--- /dev/null
- $section =~ s/^"\s*(.*?)\s*"$/$1/ if $section;
- if ($page && $page =~ / / && !defined ($section)) {
+ # Pod::ParseLink -- Parse an L<> formatting code in POD text.
+ # $Id: ParseLink.pm,v 1.1 2001/11/15 07:58:57 eagle Exp $
+ #
+ # Copyright 2001 by Russ Allbery <rra@stanford.edu>
+ #
+ # This program is free software; you may redistribute it and/or modify it
+ # under the same terms as Perl itself.
+ #
+ # This module implements parsing of the text of an L<> formatting code as
+ # defined in perlpodspec. It should be suitable for any POD formatter. It
+ # exports only one function, parselink(), which returns the five-item parse
+ # defined in perlpodspec.
+ #
+ # Perl core hackers, please note that this module is also separately
+ # maintained outside of the Perl core as part of the podlators. Please send
+ # me any patches at the address above in addition to sending them to the
+ # standard Perl mailing lists.
+
+ ##############################################################################
+ # Modules and declarations
+ ##############################################################################
+
+ package Pod::ParseLink;
+
+ require 5.004;
+
+ use strict;
+ use vars qw(@EXPORT @ISA $VERSION);
+
+ use Exporter;
+ @ISA = qw(Exporter);
+ @EXPORT = qw(parselink);
+
+ # Don't use the CVS revision as the version, since this module is also in Perl
+ # core and too many things could munge CVS magic revision strings. This
+ # number should ideally be the same as the CVS revision in podlators, however.
+ $VERSION = 1.01;
+
+
+ ##############################################################################
+ # Implementation
+ ##############################################################################
+
+ # Parse the name and section portion of a link into a name and section.
+ sub _parse_section {
+ my ($link) = @_;
+ $link =~ s/^\s+//;
+ $link =~ s/\s+$//;
+
+ # If the whole link is enclosed in quotes, interpret it all as a section
+ # even if it contains a slash.
+ return (undef, $1) if (/^"\s*(.*?)\s*"$/);
+
+ # Split into page and section on slash, and then clean up quoting in the
+ # section. If there is no section and the name contains spaces, also
+ # guess that it's an old section link.
+ my ($page, $section) = split (/\s*\/\s*/, $link, 2);
++ $section =~ s/^"\s*(.*?)\s*"$/$1/;
++ if ($page =~ / / && !defined ($section)) {
+ $section = $page;
+ $page = undef;
+ } else {
+ $page = undef unless $page;
+ $section = undef unless $section;
+ }
+ return ($page, $section);
+ }
+
+ # Infer link text from the page and section.
+ sub _infer_text {
+ my ($page, $section) = @_;
+ my $inferred;
+ if ($page && !$section) {
+ $inferred = $page;
+ } elsif (!$page && $section) {
+ $inferred = '"' . $section . '"';
+ } elsif ($page && $section) {
+ $inferred = '"' . $section . '" in ' . $page;
+ }
+ return $inferred;
+ }
+
+ # Given the contents of an L<> formatting code, parse it into the link text,
+ # the possibly inferred link text, the name or URL, the section, and the type
+ # of link (pod, man, or url).
+ sub parselink {
+ my ($link) = @_;
+ $link =~ s/\s+/ /g;
+ if ($link =~ /\A\w+:[^:\s]\S*\Z/) {
+ return (undef, $link, $link, undef, 'url');
+ } else {
+ my $text;
+ if ($link =~ /\|/) {
+ ($text, $link) = split (/\|/, $link, 2);
+ }
+ my ($name, $section) = _parse_section ($link);
+ my $inferred = $text || _infer_text ($name, $section);
+ my $type = ($name =~ /\(\S*\)/) ? 'man' : 'pod';
+ return ($text, $inferred, $name, $section, $type);
+ }
+ }
+
+
+ ##############################################################################
+ # Module return value and documentation
+ ##############################################################################
+
+ # Ensure we evaluate to true.
