/[pcre]/code/trunk/doc/pcre.txt
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revision 535 by ph10, Thu Jun 3 19:18:24 2010 UTC revision 545 by ph10, Wed Jun 16 10:51:15 2010 UTC
# Line 2122  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2122  MATCHING A PATTERN: THE TRADITIONAL FUNC
2122    
2123         There  are a number of optimizations that pcre_exec() uses at the start         There  are a number of optimizations that pcre_exec() uses at the start
2124         of a match, in order to speed up the process. For  example,  if  it  is         of a match, in order to speed up the process. For  example,  if  it  is
2125         known  that  a  match must start with a specific character, it searches         known that an unanchored match must start with a specific character, it
2126         the subject for that character, and fails immediately if it cannot find         searches the subject for that character, and fails  immediately  if  it
2127         it,  without actually running the main matching function. When callouts         cannot  find  it,  without actually running the main matching function.
2128         are in use, these optimizations can cause  them  to  be  skipped.  This         This means that a special item such as (*COMMIT) at the start of a pat-
2129         option  disables  the  "start-up" optimizations, causing performance to         tern  is  not  considered until after a suitable starting point for the
2130         suffer, but ensuring that the callouts do occur.         match has been found. When callouts are in use, these "start-up"  opti-
2131           mizations can cause them to be skipped if the pattern is never actually
2132           used. The PCRE_NO_START_OPTIMIZE option disables the start-up optimiza-
2133           tions, causing performance to suffer, but ensuring that the callouts do
2134           occur, and that items such as (*COMMIT) are considered at every  possi-
2135           ble starting position in the subject string.
2136    
2137           PCRE_NO_UTF8_CHECK           PCRE_NO_UTF8_CHECK
2138    
2139         When PCRE_UTF8 is set at compile time, the validity of the subject as a         When PCRE_UTF8 is set at compile time, the validity of the subject as a
2140         UTF-8  string is automatically checked when pcre_exec() is subsequently         UTF-8 string is automatically checked when pcre_exec() is  subsequently
2141         called.  The value of startoffset is also checked  to  ensure  that  it         called.   The  value  of  startoffset is also checked to ensure that it
2142         points  to  the start of a UTF-8 character. There is a discussion about         points to the start of a UTF-8 character. There is a  discussion  about
2143         the validity of UTF-8 strings in the section on UTF-8  support  in  the         the  validity  of  UTF-8 strings in the section on UTF-8 support in the
2144         main  pcre  page.  If  an  invalid  UTF-8  sequence  of bytes is found,         main pcre page. If  an  invalid  UTF-8  sequence  of  bytes  is  found,
2145         pcre_exec() returns the error PCRE_ERROR_BADUTF8. If  startoffset  con-         pcre_exec()  returns  the error PCRE_ERROR_BADUTF8. If startoffset con-
2146         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.         tains an invalid value, PCRE_ERROR_BADUTF8_OFFSET is returned.
2147    
2148         If  you  already  know that your subject is valid, and you want to skip         If you already know that your subject is valid, and you  want  to  skip
2149         these   checks   for   performance   reasons,   you   can    set    the         these    checks    for   performance   reasons,   you   can   set   the
2150         PCRE_NO_UTF8_CHECK  option  when calling pcre_exec(). You might want to         PCRE_NO_UTF8_CHECK option when calling pcre_exec(). You might  want  to
2151         do this for the second and subsequent calls to pcre_exec() if  you  are         do  this  for the second and subsequent calls to pcre_exec() if you are
2152         making  repeated  calls  to  find  all  the matches in a single subject         making repeated calls to find all  the  matches  in  a  single  subject
2153         string. However, you should be  sure  that  the  value  of  startoffset         string.  However,  you  should  be  sure  that the value of startoffset
2154         points  to  the  start of a UTF-8 character. When PCRE_NO_UTF8_CHECK is         points to the start of a UTF-8 character.  When  PCRE_NO_UTF8_CHECK  is
2155         set, the effect of passing an invalid UTF-8 string as a subject,  or  a         set,  the  effect of passing an invalid UTF-8 string as a subject, or a
2156         value  of startoffset that does not point to the start of a UTF-8 char-         value of startoffset that does not point to the start of a UTF-8  char-
2157         acter, is undefined. Your program may crash.         acter, is undefined. Your program may crash.
