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diff --git a/chromium/third_party/cygwin/lib/perl5/5.10/pods/perluniintro.pod b/chromium/third_party/cygwin/lib/perl5/5.10/pods/perluniintro.pod deleted file mode 100644 index ee61acfb025..00000000000 --- a/chromium/third_party/cygwin/lib/perl5/5.10/pods/perluniintro.pod +++ /dev/null @@ -1,885 +0,0 @@ -=head1 NAME - -perluniintro - Perl Unicode introduction - -=head1 DESCRIPTION - -This document gives a general idea of Unicode and how to use Unicode -in Perl. - -=head2 Unicode - -Unicode is a character set standard which plans to codify all of the -writing systems of the world, plus many other symbols. - -Unicode and ISO/IEC 10646 are coordinated standards that provide code -points for characters in almost all modern character set standards, -covering more than 30 writing systems and hundreds of languages, -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<character> is an abstract entity. It is not bound to any -particular integer width, especially not to the C language C<char>. -Unicode is language-neutral and display-neutral: it does not encode the -language of the text and it does not define fonts or other graphical -layout details. Unicode operates on characters and on text built from -those characters. - -Unicode defines characters like C<LATIN CAPITAL LETTER A> or C<GREEK -SMALL LETTER ALPHA> and unique numbers for the characters, in this -case 0x0041 and 0x03B1, respectively. These unique numbers are called -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. - -Unicode also defines various I<properties> for the characters, like -"uppercase" or "lowercase", "decimal digit", or "punctuation"; -these properties are independent of the names of the characters. -Furthermore, various operations on the characters like uppercasing, -lowercasing, and collating (sorting) are defined. - -A Unicode character consists either of a single code point, or a -I<base character> (like C<LATIN CAPITAL LETTER A>), followed by one or -more I<modifiers> (like C<COMBINING ACUTE ACCENT>). This sequence of -base character and modifiers is called a I<combining character -sequence>. - -Whether to call these combining character sequences "characters" -depends on your point of view. If you are a programmer, you probably -would tend towards seeing each element in the sequences as one unit, -or "character". The whole sequence could be seen as one "character", -however, from the user's point of view, since that's probably what it -looks like in the context of the user's language. - -With this "whole sequence" view of characters, the total number of -characters is open-ended. But in the programmer's "one unit is one -character" point of view, the concept of "characters" is more -deterministic. In this document, we take that second point of view: -one "character" is one Unicode code point, be it a base character or -a combining character. - -For some combinations, there are I<precomposed> characters. -C<LATIN CAPITAL LETTER A WITH ACUTE>, for example, is defined as -a single code point. These precomposed characters are, however, -only available for some combinations, and are mainly -meant to support round-trip conversions between Unicode and legacy -standards (like the ISO 8859). In the general case, the composing -method is more extensible. To support conversion between -different compositions of the characters, various I<normalization -forms> to standardize representations are also defined. - -Because of backward compatibility with legacy encodings, the "a unique -number for every character" idea breaks down a bit: instead, there is -"at least one number for every character". The same character could -be represented differently in several legacy encodings. The -converse is also not true: some code points do not have an assigned -character. Firstly, there are unallocated code points within -otherwise used blocks. Secondly, there are special Unicode control -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<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 -by a language or a set of languages. B<This is also untrue.