diff options
| author | ph10 <ph10@6239d852-aaf2-0410-a92c-79f79f948069> | 2019-05-24 17:15:48 +0000 |
|---|---|---|
| committer | ph10 <ph10@6239d852-aaf2-0410-a92c-79f79f948069> | 2019-05-24 17:15:48 +0000 |
| commit | be0b8eba4f57f4572a6744cc534081fc7249386d (patch) | |
| tree | cf4eb5c8740d93c022457fd7628f3fb3f152e29b /doc | |
| parent | d45c1c6b2ee61449c2e574f4e2ef598846bdf851 (diff) | |
| download | pcre2-be0b8eba4f57f4572a6744cc534081fc7249386d.tar.gz | |
Implement support for invalid UTF in the pcre2_match() interpreter.
git-svn-id: svn://vcs.exim.org/pcre2/code/trunk@1094 6239d852-aaf2-0410-a92c-79f79f948069
Diffstat (limited to 'doc')
| -rw-r--r-- | doc/html/pcre2_compile.html | 1 | ||||
| -rw-r--r-- | doc/html/pcre2_jit_compile.html | 6 | ||||
| -rw-r--r-- | doc/html/pcre2api.html | 69 | ||||
| -rw-r--r-- | doc/html/pcre2jit.html | 44 | ||||
| -rw-r--r-- | doc/html/pcre2matching.html | 11 | ||||
| -rw-r--r-- | doc/html/pcre2pattern.html | 23 | ||||
| -rw-r--r-- | doc/html/pcre2test.html | 3 | ||||
| -rw-r--r-- | doc/html/pcre2unicode.html | 132 | ||||
| -rw-r--r-- | doc/pcre2.txt | 2997 | ||||
| -rw-r--r-- | doc/pcre2_compile.3 | 3 | ||||
| -rw-r--r-- | doc/pcre2_jit_compile.3 | 7 | ||||
| -rw-r--r-- | doc/pcre2api.3 | 74 | ||||
| -rw-r--r-- | doc/pcre2jit.3 | 40 | ||||
| -rw-r--r-- | doc/pcre2matching.3 | 12 | ||||
| -rw-r--r-- | doc/pcre2pattern.3 | 25 | ||||
| -rw-r--r-- | doc/pcre2test.1 | 5 | ||||
| -rw-r--r-- | doc/pcre2test.txt | 3 | ||||
| -rw-r--r-- | doc/pcre2unicode.3 | 129 |
18 files changed, 1932 insertions, 1652 deletions
diff --git a/doc/html/pcre2_compile.html b/doc/html/pcre2_compile.html index 23f75e1..d865fb3 100644 --- a/doc/html/pcre2_compile.html +++ b/doc/html/pcre2_compile.html @@ -65,6 +65,7 @@ The option bits are: PCRE2_EXTENDED Ignore white space and # comments PCRE2_FIRSTLINE Force matching to be before newline PCRE2_LITERAL Pattern characters are all literal + PCRE2_MATCH_INVALID_UTF Enable support for matching invalid UTF PCRE2_MATCH_UNSET_BACKREF Match unset backreferences PCRE2_MULTILINE ^ and $ match newlines within data PCRE2_NEVER_BACKSLASH_C Lock out the use of \C in patterns diff --git a/doc/html/pcre2_jit_compile.html b/doc/html/pcre2_jit_compile.html index bbaa82c..e52fb65 100644 --- a/doc/html/pcre2_jit_compile.html +++ b/doc/html/pcre2_jit_compile.html @@ -40,8 +40,12 @@ bits: PCRE2_JIT_COMPLETE compile code for full matching PCRE2_JIT_PARTIAL_SOFT compile code for soft partial matching PCRE2_JIT_PARTIAL_HARD compile code for hard partial matching - PCRE2_JIT_INVALID_UTF compile code to handle invalid UTF </pre> +There is also an obsolete option called PCRE2_JIT_INVALID_UTF, which has been +superseded by the <b>pcre2_compile()</b> option PCRE2_MATCH_INVALID_UTF. The old +option is deprecated and may be removed in future. +</P> +<P> The yield of the function is 0 for success, or a negative error code otherwise. In particular, PCRE2_ERROR_JIT_BADOPTION is returned if JIT is not supported or if an unknown bit is set in <i>options</i>. diff --git a/doc/html/pcre2api.html b/doc/html/pcre2api.html index 7ca39f5..345a7da 100644 --- a/doc/html/pcre2api.html +++ b/doc/html/pcre2api.html @@ -1347,11 +1347,12 @@ and <b>pcre2_compile()</b> returns a non-NULL value. <P> There are nearly 100 positive error codes that <b>pcre2_compile()</b> may return if it finds an error in the pattern. There are also some negative error codes -that are used for invalid UTF strings. These are the same as given by -<b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and are described in the +that are used for invalid UTF strings when validity checking is in force. These +are the same as given by <b>pcre2_match()</b> and <b>pcre2_dfa_match()</b>, and +are described in the <a href="pcre2unicode.html"><b>pcre2unicode</b></a> -page. There is no separate documentation for the positive error codes, because -the textual error messages that are obtained by calling the +documentation. There is no separate documentation for the positive error codes, +because the textual error messages that are obtained by calling the <b>pcre2_get_error_message()</b> function (see "Obtaining a textual error message" <a href="#geterrormessage">below)</a> @@ -1615,10 +1616,18 @@ expression engine is not the most efficient way of doing it. If you are doing a lot of literal matching and are worried about efficiency, you should consider using other approaches. The only other main options that are allowed with PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, -PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, -PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE -and PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an -error. +PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_MATCH_INVALID_UTF, +PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, PCRE2_UTF, and +PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE and +PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an error. +<pre> + PCRE2_MATCH_INVALID_UTF +</pre> +This option forces PCRE2_UTF (see below) and also enables support for matching +by <b>pcre2_match()</b> in subject strings that contain invalid UTF sequences. +This facility is not supported for DFA matching. For details, see the +<a href="pcre2unicode.html"><b>pcre2unicode</b></a> +documentation. <pre> PCRE2_MATCH_UNSET_BACKREF </pre> @@ -2653,15 +2662,22 @@ of JIT; it forces matching to be done by the interpreter. PCRE2_NO_UTF_CHECK </pre> When PCRE2_UTF is set at compile time, the validity of the subject as a UTF -string is checked by default when <b>pcre2_match()</b> is subsequently called. -If a non-zero starting offset is given, 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. +string is checked unless PCRE2_NO_UTF_CHECK is passed to <b>pcre2_match()</b> or +PCRE2_MATCH_INVALID_UTF was passed to <b>pcre2_compile()</b>. The latter special +case is discussed in detail in the +<a href="pcre2unicode.html"><b>pcre2unicode</b></a> +documentation. +</P> +<P> +In the default case, if a non-zero starting offset is given, 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> The check is carried out before any other processing takes place, and a @@ -2674,19 +2690,20 @@ and <a href="pcre2unicode.html#utf32strings">UTF-32 strings</a> in the <a href="pcre2unicode.html"><b>pcre2unicode</b></a> -page. +documentation. </P> <P> -If you know that your subject is valid, and you want to skip these checks for +If you know that your subject is valid, and you want to skip this check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling <b>pcre2_match()</b>. You might want to do this for the second and subsequent -calls to <b>pcre2_match()</b> if you are making repeated calls to find other +calls to <b>pcre2_match()</b> if you are making repeated calls to find multiple matches in the same subject string. </P> <P> -<b>Warning:</b> When PCRE2_NO_UTF_CHECK is set, the effect of passing an invalid +<b>Warning:</b> Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when +PCRE2_NO_UTF_CHECK is set at match time the effect of passing an invalid string as a subject, or an invalid value of <i>startoffset</i>, is undefined. -Your program may crash or loop indefinitely. +Your program may crash or loop indefinitely or give wrong results. <pre> PCRE2_PARTIAL_HARD PCRE2_PARTIAL_SOFT @@ -3772,6 +3789,12 @@ This return is given if <b>pcre2_dfa_match()</b> encounters a condition item that uses a backreference for the condition, or a test for recursion in a specific capture group. These are not supported. <pre> + PCRE2_ERROR_DFA_UINVALID_UTF +</pre> +This return is given if <b>pcre2_dfa_match()</b> is called for a pattern that +was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for DFA +matching. +<pre> PCRE2_ERROR_DFA_WSSIZE </pre> This return is given if <b>pcre2_dfa_match()</b> runs out of space in the @@ -3808,7 +3831,7 @@ Cambridge, England. </P> <br><a name="SEC42" href="#TOC1">REVISION</a><br> <P> -Last updated: 14 February 2019 +Last updated: 23 May 2019 <br> Copyright © 1997-2019 University of Cambridge. <br> diff --git a/doc/html/pcre2jit.html b/doc/html/pcre2jit.html index cb4eb88..47b588e 100644 --- a/doc/html/pcre2jit.html +++ b/doc/html/pcre2jit.html @@ -147,25 +147,29 @@ pattern. </P> <br><a name="SEC4" href="#TOC1">MATCHING SUBJECTS CONTAINING INVALID UTF</a><br> <P> -When a pattern is compiled with the PCRE2_UTF option, the interpretive matching -function expects its subject string to be a valid sequence of UTF code units. -If it is not, the result is undefined. This is also true by default of matching -via JIT. However, if the option PCRE2_JIT_INVALID_UTF is passed to -<b>pcre2_jit_compile()</b>, code that can process a subject containing invalid -UTF is compiled. -</P> -<P> -In this mode, an invalid code unit sequence never matches any pattern item. It -does not match dot, it does not match \p{Any}, it does not even match negative -items such as [^X]. A lookbehind assertion fails if it encounters an invalid -sequence while moving the current point backwards. In other words, an invalid -UTF code unit sequence acts as a barrier which no match can cross. Reaching an -invalid sequence causes an immediate backtrack. -</P> -<P> -Using this option, an application can run matches in arbitrary data, knowing -that any matched strings that are returned will be valid UTF. This can be -useful when searching for text in executable or other binary files. +When a pattern is compiled with the PCRE2_UTF option, subject strings are +normally expected to be a valid sequence of UTF code units. By default, this is +checked at the start of matching and an error is generated if invalid UTF is +detected. The PCRE2_NO_UTF_CHECK option can be passed to <b>pcre2_match()</b> to +skip the check (for improved performance) if you are sure that a subject string +is valid. If this option is used with an invalid string, the result is +undefined. +</P> +<P> +However, a way of running matches on strings that may contain invalid UTF +sequences is available. Calling <b>pcre2_compile()</b> with the +PCRE2_MATCH_INVALID_UTF option has two effects: it tells the interpreter in +<b>pcre2_match()</b> to support invalid UTF, and, if <b>pcre2_jit_compile()</b> +is called, the compiled JIT code also supports invalid UTF. Details of how this +support works, in both the JIT and the interpretive cases, is given in the +<a href="pcre2unicode.html"><b>pcre2unicode</b></a> +documentation. +</P> +<P> +There is also an obsolete option for <b>pcre2_jit_compile()</b> called +PCRE2_JIT_INVALID_UTF, which currently exists only for backward compatibility. +It is superseded by the <b>pcre2_compile()</b> option PCRE2_MATCH_INVALID_UTF +and should no longer be used. It may be removed in future. </P> <br><a name="SEC5" href="#TOC1">UNSUPPORTED OPTIONS AND PATTERN ITEMS</a><br> <P> @@ -461,7 +465,7 @@ Cambridge, England. </P> <br><a name="SEC14" href="#TOC1">REVISION</a><br> <P> -Last updated: 06 March 2019 +Last updated: 23 May 2019 <br> Copyright © 1997-2019 University of Cambridge. <br> diff --git a/doc/html/pcre2matching.html b/doc/html/pcre2matching.html index 3e32cb5..340078e 100644 --- a/doc/html/pcre2matching.html +++ b/doc/html/pcre2matching.html @@ -188,6 +188,10 @@ code unit) at a time, for all active paths through the tree. 9. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) are not supported. (*FAIL) is supported, and behaves like a failing negative assertion. </P> +<P> +10. The PCRE2_MATCH_INVALID_UTF option for <b>pcre2_compile()</b> is not +supported by <b>pcre2_dfa_match()</b>. +</P> <br><a name="SEC5" href="#TOC1">ADVANTAGES OF THE ALTERNATIVE ALGORITHM</a><br> <P> Using the alternative matching algorithm provides the following advantages: @@ -219,7 +223,8 @@ because it has to search for all possible matches, but is also because it is less susceptible to optimization. </P> <P> -2. Capturing parentheses, backreferences, and script runs are not supported. +2. Capturing parentheses, backreferences, script runs, and matching within +invalid UTF string are not supported. </P> <P> 3. Although atomic groups are supported, their use does not provide the @@ -236,9 +241,9 @@ Cambridge, England. </P> <br><a name="SEC8" href="#TOC1">REVISION</a><br> <P> -Last updated: 10 October 2018 +Last updated: 23 May 2019 <br> -Copyright © 1997-2018 University of Cambridge. +Copyright © 1997-2019 University of Cambridge. <br> <p> Return to the <a href="index.html">PCRE2 index page</a>. diff --git a/doc/html/pcre2pattern.html b/doc/html/pcre2pattern.html index e6958c1..e850ae0 100644 --- a/doc/html/pcre2pattern.html +++ b/doc/html/pcre2pattern.html @@ -91,10 +91,11 @@ single code units, or as multiple UTF-8 or UTF-16 code units. UTF-32 can be specified for the 32-bit library, in which case it constrains the character values to valid Unicode code points. To process UTF strings, PCRE2 must be built to include Unicode support (which is the default). When using UTF strings -you must either call the compiling function with the PCRE2_UTF option, or the -pattern must start with the special sequence (*UTF), which is equivalent to -setting the relevant option. How setting a UTF mode affects pattern matching is -mentioned in several places below. There is also a summary of features in the +you must either call the compiling function with one or both of the PCRE2_UTF +or PCRE2_MATCH_INVALID_UTF options, or the pattern must start with the special +sequence (*UTF), which is equivalent to setting the relevant PCRE2_UTF. How +setting a UTF mode affects pattern matching is mentioned in several places +below. There is also a summary of features in the <a href="pcre2unicode.html"><b>pcre2unicode</b></a> page. </P> @@ -428,11 +429,11 @@ There may be any number of hexadecimal digits. This syntax is from ECMAScript 6. </P> <P> -The \N{U+hhh..} escape sequence is recognized only when the PCRE2_UTF option -is set, that is, when PCRE2 is operating in a Unicode mode. Perl also uses -\N{name} to specify characters by Unicode name; PCRE2 does not support this. -Note that when \N is not followed by an opening brace (curly bracket) it has -an entirely different meaning, matching any character that is not a newline. +The \N{U+hhh..} escape sequence is recognized only when PCRE2 is operating in +UTF mode. Perl also uses \N{name} to specify characters by Unicode name; PCRE2 +does not support this. Note that when \N is not followed by an opening brace +(curly bracket) it has an entirely different meaning, matching any character +that is not a newline. </P> <P> There are some legacy applications where the escape sequence \r is expected to @@ -1360,7 +1361,7 @@ with \C in UTF-8 or UTF-16 mode means that the rest of the string may start with a malformed UTF character. This has undefined results, because PCRE2 assumes that it is matching character by character in a valid UTF string (by default it checks the subject string's validity at the start of processing -unless the PCRE2_NO_UTF_CHECK option is used). +unless the PCRE2_NO_UTF_CHECK or PCRE2_MATCH_INVALID_UTF option is used). </P> <P> An application can lock out the use of \C by setting the @@ -3727,7 +3728,7 @@ Cambridge, England. </P> <br><a name="SEC31" href="#TOC1">REVISION</a><br> <P> -Last updated: 12 February 2019 +Last updated: 23 May 2019 <br> Copyright © 1997-2019 University of Cambridge. <br> diff --git a/doc/html/pcre2test.html b/doc/html/pcre2test.html index 083d5cc..6d9e839 100644 --- a/doc/html/pcre2test.html +++ b/doc/html/pcre2test.html @@ -613,6 +613,7 @@ for a description of the effects of these options. firstline set PCRE2_FIRSTLINE literal set PCRE2_LITERAL match_line set PCRE2_EXTRA_MATCH_LINE + match_invalid_utf set PCRE2_MATCH_INVALID_UTF match_unset_backref set PCRE2_MATCH_UNSET_BACKREF match_word set PCRE2_EXTRA_MATCH_WORD /m multiline set PCRE2_MULTILINE @@ -2078,7 +2079,7 @@ Cambridge, England. </P> <br><a name="SEC21" href="#TOC1">REVISION</a><br> <P> -Last updated: 11 March 2019 +Last updated: 23 May 2019 <br> Copyright © 1997-2019 University of Cambridge. <br> diff --git a/doc/html/pcre2unicode.html b/doc/html/pcre2unicode.html index c11c7c2..f540b7c 100644 --- a/doc/html/pcre2unicode.html +++ b/doc/html/pcre2unicode.html @@ -16,22 +16,33 @@ please consult the man page, in case the conversion went wrong. UNICODE AND UTF SUPPORT </b><br> <P> -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 +PCRE2 is normally built with Unicode support, though if you do not need it, you +can build it without, in which case the library will be smaller. With Unicode +support, PCRE2 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), but this is not the default. Unless specifically requested, PCRE2 +treats each code unit in a string as one character. +</P> +<P> +There are two ways of telling PCRE2 to switch to UTF mode, where characters may +consist of more than one code unit and the range of values is constrained. The +program can call <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. There are also some other -changes to the way characters are handled, as documented below. +with the PCRE2_UTF option, or the pattern may start with the sequence (*UTF). +However, the latter facility can be locked out by the PCRE2_NEVER_UTF option. +That is, the programmer can prevent the supplier of the pattern from switching +to UTF mode. +</P> +<P> +Note that the PCRE2_MATCH_INVALID_UTF option (see +<a href="#matchinvalid">below)</a> +forces PCRE2_UTF to be set. </P> <P> -If you do not need Unicode support you can build PCRE2 without it, in which -case the library will be smaller. +In UTF mode, 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. There are also some other changes to the way characters are +handled, as documented below. </P> <br><b> UNICODE PROPERTY SUPPORT @@ -63,22 +74,22 @@ also recognized; larger ones can be coded using \o{...}. <P> The escape sequence \N{U+<hex digits>} is recognized as another way of specifying a Unicode character by code point in a UTF mode. It is not allowed -in non-UTF modes. +in non-UTF mode. </P> <P> -In UTF modes, repeat quantifiers apply to complete UTF characters, not to +In UTF mode, 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 +In UTF mode, the dot metacharacter matches one UTF character instead of a single code unit. </P> <P> -In UTF modes, capture group names are not restricted to ASCII, and may contain +In UTF mode, capture group names are not restricted to ASCII, and may contain any Unicode letters and decimal digits, as well as underscore. </P> <P> -The escape sequence \C can be used to match a single code unit in a UTF mode, +The escape sequence \C can be used to match a single code unit in UTF mode, 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> @@ -93,7 +104,7 @@ may consist of more than one code unit. The use of \C in these modes provokes a match-time error. Also, the JIT optimization does not support \C in these modes. If JIT optimization is requested for a UTF-8 or UTF-16 pattern that contains \C, it will not succeed, and so when <b>pcre2_match()</b> is called, -the matching will be carried out by the normal interpretive function. +the matching will be carried out by the interpretive function. </P> <P> The character escapes \b, \B, \d, \D, \s, \S, \w, and \W correctly test @@ -123,14 +134,14 @@ However, the special horizontal and vertical white space matching escapes (\h, not PCRE2_UCP is set. </P> <br><b> -CASE-EQUIVALENCE IN UTF MODES +CASE-EQUIVALENCE IN UTF MODE </b><br> <P> -Case-insensitive matching in a UTF mode makes use of Unicode properties except +Case-insensitive matching in UTF mode makes use of Unicode properties except for characters whose code points are less than 128 and that have at most two case-equivalent values. For these, a direct table lookup is used for speed. A few Unicode characters such as Greek sigma have more than two code points that -are case-equivalent, and these are treated as such. +are case-equivalent, and these are treated specially. <a name="scriptruns"></a></P> <br><b> SCRIPT RUNS @@ -248,7 +259,7 @@ VALIDITY OF UTF STRINGS <P> When the PCRE2_UTF option is set, the strings passed as patterns and subjects are (by default) checked for validity on entry to the relevant functions. If an -invalid UTF string is passed, an negative error code is returned. The code unit +invalid UTF string is passed, a 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. @@ -263,17 +274,16 @@ only valid UTF code unit sequences. </P> <P> If you pass an invalid UTF string when PCRE2_NO_UTF_CHECK is set, the result -is usually undefined and your program may crash or loop indefinitely. There is, -however, one mode of matching that can handle invalid UTF subject strings. This -is matching via the JIT optimization using the PCRE2_JIT_INVALID_UTF option -when calling <b>pcre2_jit_compile()</b>. For details, see the -<a href="pcre2jit.html"><b>pcre2jit</b></a> -documentation. +is undefined and your program may crash or loop indefinitely or give incorrect +results. There is, however, one mode of matching that can handle invalid UTF +subject strings. This is enabled by passing PCRE2_MATCH_INVALID_UTF to +<b>pcre2_compile()</b> and is discussed below in the next section. The rest of +this section covers the case when PCRE2_MATCH_INVALID_UTF is not set. </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 -the check for a subject string you must pass this same option to +Passing PCRE2_NO_UTF_CHECK to <b>pcre2_compile()</b> just disables the UTF check +for the pattern; it does not also apply to subject strings. If you want to +disable the check for a subject string you must pass this same option to <b>pcre2_match()</b> or <b>pcre2_dfa_match()</b>. </P> <P> @@ -352,7 +362,7 @@ 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 +A 4-byte character has a value greater than 0x10ffff; these code points are excluded by RFC 3629. <pre> PCRE2_ERROR_UTF8_ERR14 @@ -405,7 +415,59 @@ The following negative error codes are given for invalid UTF-32 strings: PCRE2_ERROR_UTF32_ERR1 Surrogate character (0xd800 to 0xdfff) PCRE2_ERROR_UTF32_ERR2 Code point is greater than 0x10ffff -</PRE> +<a name="matchinvalid"></a></PRE> +</P> +<br><b> +MATCHING IN INVALID UTF STRINGS +</b><br> +<P> +You can run pattern matches on subject strings that may contain invalid UTF +sequences if you call <b>pcre2_compile()</b> with the PCRE2_MATCH_INVALID_UTF +option. This is supported by <b>pcre2_match()</b>, including JIT matching, but +not by <b>pcre2_dfa_match()</b>. When PCRE2_MATCH_INVALID_UTF is set, it forces +PCRE2_UTF to be set as well. Note, however, that the pattern itself must be a +valid UTF string. +</P> +<P> +Setting PCRE2_MATCH_INVALID_UTF does not affect what <b>pcre2_compile()</b> +generates, but if <b>pcre2_jit_compile()</b> is subsequently called, it does +generate different code. If JIT is not used, the option affects the behaviour +of the interpretive code in <b>pcre2_match()</b>. When PCRE2_MATCH_INVALID_UTF +is set at compile time, PCRE2_NO_UTF_CHECK is ignored at match time. +</P> +<P> +In this mode, an invalid code unit sequence in the subject never matches any +pattern item. It does not match dot, it does not match \p{Any}, it does not +even match negative items such as [^X]. A lookbehind assertion fails if it +encounters an invalid sequence while moving the current point backwards. In +other words, an invalid UTF code unit sequence acts as a barrier which no match +can cross. +</P> +<P> +You can also think of this as the subject being split up into fragments of +valid UTF, delimited internally by invalid code unit sequences. The pattern is +matched fragment by fragment. The result of a successful match, however, is +given as code unit offsets in the entire subject string in the usual way. There +are a few points to consider: +</P> +<P> +The internal boundaries are not interpreted as the beginnings or ends of lines +and so do not match circumflex or dollar characters in the pattern. +</P> +<P> +If <b>pcre2_match()</b> is called with an offset that points to an invalid +UTF-sequence, that sequence is skipped, and the match starts at the next valid +UTF character, or the end of the subject. +</P> +<P> +At internal fragment boundaries, \b and \B behave in the same way as at the +beginning and end of the subject. For example, a sequence such as \bWORD\b +would match an instance of WORD that is surrounded by invalid UTF code units. +</P> +<P> +Using PCRE2_MATCH_INVALID_UTF, an application can run matches on arbitrary +data, knowing that any matched strings that are returned are valid UTF. This +can be useful when searching for UTF text in executable or other binary files. </P> <br><b> AUTHOR @@ -422,7 +484,7 @@ Cambridge, England. REVISION </b><br> <P> -Last updated: 06 March 2019 +Last updated: 24 May 2019 <br> Copyright © 1997-2019 University of Cambridge. <br> diff --git a/doc/pcre2.txt b/doc/pcre2.txt index 9c956e8..18e16da 100644 --- a/doc/pcre2.txt +++ b/doc/pcre2.txt @@ -180,8 +180,8 @@ REVISION Last updated: 17 September 2018 Copyright (c) 1997-2018 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2API(3) Library Functions Manual PCRE2API(3) @@ -1336,29 +1336,30 @@ COMPILING A PATTERN There are nearly 100 positive error codes that pcre2_compile() may return if it finds an error in the pattern. There are also some nega- - tive error codes that are used for invalid UTF strings. These are the - same as given by pcre2_match() and pcre2_dfa_match(), and are described - in the pcre2unicode page. There is no separate documentation for the - positive error codes, because the textual error messages that are - obtained by calling the pcre2_get_error_message() function (see - "Obtaining a textual error message" below) should be self-explanatory. - Macro names starting with PCRE2_ERROR_ are defined for both positive - and negative error codes in pcre2.h. + tive error codes that are used for invalid UTF strings when validity + checking is in force. These are the same as given by pcre2_match() and + pcre2_dfa_match(), and are described in the pcre2unicode documentation. + There is no separate documentation for the positive error codes, + because the textual error messages that are obtained by calling the + pcre2_get_error_message() function (see "Obtaining a textual error mes- + sage" below) should be self-explanatory. Macro names starting with + PCRE2_ERROR_ are defined for both positive and negative error codes in + pcre2.h. The value returned in erroroffset is an indication of where in the pat- - tern the error occurred. It is not necessarily the furthest point in - the pattern that was read. For example, after the error "lookbehind + tern the error occurred. It is not necessarily the furthest point in + the pattern that was read. For example, after the error "lookbehind assertion is not fixed length", the error offset points to the start of - the failing assertion. For an invalid UTF-8 or UTF-16 string, the off- + the failing assertion. For an invalid UTF-8 or UTF-16 string, the off- set is that of the first code unit of the failing character. - Some errors are not detected until the whole pattern has been scanned; - in these cases, the offset passed back is the length of the pattern. - Note that the offset is in code units, not characters, even in a UTF + Some errors are not detected until the whole pattern has been scanned; + in these cases, the offset passed back is the length of the pattern. + Note that the offset is in code units, not characters, even in a UTF mode. It may sometimes point into the middle of a UTF-8 or UTF-16 char- acter. - This code fragment shows a typical straightforward call to pcre2_com- + This code fragment shows a typical straightforward call to pcre2_com- pile(): pcre2_code *re; @@ -1375,226 +1376,233 @@ COMPILING A PATTERN Main compile options - The following names for option bits are defined in the pcre2.h header + The following names for option bits are defined in the pcre2.h header file: PCRE2_ANCHORED If this bit is set, the pattern is forced to be "anchored", that is, it - is constrained to match only at the first matching point in the string - that is being searched (the "subject string"). This effect can also be - achieved by appropriate constructs in the pattern itself, which is the + is constrained to match only at the first matching point in the string + that is being searched (the "subject string"). This effect can also be + achieved by appropriate constructs in the pattern itself, which is the only way to do it in Perl. PCRE2_ALLOW_EMPTY_CLASS - By default, for compatibility with Perl, a closing square bracket that - immediately follows an opening one is treated as a data character for - the class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the + By default, for compatibility with Perl, a closing square bracket that + immediately follows an opening one is treated as a data character for + the class. When PCRE2_ALLOW_EMPTY_CLASS is set, it terminates the class, which therefore contains no characters and so can never match. PCRE2_ALT_BSUX - This option request alternative handling of three escape sequences, - which makes PCRE2's behaviour more like ECMAscript (aka JavaScript). + This option request alternative handling of three escape sequences, + which makes PCRE2's behaviour more like ECMAscript (aka JavaScript). When it is set: (1) \U matches an upper case "U" character; by default \U causes a com- pile time error (Perl uses \U to upper case subsequent characters). (2) \u matches a lower case "u" character unless it is followed by four - hexadecimal digits, in which case the hexadecimal number defines the - code point to match. By default, \u causes a compile time error (Perl + hexadecimal digits, in which case the hexadecimal number defines the + code point to match. By default, \u causes a compile time error (Perl uses it to upper case the following character). - (3) \x matches a lower case "x" character unless it is followed by two - hexadecimal digits, in which case the hexadecimal number defines the - code point to match. By default, as in Perl, a hexadecimal number is + (3) \x matches a lower case "x" character unless it is followed by two + hexadecimal digits, in which case the hexadecimal number defines the + code point to match. By default, as in Perl, a hexadecimal number is always expected after \x, but it may have zero, one, or two digits (so, for example, \xz matches a binary zero character followed by z). ECMAscript 6 added additional functionality to \u. This can be accessed - using the PCRE2_EXTRA_ALT_BSUX extra option (see "Extra compile - options" below). Note that this alternative escape handling applies - only to patterns. Neither of these options affects the processing of + using the PCRE2_EXTRA_ALT_BSUX extra option (see "Extra compile + options" below). Note that this alternative escape handling applies + only to patterns. Neither of these options affects the processing of replacement strings passed to pcre2_substitute(). PCRE2_ALT_CIRCUMFLEX In multiline mode (when PCRE2_MULTILINE is set), the circumflex - metacharacter matches at the start of the subject (unless PCRE2_NOTBOL - is set), and also after any internal newline. However, it does not + metacharacter matches at the start of the subject (unless PCRE2_NOTBOL + is set), and also after any internal newline. However, it does not match after a newline at the end of the subject, for compatibility with - Perl. If you want a multiline circumflex also to match after a termi- + Perl. If you want a multiline circumflex also to match after a termi- nating newline, you must set PCRE2_ALT_CIRCUMFLEX. PCRE2_ALT_VERBNAMES - By default, for compatibility with Perl, the name in any verb sequence - such as (*MARK:NAME) is any sequence of characters that does not - include a closing parenthesis. The name is not processed in any way, - and it is not possible to include a closing parenthesis in the name. - However, if the PCRE2_ALT_VERBNAMES option is set, normal backslash - processing is applied to verb names and only an unescaped closing - parenthesis terminates the name. A closing parenthesis can be included - in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED or - PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped - whitespace in verb names is skipped and #-comments are recognized, + By default, for compatibility with Perl, the name in any verb sequence + such as (*MARK:NAME) is any sequence of characters that does not + include a closing parenthesis. The name is not processed in any way, + and it is not possible to include a closing parenthesis in the name. + However, if the PCRE2_ALT_VERBNAMES option is set, normal backslash + processing is applied to verb names and only an unescaped closing + parenthesis terminates the name. A closing parenthesis can be included + in a name either as \) or between \Q and \E. If the PCRE2_EXTENDED or + PCRE2_EXTENDED_MORE option is set with PCRE2_ALT_VERBNAMES, unescaped + whitespace in verb names is skipped and #-comments are recognized, exactly as in the rest of the pattern. PCRE2_AUTO_CALLOUT - If this bit is set, pcre2_compile() automatically inserts callout - items, all with number 255, before each pattern item, except immedi- - ately before or after an explicit callout in the pattern. For discus- + If this bit is set, pcre2_compile() automatically inserts callout + items, all with number 255, before each pattern item, except immedi- + ately before or after an explicit callout in the pattern. For discus- sion of the callout facility, see the pcre2callout documentation. PCRE2_CASELESS - If this bit is set, letters in the pattern match both upper and lower - case letters in the subject. It is equivalent to Perl's /i option, and - it can be changed within a pattern by a (?i) option setting. If - PCRE2_UTF is set, Unicode properties are used for all characters with - more than one other case, and for all characters whose code points are - greater than U+007F. For lower valued characters with only one other - case, a lookup table is used for speed. When PCRE2_UTF is not set, a + If this bit is set, letters in the pattern match both upper and lower + case letters in the subject. It is equivalent to Perl's /i option, and + it can be changed within a pattern by a (?i) option setting. If + PCRE2_UTF is set, Unicode properties are used for all characters with + more than one other case, and for all characters whose code points are + greater than U+007F. For lower valued characters with only one other + case, a lookup table is used for speed. When PCRE2_UTF is not set, a lookup table is used for all code points less than 256, and higher code - points (available only in 16-bit or 32-bit mode) are treated as not + points (available only in 16-bit or 32-bit mode) are treated as not having another case. PCRE2_DOLLAR_ENDONLY - If this bit is set, a dollar metacharacter in the pattern matches only - at the end of the subject string. Without this option, a dollar also - matches immediately before a newline at the end of the string (but not - before any other newlines). The PCRE2_DOLLAR_ENDONLY option is ignored - if PCRE2_MULTILINE is set. There is no equivalent to this option in + If this bit is set, a dollar metacharacter in the pattern matches only + at the end of the subject string. Without this option, a dollar also + matches immediately before a newline at the end of the string (but not + before any other newlines). The PCRE2_DOLLAR_ENDONLY option is ignored + if PCRE2_MULTILINE is set. There is no equivalent to this option in Perl, and no way to set it within a pattern. PCRE2_DOTALL - If this bit is set, a dot metacharacter in the pattern matches any - character, including one that indicates a newline. However, it only + If this bit is set, a dot metacharacter in the pattern matches any + character, including one that indicates a newline. However, it only ever matches one character, even if newlines are coded as CRLF. Without this option, a dot does not match when the current position in the sub- - ject is at a newline. This option is equivalent to Perl's /s option, + ject is at a newline. This option is equivalent to Perl's /s option, and it can be changed within a pattern by a (?s) option setting. A neg- - ative class such as [^a] always matches newline characters, and the \N - escape sequence always matches a non-newline character, independent of + ative class such as [^a] always matches newline characters, and the \N + escape sequence always matches a non-newline character, independent of the setting of PCRE2_DOTALL. PCRE2_DUPNAMES - If this bit is set, names used to identify capture groups need not be - unique. This can be helpful for certain types of pattern when it is - known that only one instance of the named group can ever be matched. - There are more details of named capture groups below; see also the + If this bit is set, names used to identify capture groups need not be + unique. This can be helpful for certain types of pattern when it is + known that only one instance of the named group can ever be matched. + There are more details of named capture groups below; see also the pcre2pattern documentation. PCRE2_ENDANCHORED - If this bit is set, the end of any pattern match must be right at the + If this bit is set, the end of any pattern match must be right at the end of the string being searched (the "subject string"). If the pattern match succeeds by reaching (*ACCEPT), but does not reach the end of the - subject, the match fails at the current starting point. For unanchored - patterns, a new match is then tried at the next starting point. How- + subject, the match fails at the current starting point. For unanchored + patterns, a new match is then tried at the next starting point. How- ever, if the match succeeds by reaching the end of the pattern, but not - the end of the subject, backtracking occurs and an alternative match + the end of the subject, backtracking occurs and an alternative match may be found. Consider these two patterns: .(*ACCEPT)|.. .