perl's encoding on output by use of the ":encoding(...)" layer.
See L<open>.
+In some filesystems (for example Microsoft NTFS and Apple HFS+) the
+filenames are in UTF-8 . By using opendir() and File::Glob you can
+make readdir() and glob() to return the filenames as Unicode, see
+L<perlfunc/opendir> and L<File::Glob> for details.
+
To mark the Perl source itself as being in a particular encoding,
see L<encoding>.
=item *
-Strings and patterns may contain characters that have an ordinal value
-larger than 255.
+Strings (including hash keys) and regular expression patterns may
+contain characters that have an ordinal value larger than 255.
If you use a Unicode editor to edit your program, Unicode characters
may occur directly within the literal strings in one of the various
This works only for characters with a code 0x100 and above.
Additionally, if you
+
use charnames ':full';
+
you can use the C<\N{...}> notation, putting the official Unicode character
name within the curlies. For example, C<\N{WHITE SMILING FACE}>.
This works for all characters that have names.
=item *
-If an appropriate L<encoding> is specified,
-identifiers within the Perl script may contain Unicode alphanumeric
-characters, including ideographs. (You are currently on your own when
-it comes to using the canonical forms of characters--Perl doesn't
-(yet) attempt to canonicalize variable names for you.)
+If an appropriate L<encoding> is specified, identifiers within the
+Perl script may contain Unicode alphanumeric characters, including
+ideographs. (You are currently on your own when it comes to using the
+canonical forms of characters--Perl doesn't (yet) attempt to
+canonicalize variable names for you.)
=item *
Armenian
Bengali
Bopomofo
+ Buhid
CanadianAboriginal
Cherokee
Cyrillic
Gurmukhi
Han
Hangul
+ Hanunoo
Hebrew
Hiragana
Inherited
Runic
Sinhala
Syriac
+ Tagalog
+ Tagbanwa
Tamil
Telugu
Thaana
There are also extended property classes that supplement the basic
properties, defined by the F<PropList> Unicode database:
- ASCII_Hex_Digit
+ ASCIIHexDigit
BidiControl
Dash
+ Deprecated
Diacritic
Extender
+ GraphemeLink
HexDigit
Hyphen
Ideographic
+ IDSBinaryOperator
+ IDSTrinaryOperator
JoinControl
+ LogicalOrderException
NoncharacterCodePoint
OtherAlphabetic
+ OtherDefaultIgnorableCodePoint
+ OtherGraphemeExtend
OtherLowercase
OtherMath
OtherUppercase
QuotationMark
+ Radical
+ SoftDotted
+ TerminalPunctuation
+ UnifiedIdeograph
WhiteSpace
and further derived properties:
These block names are supported:
- InAlphabeticPresentationForms
- InArabicBlock
- InArabicPresentationFormsA
- InArabicPresentationFormsB
- InArmenianBlock
- InArrows
- InBasicLatin
- InBengaliBlock
- InBlockElements
- InBopomofoBlock
- InBopomofoExtended
- InBoxDrawing
- InBraillePatterns
- InByzantineMusicalSymbols
- InCJKCompatibility
- InCJKCompatibilityForms
- InCJKCompatibilityIdeographs
- InCJKCompatibilityIdeographsSupplement
- InCJKRadicalsSupplement
- InCJKSymbolsAndPunctuation
- InCJKUnifiedIdeographs
- InCJKUnifiedIdeographsExtensionA
- InCJKUnifiedIdeographsExtensionB
- InCherokeeBlock
- InCombiningDiacriticalMarks
- InCombiningHalfMarks
- InCombiningMarksForSymbols
- InControlPictures
- InCurrencySymbols
- InCyrillicBlock
- InDeseretBlock
- InDevanagariBlock
- InDingbats
- InEnclosedAlphanumerics
- InEnclosedCJKLettersAndMonths
- InEthiopicBlock
- InGeneralPunctuation
- InGeometricShapes
- InGeorgianBlock
- InGothicBlock
- InGreekBlock
- InGreekExtended
- InGujaratiBlock
- InGurmukhiBlock
- InHalfwidthAndFullwidthForms
- InHangulCompatibilityJamo
- InHangulJamo
