3 perlunicode - Unicode support in Perl
7 =head2 Important Caveats
9 Unicode support is an extensive requirement. While perl does not
10 implement the Unicode standard or the accompanying technical reports
11 from cover to cover, Perl does support many Unicode features.
15 =item Input and Output Disciplines
17 A filehandle can be marked as containing perl's internal Unicode
18 encoding (UTF-8 or UTF-EBCDIC) by opening it with the ":utf8" layer.
19 Other encodings can be converted to perl's encoding on input, or from
20 perl's encoding on output by use of the ":encoding(...)" layer.
23 To mark the Perl source itself as being in a particular encoding,
26 =item Regular Expressions
28 The regular expression compiler produces polymorphic opcodes. That is,
29 the pattern adapts to the data and automatically switch to the Unicode
30 character scheme when presented with Unicode data, or a traditional
31 byte scheme when presented with byte data.
33 =item C<use utf8> still needed to enable UTF-8/UTF-EBCDIC in scripts
35 As a compatibility measure, this pragma must be explicitly used to
36 enable recognition of UTF-8 in the Perl scripts themselves on ASCII
37 based machines, or to recognize UTF-EBCDIC on EBCDIC based machines.
38 B<NOTE: this should be the only place where an explicit C<use utf8>
41 You can also use the C<encoding> pragma to change the default encoding
42 of the data in your script; see L<encoding>.
46 =head2 Byte and Character semantics
48 Beginning with version 5.6, Perl uses logically wide characters to
49 represent strings internally.
51 In future, Perl-level operations can be expected to work with
52 characters rather than bytes, in general.
54 However, as strictly an interim compatibility measure, Perl aims to
55 provide a safe migration path from byte semantics to character
56 semantics for programs. For operations where Perl can unambiguously
57 decide that the input data is characters, Perl now switches to
58 character semantics. For operations where this determination cannot
59 be made without additional information from the user, Perl decides in
60 favor of compatibility, and chooses to use byte semantics.
62 This behavior preserves compatibility with earlier versions of Perl,
63 which allowed byte semantics in Perl operations, but only as long as
64 none of the program's inputs are marked as being as source of Unicode
65 character data. Such data may come from filehandles, from calls to
66 external programs, from information provided by the system (such as %ENV),
67 or from literals and constants in the source text.
69 On Windows platforms, if the C<-C> command line switch is used, (or the
70 ${^WIDE_SYSTEM_CALLS} global flag is set to C<1>), all system calls
71 will use the corresponding wide character APIs. Note that this is
72 currently only implemented on Windows since other platforms lack an
73 API standard on this area.
75 Regardless of the above, the C<bytes> pragma can always be used to
76 force byte semantics in a particular lexical scope. See L<bytes>.
78 The C<utf8> pragma is primarily a compatibility device that enables
79 recognition of UTF-(8|EBCDIC) in literals encountered by the parser.
80 Note that this pragma is only required until a future version of Perl
81 in which character semantics will become the default. This pragma may
82 then become a no-op. See L<utf8>.
84 Unless mentioned otherwise, Perl operators will use character semantics
85 when they are dealing with Unicode data, and byte semantics otherwise.
86 Thus, character semantics for these operations apply transparently; if
87 the input data came from a Unicode source (for example, by adding a
88 character encoding discipline to the filehandle whence it came, or a
89 literal Unicode string constant in the program), character semantics
90 apply; otherwise, byte semantics are in effect. To force byte semantics
91 on Unicode data, the C<bytes> pragma should be used.
93 Notice that if you concatenate strings with byte semantics and strings
94 with Unicode character data, the bytes will by default be upgraded
95 I<as if they were ISO 8859-1 (Latin-1)> (or if in EBCDIC, after a
96 translation to ISO 8859-1). This is done without regard to the
97 system's native 8-bit encoding, so to change this for systems with
98 non-Latin-1 (or non-EBCDIC) native encodings, use the C<encoding>
99 pragma, see L<encoding>.
