=item *
-Named Unicode properties and block ranges may be used as character
-classes via the new C<\p{}> (matches property) and C<\P{}> (doesn't
-match property) constructs. For instance, C<\p{Lu}> matches any
+Named Unicode properties, scripts, and block ranges may be used like
+character classes via the new C<\p{}> (matches property) and C<\P{}>
+(doesn't match property) constructs. For instance, C<\p{Lu}> matches any
character with the Unicode "Lu" (Letter, uppercase) property, while
C<\p{M}> matches any character with a "M" (mark -- accents and such)
-property. Single letter properties may omit the brackets, so that can
-be written C<\pM> also. Many predefined character classes are
-available, such as C<\p{IsMirrored}> and C<\p{InTibetan}>.
-
-The C<\p{Is...}> test for "general properties" such as "letter",
-"digit", while the C<\p{In...}> test for Unicode scripts and blocks.
+property. Single letter properties may omit the brackets, so that can be
+written C<\pM> also. Many predefined properties are available, such
+as C<\p{Mirrored}> and C<\p{Tibetan}>.
The official Unicode script and block names have spaces and dashes as
-separators, but for convenience you can have dashes, spaces, and
-underbars at every word division, and you need not care about correct
-casing. It is recommended, however, that for consistency you use the
-following naming: the official Unicode script, block, or property name
-(see below for the additional rules that apply to block names), with
-whitespace and dashes replaced with underbar, and the words
-"uppercase-first-lowercase-rest". That is, "Latin-1 Supplement"
-becomes "Latin_1_Supplement".
+separators, but for convenience you can have dashes, spaces, and underbars
+at every word division, and you need not care about correct casing. It is
+recommended, however, that for consistency you use the following naming:
+the official Unicode script, block, or property name (see below for the
+additional rules that apply to block names), with whitespace and dashes
+removed, and the words "uppercase-first-lowercase-rest". That is, "Latin-1
+Supplement" becomes "Latin1Supplement".
You can also negate both C<\p{}> and C<\P{}> by introducing a caret
-(^) between the first curly and the property name: C<\p{^In_Tamil}> is
-equal to C<\P{In_Tamil}>.
+(^) between the first curly and the property name: C<\p{^Tamil}> is
+equal to C<\P{Tamil}>.
-The C<In> and C<Is> can be left out: C<\p{Greek}> is equal to
-C<\p{In_Greek}>, C<\P{Pd}> is equal to C<\P{Pd}>.
+Here are the basic Unicode General Category properties, followed by their
+long form (you can use either, e.g. C<\p{Lu}> and C<\p{LowercaseLetter}>
+are identical).
Short Long
L Letter
- Lu Uppercase_Letter
- Ll Lowercase_Letter
- Lt Titlecase_Letter
- Lm Modifier_Letter
- Lo Other_Letter
+ Lu UppercaseLetter
+ Ll LowercaseLetter
+ Lt TitlecaseLetter
+ Lm ModifierLetter
+ Lo OtherLetter
M Mark
- Mn Nonspacing_Mark
- Mc Spacing_Mark
- Me Enclosing_Mark
+ Mn NonspacingMark
+ Mc SpacingMark
+ Me EnclosingMark
N Number
- Nd Decimal_Number
- Nl Letter_Number
- No Other_Number
+ Nd DecimalNumber
+ Nl LetterNumber
+ No OtherNumber
P Punctuation
- Pc Connector_Punctuation
- Pd Dash_Punctuation
- Ps Open_Punctuation
- Pe Close_Punctuation
- Pi Initial_Punctuation
+ Pc ConnectorPunctuation
+ Pd DashPunctuation
+ Ps OpenPunctuation
+ Pe ClosePunctuation
+ Pi InitialPunctuation
(may behave like Ps or Pe depending on usage)
- Pf Final_Punctuation
+ Pf FinalPunctuation
(may behave like Ps or Pe depending on usage)
- Po Other_Punctuation
+ Po OtherPunctuation
S Symbol
- Sm Math_Symbol
- Sc Currency_Symbol
- Sk Modifier_Symbol
- So Other_Symbol
+ Sm MathSymbol
+ Sc CurrencySymbol
+ Sk ModifierSymbol
+ So OtherSymbol
Z Separator
- Zs Space_Separator
- Zl Line_Separator
- Zp Paragraph_Separator
+ Zs SpaceSeparator
+ Zl LineSeparator
+ Zp ParagraphSeparator
C Other
Cc Control
Cf Format
- Cs Surrogate
- Co Private_Use
+ Cs Surrogate (not usable)
+ Co PrivateUse
Cn Unassigned
The single-letter properties match all characters in any of the
two-letter sub-properties starting with the same letter.
