From 0a55fa14f462169bbd8a8de623804f039854f95f Mon Sep 17 00:00:00 2001 From: dartraiden Date: Fri, 1 Jun 2018 18:25:57 +0300 Subject: we only needs license, contributors and version info --- libs/Pcre16/docs/doc/html/pcreapi.html | 2921 -------------------------------- 1 file changed, 2921 deletions(-) delete mode 100644 libs/Pcre16/docs/doc/html/pcreapi.html (limited to 'libs/Pcre16/docs/doc/html/pcreapi.html') diff --git a/libs/Pcre16/docs/doc/html/pcreapi.html b/libs/Pcre16/docs/doc/html/pcreapi.html deleted file mode 100644 index 2d7adf185a..0000000000 --- a/libs/Pcre16/docs/doc/html/pcreapi.html +++ /dev/null @@ -1,2921 +0,0 @@ - - -pcreapi specification - - -

pcreapi man page

-

-Return to the PCRE index page. -

-

-This page is part of the PCRE HTML documentation. It was generated automatically -from the original man page. If there is any nonsense in it, please consult the -man page, in case the conversion went wrong. -
-

-

-#include <pcre.h> -

-
PCRE NATIVE API BASIC FUNCTIONS
-

-pcre *pcre_compile(const char *pattern, int options, - const char **errptr, int *erroffset, - const unsigned char *tableptr); -
-
-pcre *pcre_compile2(const char *pattern, int options, - int *errorcodeptr, - const char **errptr, int *erroffset, - const unsigned char *tableptr); -
-
-pcre_extra *pcre_study(const pcre *code, int options, - const char **errptr); -
-
-void pcre_free_study(pcre_extra *extra); -
-
-int pcre_exec(const pcre *code, const pcre_extra *extra, - const char *subject, int length, int startoffset, - int options, int *ovector, int ovecsize); -
-
-int pcre_dfa_exec(const pcre *code, const pcre_extra *extra, - const char *subject, int length, int startoffset, - int options, int *ovector, int ovecsize, - int *workspace, int wscount); -

-
PCRE NATIVE API STRING EXTRACTION FUNCTIONS
-

-int pcre_copy_named_substring(const pcre *code, - const char *subject, int *ovector, - int stringcount, const char *stringname, - char *buffer, int buffersize); -
-
-int pcre_copy_substring(const char *subject, int *ovector, - int stringcount, int stringnumber, char *buffer, - int buffersize); -
-
-int pcre_get_named_substring(const pcre *code, - const char *subject, int *ovector, - int stringcount, const char *stringname, - const char **stringptr); -
-
-int pcre_get_stringnumber(const pcre *code, - const char *name); -
-
-int pcre_get_stringtable_entries(const pcre *code, - const char *name, char **first, char **last); -
-
-int pcre_get_substring(const char *subject, int *ovector, - int stringcount, int stringnumber, - const char **stringptr); -
-
-int pcre_get_substring_list(const char *subject, - int *ovector, int stringcount, const char ***listptr); -
-
-void pcre_free_substring(const char *stringptr); -
-
-void pcre_free_substring_list(const char **stringptr); -

-
PCRE NATIVE API AUXILIARY FUNCTIONS
-

-int pcre_jit_exec(const pcre *code, const pcre_extra *extra, - const char *subject, int length, int startoffset, - int options, int *ovector, int ovecsize, - pcre_jit_stack *jstack); -
-
-pcre_jit_stack *pcre_jit_stack_alloc(int startsize, int maxsize); -
-
-void pcre_jit_stack_free(pcre_jit_stack *stack); -
-
-void pcre_assign_jit_stack(pcre_extra *extra, - pcre_jit_callback callback, void *data); -
-
-const unsigned char *pcre_maketables(void); -
-
-int pcre_fullinfo(const pcre *code, const pcre_extra *extra, - int what, void *where); -
-
-int pcre_refcount(pcre *code, int adjust); -
-
-int pcre_config(int what, void *where); -
-
-const char *pcre_version(void); -
-
-int pcre_pattern_to_host_byte_order(pcre *code, - pcre_extra *extra, const unsigned char *tables); -

-
PCRE NATIVE API INDIRECTED FUNCTIONS
-

-void *(*pcre_malloc)(size_t); -
-
-void (*pcre_free)(void *); -
-
-void *(*pcre_stack_malloc)(size_t); -
-
-void (*pcre_stack_free)(void *); -
-
-int (*pcre_callout)(pcre_callout_block *); -
-
-int (*pcre_stack_guard)(void); -

-
PCRE 8-BIT, 16-BIT, AND 32-BIT LIBRARIES
-

-As well as support for 8-bit character strings, PCRE also supports 16-bit -strings (from release 8.30) and 32-bit strings (from release 8.32), by means of -two additional libraries. They can be built as well as, or instead of, the -8-bit library. To avoid too much complication, this document describes the -8-bit versions of the functions, with only occasional references to the 16-bit -and 32-bit libraries. -

-

-The 16-bit and 32-bit functions operate in the same way as their 8-bit -counterparts; they just use different data types for their arguments and -results, and their names start with pcre16_ or pcre32_ instead of -pcre_. For every option that has UTF8 in its name (for example, -PCRE_UTF8), there are corresponding 16-bit and 32-bit names with UTF8 replaced -by UTF16 or UTF32, respectively. This facility is in fact just cosmetic; the -16-bit and 32-bit option names define the same bit values. -

-

-References to bytes and UTF-8 in this document should be read as references to -16-bit data units and UTF-16 when using the 16-bit library, or 32-bit data -units and UTF-32 when using the 32-bit library, unless specified otherwise. -More details of the specific differences for the 16-bit and 32-bit libraries -are given in the -pcre16 -and -pcre32 -pages. -

-
PCRE API OVERVIEW
-

-PCRE has its own native API, which is described in this document. There are -also some wrapper functions (for the 8-bit library only) that correspond to the -POSIX regular expression API, but they do not give access to all the -functionality. They are described in the -pcreposix -documentation. Both of these APIs define a set of C function calls. A C++ -wrapper (again for the 8-bit library only) is also distributed with PCRE. It is -documented in the -pcrecpp -page. -

-

-The native API C function prototypes are defined in the header file -pcre.h, and on Unix-like systems the (8-bit) library itself is called -libpcre. It can normally be accessed by adding -lpcre to the -command for linking an application that uses PCRE. The header file defines the -macros PCRE_MAJOR and PCRE_MINOR to contain the major and minor release numbers -for the library. Applications can use these to include support for different -releases of PCRE. -

-

-In a Windows environment, if you want to statically link an application program -against a non-dll pcre.a file, you must define PCRE_STATIC before -including pcre.h or pcrecpp.h, because otherwise the -pcre_malloc() and pcre_free() exported functions will be declared -__declspec(dllimport), with unwanted results. -

-

-The functions pcre_compile(), pcre_compile2(), pcre_study(), -and pcre_exec() are used for compiling and matching regular expressions -in a Perl-compatible manner. A sample program that demonstrates the simplest -way of using them is provided in the file called pcredemo.c in the PCRE -source distribution. A listing of this program is given in the -pcredemo -documentation, and the -pcresample -documentation describes how to compile and run it. -

-

-Just-in-time compiler support is an optional feature of PCRE that can be built -in appropriate hardware environments. It greatly speeds up the matching -performance of many patterns. Simple programs can easily request that it be -used if available, by setting an option that is ignored when it is not -relevant. More complicated programs might need to make use of the functions -pcre_jit_stack_alloc(), pcre_jit_stack_free(), and -pcre_assign_jit_stack() in order to control the JIT code's memory usage. -

-

-From release 8.32 there is also a direct interface for JIT execution, which -gives improved performance. The JIT-specific functions are discussed in the -pcrejit -documentation. -

-

-A second matching function, pcre_dfa_exec(), which is not -Perl-compatible, is also provided. This uses a different algorithm for the -matching. The alternative algorithm finds all possible matches (at a given -point in the subject), and scans the subject just once (unless there are -lookbehind assertions). However, this algorithm does not return captured -substrings. A description of the two matching algorithms and their advantages -and disadvantages is given in the -pcrematching -documentation. -

-

-In addition to the main compiling and matching functions, there are convenience -functions for extracting captured substrings from a subject string that is -matched by pcre_exec(). They are: -

-  pcre_copy_substring()
-  pcre_copy_named_substring()
-  pcre_get_substring()
-  pcre_get_named_substring()
-  pcre_get_substring_list()
-  pcre_get_stringnumber()
-  pcre_get_stringtable_entries()
-
-pcre_free_substring() and pcre_free_substring_list() are also -provided, to free the memory used for extracted strings. -

-

-The function pcre_maketables() is used to build a set of character tables -in the current locale for passing to pcre_compile(), pcre_exec(), -or pcre_dfa_exec(). This is an optional facility that is provided for -specialist use. Most commonly, no special tables are passed, in which case -internal tables that are generated when PCRE is built are used. -

-

-The function pcre_fullinfo() is used to find out information about a -compiled pattern. The function pcre_version() returns a pointer to a -string containing the version of PCRE and its date of release. -

-

-The function pcre_refcount() maintains a reference count in a data block -containing a compiled pattern. This is provided for the benefit of -object-oriented applications. -

-

-The global variables pcre_malloc and pcre_free initially contain -the entry points of the standard malloc() and free() functions, -respectively. PCRE calls the memory management functions via these variables, -so a calling program can replace them if it wishes to intercept the calls. This -should be done before calling any PCRE functions. -

-

-The global variables pcre_stack_malloc and pcre_stack_free are also -indirections to memory management functions. These special functions are used -only when PCRE is compiled to use the heap for remembering data, instead of -recursive function calls, when running the pcre_exec() function. See the -pcrebuild -documentation for details of how to do this. It is a non-standard way of -building PCRE, for use in environments that have limited stacks. Because of the -greater use of memory management, it runs more slowly. Separate functions are -provided so that special-purpose external code can be used for this case. When -used, these functions always allocate memory blocks of the same size. There is -a discussion about PCRE's stack usage in the -pcrestack -documentation. -

-

-The global variable pcre_callout initially contains NULL. It can be set -by the caller to a "callout" function, which PCRE will then call at specified -points during a matching operation. Details are given in the -pcrecallout -documentation. -

-

-The global variable pcre_stack_guard initially contains NULL. It can be -set by the caller to a function that is called by PCRE whenever it starts -to compile a parenthesized part of a pattern. When parentheses are nested, PCRE -uses recursive function calls, which use up the system stack. This function is -provided so that applications with restricted stacks can force a compilation -error if the stack runs out. The function should return zero if all is well, or -non-zero to force an error. -

-
NEWLINES
-

-PCRE supports five different conventions for indicating line breaks in -strings: a single CR (carriage return) character, a single LF (linefeed) -character, the two-character sequence CRLF, any of the three preceding, or any -Unicode newline sequence. The Unicode newline sequences are the three just -mentioned, plus the single characters VT (vertical tab, U+000B), FF (form feed, -U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS -(paragraph separator, U+2029). -

-

-Each of the first three conventions is used by at least one operating system as -its standard newline sequence. When PCRE is built, a default can be specified. -The default default is LF, which is the Unix standard. When PCRE is run, the -default can be overridden, either when a pattern is compiled, or when it is -matched. -

-

-At compile time, the newline convention can be specified by the options -argument of pcre_compile(), or it can be specified by special text at the -start of the pattern itself; this overrides any other settings. See the -pcrepattern -page for details of the special character sequences. -

-

-In the PCRE documentation the word "newline" is used to mean "the character or -pair of characters that indicate a line break". The choice of newline -convention affects the handling of the dot, circumflex, and dollar -metacharacters, the handling of #-comments in /x mode, and, when CRLF is a -recognized line ending sequence, the match position advancement for a -non-anchored pattern. There is more detail about this in the -section on pcre_exec() options -below. -

-

-The choice of newline convention does not affect the interpretation of -the \n or \r escape sequences, nor does it affect what \R matches, which is -controlled in a similar way, but by separate options. -

-
MULTITHREADING
-

-The PCRE functions can be used in multi-threading applications, with the -proviso that the memory management functions pointed to by pcre_malloc, -pcre_free, pcre_stack_malloc, and pcre_stack_free, and the -callout and stack-checking functions pointed to by pcre_callout and -pcre_stack_guard, are shared by all threads. -

-

-The compiled form of a regular expression is not altered during matching, so -the same compiled pattern can safely be used by several threads at once. -

-

-If the just-in-time optimization feature is being used, it needs separate -memory stack areas for each thread. See the -pcrejit -documentation for more details. -

-
SAVING PRECOMPILED PATTERNS FOR LATER USE
-

-The compiled form of a regular expression can be saved and re-used at a later -time, possibly by a different program, and even on a host other than the one on -which it was compiled. Details are given in the -pcreprecompile -documentation, which includes a description of the -pcre_pattern_to_host_byte_order() function. However, compiling a regular -expression with one version of PCRE for use with a different version is not -guaranteed to work and may cause crashes. -

-
CHECKING BUILD-TIME OPTIONS
-

-int pcre_config(int what, void *where); -

-

-The function pcre_config() makes it possible for a PCRE client to -discover which optional features have been compiled into the PCRE library. The -pcrebuild -documentation has more details about these optional features. -

-

-The first argument for pcre_config() is an integer, specifying which -information is required; the second argument is a pointer to a variable into -which the information is placed. The returned value is zero on success, or the -negative error code PCRE_ERROR_BADOPTION if the value in the first argument is -not recognized. The following information is available: -