2158    
2159           PCRE_PARTIAL_HARD           PCRE_PARTIAL_HARD
2160           PCRE_PARTIAL_SOFT           PCRE_PARTIAL_SOFT
2161    
2162         These options turn on the partial matching feature. For backwards  com-         These  options turn on the partial matching feature. For backwards com-
2163         patibility,  PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A partial         patibility, PCRE_PARTIAL is a synonym for PCRE_PARTIAL_SOFT. A  partial
2164         match occurs if the end of the subject string is reached  successfully,         match  occurs if the end of the subject string is reached successfully,
2165         but  there  are not enough subject characters to complete the match. If         but there are not enough subject characters to complete the  match.  If
2166         this happens when PCRE_PARTIAL_HARD  is  set,  pcre_exec()  immediately         this  happens  when  PCRE_PARTIAL_HARD  is set, pcre_exec() immediately
2167         returns  PCRE_ERROR_PARTIAL.  Otherwise,  if  PCRE_PARTIAL_SOFT is set,         returns PCRE_ERROR_PARTIAL. Otherwise,  if  PCRE_PARTIAL_SOFT  is  set,
2168         matching continues by testing any other alternatives. Only if they  all         matching  continues by testing any other alternatives. Only if they all
2169         fail  is  PCRE_ERROR_PARTIAL  returned (instead of PCRE_ERROR_NOMATCH).         fail is PCRE_ERROR_PARTIAL returned  (instead  of  PCRE_ERROR_NOMATCH).
2170         The portion of the string that was inspected when the partial match was         The portion of the string that was inspected when the partial match was
2171         found  is  set  as  the first matching string. There is a more detailed         found is set as the first matching string. There  is  a  more  detailed
2172         discussion in the pcrepartial documentation.         discussion in the pcrepartial documentation.
2173    
2174     The string to be matched by pcre_exec()     The string to be matched by pcre_exec()
2175    
2176         The subject string is passed to pcre_exec() as a pointer in subject,  a         The  subject string is passed to pcre_exec() as a pointer in subject, a
2177         length (in bytes) in length, and a starting byte offset in startoffset.         length (in bytes) in length, and a starting byte offset in startoffset.
2178         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-         In UTF-8 mode, the byte offset must point to the start of a UTF-8 char-
2179         acter.  Unlike  the pattern string, the subject may contain binary zero         acter. Unlike the pattern string, the subject may contain  binary  zero
2180         bytes. When the starting offset is zero, the search for a match  starts         bytes.  When the starting offset is zero, the search for a match starts
2181         at  the  beginning  of  the subject, and this is by far the most common         at the beginning of the subject, and this is by  far  the  most  common
2182         case.         case.
2183    
2184         A non-zero starting offset is useful when searching for  another  match         A  non-zero  starting offset is useful when searching for another match
2185         in  the same subject by calling pcre_exec() again after a previous suc-         in the same subject by calling pcre_exec() again after a previous  suc-
2186         cess.  Setting startoffset differs from just passing over  a  shortened         cess.   Setting  startoffset differs from just passing over a shortened
2187         string  and  setting  PCRE_NOTBOL  in the case of a pattern that begins         string and setting PCRE_NOTBOL in the case of  a  pattern  that  begins
2188         with any kind of lookbehind. For example, consider the pattern         with any kind of lookbehind. For example, consider the pattern
2189    
2190           \Biss\B           \Biss\B
2191    
2192         which finds occurrences of "iss" in the middle of  words.  (\B  matches         which  finds  occurrences  of "iss" in the middle of words. (\B matches
2193         only  if  the  current position in the subject is not a word boundary.)         only if the current position in the subject is not  a  word  boundary.)
2194         When applied to the string "Mississipi" the first call  to  pcre_exec()         When  applied  to the string "Mississipi" the first call to pcre_exec()
2195         finds  the  first  occurrence. If pcre_exec() is called again with just         finds the first occurrence. If pcre_exec() is called  again  with  just
2196         the remainder of the subject,  namely  "issipi",  it  does  not  match,         the  remainder  of  the  subject,  namely  "issipi", it does not match,
2197         because \B is always false at the start of the subject, which is deemed         because \B is always false at the start of the subject, which is deemed
2198         to be a word boundary. However, if pcre_exec()  is  passed  the  entire         to  be  a  word  boundary. However, if pcre_exec() is passed the entire
2199         string again, but with startoffset set to 4, it finds the second occur-         string again, but with startoffset set to 4, it finds the second occur-
2200         rence of "iss" because it is able to look behind the starting point  to         rence  of "iss" because it is able to look behind the starting point to
2201         discover that it is preceded by a letter.         discover that it is preceded by a letter.