> -The division into blocks exists, but it is almost completely -accidental--an artifact of how the characters have been and -still are allocated. Instead, there is a concept called I<scripts>, -which is more useful: there is C<Latin> script, C<Greek> script, and -so on. Scripts usually span varied parts of several blocks. -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> 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>. - -=head2 Perl's Unicode Support - -Starting from Perl 5.6.0, Perl has had the capacity to handle Unicode -natively. Perl 5.8.0, however, is the first recommended release for -serious Unicode work. The maintenance release 5.6.1 fixed many of the -problems of the initial Unicode implementation, but for example -regular expressions still do not work with Unicode in 5.6.1. - -B<Starting from Perl 5.8.0, the use of C<use utf8> is no longer -necessary.> In earlier releases the C<utf8> pragma was used to declare -that operations in the current block or file would be Unicode-aware. -This model was found to be wrong, or at least clumsy: the "Unicodeness" -is now carried with the data, instead of being attached to the -operations. Only one case remains where an explicit C<use utf8> is -needed: if your Perl script itself is encoded in UTF-8, you can use -UTF-8 in your identifier names, and in string and regular expression -literals, by saying C<use utf8>. This is not the default because -scripts with legacy 8-bit data in them would break. See L<utf8>. - -=head2 Perl's Unicode Model - -Perl supports both pre-5.6 strings of eight-bit native bytes, and -strings of Unicode characters. The principle is that Perl tries to -keep its data as eight-bit bytes for as long as possible, but as soon -as Unicodeness cannot be avoided, the data is transparently upgraded -to Unicode. - -Internally, Perl currently uses either whatever the native eight-bit -character set of the platform (for example Latin-1) is, defaulting to -UTF-8, to encode Unicode strings. Specifically, if all code points in -the string are C<0xFF> or less, Perl uses the native eight-bit -character set. Otherwise, it uses UTF-8. - -A user of Perl does not normally need to know nor care how Perl -happens to encode its internal strings, but it becomes relevant when -outputting Unicode strings to a stream without a PerlIO layer -- one with -the "default" encoding. In such a case, the raw bytes used internally -(the native character set or UTF-8, as appropriate for each string) -will be used, and a "Wide character" warning will be issued if those -strings contain a character beyond 0x00FF. - -For example, - - perl -e 'print "\x{DF}\n", "\x{0100}\x{DF}\n"' - -produces a fairly useless mixture of native bytes and UTF-8, as well -as a warning: - - Wide character in print at ... - -To output UTF-8, use the C<:encoding> or C<:utf8> output layer. Prepending - - binmode(STDOUT, ":utf8"); - -to this sample program ensures that the output is completely UTF-8, -and removes the program's warning. - -You can enable automatic UTF-8-ification of your standard file -handles, default C<open()> layer, and C<@ARGV> by using either -the C<-C> command line switch or the C<PERL_UNICODE> environment -variable, see L<perlrun> 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: -you can see whether yours is by running "perl -V" and looking for -C<useperlio=define>. - -=head2 Unicode and EBCDIC - -Perl 5.8.0 also supports Unicode on EBCDIC platforms. There, -Unicode support is somewhat more complex to implement since -additional conversions are needed at every step. Some problems -remain, see L<perlebcdic> for details. - -In any case, the Unicode support on EBCDIC platforms is better than -in the 5.6 series, which didn't work much at all for EBCDIC platform. -On EBCDIC platforms, the internal Unicode encoding form is UTF-EBCDIC -instead of UTF-8. The difference is that as UTF-8 is "ASCII-safe" in -that ASCII characters encode to UTF-8 as-is, while UTF-EBCDIC is -"EBCDIC-safe". - -=head2 Creating Unicode - -To create Unicode characters in literals for code points above C<0xFF>, -use the C<\x{...