----------------------------------------------------------------
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 suspects. See
Encode::Guess for details.
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.
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).
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.
Audrey Tang may add support for this encoding in her module in future.
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
Cyrillic encoding ISO-IR-111
Anton Tagunov doubts its usefulness.
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 <http://www.unicode.org/>). Contributions welcome.
ISIRI 3342, Iran System, ISIRI 2900 [Farsi]
Ditto.
Thai encoding TCVN
Ditto.
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
<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.uf>
and
<http://lxr.mozilla.org/seamonkey/source/intl/uconv/ucvlatin/vps.ut>
if you are interested in helping us.
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 <http://www.unicode.org/Public/MAPPINGS/VENDORS/APPLE/> .
(Mac) Indic encodings
The maps for the following are available at <http://www.unicode.org/>
but remain unsupported because those encodings need an algorithmical
approach, currently unsupported by enc2xs:
MacDevanagari
MacGurmukhi
MacGujarati
For details, please see "Unicode mapping issues and notes:" at
<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 <http://www.unicode.org/> .
Encoding vs. Charset -- terminology
We are used to using the term (character) encoding and 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 encoding and character set.
To understand that, here is a description of how we make computers grok
our characters.
• First we start with which characters to include. We call this
collection of characters character repertoire.
• Then we have to give each character a unique ID so your computer can
tell the difference between 'a' and 'A'. This itemized character
repertoire is now a character set.
• If your computer can grow the character set without further
processing, you can go ahead and use it. This is called a coded
character set (CCS) or raw character encoding. ASCII is used this way
for most cases.
• But in many cases, especially multi-byte CJK encodings, you have to
tweak a little more. Your network connection may not accept any data
with the Most Significant Bit set, and your computer may not be able
to tell if a given byte is a whole character or just half of it. So
you have to encode the character set to use it.
A character encoding scheme (CES) determines how to encode a given
character set, or a set of multiple character sets. 7bit ISO-2022 is
an example of a CES. You switch between character sets via escape
sequences.
Technically, or mathematically, speaking, a character set encoded in
such a CES that maps character by character may form a CCS. EUC is such
an example. The CES of EUC is as follows:
• Map ASCII unchanged.
• Map such a character set that consists of 94 or 96 powered by N
members by adding 0x80 to each byte.
• You can also use 0x8e and 0x8f to indicate that the following sequence
of characters belongs to yet another character set. To each following
byte is added the value 0x80.
By carefully looking at the encoded byte sequence, you can find that the
byte sequence conforms a unique number. In that sense, EUC is a CCS
generated by a CES above from up to four CCS (complicated?). UTF-8
falls into this category. See "UTF-8" in perlUnicode to find out how
UTF-8 maps Unicode to a byte sequence.
You may also have found out by now why 7bit ISO-2022 cannot comprise a
CCS. If you look at a byte sequence \x21\x21, you can't tell if it is
two !'s or IDEOGRAPHIC SPACE. EUC maps the latter to \xA1\xA1 so you
have no trouble differentiating between "!!". and " ".
Encoding Classification (by Anton Tagunov and Dan Kogai)
This section tries to classify the supported encodings by their
applicability for information exchange over the Internet and to choose
the most suitable aliases to name them in the context of such
communication.
• To (en|de)code encodings marked by "(**)", you need
"Encode::HanExtra", available from CPAN.
Encoding names
US-ASCII UTF-8 ISO-8859-* KOI8-R
Shift_JIS EUC-JP ISO-2022-JP ISO-2022-JP-1
EUC-KR Big5 GB2312
are registered with IANA as preferred MIME names and may be used over
the Internet.
"Shift_JIS" has been officialized by JIS X 0208:1997. "Microsoft-
related naming mess" gives details.
"GB2312" is the IANA name for "EUC-CN". See "Microsoft-related naming
mess" for details.
"GB_2312-80" raw encoding is available as "gb2312-raw" with Encode. See
Encode::CN for details.
EUC-CN
KOI8-U [RFC2319]
have not been registered with IANA (as of March 2002) but seem to be
supported by major web browsers. The IANA name for "EUC-CN" is
"GB2312".
