in the largest Chinese, Japanese, and Korean dictionaries are also
encoded. The standards will eventually cover almost all characters in
more than 250 writing systems and thousands of languages.
+Unicode 1.0 was released in October 1991, and 4.0 in April 2003.
A Unicode I<character> is an abstract entity. It is not bound to any
particular integer width, especially not to the C language C<char>.
I<code points>.
The Unicode standard prefers using hexadecimal notation for the code
-points. If numbers like C<0x0041> are unfamiliar to
-you, take a peek at a later section, L</"Hexadecimal Notation">.
-The Unicode standard uses the notation C<U+0041 LATIN CAPITAL LETTER A>,
-to give the hexadecimal code point and the normative name of
-the character.
+points. If numbers like C<0x0041> are unfamiliar to you, take a peek
+at a later section, L</"Hexadecimal Notation">. The Unicode standard
+uses the notation C<U+0041 LATIN CAPITAL LETTER A>, to give the
+hexadecimal code point and the normative name of the character.
Unicode also defines various I<properties> for the characters, like
"uppercase" or "lowercase", "decimal digit", or "punctuation";
A common myth about Unicode is that it would be "16-bit", that is,
Unicode is only represented as C<0x10000> (or 65536) characters from
-C<0x0000> to C<0xFFFF>. B<This is untrue.> Since Unicode 2.0, Unicode
-has been defined all the way up to 21 bits (C<0x10FFFF>), and since
-Unicode 3.1, characters have been defined beyond C<0xFFFF>. The first
-C<0x10000> characters are called the I<Plane 0>, or the I<Basic
-Multilingual Plane> (BMP). With Unicode 3.1, 17 planes in all are
-defined--but nowhere near full of defined characters, yet.
+C<0x0000> to C<0xFFFF>. B<This is untrue.> Since Unicode 2.0 (July
+1996), Unicode has been defined all the way up to 21 bits (C<0x10FFFF>),
+and since Unicode 3.1 (March 2001), characters have been defined
+beyond C<0xFFFF>. The first C<0x10000> characters are called the
+I<Plane 0>, or the I<Basic Multilingual Plane> (BMP). With Unicode
+3.1, 17 (yes, seventeen) planes in all were defined--but they are
+nowhere near full of defined characters, yet.
Another myth is that the 256-character blocks have something to
do with languages--that each block would define the characters used
For further information see L<Unicode::UCD>.
The Unicode code points are just abstract numbers. To input and
-output these abstract numbers, the numbers must be I<encoded> somehow.
-Unicode defines several I<character encoding forms>, of which I<UTF-8>
-is perhaps the most popular. UTF-8 is a variable length encoding that
-encodes Unicode characters as 1 to 6 bytes (only 4 with the currently
-defined characters). Other encodings include UTF-16 and UTF-32 and their
-big- and little-endian variants (UTF-8 is byte-order independent)
-The ISO/IEC 10646 defines the UCS-2 and UCS-4 encoding forms.
+output these abstract numbers, the numbers must be I<encoded> or
+I<serialised> somehow. Unicode defines several I<character encoding
+forms>, of which I<UTF-8> is perhaps the most popular. UTF-8 is a
+variable length encoding that encodes Unicode characters as 1 to 6
+bytes (only 4 with the currently defined characters). Other encodings
+include UTF-16 and UTF-32 and their big- and little-endian variants
+(UTF-8 is byte-order independent) The ISO/IEC 10646 defines the UCS-2
+and UCS-4 encoding forms.
For more information about encodings--for instance, to learn what
I<surrogates> and I<byte order marks> (BOMs) are--see L<perlunicode>.
constants: you cannot use variables in them. if you want similar
run-time functionality, use C<chr()> and C<charnames::vianame()>.
-Also note that if all the code points for pack "U" are below 0x100,
-bytes will be generated, just like if you were using C<chr()>.
-
- my $bytes = pack("U*", 0x80, 0xFF);
-
If you want to force the result to Unicode characters, use the special
-C<"U0"> prefix. It consumes no arguments but forces the result to be
-in Unicode characters, instead of bytes.
+C<"U0"> prefix. It consumes no arguments but causes the following bytes
+to be interpreted as the UTF-8 encoding of Unicode characters:
+
+ my $chars = pack("U0W*", 0x80, 0x42);
- my $chars = pack("U0U*", 0x80, 0xFF);
+Likewise, you can stop such UTF-8 interpretation by using the special
+C<"C0"> prefix.
=head2 Handling Unicode
will work on the Unicode characters (see L<perlunicode> and L<perlretut>).
Note that Perl considers combining character sequences to be
-characters, so for example
+separate characters, so for example
use charnames ':full';
print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n";
The C<Encode> module knows about many encodings and has interfaces
for doing conversions between those encodings:
- use Encode 'from_to';
- from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8
+ use Encode 'decode';
+ $data = decode("iso-8859-3", $data); # convert from legacy to utf-8
=head2 Unicode I/O
chr($_) =~ /[[:cntrl:]]/ ? # else if control character ...
sprintf("\\x%02X", $_) : # \x..
quotemeta(chr($_)) # else quoted or as themselves
- } unpack("U*", $_[0])); # unpack Unicode characters
+ } unpack("W*", $_[0])); # unpack Unicode characters
}
For example,
ways of looking behind the scenes.