-  PCRE_CONFIG_UTF8
-
-The output is an integer that is set to one if UTF-8 support is available; -otherwise it is set to zero. This value should normally be given to the 8-bit -version of this function, pcre_config(). If it is given to the 16-bit -or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. -
-  PCRE_CONFIG_UTF16
-
-The output is an integer that is set to one if UTF-16 support is available; -otherwise it is set to zero. This value should normally be given to the 16-bit -version of this function, pcre16_config(). If it is given to the 8-bit -or 32-bit version of this function, the result is PCRE_ERROR_BADOPTION. -
-  PCRE_CONFIG_UTF32
-
-The output is an integer that is set to one if UTF-32 support is available; -otherwise it is set to zero. This value should normally be given to the 32-bit -version of this function, pcre32_config(). If it is given to the 8-bit -or 16-bit version of this function, the result is PCRE_ERROR_BADOPTION. -
-  PCRE_CONFIG_UNICODE_PROPERTIES
-
-The output is an integer that is set to one if support for Unicode character -properties is available; otherwise it is set to zero. -
-  PCRE_CONFIG_JIT
-
-The output is an integer that is set to one if support for just-in-time -compiling is available; otherwise it is set to zero. -
-  PCRE_CONFIG_JITTARGET
-
-The output is a pointer to a zero-terminated "const char *" string. If JIT -support is available, the string contains the name of the architecture for -which the JIT compiler is configured, for example "x86 32bit (little endian + -unaligned)". If JIT support is not available, the result is NULL. -
-  PCRE_CONFIG_NEWLINE
-
-The output is an integer whose value specifies the default character sequence -that is recognized as meaning "newline". The values that are supported in -ASCII/Unicode environments are: 10 for LF, 13 for CR, 3338 for CRLF, -2 for -ANYCRLF, and -1 for ANY. In EBCDIC environments, CR, ANYCRLF, and ANY yield the -same values. However, the value for LF is normally 21, though some EBCDIC -environments use 37. The corresponding values for CRLF are 3349 and 3365. The -default should normally correspond to the standard sequence for your operating -system. -
-  PCRE_CONFIG_BSR
-
-The output is an integer whose value indicates what character sequences the \R -escape sequence matches by default. A value of 0 means that \R matches any -Unicode line ending sequence; a value of 1 means that \R matches only CR, LF, -or CRLF. The default can be overridden when a pattern is compiled or matched. -
-  PCRE_CONFIG_LINK_SIZE
-
-The output is an integer that contains the number of bytes used for internal -linkage in compiled regular expressions. For the 8-bit library, the value can -be 2, 3, or 4. For the 16-bit library, the value is either 2 or 4 and is still -a number of bytes. For the 32-bit library, the value is either 2 or 4 and is -still a number of bytes. The default value of 2 is sufficient for all but the -most massive patterns, since it allows the compiled pattern to be up to 64K in -size. Larger values allow larger regular expressions to be compiled, at the -expense of slower matching. -
-  PCRE_CONFIG_POSIX_MALLOC_THRESHOLD
-
-The output is an integer that contains the threshold above which the POSIX -interface uses malloc() for output vectors. Further details are given in -the -pcreposix -documentation. -
-  PCRE_CONFIG_PARENS_LIMIT
-
-The output is a long integer that gives the maximum depth of nesting of -parentheses (of any kind) in a pattern. This limit is imposed to cap the amount -of system stack used when a pattern is compiled. It is specified when PCRE is -built; the default is 250. This limit does not take into account the stack that -may already be used by the calling application. For finer control over -compilation stack usage, you can set a pointer to an external checking function -in pcre_stack_guard. -
-  PCRE_CONFIG_MATCH_LIMIT
-
-The output is a long integer that gives the default limit for the number of -internal matching function calls in a pcre_exec() execution. Further -details are given with pcre_exec() below. -
-  PCRE_CONFIG_MATCH_LIMIT_RECURSION
-
-The output is a long integer that gives the default limit for the depth of -recursion when calling the internal matching function in a pcre_exec() -execution. Further details are given with pcre_exec() below. -
-  PCRE_CONFIG_STACKRECURSE
-
-The output is an integer that is set to one if internal recursion when running -pcre_exec() is implemented by recursive function calls that use the stack -to remember their state. This is the usual way that PCRE is compiled. The -output is zero if PCRE was compiled to use blocks of data on the heap instead -of recursive function calls. In this case, pcre_stack_malloc and -pcre_stack_free are called to manage memory blocks on the heap, thus -avoiding the use of the stack. -

-
COMPILING A PATTERN
-

-pcre *pcre_compile(const char *pattern, int options, - const char **errptr, int *erroffset, - const unsigned char *tableptr); -
-
-pcre *pcre_compile2(const char *pattern, int options, - int *errorcodeptr, - const char **errptr, int *erroffset, - const unsigned char *tableptr); -

-

-Either of the functions pcre_compile() or pcre_compile2() can be -called to compile a pattern into an internal form. The only difference between -the two interfaces is that pcre_compile2() has an additional argument, -errorcodeptr, via which a numerical error code can be returned. To avoid -too much repetition, we refer just to pcre_compile() below, but the -information applies equally to pcre_compile2(). -

-

-The pattern is a C string terminated by a binary zero, and is passed in the -pattern argument. A pointer to a single block of memory that is obtained -via pcre_malloc is returned. This contains the compiled code and related -data. The pcre type is defined for the returned block; this is a typedef -for a structure whose contents are not externally defined. It is up to the -caller to free the memory (via pcre_free) when it is no longer required. -

-

-Although the compiled code of a PCRE regex is relocatable, that is, it does not -depend on memory location, the complete pcre data block is not -fully relocatable, because it may contain a copy of the tableptr -argument, which is an address (see below). -

-

-The options argument contains various bit settings that affect the -compilation. It should be zero if no options are required. The available -options are described below. Some of them (in particular, those that are -compatible with Perl, but some others as well) can also be set and unset from -within the pattern (see the detailed description in the -pcrepattern -documentation). For those options that can be different in different parts of -the pattern, the contents of the options argument specifies their -settings at the start of compilation and execution. The PCRE_ANCHORED, -PCRE_BSR_xxx, PCRE_NEWLINE_xxx, PCRE_NO_UTF8_CHECK, and -PCRE_NO_START_OPTIMIZE options can be set at the time of matching as well as at -compile time. -

-

-If errptr is NULL, pcre_compile() returns NULL immediately. -Otherwise, if compilation of a pattern fails, pcre_compile() returns -NULL, and sets the variable pointed to by errptr to point to a textual -error message. This is a static string that is part of the library. You must -not try to free it. Normally, the offset from the start of the pattern to the -data unit that was being processed when the error was discovered is placed in -the variable pointed to by erroffset, which must not be NULL (if it is, -an immediate error is given). However, for an invalid UTF-8 or UTF-16 string, -the offset is that of the first data 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 data units, not characters, even in a UTF mode. It may sometimes -point into the middle of a UTF-8 or UTF-16 character. -

-

-If pcre_compile2() is used instead of pcre_compile(), and the -errorcodeptr argument is not NULL, a non-zero error code number is -returned via this argument in the event of an error. This is in addition to the -textual error message. Error codes and messages are listed below. -

-

-If the final argument, tableptr, is NULL, PCRE uses a default set of -character tables that are built when PCRE is compiled, using the default C -locale. Otherwise, tableptr must be an address that is the result of a -call to pcre_maketables(). This value is stored with the compiled -pattern, and used again by pcre_exec() and pcre_dfa_exec() when the -pattern is matched. For more discussion, see the section on locale support -below. -

-

-This code fragment shows a typical straightforward call to pcre_compile(): -

-  pcre *re;
-  const char *error;
-  int erroffset;
-  re = pcre_compile(
-    "^A.*Z",          /* the pattern */
-    0,                /* default options */
-    &error,           /* for error message */
-    &erroffset,       /* for error offset */
-    NULL);            /* use default character tables */
-
-The following names for option bits are defined in the pcre.h header -file: -
-  PCRE_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 only way to do it in -Perl. -
-  PCRE_AUTO_CALLOUT
-
-If this bit is set, pcre_compile() automatically inserts callout items, -all with number 255, before each pattern item. For discussion of the callout -facility, see the -pcrecallout -documentation. -
-  PCRE_BSR_ANYCRLF
-  PCRE_BSR_UNICODE
-
-These options (which are mutually exclusive) control what the \R escape -sequence matches. The choice is either to match only CR, LF, or CRLF, or to -match any Unicode newline sequence. The default is specified when PCRE is -built. It can be overridden from within the pattern, or by setting an option -when a compiled pattern is matched. -
-  PCRE_CASELESS
-
-If this bit is set, letters in the pattern match both upper and lower case -letters. It is equivalent to Perl's /i option, and it can be changed within a -pattern by a (?i) option setting. In UTF-8 mode, PCRE always understands the -concept of case for characters whose values are less than 128, so caseless -matching is always possible. For characters with higher values, the concept of -case is supported if PCRE is compiled with Unicode property support, but not -otherwise. If you want to use caseless matching for characters 128 and above, -you must ensure that PCRE is compiled with Unicode property support as well as -with UTF-8 support. -
-  PCRE_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 PCRE_DOLLAR_ENDONLY option is ignored if PCRE_MULTILINE is set. -There is no equivalent to this option in Perl, and no way to set it within a -pattern. -
-  PCRE_DOTALL
-
-If this bit is set, a dot metacharacter in the pattern matches a character of -any value, 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 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 negative class such as [^a] always matches newline -characters, independent of the setting of this option. -
-  PCRE_DUPNAMES
-
-If this bit is set, names used to identify capturing subpatterns need not be -unique. This can be helpful for certain types of pattern when it is known that -only one instance of the named subpattern can ever be matched. There are more -details of named subpatterns below; see also the -pcrepattern -documentation. -
-  PCRE_EXTENDED
-
-If this bit is set, most white space characters in the pattern are totally -ignored except when escaped or inside a character class. However, white space -is not allowed within sequences such as (?> that introduce various -parenthesized subpatterns, nor within a numerical quantifier such as {1,3}. -However, ignorable white space is permitted between an item and a following -quantifier and between a quantifier and a following + that indicates -possessiveness. -

-

-White space did not used to include the VT character (code 11), because Perl -did not treat this character as white space. However, Perl changed at release -5.18, so PCRE followed at release 8.34, and VT is now treated as white space. -

-

-PCRE_EXTENDED also causes characters between an unescaped # outside a character -class and the next newline, inclusive, to be ignored. PCRE_EXTENDED is -equivalent to Perl's /x option, and it can be changed within a pattern by a -(?x) option setting. -

-

-Which characters are interpreted as newlines is controlled by the options -passed to pcre_compile() or by a special sequence at the start of the -pattern, as described in the section entitled -"Newline conventions" -in the pcrepattern documentation. Note that the end of this type of -comment is a literal newline sequence in the pattern; escape sequences that -happen to represent a newline do not count. -

-

-This option makes it possible to include comments inside complicated patterns. -Note, however, that this applies only to data characters. White space characters -may never appear within special character sequences in a pattern, for example -within the sequence (?( that introduces a conditional subpattern. -

-  PCRE_EXTRA
-
-This option was invented in order to turn on additional functionality of PCRE -that is incompatible with Perl, but it is currently of very little use. When -set, any backslash in a pattern that is followed by a letter that has no -special meaning causes an error, thus reserving these combinations for future -expansion. By default, as in Perl, a backslash followed by a letter with no -special meaning is treated as a literal. (Perl can, however, be persuaded to -give an error for this, by running it with the -w option.) There are at present -no other features controlled by this option. It can also be set by a (?X) -option setting within a pattern. -
-  PCRE_FIRSTLINE
-
-If this option is set, an unanchored pattern is required to match before or at -the first newline in the subject string, though the matched text may continue -over the newline. -
-  PCRE_JAVASCRIPT_COMPAT
-
-If this option is set, PCRE's behaviour is changed in some ways so that it is -compatible with JavaScript rather than Perl. The changes are as follows: -

-

-(1) A lone closing square bracket in a pattern causes a compile-time error, -because this is illegal in JavaScript (by default it is treated as a data -character). Thus, the pattern AB]CD becomes illegal when this option is set. -

-

-(2) At run time, a back reference to an unset subpattern group matches an empty -string (by default this causes the current matching alternative to fail). A -pattern such as (\1)(a) succeeds when this option is set (assuming it can find -an "a" in the subject), whereas it fails by default, for Perl compatibility. -

-

-(3) \U matches an upper case "U" character; by default \U causes a compile -time error (Perl uses \U to upper case subsequent characters). -

-

-(4) \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 uses it to upper -case the following character). -

-

-(5) \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). -

-  PCRE_MULTILINE
-
-By default, for the purposes of matching "start of line" and "end of line", -PCRE treats the subject string as consisting of a single line of characters, -even if it actually contains newlines. The "start of line" metacharacter (^) -matches only at the start of the string, and the "end of line" metacharacter -($) matches only at the end of the string, or before a terminating newline -(except when PCRE_DOLLAR_ENDONLY is set). Note, however, that unless -PCRE_DOTALL is set, the "any character" metacharacter (.) does not match at a -newline. This behaviour (for ^, $, and dot) is the same as Perl. -

-

-When PCRE_MULTILINE it is set, the "start of line" and "end of line" constructs -match immediately following or immediately before internal newlines in the -subject string, respectively, as well as at the very start and end. This is -equivalent to Perl's /m option, and it can be changed within a pattern by a -(?m) option setting. If there are no newlines in a subject string, or no -occurrences of ^ or $ in a pattern, setting PCRE_MULTILINE has no effect. -