|.. - If matched against "abc" with PCRE2_ENDANCHORED set, the first matches - "c" whereas the second matches "bc". The effect of PCRE2_ENDANCHORED - can also be achieved by appropriate constructs in the pattern itself, + If matched against "abc" with PCRE2_ENDANCHORED set, the first matches + "c" whereas the second matches "bc". The effect of PCRE2_ENDANCHORED + can also be achieved by appropriate constructs in the pattern itself, which is the only way to do it in Perl. For DFA matching with pcre2_dfa_match(), PCRE2_ENDANCHORED applies only - to the first (that is, the longest) matched string. Other parallel - matches, which are necessarily substrings of the first one, must obvi- + to the first (that is, the longest) matched string. Other parallel + matches, which are necessarily substrings of the first one, must obvi- ously end before the end of the subject. PCRE2_EXTENDED - If this bit is set, most white space characters in the pattern are - totally ignored except when escaped or inside a character class. How- - ever, white space is not allowed within sequences such as (?> that - introduce various parenthesized groups, nor within numerical quanti- + If this bit is set, most white space characters in the pattern are + totally ignored except when escaped or inside a character class. How- + ever, white space is not allowed within sequences such as (?> that + introduce various parenthesized groups, nor within numerical quanti- fiers such as {1,3}. Ignorable white space is permitted between an item - and a following quantifier and between a quantifier and a following + - that indicates possessiveness. PCRE2_EXTENDED is equivalent to Perl's + and a following quantifier and between a quantifier and a following + + that indicates possessiveness. PCRE2_EXTENDED is equivalent to Perl's /x option, and it can be changed within a pattern by a (?x) option set- ting. - When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recog- - nizes as white space only those characters with code points less than + When PCRE2 is compiled without Unicode support, PCRE2_EXTENDED recog- + nizes as white space only those characters with code points less than 256 that are flagged as white space in its low-character table. The ta- ble is normally created by pcre2_maketables(), which uses the isspace() - function to identify space characters. In most ASCII environments, the - relevant characters are those with code points 0x0009 (tab), 0x000A - (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D (carriage + function to identify space characters. In most ASCII environments, the + relevant characters are those with code points 0x0009 (tab), 0x000A + (linefeed), 0x000B (vertical tab), 0x000C (formfeed), 0x000D (carriage return), and 0x0020 (space). When PCRE2 is compiled with Unicode support, in addition to these char- - acters, five more Unicode "Pattern White Space" characters are recog- + acters, five more Unicode "Pattern White Space" characters are recog- nized by PCRE2_EXTENDED. These are U+0085 (next line), U+200E (left-to- - right mark), U+200F (right-to-left mark), U+2028 (line separator), and - U+2029 (paragraph separator). This set of characters is the same as - recognized by Perl's /x option. Note that the horizontal and vertical - space characters that are matched by the \h and \v escapes in patterns + right mark), U+200F (right-to-left mark), U+2028 (line separator), and + U+2029 (paragraph separator). This set of characters is the same as + recognized by Perl's /x option. Note that the horizontal and vertical + space characters that are matched by the \h and \v escapes in patterns are a much bigger set. - As well as ignoring most white space, PCRE2_EXTENDED also causes char- - acters between an unescaped # outside a character class and the next - newline, inclusive, to be ignored, which makes it possible to include + As well as ignoring most white space, PCRE2_EXTENDED also causes char- + acters between an unescaped # outside a character class and the next + newline, inclusive, to be ignored, which makes it possible to include comments inside complicated patterns. Note that the end of this type of - comment is a literal newline sequence in the pattern; escape sequences + comment is a literal newline sequence in the pattern; escape sequences that happen to represent a newline do not count. Which characters are interpreted as newlines can be specified by a set- - ting in the compile context that is passed to pcre2_compile() or by a - special sequence at the start of the pattern, as described in the sec- - tion entitled "Newline conventions" in the pcre2pattern documentation. + ting in the compile context that is passed to pcre2_compile() or by a + special sequence at the start of the pattern, as described in the sec- + tion entitled "Newline conventions" in the pcre2pattern documentation. A default is defined when PCRE2 is built. PCRE2_EXTENDED_MORE - This option has the effect of PCRE2_EXTENDED, but, in addition, - unescaped space and horizontal tab characters are ignored inside a - character class. Note: only these two characters are ignored, not the - full set of pattern white space characters that are ignored outside a + This option has the effect of PCRE2_EXTENDED, but, in addition, + unescaped space and horizontal tab characters are ignored inside a + character class. Note: only these two characters are ignored, not the + full set of pattern white space characters that are ignored outside a character class. PCRE2_EXTENDED_MORE is equivalent to Perl's /xx - option, and it can be changed within a pattern by a (?xx) option set- + option, and it can be changed within a pattern by a (?xx) option set- ting. PCRE2_FIRSTLINE If this option is set, the start of an unanchored pattern match must be - before or at the first newline in the subject string following the - start of matching, though the matched text may continue over the new- + before or at the first newline in the subject string following the + start of matching, though the matched text may continue over the new- line. If startoffset is non-zero, the limiting newline is not necessar- - ily the first newline in the subject. For example, if the subject + ily the first newline in the subject. For example, if the subject string is "abc\nxyz" (where \n represents a single-character newline) a - pattern match for "yz" succeeds with PCRE2_FIRSTLINE if startoffset is - greater than 3. See also PCRE2_USE_OFFSET_LIMIT, which provides a more - general limiting facility. If PCRE2_FIRSTLINE is set with an offset - limit, a match must occur in the first line and also within the offset + pattern match for "yz" succeeds with PCRE2_FIRSTLINE if startoffset is + greater than 3. See also PCRE2_USE_OFFSET_LIMIT, which provides a more + general limiting facility. If PCRE2_FIRSTLINE is set with an offset + limit, a match must occur in the first line and also within the offset limit. In other words, whichever limit comes first is used. PCRE2_LITERAL If this option is set, all meta-characters in the pattern are disabled, - and it is treated as a literal string. Matching literal strings with a + and it is treated as a literal string. Matching literal strings with a regular expression engine is not the most efficient way of doing it. If - you are doing a lot of literal matching and are worried about effi- + you are doing a lot of literal matching and are worried about effi- ciency, you should consider using other approaches. The only other main options that are allowed with PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, PCRE2_CASELESS, PCRE2_FIRSTLINE, - PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, PCRE2_UTF, and - PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE and - PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an - error. + PCRE2_MATCH_INVALID_UTF, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, + PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options + PCRE2_EXTRA_MATCH_LINE and PCRE2_EXTRA_MATCH_WORD are also supported. + Any other options cause an error. + + PCRE2_MATCH_INVALID_UTF + + This option forces PCRE2_UTF (see below) and also enables support for + matching by pcre2_match() in subject strings that contain invalid UTF + sequences. This facility is not supported for DFA matching. For + details, see the pcre2unicode documentation. PCRE2_MATCH_UNSET_BACKREF @@ -2608,33 +2616,39 @@ MATCHING A PATTERN: THE TRADITIONAL FUNCTION PCRE2_NO_UTF_CHECK When PCRE2_UTF is set at compile time, the validity of the subject as a - UTF string is checked by default when pcre2_match() is subsequently - called. If a non-zero starting offset is given, the check is applied - only to that part of the subject that could be inspected during match- - ing, 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. + UTF string is checked unless PCRE2_NO_UTF_CHECK is passed to + pcre2_match() or PCRE2_MATCH_INVALID_UTF was passed to pcre2_compile(). + The latter special case is discussed in detail in the pcre2unicode doc- + umentation. + + In the default case, if a non-zero starting offset is given, 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. The check is carried out before any other processing takes place, and a negative error code is returned if the check fails. There are several UTF error codes for each code unit width, corresponding to different problems with the code unit sequence. There are discussions about the validity of UTF-8 strings, UTF-16 strings, and UTF-32 strings in the - pcre2unicode page. + pcre2unicode documentation. - If you know that your subject is valid, and you want to skip these - checks for performance reasons, you can set the PCRE2_NO_UTF_CHECK - option when calling pcre2_match(). You might want to do this for the - second and subsequent calls to pcre2_match() if you are making repeated - calls to find other matches in the same subject string. + If you know that your subject is valid, and you want to skip this check + for performance reasons, you can set the PCRE2_NO_UTF_CHECK option when + calling pcre2_match(). You might want to do this for the second and + subsequent calls to pcre2_match() if you are making repeated calls to + find multiple matches in the same subject string. - Warning: When PCRE2_NO_UTF_CHECK is set, the effect of passing an - invalid string as a subject, or an invalid value of startoffset, is - undefined. Your program may crash or loop indefinitely. + Warning: Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when + PCRE2_NO_UTF_CHECK is set at match time the effect of passing an + invalid string as a subject, or an invalid value of startoffset, is + undefined. Your program may crash or loop indefinitely or give wrong + results. PCRE2_PARTIAL_HARD PCRE2_PARTIAL_SOFT @@ -3642,6 +3656,12 @@ MATCHING A PATTERN: THE ALTERNATIVE FUNCTION that uses a backreference for the condition, or a test for recursion in a specific capture group. These are not supported. + PCRE2_ERROR_DFA_UINVALID_UTF + + This return is given if pcre2_dfa_match() is called for a pattern that + was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for + DFA matching. + PCRE2_ERROR_DFA_WSSIZE This return is given if pcre2_dfa_match() runs out of space in the @@ -3678,11 +3698,11 @@ AUTHOR REVISION - Last updated: 14 February 2019 + Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2BUILD(3) Library Functions Manual PCRE2BUILD(3) @@ -4254,8 +4274,8 @@ REVISION Last updated: 03 March 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2CALLOUT(3) Library Functions Manual PCRE2CALLOUT(3) @@ -4685,8 +4705,8 @@ REVISION Last updated: 03 February 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2COMPAT(3) Library Functions Manual PCRE2COMPAT(3) @@ -4890,8 +4910,8 @@ REVISION Last updated: 12 February 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2JIT(3) Library Functions Manual PCRE2JIT(3) @@ -5012,25 +5032,27 @@ SIMPLE USE OF JIT MATCHING SUBJECTS CONTAINING INVALID UTF - When a pattern is compiled with the PCRE2_UTF option, the interpretive - matching function expects its subject string to be a valid sequence of - UTF code units. If it is not, the result is undefined. This is also - true by default of matching via JIT. However, if the option - PCRE2_JIT_INVALID_UTF is passed to pcre2_jit_compile(), code that can - process a subject containing invalid UTF is compiled. - - In this mode, an invalid code unit sequence never matches any pattern - item. It does not match dot, it does not match \p{Any}, it does not - even match negative items such as [^X]. A lookbehind assertion fails if - it encounters an invalid sequence while moving the current point back- - wards. In other words, an invalid UTF code unit sequence acts as a bar- - rier which no match can cross. Reaching an invalid sequence causes an - immediate backtrack. - - Using this option, an application can run matches in arbitrary data, - knowing that any matched strings that are returned will be valid UTF. - This can be useful when searching for text in executable or other - binary files. + When a pattern is compiled with the PCRE2_UTF option, subject strings + are normally expected to be a valid sequence of UTF code units. By + default, this is checked at the start of matching and an error is gen- + erated if invalid UTF is detected. The PCRE2_NO_UTF_CHECK option can be + passed to pcre2_match() to skip the check (for improved performance) if + you are sure that a subject string is valid. If this option is used + with an invalid string, the result is undefined. + + However, a way of running matches on strings that may contain invalid + UTF sequences is available. Calling pcre2_compile() with the + PCRE2_MATCH_INVALID_UTF option has two effects: it tells the inter- + preter in pcre2_match() to support invalid UTF, and, if pcre2_jit_com- + pile() is called, the compiled JIT code also supports invalid UTF. + Details of how this support works, in both the JIT and the interpretive + cases, is given in the pcre2unicode documentation. + + There is also an obsolete option for pcre2_jit_compile() called + PCRE2_JIT_INVALID_UTF, which currently exists only for backward compat- + ibility. It is superseded by the pcre2_compile() option + PCRE2_MATCH_INVALID_UTF and should no longer be used. It may be removed + in future. UNSUPPORTED OPTIONS AND PATTERN ITEMS @@ -5310,11 +5332,11 @@ AUTHOR REVISION - Last updated: 06 March 2019 + Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2LIMITS(3) Library Functions Manual PCRE2LIMITS(3) @@ -5383,8 +5405,8 @@ REVISION Last updated: 02 February 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2MATCHING(3) Library Functions Manual PCRE2MATCHING(3) @@ -5556,23 +5578,26 @@ THE ALTERNATIVE MATCHING ALGORITHM are not supported. (*FAIL) is supported, and behaves like a failing negative assertion. + 10. The PCRE2_MATCH_INVALID_UTF option for pcre2_compile() is not sup- + ported by pcre2_dfa_match(). + ADVANTAGES OF THE ALTERNATIVE ALGORITHM - Using the alternative matching algorithm provides the following advan- + Using the alternative matching algorithm provides the following advan- tages: 1. All possible matches (at a single point in the subject) are automat- - ically found, and in particular, the longest match is found. To find + ically found, and in particular, the longest match is found. To find more than one match using the standard algorithm, you have to do kludgy things with callouts. - 2. Because the alternative algorithm scans the subject string just + 2. Because the alternative algorithm scans the subject string just once, and never needs to backtrack (except for lookbehinds), it is pos- - sible to pass very long subject strings to the matching function in + sible to pass very long subject strings to the matching function in several pieces, checking for partial matching each time. Although it is - also possible to do multi-segment matching using the standard algo- - rithm, by retaining partially matched substrings, it is more compli- + also possible to do multi-segment matching using the standard algo- + rithm, by retaining partially matched substrings, it is more compli- cated. The pcre2partial documentation gives details of partial matching and discusses multi-segment matching. @@ -5581,12 +5606,12 @@ DISADVANTAGES OF THE ALTERNATIVE ALGORITHM The alternative algorithm suffers from a number of disadvantages: - 1. It is substantially slower than the standard algorithm. This is - partly because it has to search for all possible matches, but is also + 1. It is substantially slower than the standard algorithm. This is + partly because it has to search for all possible matches, but is also because it is less susceptible to optimization. - 2. Capturing parentheses, backreferences, and script runs are not sup- - ported. + 2. Capturing parentheses, backreferences, script runs, and matching + within invalid UTF string are not supported. 3. Although atomic groups are supported, their use does not provide the performance advantage that it does for the standard algorithm. @@ -5601,11 +5626,11 @@ AUTHOR REVISION - Last updated: 10 October 2018 - Copyright (c) 1997-2018 University of Cambridge. + Last updated: 23 May 2019 + Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2PARTIAL(3) Library Functions Manual PCRE2PARTIAL(3) @@ -6044,8 +6069,8 @@ REVISION Last updated: 22 December 2014 Copyright (c) 1997-2014 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2PATTERN(3) Library Functions Manual PCRE2PATTERN(3) @@ -6098,11 +6123,11 @@ SPECIAL START-OF-PATTERN ITEMS the character values to valid Unicode code points. To process UTF strings, PCRE2 must be built to include Unicode support (which is the default). When using UTF strings you must either call the compiling - function with the PCRE2_UTF option, or the pattern must start with the - special sequence (*UTF), which is equivalent to setting the relevant - option. How setting a UTF mode affects pattern matching is mentioned in - several places below. There is also a summary of features in the - pcre2unicode page. + function with one or both of the PCRE2_UTF or PCRE2_MATCH_INVALID_UTF + options, or the pattern must start with the special sequence (*UTF), + which is equivalent to setting the relevant PCRE2_UTF. How setting a + UTF mode affects pattern matching is mentioned in several places below. + There is also a summary of features in the pcre2unicode page. Some applications that allow their users to supply patterns may wish to restrict them to non-UTF data for security reasons. If the @@ -6406,58 +6431,57 @@ BACKSLASH decimal code point. There may be any number of hexadecimal digits. This syntax is from ECMAScript 6. - The \N{U+hhh..} escape sequence is recognized only when the PCRE2_UTF - option is set, that is, when PCRE2 is operating in a Unicode mode. Perl - also uses \N{name} to specify characters by Unicode name; PCRE2 does - not support this. Note that when \N is not followed by an opening - brace (curly bracket) it has an entirely different meaning, matching - any character that is not a newline. + The \N{U+hhh..} escape sequence is recognized only when PCRE2 is oper- + ating in UTF mode. Perl also uses \N{name} to specify characters by + Unicode name; PCRE2 does not support this. Note that when \N is not + followed by an opening brace (curly bracket) it has an entirely differ- + ent meaning, matching any character that is not a newline. - There are some legacy applications where the escape sequence \r is + There are some legacy applications where the escape sequence \r is expected to match a newline. If the PCRE2_EXTRA_ESCAPED_CR_IS_LF option - is set, \r in a pattern is converted to \n so that it matches a LF + is set, \r in a pattern is converted to \n so that it matches a LF (linefeed) instead of a CR (carriage return) character. - The precise effect of \cx on ASCII characters is as follows: if x is a - lower case letter, it is converted to upper case. Then bit 6 of the + The precise effect of \cx on ASCII characters is as follows: if x is a + lower case letter, it is converted to upper case. Then bit 6 of the character (hex 40) is inverted. Thus \cA to \cZ become hex 01 to hex 1A - (A is 41, Z is 5A), but \c{ becomes hex 3B ({ is 7B), and \c; becomes - hex 7B (; is 3B). If the code unit following \c has a value less than + (A is 41, Z is 5A), but \c{ becomes hex 3B ({ is 7B), and \c; becomes + hex 7B (; is 3B). If the code unit following \c has a value less than 32 or greater than 126, a compile-time error occurs. - When PCRE2 is compiled in EBCDIC mode, \N{U+hhh..} is not supported. + When PCRE2 is compiled in EBCDIC mode, \N{U+hhh..} is not supported. \a, \e, \f, \n, \r, and \t generate the appropriate EBCDIC code values. The \c escape is processed as specified for Perl in the perlebcdic doc- - ument. The only characters that are allowed after \c are A-Z, a-z, or - one of @, [, \, ], ^, _, or ?. Any other character provokes a compile- - time error. The sequence \c@ encodes character code 0; after \c the - letters (in either case) encode characters 1-26 (hex 01 to hex 1A); [, - \, ], ^, and _ encode characters 27-31 (hex 1B to hex 1F), and \c? + ument. The only characters that are allowed after \c are A-Z, a-z, or + one of @, [, \, ], ^, _, or ?. Any other character provokes a compile- + time error. The sequence \c@ encodes character code 0; after \c the + letters (in either case) encode characters 1-26 (hex 01 to hex 1A); [, + \, ], ^, and _ encode characters 27-31 (hex 1B to hex 1F), and \c? becomes either 255 (hex FF) or 95 (hex 5F). - Thus, apart from \c?, these escapes generate the same character code - values as they do in an ASCII environment, though the meanings of the - values mostly differ. For example, \cG always generates code value 7, + Thus, apart from \c?, these escapes generate the same character code + values as they do in an ASCII environment, though the meanings of the + values mostly differ. For example, \cG always generates code value 7, which is BEL in ASCII but DEL in EBCDIC. - The sequence \c? generates DEL (127, hex 7F) in an ASCII environment, - but because 127 is not a control character in EBCDIC, Perl makes it - generate the APC character. Unfortunately, there are several variants - of EBCDIC. In most of them the APC character has the value 255 (hex - FF), but in the one Perl calls POSIX-BC its value is 95 (hex 5F). If + The sequence \c? generates DEL (127, hex 7F) in an ASCII environment, + but because 127 is not a control character in EBCDIC, Perl makes it + generate the APC character. Unfortunately, there are several variants + of EBCDIC. In most of them the APC character has the value 255 (hex + FF), but in the one Perl calls POSIX-BC its value is 95 (hex 5F). If certain other characters have POSIX-BC values, PCRE2 makes \c? generate 95; otherwise it generates 255. - After \0 up to two further octal digits are read. If there are fewer - than two digits, just those that are present are used. Thus the + After \0 up to two further octal digits are read. If there are fewer + than two digits, just those that are present are used. Thus the sequence \0\x\015 specifies two binary zeros followed by a CR character (code value 13). Make sure you supply two digits after the initial zero if the pattern character that follows is itself an octal digit. - The escape \o must be followed by a sequence of octal digits, enclosed - in braces. An error occurs if this is not the case. This escape is a - recent addition to Perl; it provides way of specifying character code - points as octal numbers greater than 0777, and it also allows octal + The escape \o must be followed by a sequence of octal digits, enclosed + in braces. An error occurs if this is not the case. This escape is a + recent addition to Perl; it provides way of specifying character code + points as octal numbers greater than 0777, and it also allows octal numbers and backreferences to be unambiguously specified. For greater clarity and unambiguity, it is best to avoid following \ by @@ -6470,16 +6494,16 @@ BACKSLASH Outside a character class, PCRE2 reads the digit and any following dig- its as a decimal number. If the number is less than 10, begins with the - digit 8 or 9, or if there are at least that many previous capture - groups in the expression, the entire sequence is taken as a backrefer- - ence. A description of how this works is given later, following the - discussion of parenthesized groups. Otherwise, up to three octal dig- + digit 8 or 9, or if there are at least that many previous capture + groups in the expression, the entire sequence is taken as a backrefer- + ence. A description of how this works is given later, following the + discussion of parenthesized groups. Otherwise, up to three octal dig- its are read to form a character code. - Inside a character class, PCRE2 handles \8 and \9 as the literal char- - acters "8" and "9", and otherwise reads up to three octal digits fol- + Inside a character class, PCRE2 handles \8 and \9 as the literal char- + acters "8" and "9", and otherwise reads up to three octal digits fol- lowing the backslash, using them to generate a data character. Any sub- - sequent digits stand for themselves. For example, outside a character + sequent digits stand for themselves. For example, outside a character class: \040 is another way of writing an ASCII space @@ -6496,13 +6520,13 @@ BACKSLASH the value 255 (decimal) \81 is always a backreference - Note that octal values of 100 or greater that are specified using this - syntax must not be introduced by a leading zero, because no more than + Note that octal values of 100 or greater that are specified using this + syntax must not be introduced by a leading zero, because no more than three octal digits are ever read. Constraints on character values - Characters that are specified using octal or hexadecimal numbers are + Characters that are specified using octal or hexadecimal numbers are limited to certain values, as follows: 8-bit non-UTF mode no greater than 0xff @@ -6511,45 +6535,45 @@ BACKSLASH All UTF modes no greater than 0x10ffff and a valid code point Invalid Unicode code points are all those in the range 0xd800 to 0xdfff - (the so-called "surrogate" code points). The check for these can be - disabled by the caller of pcre2_compile() by setting the option - PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES. However, this is possible only in - UTF-8 and UTF-32 modes, because these values are not representable in + (the so-called "surrogate" code points). The check for these can be + disabled by the caller of pcre2_compile() by setting the option + PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES. However, this is possible only in + UTF-8 and UTF-32 modes, because these values are not representable in UTF-16. Escape sequences in character classes All the sequences that define a single character value can be used both - inside and outside character classes. In addition, inside a character + inside and outside character classes. In addition, inside a character class, \b is interpreted as the backspace character (hex 08). When not followed by an opening brace, \N is not allowed in a character - class. \B, \R, and \X are not special inside a character class. Like - other unrecognized alphabetic escape sequences, they cause an error. + class. \B, \R, and \X are not special inside a character class. Like + other unrecognized alphabetic escape sequences, they cause an error. Outside a character class, these sequences have different meanings. Unsupported escape sequences - In Perl, the sequences \F, \l, \L, \u, and \U are recognized by its - string handler and used to modify the case of following characters. By - default, PCRE2 does not support these escape sequences in patterns. + In Perl, the sequences \F, \l, \L, \u, and \U are recognized by its + string handler and used to modify the case of following characters. By + default, PCRE2 does not support these escape sequences in patterns. However, if either of the PCRE2_ALT_BSUX or PCRE2_EXTRA_ALT_BSUX - options is set, \U matches a "U" character, and \u can be used to + options is set, \U matches a "U" character, and \u can be used to define a character by code point, as described above. Absolute and relative backreferences - The sequence \g followed by a signed or unsigned number, optionally - enclosed in braces, is an absolute or relative backreference. A named - backreference can be coded as \g{name}. Backreferences are discussed + The sequence \g followed by a signed or unsigned number, optionally + enclosed in braces, is an absolute or relative backreference. A named + backreference can be coded as \g{name}. Backreferences are discussed later, following the discussion of parenthesized groups. Absolute and relative subroutine calls - For compatibility with Oniguruma, the non-Perl syntax \g followed by a + For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or a number enclosed either in angle brackets or single quotes, is - an alternative syntax for referencing a capture group as a subroutine. - Details are discussed later. Note that \g{...} (Perl syntax) and + an alternative syntax for referencing a capture group as a subroutine. + Details are discussed later. Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not synonymous. The former is a backref- erence; the latter is a subroutine call. @@ -6569,58 +6593,58 @@ BACKSLASH \w any "word" character \W any "non-word" character - The \N escape sequence has the same meaning as the "." metacharacter - when PCRE2_DOTALL is not set, but setting PCRE2_DOTALL does not change + The \N escape sequence has the same meaning as the "." metacharacter + when PCRE2_DOTALL is not set, but setting PCRE2_DOTALL does not change the meaning of \N. Note that when \N is followed by an opening brace it has a different meaning. See the section entitled "Non-printing charac- - ters" above for details. Perl also uses \N{name} to specify characters + ters" above for details. Perl also uses \N{name} to specify characters by Unicode name; PCRE2 does not support this. - Each pair of lower and upper case escape sequences partitions the com- - plete set of characters into two disjoint sets. Any given character - matches one, and only one, of each pair. The sequences can appear both - inside and outside character classes. They each match one character of - the appropriate type. If the current matching point is at the end of - the subject string, all of them fail, because there is no character to + Each pair of lower and upper case escape sequences partitions the com- + plete set of characters into two disjoint sets. Any given character + matches one, and only one, of each pair. The sequences can appear both + inside and outside character classes. They each match one character of + the appropriate type. If the current matching point is at the end of + the subject string, all of them fail, because there is no character to match. - The default \s characters are HT (9), LF (10), VT (11), FF (12), CR - (13), and space (32), which are defined as white space in the "C" + The default \s characters are HT (9), LF (10), VT (11), FF (12), CR + (13), and space (32), which are defined as white space in the "C" locale. This list may vary if locale-specific matching is taking place. - For example, in some locales the "non-breaking space" character (\xA0) + For example, in some locales the "non-breaking space" character (\xA0) is recognized as white space, and in others the VT character is not. - A "word" character is an underscore or any character that is a letter - or digit. By default, the definition of letters and digits is con- + A "word" character is an underscore or any character that is a letter + or digit. By default, the definition of letters and digits is con- trolled by PCRE2's low-valued character tables, and may vary if locale- specific matching is taking place (see "Locale support" in the pcre2api - page). For example, in a French locale such as "fr_FR" in Unix-like - systems, or "french" in Windows, some character codes greater than 127 - are used for accented letters, and these are then matched by \w. The + page). For example, in a French locale such as "fr_FR" in Unix-like + systems, or "french" in Windows, some character codes greater than 127 + are used for accented letters, and these are then matched by \w. The use of locales with Unicode is discouraged. - By default, characters whose code points are greater than 127 never + By default, characters whose code points are greater than 127 never match \d, \s, or \w, and always match \D, \S, and \W, although this may - be different for characters in the range 128-255 when locale-specific - matching is happening. These escape sequences retain their original - meanings from before Unicode support was available, mainly for effi- - ciency reasons. If the PCRE2_UCP option is set, the behaviour is - changed so that Unicode properties are used to determine character + be different for characters in the range 128-255 when locale-specific + matching is happening. These escape sequences retain their original + meanings from before Unicode support was available, mainly for effi- + ciency reasons. If the PCRE2_UCP option is set, the behaviour is + changed so that Unicode properties are used to determine character types, as follows: \d any character that matches \p{Nd} (decimal digit) \s any character that matches \p{Z} or \h or \v \w any character that matches \p{L} or \p{N}, plus underscore - The upper case escapes match the inverse sets of characters. Note that - \d matches only decimal digits, whereas \w matches any Unicode digit, + The upper case escapes match the inverse sets of characters. Note that + \d matches only decimal digits, whereas \w matches any Unicode digit, as well as any Unicode letter, and underscore. Note also that PCRE2_UCP - affects \b, and \B because they are defined in terms of \w and \W. + affects \b, and \B because they are defined in terms of \w and \W. Matching these sequences is noticeably slower when PCRE2_UCP is set. - The sequences \h, \H, \v, and \V, in contrast to the other sequences, - which match only ASCII characters by default, always match a specific - list of code points, whether or not PCRE2_UCP is set. The horizontal + The sequences \h, \H, \v, and \V, in contrast to the other sequences, + which match only ASCII characters by default, always match a specific + list of code points, whether or not PCRE2_UCP is set. The horizontal space characters are: U+0009 Horizontal tab (HT) @@ -6653,36 +6677,36 @@ BACKSLASH U+2028 Line separator U+2029 Paragraph separator - In 8-bit, non-UTF-8 mode, only the characters with code points less + In 8-bit, non-UTF-8 mode, only the characters with code points less than 256 are relevant. Newline sequences - Outside a character class, by default, the escape sequence \R matches - any Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent + Outside a character class, by default, the escape sequence \R matches + any Unicode newline sequence. In 8-bit non-UTF-8 mode \R is equivalent to the following: (?