+ 1;
+ __END__
+
+ =head1 NAME
+
+ Pod::ParseLink -- Parse an L<> formatting code in POD text
+
+ =head1 SYNOPSIS
+
+ use Pod::ParseLink;
+ my ($text, $inferred, $name, $section, $type) = parselink ($link);
+
+ =head1 DESCRIPTION
+
+ This module only provides a single function, parselink(), which takes the
+ text of an LE<lt>E<gt> formatting code and parses it. It returns the anchor
+ text for the link (if any was given), the anchor text possibly inferred from
+ the name and section, the name or URL, the section if any, and the type of
+ link. The type will be one of 'url', 'pod', or 'man', indicating a URL, a
+ link to a POD page, or a link to a Unix manual page.
+
+ Parsing is implemented per L<perlpodspec>. For backward compatibility,
+ links where there is no section and name contains spaces, or links where the
+ entirety of the link (except for the anchor text if given) is enclosed in
+ double-quotes are interpreted as links to a section (LE<lt>/sectionE<gt>).
+
+ The inferred anchor text is implemented per L<perlpodspec>:
+
+ L<name> => L<name|name>
+ L</section> => L<"section"|/section>
+ L<name/section> => L<"section" in name|name/section>
+
+ The name may contain embedded EE<lt>E<gt> and ZE<lt>E<gt> formatting codes,
+ and the section, anchor text, and inferred anchor text may contain any
+ formatting codes. Any double quotes around the name or section are removed
+ as part of the parsing, as are any leading or trailing whitespace.
+
+ No attempt is made to resolve formatting codes. The caller must be prepared
+ to do that either before or after calling parselink(). (This is because
+ interpretation of EE<lt>E<gt> formatting codes may vary by formatter.)
+
+ =head1 AUTHOR
+
+ Russ Allbery <rra@stanford.edu>.
+
+ =head1 COPYRIGHT AND LICENSE
+
+ Copyright 2001 by Russ Allbery <rra@stanford.edu>.
+
+ This program is free software; you may redistribute it and/or modify it
+ under the same terms as Perl itself.
+
+ =cut
--- /dev/null
-our($VERSION, $ithreads, $othreads);
+ package Thread;
+
++$VERSION = '2.00';
++
+ use strict;
+
- $VERSION = '2.00';
++our $ithreads;
++our $othreads;
+
+ BEGIN {
-our(@ISA, @EXPORT, @EXPORT_OK);
+ use Config;
+ $ithreads = $Config{useithreads};
+ $othreads = $Config{use5005threads};
+ }
+
+ require Exporter;
+ use XSLoader ();
- if ($othreads) {
- require Carp;
- Carp::croak("This Perl has both ithreads and 5005threads (serious malconfiguration)");
- }
++our($VERSION, @ISA, @EXPORT, @EXPORT_OK);
+
+ @ISA = qw(Exporter);
+
+ BEGIN {
+ if ($ithreads) {
+ @EXPORT = qw(share cond_wait cond_broadcast cond_signal unlock)
+ } elsif ($othreads) {
+ @EXPORT_OK = qw(cond_signal cond_broadcast cond_wait);
+ }
+ push @EXPORT_OK, qw(async yield);
+ }
+
+ =head1 NAME
+
+ Thread - manipulate threads in Perl
+
+ =head1 CAVEAT
+
+ Perl has two thread models.
+
+ In Perl 5.005 the thread model was that all data is implicitly shared
+ and shared access to data has to be explicitly synchronized.
+ This model is called "5005threads".
+
+ In Perl 5.6 a new model was introduced in which all is was thread
+ local and shared access to data has to be explicitly declared.
+ This model is called "ithreads", for "interpreter threads".
+
+ In Perl 5.6 the ithreads model was not available as a public API,
+ only as an internal API that was available for extension writers,
+ and to implement fork() emulation on Win32 platforms.
+
+ In Perl 5.8 the ithreads model became available through the C<threads>
+ module.
+
+ Neither model is configured by default into Perl (except, as mentioned
+ above, in Win32 ithreads are always available.) You can see your
+ Perl's threading configuration by running C<perl -V> and looking for
+ the I<use...threads> variables, or inside script by C<use Config;>
+ and testing for C<$Config{use5005threads}> and C<$Config{useithreads}>.
+
+ For old code and interim backwards compatibility, the Thread module
+ has been reworked to function as a frontend for both 5005threads and
+ ithreads.
+
+ Note that the compatibility is not complete: because the data sharing
+ models are directly opposed, anything to do with data sharing has to
+ be thought differently. With the ithreads you must explicitly share()
+ variables between the threads.
+
+ For new code the use of the C<Thread> module is discouraged and
+ the direct use use of the C<threads> and C<threads::shared> modules
+ is encouraged instead.