}> notation in double-quoted strings: - - my $smiley = "\x{263a}"; - -Similarly, it can be used in regular expression literals - - $smiley =~ /\x{263a}/; - -At run-time you can use C<chr()>: - - my $hebrew_alef = chr(0x05d0); - -See L</"Further Resources"> for how to find all these numeric codes. - -Naturally, C<ord()> will do the reverse: it turns a character into -a code point. - -Note that C<\x..> (no C<{}> and only two hexadecimal digits), C<\x{...}>, -and C<chr(...)> for arguments less than C<0x100> (decimal 256) -generate an eight-bit character for backward compatibility with older -Perls. For arguments of C<0x100> or more, Unicode characters are -always produced. If you want to force the production of Unicode -characters regardless of the numeric value, use C<pack("U", ...)> -instead of C<\x..>, C<\x{...}>, or C<chr()>. - -You can also use the C<charnames> pragma to invoke characters -by name in double-quoted strings: - - use charnames ':full'; - my $arabic_alef = "\N{ARABIC LETTER ALEF}"; - -And, as mentioned above, you can also C<pack()> numbers into Unicode -characters: - - my $georgian_an = pack("U", 0x10a0); - -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<chr()> and C<charnames::vianame()>. - -If you want to force the result to Unicode characters, use the special -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); - -Likewise, you can stop such UTF-8 interpretation by using the special -C<"C0"> prefix. - -=head2 Handling Unicode - -Handling Unicode is for the most part transparent: just use the -strings as usual. Functions like C<index()>, C<length()>, and -C<substr()> will work on the Unicode characters; regular expressions -will work on the Unicode characters (see L<perlunicode> and L<perlretut>). - -Note that Perl considers combining character sequences to be -separate characters, so for example - - use charnames ':full'; - print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n"; - -will print 2, not 1. The only exception is that regular expressions -have C<\X> for matching a combining character sequence. - -Life is not quite so transparent, however, when working with legacy -encodings, I/O, and certain special cases: - -=head2 Legacy Encodings - -When you combine legacy data and Unicode the legacy data needs -to be upgraded to Unicode. Normally ISO 8859-1 (or EBCDIC, if -applicable) is assumed. - -The C<Encode> module knows about many encodings and has interfaces -for doing conversions between those encodings: - - use Encode 'decode'; - $data = decode("iso-8859-3", $data); # convert from legacy to utf-8 - -=head2 Unicode I/O - -Normally, writing out Unicode data - - print FH $some_string_with_unicode, "\n"; - -produces raw bytes that Perl happens to use to internally encode the -Unicode string. Perl's internal encoding depends on the system as -well as what characters happen to be in the string at the time. If -any of the characters are at code points C<0x100> or above, you will get -a warning. To ensure that the output is explicitly rendered in the -encoding you desire--and to avoid the warning--open the stream with -the desired encoding. Some examples: - - open FH, ">:utf8", "file"; - - open FH, ">:encoding(ucs2)", "file"; - open FH, ">:encoding(UTF-8)", "file"; - open FH, ">:encoding(shift_jis)", "file"; - -and on already open streams, use C<binmode()>: - - binmode(STDOUT, ":utf8"); - - binmode(STDOUT, ":encoding(ucs2)"); - binmode(STDOUT, ":encoding(UTF-8)"); - binmode(STDOUT, ":encoding(shift_jis)"); - -The matching of encoding names is loose: case does not matter, and -many encodings have several aliases. Note that the C<:utf8> layer -must always be specified exactly like that; it is I<not> subject to -the loose matching of encoding names. Also note that C<:utf8> is unsafe for -input, because it accepts the data without validating that it is indeed valid -UTF8. - -See L<PerlIO> for the C<:utf8> layer, L<PerlIO::encoding> and -L<Encode::PerlIO> for the C<:encoding()> layer, and -L<Encode::Supported> for many encodings supported by the C<Encode> -module. - -Reading in