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diff --git a/chromium/third_party/cygwin/lib/perl5/5.10/pods/perlunifaq.pod b/chromium/third_party/cygwin/lib/perl5/5.10/pods/perlunifaq.pod deleted file mode 100644 index b2913349cc4..00000000000 --- a/chromium/third_party/cygwin/lib/perl5/5.10/pods/perlunifaq.pod +++ /dev/null @@ -1,305 +0,0 @@ -=head1 NAME - -perlunifaq - Perl Unicode FAQ - -=head1 Q and A - -This is a list of questions and answers about Unicode in Perl, intended to be -read after L<perlunitut>. - -=head2 perlunitut isn't really a Unicode tutorial, is it? - -No, and this isn't really a Unicode FAQ. - -Perl has an abstracted interface for all supported character encodings, so they -is actually a generic C<Encode> tutorial and C<Encode> FAQ. But many people -think that Unicode is special and magical, and I didn't want to disappoint -them, so I decided to call the document a Unicode tutorial. - -=head2 What character encodings does Perl support? - -To find out which character encodings your Perl supports, run: - - perl -MEncode -le "print for Encode->encodings(':all')" - -=head2 Which version of perl should I use? - -Well, if you can, upgrade to the most recent, but certainly C<5.8.1> or newer. -The tutorial and FAQ are based on the status quo as of C<5.8.8>. - -You should also check your modules, and upgrade them if necessary. For example, -HTML::Entities requires version >= 1.32 to function correctly, even though the -changelog is silent about this. - -=head2 What about binary data, like images? - -Well, apart from a bare C<binmode $fh>, you shouldn't treat them specially. -(The binmode is needed because otherwise Perl may convert line endings on Win32 -systems.) - -Be careful, though, to never combine text strings with binary strings. If you -need text in a binary stream, encode your text strings first using the -appropriate encoding, then join them with binary strings. See also: "What if I -don't encode?". - -=head2 When should I decode or encode? - -Whenever you're communicating text with anything that is external to your perl -process, like a database, a text file, a socket, or another program. Even if -the thing you're communicating with is also written in Perl. - -=head2 What if I don't decode? - -Whenever your encoded, binary string is used together with a text string, Perl -will assume that your binary string was encoded with ISO-8859-1, also known as -latin-1. If it wasn't latin-1, then your data is unpleasantly converted. For -example, if it was UTF-8, the individual bytes of multibyte characters are seen -as separate characters, and then again converted to UTF-8. Such double encoding -can be compared to double HTML encoding (C<&gt;>), or double URI encoding -(C<%253E>). - -This silent implicit decoding is known as "upgrading". That may sound -positive, but it's best to avoid it. - -=head2 What if I don't encode? - -Your text string will be sent using the bytes in Perl's internal format. In -some cases, Perl will warn you that you're doing something wrong, with a -friendly warning: - - Wide character in print at example.pl line 2. - -Because the internal format is often UTF-8, these bugs are hard to spot, -because UTF-8 is usually the encoding you wanted! But don't be lazy, and don't -use the fact that Perl's internal format is UTF-8 to your advantage. Encode -explicitly to avoid weird bugs, and to show to maintenance programmers that you -thought this through. - -=head2 Is there a way to automatically decode or encode? - -If all data that comes from a certain handle is encoded in exactly the same -way, you can tell the PerlIO system to automatically decode everything, with -the C<encoding> layer. If you do this, you can't accidentally forget to decode -or encode anymore, on things that use the layered handle. - -You can provide this layer when C<open>ing the file: - - open my $fh, '>:encoding(UTF-8)', $filename; # auto encoding on write - open my $fh, '<:encoding(UTF-8)', $filename; # auto decoding on read - -Or if you already have an open filehandle: - - binmode $fh, ':encoding(UTF-8)'; - -Some database drivers for DBI can also automatically encode and decode, but -that is sometimes limited to the UTF-8 encoding. - -=head2 What if I don't know which encoding was used? - -Do whatever you can to find out, and if you have to: guess. (Don't forget to -document your guess with a comment.) - -You could open the document in a web browser, and