2202    
2203         If  a  non-zero starting offset is passed when the pattern is anchored,         If a non-zero starting offset is passed when the pattern  is  anchored,
2204         one attempt to match at the given offset is made. This can only succeed         one attempt to match at the given offset is made. This can only succeed
2205         if  the  pattern  does  not require the match to be at the start of the         if the pattern does not require the match to be at  the  start  of  the
2206         subject.         subject.
2207    
2208     How pcre_exec() returns captured substrings     How pcre_exec() returns captured substrings
2209    
2210         In general, a pattern matches a certain portion of the subject, and  in         In  general, a pattern matches a certain portion of the subject, and in
2211         addition,  further  substrings  from  the  subject may be picked out by         addition, further substrings from the subject  may  be  picked  out  by
2212         parts of the pattern. Following the usage  in  Jeffrey  Friedl's  book,         parts  of  the  pattern.  Following the usage in Jeffrey Friedl's book,
2213         this  is  called "capturing" in what follows, and the phrase "capturing         this is called "capturing" in what follows, and the  phrase  "capturing
2214         subpattern" is used for a fragment of a pattern that picks out  a  sub-         subpattern"  is  used for a fragment of a pattern that picks out a sub-
2215         string.  PCRE  supports several other kinds of parenthesized subpattern         string. PCRE supports several other kinds of  parenthesized  subpattern
2216         that do not cause substrings to be captured.         that do not cause substrings to be captured.
2217    
2218         Captured substrings are returned to the caller via a vector of integers         Captured substrings are returned to the caller via a vector of integers
2219         whose  address is passed in ovector. The number of elements in the vec-         whose address is passed in ovector. The number of elements in the  vec-
2220         tor is passed in ovecsize, which must be a non-negative  number.  Note:         tor  is  passed in ovecsize, which must be a non-negative number. Note:
2221         this argument is NOT the size of ovector in bytes.         this argument is NOT the size of ovector in bytes.
2222    
2223         The  first  two-thirds of the vector is used to pass back captured sub-         The first two-thirds of the vector is used to pass back  captured  sub-
2224         strings, each substring using a pair of integers. The  remaining  third         strings,  each  substring using a pair of integers. The remaining third
2225         of  the  vector is used as workspace by pcre_exec() while matching cap-         of the vector is used as workspace by pcre_exec() while  matching  cap-
2226         turing subpatterns, and is not available for passing back  information.         turing  subpatterns, and is not available for passing back information.
2227         The  number passed in ovecsize should always be a multiple of three. If         The number passed in ovecsize should always be a multiple of three.  If
2228         it is not, it is rounded down.         it is not, it is rounded down.
2229    
2230         When a match is successful, information about  captured  substrings  is         When  a  match  is successful, information about captured substrings is
2231         returned  in  pairs  of integers, starting at the beginning of ovector,         returned in pairs of integers, starting at the  beginning  of  ovector,
2232         and continuing up to two-thirds of its length at the  most.  The  first         and  continuing  up  to two-thirds of its length at the most. The first
2233         element  of  each pair is set to the byte offset of the first character         element of each pair is set to the byte offset of the  first  character
2234         in a substring, and the second is set to the byte offset of  the  first         in  a  substring, and the second is set to the byte offset of the first
2235         character  after  the end of a substring. Note: these values are always         character after the end of a substring. Note: these values  are  always
2236         byte offsets, even in UTF-8 mode. They are not character counts.         byte offsets, even in UTF-8 mode. They are not character counts.
2237    
2238         The first pair of integers, ovector[0]  and  ovector[1],  identify  the         The  first  pair  of  integers, ovector[0] and ovector[1], identify the
2239         portion  of  the subject string matched by the entire pattern. The next         portion of the subject string matched by the entire pattern.  The  next
2240         pair is used for the first capturing subpattern, and so on.  The  value         pair  is  used for the first capturing subpattern, and so on. The value
2241         returned by pcre_exec() is one more than the highest numbered pair that         returned by pcre_exec() is one more than the highest numbered pair that
2242         has been set.  For example, if two substrings have been  captured,  the         has  been  set.  For example, if two substrings have been captured, the
2243         returned  value is 3. If there are no capturing subpatterns, the return         returned value is 3. If there are no capturing subpatterns, the  return
2244         value from a successful match is 1, indicating that just the first pair         value from a successful match is 1, indicating that just the first pair
2245         of offsets has been set.         of offsets has been set.