+
+ Finally, note that there are many known serious problems with the
+ 5005threads, one of the least of which is that regular expression
+ match variables like $1 are not threadsafe, that is, they easily get
+ corrupted by competing threads. Other problems include more insidious
+ data corruption and mysterious crashes. You are seriously urged to
+ use ithreads instead.
+
+ =head1 SYNOPSIS
+
+ use Thread;
+
+ my $t = Thread->new(\&start_sub, @start_args);
+
+ $result = $t->join;
+ $result = $t->eval;
+ $t->detach;
+
+ if ($t->done) {
+ $t->join;
+ }
+
+ if($t->equal($another_thread)) {
+ # ...
+ }
+
+ yield();
+
+ my $tid = Thread->self->tid;
+
+ lock($scalar);
+ lock(@array);
+ lock(%hash);
+
+ lock(\&sub); # not available with ithreads
+
+ $flags = $t->flags; # not available with ithreads
+
+ my @list = Thread->list; # not available with ithreads
+
+ unlock(...); # not available with the 5.005 threads
+
+ use Thread 'async';
+
+ =head1 DESCRIPTION
+
+ The C<Thread> module provides multithreading support for perl.
+
+ =head1 FUNCTIONS
+
+ =over 8
+
+ =item $thread = Thread->new(\&start_sub)
+
+ =item $thread = Thread->new(\&start_sub, LIST)
+
+ C<new> starts a new thread of execution in the referenced subroutine. The
+ optional list is passed as parameters to the subroutine. Execution
+ continues in both the subroutine and the code after the C<new> call.
+
+ C<Thread->new> returns a thread object representing the newly created
+ thread.
+
+ =item lock VARIABLE
+
+ C<lock> places a lock on a variable until the lock goes out of scope
+ (with ithreads you can also explicitly unlock()).
+
+ If the variable is locked by another thread, the C<lock> call will
+ block until it's available. C<lock> is recursive, so multiple calls
+ to C<lock> are safe--the variable will remain locked until the
+ outermost lock on the variable goes out of scope.
+
+ Locks on variables only affect C<lock> calls--they do I<not> affect normal
+ access to a variable. (Locks on subs are different, and covered in a bit.)
+ If you really, I<really> want locks to block access, then go ahead and tie
+ them to something and manage this yourself. This is done on purpose.
+ While managing access to variables is a good thing, Perl doesn't force
+ you out of its living room...
+
+ If a container object, such as a hash or array, is locked, all the
+ elements of that container are not locked. For example, if a thread
+ does a C<lock @a>, any other thread doing a C<lock($a[12])> won't
+ block.
+
+ With 5005threads you may also C<lock> a sub, using C<lock &sub>.
+ Any calls to that sub from another thread will block until the lock
+ is released. This behaviour is not equivalent to declaring the sub
+ with the C<locked> attribute. The C<locked> attribute serializes
+ access to a subroutine, but allows different threads non-simultaneous
+ access. C<lock &sub>, on the other hand, will not allow I<any> other
+ thread access for the duration of the lock.
+
+ Finally, C<lock> will traverse up references exactly I<one> level.
+ C<lock(\$a)> is equivalent to C<lock($a)>, while C<lock(\\$a)> is not.
+
+ =item async BLOCK;
+
+ C<async> creates a thread to execute the block immediately following
+ it. This block is treated as an anonymous sub, and so must have a
+ semi-colon after the closing brace. Like C<Thread->new>, C<async>
+ returns a thread object.
+
+ =item Thread->self
+
+ The C<Thread-E<gt>self> function returns a thread object that represents
+ the thread making the C<Thread-E<gt>self> call.
+
+ =item cond_wait VARIABLE
+
+ The C<cond_wait> function takes a B<locked> variable as
+ a parameter, unlocks the variable, and blocks until another thread
+ does a C<cond_signal> or C<cond_broadcast> for that same locked
+ variable. The variable that C<cond_wait> blocked on is relocked
+ after the C<cond_wait> is satisfied. If there are multiple threads
+ C<cond_wait>ing on the same variable, all but one will reblock waiting
+ to reaquire the lock on the variable. (So if you're only using
+ C<cond_wait> for synchronization, give up the lock as soon as
+ possible.)