There's also C<L&> which is an alias for C<Ll>, C<Lu>, and C<Lt>.
-The following reserved ranges have C<In> tests:
-
- CJK_Ideograph_Extension_A
- CJK_Ideograph
- Hangul_Syllable
- Non_Private_Use_High_Surrogate
- Private_Use_High_Surrogate
- Low_Surrogate
- Private_Surrogate
- CJK_Ideograph_Extension_B
- Plane_15_Private_Use
- Plane_16_Private_Use
+Because Perl hides the need for the user to understand the internal
+representation of Unicode characters, it has no need to support the
+somewhat messy concept of surrogates. Therefore, the C<Cs> property is not
+supported.
-For example C<"\x{AC00}" =~ \p{HangulSyllable}> will test true.
-(Handling of surrogates is not implemented yet, because Perl
-uses UTF-8 and not UTF-16 internally to represent Unicode.
-So you really can't use the "Cs" category.)
+Because scripts differ in their directionality (for example Hebrew is
+written right to left), Unicode supplies these properties:
-Additionally, because scripts differ in their directionality
-(for example Hebrew is written right to left), all characters
-have their directionality defined:
+ Property Meaning
BidiL Left-to-Right
BidiLRE Left-to-Right Embedding
BidiWS Whitespace
BidiON Other Neutrals
+For example, C<\p{BidiR}> matches all characters that are normally
+written right to left.
+
=back
=head2 Scripts
-The scripts available for C<\p{In...}> and C<\P{In...}>, for example
-C<\p{InLatin}> or \p{InCyrillic>, are as follows:
+The scripts available via C<\p{...}> and C<\P{...}>, for example
+C<\p{Latin}> or \p{Cyrillic>, are as follows:
Arabic
Armenian
Bengali
Bopomofo
- Canadian-Aboriginal
+ CanadianAboriginal
Cherokee
Cyrillic
Deseret
Mongolian
Myanmar
Ogham
- Old-Italic
+ OldItalic
Oriya
Runic
Sinhala
properties, defined by the F<PropList> Unicode database:
ASCII_Hex_Digit
- Bidi_Control
+ BidiControl
Dash
Diacritic
Extender
- Hex_Digit
+ HexDigit
Hyphen
Ideographic
- Join_Control
- Noncharacter_Code_Point
- Other_Alphabetic
- Other_Lowercase
- Other_Math
- Other_Uppercase
- Quotation_Mark
- White_Space
+ JoinControl
+ NoncharacterCodePoint
+ OtherAlphabetic
+ OtherLowercase
+ OtherMath
+ OtherUppercase
+ QuotationMark
+ WhiteSpace
and further derived properties:
- Alphabetic Lu + Ll + Lt + Lm + Lo + Other_Alphabetic
- Lowercase Ll + Other_Lowercase
- Uppercase Lu + Other_Uppercase
- Math Sm + Other_Math
+ Alphabetic Lu + Ll + Lt + Lm + Lo + OtherAlphabetic
+ Lowercase Ll + OtherLowercase
+ Uppercase Lu + OtherUppercase
+ Math Sm + OtherMath
ID_Start Lu + Ll + Lt + Lm + Lo + Nl
ID_Continue ID_Start + Mn + Mc + Nd + Pc
Any Any character
- Assigned Any non-Cn character
+ Assigned Any non-Cn character (i.e. synonym for C<\P{Cn}>)
+ Unassigned Synonym for C<\p{Cn}>
Common Any character (or unassigned code point)
not explicitly assigned to a script
+For backward compatability, all properties mentioned so far may have C<Is>
+prepended to their name (e.g. C<\P{IsLu}> is equal to C<\P{Lu}>).