2246    
2247         If a capturing subpattern is matched repeatedly, it is the last portion         If a capturing subpattern is matched repeatedly, it is the last portion
2248         of the string that it matched that is returned.         of the string that it matched that is returned.
2249    
2250         If the vector is too small to hold all the captured substring  offsets,         If  the vector is too small to hold all the captured substring offsets,
2251         it is used as far as possible (up to two-thirds of its length), and the         it is used as far as possible (up to two-thirds of its length), and the
2252         function returns a value of zero. If the substring offsets are  not  of         function  returns  a value of zero. If the substring offsets are not of
2253         interest,  pcre_exec()  may  be  called with ovector passed as NULL and         interest, pcre_exec() may be called with ovector  passed  as  NULL  and
2254         ovecsize as zero. However, if the pattern contains back references  and         ovecsize  as zero. However, if the pattern contains back references and
2255         the  ovector is not big enough to remember the related substrings, PCRE         the ovector is not big enough to remember the related substrings,  PCRE
2256         has to get additional memory for use during matching. Thus it  is  usu-         has  to  get additional memory for use during matching. Thus it is usu-
2257         ally advisable to supply an ovector.         ally advisable to supply an ovector.
2258    
2259         The pcre_fullinfo() function can be used to find out how many capturing         The pcre_fullinfo() function can be used to find out how many capturing
2260         subpatterns there are in a compiled  pattern.  The  smallest  size  for         subpatterns  there  are  in  a  compiled pattern. The smallest size for
2261         ovector  that  will allow for n captured substrings, in addition to the         ovector that will allow for n captured substrings, in addition  to  the
2262         offsets of the substring matched by the whole pattern, is (n+1)*3.         offsets of the substring matched by the whole pattern, is (n+1)*3.
2263    
2264         It is possible for capturing subpattern number n+1 to match  some  part         It  is  possible for capturing subpattern number n+1 to match some part
2265         of the subject when subpattern n has not been used at all. For example,         of the subject when subpattern n has not been used at all. For example,
2266         if the string "abc" is matched  against  the  pattern  (a|(z))(bc)  the         if  the  string  "abc"  is  matched against the pattern (a|(z))(bc) the
2267         return from the function is 4, and subpatterns 1 and 3 are matched, but         return from the function is 4, and subpatterns 1 and 3 are matched, but
2268         2 is not. When this happens, both values in  the  offset  pairs  corre-         2  is  not.  When  this happens, both values in the offset pairs corre-
2269         sponding to unused subpatterns are set to -1.         sponding to unused subpatterns are set to -1.
2270    
2271         Offset  values  that correspond to unused subpatterns at the end of the         Offset values that correspond to unused subpatterns at the end  of  the
2272         expression are also set to -1. For example,  if  the  string  "abc"  is         expression  are  also  set  to  -1. For example, if the string "abc" is
2273         matched  against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are not         matched against the pattern (abc)(x(yz)?)? subpatterns 2 and 3 are  not
2274         matched. The return from the function is 2, because  the  highest  used         matched.  The  return  from the function is 2, because the highest used
2275         capturing subpattern number is 1. However, you can refer to the offsets         capturing subpattern number is 1. However, you can refer to the offsets
2276         for the second and third capturing subpatterns if  you  wish  (assuming         for  the  second  and third capturing subpatterns if you wish (assuming
2277         the vector is large enough, of course).         the vector is large enough, of course).
2278    
2279         Some  convenience  functions  are  provided for extracting the captured         Some convenience functions are provided  for  extracting  the  captured
2280         substrings as separate strings. These are described below.         substrings as separate strings. These are described below.
2281    
2282     Error return values from pcre_exec()     Error return values from pcre_exec()
2283    
2284         If pcre_exec() fails, it returns a negative number. The  following  are         If  pcre_exec()  fails, it returns a negative number. The following are
2285         defined in the header file:         defined in the header file:
2286    
2287           PCRE_ERROR_NOMATCH        (-1)           PCRE_ERROR_NOMATCH        (-1)
# Line 2285  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2290  MATCHING A PATTERN: THE TRADITIONAL FUNC
2290    
2291           PCRE_ERROR_NULL           (-2)           PCRE_ERROR_NULL           (-2)
2292    
2293         Either  code  or  subject  was  passed as NULL, or ovector was NULL and         Either code or subject was passed as NULL,  or  ovector  was  NULL  and
2294         ovecsize was not zero.         ovecsize was not zero.