+
+ =item cond_signal VARIABLE
+
+ The C<cond_signal> function takes a locked variable as a parameter and
+ unblocks one thread that's C<cond_wait>ing on that variable. If more than
+ one thread is blocked in a C<cond_wait> on that variable, only one (and
+ which one is indeterminate) will be unblocked.
+
+ If there are no threads blocked in a C<cond_wait> on the variable,
+ the signal is discarded.
+
+ =item cond_broadcast VARIABLE
+
+ The C<cond_broadcast> function works similarly to C<cond_signal>.
+ C<cond_broadcast>, though, will unblock B<all> the threads that are
+ blocked in a C<cond_wait> on the locked variable, rather than only
+ one.
+
+ =item yield
+
+ The C<yield> function allows another thread to take control of the
+ CPU. The exact results are implementation-dependent.
+
+ =back
+
+ =head1 METHODS
+
+ =over 8
+
+ =item join
+
+ C<join> waits for a thread to end and returns any values the thread
+ exited with. C<join> will block until the thread has ended, though
+ it won't block if the thread has already terminated.
+
+ If the thread being C<join>ed C<die>d, the error it died with will
+ be returned at this time. If you don't want the thread performing
+ the C<join> to die as well, you should either wrap the C<join> in
+ an C<eval> or use the C<eval> thread method instead of C<join>.
+
+ =item eval
+
+ The C<eval> method wraps an C<eval> around a C<join>, and so waits for
+ a thread to exit, passing along any values the thread might have returned.
+ Errors, of course, get placed into C<$@>. (Not available with ithreads.)
+
+ =item detach
+
+ C<detach> tells a thread that it is never going to be joined i.e.
+ that all traces of its existence can be removed once it stops running.
+ Errors in detached threads will not be visible anywhere - if you want
+ to catch them, you should use $SIG{__DIE__} or something like that.
+
+ =item equal
+
+ C<equal> tests whether two thread objects represent the same thread and
+ returns true if they do.
+
+ =item tid
+
+ The C<tid> method returns the tid of a thread. The tid is
+ a monotonically increasing integer assigned when a thread is
+ created. The main thread of a program will have a tid of zero,
+ while subsequent threads will have tids assigned starting with one.
+
+ =item flags
+
+ The C<flags> method returns the flags for the thread. This is the
+ integer value corresponding to the internal flags for the thread,
+ and the value may not be all that meaningful to you.
+ (Not available with ithreads.)
+
+ =item done
+
+ The C<done> method returns true if the thread you're checking has
+ finished, and false otherwise. (Not available with ithreads.)
+
+ =back
+
+ =head1 LIMITATIONS
+
+ The sequence number used to assign tids is a simple integer, and no
+ checking is done to make sure the tid isn't currently in use. If a
+ program creates more than 2**32 - 1 threads in a single run, threads
+ may be assigned duplicate tids. This limitation may be lifted in
+ a future version of Perl.
+
+ =head1 SEE ALSO
+
+ L<threads::shared> (not available with 5005threads)
+
+ L<attributes>, L<Thread::Queue>, L<Thread::Semaphore>,
+ L<Thread::Specific> (not available with ithreads)
+
+ =cut
+
+ #
+ # Methods
+ #
+
+ #
+ # Exported functions
+ #
+
+ sub async (&) {
+ return Thread->new($_[0]);
+ }
+
+ sub eval {
+ return eval { shift->join; };
+ }
+
+ sub unimplemented {
+ print $_[0], " unimplemented with ",
+ $Config{useithreads} ? "ithreads" : "5005threads", "\n";
+
+ }
+
+ sub unimplement {
+ for my $m (@_) {
+ no strict 'refs';
+ *{"Thread::$m"} = sub { unimplemented $m };
+ }
+ }
+
+ BEGIN {
+ if ($ithreads) {
- Carp::croak("This Perl has neither ithreads nor 5005threads");
+ XSLoader::load 'threads';
+ for my $m (qw(new join detach yield self tid equal)) {
+ no strict 'refs';
+ *{"Thread::$m"} = \&{"threads::$m"};
+ }
+ XSLoader::load 'threads::shared';
+ for my $m (qw(cond_signal cond_broadcast cond_wait unlock share)) {
+ no strict 'refs';
+ *{"Thread::$m"} = \&{"threads::shared::${m}_enabled"};
+ }
+ # trying to unimplement eval gives redefined warning
+ unimplement(qw(list done flags));
+ } elsif ($othreads) {
+ XSLoader::load 'Thread';
+ unimplement(qw(unlock));
+ } else {
+ require Carp;
++ Carp::croak("This Perl has neither ithreads not 5005threads");
+ }
+ }
+
+ 1;
--- /dev/null
- print FH chr(0x100), "\n";
+ =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 with plans to cover 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 the 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.