- InHangulSyllables
- InHebrewBlock
- InHighPrivateUseSurrogates
- InHighSurrogates
- InHiraganaBlock
- InIPAExtensions
- InIdeographicDescriptionCharacters
- InKanbun
- InKangxiRadicals
- InKannadaBlock
- InKatakanaBlock
- InKhmerBlock
- InLaoBlock
- InLatin1Supplement
- InLatinExtendedAdditional
- InLatinExtended-A
- InLatinExtended-B
- InLetterlikeSymbols
- InLowSurrogates
- InMalayalamBlock
- InMathematicalAlphanumericSymbols
- InMathematicalOperators
- InMiscellaneousSymbols
- InMiscellaneousTechnical
- InMongolianBlock
- InMusicalSymbols
- InMyanmarBlock
- InNumberForms
- InOghamBlock
- InOldItalicBlock
- InOpticalCharacterRecognition
- InOriyaBlock
- InPrivateUse
- InRunicBlock
- InSinhalaBlock
- InSmallFormVariants
- InSpacingModifierLetters
- InSpecials
- InSuperscriptsAndSubscripts
- InSyriacBlock
- InTags
- InTamilBlock
- InTeluguBlock
- InThaanaBlock
- InThaiBlock
- InTibetanBlock
- InUnifiedCanadianAboriginalSyllabics
- InYiRadicals
- InYiSyllables
+ InAlphabeticPresentationForms
+ InArabic
+ InArabicPresentationFormsA
+ InArabicPresentationFormsB
+ InArmenian
+ InArrows
+ InBasicLatin
+ InBengali
+ InBlockElements
+ InBopomofo
+ InBopomofoExtended
+ InBoxDrawing
+ InBraillePatterns
+ InBuhid
+ InByzantineMusicalSymbols
+ InCJKCompatibility
+ InCJKCompatibilityForms
+ InCJKCompatibilityIdeographs
+ InCJKCompatibilityIdeographsSupplement
+ InCJKRadicalsSupplement
+ InCJKSymbolsAndPunctuation
+ InCJKUnifiedIdeographs
+ InCJKUnifiedIdeographsExtensionA
+ InCJKUnifiedIdeographsExtensionB
+ InCherokee
+ InCombiningDiacriticalMarks
+ InCombiningDiacriticalMarksforSymbols
+ InCombiningHalfMarks
+ InControlPictures
+ InCurrencySymbols
+ InCyrillic
+ InCyrillicSupplementary
+ InDeseret
+ InDevanagari
+ InDingbats
+ InEnclosedAlphanumerics
+ InEnclosedCJKLettersAndMonths
+ InEthiopic
+ InGeneralPunctuation
+ InGeometricShapes
+ InGeorgian
+ InGothic
+ InGreekExtended
+ InGreekAndCoptic
+ InGujarati
+ InGurmukhi
+ InHalfwidthAndFullwidthForms
+ InHangulCompatibilityJamo
+ InHangulJamo
+ InHangulSyllables
+ InHanunoo
+ InHebrew
+ InHighPrivateUseSurrogates
+ InHighSurrogates
+ InHiragana
+ InIPAExtensions
+ InIdeographicDescriptionCharacters
+ InKanbun
+ InKangxiRadicals
+ InKannada
+ InKatakana
+ InKatakanaPhoneticExtensions
+ InKhmer
+ InLao
+ InLatin1Supplement
+ InLatinExtendedA
+ InLatinExtendedAdditional
+ InLatinExtendedB
+ InLetterlikeSymbols
+ InLowSurrogates
+ InMalayalam
+ InMathematicalAlphanumericSymbols
+ InMathematicalOperators
+ InMiscellaneousMathematicalSymbolsA
+ InMiscellaneousMathematicalSymbolsB
+ InMiscellaneousSymbols
+ InMiscellaneousTechnical
+ InMongolian
+ InMusicalSymbols
+ InMyanmar
+ InNumberForms
+ InOgham
+ InOldItalic
+ InOpticalCharacterRecognition
+ InOriya
+ InPrivateUseArea
+ InRunic
+ InSinhala
+ InSmallFormVariants
+ InSpacingModifierLetters
+ InSpecials
+ InSuperscriptsAndSubscripts
+ InSupplementalArrowsA
+ InSupplementalArrowsB
+ InSupplementalMathematicalOperators
+ InSupplementaryPrivateUseAreaA
+ InSupplementaryPrivateUseAreaB
+ InSyriac
+ InTagalog
+ InTagbanwa
+ InTags
+ InTamil
+ InTelugu
+ InThaana
+ InThai
+ InTibetan
+ InUnifiedCanadianAboriginalSyllabics
+ InVariationSelectors
+ InYiRadicals
+ InYiSyllables
=over 4
=item *
-The special pattern C<\X> match matches any extended Unicode sequence
+The special pattern C<\X> matches any extended Unicode sequence
(a "combining character sequence" in Standardese), where the first
character is a base character and subsequent characters are mark
characters that apply to the base character. It is equivalent to
See L<Encode>.