>\r\n|\n|\x0b|\f|\r|\x85) - This is an example of an "atomic group", details of which are given + This is an example of an "atomic group", details of which are given below. This particular group matches either the two-character sequence - CR followed by LF, or one of the single characters LF (linefeed, - U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car- - riage return, U+000D), or NEL (next line, U+0085). Because this is an - atomic group, the two-character sequence is treated as a single unit + CR followed by LF, or one of the single characters LF (linefeed, + U+000A), VT (vertical tab, U+000B), FF (form feed, U+000C), CR (car- + riage return, U+000D), or NEL (next line, U+0085). Because this is an + atomic group, the two-character sequence is treated as a single unit that cannot be split. In other modes, two additional characters whose code points are greater than 255 are added: LS (line separator, U+2028) and PS (paragraph sepa- - rator, U+2029). Unicode support is not needed for these characters to + rator, U+2029). Unicode support is not needed for these characters to be recognized. It is possible to restrict \R to match only CR, LF, or CRLF (instead of - the complete set of Unicode line endings) by setting the option - PCRE2_BSR_ANYCRLF at compile time. (BSR is an abbrevation for "back- + the complete set of Unicode line endings) by setting the option + PCRE2_BSR_ANYCRLF at compile time. (BSR is an abbrevation for "back- slash R".) This can be made the default when PCRE2 is built; if this is - the case, the other behaviour can be requested via the PCRE2_BSR_UNI- - CODE option. It is also possible to specify these settings by starting + the case, the other behaviour can be requested via the PCRE2_BSR_UNI- + CODE option. It is also possible to specify these settings by starting a pattern string with one of the following sequences: (*BSR_ANYCRLF) CR, LF, or CRLF only @@ -6690,27 +6714,27 @@ BACKSLASH These override the default and the options given to the compiling func- tion. Note that these special settings, which are not Perl-compatible, - are recognized only at the very start of a pattern, and that they must - be in upper case. If more than one of them is present, the last one is - used. They can be combined with a change of newline convention; for + are recognized only at the very start of a pattern, and that they must + be in upper case. If more than one of them is present, the last one is + used. They can be combined with a change of newline convention; for example, a pattern can start with: (*ANY)(*BSR_ANYCRLF) - They can also be combined with the (*UTF) or (*UCP) special sequences. - Inside a character class, \R is treated as an unrecognized escape + They can also be combined with the (*UTF) or (*UCP) special sequences. + Inside a character class, \R is treated as an unrecognized escape sequence, and causes an error. Unicode character properties - When PCRE2 is built with Unicode support (the default), three addi- - tional escape sequences that match characters with specific properties + When PCRE2 is built with Unicode support (the default), three addi- + tional escape sequences that match characters with specific properties are available. They can be used in any mode, though in 8-bit and 16-bit - non-UTF modes these sequences are of course limited to testing charac- - ters whose code points are less than U+0100 and U+10000, respectively. - In 32-bit non-UTF mode, code points greater than 0x10ffff (the Unicode - limit) may be encountered. These are all treated as being in the - Unknown script and with an unassigned type. The extra escape sequences + non-UTF modes these sequences are of course limited to testing charac- + ters whose code points are less than U+0100 and U+10000, respectively. + In 32-bit non-UTF mode, code points greater than 0x10ffff (the Unicode + limit) may be encountered. These are all treated as being in the + Unknown script and with an unassigned type. The extra escape sequences are: \p{xx} a character with the xx property @@ -6718,15 +6742,15 @@ BACKSLASH \X a Unicode extended grapheme cluster The property names represented by xx above are case-sensitive. There is - support for Unicode script names, Unicode general category properties, - "Any", which matches any character (including newline), and some spe- - cial PCRE2 properties (described in the next section). Other Perl + support for Unicode script names, Unicode general category properties, + "Any", which matches any character (including newline), and some spe- + cial PCRE2 properties (described in the next section). Other Perl properties such as "InMusicalSymbols" are not supported by PCRE2. Note - that \P{Any} does not match any characters, so always causes a match + that \P{Any} does not match any characters, so always causes a match failure. Sets of Unicode characters are defined as belonging to certain scripts. - A character from one of these sets can be matched using a script name. + A character from one of these sets can be matched using a script name. For example: \p{Greek} @@ -6734,43 +6758,43 @@ BACKSLASH Unassigned characters (and in non-UTF 32-bit mode, characters with code points greater than 0x10FFFF) are assigned the "Unknown" script. Others - that are not part of an identified script are lumped together as "Com- + that are not part of an identified script are lumped together as "Com- mon". The current list of scripts is: - Adlam, Ahom, Anatolian_Hieroglyphs, Arabic, Armenian, Avestan, Bali- - nese, Bamum, Bassa_Vah, Batak, Bengali, Bhaiksuki, Bopomofo, Brahmi, - Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Caucasian_Alba- - nian, Chakma, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, - Cyrillic, Deseret, Devanagari, Dogra, Duployan, Egyptian_Hieroglyphs, - Elbasan, Ethiopic, Georgian, Glagolitic, Gothic, Grantha, Greek, - Gujarati, Gunjala_Gondi, Gurmukhi, Han, Hangul, Hanifi_Rohingya, - Hanunoo, Hatran, Hebrew, Hiragana, Imperial_Aramaic, Inherited, - Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi, Kan- - nada, Katakana, Kayah_Li, Kharoshthi, Khmer, Khojki, Khudawadi, Lao, - Latin, Lepcha, Limbu, Linear_A, Linear_B, Lisu, Lycian, Lydian, Maha- - jani, Makasar, Malayalam, Mandaic, Manichaean, Marchen, Masaram_Gondi, + Adlam, Ahom, Anatolian_Hieroglyphs, Arabic, Armenian, Avestan, Bali- + nese, Bamum, Bassa_Vah, Batak, Bengali, Bhaiksuki, Bopomofo, Brahmi, + Braille, Buginese, Buhid, Canadian_Aboriginal, Carian, Caucasian_Alba- + nian, Chakma, Cham, Cherokee, Common, Coptic, Cuneiform, Cypriot, + Cyrillic, Deseret, Devanagari, Dogra, Duployan, Egyptian_Hieroglyphs, + Elbasan, Ethiopic, Georgian, Glagolitic, Gothic, Grantha, Greek, + Gujarati, Gunjala_Gondi, Gurmukhi, Han, Hangul, Hanifi_Rohingya, + Hanunoo, Hatran, Hebrew, Hiragana, Imperial_Aramaic, Inherited, + Inscriptional_Pahlavi, Inscriptional_Parthian, Javanese, Kaithi, Kan- + nada, Katakana, Kayah_Li, Kharoshthi, Khmer, Khojki, Khudawadi, Lao, + Latin, Lepcha, Limbu, Linear_A, Linear_B, Lisu, Lycian, Lydian, Maha- + jani, Makasar, Malayalam, Mandaic, Manichaean, Marchen, Masaram_Gondi, Medefaidrin, Meetei_Mayek, Mende_Kikakui, Meroitic_Cursive, - Meroitic_Hieroglyphs, Miao, Modi, Mongolian, Mro, Multani, Myanmar, - Nabataean, New_Tai_Lue, Newa, Nko, Nushu, Ogham, Ol_Chiki, Old_Hungar- - ian, Old_Italic, Old_North_Arabian, Old_Permic, Old_Persian, Old_Sog- - dian, Old_South_Arabian, Old_Turkic, Oriya, Osage, Osmanya, + Meroitic_Hieroglyphs, Miao, Modi, Mongolian, Mro, Multani, Myanmar, + Nabataean, New_Tai_Lue, Newa, Nko, Nushu, Ogham, Ol_Chiki, Old_Hungar- + ian, Old_Italic, Old_North_Arabian, Old_Permic, Old_Persian, Old_Sog- + dian, Old_South_Arabian, Old_Turkic, Oriya, Osage, Osmanya, Pahawh_Hmong, Palmyrene, Pau_Cin_Hau, Phags_Pa, Phoenician, - Psalter_Pahlavi, Rejang, Runic, Samaritan, Saurashtra, Sharada, Sha- - vian, Siddham, SignWriting, Sinhala, Sogdian, Sora_Sompeng, Soyombo, - Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, - Tai_Viet, Takri, Tamil, Tangut, Telugu, Thaana, Thai, Tibetan, Tifi- - nagh, Tirhuta, Ugaritic, Unknown, Vai, Warang_Citi, Yi, Zan- + Psalter_Pahlavi, Rejang, Runic, Samaritan, Saurashtra, Sharada, Sha- + vian, Siddham, SignWriting, Sinhala, Sogdian, Sora_Sompeng, Soyombo, + Sundanese, Syloti_Nagri, Syriac, Tagalog, Tagbanwa, Tai_Le, Tai_Tham, + Tai_Viet, Takri, Tamil, Tangut, Telugu, Thaana, Thai, Tibetan, Tifi- + nagh, Tirhuta, Ugaritic, Unknown, Vai, Warang_Citi, Yi, Zan- abazar_Square. Each character has exactly one Unicode general category property, spec- - ified by a two-letter abbreviation. For compatibility with Perl, nega- - tion can be specified by including a circumflex between the opening - brace and the property name. For example, \p{^Lu} is the same as + ified by a two-letter abbreviation. For compatibility with Perl, nega- + tion can be specified by including a circumflex between the opening + brace and the property name. For example, \p{^Lu} is the same as \P{Lu}. If only one letter is specified with \p or \P, it includes all the gen- - eral category properties that start with that letter. In this case, in - the absence of negation, the curly brackets in the escape sequence are + eral category properties that start with that letter. In this case, in + the absence of negation, the curly brackets in the escape sequence are optional; these two examples have the same effect: \p{L} @@ -6822,88 +6846,88 @@ BACKSLASH Zp Paragraph separator Zs Space separator - The special property L& is also supported: it matches a character that - has the Lu, Ll, or Lt property, in other words, a letter that is not + The special property L& is also supported: it matches a character that + has the Lu, Ll, or Lt property, in other words, a letter that is not classified as a modifier or "other". - The Cs (Surrogate) property applies only to characters whose code - points are in the range U+D800 to U+DFFF. These characters are no dif- - ferent to any other character when PCRE2 is not in UTF mode (using the - 16-bit or 32-bit library). However, they are not valid in Unicode + The Cs (Surrogate) property applies only to characters whose code + points are in the range U+D800 to U+DFFF. These characters are no dif- + ferent to any other character when PCRE2 is not in UTF mode (using the + 16-bit or 32-bit library). However, they are not valid in Unicode strings and so cannot be tested by PCRE2 in UTF mode, unless UTF valid- - ity checking has been turned off (see the discussion of + ity checking has been turned off (see the discussion of PCRE2_NO_UTF_CHECK in the pcre2api page). - The long synonyms for property names that Perl supports (such as - \p{Letter}) are not supported by PCRE2, nor is it permitted to prefix + The long synonyms for property names that Perl supports (such as + \p{Letter}) are not supported by PCRE2, nor is it permitted to prefix any of these properties with "Is". No character that is in the Unicode table has the Cn (unassigned) prop- erty. Instead, this property is assumed for any code point that is not in the Unicode table. - Specifying caseless matching does not affect these escape sequences. - For example, \p{Lu} always matches only upper case letters. This is + Specifying caseless matching does not affect these escape sequences. + For example, \p{Lu} always matches only upper case letters. This is different from the behaviour of current versions of Perl. - Matching characters by Unicode property is not fast, because PCRE2 has - to do a multistage table lookup in order to find a character's prop- + Matching characters by Unicode property is not fast, because PCRE2 has + to do a multistage table lookup in order to find a character's prop- erty. That is why the traditional escape sequences such as \d and \w do - not use Unicode properties in PCRE2 by default, though you can make - them do so by setting the PCRE2_UCP option or by starting the pattern + not use Unicode properties in PCRE2 by default, though you can make + them do so by setting the PCRE2_UCP option or by starting the pattern with (*UCP). Extended grapheme clusters - The \X escape matches any number of Unicode characters that form an + The \X escape matches any number of Unicode characters that form an "extended grapheme cluster", and treats the sequence as an atomic group - (see below). Unicode supports various kinds of composite character by - giving each character a grapheme breaking property, and having rules + (see below). Unicode supports various kinds of composite character by + giving each character a grapheme breaking property, and having rules that use these properties to define the boundaries of extended grapheme - clusters. The rules are defined in Unicode Standard Annex 29, "Unicode - Text Segmentation". Unicode 11.0.0 abandoned the use of some previous - properties that had been used for emojis. Instead it introduced vari- - ous emoji-specific properties. PCRE2 uses only the Extended Picto- + clusters. The rules are defined in Unicode Standard Annex 29, "Unicode + Text Segmentation". Unicode 11.0.0 abandoned the use of some previous + properties that had been used for emojis. Instead it introduced vari- + ous emoji-specific properties. PCRE2 uses only the Extended Picto- graphic property. - \X always matches at least one character. Then it decides whether to + \X always matches at least one character. Then it decides whether to add additional characters according to the following rules for ending a cluster: 1. End at the end of the subject string. - 2. Do not end between CR and LF; otherwise end after any control char- + 2. Do not end between CR and LF; otherwise end after any control char- acter. - 3. Do not break Hangul (a Korean script) syllable sequences. Hangul - characters are of five types: L, V, T, LV, and LVT. An L character may - be followed by an L, V, LV, or LVT character; an LV or V character may + 3. Do not break Hangul (a Korean script) syllable sequences. Hangul + characters are of five types: L, V, T, LV, and LVT. An L character may + be followed by an L, V, LV, or LVT character; an LV or V character may be followed by a V or T character; an LVT or T character may be follwed only by a T character. - 4. Do not end before extending characters or spacing marks or the - "zero-width joiner" character. Characters with the "mark" property + 4. Do not end before extending characters or spacing marks or the + "zero-width joiner" character. Characters with the "mark" property always have the "extend" grapheme breaking property. 5. Do not end after prepend characters. 6. Do not break within emoji modifier sequences or emoji zwj sequences. That is, do not break between characters with the Extended_Pictographic - property. Extend and ZWJ characters are allowed between the charac- + property. Extend and ZWJ characters are allowed between the charac- ters. - 7. Do not break within emoji flag sequences. That is, do not break - between regional indicator (RI) characters if there are an odd number + 7. Do not break within emoji flag sequences. That is, do not break + between regional indicator (RI) characters if there are an odd number of RI characters before the break point. 8. Otherwise, end the cluster. PCRE2's additional properties - As well as the standard Unicode properties described above, PCRE2 sup- - ports four more that make it possible to convert traditional escape + As well as the standard Unicode properties described above, PCRE2 sup- + ports four more that make it possible to convert traditional escape sequences such as \w and \s to use Unicode properties. PCRE2 uses these - non-standard, non-Perl properties internally when PCRE2_UCP is set. + non-standard, non-Perl properties internally when PCRE2_UCP is set. However, they may also be used explicitly. These properties are: Xan Any alphanumeric character @@ -6911,69 +6935,69 @@ BACKSLASH Xsp Any Perl space character Xwd Any Perl "word" character - Xan matches characters that have either the L (letter) or the N (num- - ber) property. Xps matches the characters tab, linefeed, vertical tab, - form feed, or carriage return, and any other character that has the Z - (separator) property. Xsp is the same as Xps; in PCRE1 it used to - exclude vertical tab, for Perl compatibility, but Perl changed. Xwd + Xan matches characters that have either the L (letter) or the N (num- + ber) property. Xps matches the characters tab, linefeed, vertical tab, + form feed, or carriage return, and any other character that has the Z + (separator) property. Xsp is the same as Xps; in PCRE1 it used to + exclude vertical tab, for Perl compatibility, but Perl changed. Xwd matches the same characters as Xan, plus underscore. - There is another non-standard property, Xuc, which matches any charac- - ter that can be represented by a Universal Character Name in C++ and - other programming languages. These are the characters $, @, ` (grave - accent), and all characters with Unicode code points greater than or - equal to U+00A0, except for the surrogates U+D800 to U+DFFF. Note that - most base (ASCII) characters are excluded. (Universal Character Names - are of the form \uHHHH or \UHHHHHHHH where H is a hexadecimal digit. + There is another non-standard property, Xuc, which matches any charac- + ter that can be represented by a Universal Character Name in C++ and + other programming languages. These are the characters $, @, ` (grave + accent), and all characters with Unicode code points greater than or + equal to U+00A0, except for the surrogates U+D800 to U+DFFF. Note that + most base (ASCII) characters are excluded. (Universal Character Names + are of the form \uHHHH or \UHHHHHHHH where H is a hexadecimal digit. Note that the Xuc property does not match these sequences but the char- acters that they represent.) Resetting the match start - In normal use, the escape sequence \K causes any previously matched - characters not to be included in the final matched sequence that is + In normal use, the escape sequence \K causes any previously matched + characters not to be included in the final matched sequence that is returned. For example, the pattern: foo\Kbar - matches "foobar", but reports that it has matched "bar". \K does not + matches "foobar", but reports that it has matched "bar". \K does not interact with anchoring in any way. The pattern: ^foo\Kbar - matches only when the subject begins with "foobar" (in single line - mode), though it again reports the matched string as "bar". This fea- - ture is similar to a lookbehind assertion (described below). However, - in this case, the part of the subject before the real match does not - have to be of fixed length, as lookbehind assertions do. The use of \K - does not interfere with the setting of captured substrings. For exam- + matches only when the subject begins with "foobar" (in single line + mode), though it again reports the matched string as "bar". This fea- + ture is similar to a lookbehind assertion (described below). However, + in this case, the part of the subject before the real match does not + have to be of fixed length, as lookbehind assertions do. The use of \K + does not interfere with the setting of captured substrings. For exam- ple, when the pattern (foo)\Kbar matches "foobar", the first substring is still set to "foo". - Perl documents that the use of \K within assertions is "not well - defined". In PCRE2, \K is acted upon when it occurs inside positive - assertions, but is ignored in negative assertions. Note that when a - pattern such as (?=ab\K) matches, the reported start of the match can - be greater than the end of the match. Using \K in a lookbehind asser- - tion at the start of a pattern can also lead to odd effects. For exam- + Perl documents that the use of \K within assertions is "not well + defined". In PCRE2, \K is acted upon when it occurs inside positive + assertions, but is ignored in negative assertions. Note that when a + pattern such as (?=ab\K) matches, the reported start of the match can + be greater than the end of the match. Using \K in a lookbehind asser- + tion at the start of a pattern can also lead to odd effects. For exam- ple, consider this pattern: (?<=\Kfoo)bar - If the subject is "foobar", a call to pcre2_match() with a starting - offset of 3 succeeds and reports the matching string as "foobar", that - is, the start of the reported match is earlier than where the match + If the subject is "foobar", a call to pcre2_match() with a starting + offset of 3 succeeds and reports the matching string as "foobar", that + is, the start of the reported match is earlier than where the match started. Simple assertions - The final use of backslash is for certain simple assertions. An asser- - tion specifies a condition that has to be met at a particular point in - a match, without consuming any characters from the subject string. The - use of groups for more complicated assertions is described below. The + The final use of backslash is for certain simple assertions. An asser- + tion specifies a condition that has to be met at a particular point in + a match, without consuming any characters from the subject string. The + use of groups for more complicated assertions is described below. The backslashed assertions are: \b matches at a word boundary @@ -6984,191 +7008,191 @@ BACKSLASH \z matches only at the end of the subject \G matches at the first matching position in the subject - Inside a character class, \b has a different meaning; it matches the - backspace character. If any other of these assertions appears in a + Inside a character class, \b has a different meaning; it matches the + backspace character. If any other of these assertions appears in a character class, an "invalid escape sequence" error is generated. - A word boundary is a position in the subject string where the current - character and the previous character do not both match \w or \W (i.e. - one matches \w and the other matches \W), or the start or end of the - string if the first or last character matches \w, respectively. When - PCRE2 is built with Unicode support, the meanings of \w and \W can be - changed by setting the PCRE2_UCP option. When this is done, it also - affects \b and \B. Neither PCRE2 nor Perl has a separate "start of - word" or "end of word" metasequence. However, whatever follows \b nor- + A word boundary is a position in the subject string where the current + character and the previous character do not both match \w or \W (i.e. + one matches \w and the other matches \W), or the start or end of the + string if the first or last character matches \w, respectively. When + PCRE2 is built with Unicode support, the meanings of \w and \W can be + changed by setting the PCRE2_UCP option. When this is done, it also + affects \b and \B. Neither PCRE2 nor Perl has a separate "start of + word" or "end of word" metasequence. However, whatever follows \b nor- mally determines which it is. For example, the fragment \ba matches "a" at the start of a word. - The \A, \Z, and \z assertions differ from the traditional circumflex + The \A, \Z, and \z assertions differ from the traditional circumflex and dollar (described in the next section) in that they only ever match - at the very start and end of the subject string, whatever options are - set. Thus, they are independent of multiline mode. These three asser- - tions are not affected by the PCRE2_NOTBOL or PCRE2_NOTEOL options, - which affect only the behaviour of the circumflex and dollar metachar- - acters. However, if the startoffset argument of pcre2_match() is non- - zero, indicating that matching is to start at a point other than the - beginning of the subject, \A can never match. The difference between - \Z and \z is that \Z matches before a newline at the end of the string + at the very start and end of the subject string, whatever options are + set. Thus, they are independent of multiline mode. These three asser- + tions are not affected by the PCRE2_NOTBOL or PCRE2_NOTEOL options, + which affect only the behaviour of the circumflex and dollar metachar- + acters. However, if the startoffset argument of pcre2_match() is non- + zero, indicating that matching is to start at a point other than the + beginning of the subject, \A can never match. The difference between + \Z and \z is that \Z matches before a newline at the end of the string as well as at the very end, whereas \z matches only at the end. - The \G assertion is true only when the current matching position is at - the start point of the matching process, as specified by the startoff- - set argument of pcre2_match(). It differs from \A when the value of - startoffset is non-zero. By calling pcre2_match() multiple times with - appropriate arguments, you can mimic Perl's /g option, and it is in + The \G assertion is true only when the current matching position is at + the start point of the matching process, as specified by the startoff- + set argument of pcre2_match(). It differs from \A when the value of + startoffset is non-zero. By calling pcre2_match() multiple times with + appropriate arguments, you can mimic Perl's /g option, and it is in this kind of implementation where \G can be useful. - Note, however, that PCRE2's implementation of \G, being true at the - starting character of the matching process, is subtly different from - Perl's, which defines it as true at the end of the previous match. In - Perl, these can be different when the previously matched string was + Note, however, that PCRE2's implementation of \G, being true at the + starting character of the matching process, is subtly different from + Perl's, which defines it as true at the end of the previous match. In + Perl, these can be different when the previously matched string was empty. Because PCRE2 does just one match at a time, it cannot reproduce this behaviour. - If all the alternatives of a pattern begin with \G, the expression is + If all the alternatives of a pattern begin with \G, the expression is anchored to the starting match position, and the "anchored" flag is set in the compiled regular expression. CIRCUMFLEX AND DOLLAR - The circumflex and dollar metacharacters are zero-width assertions. - That is, they test for a particular condition being true without con- + The circumflex and dollar metacharacters are zero-width assertions. + That is, they test for a particular condition being true without con- suming any characters from the subject string. These two metacharacters - are concerned with matching the starts and ends of lines. If the new- - line convention is set so that only the two-character sequence CRLF is - recognized as a newline, isolated CR and LF characters are treated as + are concerned with matching the starts and ends of lines. If the new- + line convention is set so that only the two-character sequence CRLF is + recognized as a newline, isolated CR and LF characters are treated as ordinary data characters, and are not recognized as newlines. Outside a character class, in the default matching mode, the circumflex - character is an assertion that is true only if the current matching - point is at the start of the subject string. If the startoffset argu- - ment of pcre2_match() is non-zero, or if PCRE2_NOTBOL is set, circum- - flex can never match if the PCRE2_MULTILINE option is unset. Inside a - character class, circumflex has an entirely different meaning (see + character is an assertion that is true only if the current matching + point is at the start of the subject string. If the startoffset argu- + ment of pcre2_match() is non-zero, or if PCRE2_NOTBOL is set, circum- + flex can never match if the PCRE2_MULTILINE option is unset. Inside a + character class, circumflex has an entirely different meaning (see below). - Circumflex need not be the first character of the pattern if a number - of alternatives are involved, but it should be the first thing in each - alternative in which it appears if the pattern is ever to match that - branch. If all possible alternatives start with a circumflex, that is, - if the pattern is constrained to match only at the start of the sub- - ject, it is said to be an "anchored" pattern. (There are also other + Circumflex need not be the first character of the pattern if a number + of alternatives are involved, but it should be the first thing in each + alternative in which it appears if the pattern is ever to match that + branch. If all possible alternatives start with a circumflex, that is, + if the pattern is constrained to match only at the start of the sub- + ject, it is said to be an "anchored" pattern. (There are also other constructs that can cause a pattern to be anchored.) - The dollar character is an assertion that is true only if the current - matching point is at the end of the subject string, or immediately - before a newline at the end of the string (by default), unless + The dollar character is an assertion that is true only if the current + matching point is at the end of the subject string, or immediately + before a newline at the end of the string (by default), unless PCRE2_NOTEOL is set. Note, however, that it does not actually match the newline. Dollar need not be the last character of the pattern if a num- ber of alternatives are involved, but it should be the last item in any - branch in which it appears. Dollar has no special meaning in a charac- + branch in which it appears. Dollar has no special meaning in a charac- ter class. - The meaning of dollar can be changed so that it matches only at the - very end of the string, by setting the PCRE2_DOLLAR_ENDONLY option at + The meaning of dollar can be changed so that it matches only at the + very end of the string, by setting the PCRE2_DOLLAR_ENDONLY option at compile time. This does not affect the \Z assertion. The meanings of the circumflex and dollar metacharacters are changed if - the PCRE2_MULTILINE option is set. When this is the case, a dollar - character matches before any newlines in the string, as well as at the - very end, and a circumflex matches immediately after internal newlines - as well as at the start of the subject string. It does not match after - a newline that ends the string, for compatibility with Perl. However, + the PCRE2_MULTILINE option is set. When this is the case, a dollar + character matches before any newlines in the string, as well as at the + very end, and a circumflex matches immediately after internal newlines + as well as at the start of the subject string. It does not match after + a newline that ends the string, for compatibility with Perl. However, this can be changed by setting the PCRE2_ALT_CIRCUMFLEX option. - For example, the pattern /^abc$/ matches the subject string "def\nabc" - (where \n represents a newline) in multiline mode, but not otherwise. - Consequently, patterns that are anchored in single line mode because - all branches start with ^ are not anchored in multiline mode, and a - match for circumflex is possible when the startoffset argument of - pcre2_match() is non-zero. The PCRE2_DOLLAR_ENDONLY option is ignored + For example, the pattern /^abc$/ matches the subject string "def\nabc" + (where \n represents a newline) in multiline mode, but not otherwise. + Consequently, patterns that are anchored in single line mode because + all branches start with ^ are not anchored in multiline mode, and a + match for circumflex is possible when the startoffset argument of + pcre2_match() is non-zero. The PCRE2_DOLLAR_ENDONLY option is ignored if PCRE2_MULTILINE is set. - When the newline convention (see "Newline conventions" below) recog- - nizes the two-character sequence CRLF as a newline, this is preferred, - even if the single characters CR and LF are also recognized as new- - lines. For example, if the newline convention is "any", a multiline - mode circumflex matches before "xyz" in the string "abc\r\nxyz" rather - than after CR, even though CR on its own is a valid newline. (It also + When the newline convention (see "Newline conventions" below) recog- + nizes the two-character sequence CRLF as a newline, this is preferred, + even if the single characters CR and LF are also recognized as new- + lines. For example, if the newline convention is "any", a multiline + mode circumflex matches before "xyz" in the string "abc\r\nxyz" rather + than after CR, even though CR on its own is a valid newline. (It also matches at the very start of the string, of course.) - Note that the sequences \A, \Z, and \z can be used to match the start - and end of the subject in both modes, and if all branches of a pattern - start with \A it is always anchored, whether or not PCRE2_MULTILINE is + Note that the sequences \A, \Z, and \z can be used to match the start + and end of the subject in both modes, and if all branches of a pattern + start with \A it is always anchored, whether or not PCRE2_MULTILINE is set. FULL STOP (PERIOD, DOT) AND \N Outside a character class, a dot in the pattern matches any one charac- - ter in the subject string except (by default) a character that signi- + ter in the subject string except (by default) a character that signi- fies the end of a line. - When a line ending is defined as a single character, dot never matches - that character; when the two-character sequence CRLF is used, dot does - not match CR if it is immediately followed by LF, but otherwise it - matches all characters (including isolated CRs and LFs). When any Uni- - code line endings are being recognized, dot does not match CR or LF or + When a line ending is defined as a single character, dot never matches + that character; when the two-character sequence CRLF is used, dot does + not match CR if it is immediately followed by LF, but otherwise it + matches all characters (including isolated CRs and LFs). When any Uni- + code line endings are being recognized, dot does not match CR or LF or any of the other line ending characters. - The behaviour of dot with regard to newlines can be changed. If the - PCRE2_DOTALL option is set, a dot matches any one character, without - exception. If the two-character sequence CRLF is present in the sub- + The behaviour of dot with regard to newlines can be changed. If the + PCRE2_DOTALL option is set, a dot matches any one character, without + exception. If the two-character sequence CRLF is present in the sub- ject string, it takes two dots to match it. - The handling of dot is entirely independent of the handling of circum- - flex and dollar, the only relationship being that they both involve + The handling of dot is entirely independent of the handling of circum- + flex and dollar, the only relationship being that they both involve newlines. Dot has no special meaning in a character class. - The escape sequence \N when not followed by an opening brace behaves - like a dot, except that it is not affected by the PCRE2_DOTALL option. - In other words, it matches any character except one that signifies the + The escape sequence \N when not followed by an opening brace behaves + like a dot, except that it is not affected by the PCRE2_DOTALL option. + In other words, it matches any character except one that signifies the end of a line. When \N is followed by an opening brace it has a different meaning. See - the section entitled "Non-printing characters" above for details. Perl - also uses \N{name} to specify characters by Unicode name; PCRE2 does + the section entitled "Non-printing characters" above for details. Perl + also uses \N{name} to specify characters by Unicode name; PCRE2 does not support this. MATCHING A SINGLE CODE UNIT - Outside a character class, the escape sequence \C matches any one code - unit, whether or not a UTF mode is set. In the 8-bit library, one code - unit is one byte; in the 16-bit library it is a 16-bit unit; in the - 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches - line-ending characters. The feature is provided in Perl in order to + Outside a character class, the escape sequence \C matches any one code + unit, whether or not a UTF mode is set. In the 8-bit library, one code + unit is one byte; in the 16-bit library it is a 16-bit unit; in the + 32-bit library it is a 32-bit unit. Unlike a dot, \C always matches + line-ending characters. The feature is provided in Perl in order to match individual bytes in UTF-8 mode, but it is unclear how it can use- fully be used. - Because \C breaks up characters into individual code units, matching - one unit with \C in UTF-8 or UTF-16 mode means that the rest of the - string may start with a malformed UTF character. This has undefined + Because \C breaks up characters into individual code units, matching + one unit with \C in UTF-8 or UTF-16 mode means that the rest of the + string may start with a malformed UTF character. This has undefined results, because PCRE2 assumes that it is matching character by charac- - ter in a valid UTF string (by default it checks the subject string's - validity at the start of processing unless the PCRE2_NO_UTF_CHECK - option is used). + ter in a valid UTF string (by default it checks the subject string's + validity at the start of processing unless the PCRE2_NO_UTF_CHECK or + PCRE2_MATCH_INVALID_UTF option is used). - An application can lock out the use of \C by setting the - PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also + An application can lock out the use of \C by setting the + PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also possible to build PCRE2 with the use of \C permanently disabled. - PCRE2 does not allow \C to appear in lookbehind assertions (described - below) in UTF-8 or UTF-16 modes, because this would make it impossible - to calculate the length of the lookbehind. Neither the alternative + PCRE2 does not allow \C to appear in lookbehind assertions (described + below) in UTF-8 or UTF-16 modes, because this would make it impossible + to calculate the length of the lookbehind. Neither the alternative matching function pcre2_dfa_match() nor the JIT optimizer support \C in these UTF modes. The former gives a match-time error; the latter fails to optimize and so the match is always run using the interpreter. - In the 32-bit library, however, \C is always supported (when not - explicitly locked out) because it always matches a single code unit, + In the 32-bit library, however, \C is always supported (when not + explicitly locked out) because it always matches a single code unit, whether or not UTF-32 is specified. In general, the \C escape sequence is best avoided. However, one way of - using it that avoids the problem of malformed UTF-8 or UTF-16 charac- - ters is to use a lookahead to check the length of the next character, - as in this pattern, which could be used with a UTF-8 string (ignore + using it that avoids the problem of malformed UTF-8 or UTF-16 charac- + ters is to use a lookahead to check the length of the next character, + as in this pattern, which could be used with a UTF-8 string (ignore white space and line breaks): (?| (?=[\x00-\x7f])(\C) | @@ -7176,11 +7200,11 @@ MATCHING A SINGLE CODE UNIT (?=[\x{800}-\x{ffff}])(\C)(\C)(\C) | (?=[\x{10000}-\x{1fffff}])(\C)(\C)(\C)(\C)) - In this example, a group that starts with (?| resets the capturing - parentheses numbers in each alternative (see "Duplicate Group Numbers" + In this example, a group that starts with (?| resets the capturing + parentheses numbers in each alternative (see "Duplicate Group Numbers" below). The assertions at the start of each branch check the next UTF-8 - character for values whose encoding uses 1, 2, 3, or 4 bytes, respec- - tively. The character's individual bytes are then captured by the + character for values whose encoding uses 1, 2, 3, or 4 bytes, respec- + tively. The character's individual bytes are then captured by the appropriate number of \C groups. @@ -7188,115 +7212,115 @@ SQUARE BRACKETS AND CHARACTER CLASSES An opening square bracket introduces a character class, terminated by a closing square bracket. A closing square bracket on its own is not spe- - cial by default. If a closing square bracket is required as a member + cial by default. If a closing square bracket is required as a member of the class, it should be the first data character in the class (after - an initial circumflex, if present) or escaped with a backslash. This - means that, by default, an empty class cannot be defined. However, if - the PCRE2_ALLOW_EMPTY_CLASS option is set, a closing square bracket at + an initial circumflex, if present) or escaped with a backslash. This + means that, by default, an empty class cannot be defined. However, if + the PCRE2_ALLOW_EMPTY_CLASS option is set, a closing square bracket at the start does end the (empty) class. - A character class matches a single character in the subject. A matched + A character class matches a single character in the subject. A matched character must be in the set of characters defined by the class, unless - the first character in the class definition is a circumflex, in which + the first character in the class definition is a circumflex, in which case the subject character must not be in the set defined by the class. - If a circumflex is actually required as a member of the class, ensure + If a circumflex is actually required as a member of the class, ensure it is not the first character, or escape it with a backslash. - For example, the character class [aeiou] matches any lower case vowel, - while [^aeiou] matches any character that is not a lower case vowel. + For example, the character class [aeiou] matches any lower case vowel, + while [^aeiou] matches any character that is not a lower case vowel. Note that a circumflex is just a convenient notation for specifying the - characters that are in the class by enumerating those that are not. A - class that starts with a circumflex is not an assertion; it still con- - sumes a character from the subject string, and therefore it fails if + characters that are in the class by enumerating those that are not. A + class that starts with a circumflex is not an assertion; it still con- + sumes a character from the subject string, and therefore it fails if the current pointer is at the end of the string. - Characters in a class may be specified by their code points using \o, - \x, or \N{U+hh..