X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperluniintro.pod;h=b0d5859065cce8b54cf5d0b2e155bdef6ecdebb2;hb=53273a086103cdbbf7ebdd5f1a18b2c0777cbc1b;hp=870926ea1fcb999842e3e8e8dcf216f554e1dd64;hpb=fae2c0fbfb26247eb616ab310ef74b1f4084ba68;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perluniintro.pod b/pod/perluniintro.pod index 870926e..b0d5859 100644 --- a/pod/perluniintro.pod +++ b/pod/perluniintro.pod @@ -19,6 +19,7 @@ including all commercially-important modern languages. All characters 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 is an abstract entity. It is not bound to any particular integer width, especially not to the C language C. @@ -33,11 +34,10 @@ case 0x0041 and 0x03B1, respectively. These unique numbers are called I. 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. -The Unicode standard uses the notation C, -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. The Unicode standard +uses the notation C, to give the +hexadecimal code point and the normative name of the character. Unicode also defines various I for the characters, like "uppercase" or "lowercase", "decimal digit", or "punctuation"; @@ -86,12 +86,13 @@ characters that do not represent true characters. 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 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, or the I (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 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, or the I (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 @@ -104,13 +105,14 @@ so on. Scripts usually span varied parts of several blocks. For further information see L. The Unicode code points are just abstract numbers. To input and -output these abstract numbers, the numbers must be I somehow. -Unicode defines several I, of which I -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 or +I somehow. Unicode defines several I, of which I 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 and I (BOMs) are--see L. @@ -172,14 +174,15 @@ To output UTF-8, use the C<:utf8> output layer. Prepending to this sample program ensures that the output is completely UTF-8, and removes the program's warning. -If your locale environment variables (C, C, -C, C) contain the strings 'UTF-8' or 'UTF8', -regardless of case, then the default encoding of your STDIN, STDOUT, -and STDERR and of B, is UTF-8. Note that -this means that Perl expects other software to work, too: if Perl has -been led to believe that STDIN should be UTF-8, but then STDIN coming -in from another command is not UTF-8, Perl will complain about the -malformed UTF-8. +You can enable automatic UTF-8-ification of your standard file +handles, default C layer, and C<@ARGV> by using either +the C<-C> command line switch or the C environment +variable, see L for the documentation of the C<-C> switch. + +Note that this means that Perl expects other software to work, too: +if Perl has been led to believe that STDIN should be UTF-8, but then +STDIN coming in from another command is not UTF-8, Perl will complain +about the malformed UTF-8. All features that combine Unicode and I/O also require using the new PerlIO feature. Almost all Perl 5.8 platforms do use PerlIO, though: @@ -243,16 +246,14 @@ Note that both C<\x{...}> and C<\N{...}> are compile-time string constants: you cannot use variables in them. if you want similar run-time functionality, use C and C. -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. - - 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 $chars = pack("U0U*", 0x80, 0xFF); +Likewise, you can stop such UTF-8 interpretation by using the special +C<"C0"> prefix. =head2 Handling Unicode @@ -262,7 +263,7 @@ C will work on the Unicode characters; regular expressions will work on the Unicode characters (see L and L). Note that Perl considers combining character sequences to be -characters, so for example +separate characters, so for example use charnames ':full'; print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n"; @@ -296,8 +297,8 @@ If that variable isn't set, the encoding pragma will fail. The C module knows about many encodings and has interfaces for doing conversions between those encodings: - use Encode 'from_to'; - from_to($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 @@ -361,7 +362,7 @@ the C pragma. See L, or look at the following example. With the C pragma you can use the C<:locale> layer - $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R'; + BEGIN { $ENV{LC_ALL} = $ENV{LANG} = 'ru_RU.KOI8-R' } # the :locale will probe the locale environment variables like LC_ALL use open OUT => ':locale'; # russki parusski open(O, ">koi8"); @@ -398,9 +399,9 @@ written to the stream. For example, the following snippet copies the contents of the file "text.jis" (encoded as ISO-2022-JP, aka JIS) to the file "text.utf8", encoded as UTF-8: - open(my $nihongo, '<:encoding(iso2022-jp)', 'text.jis'); - open(my $unicode, '>:utf8', 'text.utf8'); - while (<$nihongo>) { print $unicode } + open(my $nihongo, '<:encoding(iso-2022-jp)', 'text.jis'); + open(my $unicode, '>:utf8', 'text.utf8'); + while (<$nihongo>) { print $unicode $_ } The naming of encodings, both by the C and by the C pragma, is similar to the C pragma in that it allows for @@ -433,7 +434,8 @@ UTF-8 encoded. A C would have avoided the bug, or explicitly opening also the F for input as UTF-8. B: the C<:utf8> and C<:encoding> features work only if your -Perl has been built with the new PerlIO feature. +Perl has been built with the new PerlIO feature (which is the default +on most systems). =head2 Displaying Unicode As Text @@ -449,17 +451,19 @@ displayed as C<\x..