-=head1 CAVEATS
-
-Whether an arbitrary piece of data will be treated as "characters" or
-"bytes" by internal operations cannot be divined at the current time.
-
-Use of locales with Unicode data may lead to odd results. Currently
-there is some attempt to apply 8-bit locale info to characters in the
-range 0..255, but this is demonstrably incorrect for locales that use
-characters above that range when mapped into Unicode. It will also
-tend to run slower. Avoidance of locales is strongly encouraged.
-
-=head1 UNICODE REGULAR EXPRESSION SUPPORT LEVEL
+=head2 Unicode Regular Expression Support Level
The following list of Unicode regular expression support describes
feature by feature the Unicode support implemented in Perl as of Perl
in Perl can be written as:
- (?!\p{Unassigned})\p{InGreek}
- (?=\p{Assigned})\p{InGreek}
+ (?!\p{Unassigned})\p{InGreekAndCoptic}
+ (?=\p{Assigned})\p{InGreekAndCoptic}
But in this particular example, you probably really want
=over 4
-=item
+=item *
UTF-8
Note the A0..BF in U+0800..U+0FFF, the 80..9F in U+D000...U+D7FF,
the 90..BF in U+10000..U+3FFFF, and the 80...8F in U+100000..U+10FFFF.
+The "gaps" are caused by legal UTF-8 avoiding non-shortest encodings:
+it is technically possible to UTF-8-encode a single code point in different
+ways, but that is explicitly forbidden, and the shortest possible encoding
+should always be used (and that is what Perl does).
+
Or, another way to look at it, as bits:
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
leading bits of the start byte tell how many bytes the are in the
encoded character.
-=item
+=item *
UTF-EBCDIC
Like UTF-8, but EBCDIC-safe, as UTF-8 is ASCII-safe.
-=item
+=item *
UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks)
and the decoding is
- $uni = 0x10000 + ($hi - 0xD8000) * 0x400 + ($lo - 0xDC00);
+ $uni = 0x10000 + ($hi - 0xD800) * 0x400 + ($lo - 0xDC00);
If you try to generate surrogates (for example by using chr()), you
will get a warning if warnings are turned on (C<-w> or C<use
little-endian format" and cannot be "0xFFFE, represented in big-endian
format".
-=item
+=item *
UTF-32, UTF-32BE, UTF32-LE
needed. The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and
0xFF 0xFE 0x00 0x00 for LE.
-=item
+=item *
UCS-2, UCS-4
encoding, UCS-4 is a 32-bit encoding. Unlike UTF-16, UCS-2
is not extensible beyond 0xFFFF, because it does not use surrogates.
-=item
+=item *
UTF-7
the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic>
for more discussion of the issues.
+=head2 Locales
+
+Usually locale settings and Unicode do not affect each other, but
+there are a couple of exceptions:
+
+=over 4
+
+=item *
+
+If your locale environment variables (LANGUAGE, LC_ALL, LC_CTYPE, LANG)
+contain the strings 'UTF-8' or 'UTF8' (case-insensitive matching),
+the default encoding of your STDIN, STDOUT, and STDERR, and of
+B<any subsequent file open>, is UTF-8.
+
+=item *
+
+Perl tries really hard to work both with Unicode and the old byte
+oriented world: most often this is nice, but sometimes this causes
+problems.
+
+=back
+
=head2 Using Unicode in XS
If you want to handle Perl Unicode in XS extensions, you may find
DO_UTF8(sv) returns true if the UTF8 flag is on and the bytes pragma
is not in effect. SvUTF8(sv) returns true is the UTF8 flag is on, the
bytes pragma is ignored. The UTF8 flag being on does B<not> mean that
-there are any characters of code points greater than 255 (or 127) in the
-scalar, or that there even are any characters in the scalar. What the
-UTF8 flag means is that the sequence of octets in the representation
-of the scalar should be treated as UTF-8 encoding of a string.
-The UTF8 flag being off means that each octet in this representation
-encodes a single character with codepoint 0..255 within the string.
-Perl's Unicode model is not to use UTF-8 until it's really necessary.
+there are any characters of code points greater than 255 (or 127) in
+the scalar, or that there even are any characters in the scalar.