+
+ A Unicode I<character> is an abstract entity. It is not bound to any
+ particular integer width, and especially not to the C language C<char>.
+ Unicode is language neutral and display neutral: it doesn't encode the
+ language of the text, and it doesn't 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 then unique numbers for those, hexadecimal
+ 0x0041 or 0x03B1 for those particular characters. Such unique
+ numbers are called I<code points>.
+
+ The Unicode standard prefers using hexadecimal notation for the code
+ points. (In case this notation, numbers like 0x0041, is 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>,
+ which gives 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
+ a base character and modifiers is called a I<combining character
+ sequence>.
+
+ Whether to call these combining character sequences, as a whole,
+ "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, one "character", but from the user viewpoint, the sequence as a
+ whole is probably considered one "character", since that's probably what
+ it looks like in the context of the user's language.
+
+ With this "as a whole" view of characters, the 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, and so we take
+ that point of view in this document: one "character" is one Unicode
+ code point, be it a base character or a combining character.
+
+ For some of the combinations there are I<precomposed> characters,
+ for example C<LATIN CAPITAL LETTER A WITH ACUTE> is defined as
+ a single code point. These precomposed characters are, however,
+ often available only for some combinations, and mainly they are
+ meant to support round-trip conversions between Unicode and legacy
+ standards (like the ISO 8859), and in general case the composing
+ method is more extensible. To support conversion between the
+ different compositions of the characters, various I<normalization
+ forms> are also defined.
+
+ Because of backward compatibility with legacy encodings, the "a unique
+ number for every character" breaks down a bit: "at least one number
+ for every character" is closer to truth. (This happens when the same
+ character has been encoded in several legacy encodings.) The converse
+ is also not true: not every code point has 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,
+ 0x10000 (or 65536) characters from 0x0000 to 0xFFFF. B<This is untrue.>
+ Since Unicode 2.0 Unicode has been defined all the way up to 21 bits
+ (0x10FFFF), and since 3.1 characters have been defined beyond 0xFFFF.
+ The first 0x10000 characters are called the I<Plane 0>, or the I<Basic
+ Multilingual Plane> (BMP). With the Unicode 3.1, 17 planes in all are
+ defined (but nowhere near full of defined characters yet).
+
+ Another myth is that the 256-character blocks have something to do
+ with languages: a block per language. B<Also this is untrue.>
+ The division into the blocks exists but it is almost completely
+ accidental, an artifact of how the characters have been historically
+ allocated. Instead, there is a concept called I<scripts>, which may
+ be more useful: there is C<Latin> script, C<Greek> script, and so on.
+ Scripts usually span several 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> 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 are UTF-16 and UTF-32 and their
+ big and little endian variants (UTF-8 is byteorder independent).
+ The ISO/IEC 10646 defines the UCS-2 and UCS-4 encoding forms.
+
+ For more information about encodings, for example 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 capability of handling
+ Unicode natively. The first recommended release for serious Unicode
+ work is Perl 5.8.0, however. The maintenance release 5.6.1 fixed many
+ of the problems of the initial implementation of Unicode, but for
+ example regular expressions didn't really work with Unicode.
+
+ 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, not attached to the operations. (There
+ is one remaining case where an explicit C<use utf8> is needed: if your
+ Perl script is in UTF-8, you can use UTF-8 in your variable and
+ subroutine names, and in your string and regular expression literals,
+ by saying C<use utf8>. This is not the default because that would
+ break existing scripts having legacy 8-bit data in them.)
+
+ =head2 Perl's Unicode Model
+
+ Perl supports both the old, pre-5.6, model of 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.
+
+ The internal encoding of Unicode in Perl is UTF-8. The internal
+ encoding is normally hidden, however, and one need not and should not
+ worry about the internal encoding at all: it is all just characters.