2295    
2296           PCRE_ERROR_BADOPTION      (-3)           PCRE_ERROR_BADOPTION      (-3)
# Line 2294  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2299  MATCHING A PATTERN: THE TRADITIONAL FUNC
2299    
2300           PCRE_ERROR_BADMAGIC       (-4)           PCRE_ERROR_BADMAGIC       (-4)
2301    
2302         PCRE stores a 4-byte "magic number" at the start of the compiled  code,         PCRE  stores a 4-byte "magic number" at the start of the compiled code,
2303         to catch the case when it is passed a junk pointer and to detect when a         to catch the case when it is passed a junk pointer and to detect when a
2304         pattern that was compiled in an environment of one endianness is run in         pattern that was compiled in an environment of one endianness is run in
2305         an  environment  with the other endianness. This is the error that PCRE         an environment with the other endianness. This is the error  that  PCRE
2306         gives when the magic number is not present.         gives when the magic number is not present.
2307    
2308           PCRE_ERROR_UNKNOWN_OPCODE (-5)           PCRE_ERROR_UNKNOWN_OPCODE (-5)
2309    
2310         While running the pattern match, an unknown item was encountered in the         While running the pattern match, an unknown item was encountered in the
2311         compiled  pattern.  This  error  could be caused by a bug in PCRE or by         compiled pattern. This error could be caused by a bug  in  PCRE  or  by
2312         overwriting of the compiled pattern.         overwriting of the compiled pattern.
2313    
2314           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2315    
2316         If a pattern contains back references, but the ovector that  is  passed         If  a  pattern contains back references, but the ovector that is passed
2317         to pcre_exec() is not big enough to remember the referenced substrings,         to pcre_exec() is not big enough to remember the referenced substrings,
2318         PCRE gets a block of memory at the start of matching to  use  for  this         PCRE  gets  a  block of memory at the start of matching to use for this
2319         purpose.  If the call via pcre_malloc() fails, this error is given. The         purpose. If the call via pcre_malloc() fails, this error is given.  The
2320         memory is automatically freed at the end of matching.         memory is automatically freed at the end of matching.
2321    
2322         This error is also given if pcre_stack_malloc() fails  in  pcre_exec().         This  error  is also given if pcre_stack_malloc() fails in pcre_exec().
2323         This  can happen only when PCRE has been compiled with --disable-stack-         This can happen only when PCRE has been compiled with  --disable-stack-
2324         for-recursion.         for-recursion.
2325    
2326           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2327    
2328         This error is used by the pcre_copy_substring(),  pcre_get_substring(),         This  error is used by the pcre_copy_substring(), pcre_get_substring(),
2329         and  pcre_get_substring_list()  functions  (see  below).  It  is  never         and  pcre_get_substring_list()  functions  (see  below).  It  is  never
2330         returned by pcre_exec().         returned by pcre_exec().
2331    
2332           PCRE_ERROR_MATCHLIMIT     (-8)           PCRE_ERROR_MATCHLIMIT     (-8)
2333    
2334         The backtracking limit, as specified by  the  match_limit  field  in  a         The  backtracking  limit,  as  specified  by the match_limit field in a
2335         pcre_extra  structure  (or  defaulted) was reached. See the description         pcre_extra structure (or defaulted) was reached.  See  the  description
2336         above.         above.
2337    
2338           PCRE_ERROR_CALLOUT        (-9)           PCRE_ERROR_CALLOUT        (-9)
2339    
2340         This error is never generated by pcre_exec() itself. It is provided for         This error is never generated by pcre_exec() itself. It is provided for
2341         use  by  callout functions that want to yield a distinctive error code.         use by callout functions that want to yield a distinctive  error  code.
2342         See the pcrecallout documentation for details.         See the pcrecallout documentation for details.
2343    
2344           PCRE_ERROR_BADUTF8        (-10)           PCRE_ERROR_BADUTF8        (-10)
2345    
2346         A string that contains an invalid UTF-8 byte sequence was passed  as  a         A  string  that contains an invalid UTF-8 byte sequence was passed as a
2347         subject.         subject.
2348    
2349           PCRE_ERROR_BADUTF8_OFFSET (-11)           PCRE_ERROR_BADUTF8_OFFSET (-11)
2350    
2351         The UTF-8 byte sequence that was passed as a subject was valid, but the         The UTF-8 byte sequence that was passed as a subject was valid, but the
2352         value of startoffset did not point to the beginning of a UTF-8  charac-         value  of startoffset did not point to the beginning of a UTF-8 charac-
2353         ter.         ter.