>, and the rest of the characters as themselves: sprintf("\\x{%04X}", $_) : # \x{...} chr($_) =~ /[[:cntrl:]]/ ? # else if control character ... sprintf("\\x%02X", $_) : # \x.. - chr($_) # else as themselves - } unpack("U*", $_[0])); # unpack Unicode characters + quotemeta(chr($_)) # else quoted or as themselves + } unpack("W*", $_[0])); # unpack Unicode characters } For example, nice_string("foo\x{100}bar\n") -returns: +returns the string + + 'foo\x{0100}bar\x0A' - "foo\x{0100}bar\x0A" +which is ready to be printed. =head2 Special Cases @@ -488,19 +492,20 @@ explicitly-defined I/O layers). But if you must, there are two ways of looking behind the scenes. One way of peeking inside the internal encoding of Unicode characters -is to use C to get the bytes or C -to display the bytes: +is to use C to get the bytes of whatever the string +encoding happens to be, or C to get the bytes of the +UTF-8 encoding: # this prints c4 80 for the UTF-8 bytes 0xc4 0x80 - print join(" ", unpack("H*", pack("U", 0x100))), "\n"; + print join(" ", unpack("U0(H2)*", pack("U", 0x100))), "\n"; Yet another way would be to use the Devel::Peek module: perl -MDevel::Peek -e 'Dump(chr(0x100))' -That shows the UTF8 flag in FLAGS and both the UTF-8 bytes +That shows the C flag in FLAGS and both the UTF-8 bytes and Unicode characters in C. See also later in this document -the discussion about the C function of the C module. +the discussion about the C function. =back @@ -621,8 +626,7 @@ didn't get the transparency of Unicode quite right. Okay, if you insist: - use Encode 'is_utf8'; - print is_utf8($string) ? 1 : 0, "\n"; + print utf8::is_utf8($string) ? 1 : 0, "\n"; But note that this doesn't mean that any of the characters in the string are necessary UTF-8 encoded, or that any of the characters have @@ -633,7 +637,7 @@ C<$string>. If the flag is off, the bytes in the scalar are interpreted 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, @@ -642,8 +646,8 @@ as if copies of the byte strings were upgraded to UTF-8: for example, $b = "\x{100}"; print "$a = $b\n"; -the output string will be UTF-8-encoded C, but note -that C<$a> will stay byte-encoded. +the output string will be UTF-8-encoded C, but +C<$a> will stay byte-encoded. Sometimes you might really need to know the byte length of a string instead of the character length. For that use either the @@ -665,22 +669,24 @@ How Do I Detect Data That's Not Valid In a Particular Encoding? Use the C package to try converting it. For example, - use Encode 'encode_utf8'; - if (encode_utf8($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 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 -warning is produced. The "U0" means "expect strictly UTF-8 encoded -Unicode". Without that the C would accept also -data like C), similarly to the C as we saw earlier. +warning is produced. The "C0" means +"process the string character per character". Without that the +C would work in C mode (the default if the format +string starts with C) and it would return the bytes making up the UTF-8 +encoding of the target string, something that will always work. =item * @@ -722,8 +728,8 @@ Back to converting data. If you have (or want) data in your system's 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 is valid UTF-8, but Perl doesn't know it yet, you can make Perl a believer, too: @@ -731,6 +737,10 @@ 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*", $bytes); + You can convert well-formed UTF-8 to a sequence of bytes, but if you just want to convert random binary data into UTF-8, you can't. B. You can @@ -749,7 +759,10 @@ http://www.cl.cam.ac.uk/~mgk25/unicode.html How Does Unicode Work With Traditional Locales? In Perl, not very well. Avoid using locales through the C -pragma. Use only one or the other. +pragma. Use only one or the other. But see L for the +description of the C<-C> switch and its environment counterpart, +C<$ENV{PERL_UNICODE}> to see how to enable various Unicode features, +for example by using locale settings. =back @@ -862,7 +875,7 @@ If you have the GNU recode installed, you can also use the Perl front-end C for character conversions. The following are fast conversions from ISO 8859-1 (Latin-1) bytes -to UTF-8 bytes, the code works even with older Perl 5 versions. +to UTF-8 bytes and back, the code works even with older Perl 5 versions. # ISO 8859-1 to UTF-8 s/([\x80-\xFF])/chr(0xC0|ord($1)>>6).chr(0x80|ord($1)&0x3F)/eg; @@ -873,7 +886,8 @@ to UTF-8 bytes, the code works even with older Perl 5 versions. =head1 SEE ALSO L, L, L, L, L, L, -L, L, L, L +L, L, L, L, +L =head1 ACKNOWLEDGMENTS @@ -883,6 +897,6 @@ mailing lists for their valuable feedback. =head1 AUTHOR, COPYRIGHT, AND LICENSE -Copyright 2001-2002 Jarkko Hietaniemi +Copyright 2001-2002 Jarkko Hietaniemi Ejhi@iki.fiE This document may be distributed under the same terms as Perl itself.