-  PCRE_NEVER_UTF
-
-This option locks out interpretation of the pattern as UTF-8 (or UTF-16 or -UTF-32 in the 16-bit and 32-bit libraries). In particular, it prevents the -creator of the pattern from switching to UTF interpretation by starting the -pattern with (*UTF). This may be useful in applications that process patterns -from external sources. The combination of PCRE_UTF8 and PCRE_NEVER_UTF also -causes an error. -
-  PCRE_NEWLINE_CR
-  PCRE_NEWLINE_LF
-  PCRE_NEWLINE_CRLF
-  PCRE_NEWLINE_ANYCRLF
-  PCRE_NEWLINE_ANY
-
-These options override the default newline definition that was chosen when PCRE -was built. Setting the first or the second specifies that a newline is -indicated by a single character (CR or LF, respectively). Setting -PCRE_NEWLINE_CRLF specifies that a newline is indicated by the two-character -CRLF sequence. Setting PCRE_NEWLINE_ANYCRLF specifies that any of the three -preceding sequences should be recognized. Setting PCRE_NEWLINE_ANY specifies -that any Unicode newline sequence should be recognized. -

-

-In an ASCII/Unicode environment, the Unicode newline sequences are the three -just mentioned, plus the single characters VT (vertical tab, U+000B), FF (form -feed, U+000C), NEL (next line, U+0085), LS (line separator, U+2028), and PS -(paragraph separator, U+2029). For the 8-bit library, the last two are -recognized only in UTF-8 mode. -

-

-When PCRE is compiled to run in an EBCDIC (mainframe) environment, the code for -CR is 0x0d, the same as ASCII. However, the character code for LF is normally -0x15, though in some EBCDIC environments 0x25 is used. Whichever of these is -not LF is made to correspond to Unicode's NEL character. EBCDIC codes are all -less than 256. For more details, see the -pcrebuild -documentation. -

-

-The newline setting in the options word uses three bits that are treated -as a number, giving eight possibilities. Currently only six are used (default -plus the five values above). This means that if you set more than one newline -option, the combination may or may not be sensible. For example, -PCRE_NEWLINE_CR with PCRE_NEWLINE_LF is equivalent to PCRE_NEWLINE_CRLF, but -other combinations may yield unused numbers and cause an error. -

-

-The only time that a line break in a pattern is specially recognized when -compiling is when PCRE_EXTENDED is set. CR and LF are white space characters, -and so are ignored in this mode. Also, an unescaped # outside a character class -indicates a comment that lasts until after the next line break sequence. In -other circumstances, line break sequences in patterns are treated as literal -data. -

-

-The newline option that is set at compile time becomes the default that is used -for pcre_exec() and pcre_dfa_exec(), but it can be overridden. -

-  PCRE_NO_AUTO_CAPTURE
-
-If this option is set, it disables the use of numbered capturing parentheses in -the pattern. Any opening parenthesis that is not followed by ? behaves as if it -were followed by ?: but named parentheses can still be used for capturing (and -they acquire numbers in the usual way). There is no equivalent of this option -in Perl. -
-  PCRE_NO_AUTO_POSSESS
-
-If this option is set, it disables "auto-possessification". This is an -optimization that, for example, turns a+b into a++b in order to avoid -backtracks into a+ that can never be successful. However, if callouts are in -use, auto-possessification means that some of them are never taken. You can set -this option if you want the matching functions to do a full unoptimized search -and run all the callouts, but it is mainly provided for testing purposes. -
-  PCRE_NO_START_OPTIMIZE
-
-This is an option that acts at matching time; that is, it is really an option -for pcre_exec() or pcre_dfa_exec(). If it is set at compile time, -it is remembered with the compiled pattern and assumed at matching time. This -is necessary if you want to use JIT execution, because the JIT compiler needs -to know whether or not this option is set. For details see the discussion of -PCRE_NO_START_OPTIMIZE -below. -
-  PCRE_UCP
-
-This option changes the way PCRE processes \B, \b, \D, \d, \S, \s, \W, -\w, and some of the POSIX character classes. By default, only ASCII characters -are recognized, but if PCRE_UCP is set, Unicode properties are used instead to -classify characters. More details are given in the section on -generic character types -in the -pcrepattern -page. If you set PCRE_UCP, matching one of the items it affects takes much -longer. The option is available only if PCRE has been compiled with Unicode -property support. -
-  PCRE_UNGREEDY
-
-This option inverts the "greediness" of the quantifiers so that they are not -greedy by default, but become greedy if followed by "?". It is not compatible -with Perl. It can also be set by a (?U) option setting within the pattern. -
-  PCRE_UTF8
-
-This option causes PCRE to regard both the pattern and the subject as strings -of UTF-8 characters instead of single-byte strings. However, it is available -only when PCRE is built to include UTF support. If not, the use of this option -provokes an error. Details of how this option changes the behaviour of PCRE are -given in the -pcreunicode -page. -
-  PCRE_NO_UTF8_CHECK
-
-When PCRE_UTF8 is set, the validity of the pattern as a UTF-8 string is -automatically checked. There is a discussion about the -validity of UTF-8 strings -in the -pcreunicode -page. If an invalid UTF-8 sequence is found, pcre_compile() returns an -error. If you already know that your pattern is valid, and you want to skip -this check for performance reasons, you can set the PCRE_NO_UTF8_CHECK option. -When it is set, the effect of passing an invalid UTF-8 string as a pattern is -undefined. It may cause your program to crash or loop. Note that this option -can also be passed to pcre_exec() and pcre_dfa_exec(), to suppress -the validity checking of subject strings only. If the same string is being -matched many times, the option can be safely set for the second and subsequent -matchings to improve performance. -

-
COMPILATION ERROR CODES
-

-The following table lists the error codes than may be returned by -pcre_compile2(), along with the error messages that may be returned by -both compiling functions. Note that error messages are always 8-bit ASCII -strings, even in 16-bit or 32-bit mode. As PCRE has developed, some error codes -have fallen out of use. To avoid confusion, they have not been re-used. -

-   0  no error
-   1  \ at end of pattern
-   2  \c at end of pattern
-   3  unrecognized character follows \
-   4  numbers out of order in {} quantifier
-   5  number too big in {} quantifier
-   6  missing terminating ] for character class
-   7  invalid escape sequence in character class
-   8  range out of order in character class
-   9  nothing to repeat
-  10  [this code is not in use]
-  11  internal error: unexpected repeat
-  12  unrecognized character after (? or (?-
-  13  POSIX named classes are supported only within a class
-  14  missing )
-  15  reference to non-existent subpattern
-  16  erroffset passed as NULL
-  17  unknown option bit(s) set
-  18  missing ) after comment
-  19  [this code is not in use]
-  20  regular expression is too large
-  21  failed to get memory
-  22  unmatched parentheses
-  23  internal error: code overflow
-  24  unrecognized character after (?<
-  25  lookbehind assertion is not fixed length
-  26  malformed number or name after (?(
-  27  conditional group contains more than two branches
-  28  assertion expected after (?(
-  29  (?R or (?[+-]digits must be followed by )
-  30  unknown POSIX class name
-  31  POSIX collating elements are not supported
-  32  this version of PCRE is compiled without UTF support
-  33  [this code is not in use]
-  34  character value in \x{} or \o{} is too large
-  35  invalid condition (?(0)
-  36  \C not allowed in lookbehind assertion
-  37  PCRE does not support \L, \l, \N{name}, \U, or \u
-  38  number after (?C is > 255
-  39  closing ) for (?C expected
-  40  recursive call could loop indefinitely
-  41  unrecognized character after (?P
-  42  syntax error in subpattern name (missing terminator)
-  43  two named subpatterns have the same name
-  44  invalid UTF-8 string (specifically UTF-8)
-  45  support for \P, \p, and \X has not been compiled
-  46  malformed \P or \p sequence
-  47  unknown property name after \P or \p
-  48  subpattern name is too long (maximum 32 characters)
-  49  too many named subpatterns (maximum 10000)
-  50  [this code is not in use]
-  51  octal value is greater than \377 in 8-bit non-UTF-8 mode
-  52  internal error: overran compiling workspace
-  53  internal error: previously-checked referenced subpattern
-        not found
-  54  DEFINE group contains more than one branch
-  55  repeating a DEFINE group is not allowed
-  56  inconsistent NEWLINE options
-  57  \g is not followed by a braced, angle-bracketed, or quoted
-        name/number or by a plain number
-  58  a numbered reference must not be zero
-  59  an argument is not allowed for (*ACCEPT), (*FAIL), or (*COMMIT)
-  60  (*VERB) not recognized or malformed
-  61  number is too big
-  62  subpattern name expected
-  63  digit expected after (?+
-  64  ] is an invalid data character in JavaScript compatibility mode
-  65  different names for subpatterns of the same number are
-        not allowed
-  66  (*MARK) must have an argument
-  67  this version of PCRE is not compiled with Unicode property
-        support
-  68  \c must be followed by an ASCII character
-  69  \k is not followed by a braced, angle-bracketed, or quoted name
-  70  internal error: unknown opcode in find_fixedlength()
-  71  \N is not supported in a class
-  72  too many forward references
-  73  disallowed Unicode code point (>= 0xd800 && <= 0xdfff)
-  74  invalid UTF-16 string (specifically UTF-16)
-  75  name is too long in (*MARK), (*PRUNE), (*SKIP), or (*THEN)
-  76  character value in \u.... sequence is too large
-  77  invalid UTF-32 string (specifically UTF-32)
-  78  setting UTF is disabled by the application
-  79  non-hex character in \x{} (closing brace missing?)
-  80  non-octal character in \o{} (closing brace missing?)
-  81  missing opening brace after \o
-  82  parentheses are too deeply nested
-  83  invalid range in character class
-  84  group name must start with a non-digit
-  85  parentheses are too deeply nested (stack check)
-
-The numbers 32 and 10000 in errors 48 and 49 are defaults; different values may -be used if the limits were changed when PCRE was built. -

-
STUDYING A PATTERN
-

-pcre_extra *pcre_study(const pcre *code, int options, - const char **errptr); -

-

-If a compiled pattern is going to be used several times, it is worth spending -more time analyzing it in order to speed up the time taken for matching. The -function pcre_study() takes a pointer to a compiled pattern as its first -argument. If studying the pattern produces additional information that will -help speed up matching, pcre_study() returns a pointer to a -pcre_extra block, in which the study_data field points to the -results of the study. -

-

-The returned value from pcre_study() can be passed directly to -pcre_exec() or pcre_dfa_exec(). However, a pcre_extra block -also contains other fields that can be set by the caller before the block is -passed; these are described -below -in the section on matching a pattern. -

-

-If studying the pattern does not produce any useful information, -pcre_study() returns NULL by default. In that circumstance, if the -calling program wants to pass any of the other fields to pcre_exec() or -pcre_dfa_exec(), it must set up its own pcre_extra block. However, -if pcre_study() is called with the PCRE_STUDY_EXTRA_NEEDED option, it -returns a pcre_extra block even if studying did not find any additional -information. It may still return NULL, however, if an error occurs in -pcre_study(). -

-

-The second argument of pcre_study() contains option bits. There are three -further options in addition to PCRE_STUDY_EXTRA_NEEDED: -

-  PCRE_STUDY_JIT_COMPILE
-  PCRE_STUDY_JIT_PARTIAL_HARD_COMPILE
-  PCRE_STUDY_JIT_PARTIAL_SOFT_COMPILE
-
-If any of these are set, and the just-in-time compiler is available, the -pattern is further compiled into machine code that executes much faster than -the pcre_exec() interpretive matching function. If the just-in-time -compiler is not available, these options are ignored. All undefined bits in the -options argument must be zero. -

-

-JIT compilation is a heavyweight optimization. It can take some time for -patterns to be analyzed, and for one-off matches and simple patterns the -benefit of faster execution might be offset by a much slower study time. -Not all patterns can be optimized by the JIT compiler. For those that cannot be -handled, matching automatically falls back to the pcre_exec() -interpreter. For more details, see the -pcrejit -documentation. -

-

-The third argument for pcre_study() is a pointer for an error message. If -studying succeeds (even if no data is returned), the variable it points to is -set to NULL. Otherwise it is set to point to a textual error message. This is a -static string that is part of the library. You must not try to free it. You -should test the error pointer for NULL after calling pcre_study(), to be -sure that it has run successfully. -

-

-When you are finished with a pattern, you can free the memory used for the -study data by calling pcre_free_study(). This function was added to the -API for release 8.20. For earlier versions, the memory could be freed with -pcre_free(), just like the pattern itself. This will still work in cases -where JIT optimization is not used, but it is advisable to change to the new -function when convenient. -

-

-This is a typical way in which pcre_study() is used (except that in a -real application there should be tests for errors): -

-  int rc;
-  pcre *re;
-  pcre_extra *sd;
-  re = pcre_compile("pattern", 0, &error, &erroroffset, NULL);
-  sd = pcre_study(
-    re,             /* result of pcre_compile() */
-    0,              /* no options */
-    &error);        /* set to NULL or points to a message */
-  rc = pcre_exec(   /* see below for details of pcre_exec() options */
-    re, sd, "subject", 7, 0, 0, ovector, 30);
-  ...
-  pcre_free_study(sd);
-  pcre_free(re);
-
-Studying a pattern does two things: first, a lower bound for the length of -subject string that is needed to match the pattern is computed. This does not -mean that there are any strings of that length that match, but it does -guarantee that no shorter strings match. The value is used to avoid wasting -time by trying to match strings that are shorter than the lower bound. You can -find out the value in a calling program via the pcre_fullinfo() function. -