2354    
2355           PCRE_ERROR_PARTIAL        (-12)           PCRE_ERROR_PARTIAL        (-12)
2356    
2357         The  subject  string did not match, but it did match partially. See the         The subject string did not match, but it did match partially.  See  the
2358         pcrepartial documentation for details of partial matching.         pcrepartial documentation for details of partial matching.
2359    
2360           PCRE_ERROR_BADPARTIAL     (-13)           PCRE_ERROR_BADPARTIAL     (-13)
2361    
2362         This code is no longer in  use.  It  was  formerly  returned  when  the         This  code  is  no  longer  in  use.  It was formerly returned when the
2363         PCRE_PARTIAL  option  was used with a compiled pattern containing items         PCRE_PARTIAL option was used with a compiled pattern  containing  items
2364         that were  not  supported  for  partial  matching.  From  release  8.00         that  were  not  supported  for  partial  matching.  From  release 8.00
2365         onwards, there are no restrictions on partial matching.         onwards, there are no restrictions on partial matching.
2366    
2367           PCRE_ERROR_INTERNAL       (-14)           PCRE_ERROR_INTERNAL       (-14)
2368    
2369         An  unexpected  internal error has occurred. This error could be caused         An unexpected internal error has occurred. This error could  be  caused
2370         by a bug in PCRE or by overwriting of the compiled pattern.         by a bug in PCRE or by overwriting of the compiled pattern.
2371    
2372           PCRE_ERROR_BADCOUNT       (-15)           PCRE_ERROR_BADCOUNT       (-15)
# Line 2371  MATCHING A PATTERN: THE TRADITIONAL FUNC Line 2376  MATCHING A PATTERN: THE TRADITIONAL FUNC
2376           PCRE_ERROR_RECURSIONLIMIT (-21)           PCRE_ERROR_RECURSIONLIMIT (-21)
2377    
2378         The internal recursion limit, as specified by the match_limit_recursion         The internal recursion limit, as specified by the match_limit_recursion
2379         field  in  a  pcre_extra  structure (or defaulted) was reached. See the         field in a pcre_extra structure (or defaulted)  was  reached.  See  the
2380         description above.         description above.
2381    
2382           PCRE_ERROR_BADNEWLINE     (-23)           PCRE_ERROR_BADNEWLINE     (-23)
# Line 2394  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER Line 2399  EXTRACTING CAPTURED SUBSTRINGS BY NUMBER
2399         int pcre_get_substring_list(const char *subject,         int pcre_get_substring_list(const char *subject,
2400              int *ovector, int stringcount, const char ***listptr);              int *ovector, int stringcount, const char ***listptr);
2401    
2402         Captured substrings can be  accessed  directly  by  using  the  offsets         Captured  substrings  can  be  accessed  directly  by using the offsets
2403         returned  by  pcre_exec()  in  ovector.  For convenience, the functions         returned by pcre_exec() in  ovector.  For  convenience,  the  functions
2404         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-         pcre_copy_substring(),    pcre_get_substring(),    and    pcre_get_sub-
2405         string_list()  are  provided for extracting captured substrings as new,         string_list() are provided for extracting captured substrings  as  new,
2406         separate, zero-terminated strings. These functions identify  substrings         separate,  zero-terminated strings. These functions identify substrings
2407         by  number.  The  next section describes functions for extracting named         by number. The next section describes functions  for  extracting  named
2408         substrings.         substrings.
2409    
2410         A substring that contains a binary zero is correctly extracted and  has         A  substring that contains a binary zero is correctly extracted and has
2411         a  further zero added on the end, but the result is not, of course, a C         a further zero added on the end, but the result is not, of course, a  C
2412         string.  However, you can process such a string  by  referring  to  the         string.   However,  you  can  process such a string by referring to the
2413         length  that  is  returned  by  pcre_copy_substring() and pcre_get_sub-         length that is  returned  by  pcre_copy_substring()  and  pcre_get_sub-
2414         string().  Unfortunately, the interface to pcre_get_substring_list() is         string().  Unfortunately, the interface to pcre_get_substring_list() is
2415         not  adequate for handling strings containing binary zeros, because the         not adequate for handling strings containing binary zeros, because  the
2416         end of the final string is not independently indicated.         end of the final string is not independently indicated.