} in the usual way. When caseless matching is set, any - letters in a class represent both their upper case and lower case ver- - sions, so for example, a caseless [aeiou] matches "A" as well as "a", - and a caseless [^aeiou] does not match "A", whereas a caseful version + Characters in a class may be specified by their code points using \o, + \x, or \N{U+hh..} in the usual way. When caseless matching is set, any + letters in a class represent both their upper case and lower case ver- + sions, so for example, a caseless [aeiou] matches "A" as well as "a", + and a caseless [^aeiou] does not match "A", whereas a caseful version would. - Characters that might indicate line breaks are never treated in any - special way when matching character classes, whatever line-ending - sequence is in use, and whatever setting of the PCRE2_DOTALL and - PCRE2_MULTILINE options is used. A class such as [^a] always matches + Characters that might indicate line breaks are never treated in any + special way when matching character classes, whatever line-ending + sequence is in use, and whatever setting of the PCRE2_DOTALL and + PCRE2_MULTILINE options is used. A class such as [^a] always matches one of these characters. The generic character type escape sequences \d, \D, \h, \H, \p, \P, \s, - \S, \v, \V, \w, and \W may appear in a character class, and add the - characters that they match to the class. For example, [\dABCDEF] - matches any hexadecimal digit. In UTF modes, the PCRE2_UCP option - affects the meanings of \d, \s, \w and their upper case partners, just - as it does when they appear outside a character class, as described in - the section entitled "Generic character types" above. The escape - sequence \b has a different meaning inside a character class; it - matches the backspace character. The sequences \B, \R, and \X are not - special inside a character class. Like any other unrecognized escape - sequences, they cause an error. The same is true for \N when not fol- + \S, \v, \V, \w, and \W may appear in a character class, and add the + characters that they match to the class. For example, [\dABCDEF] + matches any hexadecimal digit. In UTF modes, the PCRE2_UCP option + affects the meanings of \d, \s, \w and their upper case partners, just + as it does when they appear outside a character class, as described in + the section entitled "Generic character types" above. The escape + sequence \b has a different meaning inside a character class; it + matches the backspace character. The sequences \B, \R, and \X are not + special inside a character class. Like any other unrecognized escape + sequences, they cause an error. The same is true for \N when not fol- lowed by an opening brace. - The minus (hyphen) character can be used to specify a range of charac- - ters in a character class. For example, [d-m] matches any letter - between d and m, inclusive. If a minus character is required in a - class, it must be escaped with a backslash or appear in a position - where it cannot be interpreted as indicating a range, typically as the + The minus (hyphen) character can be used to specify a range of charac- + ters in a character class. For example, [d-m] matches any letter + between d and m, inclusive. If a minus character is required in a + class, it must be escaped with a backslash or appear in a position + where it cannot be interpreted as indicating a range, typically as the first or last character in the class, or immediately after a range. For - example, [b-d-z] matches letters in the range b to d, a hyphen charac- + example, [b-d-z] matches letters in the range b to d, a hyphen charac- ter, or z. Perl treats a hyphen as a literal if it appears before or after a POSIX class (see below) or before or after a character type escape such as as - \d or \H. However, unless the hyphen is the last character in the - class, Perl outputs a warning in its warning mode, as this is most - likely a user error. As PCRE2 has no facility for warning, an error is + \d or \H. However, unless the hyphen is the last character in the + class, Perl outputs a warning in its warning mode, as this is most + likely a user error. As PCRE2 has no facility for warning, an error is given in these cases. It is not possible to have the literal character "]" as the end charac- - ter of a range. A pattern such as [W-]46] is interpreted as a class of - two characters ("W" and "-") followed by a literal string "46]", so it - would match "W46]" or "-46]". However, if the "]" is escaped with a - backslash it is interpreted as the end of range, so [W-\]46] is inter- - preted as a class containing a range followed by two other characters. - The octal or hexadecimal representation of "]" can also be used to end + ter of a range. A pattern such as [W-]46] is interpreted as a class of + two characters ("W" and "-") followed by a literal string "46]", so it + would match "W46]" or "-46]". However, if the "]" is escaped with a + backslash it is interpreted as the end of range, so [W-\]46] is inter- + preted as a class containing a range followed by two other characters. + The octal or hexadecimal representation of "]" can also be used to end a range. Ranges normally include all code points between the start and end char- - acters, inclusive. They can also be used for code points specified + acters, inclusive. They can also be used for code points specified numerically, for example [\000-\037]. Ranges can include any characters - that are valid for the current mode. In any UTF mode, the so-called - "surrogate" characters (those whose code points lie between 0xd800 and - 0xdfff inclusive) may not be specified explicitly by default (the - PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES option disables this check). How- + that are valid for the current mode. In any UTF mode, the so-called + "surrogate" characters (those whose code points lie between 0xd800 and + 0xdfff inclusive) may not be specified explicitly by default (the + PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES option disables this check). How- ever, ranges such as [\x{d7ff}-\x{e000}], which include the surrogates, are always permitted. - There is a special case in EBCDIC environments for ranges whose end + There is a special case in EBCDIC environments for ranges whose end points are both specified as literal letters in the same case. For com- - patibility with Perl, EBCDIC code points within the range that are not - letters are omitted. For example, [h-k] matches only four characters, + patibility with Perl, EBCDIC code points within the range that are not + letters are omitted. For example, [h-k] matches only four characters, even though the codes for h and k are 0x88 and 0x92, a range of 11 code - points. However, if the range is specified numerically, for example, + points. However, if the range is specified numerically, for example, [\x88-\x92] or [h-\x92], all code points are included. If a range that includes letters is used when caseless matching is set, it matches the letters in either case. For example, [W-c] is equivalent - to [][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if - character tables for a French locale are in use, [\xc8-\xcb] matches + to [][\\^_`wxyzabc], matched caselessly, and in a non-UTF mode, if + character tables for a French locale are in use, [\xc8-\xcb] matches accented E characters in both cases. - A circumflex can conveniently be used with the upper case character - types to specify a more restricted set of characters than the matching - lower case type. For example, the class [^\W_] matches any letter or + A circumflex can conveniently be used with the upper case character + types to specify a more restricted set of characters than the matching + lower case type. For example, the class [^\W_] matches any letter or digit, but not underscore, whereas [\w] includes underscore. A positive character class should be read as "something OR something OR ..." and a negative class as "NOT something AND NOT something AND NOT ...". - The only metacharacters that are recognized in character classes are - backslash, hyphen (only where it can be interpreted as specifying a - range), circumflex (only at the start), opening square bracket (only - when it can be interpreted as introducing a POSIX class name, or for a - special compatibility feature - see the next two sections), and the + The only metacharacters that are recognized in character classes are + backslash, hyphen (only where it can be interpreted as specifying a + range), circumflex (only at the start), opening square bracket (only + when it can be interpreted as introducing a POSIX class name, or for a + special compatibility feature - see the next two sections), and the terminating closing square bracket. However, escaping other non- alphanumeric characters does no harm. @@ -7304,7 +7328,7 @@ SQUARE BRACKETS AND CHARACTER CLASSES POSIX CHARACTER CLASSES Perl supports the POSIX notation for character classes. This uses names - enclosed by [: and :] within the enclosing square brackets. PCRE2 also + enclosed by [: and :] within the enclosing square brackets. PCRE2 also supports this notation. For example, [01[:alpha:]%] @@ -7327,13 +7351,13 @@ POSIX CHARACTER CLASSES word "word" characters (same as \w) xdigit hexadecimal digits - The default "space" characters are HT (9), LF (10), VT (11), FF (12), - CR (13), and space (32). If locale-specific matching is taking place, - the list of space characters may be different; there may be fewer or + The default "space" characters are HT (9), LF (10), VT (11), FF (12), + CR (13), and space (32). If locale-specific matching is taking place, + the list of space characters may be different; there may be fewer or more of them. "Space" and \s match the same set of characters. - The name "word" is a Perl extension, and "blank" is a GNU extension - from Perl 5.8. Another Perl extension is negation, which is indicated + The name "word" is a Perl extension, and "blank" is a GNU extension + from Perl 5.8. Another Perl extension is negation, which is indicated by a ^ character after the colon. For example, [12[:^digit:]] @@ -7344,9 +7368,9 @@ POSIX CHARACTER CLASSES By default, characters with values greater than 127 do not match any of the POSIX character classes, although this may be different for charac- - ters in the range 128-255 when locale-specific matching is happening. - However, if the PCRE2_UCP option is passed to pcre2_compile(), some of - the classes are changed so that Unicode character properties are used. + ters in the range 128-255 when locale-specific matching is happening. + However, if the PCRE2_UCP option is passed to pcre2_compile(), some of + the classes are changed so that Unicode character properties are used. This is achieved by replacing certain POSIX classes with other sequences, as follows: @@ -7360,10 +7384,10 @@ POSIX CHARACTER CLASSES [:upper:] becomes \p{Lu} [:word:] becomes \p{Xwd} - Negated versions, such as [:^alpha:] use \P instead of \p. Three other + Negated versions, such as [:^alpha:] use \P instead of \p. Three other POSIX classes are handled specially in UCP mode: - [:graph:] This matches characters that have glyphs that mark the page + [:graph:] This matches characters that have glyphs that mark the page when printed. In Unicode property terms, it matches all char- acters with the L, M, N, P, S, or Cf properties, except for: @@ -7372,60 +7396,60 @@ POSIX CHARACTER CLASSES U+2066 - U+2069 Various "isolate"s - [:print:] This matches the same characters as [:graph:] plus space - characters that are not controls, that is, characters with + [:print:] This matches the same characters as [:graph:] plus space + characters that are not controls, that is, characters with the Zs property. [:punct:] This matches all characters that have the Unicode P (punctua- - tion) property, plus those characters with code points less + tion) property, plus those characters with code points less than 256 that have the S (Symbol) property. - The other POSIX classes are unchanged, and match only characters with + The other POSIX classes are unchanged, and match only characters with code points less than 256. COMPATIBILITY FEATURE FOR WORD BOUNDARIES - In the POSIX.2 compliant library that was included in 4.4BSD Unix, the - ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word" + In the POSIX.2 compliant library that was included in 4.4BSD Unix, the + ugly syntax [[:<:]] and [[:>:]] is used for matching "start of word" and "end of word". PCRE2 treats these items as follows: [[:<:]] is converted to \b(?=\w) [[:>:]] is converted to \b(?<=\w) Only these exact character sequences are recognized. A sequence such as - [a[:<:]b] provokes error for an unrecognized POSIX class name. This - support is not compatible with Perl. It is provided to help migrations + [a[:<:]b] provokes error for an unrecognized POSIX class name. This + support is not compatible with Perl. It is provided to help migrations from other environments, and is best not used in any new patterns. Note - that \b matches at the start and the end of a word (see "Simple asser- - tions" above), and in a Perl-style pattern the preceding or following - character normally shows which is wanted, without the need for the - assertions that are used above in order to give exactly the POSIX be- + that \b matches at the start and the end of a word (see "Simple asser- + tions" above), and in a Perl-style pattern the preceding or following + character normally shows which is wanted, without the need for the + assertions that are used above in order to give exactly the POSIX be- haviour. VERTICAL BAR - Vertical bar characters are used to separate alternative patterns. For + Vertical bar characters are used to separate alternative patterns. For example, the pattern gilbert|sullivan - matches either "gilbert" or "sullivan". Any number of alternatives may - appear, and an empty alternative is permitted (matching the empty + matches either "gilbert" or "sullivan". Any number of alternatives may + appear, and an empty alternative is permitted (matching the empty string). The matching process tries each alternative in turn, from left - to right, and the first one that succeeds is used. If the alternatives - are within a group (defined below), "succeeds" means matching the rest + to right, and the first one that succeeds is used. If the alternatives + are within a group (defined below), "succeeds" means matching the rest of the main pattern as well as the alternative in the group. INTERNAL OPTION SETTING - The settings of the PCRE2_CASELESS, PCRE2_MULTILINE, PCRE2_DOTALL, - PCRE2_EXTENDED, PCRE2_EXTENDED_MORE, and PCRE2_NO_AUTO_CAPTURE options - can be changed from within the pattern by a sequence of letters - enclosed between "(?" and ")". These options are Perl-compatible, and - are described in detail in the pcre2api documentation. The option let- + The settings of the PCRE2_CASELESS, PCRE2_MULTILINE, PCRE2_DOTALL, + PCRE2_EXTENDED, PCRE2_EXTENDED_MORE, and PCRE2_NO_AUTO_CAPTURE options + can be changed from within the pattern by a sequence of letters + enclosed between "(?" and ")". These options are Perl-compatible, and + are described in detail in the pcre2api documentation. The option let- ters are: i for PCRE2_CASELESS @@ -7436,49 +7460,49 @@ INTERNAL OPTION SETTING xx for PCRE2_EXTENDED_MORE For example, (?im) sets caseless, multiline matching. It is also possi- - ble to unset these options by preceding the relevant letters with a + ble to unset these options by preceding the relevant letters with a hyphen, for example (?-im). The two "extended" options are not indepen- dent; unsetting either one cancels the effects of both of them. - A combined setting and unsetting such as (?im-sx), which sets - PCRE2_CASELESS and PCRE2_MULTILINE while unsetting PCRE2_DOTALL and - PCRE2_EXTENDED, is also permitted. Only one hyphen may appear in the - options string. If a letter appears both before and after the hyphen, - the option is unset. An empty options setting "(?)" is allowed. Need- + A combined setting and unsetting such as (?im-sx), which sets + PCRE2_CASELESS and PCRE2_MULTILINE while unsetting PCRE2_DOTALL and + PCRE2_EXTENDED, is also permitted. Only one hyphen may appear in the + options string. If a letter appears both before and after the hyphen, + the option is unset. An empty options setting "(?)" is allowed. Need- less to say, it has no effect. - If the first character following (? is a circumflex, it causes all of - the above options to be unset. Thus, (?^) is equivalent to (?-imnsx). - Letters may follow the circumflex to cause some options to be re- + If the first character following (? is a circumflex, it causes all of + the above options to be unset. Thus, (?^) is equivalent to (?-imnsx). + Letters may follow the circumflex to cause some options to be re- instated, but a hyphen may not appear. - The PCRE2-specific options PCRE2_DUPNAMES and PCRE2_UNGREEDY can be - changed in the same way as the Perl-compatible options by using the + The PCRE2-specific options PCRE2_DUPNAMES and PCRE2_UNGREEDY can be + changed in the same way as the Perl-compatible options by using the characters J and U respectively. However, these are not unset by (?^). - When one of these option changes occurs at top level (that is, not - inside group parentheses), the change applies to the remainder of the - pattern that follows. An option change within a group (see below for a + When one of these option changes occurs at top level (that is, not + inside group parentheses), the change applies to the remainder of the + pattern that follows. An option change within a group (see below for a description of groups) affects only that part of the group that follows it, so (a(?i)b)c - matches abc and aBc and no other strings (assuming PCRE2_CASELESS is - not used). By this means, options can be made to have different set- + matches abc and aBc and no other strings (assuming PCRE2_CASELESS is + not used). By this means, options can be made to have different set- tings in different parts of the pattern. Any changes made in one alter- - native do carry on into subsequent branches within the same group. For + native do carry on into subsequent branches within the same group. For example, (a(?i)b|c) - matches "ab", "aB", "c", and "C", even though when matching "C" the - first branch is abandoned before the option setting. This is because - the effects of option settings happen at compile time. There would be + matches "ab", "aB", "c", and "C", even though when matching "C" the + first branch is abandoned before the option setting. This is because + the effects of option settings happen at compile time. There would be some very weird behaviour otherwise. - As a convenient shorthand, if any option settings are required at the - start of a non-capturing group (see the next section), the option let- + As a convenient shorthand, if any option settings are required at the + start of a non-capturing group (see the next section), the option let- ters may appear between the "?" and the ":". Thus the two patterns (?i:saturday|sunday) @@ -7486,39 +7510,39 @@ INTERNAL OPTION SETTING match exactly the same set of strings. - Note: There are other PCRE2-specific options, applying to the whole - pattern, which can be set by the application when the compiling func- - tion is called. In addition, the pattern can contain special leading - sequences such as (*CRLF) to override what the application has set or - what has been defaulted. Details are given in the section entitled + Note: There are other PCRE2-specific options, applying to the whole + pattern, which can be set by the application when the compiling func- + tion is called. In addition, the pattern can contain special leading + sequences such as (*CRLF) to override what the application has set or + what has been defaulted. Details are given in the section entitled "Newline sequences" above. There are also the (*UTF) and (*UCP) leading - sequences that can be used to set UTF and Unicode property modes; they - are equivalent to setting the PCRE2_UTF and PCRE2_UCP options, respec- - tively. However, the application can set the PCRE2_NEVER_UTF and - PCRE2_NEVER_UCP options, which lock out the use of the (*UTF) and + sequences that can be used to set UTF and Unicode property modes; they + are equivalent to setting the PCRE2_UTF and PCRE2_UCP options, respec- + tively. However, the application can set the PCRE2_NEVER_UTF and + PCRE2_NEVER_UCP options, which lock out the use of the (*UTF) and (*UCP) sequences. GROUPS - Groups are delimited by parentheses (round brackets), which can be + Groups are delimited by parentheses (round brackets), which can be nested. Turning part of a pattern into a group does two things: 1. It localizes a set of alternatives. For example, the pattern cat(aract|erpillar|) - matches "cataract", "caterpillar", or "cat". Without the parentheses, + matches "cataract", "caterpillar", or "cat". Without the parentheses, it would match "cataract", "erpillar" or an empty string. - 2. It creates a "capture group". This means that, when the whole pat- - tern matches, the portion of the subject string that matched the group - is passed back to the caller, separately from the portion that matched - the whole pattern. (This applies only to the traditional matching + 2. It creates a "capture group". This means that, when the whole pat- + tern matches, the portion of the subject string that matched the group + is passed back to the caller, separately from the portion that matched + the whole pattern. (This applies only to the traditional matching function; the DFA matching function does not support capturing.) Opening parentheses are counted from left to right (starting from 1) to - obtain numbers for capture groups. For example, if the string "the red + obtain numbers for capture groups. For example, if the string "the red king" is matched against the pattern the ((red|white) (king|queen)) @@ -7526,11 +7550,11 @@ GROUPS the captured substrings are "red king", "red", and "king", and are num- bered 1, 2, and 3, respectively. - The fact that plain parentheses fulfil two functions is not always - helpful. There are often times when grouping is required without cap- - turing. If an opening parenthesis is followed by a question mark and a - colon, the group does not do any capturing, and is not counted when - computing the number of any subsequent capture groups. For example, if + The fact that plain parentheses fulfil two functions is not always + helpful. There are often times when grouping is required without cap- + turing. If an opening parenthesis is followed by a question mark and a + colon, the group does not do any capturing, and is not counted when + computing the number of any subsequent capture groups. For example, if the string "the white queen" is matched against the pattern the ((?:red|white) (king|queen)) @@ -7538,16 +7562,16 @@ GROUPS the captured substrings are "white queen" and "queen", and are numbered 1 and 2. The maximum number of capture groups is 65535. - As a convenient shorthand, if any option settings are required at the - start of a non-capturing group, the option letters may appear between + As a convenient shorthand, if any option settings are required at the + start of a non-capturing group, the option letters may appear between the "?" and the ":". Thus the two patterns (?i:saturday|sunday) (?:(?i)saturday|sunday) match exactly the same set of strings. Because alternative branches are - tried from left to right, and options are not reset until the end of - the group is reached, an option setting in one branch does affect sub- + tried from left to right, and options are not reset until the end of + the group is reached, an option setting in one branch does affect sub- sequent branches, so the above patterns match "SUNDAY" as well as "Sat- urday". @@ -7555,19 +7579,19 @@ GROUPS DUPLICATE GROUP NUMBERS Perl 5.10 introduced a feature whereby each alternative in a group uses - the same numbers for its capturing parentheses. Such a group starts - with (?| and is itself a non-capturing group. For example, consider + the same numbers for its capturing parentheses. Such a group starts + with (?| and is itself a non-capturing group. For example, consider this pattern: (?|(Sat)ur|(Sun))day - Because the two alternatives are inside a (?| group, both sets of cap- - turing parentheses are numbered one. Thus, when the pattern matches, - you can look at captured substring number one, whichever alternative - matched. This construct is useful when you want to capture part, but + Because the two alternatives are inside a (?| group, both sets of cap- + turing parentheses are numbered one. Thus, when the pattern matches, + you can look at captured substring number one, whichever alternative + matched. This construct is useful when you want to capture part, but not all, of one of a number of alternatives. Inside a (?| group, paren- - theses are numbered as usual, but the number is reset at the start of - each branch. The numbers of any capturing parentheses that follow the + theses are numbered as usual, but the number is reset at the start of + each branch. The numbers of any capturing parentheses that follow the whole group start after the highest number used in any branch. The fol- lowing example is taken from the Perl documentation. The numbers under- neath show in which buffer the captured content will be stored. @@ -7576,13 +7600,13 @@ DUPLICATE GROUP NUMBERS / ( a ) (?| x ( y ) z | (p (q) r) | (t) u (v) ) ( z ) /x # 1 2 2 3 2 3 4 - A backreference to a capture group uses the most recent value that is + A backreference to a capture group uses the most recent value that is set for the group. The following pattern matches "abcabc" or "defdef": /(?|(abc)|(def))\1/ - In contrast, a subroutine call to a capture group always refers to the - first one in the pattern with the given number. The following pattern + In contrast, a subroutine call to a capture group always refers to the + first one in the pattern with the given number. The following pattern matches "abcabc" or "defabc": /(?|(abc)|(def))(?1)/ @@ -7593,24 +7617,24 @@ DUPLICATE GROUP NUMBERS If a condition test for a group's having matched refers to a non-unique number, the test is true if any group with that number has matched. - An alternative approach to using this "branch reset" feature is to use + An alternative approach to using this "branch reset" feature is to use duplicate named groups, as described in the next section. NAMED CAPTURE GROUPS Identifying capture groups by number is simple, but it can be very hard - to keep track of the numbers in complicated patterns. Furthermore, if - an expression is modified, the numbers may change. To help with this - difficulty, PCRE2 supports the naming of capture groups. This feature - was not added to Perl until release 5.10. Python had the feature ear- - lier, and PCRE1 introduced it at release 4.0, using the Python syntax. + to keep track of the numbers in complicated patterns. Furthermore, if + an expression is modified, the numbers may change. To help with this + difficulty, PCRE2 supports the naming of capture groups. This feature + was not added to Perl until release 5.10. Python had the feature ear- + lier, and PCRE1 introduced it at release 4.0, using the Python syntax. PCRE2 supports both the Perl and the Python syntax. - In PCRE2, a capture group can be named in one of three ways: + In PCRE2, a capture group can be named in one of three ways: (?<name>...) or (?'name'...) as in Perl, or (?P<name>...) as in Python. - Names may be up to 32 code units long. When PCRE2_UTF is not set, they - may contain only ASCII alphanumeric characters and underscores, but + Names may be up to 32 code units long. When PCRE2_UTF is not set, they + may contain only ASCII alphanumeric characters and underscores, but must start with a non-digit. When PCRE2_UTF is set, the syntax of group names is extended to allow any Unicode letter or Unicode decimal digit. In other words, group names must match one of these patterns: @@ -7618,52 +7642,52 @@ NAMED CAPTURE GROUPS ^[_A-Za-z][_A-Za-z0-9]*\z when PCRE2_UTF is not set ^[_\p{L}][_\p{L}\p{Nd}]*\z when PCRE2_UTF is set - References to capture groups from other parts of the pattern, such as - backreferences, recursion, and conditions, can all be made by name as + References to capture groups from other parts of the pattern, such as + backreferences, recursion, and conditions, can all be made by name as well as by number. Named capture groups are allocated numbers as well as names, exactly as - if the names were not present. In both PCRE2 and Perl, capture groups - are primarily identified by numbers; any names are just aliases for + if the names were not present. In both PCRE2 and Perl, capture groups + are primarily identified by numbers; any names are just aliases for these numbers. The PCRE2 API provides function calls for extracting the - complete name-to-number translation table from a compiled pattern, as - well as convenience functions for extracting captured substrings by + complete name-to-number translation table from a compiled pattern, as + well as convenience functions for extracting captured substrings by name. - Warning: When more than one capture group has the same number, as - described in the previous section, a name given to one of them applies + Warning: When more than one capture group has the same number, as + described in the previous section, a name given to one of them applies to all of them. Perl allows identically numbered groups to have differ- - ent names. Consider this pattern, where there are two capture groups, + ent names. Consider this pattern, where there are two capture groups, both numbered 1: (?|(?<AA>aa)|(?<BB>bb)) - Perl allows this, with both names AA and BB as aliases of group 1. + Perl allows this, with both names AA and BB as aliases of group 1. Thus, after a successful match, both names yield the same value (either "aa" or "bb"). - In an attempt to reduce confusion, PCRE2 does not allow the same group + In an attempt to reduce confusion, PCRE2 does not allow the same group number to be associated with more than one name. The example above pro- - vokes a compile-time error. However, there is still scope for confu- + vokes a compile-time error. However, there is still scope for confu- sion. Consider this pattern: (?|(?<AA>aa)|(bb)) Although the second group number 1 is not explicitly named, the name AA - is still an alias for any group 1. Whether the pattern matches "aa" or + is still an alias for any group 1. Whether the pattern matches "aa" or "bb", a reference by name to group AA yields the matched string. - By default, a name must be unique within a pattern, except that dupli- + By default, a name must be unique within a pattern, except that dupli- cate names are permitted for groups with the same number, for example: (?|(?<AA>aa)|(?<AA>bb)) The duplicate name constraint can be disabled by setting the PCRE2_DUP- NAMES option at compile time, or by the use of (?J) within the pattern. - Duplicate names can be useful for patterns where only one instance of - the named capture group can match. Suppose you want to match the name - of a weekday, either as a 3-letter abbreviation or as the full name, - and in both cases you want to extract the abbreviation. This pattern + Duplicate names can be useful for patterns where only one instance of + the named capture group can match. Suppose you want to match the name + of a weekday, either as a 3-letter abbreviation or as the full name, + and in both cases you want to extract the abbreviation. This pattern (ignoring the line breaks) does the job: (?<DN>Mon|Fri|Sun)(?:day)?| @@ -7672,17 +7696,17 @@ NAMED CAPTURE GROUPS (?<DN>Thu)(?:rsday)?| (?<DN>Sat)(?:urday)? - There are five capture groups, but only one is ever set after a match. - The convenience functions for extracting the data by name returns the - substring for the first (and in this example, the only) group of that + There are five capture groups, but only one is ever set after a match. + The convenience functions for extracting the data by name returns the + substring for the first (and in this example, the only) group of that name that matched. This saves searching to find which numbered group it - was. (An alternative way of solving this problem is to use a "branch + was. (An alternative way of solving this problem is to use a "branch reset" group, as described in the previous section.) - If you make a backreference to a non-unique named group from elsewhere - in the pattern, the groups to which the name refers are checked in the - order in which they appear in the overall pattern. The first one that - is set is used for the reference. For example, this pattern matches + If you make a backreference to a non-unique named group from elsewhere + in the pattern, the groups to which the name refers are checked in the + order in which they appear in the overall pattern. The first one that + is set is used for the reference. For example, this pattern matches both "foofoo" and "barbar" but not "foobar" or "barfoo": (?:(?<n>foo)|(?<n>bar))\k<n> @@ -7695,15 +7719,15 @@ NAMED CAPTURE GROUPS If you use a named reference in a condition test (see the section about conditions below), either to check whether a capture group has matched, or to check for recursion, all groups with the same name are tested. If - the condition is true for any one of them, the overall condition is - true. This is the same behaviour as testing by number. For further - details of the interfaces for handling named capture groups, see the + the condition is true for any one of them, the overall condition is + true. This is the same behaviour as testing by number. For further + details of the interfaces for handling named capture groups, see the pcre2api documentation. REPETITION - Repetition is specified by quantifiers, which can follow any of the + Repetition is specified by quantifiers, which can follow any of the following items: a literal data character @@ -7717,17 +7741,17 @@ REPETITION a parenthesized group (including most assertions) a subroutine call (recursive or otherwise) - The general repetition quantifier specifies a minimum and maximum num- - ber of permitted matches, by giving the two numbers in curly brackets - (braces), separated by a comma. The numbers must be less than 65536, + The general repetition quantifier specifies a minimum and maximum num- + ber of permitted matches, by giving the two numbers in curly brackets + (braces), separated by a comma. The numbers must be less than 65536, and the first must be less than or equal to the second. For example, z{2,4} - matches "zz", "zzz", or "zzzz". A closing brace on its own is not a - special character. If the second number is omitted, but the comma is - present, there is no upper limit; if the second number and the comma - are both omitted, the quantifier specifies an exact number of required + matches "zz", "zzz", or "zzzz". A closing brace on its own is not a + special character. If the second number is omitted, but the comma is + present, there is no upper limit; if the second number and the comma + are both omitted, the quantifier specifies an exact number of required matches. Thus [aeiou]{3,} @@ -7736,50 +7760,50 @@ REPETITION \d{8} - matches exactly 8 digits. An opening curly bracket that appears in a - position where a quantifier is not allowed, or one that does not match - the syntax of a quantifier, is taken as a literal character. For exam- + matches exactly 8 digits. An opening curly bracket that appears in a + position where a quantifier is not allowed, or one that does not match + the syntax of a quantifier, is taken as a literal character. For exam- ple, {,6} is not a quantifier, but a literal string of four characters. In UTF modes, quantifiers apply to characters rather than to individual - code units. Thus, for example, \x{100}{2} matches two characters, each + code units. Thus, for example, \x{100}{2} matches two characters, each of which is represented by a two-byte sequence in a UTF-8 string. Simi- - larly, \X{3} matches three Unicode extended grapheme clusters, each of - which may be several code units long (and they may be of different + larly, \X{3} matches three Unicode extended grapheme clusters, each of + which may be several code units long (and they may be of different lengths). The quantifier {0} is permitted, causing the expression to behave as if the previous item and the quantifier were not present. This may be use- - ful for capture groups that are referenced as subroutines from else- - where in the pattern (but see also the section entitled "Defining cap- + ful for capture groups that are referenced as subroutines from else- + where in the pattern (but see also the section entitled "Defining cap- ture groups for use by reference only" below). Except for parenthesized - groups, items that have a {0} quantifier are omitted from the compiled + groups, items that have a {0} quantifier are omitted from the compiled pattern. - For convenience, the three most common quantifiers have single-charac- + For convenience, the three most common quantifiers have single-charac- ter abbreviations: * is equivalent to {0,} + is equivalent to {1,} ? is equivalent to {0,1} - It is possible to construct infinite loops by following a group that - can match no characters with a quantifier that has no upper limit, for + It is possible to construct infinite loops by following a group that + can match no characters with a quantifier that has no upper limit, for example: (a?)* - Earlier versions of Perl and PCRE1 used to give an error at compile + Earlier versions of Perl and PCRE1 used to give an error at compile time for such patterns. However, because there are cases where this can be useful, such patterns are now accepted, but if any repetition of the group does in fact match no characters, the loop is forcibly broken. - By default, quantifiers are "greedy", that is, they match as much as + By default, quantifiers are "greedy", that is, they match as much as possible (up to the maximum number of permitted times), without causing - the rest of the pattern to fail. The classic example of where this - gives problems is in trying to match comments in C programs. These - appear between /* and */ and within the comment, individual * and / - characters may appear. An attempt to match C comments by applying the + the rest of the pattern to fail. The classic example of where this + gives problems is in trying to match comments in C programs. These + appear between /* and */ and within the comment, individual * and / + characters may appear. An attempt to match C comments by applying the pattern /\*.