One way of peeking inside the internal encoding of Unicode characters
-is to use C<unpack("C*", ...> to get the bytes or C<unpack("H*", ...)>
-to display the bytes:
+is to use C<unpack("C*", ...> to get the bytes of whatever the string
+encoding happens to be, or C<unpack("U0..", ...)> to get the bytes of the
+UTF-8 encoding:
# this prints c4 80 for the UTF-8 bytes 0xc4 0x80
- print join(" ", unpack("H*", pack("U", 0x100))), "\n";
+ print join(" ", unpack("U0(H2)*", pack("U", 0x100))), "\n";
Yet another way would be to use the Devel::Peek module:
perl -MDevel::Peek -e 'Dump(chr(0x100))'
-That shows the UTF8 flag in FLAGS and both the UTF-8 bytes
+That shows the C<UTF8> flag in FLAGS and both the UTF-8 bytes
and Unicode characters in C<PV>. See also later in this document
the discussion about the C<utf8::is_utf8()> function.
as a single byte encoding. If the flag is on, the bytes in the scalar
are interpreted as the (multi-byte, variable-length) UTF-8 encoded code
points of the characters. Bytes added to an UTF-8 encoded string are
-automatically upgraded to UTF-8. If mixed non-UTF8 and UTF-8 scalars
+automatically upgraded to UTF-8. If mixed non-UTF-8 and UTF-8 scalars
are merged (double-quoted interpolation, explicit concatenation, and
printf/sprintf parameter substitution), the result will be UTF-8 encoded
as if copies of the byte strings were upgraded to UTF-8: for example,
$b = "\x{100}";
print "$a = $b\n";
-the output string will be UTF-8-encoded C<ab\x80c\x{100}\n>, but note
-that C<$a> will stay byte-encoded.
+the output string will be UTF-8-encoded C<ab\x80c = \x{100}\n>, but
+C<$a> will stay byte-encoded.
Sometimes you might really need to know the byte length of a string
instead of the character length. For that use either the
Use the C<Encode> package to try converting it.
For example,
- use Encode 'encode_utf8';
- if (encode_utf8($string_of_bytes_that_I_think_is_utf8)) {
+ use Encode 'decode_utf8';
+ if (decode_utf8($string_of_bytes_that_I_think_is_utf8)) {
# valid
} else {
# invalid
}
-For UTF-8 only, you can use:
+Or use C<unpack> to try decoding it:
use warnings;
- @chars = unpack("U0U*", $string_of_bytes_that_I_think_is_utf8);
+ @chars = unpack("C0U*", $string_of_bytes_that_I_think_is_utf8);
If invalid, a C<Malformed UTF-8 character (byte 0x##) in unpack>
-warning is produced. The "U0" means "expect strictly UTF-8 encoded
-Unicode". Without that the C<unpack("U*", ...)> would accept also
-data like C<chr(0xFF>), similarly to the C<pack> as we saw earlier.
+warning is produced. The "C0" means
+"process the string character per character". Without that the
+C<unpack("U*", ...)> would work in C<U0> mode (the default if the format
+string starts with C<U>) and it would return the bytes making up the UTF-8
+encoding of the target string, something that will always work.
=item *
native 8-bit encoding (e.g. Latin-1, EBCDIC, etc.), you can use
pack/unpack to convert to/from Unicode.
- $native_string = pack("C*", unpack("U*", $Unicode_string));
- $Unicode_string = pack("U*", unpack("C*", $native_string));
+ $native_string = pack("W*", unpack("U*", $Unicode_string));
+ $Unicode_string = pack("U*", unpack("W*", $native_string));
If you have a sequence of bytes you B<know> is valid UTF-8,
but Perl doesn't know it yet, you can make Perl a believer, too:
use Encode 'decode_utf8';
$Unicode = decode_utf8($bytes);
+or:
+
+ $Unicode = pack("U0a*", $bytes);
+
You can convert well-formed UTF-8 to a sequence of bytes, but if
you just want to convert random binary data into UTF-8, you can't.
B<Any random collection of bytes isn't well-formed UTF-8>. You can
How Does Unicode Work With Traditional Locales?
In Perl, not very well. Avoid using locales through the C<locale>
-pragma. Use only one or the other.
+pragma. Use only one or the other. But see L<perlrun> for the
+description of the C<-C> switch and its environment counterpart,
+C<$ENV{PERL_UNICODE}> to see how to enable various Unicode features,
+for example by using locale settings.
=back
=head1 SEE ALSO
L<perlunicode>, L<Encode>, L<encoding>, L<open>, L<utf8>, L<bytes>,
-L<perlretut>, L<Unicode::Collate>, L<Unicode::Normalize>, L<Unicode::UCD>
+L<perlretut>, L<perlrun>, L<Unicode::Collate>, L<Unicode::Normalize>,
+L<Unicode::UCD>
=head1 ACKNOWLEDGMENTS
projects / p5sagit/p5-mst-13.2.git / blobdiff