2417    
2418         The first three arguments are the same for all  three  of  these  func-         The  first  three  arguments  are the same for all three of these func-
2419         tions:  subject  is  the subject string that has just been successfully         tions: subject is the subject string that has  just  been  successfully
2420         matched, ovector is a pointer to the vector of integer offsets that was         matched, ovector is a pointer to the vector of integer offsets that was
2421         passed to pcre_exec(), and stringcount is the number of substrings that         passed to pcre_exec(), and stringcount is the number of substrings that
2422         were captured by the match, including the substring  that  matched  the         were  captured  by  the match, including the substring that matched the
2423         entire regular expression. This is the value returned by pcre_exec() if         entire regular expression. This is the value returned by pcre_exec() if
2424         it is greater than zero. If pcre_exec() returned zero, indicating  that         it  is greater than zero. If pcre_exec() returned zero, indicating that
2425         it  ran out of space in ovector, the value passed as stringcount should         it ran out of space in ovector, the value passed as stringcount  should
2426         be the number of elements in the vector divided by three.         be the number of elements in the vector divided by three.
2427    
2428         The functions pcre_copy_substring() and pcre_get_substring() extract  a         The  functions pcre_copy_substring() and pcre_get_substring() extract a
2429         single  substring,  whose  number  is given as stringnumber. A value of         single substring, whose number is given as  stringnumber.  A  value  of
2430         zero extracts the substring that matched the  entire  pattern,  whereas         zero  extracts  the  substring that matched the entire pattern, whereas
2431         higher  values  extract  the  captured  substrings.  For pcre_copy_sub-         higher values  extract  the  captured  substrings.  For  pcre_copy_sub-
2432         string(), the string is placed in buffer,  whose  length  is  given  by         string(),  the  string  is  placed  in buffer, whose length is given by
2433         buffersize,  while  for  pcre_get_substring()  a new block of memory is         buffersize, while for pcre_get_substring() a new  block  of  memory  is
2434         obtained via pcre_malloc, and its address is  returned  via  stringptr.         obtained  via  pcre_malloc,  and its address is returned via stringptr.
2435         The  yield  of  the function is the length of the string, not including         The yield of the function is the length of the  string,  not  including
2436         the terminating zero, or one of these error codes:         the terminating zero, or one of these error codes:
2437    
2438           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2439    
2440         The buffer was too small for pcre_copy_substring(), or the  attempt  to         The  buffer  was too small for pcre_copy_substring(), or the attempt to
2441         get memory failed for pcre_get_substring().         get memory failed for pcre_get_substring().
2442    
2443           PCRE_ERROR_NOSUBSTRING    (-7)           PCRE_ERROR_NOSUBSTRING    (-7)
2444    
2445         There is no substring whose number is stringnumber.         There is no substring whose number is stringnumber.
2446    
2447         The  pcre_get_substring_list()  function  extracts  all  available sub-         The pcre_get_substring_list()  function  extracts  all  available  sub-
2448         strings and builds a list of pointers to them. All this is  done  in  a         strings  and  builds  a list of pointers to them. All this is done in a
2449         single block of memory that is obtained via pcre_malloc. The address of         single block of memory that is obtained via pcre_malloc. The address of
2450         the memory block is returned via listptr, which is also  the  start  of         the  memory  block  is returned via listptr, which is also the start of
2451         the  list  of  string pointers. The end of the list is marked by a NULL         the list of string pointers. The end of the list is marked  by  a  NULL
2452         pointer. The yield of the function is zero if all  went  well,  or  the         pointer.  The  yield  of  the function is zero if all went well, or the
2453         error code         error code
2454    
2455           PCRE_ERROR_NOMEMORY       (-6)           PCRE_ERROR_NOMEMORY       (-6)
2456    
2457         if the attempt to get the memory block failed.         if the attempt to get the memory block failed.
2458    
2459         When  any of these functions encounter a substring that is unset, which         When any of these functions encounter a substring that is unset,  which
2460         can happen when capturing subpattern number n+1 matches  some  part  of         can  happen  when  capturing subpattern number n+1 matches some part of
2461         the  subject, but subpattern n has not been used at all, they return an         the subject, but subpattern n has not been used at all, they return  an
2462         empty string. This can be distinguished from a genuine zero-length sub-         empty string. This can be distinguished from a genuine zero-length sub-
2463         string  by inspecting the appropriate offset in ovector, which is nega-         string by inspecting the appropriate offset in ovector, which is  nega-
2464         tive for unset substrings.         tive for unset substrings.