*\*/ @@ -7788,17 +7812,17 @@ REPETITION /* first comment */ not comment /* second comment */ - fails, because it matches the entire string owing to the greediness of - the .* item. However, if a quantifier is followed by a question mark, + fails, because it matches the entire string owing to the greediness of + the .* item. However, if a quantifier is followed by a question mark, it ceases to be greedy, and instead matches the minimum number of times possible, so the pattern /\*.*?\*/ - does the right thing with the C comments. The meaning of the various - quantifiers is not otherwise changed, just the preferred number of - matches. Do not confuse this use of question mark with its use as a - quantifier in its own right. Because it has two uses, it can sometimes + does the right thing with the C comments. The meaning of the various + quantifiers is not otherwise changed, just the preferred number of + matches. Do not confuse this use of question mark with its use as a + quantifier in its own right. Because it has two uses, it can sometimes appear doubled, as in \d??\d @@ -7807,55 +7831,55 @@ REPETITION only way the rest of the pattern matches. If the PCRE2_UNGREEDY option is set (an option that is not available in - Perl), the quantifiers are not greedy by default, but individual ones - can be made greedy by following them with a question mark. In other + Perl), the quantifiers are not greedy by default, but individual ones + can be made greedy by following them with a question mark. In other words, it inverts the default behaviour. - When a parenthesized group is quantified with a minimum repeat count - that is greater than 1 or with a limited maximum, more memory is - required for the compiled pattern, in proportion to the size of the + When a parenthesized group is quantified with a minimum repeat count + that is greater than 1 or with a limited maximum, more memory is + required for the compiled pattern, in proportion to the size of the minimum or maximum. - If a pattern starts with .* or .{0,} and the PCRE2_DOTALL option - (equivalent to Perl's /s) is set, thus allowing the dot to match new- - lines, the pattern is implicitly anchored, because whatever follows - will be tried against every character position in the subject string, - so there is no point in retrying the overall match at any position + If a pattern starts with .* or .{0,} and the PCRE2_DOTALL option + (equivalent to Perl's /s) is set, thus allowing the dot to match new- + lines, the pattern is implicitly anchored, because whatever follows + will be tried against every character position in the subject string, + so there is no point in retrying the overall match at any position after the first. PCRE2 normally treats such a pattern as though it were preceded by \A. - In cases where it is known that the subject string contains no new- - lines, it is worth setting PCRE2_DOTALL in order to obtain this opti- + In cases where it is known that the subject string contains no new- + lines, it is worth setting PCRE2_DOTALL in order to obtain this opti- mization, or alternatively, using ^ to indicate anchoring explicitly. - However, there are some cases where the optimization cannot be used. - When .* is inside capturing parentheses that are the subject of a - backreference elsewhere in the pattern, a match at the start may fail + However, there are some cases where the optimization cannot be used. + When .* is inside capturing parentheses that are the subject of a + backreference elsewhere in the pattern, a match at the start may fail where a later one succeeds. Consider, for example: (.*)abc\1 - If the subject is "xyz123abc123" the match point is the fourth charac- + If the subject is "xyz123abc123" the match point is the fourth charac- ter. For this reason, such a pattern is not implicitly anchored. - Another case where implicit anchoring is not applied is when the lead- - ing .* is inside an atomic group. Once again, a match at the start may + Another case where implicit anchoring is not applied is when the lead- + ing .* is inside an atomic group. Once again, a match at the start may fail where a later one succeeds. Consider this pattern: (?>.*?a)b - It matches "ab" in the subject "aab". The use of the backtracking con- - trol verbs (*PRUNE) and (*SKIP) also disable this optimization, and + It matches "ab" in the subject "aab". The use of the backtracking con- + trol verbs (*PRUNE) and (*SKIP) also disable this optimization, and there is an option, PCRE2_NO_DOTSTAR_ANCHOR, to do so explicitly. - When a capture group is repeated, the value captured is the substring + When a capture group is repeated, the value captured is the substring that matched the final iteration. For example, after (tweedle[dume]{3}\s*)+ has matched "tweedledum tweedledee" the value of the captured substring - is "tweedledee". However, if there are nested capture groups, the cor- - responding captured values may have been set in previous iterations. + is "tweedledee". However, if there are nested capture groups, the cor- + responding captured values may have been set in previous iterations. For example, after (a|(b))+ @@ -7865,57 +7889,57 @@ REPETITION ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS - With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") - repetition, failure of what follows normally causes the repeated item - to be re-evaluated to see if a different number of repeats allows the - rest of the pattern to match. Sometimes it is useful to prevent this, - either to change the nature of the match, or to cause it fail earlier - than it otherwise might, when the author of the pattern knows there is + With both maximizing ("greedy") and minimizing ("ungreedy" or "lazy") + repetition, failure of what follows normally causes the repeated item + to be re-evaluated to see if a different number of repeats allows the + rest of the pattern to match. Sometimes it is useful to prevent this, + either to change the nature of the match, or to cause it fail earlier + than it otherwise might, when the author of the pattern knows there is no point in carrying on. - Consider, for example, the pattern \d+foo when applied to the subject + Consider, for example, the pattern \d+foo when applied to the subject line 123456bar After matching all 6 digits and then failing to match "foo", the normal - action of the matcher is to try again with only 5 digits matching the - \d+ item, and then with 4, and so on, before ultimately failing. - "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides + action of the matcher is to try again with only 5 digits matching the + \d+ item, and then with 4, and so on, before ultimately failing. + "Atomic grouping" (a term taken from Jeffrey Friedl's book) provides the means for specifying that once a group has matched, it is not to be re-evaluated in this way. - If we use atomic grouping for the previous example, the matcher gives - up immediately on failing to match "foo" the first time. The notation + If we use atomic grouping for the previous example, the matcher gives + up immediately on failing to match "foo" the first time. The notation is a kind of special parenthesis, starting with (?> as in this example: (?>\d+)foo - Perl 5.28 introduced an experimental alphabetic form starting with (* + Perl 5.28 introduced an experimental alphabetic form starting with (* which may be easier to remember: (*atomic:\d+)foo This kind of parenthesized group "locks up" the part of the pattern it contains once it has matched, and a failure further into the pattern is - prevented from backtracking into it. Backtracking past it to previous + prevented from backtracking into it. Backtracking past it to previous items, however, works as normal. An alternative description is that a group of this type matches exactly - the string of characters that an identical standalone pattern would + the string of characters that an identical standalone pattern would match, if anchored at the current point in the subject string. - Atomic groups are not capture groups. Simple cases such as the above - example can be thought of as a maximizing repeat that must swallow - everything it can. So, while both \d+ and \d+? are prepared to adjust - the number of digits they match in order to make the rest of the pat- + Atomic groups are not capture groups. Simple cases such as the above + example can be thought of as a maximizing repeat that must swallow + everything it can. So, while both \d+ and \d+? are prepared to adjust + the number of digits they match in order to make the rest of the pat- tern match, (?>\d+) can only match an entire sequence of digits. - Atomic groups in general can of course contain arbitrarily complicated + Atomic groups in general can of course contain arbitrarily complicated expressions, and can be nested. However, when the contents of an atomic - group is just a single repeated item, as in the example above, a sim- - pler notation, called a "possessive quantifier" can be used. This con- - sists of an additional + character following a quantifier. Using this + group is just a single repeated item, as in the example above, a sim- + pler notation, called a "possessive quantifier" can be used. This con- + sists of an additional + character following a quantifier. Using this notation, the previous example can be rewritten as \d++foo @@ -7925,46 +7949,46 @@ ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS (abc|xyz){2,3}+ - Possessive quantifiers are always greedy; the setting of the - PCRE2_UNGREEDY option is ignored. They are a convenient notation for - the simpler forms of atomic group. However, there is no difference in + Possessive quantifiers are always greedy; the setting of the + PCRE2_UNGREEDY option is ignored. They are a convenient notation for + the simpler forms of atomic group. However, there is no difference in the meaning of a possessive quantifier and the equivalent atomic group, - though there may be a performance difference; possessive quantifiers + though there may be a performance difference; possessive quantifiers should be slightly faster. - The possessive quantifier syntax is an extension to the Perl 5.8 syn- - tax. Jeffrey Friedl originated the idea (and the name) in the first + The possessive quantifier syntax is an extension to the Perl 5.8 syn- + tax. Jeffrey Friedl originated the idea (and the name) in the first edition of his book. Mike McCloskey liked it, so implemented it when he - built Sun's Java package, and PCRE1 copied it from there. It found its + built Sun's Java package, and PCRE1 copied it from there. It found its way into Perl at release 5.10. - PCRE2 has an optimization that automatically "possessifies" certain - simple pattern constructs. For example, the sequence A+B is treated as - A++B because there is no point in backtracking into a sequence of A's + PCRE2 has an optimization that automatically "possessifies" certain + simple pattern constructs. For example, the sequence A+B is treated as + A++B because there is no point in backtracking into a sequence of A's when B must follow. This feature can be disabled by the PCRE2_NO_AUTO- POSSESS option, or starting the pattern with (*NO_AUTO_POSSESS). - When a pattern contains an unlimited repeat inside a group that can - itself be repeated an unlimited number of times, the use of an atomic - group is the only way to avoid some failing matches taking a very long + When a pattern contains an unlimited repeat inside a group that can + itself be repeated an unlimited number of times, the use of an atomic + group is the only way to avoid some failing matches taking a very long time indeed. The pattern (\D+|<\d+>)*[!?] - matches an unlimited number of substrings that either consist of non- - digits, or digits enclosed in <>, followed by either ! or ?. When it + matches an unlimited number of substrings that either consist of non- + digits, or digits enclosed in <>, followed by either ! or ?. When it matches, it runs quickly. However, if it is applied to aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa - it takes a long time before reporting failure. This is because the - string can be divided between the internal \D+ repeat and the external - * repeat in a large number of ways, and all have to be tried. (The - example uses [!?] rather than a single character at the end, because - both PCRE2 and Perl have an optimization that allows for fast failure - when a single character is used. They remember the last single charac- - ter that is required for a match, and fail early if it is not present - in the string.) If the pattern is changed so that it uses an atomic + it takes a long time before reporting failure. This is because the + string can be divided between the internal \D+ repeat and the external + * repeat in a large number of ways, and all have to be tried. (The + example uses [!?] rather than a single character at the end, because + both PCRE2 and Perl have an optimization that allows for fast failure + when a single character is used. They remember the last single charac- + ter that is required for a match, and fail early if it is not present + in the string.) If the pattern is changed so that it uses an atomic group, like this: ((?>\D+)|<\d+>)*[!?] @@ -7975,28 +7999,28 @@ ATOMIC GROUPING AND POSSESSIVE QUANTIFIERS BACKREFERENCES Outside a character class, a backslash followed by a digit greater than - 0 (and possibly further digits) is a backreference to a capture group + 0 (and possibly further digits) is a backreference to a capture group earlier (that is, to its left) in the pattern, provided there have been that many previous capture groups. - However, if the decimal number following the backslash is less than 8, - it is always taken as a backreference, and causes an error only if - there are not that many capture groups in the entire pattern. In other + However, if the decimal number following the backslash is less than 8, + it is always taken as a backreference, and causes an error only if + there are not that many capture groups in the entire pattern. In other words, the group that is referenced need not be to the left of the ref- - erence for numbers less than 8. A "forward backreference" of this type + erence for numbers less than 8. A "forward backreference" of this type can make sense when a repetition is involved and the group to the right has participated in an earlier iteration. - It is not possible to have a numerical "forward backreference" to a - group whose number is 8 or more using this syntax because a sequence - such as \50 is interpreted as a character defined in octal. See the + It is not possible to have a numerical "forward backreference" to a + group whose number is 8 or more using this syntax because a sequence + such as \50 is interpreted as a character defined in octal. See the subsection entitled "Non-printing characters" above for further details - of the handling of digits following a backslash. Other forms of back- - referencing do not suffer from this restriction. In particular, there + of the handling of digits following a backslash. Other forms of back- + referencing do not suffer from this restriction. In particular, there is no problem when named capture groups are used (see below). - Another way of avoiding the ambiguity inherent in the use of digits - following a backslash is to use the \g escape sequence. This escape + Another way of avoiding the ambiguity inherent in the use of digits + following a backslash is to use the \g escape sequence. This escape must be followed by a signed or unsigned number, optionally enclosed in braces. These examples are all identical: @@ -8004,9 +8028,9 @@ BACKREFERENCES (ring), \g1 (ring), \g{1} - An unsigned number specifies an absolute reference without the ambigu- + An unsigned number specifies an absolute reference without the ambigu- ity that is present in the older syntax. It is also useful when literal - digits follow the reference. A signed number is a relative reference. + digits follow the reference. A signed number is a relative reference. Consider this example: (abc(def)ghi)\g{-1} @@ -8014,36 +8038,36 @@ BACKREFERENCES The sequence \g{-1} is a reference to the most recently started capture group before \g, that is, is it equivalent to \2 in this example. Simi- larly, \g{-2} would be equivalent to \1. The use of relative references - can be helpful in long patterns, and also in patterns that are created - by joining together fragments that contain references within them- + can be helpful in long patterns, and also in patterns that are created + by joining together fragments that contain references within them- selves. The sequence \g{+1} is a reference to the next capture group. This kind - of forward reference can be useful in patterns that repeat. Perl does + of forward reference can be useful in patterns that repeat. Perl does not support the use of + in this way. - A backreference matches whatever actually most recently matched the - capture group in the current subject string, rather than anything at + A backreference matches whatever actually most recently matched the + capture group in the current subject string, rather than anything at all that matches the group (see "Groups as subroutines" below for a way of doing that). So the pattern (sens|respons)e and \1ibility - matches "sense and sensibility" and "response and responsibility", but - not "sense and responsibility". If caseful matching is in force at the - time of the backreference, the case of letters is relevant. For exam- + matches "sense and sensibility" and "response and responsibility", but + not "sense and responsibility". If caseful matching is in force at the + time of the backreference, the case of letters is relevant. For exam- ple, ((?i)rah)\s+\1 - matches "rah rah" and "RAH RAH", but not "RAH rah", even though the + matches "rah rah" and "RAH RAH", but not "RAH rah", even though the original capture group is matched caselessly. - There are several different ways of writing backreferences to named - capture groups. The .NET syntax \k{name} and the Perl syntax \k<name> - or \k'name' are supported, as is the Python syntax (?P=name). Perl - 5.10's unified backreference syntax, in which \g can be used for both - numeric and named references, is also supported. We could rewrite the + There are several different ways of writing backreferences to named + capture groups. The .NET syntax \k{name} and the Perl syntax \k<name> + or \k'name' are supported, as is the Python syntax (?P=name). Perl + 5.10's unified backreference syntax, in which \g can be used for both + numeric and named references, is also supported. We could rewrite the above example in any of the following ways: (?<p1>(?i)rah)\s+\k<p1> @@ -8051,117 +8075,117 @@ BACKREFERENCES (?P<p1>(?i)rah)\s+(?P=p1) (?<p1>(?i)rah)\s+\g{p1} - A capture group that is referenced by name may appear in the pattern + A capture group that is referenced by name may appear in the pattern before or after the reference. - There may be more than one backreference to the same group. If a group - has not actually been used in a particular match, backreferences to it + There may be more than one backreference to the same group. If a group + has not actually been used in a particular match, backreferences to it always fail by default. For example, the pattern (a|(bc))\2 - always fails if it starts to match "a" rather than "bc". However, if + always fails if it starts to match "a" rather than "bc". However, if the PCRE2_MATCH_UNSET_BACKREF option is set at compile time, a backref- erence to an unset value matches an empty string. - Because there may be many capture groups in a pattern, all digits fol- - lowing a backslash are taken as part of a potential backreference num- - ber. If the pattern continues with a digit character, some delimiter - must be used to terminate the backreference. If the PCRE2_EXTENDED or - PCRE2_EXTENDED_MORE option is set, this can be white space. Otherwise, + Because there may be many capture groups in a pattern, all digits fol- + lowing a backslash are taken as part of a potential backreference num- + ber. If the pattern continues with a digit character, some delimiter + must be used to terminate the backreference. If the PCRE2_EXTENDED or + PCRE2_EXTENDED_MORE option is set, this can be white space. Otherwise, the \g{} syntax or an empty comment (see "Comments" below) can be used. Recursive backreferences - A backreference that occurs inside the group to which it refers fails - when the group is first used, so, for example, (a\1) never matches. - However, such references can be useful inside repeated groups. For + A backreference that occurs inside the group to which it refers fails + when the group is first used, so, for example, (a\1) never matches. + However, such references can be useful inside repeated groups. For example, the pattern (a|b\1)+ matches any number of "a"s and also "aba", "ababbaa" etc. At each iter- ation of the group, the backreference matches the character string cor- - responding to the previous iteration. In order for this to work, the - pattern must be such that the first iteration does not need to match - the backreference. This can be done using alternation, as in the exam- + responding to the previous iteration. In order for this to work, the + pattern must be such that the first iteration does not need to match + the backreference. This can be done using alternation, as in the exam- ple above, or by a quantifier with a minimum of zero. - Backreferences of this type cause the group that they reference to be - treated as an atomic group. Once the whole group has been matched, a - subsequent matching failure cannot cause backtracking into the middle + Backreferences of this type cause the group that they reference to be + treated as an atomic group. Once the whole group has been matched, a + subsequent matching failure cannot cause backtracking into the middle of the group. ASSERTIONS - An assertion is a test on the characters following or preceding the + An assertion is a test on the characters following or preceding the current matching point that does not consume any characters. The simple - assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described + assertions coded as \b, \B, \A, \G, \Z, \z, ^ and $ are described above. - More complicated assertions are coded as parenthesized groups. There - are two kinds: those that look ahead of the current position in the - subject string, and those that look behind it, and in each case an - assertion may be positive (must match for the assertion to be true) or - negative (must not match for the assertion to be true). An assertion + More complicated assertions are coded as parenthesized groups. There + are two kinds: those that look ahead of the current position in the + subject string, and those that look behind it, and in each case an + assertion may be positive (must match for the assertion to be true) or + negative (must not match for the assertion to be true). An assertion group is matched in the normal way, and if it is true, matching contin- - ues after it, but with the matching position in the subject string is + ues after it, but with the matching position in the subject string is was it was before the assertion was processed. - A lookaround assertion may also appear as the condition in a condi- - tional group (see below). In this case, the result of matching the + A lookaround assertion may also appear as the condition in a condi- + tional group (see below). In this case, the result of matching the assertion determines which branch of the condition is followed. - Assertion groups are not capture groups. If an assertion contains cap- - ture groups within it, these are counted for the purposes of numbering - the capture groups in the whole pattern. Within each branch of an - assertion, locally captured substrings may be referenced in the usual - way. For example, a sequence such as (.)\g{-1} can be used to check + Assertion groups are not capture groups. If an assertion contains cap- + ture groups within it, these are counted for the purposes of numbering + the capture groups in the whole pattern. Within each branch of an + assertion, locally captured substrings may be referenced in the usual + way. For example, a sequence such as (.)\g{-1} can be used to check that two adjacent characters are the same. - When a branch within an assertion fails to match, any substrings that - were captured are discarded (as happens with any pattern branch that - fails to match). A negative assertion is true only when all its + When a branch within an assertion fails to match, any substrings that + were captured are discarded (as happens with any pattern branch that + fails to match). A negative assertion is true only when all its branches fail to match; this means that no captured substrings are ever - retained after a successful negative assertion. When an assertion con- + retained after a successful negative assertion. When an assertion con- tains a matching branch, what happens depends on the type of assertion. - For a positive assertion, internally captured substrings in the suc- - cessful branch are retained, and matching continues with the next pat- - tern item after the assertion. For a negative assertion, a matching - branch means that the assertion is not true. If such an assertion is - being used as a condition in a conditional group (see below), captured - substrings are retained, because matching continues with the "no" + For a positive assertion, internally captured substrings in the suc- + cessful branch are retained, and matching continues with the next pat- + tern item after the assertion. For a negative assertion, a matching + branch means that the assertion is not true. If such an assertion is + being used as a condition in a conditional group (see below), captured + substrings are retained, because matching continues with the "no" branch of the condition. For other failing negative assertions, control passes to the previous backtracking point, thus discarding any captured strings within the assertion. - For compatibility with Perl, most assertion groups may be repeated; - though it makes no sense to assert the same thing several times, the + For compatibility with Perl, most assertion groups may be repeated; + though it makes no sense to assert the same thing several times, the side effect of capturing may occasionally be useful. However, an asser- - tion that forms the condition for a conditional group may not be quan- + tion that forms the condition for a conditional group may not be quan- tified. In practice, for other assertions, there only three cases: - (1) If the quantifier is {0}, the assertion is never obeyed during - matching. However, it may contain internal capture groups that are + (1) If the quantifier is {0}, the assertion is never obeyed during + matching. However, it may contain internal capture groups that are called from elsewhere via the subroutine mechanism. - (2) If quantifier is {0,n} where n is greater than zero, it is treated - as if it were {0,1}. At run time, the rest of the pattern match is + (2) If quantifier is {0,n} where n is greater than zero, it is treated + as if it were {0,1}. At run time, the rest of the pattern match is tried with and without the assertion, the order depending on the greed- iness of the quantifier. - (3) If the minimum repetition is greater than zero, the quantifier is - ignored. The assertion is obeyed just once when encountered during + (3) If the minimum repetition is greater than zero, the quantifier is + ignored. The assertion is obeyed just once when encountered during matching. Alphabetic assertion names - Traditionally, symbolic sequences such as (?= and (?<= have been used - to specify lookaround assertions. Perl 5.28 introduced some experimen- + Traditionally, symbolic sequences such as (?= and (?<= have been used + to specify lookaround assertions. Perl 5.28 introduced some experimen- tal alphabetic alternatives which might be easier to remember. They all - start with (* instead of (? and must be written using lower case let- + start with (* instead of (? and must be written using lower case let- ters. PCRE2 supports the following synonyms: (*positive_lookahead: or (*pla: is the same as (?= @@ -8169,8 +8193,8 @@ ASSERTIONS (*positive_lookbehind: or (*plb: is the same as (?<= (*negative_lookbehind: or (*nlb: is the same as (?<! - For example, (*pla:foo) is the same assertion as (?=foo). In the fol- - lowing sections, the various assertions are described using the origi- + For example, (*pla:foo) is the same assertion as (?=foo). In the fol- + lowing sections, the various assertions are described using the origi- nal symbolic forms. Lookahead assertions @@ -8180,38 +8204,38 @@ ASSERTIONS \w+(?=;) - matches a word followed by a semicolon, but does not include the semi- + matches a word followed by a semicolon, but does not include the semi- colon in the match, and foo(?!bar) - matches any occurrence of "foo" that is not followed by "bar". Note + matches any occurrence of "foo" that is not followed by "bar". Note that the apparently similar pattern (?!foo)bar - does not find an occurrence of "bar" that is preceded by something - other than "foo"; it finds any occurrence of "bar" whatsoever, because + does not find an occurrence of "bar" that is preceded by something + other than "foo"; it finds any occurrence of "bar" whatsoever, because the assertion (?!foo) is always true when the next three characters are "bar". A lookbehind assertion is needed to achieve the other effect. If you want to force a matching failure at some point in a pattern, the - most convenient way to do it is with (?!) because an empty string - always matches, so an assertion that requires there not to be an empty + most convenient way to do it is with (?!) because an empty string + always matches, so an assertion that requires there not to be an empty string must always fail. The backtracking control verb (*FAIL) or (*F) is a synonym for (?!). Lookbehind assertions - Lookbehind assertions start with (?<= for positive assertions and (?<! + Lookbehind assertions start with (?<= for positive assertions and (?<! for negative assertions. For example, (?<!foo)bar - does find an occurrence of "bar" that is not preceded by "foo". The - contents of a lookbehind assertion are restricted such that all the + does find an occurrence of "bar" that is not preceded by "foo". The + contents of a lookbehind assertion are restricted such that all the strings it matches must have a fixed length. However, if there are sev- - eral top-level alternatives, they do not all have to have the same + eral top-level alternatives, they do not all have to have the same fixed length. Thus (?<=bullock|donkey) @@ -8220,74 +8244,74 @@ ASSERTIONS (?<!dogs?|cats?) - causes an error at compile time. Branches that match different length - strings are permitted only at the top level of a lookbehind assertion. + causes an error at compile time. Branches that match different length + strings are permitted only at the top level of a lookbehind assertion. This is an extension compared with Perl, which requires all branches to match the same length of string. An assertion such as (?<=ab(c|de)) - is not permitted, because its single top-level branch can match two - different lengths, but it is acceptable to PCRE2 if rewritten to use + is not permitted, because its single top-level branch can match two + different lengths, but it is acceptable to PCRE2 if rewritten to use two top-level branches: (?<=abc|abde) - In some cases, the escape sequence \K (see above) can be used instead + In some cases, the escape sequence \K (see above) can be used instead of a lookbehind assertion to get round the fixed-length restriction. - The implementation of lookbehind assertions is, for each alternative, - to temporarily move the current position back by the fixed length and + The implementation of lookbehind assertions is, for each alternative, + to temporarily move the current position back by the fixed length and then try to match. If there are insufficient characters before the cur- rent position, the assertion fails. - In UTF-8 and UTF-16 modes, PCRE2 does not allow the \C escape (which - matches a single code unit even in a UTF mode) to appear in lookbehind - assertions, because it makes it impossible to calculate the length of - the lookbehind. The \X and \R escapes, which can match different num- + In UTF-8 and UTF-16 modes, PCRE2 does not allow the \C escape (which + matches a single code unit even in a UTF mode) to appear in lookbehind + assertions, because it makes it impossible to calculate the length of + the lookbehind. The \X and \R escapes, which can match different num- bers of code units, are never permitted in lookbehinds. - "Subroutine" calls (see below) such as (?2) or (?&X) are permitted in + "Subroutine" calls (see below) such as (?2) or (?&X) are permitted in lookbehinds, as long as the called capture group matches a fixed-length - string. However, recursion, that is, a "subroutine" call into a group + string. However, recursion, that is, a "subroutine" call into a group that is already active, is not supported. Perl does not support backreferences in lookbehinds. PCRE2 does support - them, but only if certain conditions are met. The - PCRE2_MATCH_UNSET_BACKREF option must not be set, there must be no use - of (?| in the pattern (it creates duplicate group numbers), and if the - backreference is by name, the name must be unique. Of course, the ref- + them, but only if certain conditions are met. The + PCRE2_MATCH_UNSET_BACKREF option must not be set, there must be no use + of (?| in the pattern (it creates duplicate group numbers), and if the + backreference is by name, the name must be unique. Of course, the ref- erenced group must itself match a fixed length substring. The following pattern matches words containing at least two characters that begin and end with the same character: \b(\w)\w++(?<=\1) - Possessive quantifiers can be used in conjunction with lookbehind + Possessive quantifiers can be used in conjunction with lookbehind assertions to specify efficient matching of fixed-length strings at the end of subject strings. Consider a simple pattern such as abcd$ - when applied to a long string that does not match. Because matching - proceeds from left to right, PCRE2 will look for each "a" in the sub- - ject and then see if what follows matches the rest of the pattern. If + when applied to a long string that does not match. Because matching + proceeds from left to right, PCRE2 will look for each "a" in the sub- + ject and then see if what follows matches the rest of the pattern. If the pattern is specified as ^.*abcd$ - the initial .* matches the entire string at first, but when this fails + the initial .* matches the entire string at first, but when this fails (because there is no following "a"), it backtracks to match all but the - last character, then all but the last two characters, and so on. Once - again the search for "a" covers the entire string, from right to left, + last character, then all but the last two characters, and so on. Once + again the search for "a" covers the entire string, from right to left, so we are no better off. However, if the pattern is written as ^.*+(?<=abcd) there can be no backtracking for the .*+ item because of the possessive quantifier; it can match only the entire string. The subsequent lookbe- - hind assertion does a single test on the last four characters. If it - fails, the match fails immediately. For long strings, this approach + hind assertion does a single test on the last four characters. If it + fails, the match fails immediately. For long strings, this approach makes a significant difference to the processing time. Using multiple assertions @@ -8296,18 +8320,18 @@ ASSERTIONS (?<=\d{3})(?<!999)foo - matches "foo" preceded by three digits that are not "999". Notice that - each of the assertions is applied independently at the same point in - the subject string. First there is a check that the previous three - characters are all digits, and then there is a check that the same + matches "foo" preceded by three digits that are not "999". Notice that + each of the assertions is applied independently at the same point in + the subject string. First there is a check that the previous three + characters are all digits, and then there is a check that the same three characters are not "999". This pattern does not match "foo" pre- - ceded by six characters, the first of which are digits and the last - three of which are not "999". For example, it doesn't match "123abc- + ceded by six characters, the first of which are digits and the last + three of which are not "999". For example, it doesn't match "123abc- foo". A pattern to do that is (?<=\d{3}...)(?<!999)foo - This time the first assertion looks at the preceding six characters, + This time the first assertion looks at the preceding six characters, checking that the first three are digits, and then the second assertion checks that the preceding three characters are not "999". @@ -8315,53 +8339,53 @@ ASSERTIONS (?<=(?<!foo)bar)baz - matches an occurrence of "baz" that is preceded by "bar" which in turn + matches an occurrence of "baz" that is preceded by "bar" which in turn is not preceded by "foo", while (?