a file that you know happens to be encoded in one of the -Unicode or legacy encodings does not magically turn the data into -Unicode in Perl's eyes. To do that, specify the appropriate -layer when opening files - - open(my $fh,'<:encoding(utf8)', 'anything'); - my $line_of_unicode = <$fh>; - - open(my $fh,'<:encoding(Big5)', 'anything'); - my $line_of_unicode = <$fh>; - -The I/O layers can also be specified more flexibly with -the C<open> pragma. See L<open>, or look at the following example. - - use open ':encoding(utf8)'; # input/output default encoding will be UTF-8 - open X, ">file"; - print X chr(0x100), "\n"; - close X; - open Y, "<file"; - printf "%#x\n", ord(<Y>); # this should print 0x100 - close Y; - -With the C<open> pragma you can use the C<:locale> layer - - 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"); - print O chr(0x430); # Unicode CYRILLIC SMALL LETTER A = KOI8-R 0xc1 - close O; - open(I, "<koi8"); - printf "%#x\n", ord(<I>), "\n"; # this should print 0xc1 - close I; - -These methods install a transparent filter on the I/O stream that -converts data from the specified encoding when it is read in from the -stream. The result is always Unicode. - -The L<open> pragma affects all the C<open()> calls after the pragma by -setting default layers. If you want to affect only certain -streams, use explicit layers directly in the C<open()> call. - -You can switch encodings on an already opened stream by using -C<binmode()>; see L<perlfunc/binmode>. - -The C<:locale> does not currently (as of Perl 5.8.0) work with -C<open()> and C<binmode()>, only with the C<open> pragma. The -C<:utf8> and C<:encoding(...)> methods do work with all of C<open()>, -C<binmode()>, and the C<open> pragma. - -Similarly, you may use these I/O layers on output streams to -automatically convert Unicode to the specified encoding when it is -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(iso-2022-jp)', 'text.jis'); - open(my $unicode, '>:utf8', 'text.utf8'); - while (<$nihongo>) { print $unicode $_ } - -The naming of encodings, both by the C<open()> and by the C<open> -pragma allows for flexible names: C<koi8-r> and C<KOI8R> will both be -understood. - -Common encodings recognized by ISO, MIME, IANA, and various other -standardisation organisations are recognised; for a more detailed -list see L<Encode::Supported>. - -C<read()> reads characters and returns the number of characters. -C<seek()> and C<tell()> operate on byte counts, as do C<sysread()> -and C<sysseek()>. - -Notice that because of the default behaviour of not doing any -conversion upon input if there is no default layer, -it is easy to mistakenly write code that keeps on expanding a file -by repeatedly encoding the data: - - # BAD CODE WARNING - open F, "file"; - local $/; ## read in the whole file of 8-bit characters - $t = <F>; - close F; - open F, ">:encoding(utf8)", "file"; - print F $t; ## convert to UTF-8 on output - close F; - -If you run this code twice, the contents of the F<file> will be twice -UTF-8 encoded. A C<use open ':encoding(utf8)'> would have avoided the -bug, or explicitly opening also the F<file> for input as UTF-8. - -B<NOTE>: the C<:utf8> and C<:encoding> features work only if your -Perl has been built with the new PerlIO feature (which is the default -on most systems). - -=head2 Displaying Unicode As Text - -Sometimes you might want to display Perl scalars containing Unicode as -simple ASCII (or EBCDIC) text. The following subroutine converts -its argument so that Unicode characters with code points greater than -255 are displayed as C<\x{...}>, control characters (like C<\n>) are -displayed as C<\x..>, and the rest of the characters as themselves: - - sub nice_string { - join("", - map { $_ > 255 ? # if wide character... - sprintf("\\x{%04X}", $_) : # \x{...