+
+ Perl 5.8.0 will also support Unicode on EBCDIC platforms. There the
+ support is somewhat harder to implement since additional conversions
+ are needed at every step. Because of these difficulties the Unicode
+ support won't be quite as full as in other, mainly ASCII-based,
+ platforms (the Unicode support will be better than in the 5.6 series,
+ which didn't work much at all for EBCDIC platform). On EBCDIC
+ platforms the internal encoding form used is UTF-EBCDIC.
+
+ =head2 Creating Unicode
+
+ To create Unicode literals, use the C<\x{...}> notation in
+ doublequoted strings:
+
+ my $smiley = "\x{263a}";
+
+ Similarly for 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: turn a character to a code point.
+
+ Note that C<\x..>, C<\x{..}> and C<chr(...)> for arguments less than
+ 0x100 (decimal 256) will generate an eight-bit character for backward
+ compatibility with older Perls. For arguments of 0x100 or more,
+ Unicode will always be produced. If you want UTF-8 always, 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 doublequoted 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 $georgian_an = pack("U", 0x10a0);
+
+ =head2 Handling Unicode
+
+ Handling Unicode is for the most part transparent: just use the
+ strings as usual. Functions like C<index()>, C<length()>, and
+ C<substr()> will work on the Unicode characters; regular expressions
+ will work on the Unicode characters (see L<perlunicode> and L<perlretut>).
+
+ Note that Perl does B<not> consider combining character sequences
+ to be characters, such for example
+
+ use charnames ':full';
+ print length("\N{LATIN CAPITAL LETTER A}\N{COMBINING ACUTE ACCENT}"), "\n";
+
+ will print 2, not 1. The only exception is that regular expressions
+ have C<\X> for matching a combining character sequence.
+
+ When life is not quite so transparent is working with legacy
+ encodings, and I/O, and certain special cases.
+
+ =head2 Legacy Encodings
+
+ When you combine legacy data and Unicode the legacy data needs
+ to be upgraded to Unicode. Normally ISO 8859-1 (or EBCDIC, if
+ applicable) is assumed. You can override this assumption by
+ using the C<encoding> pragma, for example
+
+ use encoding 'latin2'; # ISO 8859-2
+
+ in which case literals (string or regular expression) and chr/ord
+ in your whole script are assumed to produce Unicode characters from
+ ISO 8859-2 code points. Note that the matching for the encoding
+ names is forgiving: instead of C<latin2> you could have said
+ C<Latin 2>, or C<iso8859-2>, and so forth. With just
+
+ use encoding;
+
+ first the environment variable C<PERL_ENCODING> will be consulted,
+ and if that doesn't exist, ISO 8859-1 (Latin 1) will be assumed.
+
+ The C<Encode> module knows about many encodings and it has interfaces
+ for doing conversions between those encodings:
+
+ use Encode 'from_to';
+ from_to($data, "iso-8859-3", "utf-8"); # from legacy to utf-8
+
+ =head2 Unicode I/O
+
+ Normally writing out Unicode data
+
-will print out the raw UTF-8 bytes, but you will get a warning
-out of that if you use C<-w> or C<use warnings>. To avoid the
-warning open the stream explicitly in UTF-8:
++ print chr(0x100), "\n";
+
- open FH, ">:utf8", "file";
-
-and on already open streams use C<binmode()>:
-
- binmode(STDOUT, ":utf8");
-
-Reading in correctly formed UTF-8 data will not magically turn
++will print out the raw UTF-8 bytes.
+
- use open ':utf8'; # input and output default discipline will be UTF-8
- open X, ">file";
- print X chr(0x100), "\n";
++But reading in correctly formed UTF-8 data will not magically turn
+ the data into Unicode in Perl's eyes.
+
+ You can use either the C<':utf8'> I/O discipline when opening files
+
+ open(my $fh,'<:utf8', 'anything');
+ my $line_of_utf8 = <$fh>;
+
+ The I/O disciplines can also be specified more flexibly with
+ the C<open> pragma; see L<open>:
+
- open Y, "<file";
++ use open ':utf8'; # input and output will be UTF-8
++ open X, ">utf8";
++ print X chr(0x100), "\n"; # this would have been UTF-8 without the pragma
+ close X;
-UTF-8 encoded. A C<use open ':utf8'> would have avoided the bug, or
-explicitly opening also the F<file> for input as UTF-8.
