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revision 867 by ph10, Wed Oct 19 17:37:29 2011 UTC revision 868 by ph10, Fri Jan 13 17:16:32 2012 UTC
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1  .TH PCREUNICODE 3  .TH PCREUNICODE 3
2  .SH NAME  .SH NAME
3  PCRE - Perl-compatible regular expressions  PCRE - Perl-compatible regular expressions
4  .SH "UTF-8 AND UNICODE PROPERTY SUPPORT"  .SH "UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT"
5  .rs  .rs
6  .sp  .sp
7  In order process UTF-8 strings, you must build PCRE to include UTF-8 support in  From Release 8.30, in addition to its previous UTF-8 support, PCRE also
8  the code, and, in addition, you must call  supports UTF-16 by means of a separate 16-bit library. This can be built as
9    well as, or instead of, the 8-bit library.
10    .
11    .
12    .SH "UTF-8 SUPPORT"
13    .rs
14    .sp
15    In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF
16    support, and, in addition, you must call
17  .\" HREF  .\" HREF
18  \fBpcre_compile()\fP  \fBpcre_compile()\fP
19  .\"  .\"
20  with the PCRE_UTF8 option flag, or the pattern must start with the sequence  with the PCRE_UTF8 option flag, or the pattern must start with the sequence
21  (*UTF8). When either of these is the case, both the pattern and any subject  (*UTF8). When either of these is the case, both the pattern and any subject
22  strings that are matched against it are treated as UTF-8 strings instead of  strings that are matched against it are treated as UTF-8 strings instead of
23  strings of 1-byte characters. PCRE does not support any other formats (in  strings of 1-byte characters.
24  particular, it does not support UTF-16).  .
25  .P  .
26  If you compile PCRE with UTF-8 support, but do not use it at run time, the  .SH "UTF-16 SUPPORT"
27    .rs
28    .sp
29    In order process UTF-16 strings, you must build PCRE's 16-bit library with UTF
30    support, and, in addition, you must call
31    .\" HREF
32    \fBpcre16_compile()\fP
33    .\"
34    with the PCRE_UTF16 option flag, or the pattern must start with the sequence
35    (*UTF16). When either of these is the case, both the pattern and any subject
36    strings that are matched against it are treated as UTF-16 strings instead of
37    strings of 16-bit characters.
38    .
39    .
40    .SH "UTF SUPPORT OVERHEAD"
41    .rs
42    .sp
43    If you compile PCRE with UTF support, but do not use it at run time, the
44  library will be a bit bigger, but the additional run time overhead is limited  library will be a bit bigger, but the additional run time overhead is limited
45  to testing the PCRE_UTF8 flag occasionally, so should not be very big.  to testing the PCRE_UTF8/16 flag occasionally, so should not be very big.
46  .P  .
47  If PCRE is built with Unicode character property support (which implies UTF-8  .
48  support), the escape sequences \ep{..}, \eP{..}, and \eX are supported.  .SH "UNICODE PROPERTY SUPPORT"
49    .rs
50    .sp
51    If PCRE is built with Unicode character property support (which implies UTF
52    support), the escape sequences \ep{..}, \eP{..}, and \eX can be used.
53  The available properties that can be tested are limited to the general  The available properties that can be tested are limited to the general
54  category properties such as Lu for an upper case letter or Nd for a decimal  category properties such as Lu for an upper case letter or Nd for a decimal
55  number, the Unicode script names such as Arabic or Han, and the derived  number, the Unicode script names such as Arabic or Han, and the derived
# Line 38  compatibility with Perl 5.6. PCRE does n Line 67  compatibility with Perl 5.6. PCRE does n
67  .SS "Validity of UTF-8 strings"  .SS "Validity of UTF-8 strings"
68  .rs  .rs
69  .sp  .sp
70  When you set the PCRE_UTF8 flag, the strings passed as patterns and subjects  When you set the PCRE_UTF8 flag, the byte strings passed as patterns and
71  are (by default) checked for validity on entry to the relevant functions. From  subjects are (by default) checked for validity on entry to the relevant
72  release 7.3 of PCRE, the check is according the rules of RFC 3629, which are  functions. From release 7.3 of PCRE, the check is according the rules of RFC
73  themselves derived from the Unicode specification. Earlier releases of PCRE  3629, which are themselves derived from the Unicode specification. Earlier
74  followed the rules of RFC 2279, which allows the full range of 31-bit values (0  releases of PCRE followed the rules of RFC 2279, which allows the full range of
75  to 0x7FFFFFFF). The current check allows only values in the range U+0 to  31-bit values (0 to 0x7FFFFFFF). The current check allows only values in the
76  U+10FFFF, excluding U+D800 to U+DFFF.  range U+0 to U+10FFFF, excluding U+D800 to U+DFFF.
77  .P  .P
78  The excluded code points are the "Low Surrogate Area" of Unicode, of which the  The excluded code points are the "Surrogate Area" of Unicode. They are reserved
79  Unicode Standard says this: "The Low Surrogate Area does not contain any  for use by UTF-16, where they are used in pairs to encode codepoints with
80  character assignments, consequently no character code charts or namelists are  values greater than 0xFFFF. The code points that are encoded by UTF-16 pairs
81  provided for this area. Surrogates are reserved for use with UTF-16 and then  are available independently in the UTF-8 encoding. (In other words, the whole
82  must be used in pairs." The code points that are encoded by UTF-16 pairs are  surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8.)
 available as independent code points in the UTF-8 encoding. (In other words,  
 the whole surrogate thing is a fudge for UTF-16 which unfortunately messes up  
 UTF-8.)  