101 Under character semantics, many operations that formerly operated on
102 bytes change to operating on characters. A character in Perl is
103 logically just a number ranging from 0 to 2**31 or so. Larger
104 characters may encode to longer sequences of bytes internally, but
105 this is just an internal detail which is hidden at the Perl level.
106 See L<perluniintro> for more on this.
108 =head2 Effects of character semantics
110 Character semantics have the following effects:
116 Strings and patterns may contain characters that have an ordinal value
119 If you use a Unicode editor to edit your program, Unicode characters
120 may occur directly within the literal strings in one of the various
121 Unicode encodings (UTF-8, UTF-EBCDIC, UCS-2, etc.), but are recognized
122 as such (and converted to Perl's internal representation) only if the
123 appropriate L<encoding> is specified.
125 You can also get Unicode characters into a string by using the C<\x{...}>
126 notation, putting the Unicode code for the desired character, in
127 hexadecimal, into the curlies. For instance, a smiley face is C<\x{263A}>.
128 This works only for characters with a code 0x100 and above.
131 use charnames ':full';
132 you can use the C<\N{...}> notation, putting the official Unicode character
133 name within the curlies. For example, C<\N{WHITE SMILING FACE}>.
134 This works for all characters that have names.
138 If an appropriate L<encoding> is specified,
139 identifiers within the Perl script may contain Unicode alphanumeric
140 characters, including ideographs. (You are currently on your own when
141 it comes to using the canonical forms of characters--Perl doesn't
142 (yet) attempt to canonicalize variable names for you.)
146 Regular expressions match characters instead of bytes. For instance,
147 "." matches a character instead of a byte. (However, the C<\C> pattern
148 is provided to force a match a single byte ("C<char>" in C, hence C<\C>).)
152 Character classes in regular expressions match characters instead of
153 bytes, and match against the character properties specified in the
154 Unicode properties database. So C<\w> can be used to match an
155 ideograph, for instance.
159 Named Unicode properties, scripts, and block ranges may be used like
160 character classes via the new C<\p{}> (matches property) and C<\P{}>
161 (doesn't match property) constructs. For instance, C<\p{Lu}> matches any
162 character with the Unicode "Lu" (Letter, uppercase) property, while
163 C<\p{M}> matches any character with a "M" (mark -- accents and such)
164 property. Single letter properties may omit the brackets, so that can be
165 written C<\pM> also. Many predefined properties are available, such
166 as C<\p{Mirrored}> and C<\p{Tibetan}>.
168 The official Unicode script and block names have spaces and dashes as
169 separators, but for convenience you can have dashes, spaces, and underbars
170 at every word division, and you need not care about correct casing. It is
171 recommended, however, that for consistency you use the following naming:
172 the official Unicode script, block, or property name (see below for the
173 additional rules that apply to block names), with whitespace and dashes
174 removed, and the words "uppercase-first-lowercase-rest". That is, "Latin-1
175 Supplement" becomes "Latin1Supplement".
177 You can also negate both C<\p{}> and C<\P{}> by introducing a caret
178 (^) between the first curly and the property name: C<\p{^Tamil}> is
179 equal to C<\P{Tamil}>.
181 Here are the basic Unicode General Category properties, followed by their
182 long form (you can use either, e.g. C<\p{Lu}> and C<\p{LowercaseLetter}>
205 Pc ConnectorPunctuation
209 Pi InitialPunctuation
210 (may behave like Ps or Pe depending on usage)
212 (may behave like Ps or Pe depending on usage)
224 Zp ParagraphSeparator
229 Cs Surrogate (not usable)
233 The single-letter properties match all characters in any of the
234 two-letter sub-properties starting with the same letter.