} - chr($_) =~ /[[:cntrl:]]/ ? # else if control character ... - sprintf("\\x%02X", $_) : # \x.. - quotemeta(chr($_)) # else quoted or as themselves - } unpack("W*", $_[0])); # unpack Unicode characters - } - -For example, - - nice_string("foo\x{100}bar\n") - -returns the string - - 'foo\x{0100}bar\x0A' - -which is ready to be printed. - -=head2 Special Cases - -=over 4 - -=item * - -Bit Complement Operator ~ And vec() - -The bit complement operator C<~> may produce surprising results if -used on strings containing characters with ordinal values above -255. In such a case, the results are consistent with the internal -encoding of the characters, but not with much else. So don't do -that. Similarly for C<vec()>: you will be operating on the -internally-encoded bit patterns of the Unicode characters, not on -the code point values, which is very probably not what you want. - -=item * - -Peeking At Perl's Internal Encoding - -Normal users of Perl should never care how Perl encodes any particular -Unicode string (because the normal ways to get at the contents of a -string with Unicode--via input and output--should always be via -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<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("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 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. - -=back - -=head2 Advanced Topics - -=over 4 - -=item * - -String Equivalence - -The question of string equivalence turns somewhat complicated -in Unicode: what do you mean by "equal"? - -(Is C<LATIN CAPITAL LETTER A WITH ACUTE> equal to -C<LATIN CAPITAL LETTER A>?) - -The short answer is that by default Perl compares equivalence (C<eq>, -C<ne>) based only on code points of the characters. In the above -case, the answer is no (because 0x00C1 != 0x0041). But sometimes, any -CAPITAL LETTER As should be considered equal, or even As of any case. - -The long answer is that you need to consider character normalization -and casing issues: see L<Unicode::Normalize>, Unicode Technical -Reports #15 and #21, I<Unicode Normalization Forms> and I<Case -Mappings>, http://www.unicode.org/unicode/reports/tr15/ and -http://www.unicode.org/unicode/reports/tr21/ - -As of Perl 5.8.0, the "Full" case-folding of I<Case -Mappings/SpecialCasing> is implemented. - -=item * - -String Collation - -People like to see their strings nicely sorted--or as Unicode -parlance goes, collated. But again, what do you mean by collate? - -(Does C<LATIN CAPITAL LETTER A WITH ACUTE> come before or after -C<LATIN CAPITAL LETTER A WITH GRAVE>?) - -The short answer is that by default, Perl compares strings (C<lt>, -C<le>, C<cmp>, C<ge>, C<gt>) based only on the code points of the -characters. In the above case, the answer is "after", since -C<0x00C1> > C<0x00C0>. - -The long answer is that "it depends", and a good answer cannot be -given without knowing (at the very least) the language context. -See L<Unicode::Collate>, and I<Unicode Collation Algorithm> -http://www.unicode.org/unicode/reports/tr10/ - -=back - -=head2 Miscellaneous - -=over 4 - -=item * - -Character Ranges and Classes - -Character ranges in regular expression character classes (C</[a-z]/>) -and in the C<tr///> (also known as C<y///>) operator are not magically -Unicode-aware. What this means that C<[A-Za-z]> will not magically start -to mean "all alphabetic letters"; not that it does mean that even for -8-bit characters, you should be using C</[[:alpha:]]/> in that case. - -For specifying character classes like that in regular expressions, -you can use the various Unicode properties--C<\pL>, or perhaps -C<\p{Alphabetic}>, in this particular case. You can use Unicode -code points as the end points of character ranges, but there is no -magic associated with specifying a certain range. For further -information--there are dozens of Unicode character classes--see -L<perlunicode>. - -=item * - -String-To-Number Conversions - -Unicode does define several other decimal--and numeric--characters -besides the familiar 0 to 9, such as the Arabic and Indic digits. -Perl does not support string-to-number conversion for digits other -than ASCII 0 to 9 (and ASCII a to f for hexadecimal). - -=back - -=head2 Questions With Answers - -=over 4 - -=item * - -Will My Old Scripts Break? - -Very probably not. Unless you are generating Unicode characters -somehow, old behaviour should be