+
=head2 Blocks
-In addition to B<scripts>, Unicode also defines B<blocks> of
-characters. The difference between scripts and blocks is that the
-scripts concept is closer to natural languages, while the blocks
-concept is more an artificial grouping based on groups of 256 Unicode
-characters. For example, the C<Latin> script contains letters from
-many blocks. On the other hand, the C<Latin> script does not contain
-all the characters from those blocks. It does not, for example,
-contain digits because digits are shared across many scripts. Digits
-and other similar groups, like punctuation, are in a category called
-C<Common>.
+In addition to B<scripts>, Unicode also defines B<blocks> of characters.
+The difference between scripts and blocks is that the scripts concept is
+closer to natural languages, while the blocks concept is more an artificial
+grouping based on groups of mostly 256 Unicode characters. For example, the
+C<Latin> script contains letters from many blocks. On the other hand, the
+C<Latin> script does not contain all the characters from those blocks. It
+does not, for example, contain digits because digits are shared across many
+scripts. Digits and other similar groups, like punctuation, are in a
+category called C<Common>.
For more about scripts, see the UTR #24:
http://www.unicode.org/Public/UNIDATA/Blocks.txt
-Because there are overlaps in naming (there are, for example, both
-a script called C<Katakana> and a block called C<Katakana>, the block
-version has C<Block> appended to its name, C<\p{InKatakanaBlock}>.
-
-Notice that this definition was introduced in Perl 5.8.0: in Perl
-5.6 only the blocks were used; in Perl 5.8.0 scripts became the
-preferential Unicode character class definition (prompted by
-recommendations from the Unicode consortium); this meant that
-the definitions of some character classes changed (the ones in
-the below list that have the C<Block> appended).
-
- Alphabetic Presentation Forms
- Arabic Block
- Arabic Presentation Forms-A
- Arabic Presentation Forms-B
- Armenian Block
- Arrows
- Basic Latin
- Bengali Block
- Block Elements
- Bopomofo Block
- Bopomofo Extended
- Box Drawing
- Braille Patterns
- Byzantine Musical Symbols
- CJK Compatibility
- CJK Compatibility Forms
- CJK Compatibility Ideographs
- CJK Compatibility Ideographs Supplement
- CJK Radicals Supplement
- CJK Symbols and Punctuation
- CJK Unified Ideographs
- CJK Unified Ideographs Extension A
- CJK Unified Ideographs Extension B
- Cherokee Block
- Combining Diacritical Marks
- Combining Half Marks
- Combining Marks for Symbols
- Control Pictures
- Currency Symbols
- Cyrillic Block
- Deseret Block
- Devanagari Block
- Dingbats
- Enclosed Alphanumerics
- Enclosed CJK Letters and Months
- Ethiopic Block
- General Punctuation
- Geometric Shapes
- Georgian Block
- Gothic Block
- Greek Block
- Greek Extended
- Gujarati Block
- Gurmukhi Block
- Halfwidth and Fullwidth Forms
- Hangul Compatibility Jamo
- Hangul Jamo
- Hangul Syllables
- Hebrew Block
- High Private Use Surrogates
- High Surrogates
- Hiragana Block
- IPA Extensions
- Ideographic Description Characters
- Kanbun
- Kangxi Radicals
- Kannada Block
- Katakana Block
- Khmer Block
- Lao Block
- Latin 1 Supplement
- Latin Extended Additional
- Latin Extended-A
- Latin Extended-B
- Letterlike Symbols
- Low Surrogates
- Malayalam Block
- Mathematical Alphanumeric Symbols
- Mathematical Operators
- Miscellaneous Symbols
- Miscellaneous Technical
- Mongolian Block
- Musical Symbols
- Myanmar Block
- Number Forms
- Ogham Block
- Old Italic Block
- Optical Character Recognition
- Oriya Block
- Private Use
- Runic Block
- Sinhala Block
- Small Form Variants
- Spacing Modifier Letters
- Specials
- Superscripts and Subscripts
- Syriac Block
- Tags
- Tamil Block
- Telugu Block
- Thaana Block
- Thai Block
- Tibetan Block
- Unified Canadian Aboriginal Syllabics
- Yi Radicals
- Yi Syllables
+Blocks names are given with the C<In> prefix. For example, the
+Katakana block is referenced via C<\p{InKatakana}>. The C<In>
+prefix may be omitted if there is no nameing conflict with a script
+or any other property, but it is recommended that C<In> always be used
+to avoid confusion.