KS_C_5601-1987
is heavily misused. See "Microsoft-related naming mess" for details.
"KS_C_5601-1987" raw encoding is available as "kcs5601-raw" with Encode.
See Encode::KR for details.
UTF-16 UTF-16BE UTF-16LE
are IANA-registered "charset"s. See [RFC 2781] for details. Jungshik
Shin reports that UTF-16 with a BOM is well accepted by MS IE 5/6 and NS
4/6. Beware however that
• "UTF-16" support in any software you're going to be
using/interoperating with has probably been less tested then "UTF-8"
support
• "UTF-8" coded data seamlessly passes traditional command piping
("cat", "more", etc.) while "UTF-16" coded data is likely to cause
confusion (with its zero bytes, for example)
• it is beyond the power of words to describe the way HTML browsers
encode non-"ASCII" form data. To get a general impression, visit
<http://www.alanflavell.org.uk/charset/form-i18n.html>. While
encoding of form data has stabilized for "UTF-8" encoded pages (at
least IE 5/6, NS 6, and Opera 6 behave consistently), be sure to
expect fun (and cross-browser discrepancies) with "UTF-16" encoded
pages!
The rule of thumb is to use "UTF-8" unless you know what you're doing
and unless you really benefit from using "UTF-16".
ISO-IR-165 [RFC1345]
VISCII
GB 12345
GB 18030 (**) (see links below)
EUC-TW (**)
are totally valid encodings but not registered at IANA. The names under
which they are listed here are probably the most widely-known names for
these encodings and are recommended names.
BIG5PLUS (**)
is a proprietary name.
Microsoft-related naming mess
Microsoft products misuse the following names:
KS_C_5601-1987
Microsoft extension to "EUC-KR".
Proper names: "CP949", "UHC", "x-windows-949" (as used by Mozilla).
See
<http://lists.w3.org/Archives/Public/ietf-charsets/2001AprJun/0033.html>
for details.
Encode aliases "KS_C_5601-1987" to "cp949" to reflect this common
misusage. Raw "KS_C_5601-1987" encoding is available as "kcs5601-raw".
See Encode::KR for details.
GB2312
Microsoft extension to "EUC-CN".
Proper names: "CP936", "GBK".
"GB2312" has been registered in the "EUC-CN" meaning at IANA. This has
partially repaired the situation: Microsoft's "GB2312" has become a
superset of the official "GB2312".
Encode aliases "GB2312" to "euc-cn" in full agreement with IANA
registration. "cp936" is supported separately. Raw "GB_2312-80"
encoding is available as "gb2312-raw".
See Encode::CN for details.
Big5
Microsoft extension to "Big5".
Proper name: "CP950".
Encode separately supports "Big5" and "cp950".
Shift_JIS
Microsoft's understanding of "Shift_JIS".
JIS has not endorsed the full Microsoft standard however. The
official "Shift_JIS" includes only JIS X 0201 and JIS X 0208 character
sets, while Microsoft has always used "Shift_JIS" to encode a wider
character repertoire. See "IANA" registration for "Windows-31J".
As a historical predecessor, Microsoft's variant probably has more
rights for the name, though it may be objected that Microsoft
shouldn't have used JIS as part of the name in the first place.
Unambiguous name: "CP932". "IANA" name (also used by Mozilla, and
provided as an alias by Encode): "Windows-31J".
Encode separately supports "Shift_JIS" and "cp932".
Glossary
character repertoire
A collection of unique characters. A character set in the strictest
sense. At this stage, characters are not numbered.
coded character set (CCS)
A character set that is mapped in a way computers can use directly.
Many character encodings, including EUC, fall in this category.
character encoding scheme (CES)
An algorithm to map a character set to a byte sequence. You don't
have to be able to tell which character set a given byte sequence
belongs. 7-bit ISO-2022 is a CES but it cannot be a CCS. EUC is an
example of being both a CCS and CES.
charset (in MIME context)
has long been used in the meaning of "encoding", CES.