<=\d{3}(?!999)...)foo - is another pattern that matches "foo" preceded by three digits and any + is another pattern that matches "foo" preceded by three digits and any three characters that are not "999". SCRIPT RUNS - In concept, a script run is a sequence of characters that are all from - the same Unicode script such as Latin or Greek. However, because some - scripts are commonly used together, and because some diacritical and - other marks are used with multiple scripts, it is not that simple. + In concept, a script run is a sequence of characters that are all from + the same Unicode script such as Latin or Greek. However, because some + scripts are commonly used together, and because some diacritical and + other marks are used with multiple scripts, it is not that simple. There is a full description of the rules that PCRE2 uses in the section entitled "Script Runs" in the pcre2unicode documentation. - If part of a pattern is enclosed between (*script_run: or (*sr: and a - closing parenthesis, it fails if the sequence of characters that it - matches are not a script run. After a failure, normal backtracking - occurs. Script runs can be used to detect spoofing attacks using char- - acters that look the same, but are from different scripts. The string - "paypal.com" is an infamous example, where the letters could be a mix- + If part of a pattern is enclosed between (*script_run: or (*sr: and a + closing parenthesis, it fails if the sequence of characters that it + matches are not a script run. After a failure, normal backtracking + occurs. Script runs can be used to detect spoofing attacks using char- + acters that look the same, but are from different scripts. The string + "paypal.com" is an infamous example, where the letters could be a mix- ture of Latin and Cyrillic. This pattern ensures that the matched char- acters in a sequence of non-spaces that follow white space are a script run: \s+(*sr:\S+) - To be sure that they are all from the Latin script (for example), a + To be sure that they are all from the Latin script (for example), a lookahead can be used: \s+(?=\p{Latin})(*sr:\S+) This works as long as the first character is expected to be a character - in that script, and not (for example) punctuation, which is allowed - with any script. If this is not the case, a more creative lookahead is - needed. For example, if digits, underscore, and dots are permitted at + in that script, and not (for example) punctuation, which is allowed + with any script. If this is not the case, a more creative lookahead is + needed. For example, if digits, underscore, and dots are permitted at the start: \s+(?=[0-9_.]*\p{Latin})(*sr:\S+) - In many cases, backtracking into a script run pattern fragment is not - desirable. The script run can employ an atomic group to prevent this. - Because this is a common requirement, a shorthand notation is provided + In many cases, backtracking into a script run pattern fragment is not + desirable. The script run can employ an atomic group to prevent this. + Because this is a common requirement, a shorthand notation is provided by (*atomic_script_run: or (*asr: (*asr:...) is the same as (*sr:(?>...)) @@ -8369,13 +8393,13 @@ SCRIPT RUNS Note that the atomic group is inside the script run. Putting it outside would not prevent backtracking into the script run pattern. - Support for script runs is not available if PCRE2 is compiled without + Support for script runs is not available if PCRE2 is compiled without Unicode support. A compile-time error is given if any of the above con- - structs is encountered. Script runs are not supported by the alternate - matching function, pcre2_dfa_match() because they use the same mecha- + structs is encountered. Script runs are not supported by the alternate + matching function, pcre2_dfa_match() because they use the same mecha- nism as capturing parentheses. - Warning: The (*ACCEPT) control verb (see below) should not be used + Warning: The (*ACCEPT) control verb (see below) should not be used within a script run group, because it causes an immediate exit from the group, bypassing the script run checking. @@ -8384,116 +8408,116 @@ CONDITIONAL GROUPS It is possible to cause the matching process to obey a pattern fragment conditionally or to choose between two alternative fragments, depending - on the result of an assertion, or whether a specific capture group has + on the result of an assertion, or whether a specific capture group has already been matched. The two possible forms of conditional group are: (?(condition)yes-pattern) (?(condition)yes-pattern|no-pattern) - If the condition is satisfied, the yes-pattern is used; otherwise the - no-pattern (if present) is used. An absent no-pattern is equivalent to - an empty string (it always matches). If there are more than two alter- - natives in the group, a compile-time error occurs. Each of the two - alternatives may itself contain nested groups of any form, including + If the condition is satisfied, the yes-pattern is used; otherwise the + no-pattern (if present) is used. An absent no-pattern is equivalent to + an empty string (it always matches). If there are more than two alter- + natives in the group, a compile-time error occurs. Each of the two + alternatives may itself contain nested groups of any form, including conditional groups; the restriction to two alternatives applies only at - the level of the condition itself. This pattern fragment is an example + the level of the condition itself. This pattern fragment is an example where the alternatives are complex: (?(1) (A|B|C) | (D | (?(2)E|F) | E) ) There are five kinds of condition: references to capture groups, refer- - ences to recursion, two pseudo-conditions called DEFINE and VERSION, + ences to recursion, two pseudo-conditions called DEFINE and VERSION, and assertions. Checking for a used capture group by number - If the text between the parentheses consists of a sequence of digits, - the condition is true if a capture group of that number has previously - matched. If there is more than one capture group with the same number - (see the earlier section about duplicate group numbers), the condition + If the text between the parentheses consists of a sequence of digits, + the condition is true if a capture group of that number has previously + matched. If there is more than one capture group with the same number + (see the earlier section about duplicate group numbers), the condition is true if any of them have matched. An alternative notation is to pre- cede the digits with a plus or minus sign. In this case, the group num- - ber is relative rather than absolute. The most recently opened capture - group can be referenced by (?(-1), the next most recent by (?(-2), and - so on. Inside loops it can also make sense to refer to subsequent - groups. The next capture group can be referenced as (?(+1), and so on. - (The value zero in any of these forms is not used; it provokes a com- + ber is relative rather than absolute. The most recently opened capture + group can be referenced by (?(-1), the next most recent by (?(-2), and + so on. Inside loops it can also make sense to refer to subsequent + groups. The next capture group can be referenced as (?(+1), and so on. + (The value zero in any of these forms is not used; it provokes a com- pile-time error.) - Consider the following pattern, which contains non-significant white - space to make it more readable (assume the PCRE2_EXTENDED option) and + Consider the following pattern, which contains non-significant white + space to make it more readable (assume the PCRE2_EXTENDED option) and to divide it into three parts for ease of discussion: ( \( )? [^()]+ (?(1) \) ) - The first part matches an optional opening parenthesis, and if that + The first part matches an optional opening parenthesis, and if that character is present, sets it as the first captured substring. The sec- - ond part matches one or more characters that are not parentheses. The - third part is a conditional group that tests whether or not the first - capture group matched. If it did, that is, if subject started with an - opening parenthesis, the condition is true, and so the yes-pattern is - executed and a closing parenthesis is required. Otherwise, since no- + ond part matches one or more characters that are not parentheses. The + third part is a conditional group that tests whether or not the first + capture group matched. If it did, that is, if subject started with an + opening parenthesis, the condition is true, and so the yes-pattern is + executed and a closing parenthesis is required. Otherwise, since no- pattern is not present, the conditional group matches nothing. In other - words, this pattern matches a sequence of non-parentheses, optionally + words, this pattern matches a sequence of non-parentheses, optionally enclosed in parentheses. - If you were embedding this pattern in a larger one, you could use a + If you were embedding this pattern in a larger one, you could use a relative reference: ...other stuff... ( \( )? [^()]+ (?(-1) \) ) ... - This makes the fragment independent of the parentheses in the larger + This makes the fragment independent of the parentheses in the larger pattern. Checking for a used capture group by name - Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a - used capture group by name. For compatibility with earlier versions of - PCRE1, which had this facility before Perl, the syntax (?(name)...) is - also recognized. Note, however, that undelimited names consisting of - the letter R followed by digits are ambiguous (see the following sec- + Perl uses the syntax (?(<name>)...) or (?('name')...) to test for a + used capture group by name. For compatibility with earlier versions of + PCRE1, which had this facility before Perl, the syntax (?(name)...) is + also recognized. Note, however, that undelimited names consisting of + the letter R followed by digits are ambiguous (see the following sec- tion). Rewriting the above example to use a named group gives this: (?<OPEN> \( )? [^()]+ (?(<OPEN>) \) ) - If the name used in a condition of this kind is a duplicate, the test - is applied to all groups of the same name, and is true if any one of + If the name used in a condition of this kind is a duplicate, the test + is applied to all groups of the same name, and is true if any one of them has matched. Checking for pattern recursion - "Recursion" in this sense refers to any subroutine-like call from one - part of the pattern to another, whether or not it is actually recur- - sive. See the sections entitled "Recursive patterns" and "Groups as + "Recursion" in this sense refers to any subroutine-like call from one + part of the pattern to another, whether or not it is actually recur- + sive. See the sections entitled "Recursive patterns" and "Groups as subroutines" below for details of recursion and subroutine calls. - If a condition is the string (R), and there is no capture group with - the name R, the condition is true if matching is currently in a recur- - sion or subroutine call to the whole pattern or any capture group. If - digits follow the letter R, and there is no group with that name, the - condition is true if the most recent call is into a group with the - given number, which must exist somewhere in the overall pattern. This + If a condition is the string (R), and there is no capture group with + the name R, the condition is true if matching is currently in a recur- + sion or subroutine call to the whole pattern or any capture group. If + digits follow the letter R, and there is no group with that name, the + condition is true if the most recent call is into a group with the + given number, which must exist somewhere in the overall pattern. This is a contrived example that is equivalent to a+b: ((?(R1)a+|(?1)b)) - However, in both cases, if there is a capture group with a matching - name, the condition tests for its being set, as described in the sec- - tion above, instead of testing for recursion. For example, creating a - group with the name R1 by adding (?<R1>) to the above pattern com- + However, in both cases, if there is a capture group with a matching + name, the condition tests for its being set, as described in the sec- + tion above, instead of testing for recursion. For example, creating a + group with the name R1 by adding (?<R1>) to the above pattern com- pletely changes its meaning. If a name preceded by ampersand follows the letter R, for example: (?(R&name)...) - the condition is true if the most recent recursion is into a group of + the condition is true if the most recent recursion is into a group of that name (which must exist within the pattern). This condition does not check the entire recursion stack. It tests only - the current level. If the name used in a condition of this kind is a - duplicate, the test is applied to all groups of the same name, and is + the current level. If the name used in a condition of this kind is a + duplicate, the test is applied to all groups of the same name, and is true if any one of them is the most recent recursion. At "top level", all these recursion test conditions are false. @@ -8501,110 +8525,110 @@ CONDITIONAL GROUPS Defining capture groups for use by reference only If the condition is the string (DEFINE), the condition is always false, - even if there is a group with the name DEFINE. In this case, there may - be only one alternative in the rest of the conditional group. It is - always skipped if control reaches this point in the pattern; the idea + even if there is a group with the name DEFINE. In this case, there may + be only one alternative in the rest of the conditional group. It is + always skipped if control reaches this point in the pattern; the idea of DEFINE is that it can be used to define subroutines that can be ref- - erenced from elsewhere. (The use of subroutines is described below.) - For example, a pattern to match an IPv4 address such as - "192.168.23.245" could be written like this (ignore white space and + erenced from elsewhere. (The use of subroutines is described below.) + For example, a pattern to match an IPv4 address such as + "192.168.23.245" could be written like this (ignore white space and line breaks): (?(DEFINE) (?<byte> 2[0-4]\d | 25[0-5] | 1\d\d | [1-9]?\d) ) \b (?&byte) (\.(?&byte)){3} \b - The first part of the pattern is a DEFINE group inside which a another - group named "byte" is defined. This matches an individual component of - an IPv4 address (a number less than 256). When matching takes place, - this part of the pattern is skipped because DEFINE acts like a false - condition. The rest of the pattern uses references to the named group - to match the four dot-separated components of an IPv4 address, insist- + The first part of the pattern is a DEFINE group inside which a another + group named "byte" is defined. This matches an individual component of + an IPv4 address (a number less than 256). When matching takes place, + this part of the pattern is skipped because DEFINE acts like a false + condition. The rest of the pattern uses references to the named group + to match the four dot-separated components of an IPv4 address, insist- ing on a word boundary at each end. Checking the PCRE2 version - Programs that link with a PCRE2 library can check the version by call- - ing pcre2_config() with appropriate arguments. Users of applications - that do not have access to the underlying code cannot do this. A spe- - cial "condition" called VERSION exists to allow such users to discover + Programs that link with a PCRE2 library can check the version by call- + ing pcre2_config() with appropriate arguments. Users of applications + that do not have access to the underlying code cannot do this. A spe- + cial "condition" called VERSION exists to allow such users to discover which version of PCRE2 they are dealing with by using this condition to - match a string such as "yesno". VERSION must be followed either by "=" + match a string such as "yesno". VERSION must be followed either by "=" or ">=" and a version number. For example: (?(VERSION>=10.4)yes|no) - This pattern matches "yes" if the PCRE2 version is greater or equal to - 10.4, or "no" otherwise. The fractional part of the version number may + This pattern matches "yes" if the PCRE2 version is greater or equal to + 10.4, or "no" otherwise. The fractional part of the version number may not contain more than two digits. Assertion conditions - If the condition is not in any of the above formats, it must be a - parenthesized assertion. This may be a positive or negative lookahead - or lookbehind assertion. Consider this pattern, again containing non- - significant white space, and with the two alternatives on the second + If the condition is not in any of the above formats, it must be a + parenthesized assertion. This may be a positive or negative lookahead + or lookbehind assertion. Consider this pattern, again containing non- + significant white space, and with the two alternatives on the second line: (?(?=[^a-z]*[a-z]) \d{2}-[a-z]{3}-\d{2} | \d{2}-\d{2}-\d{2} ) - The condition is a positive lookahead assertion that matches an - optional sequence of non-letters followed by a letter. In other words, - it tests for the presence of at least one letter in the subject. If a - letter is found, the subject is matched against the first alternative; - otherwise it is matched against the second. This pattern matches - strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are + The condition is a positive lookahead assertion that matches an + optional sequence of non-letters followed by a letter. In other words, + it tests for the presence of at least one letter in the subject. If a + letter is found, the subject is matched against the first alternative; + otherwise it is matched against the second. This pattern matches + strings in one of the two forms dd-aaa-dd or dd-dd-dd, where aaa are letters and dd are digits. When an assertion that is a condition contains capture groups, any cap- - turing that occurs in a matching branch is retained afterwards, for - both positive and negative assertions, because matching always contin- - ues after the assertion, whether it succeeds or fails. (Compare non- - conditional assertions, for which captures are retained only for posi- + turing that occurs in a matching branch is retained afterwards, for + both positive and negative assertions, because matching always contin- + ues after the assertion, whether it succeeds or fails. (Compare non- + conditional assertions, for which captures are retained only for posi- tive assertions that succeed.) COMMENTS There are two ways of including comments in patterns that are processed - by PCRE2. In both cases, the start of the comment must not be in a - character class, nor in the middle of any other sequence of related - characters such as (?: or a group name or number. The characters that + by PCRE2. In both cases, the start of the comment must not be in a + character class, nor in the middle of any other sequence of related + characters such as (?: or a group name or number. The characters that make up a comment play no part in the pattern matching. - The sequence (?# marks the start of a comment that continues up to the - next closing parenthesis. Nested parentheses are not permitted. If the - PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, an unescaped # - character also introduces a comment, which in this case continues to - immediately after the next newline character or character sequence in + The sequence (?# marks the start of a comment that continues up to the + next closing parenthesis. Nested parentheses are not permitted. If the + PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is set, an unescaped # + character also introduces a comment, which in this case continues to + immediately after the next newline character or character sequence in the pattern. Which characters are interpreted as newlines is controlled - by an option passed to the compiling function or by a special sequence + by an option passed to the compiling function or by a special sequence at the start of the pattern, as described in the section entitled "New- line conventions" above. Note that the end of this type of comment is a - literal newline sequence in the pattern; escape sequences that happen + literal newline sequence in the pattern; escape sequences that happen to represent a newline do not count. For example, consider this pattern - when PCRE2_EXTENDED is set, and the default newline convention (a sin- + when PCRE2_EXTENDED is set, and the default newline convention (a sin- gle linefeed character) is in force: abc #comment \n still comment - On encountering the # character, pcre2_compile() skips along, looking - for a newline in the pattern. The sequence \n is still literal at this - stage, so it does not terminate the comment. Only an actual character + On encountering the # character, pcre2_compile() skips along, looking + for a newline in the pattern. The sequence \n is still literal at this + stage, so it does not terminate the comment. Only an actual character with the code value 0x0a (the default newline) does so. RECURSIVE PATTERNS - Consider the problem of matching a string in parentheses, allowing for - unlimited nested parentheses. Without the use of recursion, the best - that can be done is to use a pattern that matches up to some fixed - depth of nesting. It is not possible to handle an arbitrary nesting + Consider the problem of matching a string in parentheses, allowing for + unlimited nested parentheses. Without the use of recursion, the best + that can be done is to use a pattern that matches up to some fixed + depth of nesting. It is not possible to handle an arbitrary nesting depth. For some time, Perl has provided a facility that allows regular expres- - sions to recurse (amongst other things). It does this by interpolating - Perl code in the expression at run time, and the code can refer to the + sions to recurse (amongst other things). It does this by interpolating + Perl code in the expression at run time, and the code can refer to the expression itself. A Perl pattern using code interpolation to solve the parentheses problem can be created like this: @@ -8614,66 +8638,66 @@ RECURSIVE PATTERNS refers recursively to the pattern in which it appears. Obviously, PCRE2 cannot support the interpolation of Perl code. - Instead, it supports special syntax for recursion of the entire pat- + Instead, it supports special syntax for recursion of the entire pat- tern, and also for individual capture group recursion. After its intro- - duction in PCRE1 and Python, this kind of recursion was subsequently + duction in PCRE1 and Python, this kind of recursion was subsequently introduced into Perl at release 5.10. - A special item that consists of (? followed by a number greater than - zero and a closing parenthesis is a recursive subroutine call of the - capture group of the given number, provided that it occurs inside that - group. (If not, it is a non-recursive subroutine call, which is - described in the next section.) The special item (?R) or (?0) is a + A special item that consists of (? followed by a number greater than + zero and a closing parenthesis is a recursive subroutine call of the + capture group of the given number, provided that it occurs inside that + group. (If not, it is a non-recursive subroutine call, which is + described in the next section.) The special item (?R) or (?0) is a recursive call of the entire regular expression. - This PCRE2 pattern solves the nested parentheses problem (assume the + This PCRE2 pattern solves the nested parentheses problem (assume the PCRE2_EXTENDED option is set so that white space is ignored): \( ( [^()]++ | (?R) )* \) - First it matches an opening parenthesis. Then it matches any number of - substrings which can either be a sequence of non-parentheses, or a - recursive match of the pattern itself (that is, a correctly parenthe- + First it matches an opening parenthesis. Then it matches any number of + substrings which can either be a sequence of non-parentheses, or a + recursive match of the pattern itself (that is, a correctly parenthe- sized substring). Finally there is a closing parenthesis. Note the use of a possessive quantifier to avoid backtracking into sequences of non- parentheses. - If this were part of a larger pattern, you would not want to recurse + If this were part of a larger pattern, you would not want to recurse the entire pattern, so instead you could use this: ( \( ( [^()]++ | (?1) )* \) ) - We have put the pattern into parentheses, and caused the recursion to + We have put the pattern into parentheses, and caused the recursion to refer to them instead of the whole pattern. - In a larger pattern, keeping track of parenthesis numbers can be - tricky. This is made easier by the use of relative references. Instead + In a larger pattern, keeping track of parenthesis numbers can be + tricky. This is made easier by the use of relative references. Instead of (?1) in the pattern above you can write (?-2) to refer to the second - most recently opened parentheses preceding the recursion. In other - words, a negative number counts capturing parentheses leftwards from + most recently opened parentheses preceding the recursion. In other + words, a negative number counts capturing parentheses leftwards from the point at which it is encountered. - Be aware however, that if duplicate capture group numbers are in use, - relative references refer to the earliest group with the appropriate + Be aware however, that if duplicate capture group numbers are in use, + relative references refer to the earliest group with the appropriate number. Consider, for example: (?|(a)|(b)) (c) (?-2) The first two capture groups (a) and (b) are both numbered 1, and group - (c) is number 2. When the reference (?-2) is encountered, the second - most recently opened parentheses has the number 1, but it is the first + (c) is number 2. When the reference (?-2) is encountered, the second + most recently opened parentheses has the number 1, but it is the first such group (the (a) group) to which the recursion refers. This would be - the same if an absolute reference (?1) was used. In other words, rela- + the same if an absolute reference (?1) was used. In other words, rela- tive references are just a shorthand for computing a group number. - It is also possible to refer to subsequent capture groups, by writing - references such as (?+2). However, these cannot be recursive because - the reference is not inside the parentheses that are referenced. They - are always non-recursive subroutine calls, as described in the next + It is also possible to refer to subsequent capture groups, by writing + references such as (?+2). However, these cannot be recursive because + the reference is not inside the parentheses that are referenced. They + are always non-recursive subroutine calls, as described in the next section. - An alternative approach is to use named parentheses. The Perl syntax - for this is (?&name); PCRE1's earlier syntax (?P>name) is also sup- + An alternative approach is to use named parentheses. The Perl syntax + for this is (?&name); PCRE1's earlier syntax (?P>name) is also sup- ported. We could rewrite the above example as follows: (?<pn> \( ( [^()]++ | (?&pn) )* \) ) @@ -8682,106 +8706,106 @@ RECURSIVE PATTERNS used. The example pattern that we have been looking at contains nested unlim- - ited repeats, and so the use of a possessive quantifier for matching - strings of non-parentheses is important when applying the pattern to + ited repeats, and so the use of a possessive quantifier for matching + strings of non-parentheses is important when applying the pattern to strings that do not match. For example, when this pattern is applied to (aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa() - it yields "no match" quickly. However, if a possessive quantifier is - not used, the match runs for a very long time indeed because there are - so many different ways the + and * repeats can carve up the subject, + it yields "no match" quickly. However, if a possessive quantifier is + not used, the match runs for a very long time indeed because there are + so many different ways the + and * repeats can carve up the subject, and all have to be tested before failure can be reported. - At the end of a match, the values of capturing parentheses are those - from the outermost level. If you want to obtain intermediate values, a + At the end of a match, the values of capturing parentheses are those + from the outermost level. If you want to obtain intermediate values, a callout function can be used (see below and the pcre2callout documenta- tion). If the pattern above is matched against (ab(cd)ef) - the value for the inner capturing parentheses (numbered 2) is "ef", - which is the last value taken on at the top level. If a capture group - is not matched at the top level, its final captured value is unset, - even if it was (temporarily) set at a deeper level during the matching + the value for the inner capturing parentheses (numbered 2) is "ef", + which is the last value taken on at the top level. If a capture group + is not matched at the top level, its final captured value is unset, + even if it was (temporarily) set at a deeper level during the matching process. - Do not confuse the (?R) item with the condition (R), which tests for - recursion. Consider this pattern, which matches text in angle brack- - ets, allowing for arbitrary nesting. Only digits are allowed in nested - brackets (that is, when recursing), whereas any characters are permit- + Do not confuse the (?R) item with the condition (R), which tests for + recursion. Consider this pattern, which matches text in angle brack- + ets, allowing for arbitrary nesting. Only digits are allowed in nested + brackets (that is, when recursing), whereas any characters are permit- ted at the outer level. < (?: (?(R) \d++ | [^<>]*+) | (?R)) * > - In this pattern, (?(R) is the start of a conditional group, with two - different alternatives for the recursive and non-recursive cases. The + In this pattern, (?(R) is the start of a conditional group, with two + different alternatives for the recursive and non-recursive cases. The (?R) item is the actual recursive call. Differences in recursion processing between PCRE2 and Perl Some former differences between PCRE2 and Perl no longer exist. - Before release 10.30, recursion processing in PCRE2 differed from Perl - in that a recursive subroutine call was always treated as an atomic - group. That is, once it had matched some of the subject string, it was - never re-entered, even if it contained untried alternatives and there - was a subsequent matching failure. (Historical note: PCRE implemented + Before release 10.30, recursion processing in PCRE2 differed from Perl + in that a recursive subroutine call was always treated as an atomic + group. That is, once it had matched some of the subject string, it was + never re-entered, even if it contained untried alternatives and there + was a subsequent matching failure. (Historical note: PCRE implemented recursion before Perl did.) - Starting with release 10.30, recursive subroutine calls are no longer + Starting with release 10.30, recursive subroutine calls are no longer treated as atomic. That is, they can be re-entered to try unused alter- - natives if there is a matching failure later in the pattern. This is - now compatible with the way Perl works. If you want a subroutine call + natives if there is a matching failure later in the pattern. This is + now compatible with the way Perl works. If you want a subroutine call to be atomic, you must explicitly enclose it in an atomic group. - Supporting backtracking into recursions simplifies certain types of + Supporting backtracking into recursions simplifies certain types of recursive pattern. For example, this pattern matches palindromic strings: ^((.)(?1)\2|.?)$ - The second branch in the group matches a single central character in - the palindrome when there are an odd number of characters, or nothing - when there are an even number of characters, but in order to work it - has to be able to try the second case when the rest of the pattern + The second branch in the group matches a single central character in + the palindrome when there are an odd number of characters, or nothing + when there are an even number of characters, but in order to work it + has to be able to try the second case when the rest of the pattern match fails. If you want to match typical palindromic phrases, the pat- - tern has to ignore all non-word characters, which can be done like + tern has to ignore all non-word characters, which can be done like this: ^\W*+((.)\W*+(?1)\W*+\2|\W*+.?)\W*+$ - If run with the PCRE2_CASELESS option, this pattern matches phrases - such as "A man, a plan, a canal: Panama!". Note the use of the posses- - sive quantifier *+ to avoid backtracking into sequences of non-word + If run with the PCRE2_CASELESS option, this pattern matches phrases + such as "A man, a plan, a canal: Panama!". Note the use of the posses- + sive quantifier *+ to avoid backtracking into sequences of non-word characters. Without this, PCRE2 takes a great deal longer (ten times or - more) to match typical phrases, and Perl takes so long that you think + more) to match typical phrases, and Perl takes so long that you think it has gone into a loop. - Another way in which PCRE2 and Perl used to differ in their recursion - processing is in the handling of captured values. Formerly in Perl, - when a group was called recursively or as a subroutine (see the next + Another way in which PCRE2 and Perl used to differ in their recursion + processing is in the handling of captured values. Formerly in Perl, + when a group was called recursively or as a subroutine (see the next section), it had no access to any values that were captured outside the - recursion, whereas in PCRE2 these values can be referenced. Consider + recursion, whereas in PCRE2 these values can be referenced. Consider this pattern: ^(.)(\1|a(?2)) - This pattern matches "bab". The first capturing parentheses match "b", + This pattern matches "bab". The first capturing parentheses match "b", then in the second group, when the backreference \1 fails to match "b", the second alternative matches "a" and then recurses. In the recursion, - \1 does now match "b" and so the whole match succeeds. This match used + \1 does now match "b" and so the whole match succeeds. This match used to fail in Perl, but in later versions (I tried 5.024) it now works. GROUPS AS SUBROUTINES - If the syntax for a recursive group call (either by number or by name) - is used outside the parentheses to which it refers, it operates a bit - like a subroutine in a programming language. More accurately, PCRE2 + If the syntax for a recursive group call (either by number or by name) + is used outside the parentheses to which it refers, it operates a bit + like a subroutine in a programming language. More accurately, PCRE2 treats the referenced group as an independent subpattern which it tries - to match at the current matching position. The called group may be - defined before or after the reference. A numbered reference can be + to match at the current matching position. The called group may be + defined before or after the reference. A numbered reference can be absolute or relative, as in these examples: (...(absolute)...)...(?2)... @@ -8792,106 +8816,106 @@ GROUPS AS SUBROUTINES (sens|respons)e and \1ibility - matches "sense and sensibility" and "response and responsibility", but + matches "sense and sensibility" and "response and responsibility", but not "sense and responsibility". If instead the pattern (sens|respons)e and (?1)ibility - is used, it does match "sense and responsibility" as well as the other - two strings. Another example is given in the discussion of DEFINE + is used, it does match "sense and responsibility" as well as the other + two strings. Another example is given in the discussion of DEFINE above. - Like recursions, subroutine calls used to be treated as atomic, but - this changed at PCRE2 release 10.30, so backtracking into subroutine - calls can now occur. However, any capturing parentheses that are set + Like recursions, subroutine calls used to be treated as atomic, but + this changed at PCRE2 release 10.30, so backtracking into subroutine + calls can now occur. However, any capturing parentheses that are set during the subroutine call revert to their previous values afterwards. - Processing options such as case-independence are fixed when a group is - defined, so if it is used as a subroutine, such options cannot be + Processing options such as case-independence are fixed when a group is + defined, so if it is used as a subroutine, such options cannot be changed for different calls. For example, consider this pattern: (abc)(?i:(?-1)) - It matches "abcabc". It does not match "abcABC" because the change of + It matches "abcabc". It does not match "abcABC" because the change of processing option does not affect the called group. - The behaviour of backtracking control verbs in groups when called as + The behaviour of backtracking control verbs in groups when called as subroutines is described in the section entitled "Backtracking verbs in subroutines" below. ONIGURUMA SUBROUTINE SYNTAX - For compatibility with Oniguruma, the non-Perl syntax \g followed by a + For compatibility with Oniguruma, the non-Perl syntax \g followed by a name or a number enclosed either in angle brackets or single quotes, is - an alternative syntax for calling a group as a subroutine, possibly - recursively. Here are two of the examples used above, rewritten using + an alternative syntax for calling a group as a subroutine, possibly + recursively. Here are two of the examples used above, rewritten using this syntax: (?<pn> \( ( (?>[^()]+) | \g<pn> )* \) ) (sens|respons)e and \g'1'ibility - PCRE2 supports an extension to Oniguruma: if a number is preceded by a + PCRE2 supports an extension to Oniguruma: if a number is preceded by a plus or a minus sign it is taken as a relative reference. For example: (abc)(?i:\g<-1>) - Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not - synonymous. The former is a backreference; the latter is a subroutine + Note that \g{...} (Perl syntax) and \g<...> (Oniguruma syntax) are not + synonymous. The former is a backreference; the latter is a subroutine call. CALLOUTS Perl has a feature whereby using the sequence (?{...