-

-Studying a pattern is also useful for non-anchored patterns that do not have a -single fixed starting character. A bitmap of possible starting bytes is -created. This speeds up finding a position in the subject at which to start -matching. (In 16-bit mode, the bitmap is used for 16-bit values less than 256. -In 32-bit mode, the bitmap is used for 32-bit values less than 256.) -

-

-These two optimizations apply to both pcre_exec() and -pcre_dfa_exec(), and the information is also used by the JIT compiler. -The optimizations can be disabled by setting the PCRE_NO_START_OPTIMIZE option. -You might want to do this if your pattern contains callouts or (*MARK) and you -want to make use of these facilities in cases where matching fails. -

-

-PCRE_NO_START_OPTIMIZE can be specified at either compile time or execution -time. However, if PCRE_NO_START_OPTIMIZE is passed to pcre_exec(), (that -is, after any JIT compilation has happened) JIT execution is disabled. For JIT -execution to work with PCRE_NO_START_OPTIMIZE, the option must be set at -compile time. -

-

-There is a longer discussion of PCRE_NO_START_OPTIMIZE -below. -

-
LOCALE SUPPORT
-

-PCRE handles caseless matching, and determines whether characters are letters, -digits, or whatever, by reference to a set of tables, indexed by character -code point. When running in UTF-8 mode, or in the 16- or 32-bit libraries, this -applies only to characters with code points less than 256. By default, -higher-valued code points never match escapes such as \w or \d. However, if -PCRE is built with Unicode property support, all characters can be tested with -\p and \P, or, alternatively, the PCRE_UCP option can be set when a pattern -is compiled; this causes \w and friends to use Unicode property support -instead of the built-in tables. -

-

-The use of locales with Unicode is discouraged. If you are handling characters -with code points greater than 128, you should either use Unicode support, or -use locales, but not try to mix the two. -

-

-PCRE contains an internal set of tables that are used when the final argument -of pcre_compile() is NULL. These are sufficient for many applications. -Normally, the internal tables recognize only ASCII characters. However, when -PCRE is built, it is possible to cause the internal tables to be rebuilt in the -default "C" locale of the local system, which may cause them to be different. -

-

-The internal tables can always be overridden by tables supplied by the -application that calls PCRE. These may be created in a different locale from -the default. As more and more applications change to using Unicode, the need -for this locale support is expected to die away. -

-

-External tables are built by calling the pcre_maketables() function, -which has no arguments, in the relevant locale. The result can then be passed -to pcre_compile() as often as necessary. For example, to build and use -tables that are appropriate for the French locale (where accented characters -with values greater than 128 are treated as letters), the following code could -be used: -

-  setlocale(LC_CTYPE, "fr_FR");
-  tables = pcre_maketables();
-  re = pcre_compile(..., tables);
-
-The locale name "fr_FR" is used on Linux and other Unix-like systems; if you -are using Windows, the name for the French locale is "french". -

-

-When pcre_maketables() runs, the tables are built in memory that is -obtained via pcre_malloc. It is the caller's responsibility to ensure -that the memory containing the tables remains available for as long as it is -needed. -

-

-The pointer that is passed to pcre_compile() is saved with the compiled -pattern, and the same tables are used via this pointer by pcre_study() -and also by pcre_exec() and pcre_dfa_exec(). Thus, for any single -pattern, compilation, studying and matching all happen in the same locale, but -different patterns can be processed in different locales. -

-

-It is possible to pass a table pointer or NULL (indicating the use of the -internal tables) to pcre_exec() or pcre_dfa_exec() (see the -discussion below in the section on matching a pattern). This facility is -provided for use with pre-compiled patterns that have been saved and reloaded. -Character tables are not saved with patterns, so if a non-standard table was -used at compile time, it must be provided again when the reloaded pattern is -matched. Attempting to use this facility to match a pattern in a different -locale from the one in which it was compiled is likely to lead to anomalous -(usually incorrect) results. -

-
INFORMATION ABOUT A PATTERN
-

-int pcre_fullinfo(const pcre *code, const pcre_extra *extra, - int what, void *where); -

-

-The pcre_fullinfo() function returns information about a compiled -pattern. It replaces the pcre_info() function, which was removed from the -library at version 8.30, after more than 10 years of obsolescence. -

-

-The first argument for pcre_fullinfo() is a pointer to the compiled -pattern. The second argument is the result of pcre_study(), or NULL if -the pattern was not studied. The third argument specifies which piece of -information is required, and the fourth argument is a pointer to a variable -to receive the data. The yield of the function is zero for success, or one of -the following negative numbers: -

-  PCRE_ERROR_NULL           the argument code was NULL
-                            the argument where was NULL
-  PCRE_ERROR_BADMAGIC       the "magic number" was not found
-  PCRE_ERROR_BADENDIANNESS  the pattern was compiled with different
-                            endianness
-  PCRE_ERROR_BADOPTION      the value of what was invalid
-  PCRE_ERROR_UNSET          the requested field is not set
-
-The "magic number" is placed at the start of each compiled pattern as an simple -check against passing an arbitrary memory pointer. The endianness error can -occur if a compiled pattern is saved and reloaded on a different host. Here is -a typical call of pcre_fullinfo(), to obtain the length of the compiled -pattern: -
-  int rc;
-  size_t length;
-  rc = pcre_fullinfo(
-    re,               /* result of pcre_compile() */
-    sd,               /* result of pcre_study(), or NULL */
-    PCRE_INFO_SIZE,   /* what is required */
-    &length);         /* where to put the data */
-
-The possible values for the third argument are defined in pcre.h, and are -as follows: -
-  PCRE_INFO_BACKREFMAX
-
-Return the number of the highest back reference in the pattern. The fourth -argument should point to an int variable. Zero is returned if there are -no back references. -
-  PCRE_INFO_CAPTURECOUNT
-
-Return the number of capturing subpatterns in the pattern. The fourth argument -should point to an int variable. -
-  PCRE_INFO_DEFAULT_TABLES
-
-Return a pointer to the internal default character tables within PCRE. The -fourth argument should point to an unsigned char * variable. This -information call is provided for internal use by the pcre_study() -function. External callers can cause PCRE to use its internal tables by passing -a NULL table pointer. -
-  PCRE_INFO_FIRSTBYTE (deprecated)
-
-Return information about the first data unit of any matched string, for a -non-anchored pattern. The name of this option refers to the 8-bit library, -where data units are bytes. The fourth argument should point to an int -variable. Negative values are used for special cases. However, this means that -when the 32-bit library is in non-UTF-32 mode, the full 32-bit range of -characters cannot be returned. For this reason, this value is deprecated; use -PCRE_INFO_FIRSTCHARACTERFLAGS and PCRE_INFO_FIRSTCHARACTER instead. -

-

-If there is a fixed first value, for example, the letter "c" from a pattern -such as (cat|cow|coyote), its value is returned. In the 8-bit library, the -value is always less than 256. In the 16-bit library the value can be up to -0xffff. In the 32-bit library the value can be up to 0x10ffff. -

-

-If there is no fixed first value, and if either -
-
-(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch -starts with "^", or -
-
-(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set -(if it were set, the pattern would be anchored), -
-
--1 is returned, indicating that the pattern matches only at the start of a -subject string or after any newline within the string. Otherwise -2 is -returned. For anchored patterns, -2 is returned. -

-  PCRE_INFO_FIRSTCHARACTER
-
-Return the value of the first data unit (non-UTF character) of any matched -string in the situation where PCRE_INFO_FIRSTCHARACTERFLAGS returns 1; -otherwise return 0. The fourth argument should point to an uint_t -variable. -

-

-In the 8-bit library, the value is always less than 256. In the 16-bit library -the value can be up to 0xffff. In the 32-bit library in UTF-32 mode the value -can be up to 0x10ffff, and up to 0xffffffff when not using UTF-32 mode. -

-  PCRE_INFO_FIRSTCHARACTERFLAGS
-
-Return information about the first data unit of any matched string, for a -non-anchored pattern. The fourth argument should point to an int -variable. -

-

-If there is a fixed first value, for example, the letter "c" from a pattern -such as (cat|cow|coyote), 1 is returned, and the character value can be -retrieved using PCRE_INFO_FIRSTCHARACTER. If there is no fixed first value, and -if either -
-
-(a) the pattern was compiled with the PCRE_MULTILINE option, and every branch -starts with "^", or -
-
-(b) every branch of the pattern starts with ".*" and PCRE_DOTALL is not set -(if it were set, the pattern would be anchored), -
-
-2 is returned, indicating that the pattern matches only at the start of a -subject string or after any newline within the string. Otherwise 0 is -returned. For anchored patterns, 0 is returned. -

-  PCRE_INFO_FIRSTTABLE
-
-If the pattern was studied, and this resulted in the construction of a 256-bit -table indicating a fixed set of values for the first data unit in any matching -string, a pointer to the table is returned. Otherwise NULL is returned. The -fourth argument should point to an unsigned char * variable. -
-  PCRE_INFO_HASCRORLF
-
-Return 1 if the pattern contains any explicit matches for CR or LF characters, -otherwise 0. The fourth argument should point to an int variable. An -explicit match is either a literal CR or LF character, or \r or \n. -
-  PCRE_INFO_JCHANGED
-
-Return 1 if the (?J) or (?-J) option setting is used in the pattern, otherwise -0. The fourth argument should point to an int variable. (?J) and -(?-J) set and unset the local PCRE_DUPNAMES option, respectively. -
-  PCRE_INFO_JIT
-
-Return 1 if the pattern was studied with one of the JIT options, and -just-in-time compiling was successful. The fourth argument should point to an -int variable. A return value of 0 means that JIT support is not available -in this version of PCRE, or that the pattern was not studied with a JIT option, -or that the JIT compiler could not handle this particular pattern. See the -pcrejit -documentation for details of what can and cannot be handled. -
-  PCRE_INFO_JITSIZE
-
-If the pattern was successfully studied with a JIT option, return the size of -the JIT compiled code, otherwise return zero. The fourth argument should point -to a size_t variable. -
-  PCRE_INFO_LASTLITERAL
-
-Return the value of the rightmost literal data unit that must exist in any -matched string, other than at its start, if such a value has been recorded. The -fourth argument should point to an int variable. If there is no such -value, -1 is returned. For anchored patterns, a last literal value is recorded -only if it follows something of variable length. For example, for the pattern -/^a\d+z\d+/ the returned value is "z", but for /^a\dz\d/ the returned value -is -1. -

-

-Since for the 32-bit library using the non-UTF-32 mode, this function is unable -to return the full 32-bit range of characters, this value is deprecated; -instead the PCRE_INFO_REQUIREDCHARFLAGS and PCRE_INFO_REQUIREDCHAR values should -be used. -

-  PCRE_INFO_MATCH_EMPTY
-
-Return 1 if the pattern can match an empty string, otherwise 0. The fourth -argument should point to an int variable. -
-  PCRE_INFO_MATCHLIMIT
-
-If the pattern set a match limit by including an item of the form -(*LIMIT_MATCH=nnnn) at the start, the value is returned. The fourth argument -should point to an unsigned 32-bit integer. If no such value has been set, the -call to pcre_fullinfo() returns the error PCRE_ERROR_UNSET. -
-  PCRE_INFO_MAXLOOKBEHIND
-
-Return the number of characters (NB not data units) in the longest lookbehind -assertion in the pattern. This information is useful when doing multi-segment -matching using the partial matching facilities. Note that the simple assertions -\b and \B require a one-character lookbehind. \A also registers a -one-character lookbehind, though it does not actually inspect the previous -character. This is to ensure that at least one character from the old segment -is retained when a new segment is processed. Otherwise, if there are no -lookbehinds in the pattern, \A might match incorrectly at the start of a new -segment. -
-  PCRE_INFO_MINLENGTH
-
-If the pattern was studied and a minimum length for matching subject strings -was computed, its value is returned. Otherwise the returned value is -1. The -value is a number of characters, which in UTF mode may be different from the -number of data units. The fourth argument should point to an int -variable. A non-negative value is a lower bound to the length of any matching -string. There may not be any strings of that length that do actually match, but -every string that does match is at least that long. -
-  PCRE_INFO_NAMECOUNT
-  PCRE_INFO_NAMEENTRYSIZE
-  PCRE_INFO_NAMETABLE
-
-PCRE supports the use of named as well as numbered capturing parentheses. The -names are just an additional way of identifying the parentheses, which still -acquire numbers. Several convenience functions such as -pcre_get_named_substring() are provided for extracting captured -substrings by name. It is also possible to extract the data directly, by first -converting the name to a number in order to access the correct pointers in the -output vector (described with pcre_exec() below). To do the conversion, -you need to use the name-to-number map, which is described by these three -values. -

-

-The map consists of a number of fixed-size entries. PCRE_INFO_NAMECOUNT gives -the number of entries, and PCRE_INFO_NAMEENTRYSIZE gives the size of each -entry; both of these return an int value. The entry size depends on the -length of the longest name. PCRE_INFO_NAMETABLE returns a pointer to the first -entry of the table. This is a pointer to char in the 8-bit library, where -the first two bytes of each entry are the number of the capturing parenthesis, -most significant byte first. In the 16-bit library, the pointer points to -16-bit data units, the first of which contains the parenthesis number. In the -32-bit library, the pointer points to 32-bit data units, the first of which -contains the parenthesis number. The rest of the entry is the corresponding -name, zero terminated. -