235 There's also C<L&> which is an alias for C<Ll>, C<Lu>, and C<Lt>.
237 Because Perl hides the need for the user to understand the internal
238 representation of Unicode characters, it has no need to support the
239 somewhat messy concept of surrogates. Therefore, the C<Cs> property is not
242 Because scripts differ in their directionality (for example Hebrew is
243 written right to left), Unicode supplies these properties:
248 BidiLRE Left-to-Right Embedding
249 BidiLRO Left-to-Right Override
251 BidiAL Right-to-Left Arabic
252 BidiRLE Right-to-Left Embedding
253 BidiRLO Right-to-Left Override
254 BidiPDF Pop Directional Format
255 BidiEN European Number
256 BidiES European Number Separator
257 BidiET European Number Terminator
259 BidiCS Common Number Separator
260 BidiNSM Non-Spacing Mark
261 BidiBN Boundary Neutral
262 BidiB Paragraph Separator
263 BidiS Segment Separator
265 BidiON Other Neutrals
267 For example, C<\p{BidiR}> matches all characters that are normally
268 written right to left.
274 The scripts available via C<\p{...}> and C<\P{...}>, for example
275 C<\p{Latin}> or \p{Cyrillic>, are as follows:
318 There are also extended property classes that supplement the basic
319 properties, defined by the F<PropList> Unicode database:
330 NoncharacterCodePoint
338 and further derived properties:
340 Alphabetic Lu + Ll + Lt + Lm + Lo + OtherAlphabetic
341 Lowercase Ll + OtherLowercase
342 Uppercase Lu + OtherUppercase
345 ID_Start Lu + Ll + Lt + Lm + Lo + Nl
346 ID_Continue ID_Start + Mn + Mc + Nd + Pc
349 Assigned Any non-Cn character (i.e. synonym for C<\P{Cn}>)
350 Unassigned Synonym for C<\p{Cn}>
351 Common Any character (or unassigned code point)
352 not explicitly assigned to a script
354 For backward compatability, all properties mentioned so far may have C<Is>
355 prepended to their name (e.g. C<\P{IsLu}> is equal to C<\P{Lu}>).
359 In addition to B<scripts>, Unicode also defines B<blocks> of characters.
360 The difference between scripts and blocks is that the scripts concept is
361 closer to natural languages, while the blocks concept is more an artificial
362 grouping based on groups of mostly 256 Unicode characters. For example, the
363 C<Latin> script contains letters from many blocks. On the other hand, the
364 C<Latin> script does not contain all the characters from those blocks. It
365 does not, for example, contain digits because digits are shared across many
366 scripts. Digits and other similar groups, like punctuation, are in a
367 category called C<Common>.
369 For more about scripts, see the UTR #24:
371 http://www.unicode.org/unicode/reports/tr24/
373 For more about blocks, see:
375 http://www.unicode.org/Public/UNIDATA/Blocks.txt
377 Blocks names are given with the C<In> prefix. For example, the
378 Katakana block is referenced via C<\p{InKatakana}. The C<In>
379 prefix may be omitted if there is no nameing conflict with a script
380 or any other property, but it is recommended that C<In> always be used
383 These block names are supported:
385 InAlphabeticPresentationForms
387 InArabicPresentationFormsA
388 InArabicPresentationFormsB
398 InByzantineMusicalSymbols
400 InCJKCompatibilityForms
401 InCJKCompatibilityIdeographs
402 InCJKCompatibilityIdeographsSupplement
403 InCJKRadicalsSupplement
404 InCJKSymbolsAndPunctuation
405 InCJKUnifiedIdeographs
406 InCJKUnifiedIdeographsExtensionA
407 InCJKUnifiedIdeographsExtensionB
409 InCombiningDiacriticalMarks
411 InCombiningMarksForSymbols
418 InEnclosedAlphanumerics
419 InEnclosedCJKLettersAndMonths
429 InHalfwidthAndFullwidthForms
430 InHangulCompatibilityJamo
434 InHighPrivateUseSurrogates
438 InIdeographicDescriptionCharacters
446 InLatinExtendedAdditional
452 InMathematicalAlphanumericSymbols
453 InMathematicalOperators
454 InMiscellaneousSymbols
455 InMiscellaneousTechnical
462 InOpticalCharacterRecognition
468 InSpacingModifierLetters
470 InSuperscriptsAndSubscripts
478 InUnifiedCanadianAboriginalSyllabics
486 The special pattern C<\X> match matches any extended Unicode sequence
487 (a "combining character sequence" in Standardese), where the first
488 character is a base character and subsequent characters are mark
489 characters that apply to the base character. It is equivalent to
494 The C<tr///> operator translates characters instead of bytes. Note
495 that the C<tr///CU> functionality has been removed, as the interface
496 was a mistake. For similar functionality see pack('U0', ...) and
501 Case translation operators use the Unicode case translation tables
502 when provided character input. Note that C<uc()> (also known as C<\U>
503 in doublequoted strings) translates to uppercase, while C<ucfirst>
504 (also known as C<\u> in doublequoted strings) translates to titlecase
505 (for languages that make the distinction). Naturally the
506 corresponding backslash sequences have the same semantics.