+
+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
=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
Level 1 - Basic Unicode Support
2.1 Hex Notation - done [1]
- Named Notation - done [2]
+ Named Notation - done [2]
2.2 Categories - done [3][4]
2.3 Subtraction - MISSING [5][6]
2.4 Simple Word Boundaries - done [7]
[ 1] \x{...}
[ 2] \N{...}
- [ 3] . \p{Is...} \P{Is...}
+ [ 3] . \p{...} \P{...}
[ 4] now scripts (see UTR#24 Script Names) in addition to blocks
[ 5] have negation
[ 6] can use look-ahead to emulate subtraction (*)
[ 7] include Letters in word characters
- [ 8] some cases of "ss"/"SS" matching U+00DF in a character
- class are missing, but that is allowed according to the TR18.
+ [ 8] note that perl does Full casefolding in matching, not Simple:
+ for example U+1F88 is equivalent with U+1F000 U+03B9,
+ not with 1F80. This difference matters for certain Greek
+ capital letters with certain modifiers: the Full casefolding
+ decomposes the letter, while the Simple casefolding would map
+ it to a single character.
[ 9] see UTR#13 Unicode Newline Guidelines
[10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029})
(should also affect <>, $., and script line numbers)
+ (the \x{85}, \x{2028} and \x{2029} do match \s)
(*) You can mimic class subtraction using lookahead.
For example, what TR18 might write as
in Perl can be written as:
- (?!\p{UNASSIGNED})\p{GreekBlock}
- (?=\p{ASSIGNED})\p{GreekBlock}
+ (?!\p{Unassigned})\p{InGreek}
+ (?=\p{Assigned})\p{InGreek}
But in this particular example, you probably really want
=over 4
-=item UTF-8
+=item *
+
+UTF-8
UTF-8 is a variable-length (1 to 6 bytes, current character allocations
require 4 bytes), byteorder independent encoding. For ASCII, UTF-8 is
transparent (and we really do mean 7-bit ASCII, not another 8-bit encoding).
-The following table is from Unicode 3.1.
+The following table is from Unicode 3.2.
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
- U+0000..U+007F 00..7F
- U+0080..U+07FF C2..DF 80..BF
+ U+0000..U+007F 00..7F
+ U+0080..U+07FF C2..DF 80..BF
U+0800..U+0FFF E0 A0..BF 80..BF
- U+1000..U+FFFF E1..EF 80..BF 80..BF
+ U+1000..U+CFFF E1..EC 80..BF 80..BF
+ U+D000..U+D7FF ED 80..9F 80..BF
+ U+D800..U+DFFF ******* ill-formed *******
+ U+E000..U+FFFF EE..EF 80..BF 80..BF
U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF
U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
+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.
Or, another way to look at it, as bits:
Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa
As you can see, the continuation bytes all begin with C<10>, and the
-leading bits of the start byte tells how many bytes the are in the
+leading bits of the start byte tell how many bytes the are in the
encoded character.