preserved. About the only behaviour -that has changed and which could start generating Unicode is the old -behaviour of C<chr()> where supplying an argument more than 255 -produced a character modulo 255. C<chr(300)>, for example, was equal -to C<chr(45)> or "-" (in ASCII), now it is LATIN CAPITAL LETTER I WITH -BREVE. - -=item * - -How Do I Make My Scripts Work With Unicode? - -Very little work should be needed since nothing changes until you -generate Unicode data. The most important thing is getting input as -Unicode; for that, see the earlier I/O discussion. - -=item * - -How Do I Know Whether My String Is In Unicode? - -You shouldn't care. No, you really shouldn't. No, really. If you -have to care--beyond the cases described above--it means that we -didn't get the transparency of Unicode quite right. - -Okay, if you insist: - - 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 -code points greater than 0xFF (255) or even 0x80 (128), or that the -string has any characters at all. All the C<is_utf8()> does is to -return the value of the internal "utf8ness" flag attached to the -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-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, - - $a = "ab\x80c"; - $b = "\x{100}"; - print "$a = $b\n"; - -the output string will be UTF-8-encoded C<ab\x80c = \x{100}\n>, but -C<$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 -C<Encode::encode_utf8()> function or the C<bytes> pragma and its only -defined function C<length()>: - - my $unicode = chr(0x100); - print length($unicode), "\n"; # will print 1 - require Encode; - print length(Encode::encode_utf8($unicode)), "\n"; # will print 2 - use bytes; - print length($unicode), "\n"; # will also print 2 - # (the 0xC4 0x80 of the UTF-8) - -=item * - -How Do I Detect Data That's Not Valid In a Particular Encoding? - -Use the C<Encode> package to try converting it. -For example, - - use Encode 'decode_utf8'; - eval { decode_utf8($string, Encode::FB_CROAK) }; - if ($@) { - # $string is valid utf8 - } else { - # $string is not valid utf8 - } - -Or use C<unpack> to try decoding it: - - use warnings; - @chars = unpack("C0U*", $string_of_bytes_that_I_think_is_utf8); - -If invalid, a C<Malformed UTF-8 character> warning is produced. The "C0" means -"process the string character per character". Without that, the -C<unpack("U*", ...)> would work in C<U0> mode (the default if the format -string starts with C<U>) and it would return the bytes making up the UTF-8 -encoding of the target string, something that will always work. - -=item * - -How Do I Convert Binary Data Into a Particular Encoding, Or Vice Versa? - -This probably isn't as useful as you might think. -Normally, you shouldn't need to. - -In one sense, what you are asking doesn't make much sense: encodings -are for characters, and binary data are not "characters", so converting -"data" into some encoding isn't meaningful unless you know in what -character set and encoding the binary data is in, in which case it's -not just binary data, now is it? - -If you have a raw sequence of bytes that you know should be -interpreted via a particular encoding, you can use C<Encode>: - - use Encode 'from_to'; - from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8 - -The call to C<from_to()> changes the bytes in C<$data>, but nothing -material about the nature of the string has changed as far as Perl is -concerned. Both before and after the call, the string C<$data> -contains just a bunch of 8-bit bytes. As far as Perl is concerned, -the encoding of the string remains as "system-native 8-bit bytes". - -You might relate this to a fictional 'Translate' module: - - use Translate; - my $phrase = "Yes"; - Translate::from_to($phrase, 'english', 'deutsch'); - ## phrase now contains "Ja" - -The contents of the string changes, but not the nature of the string. -Perl doesn't know any more after the call than before that the -contents of the string indicates the affirmative. - -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("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 -use C<unpack("C*", $string)> for the former, and you can create -well-formed Unicode data by C<pack("U*", 0xff, ...)