510 Most operators that deal with positions or lengths in the string will
511 automatically switch to using character positions, including
512 C<chop()>, C<substr()>, C<pos()>, C<index()>, C<rindex()>,
513 C<sprintf()>, C<write()>, and C<length()>. Operators that
514 specifically don't switch include C<vec()>, C<pack()>, and
515 C<unpack()>. Operators that really don't care include C<chomp()>, as
516 well as any other operator that treats a string as a bucket of bits,
517 such as C<sort()>, and the operators dealing with filenames.
521 The C<pack()>/C<unpack()> letters "C<c>" and "C<C>" do I<not> change,
522 since they're often used for byte-oriented formats. (Again, think
523 "C<char>" in the C language.) However, there is a new "C<U>" specifier
524 that will convert between Unicode characters and integers.
528 The C<chr()> and C<ord()> functions work on characters. This is like
529 C<pack("U")> and C<unpack("U")>, not like C<pack("C")> and
530 C<unpack("C")>. In fact, the latter are how you now emulate
531 byte-oriented C<chr()> and C<ord()> for Unicode strings.
532 (Note that this reveals the internal encoding of Unicode strings,
533 which is not something one normally needs to care about at all.)
537 The bit string operators C<& | ^ ~> can operate on character data.
538 However, for backward compatibility reasons (bit string operations
539 when the characters all are less than 256 in ordinal value) one should
540 not mix C<~> (the bit complement) and characters both less than 256 and
541 equal or greater than 256. Most importantly, the DeMorgan's laws
542 (C<~($x|$y) eq ~$x&~$y>, C<~($x&$y) eq ~$x|~$y>) won't hold.
543 Another way to look at this is that the complement cannot return
544 B<both> the 8-bit (byte) wide bit complement B<and> the full character
549 lc(), uc(), lcfirst(), and ucfirst() work for the following cases:
555 the case mapping is from a single Unicode character to another
556 single Unicode character
560 the case mapping is from a single Unicode character to more
561 than one Unicode character
565 What doesn't yet work are the following cases:
571 the "final sigma" (Greek)
575 anything to with locales (Lithuanian, Turkish, Azeri)
579 See the Unicode Technical Report #21, Case Mappings, for more details.
583 And finally, C<scalar reverse()> reverses by character rather than by byte.
587 =head2 Character encodings for input and output
593 Whether an arbitrary piece of data will be treated as "characters" or
594 "bytes" by internal operations cannot be divined at the current time.
596 Use of locales with Unicode data may lead to odd results. Currently
597 there is some attempt to apply 8-bit locale info to characters in the
598 range 0..255, but this is demonstrably incorrect for locales that use
599 characters above that range when mapped into Unicode. It will also
600 tend to run slower. Avoidance of locales is strongly encouraged.