-

-The names are in alphabetical order. If (?| is used to create multiple groups -with the same number, as described in the -section on duplicate subpattern numbers -in the -pcrepattern -page, the groups may be given the same name, but there is only one entry in the -table. Different names for groups of the same number are not permitted. -Duplicate names for subpatterns with different numbers are permitted, -but only if PCRE_DUPNAMES is set. They appear in the table in the order in -which they were found in the pattern. In the absence of (?| this is the order -of increasing number; when (?| is used this is not necessarily the case because -later subpatterns may have lower numbers. -

-

-As a simple example of the name/number table, consider the following pattern -after compilation by the 8-bit library (assume PCRE_EXTENDED is set, so white -space - including newlines - is ignored): -

-  (?<date> (?<year>(\d\d)?\d\d) - (?<month>\d\d) - (?<day>\d\d) )
-
-There are four named subpatterns, so the table has four entries, and each entry -in the table is eight bytes long. The table is as follows, with non-printing -bytes shows in hexadecimal, and undefined bytes shown as ??: -
-  00 01 d  a  t  e  00 ??
-  00 05 d  a  y  00 ?? ??
-  00 04 m  o  n  t  h  00
-  00 02 y  e  a  r  00 ??
-
-When writing code to extract data from named subpatterns using the -name-to-number map, remember that the length of the entries is likely to be -different for each compiled pattern. -
-  PCRE_INFO_OKPARTIAL
-
-Return 1 if the pattern can be used for partial matching with -pcre_exec(), otherwise 0. The fourth argument should point to an -int variable. From release 8.00, this always returns 1, because the -restrictions that previously applied to partial matching have been lifted. The -pcrepartial -documentation gives details of partial matching. -
-  PCRE_INFO_OPTIONS
-
-Return a copy of the options with which the pattern was compiled. The fourth -argument should point to an unsigned long int variable. These option bits -are those specified in the call to pcre_compile(), modified by any -top-level option settings at the start of the pattern itself. In other words, -they are the options that will be in force when matching starts. For example, -if the pattern /(?im)abc(?-i)d/ is compiled with the PCRE_EXTENDED option, the -result is PCRE_CASELESS, PCRE_MULTILINE, and PCRE_EXTENDED. -

-

-A pattern is automatically anchored by PCRE if all of its top-level -alternatives begin with one of the following: -

-  ^     unless PCRE_MULTILINE is set
-  \A    always
-  \G    always
-  .*    if PCRE_DOTALL is set and there are no back references to the subpattern in which .* appears
-
-For such patterns, the PCRE_ANCHORED bit is set in the options returned by -pcre_fullinfo(). -
-  PCRE_INFO_RECURSIONLIMIT
-
-If the pattern set a recursion limit by including an item of the form -(*LIMIT_RECURSION=nnnn) at the start, the value is returned. The fourth -argument should point to an unsigned 32-bit integer. If no such value has been -set, the call to pcre_fullinfo() returns the error PCRE_ERROR_UNSET. -
-  PCRE_INFO_SIZE
-
-Return the size of the compiled pattern in bytes (for all three libraries). The -fourth argument should point to a size_t variable. This value does not -include the size of the pcre structure that is returned by -pcre_compile(). The value that is passed as the argument to -pcre_malloc() when pcre_compile() is getting memory in which to -place the compiled data is the value returned by this option plus the size of -the pcre structure. Studying a compiled pattern, with or without JIT, -does not alter the value returned by this option. -
-  PCRE_INFO_STUDYSIZE
-
-Return the size in bytes (for all three libraries) of the data block pointed to -by the study_data field in a pcre_extra block. If pcre_extra -is NULL, or there is no study data, zero is returned. The fourth argument -should point to a size_t variable. The study_data field is set by -pcre_study() to record information that will speed up matching (see the -section entitled -"Studying a pattern" -above). The format of the study_data block is private, but its length -is made available via this option so that it can be saved and restored (see the -pcreprecompile -documentation for details). -
-  PCRE_INFO_REQUIREDCHARFLAGS
-
-Returns 1 if there is a rightmost literal data unit that must exist in any -matched string, other than at its start. The fourth argument should point to -an int variable. If there is no such value, 0 is returned. If returning -1, the character value itself can be retrieved using PCRE_INFO_REQUIREDCHAR. -

-

-For anchored patterns, a last literal value is recorded only if it follows -something of variable length. For example, for the pattern /^a\d+z\d+/ the -returned value 1 (with "z" returned from PCRE_INFO_REQUIREDCHAR), but for -/^a\dz\d/ the returned value is 0. -

-  PCRE_INFO_REQUIREDCHAR
-
-Return the value of the rightmost literal data unit that must exist in any -matched string, other than at its start, if such a value has been recorded. The -fourth argument should point to an uint32_t variable. If there is no such -value, 0 is returned. -

-
REFERENCE COUNTS
-

-int pcre_refcount(pcre *code, int adjust); -

-

-The pcre_refcount() function is used to maintain a reference count in the -data block that contains a compiled pattern. It is provided for the benefit of -applications that operate in an object-oriented manner, where different parts -of the application may be using the same compiled pattern, but you want to free -the block when they are all done. -

-

-When a pattern is compiled, the reference count field is initialized to zero. -It is changed only by calling this function, whose action is to add the -adjust value (which may be positive or negative) to it. The yield of the -function is the new value. However, the value of the count is constrained to -lie between 0 and 65535, inclusive. If the new value is outside these limits, -it is forced to the appropriate limit value. -

-

-Except when it is zero, the reference count is not correctly preserved if a -pattern is compiled on one host and then transferred to a host whose byte-order -is different. (This seems a highly unlikely scenario.) -

-
MATCHING A PATTERN: THE TRADITIONAL FUNCTION
-

-int pcre_exec(const pcre *code, const pcre_extra *extra, - const char *subject, int length, int startoffset, - int options, int *ovector, int ovecsize); -

-

-The function pcre_exec() is called to match a subject string against a -compiled pattern, which is passed in the code argument. If the -pattern was studied, the result of the study should be passed in the -extra argument. You can call pcre_exec() with the same code -and extra arguments as many times as you like, in order to match -different subject strings with the same pattern. -

-

-This function is the main matching facility of the library, and it operates in -a Perl-like manner. For specialist use there is also an alternative matching -function, which is described -below -in the section about the pcre_dfa_exec() function. -

-

-In most applications, the pattern will have been compiled (and optionally -studied) in the same process that calls pcre_exec(). However, it is -possible to save compiled patterns and study data, and then use them later -in different processes, possibly even on different hosts. For a discussion -about this, see the -pcreprecompile -documentation. -

-

-Here is an example of a simple call to pcre_exec(): -

-  int rc;
-  int ovector[30];
-  rc = pcre_exec(
-    re,             /* result of pcre_compile() */
-    NULL,           /* we didn't study the pattern */
-    "some string",  /* the subject string */
-    11,             /* the length of the subject string */
-    0,              /* start at offset 0 in the subject */
-    0,              /* default options */
-    ovector,        /* vector of integers for substring information */
-    30);            /* number of elements (NOT size in bytes) */
-
-

-
-Extra data for pcre_exec() -
-

-If the extra argument is not NULL, it must point to a pcre_extra -data block. The pcre_study() function returns such a block (when it -doesn't return NULL), but you can also create one for yourself, and pass -additional information in it. The pcre_extra block contains the following -fields (not necessarily in this order): -

-  unsigned long int flags;
-  void *study_data;
-  void *executable_jit;
-  unsigned long int match_limit;
-  unsigned long int match_limit_recursion;
-  void *callout_data;
-  const unsigned char *tables;
-  unsigned char **mark;
-
-In the 16-bit version of this structure, the mark field has type -"PCRE_UCHAR16 **". -
-
-In the 32-bit version of this structure, the mark field has type -"PCRE_UCHAR32 **". -

-

-The flags field is used to specify which of the other fields are set. The -flag bits are: -

-  PCRE_EXTRA_CALLOUT_DATA
-  PCRE_EXTRA_EXECUTABLE_JIT
-  PCRE_EXTRA_MARK
-  PCRE_EXTRA_MATCH_LIMIT
-  PCRE_EXTRA_MATCH_LIMIT_RECURSION
-  PCRE_EXTRA_STUDY_DATA
-  PCRE_EXTRA_TABLES
-
-Other flag bits should be set to zero. The study_data field and sometimes -the executable_jit field are set in the pcre_extra block that is -returned by pcre_study(), together with the appropriate flag bits. You -should not set these yourself, but you may add to the block by setting other -fields and their corresponding flag bits. -

-

-The match_limit field provides a means of preventing PCRE from using up a -vast amount of resources when running patterns that are not going to match, -but which have a very large number of possibilities in their search trees. The -classic example is a pattern that uses nested unlimited repeats. -

-

-Internally, pcre_exec() uses a function called match(), which it -calls repeatedly (sometimes recursively). The limit set by match_limit is -imposed on the number of times this function is called during a match, which -has the effect of limiting the amount of backtracking that can take place. For -patterns that are not anchored, the count restarts from zero for each position -in the subject string. -

-

-When pcre_exec() is called with a pattern that was successfully studied -with a JIT option, the way that the matching is executed is entirely different. -However, there is still the possibility of runaway matching that goes on for a -very long time, and so the match_limit value is also used in this case -(but in a different way) to limit how long the matching can continue. -

-

-The default value for the limit can be set when PCRE is built; the default -default is 10 million, which handles all but the most extreme cases. You can -override the default by suppling pcre_exec() with a pcre_extra -block in which match_limit is set, and PCRE_EXTRA_MATCH_LIMIT is set in -the flags field. If the limit is exceeded, pcre_exec() returns -PCRE_ERROR_MATCHLIMIT. -

-

-A value for the match limit may also be supplied by an item at the start of a -pattern of the form -

-  (*LIMIT_MATCH=d)
-
-where d is a decimal number. However, such a setting is ignored unless d is -less than the limit set by the caller of pcre_exec() or, if no such limit -is set, less than the default. -

-

-The match_limit_recursion field is similar to match_limit, but -instead of limiting the total number of times that match() is called, it -limits the depth of recursion. The recursion depth is a smaller number than the -total number of calls, because not all calls to match() are recursive. -This limit is of use only if it is set smaller than match_limit. -

-

-Limiting the recursion depth limits the amount of machine stack that can be -used, or, when PCRE has been compiled to use memory on the heap instead of the -stack, the amount of heap memory that can be used. This limit is not relevant, -and is ignored, when matching is done using JIT compiled code. -

-

-The default value for match_limit_recursion can be set when PCRE is -built; the default default is the same value as the default for -match_limit. You can override the default by suppling pcre_exec() -with a pcre_extra block in which match_limit_recursion is set, and -PCRE_EXTRA_MATCH_LIMIT_RECURSION is set in the flags field. If the limit -is exceeded, pcre_exec() returns PCRE_ERROR_RECURSIONLIMIT. -

-

-A value for the recursion limit may also be supplied by an item at the start of -a pattern of the form -

-  (*LIMIT_RECURSION=d)
-
-where d is a decimal number. However, such a setting is ignored unless d is -less than the limit set by the caller of pcre_exec() or, if no such limit -is set, less than the default. -

-

-The callout_data field is used in conjunction with the "callout" feature, -and is described in the -pcrecallout -documentation. -

-

-The tables field is provided for use with patterns that have been -pre-compiled using custom character tables, saved to disc or elsewhere, and -then reloaded, because the tables that were used to compile a pattern are not -saved with it. See the -pcreprecompile -documentation for a discussion of saving compiled patterns for later use. If -NULL is passed using this mechanism, it forces PCRE's internal tables to be -used. -

-

-Warning: The tables that pcre_exec() uses must be the same as those -that were used when the pattern was compiled. If this is not the case, the -behaviour of pcre_exec() is undefined. Therefore, when a pattern is -compiled and matched in the same process, this field should never be set. In -this (the most common) case, the correct table pointer is automatically passed -with the compiled pattern from pcre_compile() to pcre_exec(). -

-

-If PCRE_EXTRA_MARK is set in the flags field, the mark field must -be set to point to a suitable variable. If the pattern contains any -backtracking control verbs such as (*MARK:NAME), and the execution ends up with -a name to pass back, a pointer to the name string (zero terminated) is placed -in the variable pointed to by the mark field. The names are within the -compiled pattern; if you wish to retain such a name you must copy it before -freeing the memory of a compiled pattern. If there is no name to pass back, the -variable pointed to by the mark field is set to NULL. For details of the -backtracking control verbs, see the section entitled -"Backtracking control" -in the -pcrepattern -documentation. -

-
-Option bits for pcre_exec() -
-

-The unused bits of the options argument for pcre_exec() must be -zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx, -PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, -PCRE_NO_START_OPTIMIZE, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, and -PCRE_PARTIAL_SOFT. -

-

-If the pattern was successfully studied with one of the just-in-time (JIT) -compile options, the only supported options for JIT execution are -PCRE_NO_UTF8_CHECK, PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, -PCRE_NOTEMPTY_ATSTART, PCRE_PARTIAL_HARD, and PCRE_PARTIAL_SOFT. If an -unsupported option is used, JIT execution is disabled and the normal -interpretive code in pcre_exec() is run. -

