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revision 868 by ph10, Fri Oct 21 09:04:01 2011 UTC revision 869 by ph10, Sat Jan 14 11:16:23 2012 UTC
# Line 13  from the original man page. If there is Line 13  from the original man page. If there is
13  man page, in case the conversion went wrong.  man page, in case the conversion went wrong.
14  <br>  <br>
15  <br><b>  <br><b>
16  UTF-8 AND UNICODE PROPERTY SUPPORT  UTF-8, UTF-16, AND UNICODE PROPERTY SUPPORT
17  </b><br>  </b><br>
18  <P>  <P>
19  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
20  the code, and, in addition, you must call  supports UTF-16 by means of a separate 16-bit library. This can be built as
21    well as, or instead of, the 8-bit library.
22    </P>
23    <br><b>
24    UTF-8 SUPPORT
25    </b><br>
26    <P>
27    In order process UTF-8 strings, you must build PCRE's 8-bit library with UTF
28    support, and, in addition, you must call
29  <a href="pcre_compile.html"><b>pcre_compile()</b></a>  <a href="pcre_compile.html"><b>pcre_compile()</b></a>
30  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
31  (*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
32  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
33  strings of 1-byte characters. PCRE does not support any other formats (in  strings of 1-byte characters.
 particular, it does not support UTF-16).  
34  </P>  </P>
35    <br><b>
36    UTF-16 SUPPORT
37    </b><br>
38  <P>  <P>
39  If you compile PCRE with UTF-8 support, but do not use it at run time, the  In order process UTF-16 strings, you must build PCRE's 16-bit library with UTF
40    support, and, in addition, you must call
41    <a href="pcre16_compile.html"><b>pcre16_compile()</b></a>
42    with the PCRE_UTF16 option flag, or the pattern must start with the sequence
43    (*UTF16). When either of these is the case, both the pattern and any subject
44    strings that are matched against it are treated as UTF-16 strings instead of
45    strings of 16-bit characters.
46    </P>
47    <br><b>
48    UTF SUPPORT OVERHEAD
49    </b><br>
50    <P>
51    If you compile PCRE with UTF support, but do not use it at run time, the
52  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
53  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.
54  </P>  </P>
55    <br><b>
56    UNICODE PROPERTY SUPPORT
57    </b><br>
58  <P>  <P>
59  If PCRE is built with Unicode character property support (which implies UTF-8  If PCRE is built with Unicode character property support (which implies UTF
60  support), the escape sequences \p{..}, \P{..}, and \X are supported.  support), the escape sequences \p{..}, \P{..}, and \X can be used.
61  The available properties that can be tested are limited to the general  The available properties that can be tested are limited to the general
62  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
63  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 47  compatibility with Perl 5.6. PCRE does n Line 72  compatibility with Perl 5.6. PCRE does n
72  Validity of UTF-8 strings  Validity of UTF-8 strings
73  </b><br>  </b><br>
74  <P>  <P>
75  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
76  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
77  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
78  themselves derived from the Unicode specification. Earlier releases of PCRE  3629, which are themselves derived from the Unicode specification. Earlier
79  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
80  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
81  U+10FFFF, excluding U+D800 to U+DFFF.  range U+0 to U+10FFFF, excluding U+D800 to U+DFFF.
82  </P>  </P>
83  <P>  <P>
84  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
85  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
86  character assignments, consequently no character code charts or namelists are  values greater than 0xFFFF. The code points that are encoded by UTF-16 pairs
87  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
88  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.)  
89  </P>  </P>
90  <P>  <P>
91  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
# Line 97  encoded in a UTF-8-like manner as per th Line 119  encoded in a UTF-8-like manner as per th
119  PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in this  PCRE_NO_UTF8_CHECK to bypass the more restrictive test. However, in this
120  situation, you will have to apply your own validity check, and avoid the use of  situation, you will have to apply your own validity check, and avoid the use of
121  JIT optimization.  JIT optimization.
122    <a name="utf16strings"></a></P>
123    <br><b>
124    Validity of UTF-16 strings
125    </b><br>
126    <P>
127    When you set the PCRE_UTF16 flag, the strings of 16-bit data units that are
128    passed as patterns and subjects are (by default) checked for validity on entry
129    to the relevant functions. Values other than those in the surrogate range
130    U+D800 to U+DFFF are independent code points. Values in the surrogate range
131    must be used in pairs in the correct manner.
132    </P>
133    <P>
134    If an invalid UTF-16 string is passed to PCRE, an error return is given. At
135    compile time, the only additional information is the offset to the first data
136    unit of the failing character. The runtime functions <b>pcre16_exec()</b> and
137    <b>pcre16_dfa_exec()</b> also pass back this information, as well as a more
138    detailed reason code if the caller has provided memory in which to do this.