}) causes arbitrary - Perl code to be obeyed in the middle of matching a regular expression. + Perl code to be obeyed in the middle of matching a regular expression. This makes it possible, amongst other things, to extract different sub- strings that match the same pair of parentheses when there is a repeti- tion. - PCRE2 provides a similar feature, but of course it cannot obey arbi- - trary Perl code. The feature is called "callout". The caller of PCRE2 - provides an external function by putting its entry point in a match - context using the function pcre2_set_callout(), and then passing that - context to pcre2_match() or pcre2_dfa_match(). If no match context is + PCRE2 provides a similar feature, but of course it cannot obey arbi- + trary Perl code. The feature is called "callout". The caller of PCRE2 + provides an external function by putting its entry point in a match + context using the function pcre2_set_callout(), and then passing that + context to pcre2_match() or pcre2_dfa_match(). If no match context is passed, or if the callout entry point is set to NULL, callouts are dis- abled. - Within a regular expression, (?C<arg>) indicates a point at which the - external function is to be called. There are two kinds of callout: - those with a numerical argument and those with a string argument. (?C) - on its own with no argument is treated as (?C0). A numerical argument - allows the application to distinguish between different callouts. - String arguments were added for release 10.20 to make it possible for - script languages that use PCRE2 to embed short scripts within patterns + Within a regular expression, (?C<arg>) indicates a point at which the + external function is to be called. There are two kinds of callout: + those with a numerical argument and those with a string argument. (?C) + on its own with no argument is treated as (?C0). A numerical argument + allows the application to distinguish between different callouts. + String arguments were added for release 10.20 to make it possible for + script languages that use PCRE2 to embed short scripts within patterns in a similar way to Perl. During matching, when PCRE2 reaches a callout point, the external func- - tion is called. It is provided with the number or string argument of - the callout, the position in the pattern, and one item of data that is + tion is called. It is provided with the number or string argument of + the callout, the position in the pattern, and one item of data that is also set in the match block. The callout function may cause matching to proceed, to backtrack, or to fail. - By default, PCRE2 implements a number of optimizations at matching - time, and one side-effect is that sometimes callouts are skipped. If - you need all possible callouts to happen, you need to set options that - disable the relevant optimizations. More details, including a complete - description of the programming interface to the callout function, are + By default, PCRE2 implements a number of optimizations at matching + time, and one side-effect is that sometimes callouts are skipped. If + you need all possible callouts to happen, you need to set options that + disable the relevant optimizations. More details, including a complete + description of the programming interface to the callout function, are given in the pcre2callout documentation. Callouts with numerical arguments - If you just want to have a means of identifying different callout - points, put a number less than 256 after the letter C. For example, + If you just want to have a means of identifying different callout + points, put a number less than 256 after the letter C. For example, this pattern has two callout points: (?C1)abc(?C2)def - If the PCRE2_AUTO_CALLOUT flag is passed to pcre2_compile(), numerical - callouts are automatically installed before each item in the pattern. - They are all numbered 255. If there is a conditional group in the pat- + If the PCRE2_AUTO_CALLOUT flag is passed to pcre2_compile(), numerical + callouts are automatically installed before each item in the pattern. + They are all numbered 255. If there is a conditional group in the pat- tern whose condition is an assertion, an additional callout is inserted - just before the condition. An explicit callout may also be set at this + just before the condition. An explicit callout may also be set at this position, as in this example: (?(?C9)(?=a)abc|def) @@ -8901,78 +8925,78 @@ CALLOUTS Callouts with string arguments - A delimited string may be used instead of a number as a callout argu- - ment. The starting delimiter must be one of ` ' " ^ % # $ { and the + A delimited string may be used instead of a number as a callout argu- + ment. The starting delimiter must be one of ` ' " ^ % # $ { and the ending delimiter is the same as the start, except for {, where the end- - ing delimiter is }. If the ending delimiter is needed within the + ing delimiter is }. If the ending delimiter is needed within the string, it must be doubled. For example: (?C'ab ''c'' d')xyz(?C{any text})pqr - The doubling is removed before the string is passed to the callout + The doubling is removed before the string is passed to the callout function. BACKTRACKING CONTROL - There are a number of special "Backtracking Control Verbs" (to use - Perl's terminology) that modify the behaviour of backtracking during - matching. They are generally of the form (*VERB) or (*VERB:NAME). Some - verbs take either form, possibly behaving differently depending on - whether or not a name is present. The names are not required to be + There are a number of special "Backtracking Control Verbs" (to use + Perl's terminology) that modify the behaviour of backtracking during + matching. They are generally of the form (*VERB) or (*VERB:NAME). Some + verbs take either form, possibly behaving differently depending on + whether or not a name is present. The names are not required to be unique within the pattern. - By default, for compatibility with Perl, a name is any sequence of + By default, for compatibility with Perl, a name is any sequence of characters that does not include a closing parenthesis. The name is not - processed in any way, and it is not possible to include a closing - parenthesis in the name. This can be changed by setting the - PCRE2_ALT_VERBNAMES option, but the result is no longer Perl-compati- + processed in any way, and it is not possible to include a closing + parenthesis in the name. This can be changed by setting the + PCRE2_ALT_VERBNAMES option, but the result is no longer Perl-compati- ble. - When PCRE2_ALT_VERBNAMES is set, backslash processing is applied to - verb names and only an unescaped closing parenthesis terminates the - name. However, the only backslash items that are permitted are \Q, \E, - and sequences such as \x{100} that define character code points. Char- + When PCRE2_ALT_VERBNAMES is set, backslash processing is applied to + verb names and only an unescaped closing parenthesis terminates the + name. However, the only backslash items that are permitted are \Q, \E, + and sequences such as \x{100} that define character code points. Char- acter type escapes such as \d are faulted. A closing parenthesis can be included in a name either as \) or between - \Q and \E. In addition to backslash processing, if the PCRE2_EXTENDED + \Q and \E. In addition to backslash processing, if the PCRE2_EXTENDED or PCRE2_EXTENDED_MORE option is also set, unescaped whitespace in verb names is skipped, and #-comments are recognized, exactly as in the rest - of the pattern. PCRE2_EXTENDED and PCRE2_EXTENDED_MORE do not affect + of the pattern. PCRE2_EXTENDED and PCRE2_EXTENDED_MORE do not affect verb names unless PCRE2_ALT_VERBNAMES is also set. - The maximum length of a name is 255 in the 8-bit library and 65535 in - the 16-bit and 32-bit libraries. If the name is empty, that is, if the - closing parenthesis immediately follows the colon, the effect is as if + The maximum length of a name is 255 in the 8-bit library and 65535 in + the 16-bit and 32-bit libraries. If the name is empty, that is, if the + closing parenthesis immediately follows the colon, the effect is as if the colon were not there. Any number of these verbs may occur in a pat- tern. - Since these verbs are specifically related to backtracking, most of - them can be used only when the pattern is to be matched using the tra- + Since these verbs are specifically related to backtracking, most of + them can be used only when the pattern is to be matched using the tra- ditional matching function, because that uses a backtracking algorithm. - With the exception of (*FAIL), which behaves like a failing negative + With the exception of (*FAIL), which behaves like a failing negative assertion, the backtracking control verbs cause an error if encountered by the DFA matching function. - The behaviour of these verbs in repeated groups, assertions, and in - capture groups called as subroutines (whether or not recursively) is + The behaviour of these verbs in repeated groups, assertions, and in + capture groups called as subroutines (whether or not recursively) is documented below. Optimizations that affect backtracking verbs PCRE2 contains some optimizations that are used to speed up matching by running some checks at the start of each match attempt. For example, it - may know the minimum length of matching subject, or that a particular + may know the minimum length of matching subject, or that a particular character must be present. When one of these optimizations bypasses the - running of a match, any included backtracking verbs will not, of + running of a match, any included backtracking verbs will not, of course, be processed. You can suppress the start-of-match optimizations - by setting the PCRE2_NO_START_OPTIMIZE option when calling pcre2_com- - pile(), or by starting the pattern with (*NO_START_OPT). There is more + by setting the PCRE2_NO_START_OPTIMIZE option when calling pcre2_com- + pile(), or by starting the pattern with (*NO_START_OPT). There is more discussion of this option in the section entitled "Compiling a pattern" in the pcre2api documentation. - Experiments with Perl suggest that it too has similar optimizations, + Experiments with Perl suggest that it too has similar optimizations, and like PCRE2, turning them off can change the result of a match. Verbs that act immediately @@ -8981,64 +9005,64 @@ BACKTRACKING CONTROL (*ACCEPT) or (*ACCEPT:NAME) - This verb causes the match to end successfully, skipping the remainder - of the pattern. However, when it is inside a capture group that is + This verb causes the match to end successfully, skipping the remainder + of the pattern. However, when it is inside a capture group that is called as a subroutine, only that group is ended successfully. Matching then continues at the outer level. If (*ACCEPT) in triggered in a posi- - tive assertion, the assertion succeeds; in a negative assertion, the + tive assertion, the assertion succeeds; in a negative assertion, the assertion fails. - If (*ACCEPT) is inside capturing parentheses, the data so far is cap- + If (*ACCEPT) is inside capturing parentheses, the data so far is cap- tured. For example: A((?:A|B(*ACCEPT)|C)D) - This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap- + This matches "AB", "AAD", or "ACD"; when it matches "AB", "B" is cap- tured by the outer parentheses. - Warning: (*ACCEPT) should not be used within a script run group, - because it causes an immediate exit from the group, bypassing the + Warning: (*ACCEPT) should not be used within a script run group, + because it causes an immediate exit from the group, bypassing the script run checking. (*FAIL) or (*FAIL:NAME) - This verb causes a matching failure, forcing backtracking to occur. It - may be abbreviated to (*F). It is equivalent to (?!) but easier to + This verb causes a matching failure, forcing backtracking to occur. It + may be abbreviated to (*F). It is equivalent to (?!) but easier to read. The Perl documentation notes that it is probably useful only when combined with (?{}) or (??{}). Those are, of course, Perl features that - are not present in PCRE2. The nearest equivalent is the callout fea- + are not present in PCRE2. The nearest equivalent is the callout fea- ture, as for example in this pattern: a+(?C)(*FAIL) - A match with the string "aaaa" always fails, but the callout is taken + A match with the string "aaaa" always fails, but the callout is taken before each backtrack happens (in this example, 10 times). - (*ACCEPT:NAME) and (*FAIL:NAME) are treated as (*MARK:NAME)(*ACCEPT) + (*ACCEPT:NAME) and (*FAIL:NAME) are treated as (*MARK:NAME)(*ACCEPT) and (*MARK:NAME)(*FAIL), respectively. Recording which path was taken - There is one verb whose main purpose is to track how a match was - arrived at, though it also has a secondary use in conjunction with + There is one verb whose main purpose is to track how a match was + arrived at, though it also has a secondary use in conjunction with advancing the match starting point (see (*SKIP) below). (*MARK:NAME) or (*:NAME) - A name is always required with this verb. For all the other backtrack- + A name is always required with this verb. For all the other backtrack- ing control verbs, a NAME argument is optional. - When a match succeeds, the name of the last-encountered mark name on + When a match succeeds, the name of the last-encountered mark name on the matching path is passed back to the caller as described in the sec- tion entitled "Other information about the match" in the pcre2api docu- - mentation. This applies to all instances of (*MARK) and other verbs, + mentation. This applies to all instances of (*MARK) and other verbs, including those inside assertions and atomic groups. However, there are - differences in those cases when (*MARK) is used in conjunction with + differences in those cases when (*MARK) is used in conjunction with (*SKIP) as described below. - The mark name that was last encountered on the matching path is passed - back. A verb without a NAME argument is ignored for this purpose. Here - is an example of pcre2test output, where the "mark" modifier requests + The mark name that was last encountered on the matching path is passed + back. A verb without a NAME argument is ignored for this purpose. Here + is an example of pcre2test output, where the "mark" modifier requests the retrieval and outputting of (*MARK) data: re> /X(*MARK:A)Y|X(*MARK:B)Z/mark @@ -9050,76 +9074,76 @@ BACKTRACKING CONTROL MK: B The (*MARK) name is tagged with "MK:" in this output, and in this exam- - ple it indicates which of the two alternatives matched. This is a more - efficient way of obtaining this information than putting each alterna- + ple it indicates which of the two alternatives matched. This is a more + efficient way of obtaining this information than putting each alterna- tive in its own capturing parentheses. - If a verb with a name is encountered in a positive assertion that is - true, the name is recorded and passed back if it is the last-encoun- + If a verb with a name is encountered in a positive assertion that is + true, the name is recorded and passed back if it is the last-encoun- tered. This does not happen for negative assertions or failing positive assertions. - After a partial match or a failed match, the last encountered name in + After a partial match or a failed match, the last encountered name in the entire match process is returned. For example: re> /X(*MARK:A)Y|X(*MARK:B)Z/mark data> XP No match, mark = B - Note that in this unanchored example the mark is retained from the + Note that in this unanchored example the mark is retained from the match attempt that started at the letter "X" in the subject. Subsequent match attempts starting at "P" and then with an empty string do not get as far as the (*MARK) item, but nevertheless do not reset it. - If you are interested in (*MARK) values after failed matches, you - should probably set the PCRE2_NO_START_OPTIMIZE option (see above) to + If you are interested in (*MARK) values after failed matches, you + should probably set the PCRE2_NO_START_OPTIMIZE option (see above) to ensure that the match is always attempted. Verbs that act after backtracking The following verbs do nothing when they are encountered. Matching con- - tinues with what follows, but if there is a subsequent match failure, - causing a backtrack to the verb, a failure is forced. That is, back- - tracking cannot pass to the left of the verb. However, when one of + tinues with what follows, but if there is a subsequent match failure, + causing a backtrack to the verb, a failure is forced. That is, back- + tracking cannot pass to the left of the verb. However, when one of these verbs appears inside an atomic group or in a lookaround assertion - that is true, its effect is confined to that group, because once the - group has been matched, there is never any backtracking into it. Back- + that is true, its effect is confined to that group, because once the + group has been matched, there is never any backtracking into it. Back- tracking from beyond an assertion or an atomic group ignores the entire group, and seeks a preceding backtracking point. - These verbs differ in exactly what kind of failure occurs when back- - tracking reaches them. The behaviour described below is what happens - when the verb is not in a subroutine or an assertion. Subsequent sec- + These verbs differ in exactly what kind of failure occurs when back- + tracking reaches them. The behaviour described below is what happens + when the verb is not in a subroutine or an assertion. Subsequent sec- tions cover these special cases. (*COMMIT) or (*COMMIT:NAME) - This verb causes the whole match to fail outright if there is a later + This verb causes the whole match to fail outright if there is a later matching failure that causes backtracking to reach it. Even if the pat- - tern is unanchored, no further attempts to find a match by advancing - the starting point take place. If (*COMMIT) is the only backtracking + tern is unanchored, no further attempts to find a match by advancing + the starting point take place. If (*COMMIT) is the only backtracking verb that is encountered, once it has been passed pcre2_match() is com- mitted to finding a match at the current starting point, or not at all. For example: a+(*COMMIT)b - This matches "xxaab" but not "aacaab". It can be thought of as a kind + This matches "xxaab" but not "aacaab". It can be thought of as a kind of dynamic anchor, or "I've started, so I must finish." - The behaviour of (*COMMIT:NAME) is not the same as (*MARK:NAME)(*COM- - MIT). It is like (*MARK:NAME) in that the name is remembered for pass- - ing back to the caller. However, (*SKIP:NAME) searches only for names + The behaviour of (*COMMIT:NAME) is not the same as (*MARK:NAME)(*COM- + MIT). It is like (*MARK:NAME) in that the name is remembered for pass- + ing back to the caller. However, (*SKIP:NAME) searches only for names that are set with (*MARK), ignoring those set by any of the other back- tracking verbs. - If there is more than one backtracking verb in a pattern, a different - one that follows (*COMMIT) may be triggered first, so merely passing + If there is more than one backtracking verb in a pattern, a different + one that follows (*COMMIT) may be triggered first, so merely passing (*COMMIT) during a match does not always guarantee that a match must be at this starting point. - Note that (*COMMIT) at the start of a pattern is not the same as an - anchor, unless PCRE2's start-of-match optimizations are turned off, as + Note that (*COMMIT) at the start of a pattern is not the same as an + anchor, unless PCRE2's start-of-match optimizations are turned off, as shown in this output from pcre2test: re> /(*COMMIT)abc/ @@ -9130,63 +9154,63 @@ BACKTRACKING CONTROL data> xyzabc No match - For the first pattern, PCRE2 knows that any match must start with "a", - so the optimization skips along the subject to "a" before applying the - pattern to the first set of data. The match attempt then succeeds. The - second pattern disables the optimization that skips along to the first - character. The pattern is now applied starting at "x", and so the - (*COMMIT) causes the match to fail without trying any other starting + For the first pattern, PCRE2 knows that any match must start with "a", + so the optimization skips along the subject to "a" before applying the + pattern to the first set of data. The match attempt then succeeds. The + second pattern disables the optimization that skips along to the first + character. The pattern is now applied starting at "x", and so the + (*COMMIT) causes the match to fail without trying any other starting points. (*PRUNE) or (*PRUNE:NAME) - This verb causes the match to fail at the current starting position in + This verb causes the match to fail at the current starting position in the subject if there is a later matching failure that causes backtrack- - ing to reach it. If the pattern is unanchored, the normal "bumpalong" - advance to the next starting character then happens. Backtracking can - occur as usual to the left of (*PRUNE), before it is reached, or when - matching to the right of (*PRUNE), but if there is no match to the - right, backtracking cannot cross (*PRUNE). In simple cases, the use of - (*PRUNE) is just an alternative to an atomic group or possessive quan- + ing to reach it. If the pattern is unanchored, the normal "bumpalong" + advance to the next starting character then happens. Backtracking can + occur as usual to the left of (*PRUNE), before it is reached, or when + matching to the right of (*PRUNE), but if there is no match to the + right, backtracking cannot cross (*PRUNE). In simple cases, the use of + (*PRUNE) is just an alternative to an atomic group or possessive quan- tifier, but there are some uses of (*PRUNE) that cannot be expressed in - any other way. In an anchored pattern (*PRUNE) has the same effect as + any other way. In an anchored pattern (*PRUNE) has the same effect as (*COMMIT). The behaviour of (*PRUNE:NAME) is not the same as (*MARK:NAME)(*PRUNE). It is like (*MARK:NAME) in that the name is remembered for passing back - to the caller. However, (*SKIP:NAME) searches only for names set with + to the caller. However, (*SKIP:NAME) searches only for names set with (*MARK), ignoring those set by other backtracking verbs. (*SKIP) - This verb, when given without a name, is like (*PRUNE), except that if - the pattern is unanchored, the "bumpalong" advance is not to the next + This verb, when given without a name, is like (*PRUNE), except that if + the pattern is unanchored, the "bumpalong" advance is not to the next character, but to the position in the subject where (*SKIP) was encoun- - tered. (*SKIP) signifies that whatever text was matched leading up to - it cannot be part of a successful match if there is a later mismatch. + tered. (*SKIP) signifies that whatever text was matched leading up to + it cannot be part of a successful match if there is a later mismatch. Consider: a+(*SKIP)b - If the subject is "aaaac...", after the first match attempt fails - (starting at the first character in the string), the starting point + If the subject is "aaaac...", after the first match attempt fails + (starting at the first character in the string), the starting point skips on to start the next attempt at "c". Note that a possessive quan- - tifer does not have the same effect as this example; although it would - suppress backtracking during the first match attempt, the second - attempt would start at the second character instead of skipping on to + tifer does not have the same effect as this example; although it would + suppress backtracking during the first match attempt, the second + attempt would start at the second character instead of skipping on to "c". (*SKIP:NAME) - When (*SKIP) has an associated name, its behaviour is modified. When - such a (*SKIP) is triggered, the previous path through the pattern is - searched for the most recent (*MARK) that has the same name. If one is - found, the "bumpalong" advance is to the subject position that corre- - sponds to that (*MARK) instead of to where (*SKIP) was encountered. If + When (*SKIP) has an associated name, its behaviour is modified. When + such a (*SKIP) is triggered, the previous path through the pattern is + searched for the most recent (*MARK) that has the same name. If one is + found, the "bumpalong" advance is to the subject position that corre- + sponds to that (*MARK) instead of to where (*SKIP) was encountered. If no (*MARK) with a matching name is found, the (*SKIP) is ignored. - The search for a (*MARK) name uses the normal backtracking mechanism, - which means that it does not see (*MARK) settings that are inside + The search for a (*MARK) name uses the normal backtracking mechanism, + which means that it does not see (*MARK) settings that are inside atomic groups or assertions, because they are never re-entered by back- tracking. Compare the following pcre2test examples: @@ -9200,105 +9224,105 @@ BACKTRACKING CONTROL 0: b 1: b - In the first example, the (*MARK) setting is in an atomic group, so it + In the first example, the (*MARK) setting is in an atomic group, so it is not seen when (*SKIP:X) triggers, causing the (*SKIP) to be ignored. - This allows the second branch of the pattern to be tried at the first - character position. In the second example, the (*MARK) setting is not - in an atomic group. This allows (*SKIP:X) to find the (*MARK) when it + This allows the second branch of the pattern to be tried at the first + character position. In the second example, the (*MARK) setting is not + in an atomic group. This allows (*SKIP:X) to find the (*MARK) when it backtracks, and this causes a new matching attempt to start at the sec- - ond character. This time, the (*MARK) is never seen because "a" does + ond character. This time, the (*MARK) is never seen because "a" does not match "b", so the matcher immediately jumps to the second branch of the pattern. - Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It + Note that (*SKIP:NAME) searches only for names set by (*MARK:NAME). It ignores names that are set by other backtracking verbs. (*THEN) or (*THEN:NAME) - This verb causes a skip to the next innermost alternative when back- - tracking reaches it. That is, it cancels any further backtracking - within the current alternative. Its name comes from the observation + This verb causes a skip to the next innermost alternative when back- + tracking reaches it. That is, it cancels any further backtracking + within the current alternative. Its name comes from the observation that it can be used for a pattern-based if-then-else block: ( COND1 (*THEN) FOO | COND2 (*THEN) BAR | COND3 (*THEN) BAZ ) ... - If the COND1 pattern matches, FOO is tried (and possibly further items - after the end of the group if FOO succeeds); on failure, the matcher - skips to the second alternative and tries COND2, without backtracking - into COND1. If that succeeds and BAR fails, COND3 is tried. If subse- - quently BAZ fails, there are no more alternatives, so there is a back- - track to whatever came before the entire group. If (*THEN) is not + If the COND1 pattern matches, FOO is tried (and possibly further items + after the end of the group if FOO succeeds); on failure, the matcher + skips to the second alternative and tries COND2, without backtracking + into COND1. If that succeeds and BAR fails, COND3 is tried. If subse- + quently BAZ fails, there are no more alternatives, so there is a back- + track to whatever came before the entire group. If (*THEN) is not inside an alternation, it acts like (*PRUNE). - The behaviour of (*THEN:NAME) is not the same as (*MARK:NAME)(*THEN). + The behaviour of (*THEN:NAME) is not the same as (*MARK:NAME)(*THEN). It is like (*MARK:NAME) in that the name is remembered for passing back - to the caller. However, (*SKIP:NAME) searches only for names set with + to the caller. However, (*SKIP:NAME) searches only for names set with (*MARK), ignoring those set by other backtracking verbs. - A group that does not contain a | character is just a part of the - enclosing alternative; it is not a nested alternation with only one - alternative. The effect of (*THEN) extends beyond such a group to the - enclosing alternative. Consider this pattern, where A, B, etc. are - complex pattern fragments that do not contain any | characters at this + A group that does not contain a | character is just a part of the + enclosing alternative; it is not a nested alternation with only one + alternative. The effect of (*THEN) extends beyond such a group to the + enclosing alternative. Consider this pattern, where A, B, etc. are + complex pattern fragments that do not contain any | characters at this level: A (B(*THEN)C) | D - If A and B are matched, but there is a failure in C, matching does not + If A and B are matched, but there is a failure in C, matching does not backtrack into A; instead it moves to the next alternative, that is, D. - However, if the group containing (*THEN) is given an alternative, it + However, if the group containing (*THEN) is given an alternative, it behaves differently: A (B(*THEN)C | (*FAIL)) | D The effect of (*THEN) is now confined to the inner group. After a fail- - ure in C, matching moves to (*FAIL), which causes the whole group to - fail because there are no more alternatives to try. In this case, + ure in C, matching moves to (*FAIL), which causes the whole group to + fail because there are no more alternatives to try. In this case, matching does backtrack into A. - Note that a conditional group is not considered as having two alterna- - tives, because only one is ever used. In other words, the | character - in a conditional group has a different meaning. Ignoring white space, + Note that a conditional group is not considered as having two alterna- + tives, because only one is ever used. In other words, the | character + in a conditional group has a different meaning. Ignoring white space, consider: ^.*? (?(?=a) a | b(*THEN)c ) - If the subject is "ba", this pattern does not match. Because .*? is - ungreedy, it initially matches zero characters. The condition (?=a) - then fails, the character "b" is matched, but "c" is not. At this - point, matching does not backtrack to .*? as might perhaps be expected - from the presence of the | character. The conditional group is part of - the single alternative that comprises the whole pattern, and so the - match fails. (If there was a backtrack into .*?, allowing it to match + If the subject is "ba", this pattern does not match. Because .*? is + ungreedy, it initially matches zero characters. The condition (?=a) + then fails, the character "b" is matched, but "c" is not. At this + point, matching does not backtrack to .*? as might perhaps be expected + from the presence of the | character. The conditional group is part of + the single alternative that comprises the whole pattern, and so the + match fails. (If there was a backtrack into .*?, allowing it to match "b", the match would succeed.) - The verbs just described provide four different "strengths" of control + The verbs just described provide four different "strengths" of control when subsequent matching fails. (*THEN) is the weakest, carrying on the - match at the next alternative. (*PRUNE) comes next, failing the match - at the current starting position, but allowing an advance to the next - character (for an unanchored pattern). (*SKIP) is similar, except that + match at the next alternative. (*PRUNE) comes next, failing the match + at the current starting position, but allowing an advance to the next + character (for an unanchored pattern). (*SKIP) is similar, except that the advance may be more than one character. (*COMMIT) is the strongest, causing the entire match to fail. More than one backtracking verb - If more than one backtracking verb is present in a pattern, the one - that is backtracked onto first acts. For example, consider this pat- + If more than one backtracking verb is present in a pattern, the one + that is backtracked onto first acts. For example, consider this pat- tern, where A, B, etc. are complex pattern fragments: (A(*COMMIT)B(*THEN)C|ABD) - If A matches but B fails, the backtrack to (*COMMIT) causes the entire + If A matches but B fails, the backtrack to (*COMMIT) causes the entire match to fail. However, if A and B match, but C fails, the backtrack to - (*THEN) causes the next alternative (ABD) to be tried. This behaviour - is consistent, but is not always the same as Perl's. It means that if - two or more backtracking verbs appear in succession, all the the last + (*THEN) causes the next alternative (ABD) to be tried. This behaviour + is consistent, but is not always the same as Perl's. It means that if + two or more backtracking verbs appear in succession, all the the last of them has no effect. Consider this example: ...(*COMMIT)(*PRUNE)... If there is a matching failure to the right, backtracking onto (*PRUNE) - causes it to be triggered, and its action is taken. There can never be + causes it to be triggered, and its action is taken. There can never be a backtrack onto (*COMMIT). Backtracking verbs in repeated groups @@ -9308,42 +9332,42 @@ BACKTRACKING CONTROL /(a(*COMMIT)b)+ac/ - If the subject is "abac", Perl matches unless its optimizations are - disabled, but PCRE2 always fails because the (*COMMIT) in the second + If the subject is "abac", Perl matches unless its optimizations are + disabled, but PCRE2 always fails because the (*COMMIT) in the second repeat of the group acts. Backtracking verbs in assertions - (*FAIL) in any assertion has its normal effect: it forces an immediate - backtrack. The behaviour of the other backtracking verbs depends on - whether or not the assertion is standalone or acting as the condition + (*FAIL) in any assertion has its normal effect: it forces an immediate + backtrack. The behaviour of the other backtracking verbs depends on + whether or not the assertion is standalone or acting as the condition in a conditional group. - (*ACCEPT) in a standalone positive assertion causes the assertion to - succeed without any further processing; captured strings and a mark - name (if set) are retained. In a standalone negative assertion, - (*ACCEPT) causes the assertion to fail without any further processing; + (*ACCEPT) in a standalone positive assertion causes the assertion to + succeed without any further processing; captured strings and a mark + name (if set) are retained. In a standalone negative assertion, + (*ACCEPT) causes the assertion to fail without any further processing; captured substrings and any mark name are discarded. - If the assertion is a condition, (*ACCEPT) causes the condition to be - true for a positive assertion and false for a negative one; captured + If the assertion is a condition, (*ACCEPT) causes the condition to be + true for a positive assertion and false for a negative one; captured substrings are retained in both cases. The remaining verbs act only when a later failure causes a backtrack to - reach them. This means that their effect is confined to the assertion, + reach them. This means that their effect is confined to the assertion, because lookaround assertions are atomic. A backtrack that occurs after an assertion is complete does not jump back into the assertion. Note in - particular that a (*MARK) name that is set in an assertion is not + particular that a (*MARK) name that is set in an assertion is not "seen" by an instance of (*SKIP:NAME) latter in the pattern. - The effect of (*THEN) is not allowed to escape beyond an assertion. If - there are no more branches to try, (*THEN) causes a positive assertion + The effect of (*THEN) is not allowed to escape beyond an assertion. If + there are no more branches to try, (*THEN) causes a positive assertion to be false, and a negative assertion to be true. - The other backtracking verbs are not treated specially if they appear - in a standalone positive assertion. In a conditional positive asser- + The other backtracking verbs are not treated specially if they appear + in a standalone positive assertion. In a conditional positive asser- tion, backtracking (from within the assertion) into (*COMMIT), (*SKIP), - or (*PRUNE) causes the condition to be false. However, for both stand- + or (*PRUNE) causes the condition to be false. However, for both stand- alone and conditional negative assertions, backtracking into (*COMMIT), (*SKIP), or (*PRUNE) causes the assertion to be true, without consider- ing any further alternative branches. @@ -9353,26 +9377,26 @@ BACKTRACKING CONTROL These behaviours occur whether or not the group is called recursively. (*ACCEPT) in a group called as a subroutine causes the subroutine match - to succeed without any further processing. Matching then continues + to succeed without any further processing. Matching then continues after the subroutine call. Perl documents this behaviour. Perl's treat- ment of the other verbs in subroutines is different in some cases. - (*FAIL) in a group called as a subroutine has its normal effect: it + (*FAIL) in a group called as a subroutine has its normal effect: it forces an immediate backtrack. - (*COMMIT), (*SKIP), and (*PRUNE) cause the subroutine match to fail - when triggered by being backtracked to in a group called as a subrou- + (*COMMIT), (*SKIP), and (*PRUNE) cause the subroutine match to fail + when triggered by being backtracked to in a group called as a subrou- tine. There is then a backtrack at the outer level. (*THEN), when triggered, skips to the next alternative in the innermost - enclosing group that has alternatives (its normal behaviour). However, + enclosing group that has alternatives (its normal behaviour). However, if there is no such group within the subroutine's group, the subroutine match fails and there is a backtrack at the outer level. SEE ALSO - pcre2api(3), pcre2callout(3), pcre2matching(3), pcre2syntax(3), + pcre2api(3), pcre2callout(3), pcre2matching(3), pcre2syntax(3), pcre2(3). @@ -9385,11 +9409,11 @@ AUTHOR REVISION - Last updated: 12 February 2019 + Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2PERFORM(3) Library Functions Manual PCRE2PERFORM(3) @@ -9623,8 +9647,8 @@ REVISION Last updated: 03 February 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2POSIX(3) Library Functions Manual PCRE2POSIX(3) @@ -9953,8 +9977,8 @@ REVISION Last updated: 30 January 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2SAMPLE(3) Library Functions Manual PCRE2SAMPLE(3) @@ -10232,8 +10256,8 @@ REVISION Last updated: 27 June 2018 Copyright (c) 1997-2018 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2SYNTAX(3) Library Functions Manual PCRE2SYNTAX(3) @@ -10733,8 +10757,8 @@ REVISION Last updated: 11 February 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + PCRE2UNICODE(3) Library Functions Manual PCRE2UNICODE(3) @@ -10744,21 +10768,29 @@ NAME UNICODE AND UTF SUPPORT - 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 pcre2_compile() 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 sub- - ject strings that are matched against it are treated as UTF strings - instead of strings of individual one-code-unit characters. There are - also some other changes to the way characters are handled, as docu- - mented below. + PCRE2 is normally built with Unicode support, though if you do not need + it, you can build it without, in which case the library will be + smaller. With Unicode support, PCRE2 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), but this is not the default. + Unless specifically requested, PCRE2 treats each code unit in a string + as one character. + + There are two ways of telling PCRE2 to switch to UTF mode, where char- + acters may consist of more than one code unit and the range of values + is constrained. The program can call pcre2_compile() with the PCRE2_UTF + option, or the pattern may start with the sequence (*UTF). However, + the latter facility can be locked out by the PCRE2_NEVER_UTF option. + That is, the programmer can prevent the supplier of the pattern from + switching to UTF mode. + + Note that the PCRE2_MATCH_INVALID_UTF option (see below) forces + PCRE2_UTF to be set. - If you do not need Unicode support you can build PCRE2 without it, in - which case the library will be smaller. + In UTF mode, 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. There are also some other changes to the way + characters are handled, as documented below. UNICODE PROPERTY SUPPORT @@ -10785,18 +10817,18 @@ WIDE CHARACTERS AND UTF MODES The escape sequence \N{U+<hex digits>} is recognized as another way of specifying a Unicode character by code point in a UTF mode. It is not - allowed in non-UTF modes. + allowed in non-UTF mode. - In UTF modes, repeat quantifiers apply to complete UTF characters, not + In UTF mode, repeat quantifiers apply to complete UTF characters, not to individual code units. - In UTF modes, the dot metacharacter matches one UTF character instead - of a single code unit. + In UTF mode, the dot metacharacter matches one UTF character instead of + a single code unit. - In UTF modes, capture group names are not restricted to ASCII, and may + In UTF mode, capture group names are not restricted to ASCII, and may contain any Unicode letters and decimal digits, as well as underscore. - The escape sequence \C can be used to match a single code unit in a UTF + The escape sequence \C can be used to match a single code unit in UTF mode, but its use can lead to some strange effects because it breaks up multi-unit characters (see the description of \C in the pcre2pattern documentation). For this reason, there is a build-time option that dis- @@ -10810,8 +10842,8 @@ WIDE CHARACTERS AND UTF MODES modes provokes a match-time error. Also, the JIT optimization does not support \C in these modes. If JIT optimization is requested for a UTF-8 or UTF-16 pattern that contains \C, it will not succeed, and so when - pcre2_match() is called, the matching will be carried out by the normal - interpretive function. + pcre2_match() is called, the matching will be carried out by the inter- + pretive function. 