change the character set or -character encoding until you can visually confirm that all characters look the -way they should. - -There is no way to reliably detect the encoding automatically, so if people -keep sending you data without charset indication, you may have to educate them. - -=head2 Can I use Unicode in my Perl sources? - -Yes, you can! If your sources are UTF-8 encoded, you can indicate that with the -C<use utf8> pragma. - - use utf8; - -This doesn't do anything to your input, or to your output. It only influences -the way your sources are read. You can use Unicode in string literals, in -identifiers (but they still have to be "word characters" according to C<\w>), -and even in custom delimiters. - -=head2 Data::Dumper doesn't restore the UTF8 flag; is it broken? - -No, Data::Dumper's Unicode abilities are as they should be. There have been -some complaints that it should restore the UTF8 flag when the data is read -again with C<eval>. However, you should really not look at the flag, and -nothing indicates that Data::Dumper should break this rule. - -Here's what happens: when Perl reads in a string literal, it sticks to 8 bit -encoding as long as it can. (But perhaps originally it was internally encoded -as UTF-8, when you dumped it.) When it has to give that up because other -characters are added to the text string, it silently upgrades the string to -UTF-8. - -If you properly encode your strings for output, none of this is of your -concern, and you can just C<eval> dumped data as always. - -=head2 Why do regex character classes sometimes match only in the ASCII range? - -=head2 Why do some characters not uppercase or lowercase correctly? - -It seemed like a good idea at the time, to keep the semantics the same for -standard strings, when Perl got Unicode support. While it might be repaired -in the future, we now have to deal with the fact that Perl treats equal -strings differently, depending on the internal state. - -Affected are C<uc>, C<lc>, C<ucfirst>, C<lcfirst>, C<\U>, C<\L>, C<\u>, C<\l>, -C<\d>, C<\s>, C<\w>, C<\D>, C<\S>, C<\W>, C</.../i>, C<(?i:...)>, -C</[[:posix:]]/>. - -To force Unicode semantics, you can upgrade the internal representation to -by doing C<utf8::upgrade($string)>. This does not change strings that were -already upgraded. - -For a more detailed discussion, see L<Unicode::Semantics> on CPAN. - -=head2 How can I determine if a string is a text string or a binary string? - -You can't. Some use the UTF8 flag for this, but that's misuse, and makes well -behaved modules like Data::Dumper look bad. The flag is useless for this -purpose, because it's off when an 8 bit encoding (by default ISO-8859-1) is -used to store the string. - -This is something you, the programmer, has to keep track of; sorry. You could -consider adopting a kind of "Hungarian notation" to help with this. - -=head2 How do I convert from encoding FOO to encoding BAR? - -By first converting the FOO-encoded byte string to a text string, and then the -text string to a BAR-encoded byte string: - - my $text_string = decode('FOO', $foo_string); - my $bar_string = encode('BAR', $text_string); - -or by skipping the text string part, and going directly from one binary -encoding to the other: - - use Encode qw(from_to); - from_to($string, 'FOO', 'BAR'); # changes contents of $string - -or by letting automatic decoding and encoding do all the work: - - open my $foofh, '<:encoding(FOO)', 'example.foo.txt'; - open my $barfh, '>:encoding(BAR)', 'example.bar.txt'; - print { $barfh } $_ while <$foofh>; - -=head2 What are C<decode_utf8> and C<encode_utf8>? - -These are alternate syntaxes for C<decode('utf8', ...)> and C<encode('utf8', -...)>. - -=head2 What is a "wide character"? - -This is a term used both for characters with an ordinal value greater than 127, -characters with an ordinal value greater than 255, or any character occupying -than one byte, depending on the context. - -The Perl warning "Wide character in ..." is caused by a character with an -ordinal value greater than 255. With no specified encoding layer, Perl tries to -fit things in ISO-8859-1 for backward compatibility reasons. When it can't, it -emits this warning (if warnings are enabled), and outputs UTF-8 encoded data -instead. - -To avoid this warning and to avoid having different output encodings in a single -stream, always specify an encoding explicitly, for example with a PerlIO layer: - - binmode