2014-09-23 13:35:51 +02:00
|
|
|
<html>
|
|
|
|
|
<head>
|
|
|
|
|
<title>pcre2unicode specification</title>
|
|
|
|
|
</head>
|
|
|
|
|
<body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
|
|
|
|
|
<h1>pcre2unicode man page</h1>
|
|
|
|
|
<p>
|
|
|
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
|
|
|
</p>
|
|
|
|
|
<p>
|
|
|
|
|
This page is part of the PCRE2 HTML documentation. It was generated
|
|
|
|
|
automatically from the original man page. If there is any nonsense in it,
|
|
|
|
|
please consult the man page, in case the conversion went wrong.
|
|
|
|
|
<br>
|
|
|
|
|
<br><b>
|
|
|
|
|
UNICODE AND UTF SUPPORT
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
2014-11-03 19:27:56 +01:00
|
|
|
When PCRE2 is built with Unicode support (which is the default), it has
|
|
|
|
|
knowledge of Unicode character properties and can process text strings in
|
|
|
|
|
UTF-8, UTF-16, or UTF-32 format (depending on the code unit width). However, by
|
|
|
|
|
default, PCRE2 assumes that one code unit is one character. To process a
|
|
|
|
|
pattern as a UTF string, where a character may require more than one code unit,
|
|
|
|
|
you must call
|
2014-09-23 13:35:51 +02:00
|
|
|
<a href="pcre2_compile.html"><b>pcre2_compile()</b></a>
|
|
|
|
|
with the PCRE2_UTF option flag, or the pattern must start with the sequence
|
|
|
|
|
(*UTF). When either of these is the case, both the pattern and any subject
|
|
|
|
|
strings that are matched against it are treated as UTF strings instead of
|
|
|
|
|
strings of individual one-code-unit characters.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2014-11-03 19:27:56 +01:00
|
|
|
If you do not need Unicode support you can build PCRE2 without it, in which
|
|
|
|
|
case the library will be smaller.
|
2014-09-23 13:35:51 +02:00
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
UNICODE PROPERTY SUPPORT
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
When PCRE2 is built with Unicode support, the escape sequences \p{..},
|
|
|
|
|
\P{..}, and \X can be used. The Unicode properties that can be tested are
|
|
|
|
|
limited to the general category properties such as Lu for an upper case letter
|
|
|
|
|
or Nd for a decimal number, the Unicode script names such as Arabic or Han, and
|
|
|
|
|
the derived properties Any and L&. Full lists are given in the
|
|
|
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
|
|
|
and
|
|
|
|
|
<a href="pcre2syntax.html"><b>pcre2syntax</b></a>
|
|
|
|
|
documentation. Only the short names for properties are supported. For example,
|
|
|
|
|
\p{L} matches a letter. Its Perl synonym, \p{Letter}, is not supported.
|
|
|
|
|
Furthermore, in Perl, many properties may optionally be prefixed by "Is", for
|
|
|
|
|
compatibility with Perl 5.6. PCRE does not support this.
|
|
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
WIDE CHARACTERS AND UTF MODES
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
Codepoints less than 256 can be specified in patterns by either braced or
|
|
|
|
|
unbraced hexadecimal escape sequences (for example, \x{b3} or \xb3). Larger
|
|
|
|
|
values have to use braced sequences. Unbraced octal code points up to \777 are
|
|
|
|
|
also recognized; larger ones can be coded using \o{...}.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
In UTF modes, repeat quantifiers apply to complete UTF characters, not to
|
|
|
|
|
individual code units.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
In UTF modes, the dot metacharacter matches one UTF character instead of a
|
|
|
|
|
single code unit.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2014-10-20 19:28:49 +02:00
|
|
|
The escape sequence \C can be used to match a single code unit, in a UTF mode,
|
2014-09-23 13:35:51 +02:00
|
|
|
but its use can lead to some strange effects because it breaks up multi-unit
|
|
|
|
|
characters (see the description of \C in the
|
|
|
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
|
2015-10-17 15:50:56 +02:00
|
|
|
documentation). The use of \C is not supported by the alternative matching
|
|
|
|
|
function <b>pcre2_dfa_match()</b> when in UTF mode. Its use provokes a
|
|
|
|
|
match-time error. The JIT optimization also does not support \C in UTF mode.
|
|
|
|
|
If JIT optimization is requested for a UTF pattern that contains \C, it will
|
|
|
|
|
not succeed, and so the matching will be carried out by the normal interpretive
|
|
|
|
|
function.