602 =head1 UNICODE REGULAR EXPRESSION SUPPORT LEVEL
604 The following list of Unicode regular expression support describes
605 feature by feature the Unicode support implemented in Perl as of Perl
606 5.8.0. The "Level N" and the section numbers refer to the Unicode
607 Technical Report 18, "Unicode Regular Expression Guidelines".
613 Level 1 - Basic Unicode Support
615 2.1 Hex Notation - done [1]
616 Named Notation - done [2]
617 2.2 Categories - done [3][4]
618 2.3 Subtraction - MISSING [5][6]
619 2.4 Simple Word Boundaries - done [7]
620 2.5 Simple Loose Matches - done [8]
621 2.6 End of Line - MISSING [9][10]
625 [ 3] . \p{...} \P{...}
626 [ 4] now scripts (see UTR#24 Script Names) in addition to blocks
628 [ 6] can use look-ahead to emulate subtraction (*)
629 [ 7] include Letters in word characters
630 [ 8] note that perl does Full casefolding in matching, not Simple:
631 for example U+1F88 is equivalent with U+1F000 U+03B9,
632 not with 1F80. This difference matters for certain Greek
633 capital letters with certain modifiers: the Full casefolding
634 decomposes the letter, while the Simple casefolding would map
635 it to a single character.
636 [ 9] see UTR#13 Unicode Newline Guidelines
637 [10] should do ^ and $ also on \x{85}, \x{2028} and \x{2029})
638 (should also affect <>, $., and script line numbers)
639 (the \x{85}, \x{2028} and \x{2029} do match \s)
641 (*) You can mimic class subtraction using lookahead.
642 For example, what TR18 might write as
644 [{Greek}-[{UNASSIGNED}]]
646 in Perl can be written as:
648 (?!\p{Unassigned})\p{InGreek}
649 (?=\p{Assigned})\p{InGreek}
651 But in this particular example, you probably really want
655 which will match assigned characters known to be part of the Greek script.
659 Level 2 - Extended Unicode Support
661 3.1 Surrogates - MISSING
662 3.2 Canonical Equivalents - MISSING [11][12]
663 3.3 Locale-Independent Graphemes - MISSING [13]
664 3.4 Locale-Independent Words - MISSING [14]
665 3.5 Locale-Independent Loose Matches - MISSING [15]
667 [11] see UTR#15 Unicode Normalization
668 [12] have Unicode::Normalize but not integrated to regexes
669 [13] have \X but at this level . should equal that
670 [14] need three classes, not just \w and \W
671 [15] see UTR#21 Case Mappings
675 Level 3 - Locale-Sensitive Support
677 4.1 Locale-Dependent Categories - MISSING
678 4.2 Locale-Dependent Graphemes - MISSING [16][17]
679 4.3 Locale-Dependent Words - MISSING
680 4.4 Locale-Dependent Loose Matches - MISSING
681 4.5 Locale-Dependent Ranges - MISSING
683 [16] see UTR#10 Unicode Collation Algorithms
684 [17] have Unicode::Collate but not integrated to regexes
688 =head2 Unicode Encodings
690 Unicode characters are assigned to I<code points> which are abstract
691 numbers. To use these numbers various encodings are needed.
697 UTF-8 is a variable-length (1 to 6 bytes, current character allocations
698 require 4 bytes), byteorder independent encoding. For ASCII, UTF-8 is
699 transparent (and we really do mean 7-bit ASCII, not another 8-bit encoding).
701 The following table is from Unicode 3.1.
703 Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
705 U+0000..U+007F 00..7F
706 U+0080..U+07FF C2..DF 80..BF
707 U+0800..U+0FFF E0 A0..BF 80..BF
708 U+1000..U+FFFF E1..EF 80..BF 80..BF
709 U+10000..U+3FFFF F0 90..BF 80..BF 80..BF
710 U+40000..U+FFFFF F1..F3 80..BF 80..BF 80..BF
711 U+100000..U+10FFFF F4 80..8F 80..BF 80..BF
713 Or, another way to look at it, as bits:
715 Code Points 1st Byte 2nd Byte 3rd Byte 4th Byte
718 00000bbbbbaaaaaa 110bbbbb 10aaaaaa
719 ccccbbbbbbaaaaaa 1110cccc 10bbbbbb 10aaaaaa
720 00000dddccccccbbbbbbaaaaaa 11110ddd 10cccccc 10bbbbbb 10aaaaaa
722 As you can see, the continuation bytes all begin with C<10>, and the
723 leading bits of the start byte tells how many bytes the are in the
728 Like UTF-8, but EBCDIC-safe, as UTF-8 is ASCII-safe.
730 =item UTF-16, UTF-16BE, UTF16-LE, Surrogates, and BOMs (Byte Order Marks)
732 (The followings items are mostly for reference, Perl doesn't
733 use them internally.)