-=item UTF-EBCDIC
+=item *
+
+UTF-EBCDIC
Like UTF-8, but EBCDIC-safe, as UTF-8 is ASCII-safe.
-=item UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks)
+=item *
+
+UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks)
(The followings items are mostly for reference, Perl doesn't
use them internally.)
little-endian format" and cannot be "0xFFFE, represented in big-endian
format".
-=item UTF-32, UTF-32BE, UTF32-LE
+=item *
+
+UTF-32, UTF-32BE, UTF32-LE
The UTF-32 family is pretty much like the UTF-16 family, expect that
the units are 32-bit, and therefore the surrogate scheme is not
needed. The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and
0xFF 0xFE 0x00 0x00 for LE.
-=item UCS-2, UCS-4
+=item *
+
+UCS-2, UCS-4
Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit
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 UTF-7
+=item *
+
+UTF-7
A seven-bit safe (non-eight-bit) encoding, useful if the
transport/storage is not eight-bit safe. Defined by RFC 2152.
=head2 Using Unicode in XS
If you want to handle Perl Unicode in XS extensions, you may find
-the following C APIs useful:
+the following C APIs useful (see perlapi for details):
=over 4
=item *
-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. Remember that UTF8
-flag being on does not mean that there would be any characters
-of code points greater than 255 or 127 in the scalar, or that
-there even are any characters in the scalar. The UTF8 flag
-means that any characters added to the string will be encoded
-in UTF8 if the code points of the characters are greater than
-255. Not "if greater than 127", since Perl's Unicode model
-is not to use UTF-8 until it's really necessary.
+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 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 *
=item *
-utf8_length(s, len) returns the length of the UTF-8 encoded buffer in
-characters. sv_len_utf8(sv) returns the length of the UTF-8 encoded
+utf8_length(start, end) returns the length of the UTF-8 encoded buffer
+in characters. sv_len_utf8(sv) returns the length of the UTF-8 encoded
scalar.
=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 *
-is_utf8_char(buf) returns true if the buffer points to valid UTF-8.
+is_utf8_char(s) returns true if the pointer points to a valid UTF-8
+character.
=item *
UTF8SKIP(buf) will return the number of bytes in the UTF-8 encoded
character in the buffer. UNISKIP(chr) will return the number of bytes
-required to UTF-8-encode the Unicode character code point.
+required to UTF-8-encode the Unicode character code point. UTF8SKIP()
+is useful for example for iterating over the characters of a UTF-8
+encoded buffer; UNISKIP() is useful for example in computing
+the size required for a UTF-8 encoded buffer.
=item *
utf8_hop(s, off) will return a pointer to an UTF-8 encoded buffer that
is C<off> (positive or negative) Unicode characters displaced from the
-UTF-8 buffer C<s>.
+UTF-8 buffer C<s>. Be careful not to overstep the buffer: utf8_hop()
+will merrily run off the end or the beginning if told to do so.
=item *
pv_uni_display(dsv, spv, len, pvlim, flags) and sv_uni_display(dsv,
ssv, pvlim, flags) are useful for debug output of Unicode strings and
-scalars (only for debug: they display B<all> characters as hexadecimal
-code points).
+scalars. By default they are useful only for debug: they display
+B<all> characters as hexadecimal code points, but with the flags
+UNI_DISPLAY_ISPRINT and UNI_DISPLAY_BACKSLASH you can make the output
+more readable.
=item *
-ibcmp_utf8(s1, u1, len1, s2, u2, len2) can be used to compare two
-strings case-insensitively in Unicode. (For case-sensitive
-comparisons you can just use memEQ() and memNE() as usual.)
+ibcmp_utf8(s1, pe1, u1, l1, u1, s2, pe2, l2, u2) can be used to
+compare two strings case-insensitively in Unicode.
+(For case-sensitive comparisons you can just use memEQ() and memNE()
+as usual.)
=back
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. Avoidance of locales is strongly encouraged.
+
+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