>. - -=item * - -How Do I Display Unicode? How Do I Input Unicode? - -See http://www.alanwood.net/unicode/ and -http://www.cl.cam.ac.uk/~mgk25/unicode.html - -=item * - -How Does Unicode Work With Traditional Locales? - -In Perl, not very well. Avoid using locales through the C<locale> -pragma. Use only one or the other. But see L<perlrun> for the -description of the C<-C> switch and its environment counterpart, -C<$ENV{PERL_UNICODE}> to see how to enable various Unicode features, -for example by using locale settings. - -=back - -=head2 Hexadecimal Notation - -The Unicode standard prefers using hexadecimal notation because -that more clearly shows the division of Unicode into blocks of 256 characters. -Hexadecimal is also simply shorter than decimal. You can use decimal -notation, too, but learning to use hexadecimal just makes life easier -with the Unicode standard. The C<U+HHHH> notation uses hexadecimal, -for example. - -The C<0x> prefix means a hexadecimal number, the digits are 0-9 I<and> -a-f (or A-F, case doesn't matter). Each hexadecimal digit represents -four bits, or half a byte. C<print 0x..., "\n"> will show a -hexadecimal number in decimal, and C<printf "%x\n", $decimal> will -show a decimal number in hexadecimal. If you have just the -"hex digits" of a hexadecimal number, you can use the C<hex()> function. - - print 0x0009, "\n"; # 9 - print 0x000a, "\n"; # 10 - print 0x000f, "\n"; # 15 - print 0x0010, "\n"; # 16 - print 0x0011, "\n"; # 17 - print 0x0100, "\n"; # 256 - - print 0x0041, "\n"; # 65 - - printf "%x\n", 65; # 41 - printf "%#x\n", 65; # 0x41 - - print hex("41"), "\n"; # 65 - -=head2 Further Resources - -=over 4 - -=item * - -Unicode Consortium - -http://www.unicode.org/ - -=item * - -Unicode FAQ - -http://www.unicode.org/unicode/faq/ - -=item * - -Unicode Glossary - -http://www.unicode.org/glossary/ - -=item * - -Unicode Useful Resources - -http://www.unicode.org/unicode/onlinedat/resources.html - -=item * - -Unicode and Multilingual Support in HTML, Fonts, Web Browsers and Other Applications - -http://www.alanwood.net/unicode/ - -=item * - -UTF-8 and Unicode FAQ for Unix/Linux - -http://www.cl.cam.ac.uk/~mgk25/unicode.html - -=item * - -Legacy Character Sets - -http://www.czyborra.com/ -http://www.eki.ee/letter/ - -=item * - -The Unicode support files live within the Perl installation in the -directory - - $Config{installprivlib}/unicore - -in Perl 5.8.0 or newer, and - - $Config{installprivlib}/unicode - -in the Perl 5.6 series. (The renaming to F<lib/unicore> was done to -avoid naming conflicts with lib/Unicode in case-insensitive filesystems.) -The main Unicode data file is F<UnicodeData.txt> (or F<Unicode.301> in -Perl 5.6.1.) You can find the C<$Config{installprivlib}> by - - perl "-V:installprivlib" - -You can explore various information from the Unicode data files using -the C<Unicode::UCD> module. - -=back - -=head1 UNICODE IN OLDER PERLS - -If you cannot upgrade your Perl to 5.8.0 or later, you can still -do some Unicode processing by using the modules C<Unicode::String>, -C<Unicode::Map8>, and C<Unicode::Map>, available from CPAN. -If you have the GNU recode installed, you can also use the -Perl front-end C<Convert::Recode> for character conversions. - -The following are fast conversions from ISO 8859-1 (Latin-1) bytes -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; - - # UTF-8 to ISO 8859-1 - s/([\xC2\xC3])([\x80-\xBF])/chr(ord($1)<<6&0xC0|ord($2)&0x3F)/eg; - -=head1 SEE ALSO - -L<perlunitut>, L<perlunicode>, L<Encode>, L<open>, L<utf8>, L<bytes>, -L<perlretut>, L<perlrun>, L<Unicode::Collate>, L<Unicode::Normalize>, -L<Unicode::UCD> - -=head1 ACKNOWLEDGMENTS - -Thanks to the kind readers of the perl5-porters@perl.org, -perl-unicode@perl.org, linux-utf8@nl.linux.org, and unicore@unicode.org -mailing lists for their valuable feedback. - -=head1 AUTHOR, COPYRIGHT, AND LICENSE - -Copyright 2001-2002 Jarkko Hietaniemi E<lt>jhi@iki.fiE<gt> - -This document may be distributed under the same terms as Perl itself. |