++ open Y, "<utf8";
+ printf "%#x\n", ord(<Y>); # this should print 0x100
+ close Y;
+
+ With the C<open> pragma you can use the C<:locale> discipline
+
+ $ENV{LANG} = 'ru_RU.KOI8-R';
+ # the :locale will probe the locale environment variables like LANG
+ 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;
+
+ or you can also use the C<':encoding(...)'> discipline
+
+ open(my $epic,'<:encoding(iso-8859-7)','iliad.greek');
+ my $line_of_iliad = <$epic>;
+
+ Both of these methods install a transparent filter on the I/O stream that
+ will convert data from the specified encoding when it is read in from the
+ stream. In the first example the F<anything> file is assumed to be UTF-8
+ encoded Unicode, in the second example the F<iliad.greek> file is assumed
+ to be ISO-8858-7 encoded Greek, but the lines read in will be in both
+ cases Unicode.
+
+ The L<open> pragma affects all the C<open()> calls after the pragma by
+ setting default disciplines. If you want to affect only certain
+ streams, use explicit disciplines 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 work with C<open()> and
+ C<binmode()>, only with the C<open> pragma. The C<:utf8> and
+ C<:encoding(...)> do work with all of C<open()>, C<binmode()>,
+ and the C<open> pragma.
+
+ Similarly, you may use these I/O disciplines on input streams to
+ automatically convert data from the specified encoding when it is
+ written to the stream.
+
+ open(my $unicode, '<:utf8', 'japanese.uni');
+ open(my $nihongo, '>:encoding(iso2022-jp)', 'japanese.jp');
+ while (<$unicode>) { print $nihongo }
+
+ The naming of encodings, both by the C<open()> and by the C<open>
+ pragma, is similarly understanding as with the C<encoding> pragma:
+ 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>.
+
+ 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 "input is not UTF-8"
+ it is easy to mistakenly write code that keeps on expanding a file
+ by repeatedly encoding it in UTF-8:
+
+ # BAD CODE WARNING
+ open F, "file";
+ local $/; # read in the whole file
+ $t = <F>;
+ close F;
+ open F, ">:utf8", "file";
+ print F $t;
+ close F;
+
+ If you run this code twice, the contents of the F<file> will be twice
++UTF-8 encoded. A C<use open ':utf8'> would have avoided the bug.
+
+ =head2 Special Cases
+
+ =over 4
+
+ =item *
+
+ Bit Complement Operator ~ And vec()
+
+ The bit complement operator C<~> will produce surprising results if
+ used on strings containing Unicode characters. The results are
+ consistent with the internal UTF-8 encoding of the characters, but not
+ with much else. So don't do that. Similarly for vec(): you will be
+ operating on the UTF-8 bit patterns of the Unicode characters, not on
+ the bytes, which is very probably not what you want.
+
+ =item *
+
+ Peeking At UTF-8
+
+ 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:
+
+ # this will print c4 80 for the UTF-8 bytes 0xc4 0x80
+ print join(" ", unpack("H*", pack("U", 0x100))), "\n";
+
+ Yet another way would be to use the Devel::Peek module:
+
+ perl -MDevel::Peek -e 'Dump(chr(0x100))'
+
+ That will show the UTF8 flag in FLAGS and both the UTF-8 bytes
+ and Unicode characters in PV. See also later in this document
+ the discussion about the C<is_utf8> function of the C<Encode> module.
+
+ =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, no (because 0x00C1 != 0x0041). But sometimes any
+ CAPITAL LETTER As being considered equal, or even any As of any case,
+ would be desirable.
+
+ The long answer is that you need to consider character normalization
+ and casing issues: see L<Unicode::Normalize>, and Unicode Technical
+ Reports #15 and #21, I<Unicode Normalization Forms> and I<Case
+ Mappings>, http://www.unicode.org/unicode/reports/tr15/
+ http://www.unicode.org/unicode/reports/tr21/
+
+ As of Perl 5.8.0, the's regular expression case-ignoring matching
+ implements only 1:1 semantics: one character matches one character.
+ In I<Case Mappings> both 1:N and N:1 matches are defined.
+
+ =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, after, since 0x00C1 > 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
+
+ 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-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]]/> for that).
+
+ For specifying things like that in regular expressions you can use the
+ various Unicode properties, C<\pL> in this particular case. You can
+ use Unicode code points as the end points of character ranges, but
+ that means that particular code point range, nothing more. For
+ further information, see L<perlunicode>.