-  PCRE_ANCHORED
-
-The PCRE_ANCHORED option limits pcre_exec() to matching at the first -matching position. If a pattern was compiled with PCRE_ANCHORED, or turned out -to be anchored by virtue of its contents, it cannot be made unachored at -matching time. -
-  PCRE_BSR_ANYCRLF
-  PCRE_BSR_UNICODE
-
-These options (which are mutually exclusive) control what the \R escape -sequence matches. The choice is either to match only CR, LF, or CRLF, or to -match any Unicode newline sequence. These options override the choice that was -made or defaulted when the pattern was compiled. -
-  PCRE_NEWLINE_CR
-  PCRE_NEWLINE_LF
-  PCRE_NEWLINE_CRLF
-  PCRE_NEWLINE_ANYCRLF
-  PCRE_NEWLINE_ANY
-
-These options override the newline definition that was chosen or defaulted when -the pattern was compiled. For details, see the description of -pcre_compile() above. During matching, the newline choice affects the -behaviour of the dot, circumflex, and dollar metacharacters. It may also alter -the way the match position is advanced after a match failure for an unanchored -pattern. -

-

-When PCRE_NEWLINE_CRLF, PCRE_NEWLINE_ANYCRLF, or PCRE_NEWLINE_ANY is set, and a -match attempt for an unanchored pattern fails when the current position is at a -CRLF sequence, and the pattern contains no explicit matches for CR or LF -characters, the match position is advanced by two characters instead of one, in -other words, to after the CRLF. -

-

-The above rule is a compromise that makes the most common cases work as -expected. For example, if the pattern is .+A (and the PCRE_DOTALL option is not -set), it does not match the string "\r\nA" because, after failing at the -start, it skips both the CR and the LF before retrying. However, the pattern -[\r\n]A does match that string, because it contains an explicit CR or LF -reference, and so advances only by one character after the first failure. -

-

-An explicit match for CR of LF is either a literal appearance of one of those -characters, or one of the \r or \n escape sequences. Implicit matches such as -[^X] do not count, nor does \s (which includes CR and LF in the characters -that it matches). -

-

-Notwithstanding the above, anomalous effects may still occur when CRLF is a -valid newline sequence and explicit \r or \n escapes appear in the pattern. -

-  PCRE_NOTBOL
-
-This option specifies that first character of the subject string is not the -beginning of a line, so the circumflex metacharacter should not match before -it. Setting this without PCRE_MULTILINE (at compile time) causes circumflex -never to match. This option affects only the behaviour of the circumflex -metacharacter. It does not affect \A. -
-  PCRE_NOTEOL
-
-This option specifies that the end of the subject string is not the end of a -line, so the dollar metacharacter should not match it nor (except in multiline -mode) a newline immediately before it. Setting this without PCRE_MULTILINE (at -compile time) causes dollar never to match. This option affects only the -behaviour of the dollar metacharacter. It does not affect \Z or \z. -
-  PCRE_NOTEMPTY
-
-An empty string is not considered to be a valid match if this option is set. If -there are alternatives in the pattern, they are tried. If all the alternatives -match the empty string, the entire match fails. For example, if the pattern -
-  a?b?
-
-is applied to a string not beginning with "a" or "b", it matches an empty -string at the start of the subject. With PCRE_NOTEMPTY set, this match is not -valid, so PCRE searches further into the string for occurrences of "a" or "b". -
-  PCRE_NOTEMPTY_ATSTART
-
-This is like PCRE_NOTEMPTY, except that an empty string match that is not at -the start of the subject is permitted. If the pattern is anchored, such a match -can occur only if the pattern contains \K. -

-

-Perl has no direct equivalent of PCRE_NOTEMPTY or PCRE_NOTEMPTY_ATSTART, but it -does make a special case of a pattern match of the empty string within its -split() function, and when using the /g modifier. It is possible to -emulate Perl's behaviour after matching a null string by first trying the match -again at the same offset with PCRE_NOTEMPTY_ATSTART and PCRE_ANCHORED, and then -if that fails, by advancing the starting offset (see below) and trying an -ordinary match again. There is some code that demonstrates how to do this in -the -pcredemo -sample program. In the most general case, you have to check to see if the -newline convention recognizes CRLF as a newline, and if so, and the current -character is CR followed by LF, advance the starting offset by two characters -instead of one. -

-  PCRE_NO_START_OPTIMIZE
-
-There are a number of optimizations that pcre_exec() uses at the start of -a match, in order to speed up the process. For example, if it is known that an -unanchored match must start with a specific character, it searches the subject -for that character, and fails immediately if it cannot find it, without -actually running the main matching function. This means that a special item -such as (*COMMIT) at the start of a pattern is not considered until after a -suitable starting point for the match has been found. Also, when callouts or -(*MARK) items are in use, these "start-up" optimizations can cause them to be -skipped if the pattern is never actually used. The start-up optimizations are -in effect a pre-scan of the subject that takes place before the pattern is run. -

-

-The PCRE_NO_START_OPTIMIZE option disables the start-up optimizations, possibly -causing performance to suffer, but ensuring that in cases where the result is -"no match", the callouts do occur, and that items such as (*COMMIT) and (*MARK) -are considered at every possible starting position in the subject string. If -PCRE_NO_START_OPTIMIZE is set at compile time, it cannot be unset at matching -time. The use of PCRE_NO_START_OPTIMIZE at matching time (that is, passing it -to pcre_exec()) disables JIT execution; in this situation, matching is -always done using interpretively. -

-

-Setting PCRE_NO_START_OPTIMIZE can change the outcome of a matching operation. -Consider the pattern -

-  (*COMMIT)ABC
-
-When this is compiled, PCRE records the fact that a match must start with the -character "A". Suppose the subject string is "DEFABC". The start-up -optimization scans along the subject, finds "A" and runs the first match -attempt from there. The (*COMMIT) item means that the pattern must match the -current starting position, which in this case, it does. However, if the same -match is run with PCRE_NO_START_OPTIMIZE set, the initial scan along the -subject string does not happen. The first match attempt is run starting from -"D" and when this fails, (*COMMIT) prevents any further matches being tried, so -the overall result is "no match". If the pattern is studied, more start-up -optimizations may be used. For example, a minimum length for the subject may be -recorded. Consider the pattern -
-  (*MARK:A)(X|Y)
-
-The minimum length for a match is one character. If the subject is "ABC", there -will be attempts to match "ABC", "BC", "C", and then finally an empty string. -If the pattern is studied, the final attempt does not take place, because PCRE -knows that the subject is too short, and so the (*MARK) is never encountered. -In this case, studying the pattern does not affect the overall match result, -which is still "no match", but it does affect the auxiliary information that is -returned. -
-  PCRE_NO_UTF8_CHECK
-
-When PCRE_UTF8 is set at compile time, the validity of the subject as a UTF-8 -string is automatically checked when pcre_exec() is subsequently called. -The entire string is checked before any other processing takes place. The value -of startoffset is also checked to ensure that it points to the start of a -UTF-8 character. There is a discussion about the -validity of UTF-8 strings -in the -pcreunicode -page. If an invalid sequence of bytes is found, pcre_exec() returns the -error PCRE_ERROR_BADUTF8 or, if PCRE_PARTIAL_HARD is set and the problem is a -truncated character at the end of the subject, PCRE_ERROR_SHORTUTF8. In both -cases, information about the precise nature of the error may also be returned -(see the descriptions of these errors in the section entitled \fIError return -values from\fP pcre_exec() -below). -If startoffset contains a value that does not point to the start of a -UTF-8 character (or to the end of the subject), PCRE_ERROR_BADUTF8_OFFSET is -returned. -

-

-If you already know that your subject is valid, and you want to skip these -checks for performance reasons, you can set the PCRE_NO_UTF8_CHECK option when -calling pcre_exec(). You might want to do this for the second and -subsequent calls to pcre_exec() if you are making repeated calls to find -all the matches in a single subject string. However, you should be sure that -the value of startoffset points to the start of a character (or the end -of the subject). When PCRE_NO_UTF8_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. -

-  PCRE_PARTIAL_HARD
-  PCRE_PARTIAL_SOFT
-
-These options turn on the partial matching feature. For backwards -compatibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial match -occurs if the end of the subject string is reached successfully, but there are -not enough subject characters to complete the match. If this happens when -PCRE_PARTIAL_SOFT (but not PCRE_PARTIAL_HARD) is set, matching continues by -testing any remaining alternatives. Only if no complete match can be found is -PCRE_ERROR_PARTIAL returned instead of PCRE_ERROR_NOMATCH. In other words, -PCRE_PARTIAL_SOFT says that the caller is prepared to handle a partial match, -but only if no complete match can be found. -

-

-If PCRE_PARTIAL_HARD is set, it overrides PCRE_PARTIAL_SOFT. In this case, if a -partial match is found, pcre_exec() immediately returns -PCRE_ERROR_PARTIAL, without considering any other alternatives. In other words, -when PCRE_PARTIAL_HARD is set, a partial match is considered to be more -important that an alternative complete match. -

-

-In both cases, the portion of the string that was inspected when the partial -match was found is set as the first matching string. There is a more detailed -discussion of partial and multi-segment matching, with examples, in the -pcrepartial -documentation. -

-
-The string to be matched by pcre_exec() -
-

-The subject string is passed to pcre_exec() as a pointer in -subject, a length in length, and a starting offset in -startoffset. The units for length and startoffset are bytes -for the 8-bit library, 16-bit data items for the 16-bit library, and 32-bit -data items for the 32-bit library. -

-

-If startoffset is negative or greater than the length of the subject, -pcre_exec() returns PCRE_ERROR_BADOFFSET. When the starting offset is -zero, the search for a match starts at the beginning of the subject, and this -is by far the most common case. In UTF-8 or UTF-16 mode, the offset must point -to the start of a character, or the end of the subject (in UTF-32 mode, one -data unit equals one character, so all offsets are valid). Unlike the pattern -string, the subject may contain binary zeroes. -

-

-A non-zero starting offset is useful when searching for another match in the -same subject by calling pcre_exec() again after a previous success. -Setting startoffset differs from just passing over a shortened string and -setting PCRE_NOTBOL in the case of a pattern that begins with any kind of -lookbehind. For example, consider the pattern -

-  \Biss\B
-
-which finds occurrences of "iss" in the middle of words. (\B matches only if -the current position in the subject is not a word boundary.) When applied to -the string "Mississipi" the first call to pcre_exec() finds the first -occurrence. If pcre_exec() is called again with just the remainder of the -subject, namely "issipi", it does not match, because \B is always false at the -start of the subject, which is deemed to be a word boundary. However, if -pcre_exec() is passed the entire string again, but with startoffset -set to 4, it finds the second occurrence of "iss" because it is able to look -behind the starting point to discover that it is preceded by a letter. -

-

-Finding all the matches in a subject is tricky when the pattern can match an -empty string. It is possible to emulate Perl's /g behaviour by first trying the -match again at the same offset, with the PCRE_NOTEMPTY_ATSTART and -PCRE_ANCHORED options, and then if that fails, advancing the starting offset -and trying an ordinary match again. There is some code that demonstrates how to -do this in the -pcredemo -sample program. In the most general case, you have to check to see if the -newline convention recognizes CRLF as a newline, and if so, and the current -character is CR followed by LF, advance the starting offset by two characters -instead of one. -

-

-If a non-zero starting offset is passed when the pattern is anchored, one -attempt to match at the given offset is made. This can only succeed if the -pattern does not require the match to be at the start of the subject. -

-
-How pcre_exec() returns captured substrings -
-

-In general, a pattern matches a certain portion of the subject, and in -addition, further substrings from the subject may be picked out by parts of the -pattern. Following the usage in Jeffrey Friedl's book, this is called -"capturing" in what follows, and the phrase "capturing subpattern" is used for -a fragment of a pattern that picks out a substring. PCRE supports several other -kinds of parenthesized subpattern that do not cause substrings to be captured. -

-

-Captured substrings are returned to the caller via a vector of integers whose -address is passed in ovector. The number of elements in the vector is -passed in ovecsize, which must be a non-negative number. Note: this -argument is NOT the size of ovector in bytes. -

-

-The first two-thirds of the vector is used to pass back captured substrings, -each substring using a pair of integers. The remaining third of the vector is -used as workspace by pcre_exec() while matching capturing subpatterns, -and is not available for passing back information. The number passed in -ovecsize should always be a multiple of three. If it is not, it is -rounded down. -

-

-When a match is successful, information about captured substrings is returned -in pairs of integers, starting at the beginning of ovector, and -continuing up to two-thirds of its length at the most. The first element of -each pair is set to the offset of the first character in a substring, and the -second is set to the offset of the first character after the end of a -substring. These values are always data unit offsets, even in UTF mode. They -are byte offsets in the 8-bit library, 16-bit data item offsets in the 16-bit -library, and 32-bit data item offsets in the 32-bit library. Note: they -are not character counts. -

-

-The first pair of integers, ovector[0] and ovector[1], identify the -portion of the subject string matched by the entire pattern. The next pair is -used for the first capturing subpattern, and so on. The value returned by -pcre_exec() is one more than the highest numbered pair that has been set. -For example, if two substrings have been captured, the returned value is 3. If -there are no capturing subpatterns, the return value from a successful match is -1, indicating that just the first pair of offsets has been set. -

-

-If a capturing subpattern is matched repeatedly, it is the last portion of the -string that it matched that is returned. -

-

-If the vector is too small to hold all the captured substring offsets, it is -used as far as possible (up to two-thirds of its length), and the function -returns a value of zero. If neither the actual string matched nor any captured -substrings are of interest, pcre_exec() may be called with ovector -passed as NULL and ovecsize as zero. However, if the pattern contains -back references and the ovector is not big enough to remember the related -substrings, PCRE has to get additional memory for use during matching. Thus it -is usually advisable to supply an ovector of reasonable size. -