+What the UTF8 flag means is that the sequence of octets in the
+representation of the scalar is the sequence of UTF-8 encoded
+code points of the characters of a string. The UTF8 flag being
+off means that each octet in this representation encodes a single
+character with codepoint 0..255 within the string. Perl's Unicode
+model is not to use UTF-8 until it's really necessary.
=item *
encoded form. sv_utf8_downgrade(sv) does the opposite (if possible).
sv_utf8_encode(sv) is like sv_utf8_upgrade but the UTF8 flag does not
get turned on. sv_utf8_decode() does the opposite of sv_utf8_encode().
+Note that none of these are to be used as general purpose encoding/decoding
+interfaces: use Encode for that. sv_utf8_upgrade() is affected by the
+encoding pragma, but sv_utf8_downgrade() is not (since the encoding
+pragma is designed to be a one-way street).
=item *
For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h>
in the Perl source code distribution.
+=head1 BUGS
+
+Use of locales with Unicode data may lead to odd results. Currently
+there is some attempt to apply 8-bit locale info to characters in the
+range 0..255, but this is demonstrably incorrect for locales that use
+characters above that range when mapped into Unicode. It will also
+tend to run slower. Use of locales with Unicode is discouraged.
+
+Some functions are slower when working on UTF-8 encoded strings than
+on byte encoded strings. All functions that need to hop over
+characters such as length(), substr() or index() can work B<much>
+faster when the underlying data are byte-encoded. Witness the
+following benchmark:
+
+ % perl -e '
+ use Benchmark;
+ use strict;
+ our $l = 10000;
+ our $u = our $b = "x" x $l;
+ substr($u,0,1) = "\x{100}";
+ timethese(-2,{
+ LENGTH_B => q{ length($b) },
+ LENGTH_U => q{ length($u) },
+ SUBSTR_B => q{ substr($b, $l/4, $l/2) },
+ SUBSTR_U => q{ substr($u, $l/4, $l/2) },
+ });
+ '
+ Benchmark: running LENGTH_B, LENGTH_U, SUBSTR_B, SUBSTR_U for at least 2 CPU seconds...
+ LENGTH_B: 2 wallclock secs ( 2.36 usr + 0.00 sys = 2.36 CPU) @ 5649983.05/s (n=13333960)
+ LENGTH_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 12155.45/s (n=25648)
+ SUBSTR_B: 3 wallclock secs ( 2.16 usr + 0.00 sys = 2.16 CPU) @ 374480.09/s (n=808877)
+ SUBSTR_U: 2 wallclock secs ( 2.11 usr + 0.00 sys = 2.11 CPU) @ 6791.00/s (n=14329)
+
+The numbers show an incredible slowness on long UTF-8 strings and you
+should carefully avoid to use these functions within tight loops. For
+example if you want to iterate over characters, it is infinitely
+better to split into an array than to use substr, as the following
+benchmark shows:
+
+ % perl -e '
+ use Benchmark;
+ use strict;
+ our $l = 10000;
+ our $u = our $b = "x" x $l;
+ substr($u,0,1) = "\x{100}";
+ timethese(-5,{
+ SPLIT_B => q{ for my $c (split //, $b){} },
+ SPLIT_U => q{ for my $c (split //, $u){} },
+ SUBSTR_B => q{ for my $i (0..length($b)-1){my $c = substr($b,$i,1);} },
+ SUBSTR_U => q{ for my $i (0..length($u)-1){my $c = substr($u,$i,1);} },
+ });
+ '
+ Benchmark: running SPLIT_B, SPLIT_U, SUBSTR_B, SUBSTR_U for at least 5 CPU seconds...
+ SPLIT_B: 6 wallclock secs ( 5.29 usr + 0.00 sys = 5.29 CPU) @ 56.14/s (n=297)
+ SPLIT_U: 5 wallclock secs ( 5.17 usr + 0.01 sys = 5.18 CPU) @ 55.21/s (n=286)
+ SUBSTR_B: 5 wallclock secs ( 5.34 usr + 0.00 sys = 5.34 CPU) @ 123.22/s (n=658)
+ SUBSTR_U: 7 wallclock secs ( 6.20 usr + 0.00 sys = 6.20 CPU) @ 0.81/s (n=5)
+
+You see, the algorithm based on substr() was faster with byte encoded
+data but it is pathologically slow with UTF-8 data.
+
=head1 SEE ALSO
L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>,
projects / p5sagit/p5-mst-13.2.git / blobdiff