735 UTF-16 is a 2 or 4 byte encoding. The Unicode code points
736 0x0000..0xFFFF are stored in two 16-bit units, and the code points
737 0x010000..0x10FFFF in two 16-bit units. The latter case is
738 using I<surrogates>, the first 16-bit unit being the I<high
739 surrogate>, and the second being the I<low surrogate>.
741 Surrogates are code points set aside to encode the 0x01000..0x10FFFF
742 range of Unicode code points in pairs of 16-bit units. The I<high
743 surrogates> are the range 0xD800..0xDBFF, and the I<low surrogates>
744 are the range 0xDC00..0xDFFFF. The surrogate encoding is
746 $hi = ($uni - 0x10000) / 0x400 + 0xD800;
747 $lo = ($uni - 0x10000) % 0x400 + 0xDC00;
751 $uni = 0x10000 + ($hi - 0xD8000) * 0x400 + ($lo - 0xDC00);
753 If you try to generate surrogates (for example by using chr()), you
754 will get a warning if warnings are turned on (C<-w> or C<use
755 warnings;>) because those code points are not valid for a Unicode
758 Because of the 16-bitness, UTF-16 is byteorder dependent. UTF-16
759 itself can be used for in-memory computations, but if storage or
760 transfer is required, either UTF-16BE (Big Endian) or UTF-16LE
761 (Little Endian) must be chosen.
763 This introduces another problem: what if you just know that your data
764 is UTF-16, but you don't know which endianness? Byte Order Marks
765 (BOMs) are a solution to this. A special character has been reserved
766 in Unicode to function as a byte order marker: the character with the
767 code point 0xFEFF is the BOM.
769 The trick is that if you read a BOM, you will know the byte order,
770 since if it was written on a big endian platform, you will read the
771 bytes 0xFE 0xFF, but if it was written on a little endian platform,
772 you will read the bytes 0xFF 0xFE. (And if the originating platform
773 was writing in UTF-8, you will read the bytes 0xEF 0xBB 0xBF.)
775 The way this trick works is that the character with the code point
776 0xFFFE is guaranteed not to be a valid Unicode character, so the
777 sequence of bytes 0xFF 0xFE is unambiguously "BOM, represented in
778 little-endian format" and cannot be "0xFFFE, represented in big-endian
781 =item UTF-32, UTF-32BE, UTF32-LE
783 The UTF-32 family is pretty much like the UTF-16 family, expect that
784 the units are 32-bit, and therefore the surrogate scheme is not
785 needed. The BOM signatures will be 0x00 0x00 0xFE 0xFF for BE and
786 0xFF 0xFE 0x00 0x00 for LE.
790 Encodings defined by the ISO 10646 standard. UCS-2 is a 16-bit
791 encoding, UCS-4 is a 32-bit encoding. Unlike UTF-16, UCS-2
792 is not extensible beyond 0xFFFF, because it does not use surrogates.
796 A seven-bit safe (non-eight-bit) encoding, useful if the
797 transport/storage is not eight-bit safe. Defined by RFC 2152.