|
2014-09-23 13:35:51 +02:00
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly test
|
|
|
|
|
characters of any code value, but, by default, the characters that PCRE2
|
|
|
|
|
recognizes as digits, spaces, or word characters remain the same set as in
|
|
|
|
|
non-UTF mode, all with code points less than 256. This remains true even when
|
|
|
|
|
PCRE2 is built to include Unicode support, because to do otherwise would slow
|
|
|
|
|
down matching in many common cases. Note that this also applies to \b
|
|
|
|
|
and \B, because they are defined in terms of \w and \W. If you want
|
|
|
|
|
to test for a wider sense of, say, "digit", you can use explicit Unicode
|
|
|
|
|
property tests such as \p{Nd}. Alternatively, if you set the PCRE2_UCP option,
|
|
|
|
|
the way that the character escapes work is changed so that Unicode properties
|
|
|
|
|
are used to determine which characters match. There are more details in the
|
|
|
|
|
section on
|
|
|
|
|
<a href="pcre2pattern.html#genericchartypes">generic character types</a>
|
|
|
|
|
in the
|
|
|
|
|
<a href="pcre2pattern.html"><b>pcre2pattern</b></a>
|
|
|
|
|
documentation.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
Similarly, characters that match the POSIX named character classes are all
|
|
|
|
|
low-valued characters, unless the PCRE2_UCP option is set.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
However, the special horizontal and vertical white space matching escapes (\h,
|
|
|
|
|
\H, \v, and \V) do match all the appropriate Unicode characters, whether or
|
|
|
|
|
not PCRE2_UCP is set.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
Case-insensitive matching in UTF mode makes use of Unicode properties. A few
|
|
|
|
|
Unicode characters such as Greek sigma have more than two codepoints that are
|
|
|
|
|
case-equivalent, and these are treated as such.
|
|
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
VALIDITY OF UTF STRINGS
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
When the PCRE2_UTF option is set, the strings passed as patterns and subjects
|
2014-10-20 19:28:49 +02:00
|
|
|
are (by default) checked for validity on entry to the relevant functions.
|
2014-11-24 16:31:28 +01:00
|
|
|
If an invalid UTF string is passed, an negative error code is returned. The
|
|
|
|
|
code unit offset to the offending character can be extracted from the match
|
|
|
|
|
data block by calling <b>pcre2_get_startchar()</b>, which is used for this
|
|
|
|
|
purpose after a UTF error.
|
2014-09-23 13:35:51 +02:00
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
UTF-16 and UTF-32 strings can indicate their endianness by special code knows
|
|
|
|
|
as a byte-order mark (BOM). The PCRE2 functions do not handle this, expecting
|
|
|
|
|
strings to be in host byte order.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
2015-08-30 19:47:36 +02:00
|
|
|
A UTF string is checked before any other processing takes place. In the case of
|
|
|
|
|
<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b> calls with a non-zero starting
|
|
|
|
|
offset, the check is applied only to that part of the subject that could be
|
|
|
|
|
inspected during matching, and there is a check that the starting offset points
|
|
|
|
|
to the first code unit of a character or to the end of the subject. If there
|
|
|
|
|
are no lookbehind assertions in the pattern, the check starts at the starting
|
|
|
|
|
offset. Otherwise, it starts at the length of the longest lookbehind before the
|
|
|
|
|
starting offset, or at the start of the subject if there are not that many
|
|
|
|
|
characters before the starting offset. Note that the sequences \b and \B are
|
|
|
|
|
one-character lookbehinds.
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
In addition to checking the format of the string, there is a check to ensure
|
|
|
|
|
that all code points lie in the range U+0 to U+10FFFF, excluding the surrogate
|
|
|
|
|
area. The so-called "non-character" code points are not excluded because
|
|
|
|
|
Unicode corrigendum #9 makes it clear that they should not be.
|
2014-09-23 13:35:51 +02:00
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
Characters in the "Surrogate Area" of Unicode are reserved for use by UTF-16,
|
|
|
|
|
where they are used in pairs to encode code points with values greater than
|
|
|
|
|
0xFFFF. The code points that are encoded by UTF-16 pairs are available
|
|
|
|
|
independently in the UTF-8 and UTF-32 encodings. (In other words, the whole
|
|
|
|
|
surrogate thing is a fudge for UTF-16 which unfortunately messes up UTF-8 and
|
|
|
|
|
UTF-32.)
|
|
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
In some situations, you may already know that your strings are valid, and
|
|
|
|
|
therefore want to skip these checks in order to improve performance, for
|
|
|
|
|
example in the case of a long subject string that is being scanned repeatedly.
|
2014-11-23 19:38:38 +01:00
|
|
|
If you set the PCRE2_NO_UTF_CHECK option at compile time or at match time,
|
|
|
|
|
PCRE2 assumes that the pattern or subject it is given (respectively) contains
|
|
|
|
|
only valid UTF code unit sequences.
|
2014-09-23 13:35:51 +02:00
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
Passing PCRE2_NO_UTF_CHECK to <b>pcre2_compile()</b> just disables the check for
|
|
|
|
|
the pattern; it does not also apply to subject strings. If you want to disable
|
2014-11-23 19:38:38 +01:00
|
|
|
the check for a subject string you must pass this option to <b>pcre2_match()</b>
|
|
|
|
|
or <b>pcre2_dfa_match()</b>.
|
2014-09-23 13:35:51 +02:00
|
|
|
</P>
|
|
|
|
|
<P>
|
|
|
|
|
If you pass an invalid UTF string when PCRE2_NO_UTF_CHECK is set, the result
|
|
|
|
|
is undefined and your program may crash or loop indefinitely.