+
+ =item *
+
+ String-To-Number Conversions
+
+ Unicode does define several other decimal (and numeric) characters
+ than just the familiar 0 to 9, such as the Arabic and Indic digits.
+ Perl does not support string-to-number conversion for digits other
+ than the 0 to 9 (and 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, any 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 (for example, C<chr(300)>
+ was equal to C<chr(45)>).
+
+ =item How Do I Make My Scripts Work With Unicode?
+
+ Very little work should be needed since nothing changes until you
+ somehow generate Unicode data. The greatest trick will be getting
+ input as Unicode, and 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. 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:
+
+ use Encode 'is_utf8';
+ print 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
+ $string. If the flag is on, characters added to that string will be
+ automatically upgraded to UTF-8 (and even then only if they really
+ need to be upgraded, that is, if their code point is greater than 0xFF).
+
+ Sometimes you might really need to know the byte length of a string
+ instead of the character length. For that use the C<bytes> pragma
+ and its only defined function C<length()>:
+
+ my $unicode = chr(0x100);
+ print length($unicode), "\n"; # will print 1
+ use bytes;
+ print length($unicode), "\n"; # will print 2 (the 0xC4 0x80 of the UTF-8)
+
+ =item How Do I Detect Invalid UTF-8?
+
+ Either
+
+ use Encode 'encode_utf8';
+ if (encode_utf8($string)) {
+ # valid
+ } else {
+ # invalid
+ }
+
+ or
+
+ use warnings;
+ @chars = unpack("U0U*", "\xFF"); # will warn
+
+ The warning will be C<Malformed UTF-8 character (byte 0xff) in
+ unpack>. The "U0" means "expect strictly UTF-8 encoded Unicode".
+ Without that the C<unpack("U*", ...)> would accept also data like
+ C<chr(0xFF>).
+
+ =item How Do I Convert Data Into UTF-8? Or Vice Versa?
+
+ This probably isn't as useful (or simple) as you might think.
+ Also, normally you shouldn't need to.
+
+ In one sense what you are asking doesn't make much sense: UTF-8 is
+ (intended as an) Unicode encoding, so converting "data" into UTF-8
+ isn't meaningful unless you know in what character set and encoding
+ the binary data is in, and in this case you can use C<Encode>.
+
+ use Encode 'from_to';
+ from_to($data, "iso-8859-1", "utf-8"); # from latin-1 to utf-8
+
+ If you have ASCII (really 7-bit US-ASCII), you already have valid
+ UTF-8, the lowest 128 characters of UTF-8 encoded Unicode and US-ASCII
+ are equivalent.
+
+ If you have Latin-1 (or want Latin-1), you can just use pack/unpack:
+
+ $latin1 = pack("C*", unpack("U*", $utf8));
+ $utf8 = pack("U*", unpack("C*", $latin1));
+
+ (The same works for EBCDIC.)
+
+ 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';
+ $utf8 = decode_utf8($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.
+ 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/UTF-8 data by C<pack("U*", 0xff, ...)>.
+
+ =item How Do I Display Unicode? How Do I Input Unicode?
+
+ See http://www.hclrss.demon.co.uk/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.
+
+ =back
+
+ =head2 Hexadecimal Notation
+
+ The Unicode standard prefers using hexadecimal notation because that
+ shows better 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<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
+ "hexdigits" 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.hclrss.demon.co.uk/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
+
+ $Config{installprivlib}/unicode
+
+ in the Perl 5.6 series. (The renaming to F<lib/unicore> was done to
+ avoid naming conflicts with lib/Unicode in case-insensitive filesystems.)
+ The main Unicode data file is F<Unicode.txt> (or F<Unicode.301> in
+ Perl 5.6.1.) You can find the C<$Config{installprivlib}> by
+
+ perl "-V:installprivlib"
+
+ Note that some of the files have been renamed from the Unicode
+ standard since the Perl installation tries to live by the "8.3"
+ filenaming restrictions. The renamings are shown in the
+ accompanying F<rename> file.
+
+ You can explore various information from the Unicode data files using
+ the C<Unicode::UCD> module.
+
+ =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>
+
+ =head1 ACKNOWLEDGEMENTS
+
+ 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 Jarkko Hietaniemi <jhi@iki.fi>
+
+ This document may be distributed under the same terms as Perl itself.
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