801 =head2 Security Implications of Malformed UTF-8
803 Unfortunately, the specification of UTF-8 leaves some room for
804 interpretation of how many bytes of encoded output one should generate
805 from one input Unicode character. Strictly speaking, one is supposed
806 to always generate the shortest possible sequence of UTF-8 bytes,
807 because otherwise there is potential for input buffer overflow at
808 the receiving end of a UTF-8 connection. Perl always generates the
809 shortest length UTF-8, and with warnings on (C<-w> or C<use
810 warnings;>) Perl will warn about non-shortest length UTF-8 (and other
811 malformations, too, such as the surrogates, which are not real
812 Unicode code points.)
814 =head2 Unicode in Perl on EBCDIC
816 The way Unicode is handled on EBCDIC platforms is still rather
817 experimental. On such a platform, references to UTF-8 encoding in this
818 document and elsewhere should be read as meaning UTF-EBCDIC as
819 specified in Unicode Technical Report 16 unless ASCII vs EBCDIC issues
820 are specifically discussed. There is no C<utfebcdic> pragma or
821 ":utfebcdic" layer, rather, "utf8" and ":utf8" are re-used to mean
822 the platform's "natural" 8-bit encoding of Unicode. See L<perlebcdic>
823 for more discussion of the issues.
825 =head2 Using Unicode in XS
827 If you want to handle Perl Unicode in XS extensions, you may find
828 the following C APIs useful:
834 DO_UTF8(sv) returns true if the UTF8 flag is on and the bytes
835 pragma is not in effect. SvUTF8(sv) returns true is the UTF8
836 flag is on, the bytes pragma is ignored. Remember that UTF8
837 flag being on does not mean that there would be any characters
838 of code points greater than 255 or 127 in the scalar, or that
839 there even are any characters in the scalar. The UTF8 flag
840 means that any characters added to the string will be encoded
841 in UTF8 if the code points of the characters are greater than
842 255. Not "if greater than 127", since Perl's Unicode model
843 is not to use UTF-8 until it's really necessary.
847 uvuni_to_utf8(buf, chr) writes a Unicode character code point into a
848 buffer encoding the code point as UTF-8, and returns a pointer
849 pointing after the UTF-8 bytes.
853 utf8_to_uvuni(buf, lenp) reads UTF-8 encoded bytes from a buffer and
854 returns the Unicode character code point (and optionally the length of
855 the UTF-8 byte sequence).
859 utf8_length(s, len) returns the length of the UTF-8 encoded buffer in
860 characters. sv_len_utf8(sv) returns the length of the UTF-8 encoded
865 sv_utf8_upgrade(sv) converts the string of the scalar to its UTF-8
866 encoded form. sv_utf8_downgrade(sv) does the opposite (if possible).
867 sv_utf8_encode(sv) is like sv_utf8_upgrade but the UTF8 flag does not
868 get turned on. sv_utf8_decode() does the opposite of sv_utf8_encode().
872 is_utf8_char(buf) returns true if the buffer points to valid UTF-8.
876 is_utf8_string(buf, len) returns true if the len bytes of the buffer
881 UTF8SKIP(buf) will return the number of bytes in the UTF-8 encoded
882 character in the buffer. UNISKIP(chr) will return the number of bytes
883 required to UTF-8-encode the Unicode character code point.
887 utf8_distance(a, b) will tell the distance in characters between the
888 two pointers pointing to the same UTF-8 encoded buffer.
892 utf8_hop(s, off) will return a pointer to an UTF-8 encoded buffer that
893 is C<off> (positive or negative) Unicode characters displaced from the
898 pv_uni_display(dsv, spv, len, pvlim, flags) and sv_uni_display(dsv,
899 ssv, pvlim, flags) are useful for debug output of Unicode strings and
900 scalars (only for debug: they display B<all> characters as hexadecimal
905 ibcmp_utf8(s1, u1, len1, s2, u2, len2) can be used to compare two
906 strings case-insensitively in Unicode. (For case-sensitive
907 comparisons you can just use memEQ() and memNE() as usual.)
911 For more information, see L<perlapi>, and F<utf8.c> and F<utf8.h>
912 in the Perl source code distribution.
916 L<perluniintro>, L<encoding>, L<Encode>, L<open>, L<utf8>, L<bytes>,
917 L<perlretut>, L<perlvar/"${^WIDE_SYSTEM_CALLS}">
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