|
|
|
|
|
<a name="utf8strings"></a></P>
|
|
|
|
|
<br><b>
|
|
|
|
|
Errors in UTF-8 strings
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
The following negative error codes are given for invalid UTF-8 strings:
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR1
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR2
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR3
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR4
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR5
|
|
|
|
|
</pre>
|
|
|
|
|
The string ends with a truncated UTF-8 character; the code specifies how many
|
|
|
|
|
bytes are missing (1 to 5). Although RFC 3629 restricts UTF-8 characters to be
|
|
|
|
|
no longer than 4 bytes, the encoding scheme (originally defined by RFC 2279)
|
|
|
|
|
allows for up to 6 bytes, and this is checked first; hence the possibility of
|
|
|
|
|
4 or 5 missing bytes.
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR6
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR7
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR8
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR9
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR10
|
|
|
|
|
</pre>
|
|
|
|
|
The two most significant bits of the 2nd, 3rd, 4th, 5th, or 6th byte of the
|
|
|
|
|
character do not have the binary value 0b10 (that is, either the most
|
|
|
|
|
significant bit is 0, or the next bit is 1).
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR11
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR12
|
|
|
|
|
</pre>
|
|
|
|
|
A character that is valid by the RFC 2279 rules is either 5 or 6 bytes long;
|
|
|
|
|
these code points are excluded by RFC 3629.
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR13
|
|
|
|
|
</pre>
|
|
|
|
|
A 4-byte character has a value greater than 0x10fff; these code points are
|
|
|
|
|
excluded by RFC 3629.
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR14
|
|
|
|
|
</pre>
|
|
|
|
|
A 3-byte character has a value in the range 0xd800 to 0xdfff; this range of
|
|
|
|
|
code points are reserved by RFC 3629 for use with UTF-16, and so are excluded
|
|
|
|
|
from UTF-8.
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR15
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR16
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR17
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR18
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR19
|
|
|
|
|
</pre>
|
|
|
|
|
A 2-, 3-, 4-, 5-, or 6-byte character is "overlong", that is, it codes for a
|
|
|
|
|
value that can be represented by fewer bytes, which is invalid. For example,
|
|
|
|
|
the two bytes 0xc0, 0xae give the value 0x2e, whose correct coding uses just
|
|
|
|
|
one byte.
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR20
|
|
|
|
|
</pre>
|
|
|
|
|
The two most significant bits of the first byte of a character have the binary
|
|
|
|
|
value 0b10 (that is, the most significant bit is 1 and the second is 0). Such a
|
|
|
|
|
byte can only validly occur as the second or subsequent byte of a multi-byte
|
|
|
|
|
character.
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE2_ERROR_UTF8_ERR21
|
|
|
|
|
</pre>
|
|
|
|
|
The first byte of a character has the value 0xfe or 0xff. These values can
|
|
|
|
|
never occur in a valid UTF-8 string.
|
|
|
|
|
<a name="utf16strings"></a></P>
|
|
|
|
|
<br><b>
|
|
|
|
|
Errors in UTF-16 strings
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
The following negative error codes are given for invalid UTF-16 strings:
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE_UTF16_ERR1 Missing low surrogate at end of string
|
|
|
|
|
PCRE_UTF16_ERR2 Invalid low surrogate follows high surrogate
|
|
|
|
|
PCRE_UTF16_ERR3 Isolated low surrogate
|
|
|
|
|
|
|
|
|
|
<a name="utf32strings"></a></PRE>
|
|
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
Errors in UTF-32 strings
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
The following negative error codes are given for invalid UTF-32 strings:
|
|
|
|
|
<pre>
|
|
|
|
|
PCRE_UTF32_ERR1 Surrogate character (range from 0xd800 to 0xdfff)
|
|
|
|
|
PCRE_UTF32_ERR2 Code point is greater than 0x10ffff
|
|
|
|
|
|
|
|
|
|
</PRE>
|
|
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
AUTHOR
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
|
|
|
|
Philip Hazel
|
|
|
|
|
<br>
|
|
|
|
|
University Computing Service
|
|
|
|
|
<br>
|
2014-11-21 17:45:06 +01:00
|
|
|
Cambridge, England.
|
2014-09-23 13:35:51 +02:00
|
|
|
<br>
|
|
|
|
|
</P>
|
|
|
|
|
<br><b>
|
|
|
|
|
REVISION
|
|
|
|
|
</b><br>
|
|
|
|
|
<P>
|
2015-10-17 15:50:56 +02:00
|
|
|
Last updated: 16 October 2015
|
2014-09-23 13:35:51 +02:00
|
|
|
<br>
|
2015-08-30 19:47:36 +02:00
|
|
|
Copyright © 1997-2015 University of Cambridge.
|
2014-09-23 13:35:51 +02:00
|
|
|
<br>
|
|
|
|
|
<p>
|
|
|
|
|
Return to the <a href="index.html">PCRE2 index page</a>.
|
|
|
|
|
</p>
|