139    </P>
140    <P>
141    In some situations, you may already know that your strings are valid, and
142    therefore want to skip these checks in order to improve performance. If you set
143    the PCRE_NO_UTF16_CHECK flag at compile time or at run time, PCRE assumes that
144    the pattern or subject it is given (respectively) contains only valid UTF-16
145    sequences. In this case, it does not diagnose an invalid UTF-16 string.
146  </P>  </P>
147  <br><b>  <br><b>
148  General comments about UTF-8 mode  General comments about UTF modes
149  </b><br>  </b><br>
150  <P>  <P>
151  1. An unbraced hexadecimal escape sequence (such as \xb3) matches a two-byte  1. Codepoints less than 256 can be specified by either braced or unbraced
152  UTF-8 character if the value is greater than 127.  hexadecimal escape sequences (for example, \x{b3} or \xb3). Larger values
153    have to use braced sequences.
154  </P>  </P>
155  <P>  <P>
156  2. Octal numbers up to \777 are recognized, and match two-byte UTF-8  2. Octal numbers up to \777 are recognized, and in UTF-8 mode, they match
157  characters for values greater than \177.  two-byte characters for values greater than \177.
158  </P>  </P>
159  <P>  <P>
160  3. Repeat quantifiers apply to complete UTF-8 characters, not to individual  3. Repeat quantifiers apply to complete UTF characters, not to individual
161  bytes, for example: \x{100}{3}.  data units, for example: \x{100}{3}.
162  </P>  </P>
163  <P>  <P>
164  4. The dot metacharacter matches one UTF-8 character instead of a single byte.  4. The dot metacharacter matches one UTF character instead of a single data
165    unit.
166  </P>  </P>
167  <P>  <P>
168  5. The escape sequence \C can be used to match a single byte in UTF-8 mode,  5. The escape sequence \C can be used to match a single byte in UTF-8 mode, or
169  but its use can lead to some strange effects because it breaks up multibyte  a single 16-bit data unit in UTF-16 mode, but its use can lead to some strange
170  characters (see the description of \C in the  effects because it breaks up multi-unit characters (see the description of \C
171    in the
172  <a href="pcrepattern.html"><b>pcrepattern</b></a>  <a href="pcrepattern.html"><b>pcrepattern</b></a>
173  documentation). The use of \C is not supported in the alternative matching  documentation). The use of \C is not supported in the alternative matching
174  function <b>pcre_dfa_exec()</b>, nor is it supported in UTF-8 mode by the JIT  function <b>pcre[16]_dfa_exec()</b>, nor is it supported in UTF mode by the JIT
175  optimization of <b>pcre_exec()</b>. If JIT optimization is requested for a UTF-8  optimization of <b>pcre[16]_exec()</b>. If JIT optimization is requested for a
176  pattern that contains \C, it will not succeed, and so the matching will be  UTF pattern that contains \C, it will not succeed, and so the matching will
177  carried out by the normal interpretive function.  be carried out by the normal interpretive function.
178  </P>  </P>
179  <P>  <P>
180  6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly  6. The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly
181  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
182  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
183  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
184  include Unicode property support, because to do otherwise would slow down PCRE  is built to include Unicode property support, because to do otherwise would
185  in many common cases. Note in particular that this applies to \b and \B,  slow down PCRE in many common cases. Note in particular that this applies to
186  because they are defined in terms of \w and \W. If you really want to test  \b and \B, because they are defined in terms of \w and \W. If you really
187  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
188  such as \p{Nd}. Alternatively, if you set the PCRE_UCP option, the way that  property tests such as \p{Nd}. Alternatively, if you set the PCRE_UCP option,
189  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
190  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
191    section on
192  <a href="pcrepattern.html#genericchartypes">generic character types</a>  <a href="pcrepattern.html#genericchartypes">generic character types</a>
193  in the  in the
194  <a href="pcrepattern.html"><b>pcrepattern</b></a>  <a href="pcrepattern.html"><b>pcrepattern</b></a>
# Line 178  Cambridge CB2 3QH, England. Line 228  Cambridge CB2 3QH, England.
228  REVISION  REVISION
229  </b><br>  </b><br>
230  <P>  <P>
231  Last updated: 19 October 2011  Last updated: 13 January 2012
232  <br>  <br>
233  Copyright &copy; 1997-2011 University of Cambridge.  Copyright &copy; 1997-2012 University of Cambridge.
234  <br>  <br>
235  <p>  <p>
236  Return to the <a href="index.html">PCRE index page</a>.  Return to the <a href="index.html">PCRE index page</a>.

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