-

-There are some cases where zero is returned (indicating vector overflow) when -in fact the vector is exactly the right size for the final match. For example, -consider the pattern -

-  (a)(?:(b)c|bd)
-
-If a vector of 6 elements (allowing for only 1 captured substring) is given -with subject string "abd", pcre_exec() will try to set the second -captured string, thereby recording a vector overflow, before failing to match -"c" and backing up to try the second alternative. The zero return, however, -does correctly indicate that the maximum number of slots (namely 2) have been -filled. In similar cases where there is temporary overflow, but the final -number of used slots is actually less than the maximum, a non-zero value is -returned. -

-

-The pcre_fullinfo() function can be used to find out how many capturing -subpatterns there are in a compiled pattern. The smallest size for -ovector that will allow for n captured substrings, in addition to -the offsets of the substring matched by the whole pattern, is (n+1)*3. -

-

-It is possible for capturing subpattern number n+1 to match some part of -the subject when subpattern n has not been used at all. For example, if -the string "abc" is matched against the pattern (a|(z))(bc) the return from the -function is 4, and subpatterns 1 and 3 are matched, but 2 is not. When this -happens, both values in the offset pairs corresponding to unused subpatterns -are set to -1. -

-

-Offset values that correspond to unused subpatterns at the end of the -expression are also set to -1. For example, if the string "abc" is matched -against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not matched. The -return from the function is 2, because the highest used capturing subpattern -number is 1, and the offsets for for the second and third capturing subpatterns -(assuming the vector is large enough, of course) are set to -1. -

-

-Note: Elements in the first two-thirds of ovector that do not -correspond to capturing parentheses in the pattern are never changed. That is, -if a pattern contains n capturing parentheses, no more than -ovector[0] to ovector[2n+1] are set by pcre_exec(). The other -elements (in the first two-thirds) retain whatever values they previously had. -

-

-Some convenience functions are provided for extracting the captured substrings -as separate strings. These are described below. -

-
-Error return values from pcre_exec() -
-

-If pcre_exec() fails, it returns a negative number. The following are -defined in the header file: -

-  PCRE_ERROR_NOMATCH        (-1)
-
-The subject string did not match the pattern. -
-  PCRE_ERROR_NULL           (-2)
-
-Either code or subject was passed as NULL, or ovector was -NULL and ovecsize was not zero. -
-  PCRE_ERROR_BADOPTION      (-3)
-
-An unrecognized bit was set in the options argument. -
-  PCRE_ERROR_BADMAGIC       (-4)
-
-PCRE stores a 4-byte "magic number" at the start of the compiled code, to catch -the case when it is passed a junk pointer and to detect when a pattern that was -compiled in an environment of one endianness is run in an environment with the -other endianness. This is the error that PCRE gives when the magic number is -not present. -
-  PCRE_ERROR_UNKNOWN_OPCODE (-5)
-
-While running the pattern match, an unknown item was encountered in the -compiled pattern. This error could be caused by a bug in PCRE or by overwriting -of the compiled pattern. -
-  PCRE_ERROR_NOMEMORY       (-6)
-
-If a pattern contains back references, but the ovector that is passed to -pcre_exec() is not big enough to remember the referenced substrings, PCRE -gets a block of memory at the start of matching to use for this purpose. If the -call via pcre_malloc() fails, this error is given. The memory is -automatically freed at the end of matching. -

-

-This error is also given if pcre_stack_malloc() fails in -pcre_exec(). This can happen only when PCRE has been compiled with ---disable-stack-for-recursion. -

-  PCRE_ERROR_NOSUBSTRING    (-7)
-
-This error is used by the pcre_copy_substring(), -pcre_get_substring(), and pcre_get_substring_list() functions (see -below). It is never returned by pcre_exec(). -
-  PCRE_ERROR_MATCHLIMIT     (-8)
-
-The backtracking limit, as specified by the match_limit field in a -pcre_extra structure (or defaulted) was reached. See the description -above. -
-  PCRE_ERROR_CALLOUT        (-9)
-
-This error is never generated by pcre_exec() itself. It is provided for -use by callout functions that want to yield a distinctive error code. See the -pcrecallout -documentation for details. -
-  PCRE_ERROR_BADUTF8        (-10)
-
-A string that contains an invalid UTF-8 byte sequence was passed as a subject, -and the PCRE_NO_UTF8_CHECK option was not set. If the size of the output vector -(ovecsize) is at least 2, the byte offset to the start of the the invalid -UTF-8 character is placed in the first element, and a reason code is placed in -the second element. The reason codes are listed in the -following section. -For backward compatibility, if PCRE_PARTIAL_HARD is set and the problem is a -truncated UTF-8 character at the end of the subject (reason codes 1 to 5), -PCRE_ERROR_SHORTUTF8 is returned instead of PCRE_ERROR_BADUTF8. -
-  PCRE_ERROR_BADUTF8_OFFSET (-11)
-
-The UTF-8 byte sequence that was passed as a subject was checked and found to -be valid (the PCRE_NO_UTF8_CHECK option was not set), but the value of -startoffset did not point to the beginning of a UTF-8 character or the -end of the subject. -
-  PCRE_ERROR_PARTIAL        (-12)
-
-The subject string did not match, but it did match partially. See the -pcrepartial -documentation for details of partial matching. -
-  PCRE_ERROR_BADPARTIAL     (-13)
-
-This code is no longer in use. It was formerly returned when the PCRE_PARTIAL -option was used with a compiled pattern containing items that were not -supported for partial matching. From release 8.00 onwards, there are no -restrictions on partial matching. -
-  PCRE_ERROR_INTERNAL       (-14)
-
-An unexpected internal error has occurred. This error could be caused by a bug -in PCRE or by overwriting of the compiled pattern. -
-  PCRE_ERROR_BADCOUNT       (-15)
-
-This error is given if the value of the ovecsize argument is negative. -
-  PCRE_ERROR_RECURSIONLIMIT (-21)
-
-The internal recursion limit, as specified by the match_limit_recursion -field in a pcre_extra structure (or defaulted) was reached. See the -description above. -
-  PCRE_ERROR_BADNEWLINE     (-23)
-
-An invalid combination of PCRE_NEWLINE_xxx options was given. -
-  PCRE_ERROR_BADOFFSET      (-24)
-
-The value of startoffset was negative or greater than the length of the -subject, that is, the value in length. -
-  PCRE_ERROR_SHORTUTF8      (-25)
-
-This error is returned instead of PCRE_ERROR_BADUTF8 when the subject string -ends with a truncated UTF-8 character and the PCRE_PARTIAL_HARD option is set. -Information about the failure is returned as for PCRE_ERROR_BADUTF8. It is in -fact sufficient to detect this case, but this special error code for -PCRE_PARTIAL_HARD precedes the implementation of returned information; it is -retained for backwards compatibility. -
-  PCRE_ERROR_RECURSELOOP    (-26)
-
-This error is returned when pcre_exec() detects a recursion loop within -the pattern. Specifically, it means that either the whole pattern or a -subpattern has been called recursively for the second time at the same position -in the subject string. Some simple patterns that might do this are detected and -faulted at compile time, but more complicated cases, in particular mutual -recursions between two different subpatterns, cannot be detected until run -time. -
-  PCRE_ERROR_JIT_STACKLIMIT (-27)
-
-This error is returned when a pattern that was successfully studied using a -JIT compile option is being matched, but the memory available for the -just-in-time processing stack is not large enough. See the -pcrejit -documentation for more details. -
-  PCRE_ERROR_BADMODE        (-28)
-
-This error is given if a pattern that was compiled by the 8-bit library is -passed to a 16-bit or 32-bit library function, or vice versa. -
-  PCRE_ERROR_BADENDIANNESS  (-29)
-
-This error is given if a pattern that was compiled and saved is reloaded on a -host with different endianness. The utility function -pcre_pattern_to_host_byte_order() can be used to convert such a pattern -so that it runs on the new host. -
-  PCRE_ERROR_JIT_BADOPTION
-
-This error is returned when a pattern that was successfully studied using a JIT -compile option is being matched, but the matching mode (partial or complete -match) does not correspond to any JIT compilation mode. When the JIT fast path -function is used, this error may be also given for invalid options. See the -pcrejit -documentation for more details. -
-  PCRE_ERROR_BADLENGTH      (-32)
-
-This error is given if pcre_exec() is called with a negative value for -the length argument. -

-

-Error numbers -16 to -20, -22, and 30 are not used by pcre_exec(). -

-
-Reason codes for invalid UTF-8 strings -
-

-This section applies only to the 8-bit library. The corresponding information -for the 16-bit and 32-bit libraries is given in the -pcre16 -and -pcre32 -pages. -

-

-When pcre_exec() returns either PCRE_ERROR_BADUTF8 or -PCRE_ERROR_SHORTUTF8, and the size of the output vector (ovecsize) is at -least 2, the offset of the start of the invalid UTF-8 character is placed in -the first output vector element (ovector[0]) and a reason code is placed -in the second element (ovector[1]). The reason codes are given names in -the pcre.h header file: -

-  PCRE_UTF8_ERR1
-  PCRE_UTF8_ERR2
-  PCRE_UTF8_ERR3
-  PCRE_UTF8_ERR4
-  PCRE_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 (originally defined by RFC 2279) -allows for up to 6 bytes, and this is checked first; hence the possibility of -4 or 5 missing bytes. -
-  PCRE_UTF8_ERR6
-  PCRE_UTF8_ERR7
-  PCRE_UTF8_ERR8
-  PCRE_UTF8_ERR9
-  PCRE_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 most -significant bit is 0, or the next bit is 1). -
-  PCRE_UTF8_ERR11
-  PCRE_UTF8_ERR12
-
-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. -
-  PCRE_UTF8_ERR13
-
-A 4-byte character has a value greater than 0x10fff; these code points are -excluded by RFC 3629. -
-  PCRE_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 so are excluded -from UTF-8. -
-  PCRE_UTF8_ERR15
-  PCRE_UTF8_ERR16
-  PCRE_UTF8_ERR17
-  PCRE_UTF8_ERR18
-  PCRE_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 correct coding uses just -one byte. -
-  PCRE_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 second is 0). Such a -byte can only validly occur as the second or subsequent byte of a multi-byte -character. -
-  PCRE_UTF8_ERR21
-
-The first byte of a character has the value 0xfe or 0xff. These values can -never occur in a valid UTF-8 string. -
-  PCRE_UTF8_ERR22
-
-This error code was formerly used when the presence of a so-called -"non-character" caused an error. Unicode corrigendum #9 makes it clear that -such characters should not cause a string to be rejected, and so this code is -no longer in use and is never returned. -

-
EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
-

-int pcre_copy_substring(const char *subject, int *ovector, - int stringcount, int stringnumber, char *buffer, - int buffersize); -
-
-int pcre_get_substring(const char *subject, int *ovector, - int stringcount, int stringnumber, - const char **stringptr); -
-
-int pcre_get_substring_list(const char *subject, - int *ovector, int stringcount, const char ***listptr); -

-

-Captured substrings can be accessed directly by using the offsets returned by -pcre_exec() in ovector. For convenience, the functions -pcre_copy_substring(), pcre_get_substring(), and -pcre_get_substring_list() are provided for extracting captured substrings -as new, separate, zero-terminated strings. These functions identify substrings -by number. The next section describes functions for extracting named -substrings. -

-

-A substring that contains a binary zero is correctly extracted and has a -further zero added on the end, but the result is not, of course, a C string. -However, you can process such a string by referring to the length that is -returned by pcre_copy_substring() and pcre_get_substring(). -Unfortunately, the interface to pcre_get_substring_list() is not adequate -for handling strings containing binary zeros, because the end of the final -string is not independently indicated. -

-

-The first three arguments are the same for all three of these functions: -subject is the subject string that has just been successfully matched, -ovector is a pointer to the vector of integer offsets that was passed to -pcre_exec(), and stringcount is the number of substrings that were -captured by the match, including the substring that matched the entire regular -expression. This is the value returned by pcre_exec() if it is greater -than zero. If pcre_exec() returned zero, indicating that it ran out of -space in ovector, the value passed as stringcount should be the -number of elements in the vector divided by three. -

-

-The functions pcre_copy_substring() and pcre_get_substring() -extract a single substring, whose number is given as stringnumber. A -value of zero extracts the substring that matched the entire pattern, whereas -higher values extract the captured substrings. For pcre_copy_substring(), -the string is placed in buffer, whose length is given by -buffersize, while for pcre_get_substring() a new block of memory is -obtained via pcre_malloc, and its address is returned via -stringptr. The yield of the function is the length of the string, not -including the terminating zero, or one of these error codes: -

-  PCRE_ERROR_NOMEMORY       (-6)
-
-The buffer was too small for pcre_copy_substring(), or the attempt to get -memory failed for pcre_get_substring(). -
-  PCRE_ERROR_NOSUBSTRING    (-7)
-
-There is no substring whose number is stringnumber. -

-

-The pcre_get_substring_list() function extracts all available substrings -and builds a list of pointers to them. All this is done in a single block of -memory that is obtained via pcre_malloc. The address of the memory block -is returned via listptr, which is also the start of the list of string -pointers. The end of the list is marked by a NULL pointer. The yield of the -function is zero if all went well, or the error code -

-  PCRE_ERROR_NOMEMORY       (-6)
-
-if the attempt to get the memory block failed. -

-

-When any of these functions encounter a substring that is unset, which can -happen when capturing subpattern number n+1 matches some part of the -subject, but subpattern n has not been used at all, they return an empty -string. This can be distinguished from a genuine zero-length substring by -inspecting the appropriate offset in ovector, which is negative for unset -substrings. -