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 @@ -10835,14 +10867,14 @@ WIDE CHARACTERS AND UTF MODES acters, whether or not PCRE2_UCP is set. -CASE-EQUIVALENCE IN UTF MODES +CASE-EQUIVALENCE IN UTF MODE - Case-insensitive matching in a UTF mode makes use of Unicode properties + Case-insensitive matching in UTF mode makes use of Unicode properties except for characters whose code points are less than 128 and that have at most two case-equivalent values. For these, a direct table lookup is used for speed. A few Unicode characters such as Greek sigma have more - than two code points that are case-equivalent, and these are treated as - such. + than two code points that are case-equivalent, and these are treated + specially. SCRIPT RUNS @@ -10951,8 +10983,8 @@ VALIDITY OF UTF STRINGS When the PCRE2_UTF option is set, the strings passed as patterns and subjects are (by default) checked for validity on entry to the relevant - functions. If an invalid UTF string is passed, an negative error code - is returned. The code unit offset to the offending character can be + functions. If an invalid UTF string is passed, a negative error code is + returned. The code unit offset to the offending character can be extracted from the match data block by calling pcre2_get_startchar(), which is used for this purpose after a UTF error. @@ -10964,50 +10996,51 @@ VALIDITY OF UTF STRINGS it is given (respectively) contains only valid UTF code unit sequences. If you pass an invalid UTF string when PCRE2_NO_UTF_CHECK is set, the - result is usually undefined and your program may crash or loop indefi- - nitely. There is, however, one mode of matching that can handle invalid - UTF subject strings. This is matching via the JIT optimization using - the PCRE2_JIT_INVALID_UTF option when calling pcre2_jit_compile(). For - details, see the pcre2jit documentation. - - Passing PCRE2_NO_UTF_CHECK to pcre2_compile() just disables the check - for the pattern; it does not also apply to subject strings. If you want - to disable the check for a subject string you must pass this same - option to pcre2_match() or pcre2_dfa_match(). + result is undefined and your program may crash or loop indefinitely or + give incorrect results. There is, however, one mode of matching that + can handle invalid UTF subject strings. This is enabled by passing + PCRE2_MATCH_INVALID_UTF to pcre2_compile() and is discussed below in + the next section. The rest of this section covers the case when + PCRE2_MATCH_INVALID_UTF is not set. + + Passing PCRE2_NO_UTF_CHECK to pcre2_compile() just disables the UTF + check for the pattern; it does not also apply to subject strings. If + you want to disable the check for a subject string you must pass this + same option to pcre2_match() or pcre2_dfa_match(). 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 + knows as a byte-order mark (BOM). The PCRE2 functions do not handle this, expecting strings to be in host byte order. - Unless PCRE2_NO_UTF_CHECK is set, a UTF string is checked before any + Unless PCRE2_NO_UTF_CHECK is set, a UTF string is checked before any other processing takes place. In the case of pcre2_match() and - pcre2_dfa_match() calls with a non-zero starting offset, the check is + pcre2_dfa_match() 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 + 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. - In addition to checking the format of the string, there is a check to + 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 + 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. - 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 + 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.) - Setting PCRE2_NO_UTF_CHECK at compile time does not disable the error - that is given if an escape sequence for an invalid Unicode code point - is encountered in the pattern. If you want to allow escape sequences - such as \x{d800} (a surrogate code point) you can set the + Setting PCRE2_NO_UTF_CHECK at compile time does not disable the error + that is given if an escape sequence for an invalid Unicode code point + is encountered in the pattern. If you want to allow escape sequences + such as \x{d800} (a surrogate code point) you can set the PCRE2_EXTRA_ALLOW_SURROGATE_ESCAPES extra option. However, this is pos- sible only in UTF-8 and UTF-32 modes, because these values are not rep- resentable in UTF-16. @@ -11022,10 +11055,10 @@ VALIDITY OF UTF STRINGS PCRE2_ERROR_UTF8_ERR4 PCRE2_ERROR_UTF8_ERR5 - 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 (origi- - nally defined by RFC 2279) allows for up to 6 bytes, and this is + 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 (origi- + nally defined by RFC 2279) allows for up to 6 bytes, and this is checked first; hence the possibility of 4 or 5 missing bytes. PCRE2_ERROR_UTF8_ERR6 @@ -11035,24 +11068,24 @@ VALIDITY OF UTF STRINGS PCRE2_ERROR_UTF8_ERR10 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 + the character do not have the binary value 0b10 (that is, either the most significant bit is 0, or the next bit is 1). PCRE2_ERROR_UTF8_ERR11 PCRE2_ERROR_UTF8_ERR12 - A character that is valid by the RFC 2279 rules is either 5 or 6 bytes + 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. PCRE2_ERROR_UTF8_ERR13 - A 4-byte character has a value greater than 0x10fff; these code points + A 4-byte character has a value greater than 0x10ffff; these code points are excluded by RFC 3629. PCRE2_ERROR_UTF8_ERR14 - 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 + 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. PCRE2_ERROR_UTF8_ERR15 @@ -11061,26 +11094,26 @@ VALIDITY OF UTF STRINGS PCRE2_ERROR_UTF8_ERR18 PCRE2_ERROR_UTF8_ERR19 - 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 cor- + 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 cor- rect coding uses just one byte. PCRE2_ERROR_UTF8_ERR20 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 sec- - ond is 0). Such a byte can only validly occur as the second or subse- + binary value 0b10 (that is, the most significant bit is 1 and the sec- + ond is 0). Such a byte can only validly occur as the second or subse- quent byte of a multi-byte character. PCRE2_ERROR_UTF8_ERR21 - The first byte of a character has the value 0xfe or 0xff. These values + The first byte of a character has the value 0xfe or 0xff. These values can never occur in a valid UTF-8 string. Errors in UTF-16 strings - The following negative error codes are given for invalid UTF-16 + The following negative error codes are given for invalid UTF-16 strings: PCRE2_ERROR_UTF16_ERR1 Missing low surrogate at end of string @@ -11090,13 +11123,61 @@ VALIDITY OF UTF STRINGS Errors in UTF-32 strings - The following negative error codes are given for invalid UTF-32 + The following negative error codes are given for invalid UTF-32 strings: PCRE2_ERROR_UTF32_ERR1 Surrogate character (0xd800 to 0xdfff) PCRE2_ERROR_UTF32_ERR2 Code point is greater than 0x10ffff +MATCHING IN INVALID UTF STRINGS + + You can run pattern matches on subject strings that may contain invalid + UTF sequences if you call pcre2_compile() with the + PCRE2_MATCH_INVALID_UTF option. This is supported by pcre2_match(), + including JIT matching, but not by pcre2_dfa_match(). When + PCRE2_MATCH_INVALID_UTF is set, it forces PCRE2_UTF to be set as well. + Note, however, that the pattern itself must be a valid UTF string. + + Setting PCRE2_MATCH_INVALID_UTF does not affect what pcre2_compile() + generates, but if pcre2_jit_compile() is subsequently called, it does + generate different code. If JIT is not used, the option affects the be- + haviour of the interpretive code in pcre2_match(). When + PCRE2_MATCH_INVALID_UTF is set at compile time, PCRE2_NO_UTF_CHECK is + ignored at match time. + + In this mode, an invalid code unit sequence in the subject never + matches any pattern item. It does not match dot, it does not match + \p{Any}, it does not even match negative items such as [^X]. A lookbe- + hind assertion fails if it encounters an invalid sequence while moving + the current point backwards. In other words, an invalid UTF code unit + sequence acts as a barrier which no match can cross. + + You can also think of this as the subject being split up into fragments + of valid UTF, delimited internally by invalid code unit sequences. The + pattern is matched fragment by fragment. The result of a successful + match, however, is given as code unit offsets in the entire subject + string in the usual way. There are a few points to consider: + + The internal boundaries are not interpreted as the beginnings or ends + of lines and so do not match circumflex or dollar characters in the + pattern. + + If pcre2_match() is called with an offset that points to an invalid + UTF-sequence, that sequence is skipped, and the match starts at the + next valid UTF character, or the end of the subject. + + At internal fragment boundaries, \b and \B behave in the same way as at + the beginning and end of the subject. For example, a sequence such as + \bWORD\b would match an instance of WORD that is surrounded by invalid + UTF code units. + + Using PCRE2_MATCH_INVALID_UTF, an application can run matches on arbi- + trary data, knowing that any matched strings that are returned are + valid UTF. This can be useful when searching for UTF text in executable + or other binary files. + + AUTHOR Philip Hazel @@ -11106,8 +11187,8 @@ AUTHOR REVISION - Last updated: 06 March 2019 + Last updated: 24 May 2019 Copyright (c) 1997-2019 University of Cambridge. ------------------------------------------------------------------------------ - - + + diff --git a/doc/pcre2_compile.3 b/doc/pcre2_compile.3 index b23bf46..e97bf11 100644 --- a/doc/pcre2_compile.3 +++ b/doc/pcre2_compile.3 @@ -1,4 +1,4 @@ -.TH PCRE2_COMPILE 3 "11 February 2019" "PCRE2 10.33" +.TH PCRE2_COMPILE 3 "23 May 2019" "PCRE2 10.34" .SH NAME PCRE2 - Perl-compatible regular expressions (revised API) .SH SYNOPSIS @@ -53,6 +53,7 @@ The option bits are: PCRE2_EXTENDED Ignore white space and # comments PCRE2_FIRSTLINE Force matching to be before newline PCRE2_LITERAL Pattern characters are all literal + PCRE2_MATCH_INVALID_UTF Enable support for matching invalid UTF PCRE2_MATCH_UNSET_BACKREF Match unset backreferences PCRE2_MULTILINE ^ and $ match newlines within data PCRE2_NEVER_BACKSLASH_C Lock out the use of \eC in patterns diff --git a/doc/pcre2_jit_compile.3 b/doc/pcre2_jit_compile.3 index 23dd2d2..4c91043 100644 --- a/doc/pcre2_jit_compile.3 +++ b/doc/pcre2_jit_compile.3 @@ -1,4 +1,4 @@ -.TH PCRE2_JIT_COMPILE 3 "06 March 2019" "PCRE2 10.33" +.TH PCRE2_JIT_COMPILE 3 "23 May 2019" "PCRE2 10.34" .SH NAME PCRE2 - Perl-compatible regular expressions (revised API) .SH SYNOPSIS @@ -29,8 +29,11 @@ bits: PCRE2_JIT_COMPLETE compile code for full matching PCRE2_JIT_PARTIAL_SOFT compile code for soft partial matching PCRE2_JIT_PARTIAL_HARD compile code for hard partial matching - PCRE2_JIT_INVALID_UTF compile code to handle invalid UTF .sp +There is also an obsolete option called PCRE2_JIT_INVALID_UTF, which has been +superseded by the \fBpcre2_compile()\fP option PCRE2_MATCH_INVALID_UTF. The old +option is deprecated and may be removed in future. +.P The yield of the function is 0 for success, or a negative error code otherwise. In particular, PCRE2_ERROR_JIT_BADOPTION is returned if JIT is not supported or if an unknown bit is set in \fIoptions\fP. diff --git a/doc/pcre2api.3 b/doc/pcre2api.3 index d219466..22c57e1 100644 --- a/doc/pcre2api.3 +++ b/doc/pcre2api.3 @@ -1,4 +1,4 @@ -.TH PCRE2API 3 "14 February 2019" "PCRE2 10.33" +.TH PCRE2API 3 "23 May 2019" "PCRE2 10.34" .SH NAME PCRE2 - Perl-compatible regular expressions (revised API) .sp @@ -1285,13 +1285,14 @@ and \fBpcre2_compile()\fP returns a non-NULL value. .P There are nearly 100 positive error codes that \fBpcre2_compile()\fP may return if it finds an error in the pattern. There are also some negative error codes -that are used for invalid UTF strings. These are the same as given by -\fBpcre2_match()\fP and \fBpcre2_dfa_match()\fP, and are described in the +that are used for invalid UTF strings when validity checking is in force. These +are the same as given by \fBpcre2_match()\fP and \fBpcre2_dfa_match()\fP, and +are described in the .\" HREF \fBpcre2unicode\fP .\" -page. There is no separate documentation for the positive error codes, because -the textual error messages that are obtained by calling the +documentation. There is no separate documentation for the positive error codes, +because the textual error messages that are obtained by calling the \fBpcre2_get_error_message()\fP function (see "Obtaining a textual error message" .\" HTML <a href="#geterrormessage"> @@ -1557,10 +1558,20 @@ expression engine is not the most efficient way of doing it. If you are doing a lot of literal matching and are worried about efficiency, you should consider using other approaches. The only other main options that are allowed with PCRE2_LITERAL are: PCRE2_ANCHORED, PCRE2_ENDANCHORED, PCRE2_AUTO_CALLOUT, -PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, -PCRE2_UTF, and PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE -and PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an -error. +PCRE2_CASELESS, PCRE2_FIRSTLINE, PCRE2_MATCH_INVALID_UTF, +PCRE2_NO_START_OPTIMIZE, PCRE2_NO_UTF_CHECK, PCRE2_UTF, and +PCRE2_USE_OFFSET_LIMIT. The extra options PCRE2_EXTRA_MATCH_LINE and +PCRE2_EXTRA_MATCH_WORD are also supported. Any other options cause an error. +.sp + PCRE2_MATCH_INVALID_UTF +.sp +This option forces PCRE2_UTF (see below) and also enables support for matching +by \fBpcre2_match()\fP in subject strings that contain invalid UTF sequences. +This facility is not supported for DFA matching. For details, see the +.\" HREF +\fBpcre2unicode\fP +.\" +documentation. .sp PCRE2_MATCH_UNSET_BACKREF .sp @@ -2635,15 +2646,23 @@ of JIT; it forces matching to be done by the interpreter. PCRE2_NO_UTF_CHECK .sp When PCRE2_UTF is set at compile time, the validity of the subject as a UTF -string is checked by default when \fBpcre2_match()\fP is subsequently called. -If a non-zero starting offset is given, 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 \eb and \eB are one-character lookbehinds. +string is checked unless PCRE2_NO_UTF_CHECK is passed to \fBpcre2_match()\fP or +PCRE2_MATCH_INVALID_UTF was passed to \fBpcre2_compile()\fP. The latter special +case is discussed in detail in the +.\" HREF +\fBpcre2unicode\fP +.\" +documentation. +.P +In the default case, if a non-zero starting offset is given, 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 \eb and \eB are +one-character lookbehinds. .P The check is carried out before any other processing takes place, and a negative error code is returned if the check fails. There are several UTF error @@ -2666,17 +2685,18 @@ in the .\" HREF \fBpcre2unicode\fP .\" -page. +documentation. .P -If you know that your subject is valid, and you want to skip these checks for +If you know that your subject is valid, and you want to skip this check for performance reasons, you can set the PCRE2_NO_UTF_CHECK option when calling \fBpcre2_match()\fP. You might want to do this for the second and subsequent -calls to \fBpcre2_match()\fP if you are making repeated calls to find other +calls to \fBpcre2_match()\fP if you are making repeated calls to find multiple matches in the same subject string. .P -\fBWarning:\fP When PCRE2_NO_UTF_CHECK is set, the effect of passing an invalid +\fBWarning:\fP Unless PCRE2_MATCH_INVALID_UTF was set at compile time, when +PCRE2_NO_UTF_CHECK is set at match time the effect of passing an invalid string as a subject, or an invalid value of \fIstartoffset\fP, is undefined. -Your program may crash or loop indefinitely. +Your program may crash or loop indefinitely or give wrong results. .sp PCRE2_PARTIAL_HARD PCRE2_PARTIAL_SOFT @@ -3775,6 +3795,12 @@ This return is given if \fBpcre2_dfa_match()\fP encounters a condition item that uses a backreference for the condition, or a test for recursion in a specific capture group. These are not supported. .sp + PCRE2_ERROR_DFA_UINVALID_UTF +.sp +This return is given if \fBpcre2_dfa_match()\fP is called for a pattern that +was compiled with PCRE2_MATCH_INVALID_UTF. This is not supported for DFA +matching. +.sp PCRE2_ERROR_DFA_WSSIZE .sp This return is given if \fBpcre2_dfa_match()\fP runs out of space in the @@ -3817,6 +3843,6 @@ Cambridge, England. .rs .sp .nf -Last updated: 14 February 2019 +Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. .fi diff --git a/doc/pcre2jit.3 b/doc/pcre2jit.3 index b7ae2eb..f4be3fb 100644 --- a/doc/pcre2jit.3 +++ b/doc/pcre2jit.3 @@ -1,4 +1,4 @@ -.TH PCRE2JIT 3 "06 March 2019" "PCRE2 10.33" +.TH PCRE2JIT 3 "23 May 2019" "PCRE2 10.34" .SH NAME PCRE2 - Perl-compatible regular expressions (revised API) .SH "PCRE2 JUST-IN-TIME COMPILER SUPPORT" @@ -123,23 +123,29 @@ pattern. .SH "MATCHING SUBJECTS CONTAINING INVALID UTF" .rs .sp -When a pattern is compiled with the PCRE2_UTF option, the interpretive matching -function expects its subject string to be a valid sequence of UTF code units. -If it is not, the result is undefined. This is also true by default of matching -via JIT. However, if the option PCRE2_JIT_INVALID_UTF is passed to -\fBpcre2_jit_compile()\fP, code that can process a subject containing invalid -UTF is compiled. +When a pattern is compiled with the PCRE2_UTF option, subject strings are +normally expected to be a valid sequence of UTF code units. By default, this is +checked at the start of matching and an error is generated if invalid UTF is +detected. The PCRE2_NO_UTF_CHECK option can be passed to \fBpcre2_match()\fP to +skip the check (for improved performance) if you are sure that a subject string +is valid. If this option is used with an invalid string, the result is +undefined. .P -In this mode, an invalid code unit sequence never matches any pattern item. It -does not match dot, it does not match \ep{Any}, it does not even match negative -items such as [^X]. A lookbehind assertion fails if it encounters an invalid -sequence while moving the current point backwards. In other words, an invalid -UTF code unit sequence acts as a barrier which no match can cross. Reaching an -invalid sequence causes an immediate backtrack. +However, a way of running matches on strings that may contain invalid UTF +sequences is available. Calling \fBpcre2_compile()\fP with the +PCRE2_MATCH_INVALID_UTF option has two effects: it tells the interpreter in +\fBpcre2_match()\fP to support invalid UTF, and, if \fBpcre2_jit_compile()\fP +is called, the compiled JIT code also supports invalid UTF. Details of how this +support works, in both the JIT and the interpretive cases, is given in the +.\" HREF +\fBpcre2unicode\fP +.\" +documentation. .P -Using this option, an application can run matches in arbitrary data, knowing -that any matched strings that are returned will be valid UTF. This can be -useful when searching for text in executable or other binary files. +There is also an obsolete option for \fBpcre2_jit_compile()\fP called +PCRE2_JIT_INVALID_UTF, which currently exists only for backward compatibility. +It is superseded by the \fBpcre2_compile()\fP option PCRE2_MATCH_INVALID_UTF +and should no longer be used. It may be removed in future. . . .SH "UNSUPPORTED OPTIONS AND PATTERN ITEMS" @@ -438,6 +444,6 @@ Cambridge, England. .rs .sp .nf -Last updated: 06 March 2019 +Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. .fi diff --git a/doc/pcre2matching.3 b/doc/pcre2matching.3 index 20ffac5..76a08e8 100644 --- a/doc/pcre2matching.3 +++ b/doc/pcre2matching.3 @@ -1,4 +1,4 @@ -.TH PCRE2MATCHING 3 "10 October 2018" "PCRE2 10.33" +.TH PCRE2MATCHING 3 "23 May 2019" "PCRE2 10.34" .SH NAME PCRE2 - Perl-compatible regular expressions (revised API) .SH "PCRE2 MATCHING ALGORITHMS" @@ -157,6 +157,9 @@ code unit) at a time, for all active paths through the tree. .P 9. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) are not supported. (*FAIL) is supported, and behaves like a failing negative assertion. +.P +10. The PCRE2_MATCH_INVALID_UTF option for \fBpcre2_compile()\fP is not +supported by \fBpcre2_dfa_match()\fP. . . .SH "ADVANTAGES OF THE ALTERNATIVE ALGORITHM" @@ -191,7 +194,8 @@ The alternative algorithm suffers from a number of disadvantages: because it has to search for all possible matches, but is also because it is less susceptible to optimization. .P -2. Capturing parentheses, backreferences, and script runs are not supported. +2. Capturing parentheses, backreferences, script runs, and matching within +invalid UTF string are not supported. .P 3. Although atomic groups are supported, their use does not provide the performance advantage that it does for the standard algorithm. @@ -211,6 +215,6 @@ Cambridge, England. .rs .sp .nf -Last updated: 10 October 2018 -Copyright (c) 1997-2018 University of Cambridge. +Last updated: 23 May 2019 +Copyright (c) 1997-2019 University of Cambridge. .fi diff --git a/doc/pcre2pattern.3 b/doc/pcre2pattern.3 index de8d7ce..a2a0ecc 100644 --- a/doc/pcre2pattern.3 +++ b/doc/pcre2pattern.3 @@ -1,4 +1,4 @@ -.TH PCRE2PATTERN 3 "12 February 2019" "PCRE2 10.33" +.TH PCRE2PATTERN 3 "23 May 2019" "PCRE2 10.34" .SH NAME PCRE2 - Perl-compatible regular expressions (revised API) .SH "PCRE2 REGULAR EXPRESSION DETAILS" @@ -52,10 +52,11 @@ single code units, or as multiple UTF-8 or UTF-16 code units. UTF-32 can be specified for the 32-bit library, in which case it constrains the character values to valid Unicode code points. To process UTF strings, PCRE2 must be built to include Unicode support (which is the default). When using UTF strings -you must either call the compiling function with the PCRE2_UTF option, or the -pattern must start with the special sequence (*UTF), which is equivalent to -setting the relevant option. How setting a UTF mode affects pattern matching is -mentioned in several places below. There is also a summary of features in the +you must either call the compiling function with one or both of the PCRE2_UTF +or PCRE2_MATCH_INVALID_UTF options, or the pattern must start with the special +sequence (*UTF), which is equivalent to setting the relevant PCRE2_UTF. How +setting a UTF mode affects pattern matching is mentioned in several places +below. There is also a summary of features in the .\" HREF \fBpcre2unicode\fP .\" @@ -398,11 +399,11 @@ PCRE2_EXTRA_ALT_BSUX has the same effect as PCRE2_ALT_BSUX and, in addition, There may be any number of hexadecimal digits. This syntax is from ECMAScript 6. .P -The \eN{U+hhh..} escape sequence is recognized only when the PCRE2_UTF option -is set, that is, when PCRE2 is operating in a Unicode mode. Perl also uses -\eN{name} to specify characters by Unicode name; PCRE2 does not support this. -Note that when \eN is not followed by an opening brace (curly bracket) it has -an entirely different meaning, matching any character that is not a newline. +The \eN{U+hhh..} escape sequence is recognized only when PCRE2 is operating in +UTF mode. Perl also uses \eN{name} to specify characters by Unicode name; PCRE2 +does not support this. Note that when \eN is not followed by an opening brace +(curly bracket) it has an entirely different meaning, matching any character +that is not a newline. .P There are some legacy applications where the escape sequence \er is expected to match a newline. If the PCRE2_EXTRA_ESCAPED_CR_IS_LF option is set, \er in a @@ -1352,7 +1353,7 @@ with \eC in UTF-8 or UTF-16 mode means that the rest of the string may start with a malformed UTF character. This has undefined results, because PCRE2 assumes that it is matching character by character in a valid UTF string (by default it checks the subject string's validity at the start of processing -unless the PCRE2_NO_UTF_CHECK option is used). +unless the PCRE2_NO_UTF_CHECK or PCRE2_MATCH_INVALID_UTF option is used). .P An application can lock out the use of \eC by setting the PCRE2_NEVER_BACKSLASH_C option when compiling a pattern. It is also possible to @@ -3763,6 +3764,6 @@ Cambridge, England. .rs .sp .nf -Last updated: 12 February 2019 +Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. .fi diff --git a/doc/pcre2test.1 b/doc/pcre2test.1 index 568e705..eab478d 100644 --- a/doc/pcre2test.1 +++ b/doc/pcre2test.1 @@ -1,4 +1,4 @@ -.TH PCRE2TEST 1 "11 March 2019" "PCRE 10.33" +.TH PCRE2TEST 1 "23 May 2019" "PCRE 10.34" .SH NAME pcre2test - a program for testing Perl-compatible regular expressions. .SH SYNOPSIS @@ -572,6 +572,7 @@ for a description of the effects of these options. firstline set PCRE2_FIRSTLINE literal set PCRE2_LITERAL match_line set PCRE2_EXTRA_MATCH_LINE + match_invalid_utf set PCRE2_MATCH_INVALID_UTF match_unset_backref set PCRE2_MATCH_UNSET_BACKREF match_word set PCRE2_EXTRA_MATCH_WORD /m multiline set PCRE2_MULTILINE @@ -2059,6 +2060,6 @@ Cambridge, England. .rs .sp .nf -Last updated: 11 March 2019 +Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. .fi diff --git a/doc/pcre2test.txt b/doc/pcre2test.txt index cbe3528..6442270 100644 --- a/doc/pcre2test.txt +++ b/doc/pcre2test.txt @@ -551,6 +551,7 @@ PATTERN MODIFIERS firstline set PCRE2_FIRSTLINE literal set PCRE2_LITERAL match_line set PCRE2_EXTRA_MATCH_LINE + match_invalid_utf set PCRE2_MATCH_INVALID_UTF match_unset_backref set PCRE2_MATCH_UNSET_BACKREF match_word set PCRE2_EXTRA_MATCH_WORD /m multiline set PCRE2_MULTILINE @@ -1890,5 +1891,5 @@ AUTHOR REVISION - Last updated: 11 March 2019 + Last updated: 23 May 2019 Copyright (c) 1997-2019 University of Cambridge. diff --git a/doc/pcre2unicode.3 b/doc/pcre2unicode.3 index e444422..d77ebc7 100644 --- a/doc/pcre2unicode.3 +++ b/doc/pcre2unicode.3 @@ -1,26 +1,38 @@ -.TH PCRE2UNICODE 3 "11 May 2019" "PCRE2 10.33" +.TH PCRE2UNICODE 3 "24 May 2019" "PCRE2 10.34" .SH NAME PCRE - Perl-compatible regular expressions (revised API) .SH "UNICODE AND UTF SUPPORT" .rs .sp -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 +PCRE2 is normally built with Unicode support, though if you do not need it, you +can build it without, in which case the library will be smaller. With Unicode +support, PCRE2 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), but this is not the default. Unless specifically requested, PCRE2 +treats each code unit in a string as one character. +.P +There are two ways of telling PCRE2 to switch to UTF mode, where characters may +consist of more than one code unit and the range of values is constrained. The +program can call .\" HREF \fBpcre2_compile()\fP .\" -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. There are also some other -changes to the way characters are handled, as documented below. -.P -If you do not need Unicode support you can build PCRE2 without it, in which -case the library will be smaller. +with the PCRE2_UTF option, or the pattern may start with the sequence (*UTF). +However, the latter facility can be locked out by the PCRE2_NEVER_UTF option. +That is, the programmer can prevent the supplier of the pattern from switching +to UTF mode. +.P +Note that the PCRE2_MATCH_INVALID_UTF option (see +.\" HTML <a href="#matchinvalid"> +.\" </a> +below) +.\" +forces PCRE2_UTF to be set. +.P +In UTF mode, 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. There are also some other changes to the way characters are +handled, as documented below. . . .SH "UNICODE PROPERTY SUPPORT" @@ -55,18 +67,18 @@ also recognized; larger ones can be coded using \eo{...}. .P The escape sequence \eN{U+<hex digits>} is recognized as another way of specifying a Unicode character by code point in a UTF mode. It is not allowed -in non-UTF modes. +in non-UTF mode. .P -In UTF modes, repeat quantifiers apply to complete UTF characters, not to +In UTF mode, repeat quantifiers apply to complete UTF characters, not to individual code units. .P -In UTF modes, the dot metacharacter matches one UTF character instead of a +In UTF mode, the dot metacharacter matches one UTF character instead of a single code unit. .P -In UTF modes, capture group names are not restricted to ASCII, and may contain +In UTF mode, capture group names are not restricted to ASCII, and may contain any Unicode letters and decimal digits, as well as underscore. .P -The escape sequence \eC can be used to match a single code unit in a UTF mode, +The escape sequence \eC can be used to match a single code unit in UTF mode, but its use can lead to some strange effects because it breaks up multi-unit characters (see the description of \eC in the .\" HREF @@ -82,7 +94,7 @@ may consist of more than one code unit. The use of \eC in these modes provokes a match-time error. Also, the JIT optimization does not support \eC in these modes. If JIT optimization is requested for a UTF-8 or UTF-16 pattern that contains \eC, it will not succeed, and so when \fBpcre2_match()\fP is called, -the matching will be carried out by the normal interpretive function. +the matching will be carried out by the interpretive function. .P The character escapes \eb, \eB, \ed, \eD, \es, \eS, \ew, and \eW correctly test characters of any code value, but, by default, the characters that PCRE2 @@ -114,14 +126,14 @@ However, the special horizontal and vertical white space matching escapes (\eh, not PCRE2_UCP is set. . . -.SH "CASE-EQUIVALENCE IN UTF MODES" +.SH "CASE-EQUIVALENCE IN UTF MODE" .rs .sp -Case-insensitive matching in a UTF mode makes use of Unicode properties except +Case-insensitive matching in UTF mode makes use of Unicode properties except for characters whose code points are less than 128 and that have at most two case-equivalent values. For these, a direct table lookup is used for speed. A few Unicode characters such as Greek sigma have more than two code points that -are case-equivalent, and these are treated as such. +are case-equivalent, and these are treated specially. . . .\" HTML <a name="scriptruns"></a> @@ -231,7 +243,7 @@ adjacent characters. .sp When the PCRE2_UTF option is set, the strings passed as patterns and subjects are (by default) checked for validity on entry to the relevant functions. If an -invalid UTF string is passed, an negative error code is returned. The code unit +invalid UTF string is passed, a negative error code is returned. The code unit offset to the offending character can be extracted from the match data block by calling \fBpcre2_get_startchar()\fP, which is used for this purpose after a UTF error. @@ -244,18 +256,15 @@ PCRE2 assumes that the pattern or subject it is given (respectively) contains only valid UTF code unit sequences. .P If you pass an invalid UTF string when PCRE2_NO_UTF_CHECK is set, the result -is usually undefined and your program may crash or loop indefinitely. There is, -however, one mode of matching that can handle invalid UTF subject strings. This -is matching via the JIT optimization using the PCRE2_JIT_INVALID_UTF option -when calling \fBpcre2_jit_compile()\fP. For details, see the -.\" HREF -\fBpcre2jit\fP -.\" -documentation. +is undefined and your program may crash or loop indefinitely or give incorrect +results. There is, however, one mode of matching that can handle invalid UTF +subject strings. This is enabled by passing PCRE2_MATCH_INVALID_UTF to +\fBpcre2_compile()\fP and is discussed below in the next section. The rest of +this section covers the case when PCRE2_MATCH_INVALID_UTF is not set. .P -Passing PCRE2_NO_UTF_CHECK to \fBpcre2_compile()\fP just disables the check for -the pattern; it does not also apply to subject strings. If you want to disable -the check for a subject string you must pass this same option to +Passing PCRE2_NO_UTF_CHECK to \fBpcre2_compile()\fP just disables the UTF check +for the pattern; it does not also apply to subject strings. If you want to +disable the check for a subject string you must pass this same option to \fBpcre2_match()\fP or \fBpcre2_dfa_match()\fP. .P UTF-16 and UTF-32 strings can indicate their endianness by special code knows @@ -386,6 +395,52 @@ The following negative error codes are given for invalid UTF-32 strings: .sp . . +.\" HTML <a name="matchinvalid"></a> +.SH "MATCHING IN INVALID UTF STRINGS" +.rs +.sp +You can run pattern matches on subject strings that may contain invalid UTF +sequences if you call \fBpcre2_compile()\fP with the PCRE2_MATCH_INVALID_UTF +option. This is supported by \fBpcre2_match()\fP, including JIT matching, but +not by \fBpcre2_dfa_match()\fP. When PCRE2_MATCH_INVALID_UTF is set, it forces +PCRE2_UTF to be set as well. Note, however, that the pattern itself must be a +valid UTF string. +.P +Setting PCRE2_MATCH_INVALID_UTF does not affect what \fBpcre2_compile()\fP +generates, but if \fBpcre2_jit_compile()\fP is subsequently called, it does +generate different code. If JIT is not used, the option affects the behaviour +of the interpretive code in \fBpcre2_match()\fP. When PCRE2_MATCH_INVALID_UTF +is set at compile time, PCRE2_NO_UTF_CHECK is ignored at match time. +.P +In this mode, an invalid code unit sequence in the subject never matches any +pattern item. It does not match dot, it does not match \ep{Any}, it does not +even match negative items such as [^X]. A lookbehind assertion fails if it +encounters an invalid sequence while moving the current point backwards. In +other words, an invalid UTF code unit sequence acts as a barrier which no match +can cross. +.P +You can also think of this as the subject being split up into fragments of +valid UTF, delimited internally by invalid code unit sequences. The pattern is +matched fragment by fragment. The result of a successful match, however, is +given as code unit offsets in the entire subject string in the usual way. There +are a few points to consider: +.P +The internal boundaries are not interpreted as the beginnings or ends of lines +and so do not match circumflex or dollar characters in the pattern. +.P +If \fBpcre2_match()\fP is called with an offset that points to an invalid +UTF-sequence, that sequence is skipped, and the match starts at the next valid +UTF character, or the end of the subject. +.P +At internal fragment boundaries, \eb and \eB behave in the same way as at the +beginning and end of the subject. For example, a sequence such as \ebWORD\eb +would match an instance of WORD that is surrounded by invalid UTF code units. +.P +Using PCRE2_MATCH_INVALID_UTF, an application can run matches on arbitrary +data, knowing that any matched strings that are returned are valid UTF. This +can be useful when searching for UTF text in executable or other binary files. +. +. .SH AUTHOR .rs .sp @@ -400,6 +455,6 @@ Cambridge, England. .rs .sp .nf -Last updated: 11 May 2019 +Last updated: 24 May 2019 Copyright (c) 1997-2019 University of Cambridge. .fi |