While the word combination "character set" has lost this meaning in
MIME context since [RFC 2130], the "charset" abbreviation has retained
it. This is how [RFC 2277] and [RFC 2278] bless "charset":
This document uses the term "charset" to mean a set of rules for
mapping from a sequence of octets to a sequence of characters, such
as the combination of a coded character set and a character encoding
scheme; this is also what is used as an identifier in MIME "charset="
parameters, and registered in the IANA charset registry ... (Note
that this is NOT a term used by other standards bodies, such as ISO).
[RFC 2277]
EUC
Extended Unix Character. See ISO-2022.
ISO-2022
A CES that was carefully designed to coexist with ASCII. There are a
7 bit version and an 8 bit version.
The 7 bit version switches character set via escape sequence so it
cannot form a CCS. Since this is more difficult to handle in programs
than the 8 bit version, the 7 bit version is not very popular except
for iso-2022-jp, the de facto standard CES for e-mails.
The 8 bit version can form a CCS. EUC and ISO-8859 are two examples
thereof. Pre-5.6 perl could use them as string literals.
UCS
Short for Universal Character Set. When you say just UCS, it means
Unicode.
UCS-2
ISO/IEC 10646 encoding form: Universal Character Set coded in two
octets.
Unicode
A character set that aims to include all character repertoires of the
world. Many character sets in various national as well as industrial
standards have become, in a way, just subsets of Unicode.
UTF
Short for Unicode Transformation Format. Determines how to map a
Unicode character into a byte sequence.
UTF-16
A UTF in 16-bit encoding. Can either be in big endian or little
endian. The big endian version is called UTF-16BE (equal to UCS-2 +
surrogate support) and the little endian version is called UTF-16LE.
See Also
Encode, Encode::Byte, Encode::CN, Encode::JP, Encode::KR, Encode::TW,
Encode::EBCDIC, Encode::Symbol Encode::MIME::Header, Encode::Guess
References
ECMA
European Computer Manufacturers Association <http://www.ecma.ch>
ECMA-035 (eq "ISO-2022")
<http://www.ecma.ch/ecma1/STAND/ECMA-035.HTM>
The specification of ISO-2022 is available from the link above.
IANA
Internet Assigned Numbers Authority <http://www.iana.org/>
Assigned Charset Names by IANA
<http://www.iana.org/assignments/character-sets>
Most of the "canonical names" in Encode derive from this list so you
can directly apply the string you have extracted from MIME header of
mails and web pages.
ISO
International Organization for Standardization <http://www.iso.ch/>
RFC
Request For Comments -- need I say more?
<http://www.rfc-editor.org/>, <http://www.ietf.org/rfc.html>,
<http://www.faqs.org/rfcs/>
UC
Unicode Consortium <http://www.unicode.org/>
Unicode Glossary
<http://www.unicode.org/glossary/>
The glossary of this document is based upon this site.
Other Notable Sites
czyborra.com
<http://czyborra.com/>
Contains a lot of useful information, especially gory details of ISO
vs. vendor mappings.
CJK.inf
<http://examples.oreilly.com/cjkvinfo/doc/cjk.inf>
Somewhat obsolete (last update in 1996), but still useful. Also try
<ftp://ftp.oreilly.com/pub/examples/nutshell/cjkv/pdf/GB18030_Summary.pdf>
You will find brief info on "EUC-CN", "GBK" and mostly on "GB 18030".
Jungshik Shin's Hangul FAQ
<http://jshin.net/faq>
And especially its subject 8.
<http://jshin.net/faq/qa8.html>
A comprehensive overview of the Korean ("KS *") standards.
debian.org: "Introduction to i18n"
A brief description for most of the mentioned CJK encodings is
contained in
<http://www.debian.org/doc/manuals/intro-i18n/ch-codes.en.html>
Offline sources
"CJKV Information Processing" by Ken Lunde
CJKV Information Processing 1999 O'Reilly & Associates, ISBN :
1-56592-224-7
The modern successor of "CJK.inf".
Features a comprehensive coverage of CJKV character sets and encodings
along with many other issues faced by anyone trying to better support
CJKV languages/scripts in all the areas of information processing.
To purchase this book, visit
<http://oreilly.com/catalog/9780596514471/> or your favourite
bookstore.
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