-

-The two convenience functions pcre_free_substring() and -pcre_free_substring_list() can be used to free the memory returned by -a previous call of pcre_get_substring() or -pcre_get_substring_list(), respectively. They do nothing more than call -the function pointed to by pcre_free, which of course could be called -directly from a C program. However, PCRE is used in some situations where it is -linked via a special interface to another programming language that cannot use -pcre_free directly; it is for these cases that the functions are -provided. -

-
EXTRACTING CAPTURED SUBSTRINGS BY NAME
-

-int pcre_get_stringnumber(const pcre *code, - const char *name); -
-
-int pcre_copy_named_substring(const pcre *code, - const char *subject, int *ovector, - int stringcount, const char *stringname, - char *buffer, int buffersize); -
-
-int pcre_get_named_substring(const pcre *code, - const char *subject, int *ovector, - int stringcount, const char *stringname, - const char **stringptr); -

-

-To extract a substring by name, you first have to find associated number. -For example, for this pattern -

-  (a+)b(?<xxx>\d+)...
-
-the number of the subpattern called "xxx" is 2. If the name is known to be -unique (PCRE_DUPNAMES was not set), you can find the number from the name by -calling pcre_get_stringnumber(). The first argument is the compiled -pattern, and the second is the name. The yield of the function is the -subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if there is no subpattern of -that name. -

-

-Given the number, you can extract the substring directly, or use one of the -functions described in the previous section. For convenience, there are also -two functions that do the whole job. -

-

-Most of the arguments of pcre_copy_named_substring() and -pcre_get_named_substring() are the same as those for the similarly named -functions that extract by number. As these are described in the previous -section, they are not re-described here. There are just two differences: -

-

-First, instead of a substring number, a substring name is given. Second, there -is an extra argument, given at the start, which is a pointer to the compiled -pattern. This is needed in order to gain access to the name-to-number -translation table. -

-

-These functions call pcre_get_stringnumber(), and if it succeeds, they -then call pcre_copy_substring() or pcre_get_substring(), as -appropriate. NOTE: If PCRE_DUPNAMES is set and there are duplicate names, -the behaviour may not be what you want (see the next section). -

-

-Warning: If the pattern uses the (?| feature to set up multiple -subpatterns with the same number, as described in the -section on duplicate subpattern numbers -in the -pcrepattern -page, you cannot use names to distinguish the different subpatterns, because -names are not included in the compiled code. The matching process uses only -numbers. For this reason, the use of different names for subpatterns of the -same number causes an error at compile time. -

-
DUPLICATE SUBPATTERN NAMES
-

-int pcre_get_stringtable_entries(const pcre *code, - const char *name, char **first, char **last); -

-

-When a pattern is compiled with the PCRE_DUPNAMES option, names for subpatterns -are not required to be unique. (Duplicate names are always allowed for -subpatterns with the same number, created by using the (?| feature. Indeed, if -such subpatterns are named, they are required to use the same names.) -

-

-Normally, patterns with duplicate names are such that in any one match, only -one of the named subpatterns participates. An example is shown in the -pcrepattern -documentation. -

-

-When duplicates are present, pcre_copy_named_substring() and -pcre_get_named_substring() return the first substring corresponding to -the given name that is set. If none are set, PCRE_ERROR_NOSUBSTRING (-7) is -returned; no data is returned. The pcre_get_stringnumber() function -returns one of the numbers that are associated with the name, but it is not -defined which it is. -

-

-If you want to get full details of all captured substrings for a given name, -you must use the pcre_get_stringtable_entries() function. The first -argument is the compiled pattern, and the second is the name. The third and -fourth are pointers to variables which are updated by the function. After it -has run, they point to the first and last entries in the name-to-number table -for the given name. The function itself returns the length of each entry, or -PCRE_ERROR_NOSUBSTRING (-7) if there are none. The format of the table is -described above in the section entitled Information about a pattern -above. -Given all the relevant entries for the name, you can extract each of their -numbers, and hence the captured data, if any. -

-
FINDING ALL POSSIBLE MATCHES
-

-The traditional matching function uses a similar algorithm to Perl, which stops -when it finds the first match, starting at a given point in the subject. If you -want to find all possible matches, or the longest possible match, consider -using the alternative matching function (see below) instead. If you cannot use -the alternative function, but still need to find all possible matches, you -can kludge it up by making use of the callout facility, which is described in -the -pcrecallout -documentation. -

-

-What you have to do is to insert a callout right at the end of the pattern. -When your callout function is called, extract and save the current matched -substring. Then return 1, which forces pcre_exec() to backtrack and try -other alternatives. Ultimately, when it runs out of matches, pcre_exec() -will yield PCRE_ERROR_NOMATCH. -

-
OBTAINING AN ESTIMATE OF STACK USAGE
-

-Matching certain patterns using pcre_exec() can use a lot of process -stack, which in certain environments can be rather limited in size. Some users -find it helpful to have an estimate of the amount of stack that is used by -pcre_exec(), to help them set recursion limits, as described in the -pcrestack -documentation. The estimate that is output by pcretest when called with -the -m and -C options is obtained by calling pcre_exec with -the values NULL, NULL, NULL, -999, and -999 for its first five arguments. -

-

-Normally, if its first argument is NULL, pcre_exec() immediately returns -the negative error code PCRE_ERROR_NULL, but with this special combination of -arguments, it returns instead a negative number whose absolute value is the -approximate stack frame size in bytes. (A negative number is used so that it is -clear that no match has happened.) The value is approximate because in some -cases, recursive calls to pcre_exec() occur when there are one or two -additional variables on the stack. -

-

-If PCRE has been compiled to use the heap instead of the stack for recursion, -the value returned is the size of each block that is obtained from the heap. -

-
MATCHING A PATTERN: THE ALTERNATIVE FUNCTION
-

-int pcre_dfa_exec(const pcre *code, const pcre_extra *extra, - const char *subject, int length, int startoffset, - int options, int *ovector, int ovecsize, - int *workspace, int wscount); -

-

-The function pcre_dfa_exec() is called to match a subject string against -a compiled pattern, using a matching algorithm that scans the subject string -just once, and does not backtrack. This has different characteristics to the -normal algorithm, and is not compatible with Perl. Some of the features of PCRE -patterns are not supported. Nevertheless, there are times when this kind of -matching can be useful. For a discussion of the two matching algorithms, and a -list of features that pcre_dfa_exec() does not support, see the -pcrematching -documentation. -

-

-The arguments for the pcre_dfa_exec() function are the same as for -pcre_exec(), plus two extras. The ovector argument is used in a -different way, and this is described below. The other common arguments are used -in the same way as for pcre_exec(), so their description is not repeated -here. -

-

-The two additional arguments provide workspace for the function. The workspace -vector should contain at least 20 elements. It is used for keeping track of -multiple paths through the pattern tree. More workspace will be needed for -patterns and subjects where there are a lot of potential matches. -

-

-Here is an example of a simple call to pcre_dfa_exec(): -

-  int rc;
-  int ovector[10];
-  int wspace[20];
-  rc = pcre_dfa_exec(
-    re,             /* result of pcre_compile() */
-    NULL,           /* we didn't study the pattern */
-    "some string",  /* the subject string */
-    11,             /* the length of the subject string */
-    0,              /* start at offset 0 in the subject */
-    0,              /* default options */
-    ovector,        /* vector of integers for substring information */
-    10,             /* number of elements (NOT size in bytes) */
-    wspace,         /* working space vector */
-    20);            /* number of elements (NOT size in bytes) */
-
-

-
-Option bits for pcre_dfa_exec() -
-

-The unused bits of the options argument for pcre_dfa_exec() must be -zero. The only bits that may be set are PCRE_ANCHORED, PCRE_NEWLINE_xxx, -PCRE_NOTBOL, PCRE_NOTEOL, PCRE_NOTEMPTY, PCRE_NOTEMPTY_ATSTART, -PCRE_NO_UTF8_CHECK, PCRE_BSR_ANYCRLF, PCRE_BSR_UNICODE, PCRE_NO_START_OPTIMIZE, -PCRE_PARTIAL_HARD, PCRE_PARTIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. -All but the last four of these are exactly the same as for pcre_exec(), -so their description is not repeated here. -

-  PCRE_PARTIAL_HARD
-  PCRE_PARTIAL_SOFT
-
-These have the same general effect as they do for pcre_exec(), but the -details are slightly different. When PCRE_PARTIAL_HARD is set for -pcre_dfa_exec(), it returns PCRE_ERROR_PARTIAL if the end of the subject -is reached and there is still at least one matching possibility that requires -additional characters. This happens even if some complete matches have also -been found. When PCRE_PARTIAL_SOFT is set, the return code PCRE_ERROR_NOMATCH -is converted into PCRE_ERROR_PARTIAL if the end of the subject is reached, -there have been no complete matches, but there is still at least one matching -possibility. The portion of the string that was inspected when the longest -partial match was found is set as the first matching string in both cases. -There is a more detailed discussion of partial and multi-segment matching, with -examples, in the -pcrepartial -documentation. -
-  PCRE_DFA_SHORTEST
-
-Setting the PCRE_DFA_SHORTEST option causes the matching algorithm to stop as -soon as it has found one match. Because of the way the alternative algorithm -works, this is necessarily the shortest possible match at the first possible -matching point in the subject string. -
-  PCRE_DFA_RESTART
-
-When pcre_dfa_exec() returns a partial match, it is possible to call it -again, with additional subject characters, and have it continue with the same -match. The PCRE_DFA_RESTART option requests this action; when it is set, the -workspace and wscount options must reference the same vector as -before because data about the match so far is left in them after a partial -match. There is more discussion of this facility in the -pcrepartial -documentation. -

-
-Successful returns from pcre_dfa_exec() -
-

-When pcre_dfa_exec() succeeds, it may have matched more than one -substring in the subject. Note, however, that all the matches from one run of -the function start at the same point in the subject. The shorter matches are -all initial substrings of the longer matches. For example, if the pattern -

-  <.*>
-
-is matched against the string -
-  This is <something> <something else> <something further> no more
-
-the three matched strings are -
-  <something>
-  <something> <something else>
-  <something> <something else> <something further>
-
-On success, the yield of the function is a number greater than zero, which is -the number of matched substrings. The substrings themselves are returned in -ovector. Each string uses two elements; the first is the offset to the -start, and the second is the offset to the end. In fact, all the strings have -the same start offset. (Space could have been saved by giving this only once, -but it was decided to retain some compatibility with the way pcre_exec() -returns data, even though the meaning of the strings is different.) -

-

-The strings are returned in reverse order of length; that is, the longest -matching string is given first. If there were too many matches to fit into -ovector, the yield of the function is zero, and the vector is filled with -the longest matches. Unlike pcre_exec(), pcre_dfa_exec() can use -the entire ovector for returning matched strings. -

-

-NOTE: PCRE's "auto-possessification" optimization usually applies to character -repeats at the end of a pattern (as well as internally). For example, the -pattern "a\d+" is compiled as if it were "a\d++" because there is no point -even considering the possibility of backtracking into the repeated digits. For -DFA matching, this means that only one possible match is found. If you really -do want multiple matches in such cases, either use an ungreedy repeat -("a\d+?") or set the PCRE_NO_AUTO_POSSESS option when compiling. -

-
-Error returns from pcre_dfa_exec() -
-

-The pcre_dfa_exec() function returns a negative number when it fails. -Many of the errors are the same as for pcre_exec(), and these are -described -above. -There are in addition the following errors that are specific to -pcre_dfa_exec(): -

-  PCRE_ERROR_DFA_UITEM      (-16)
-
-This return is given if pcre_dfa_exec() encounters an item in the pattern -that it does not support, for instance, the use of \C or a back reference. -
-  PCRE_ERROR_DFA_UCOND      (-17)
-
-This return is given if pcre_dfa_exec() encounters a condition item that -uses a back reference for the condition, or a test for recursion in a specific -group. These are not supported. -
-  PCRE_ERROR_DFA_UMLIMIT    (-18)
-
-This return is given if pcre_dfa_exec() is called with an extra -block that contains a setting of the match_limit or -match_limit_recursion fields. This is not supported (these fields are -meaningless for DFA matching). -
-  PCRE_ERROR_DFA_WSSIZE     (-19)
-
-This return is given if pcre_dfa_exec() runs out of space in the -workspace vector. -
-  PCRE_ERROR_DFA_RECURSE    (-20)
-
-When a recursive subpattern is processed, the matching function calls itself -recursively, using private vectors for ovector and workspace. This -error is given if the output vector is not large enough. This should be -extremely rare, as a vector of size 1000 is used. -
-  PCRE_ERROR_DFA_BADRESTART (-30)
-
-When pcre_dfa_exec() is called with the PCRE_DFA_RESTART option, -some plausibility checks are made on the contents of the workspace, which -should contain data about the previous partial match. If any of these checks -fail, this error is given. -

-
SEE ALSO
-

-pcre16(3), pcre32(3), pcrebuild(3), pcrecallout(3), -pcrecpp(3)(3), pcrematching(3), pcrepartial(3), -pcreposix(3), pcreprecompile(3), pcresample(3), -pcrestack(3). -

-
AUTHOR
-

-Philip Hazel -
-University Computing Service -
-Cambridge CB2 3QH, England. -
-

-
REVISION
-

-Last updated: 18 December 2015 -
-Copyright © 1997-2015 University of Cambridge. -
-

-Return to the PCRE index page. -

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