83  .P  .P
84  If an invalid UTF-8 string is passed to PCRE, an error return is given. At  If an invalid UTF-8 string is passed to PCRE, an error return is given. At
85  compile time, the only additional information is the offset to the first byte  compile time, the only additional information is the offset to the first byte
# Line 85  situation, you will have to apply your o Line 111  situation, you will have to apply your o
111  JIT optimization.  JIT optimization.
112  .  .
113  .  .
114  .SS "General comments about UTF-8 mode"  .\" HTML <a name="utf16strings"></a>
115    .SS "Validity of UTF-16 strings"
116  .rs  .rs
117  .sp  .sp
118  1. An unbraced hexadecimal escape sequence (such as \exb3) matches a two-byte  When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are
119  UTF-8 character if the value is greater than 127.  passed as patterns and subjects are (by default) checked for validity on entry
120  .P  to the relevant functions. Values other than those in the surrogate range
121  2. Octal numbers up to \e777 are recognized, and match two-byte UTF-8  U+D800 to U+DFFF are independent code points. Values in the surrogate range
122  characters for values greater than \e177.  must be used in pairs in the correct manner.
123  .P  .P
124  3. Repeat quantifiers apply to complete UTF-8 characters, not to individual  If an invalid UTF-16 string is passed to PCRE, an error return is given. At
125  bytes, for example: \ex{100}{3}.  compile time, the only additional information is the offset to the first data
126  .P  unit of the failing character. The runtime functions \fBpcre16_exec()\fP and
127  4. The dot metacharacter matches one UTF-8 character instead of a single byte.  \fBpcre16_dfa_exec()\fP also pass back this information, as well as a more
128    detailed reason code if the caller has provided memory in which to do this.
129  .P  .P
130  5. The escape sequence \eC can be used to match a single byte in UTF-8 mode,  In some situations, you may already know that your strings are valid, and
131  but its use can lead to some strange effects because it breaks up multibyte  therefore want to skip these checks in order to improve performance. If you set
132  characters (see the description of \eC in the  the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that
133    the pattern or subject it is given (respectively) contains only valid UTF-16
134    sequences. In this case, it does not diagnose an invalid UTF-16 string.
135    .
136    .
137    .SS "General comments about UTF modes"
138    .rs
139    .sp
140    1. Codepoints less than 256 can be specified by either braced or unbraced
141    hexadecimal escape sequences (for example, \ex{b3} or \exb3). Larger values
142    have to use braced sequences.
143    .P
144    2. Octal numbers up to \e777 are recognized, and in UTF-8 mode, they match
145    two-byte characters for values greater than \e177.
146    .P
147    3. Repeat quantifiers apply to complete UTF characters, not to individual
148    data units, for example: \ex{100}{3}.
149    .P
150    4. The dot metacharacter matches one UTF character instead of a single data
151    unit.
152    .P
153    5. The escape sequence \eC can be used to match a single byte in UTF-8 mode, or
154    a single 16-bit data unit in UTF-16 mode, but its use can lead to some strange
155    effects because it breaks up multi-unit characters (see the description of \eC
156    in the
157  .\" HREF  .\" HREF
158  \fBpcrepattern\fP  \fBpcrepattern\fP
159  .\"  .\"
160  documentation). The use of \eC is not supported in the alternative matching  documentation). The use of \eC is not supported in the alternative matching
161  function \fBpcre_dfa_exec()\fP, nor is it supported in UTF-8 mode by the JIT  function \fBpcre[16]_dfa_exec()\fP, nor is it supported in UTF mode by the JIT
162  optimization of \fBpcre_exec()\fP. If JIT optimization is requested for a UTF-8  optimization of \fBpcre[16]_exec()\fP. If JIT optimization is requested for a
163  pattern that contains \eC, it will not succeed, and so the matching will be  UTF pattern that contains \eC, it will not succeed, and so the matching will
164  carried out by the normal interpretive function.  be carried out by the normal interpretive function.
165  .P  .P
166  6. The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly  6. The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly
167  test characters of any code value, but, by default, the characters that PCRE  test characters of any code value, but, by default, the characters that PCRE
168  recognizes as digits, spaces, or word characters remain the same set as before,  recognizes as digits, spaces, or word characters remain the same set as in
169  all with values less than 256. This remains true even when PCRE is built to  non-UTF mode, all with values less than 256. This remains true even when PCRE
170  include Unicode property support, because to do otherwise would slow down PCRE  is built to include Unicode property support, because to do otherwise would
171  in many common cases. Note in particular that this applies to \eb and \eB,  slow down PCRE in many common cases. Note in particular that this applies to
172  because they are defined in terms of \ew and \eW. If you really want to test  \eb and \eB, because they are defined in terms of \ew and \eW. If you really
173  for a wider sense of, say, "digit", you can use explicit Unicode property tests  want to test for a wider sense of, say, "digit", you can use explicit Unicode
174  such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option, the way that  property tests such as \ep{Nd}. Alternatively, if you set the PCRE_UCP option,
175  the character escapes work is changed so that Unicode properties are used to  the way that the character escapes work is changed so that Unicode properties
176  determine which characters match. There are more details in the section on  are used to determine which characters match. There are more details in the
177    section on
178  .\" HTML <a href="pcrepattern.html#genericchartypes">  .\" HTML <a href="pcrepattern.html#genericchartypes">
179  .\" </a>  .\" </a>
180  generic character types  generic character types
# Line 163  Cambridge CB2 3QH, England. Line 216  Cambridge CB2 3QH, England.
216  .rs  .rs
217  .sp  .sp
218  .nf  .nf
219  Last updated: 19 October 2011  Last updated: 13 January 2012
220  Copyright (c) 1997-2011 University of Cambridge.  Copyright (c) 1997-2012 University of Cambridge.
221  .fi  .fi
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