STDOUT, ":encoding(UTF-8)"; - -=head1 INTERNALS - -=head2 What is "the UTF8 flag"? - -Please, unless you're hacking the internals, or debugging weirdness, don't -think about the UTF8 flag at all. That means that you very probably shouldn't -use C<is_utf8>, C<_utf8_on> or C<_utf8_off> at all. - -The UTF8 flag, also called SvUTF8, is an internal flag that indicates that the -current internal representation is UTF-8. Without the flag, it is assumed to be -ISO-8859-1. Perl converts between these automatically. - -One of Perl's internal formats happens to be UTF-8. Unfortunately, Perl can't -keep a secret, so everyone knows about this. That is the source of much -confusion. It's better to pretend that the internal format is some unknown -encoding, and that you always have to encode and decode explicitly. - -=head2 What about the C<use bytes> pragma? - -Don't use it. It makes no sense to deal with bytes in a text string, and it -makes no sense to deal with characters in a byte string. Do the proper -conversions (by decoding/encoding), and things will work out well: you get -character counts for decoded data, and byte counts for encoded data. - -C<use bytes> is usually a failed attempt to do something useful. Just forget -about it. - -=head2 What about the C<use encoding> pragma? - -Don't use it. Unfortunately, it assumes that the programmer's environment and -that of the user will use the same encoding. It will use the same encoding for -the source code and for STDIN and STDOUT. When a program is copied to another -machine, the source code does not change, but the STDIO environment might. - -If you need non-ASCII characters in your source code, make it a UTF-8 encoded -file and C<use utf8>. - -If you need to set the encoding for STDIN, STDOUT, and STDERR, for example -based on the user's locale, C<use open>. - -=head2 What is the difference between C<:encoding> and C<:utf8>? - -Because UTF-8 is one of Perl's internal formats, you can often just skip the -encoding or decoding step, and manipulate the UTF8 flag directly. - -Instead of C<:encoding(UTF-8)>, you can simply use C<:utf8>, which skips the -encoding step if the data was already represented as UTF8 internally. This is -widely accepted as good behavior when you're writing, but it can be dangerous -when reading, because it causes internal inconsistency when you have invalid -byte sequences. Using C<:utf8> for input can sometimes result in security -breaches, so please use C<:encoding(UTF-8)> instead. - -Instead of C<decode> and C<encode>, you could use C<_utf8_on> and C<_utf8_off>, -but this is considered bad style. Especially C<_utf8_on> can be dangerous, for -the same reason that C<:utf8> can. - -There are some shortcuts for oneliners; see C<-C> in L<perlrun>. - -=head2 What's the difference between C<UTF-8> and C<utf8>? - -C<UTF-8> is the official standard. C<utf8> is Perl's way of being liberal in -what it accepts. If you have to communicate with things that aren't so liberal, -you may want to consider using C<UTF-8>. If you have to communicate with things -that are too liberal, you may have to use C<utf8>. The full explanation is in -L<Encode>. - -C<UTF-8> is internally known as C<utf-8-strict>. The tutorial uses UTF-8 -consistently, even where utf8 is actually used internally, because the -distinction can be hard to make, and is mostly irrelevant. - -For example, utf8 can be used for code points that don't exist in Unicode, like -9999999, but if you encode that to UTF-8, you get a substitution character (by -default; see L<Encode/"Handling Malformed Data"> for more ways of dealing with -this.) - -Okay, if you insist: the "internal format" is utf8, not UTF-8. (When it's not -some other encoding.) - -=head2 I lost track; what encoding is the internal format really? - -It's good that you lost track, because you shouldn't depend on the internal -format being any specific encoding. But since you asked: by default, the -internal format is either ISO-8859-1 (latin-1), or utf8, depending on the -history of the string. On EBCDIC platforms, this may be different even. - -Perl knows how it stored the string internally, and will use that knowledge -when you C<encode>. In other words: don't try to find out what the internal -encoding for a certain string is, but instead just encode it into the encoding -that you want. - -=head1 AUTHOR - -Juerd Waalboer <#####@juerd.nl> - -=head1 SEE ALSO - -L<perlunicode>, L<perluniintro>, L<Encode> - |