2465    
2466         The two convenience functions pcre_free_substring() and  pcre_free_sub-         The  two convenience functions pcre_free_substring() and pcre_free_sub-
2467         string_list()  can  be  used  to free the memory returned by a previous         string_list() can be used to free the memory  returned  by  a  previous
2468         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-         call  of  pcre_get_substring()  or  pcre_get_substring_list(),  respec-
2469         tively.  They  do  nothing  more  than  call the function pointed to by         tively. They do nothing more than  call  the  function  pointed  to  by
2470         pcre_free, which of course could be called directly from a  C  program.         pcre_free,  which  of course could be called directly from a C program.
2471         However,  PCRE is used in some situations where it is linked via a spe-         However, PCRE is used in some situations where it is linked via a  spe-
2472         cial  interface  to  another  programming  language  that  cannot   use         cial   interface  to  another  programming  language  that  cannot  use
2473         pcre_free  directly;  it is for these cases that the functions are pro-         pcre_free directly; it is for these cases that the functions  are  pro-
2474         vided.         vided.
2475    
2476    
# Line 2484  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2489  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2489              int stringcount, const char *stringname,              int stringcount, const char *stringname,
2490              const char **stringptr);              const char **stringptr);
2491    
2492         To extract a substring by name, you first have to find associated  num-         To  extract a substring by name, you first have to find associated num-
2493         ber.  For example, for this pattern         ber.  For example, for this pattern
2494    
2495           (a+)b(?<xxx>\d+)...           (a+)b(?<xxx>\d+)...
# Line 2493  EXTRACTING CAPTURED SUBSTRINGS BY NAME Line 2498  EXTRACTING CAPTURED SUBSTRINGS BY NAME
2498         be unique (PCRE_DUPNAMES was not set), you can find the number from the         be unique (PCRE_DUPNAMES was not set), you can find the number from the
2499         name by calling pcre_get_stringnumber(). The first argument is the com-         name by calling pcre_get_stringnumber(). The first argument is the com-
2500         piled pattern, and the second is the name. The yield of the function is         piled pattern, and the second is the name. The yield of the function is
2501         the  subpattern  number,  or PCRE_ERROR_NOSUBSTRING (-7) if there is no         the subpattern number, or PCRE_ERROR_NOSUBSTRING (-7) if  there  is  no
2502         subpattern of that name.         subpattern of that name.
2503    
2504         Given the number, you can extract the substring directly, or use one of         Given the number, you can extract the substring directly, or use one of
2505         the functions described in the previous section. For convenience, there         the functions described in the previous section. For convenience, there
2506         are also two functions that do the whole job.         are also two functions that do the whole job.
2507    
2508         Most   of   the   arguments    of    pcre_copy_named_substring()    and         Most    of    the    arguments   of   pcre_copy_named_substring()   and
2509         pcre_get_named_substring()  are  the  same  as  those for the similarly         pcre_get_named_substring() are the same  as  those  for  the  similarly
2510         named functions that extract by number. As these are described  in  the         named  functions  that extract by number. As these are described in the
2511         previous  section,  they  are not re-described here. There are just two         previous section, they are not re-described here. There  are  just  two
2512         differences:         differences:
2513    
2514         First, instead of a substring number, a substring name is  given.  Sec-         First,  instead  of a substring number, a substring name is given. Sec-
2515         ond, there is an extra argument, given at the start, which is a pointer         ond, there is an extra argument, given at the start, which is a pointer
2516         to the compiled pattern. This is needed in order to gain access to  the         to  the compiled pattern. This is needed in order to gain access to the
2517         name-to-number translation table.         name-to-number translation table.
2518    
2519         These  functions call pcre_get_stringnumber(), and if it succeeds, they         These functions call pcre_get_stringnumber(), and if it succeeds,  they
2520         then call pcre_copy_substring() or pcre_get_substring(),  as  appropri-         then  call  pcre_copy_substring() or pcre_get_substring(), as appropri-
2521         ate.  NOTE:  If PCRE_DUPNAMES is set and there are duplicate names, the         ate. NOTE: If PCRE_DUPNAMES is set and there are duplicate  names,  the
2522         behaviour may not be what you want (see the next section).         behaviour may not be what you want (see the next section).
2523    
2524         Warning: If the pattern uses the (?| feature to set up multiple subpat-         Warning: If the pattern uses the (?| feature to set up multiple subpat-
2525         terns  with  the  same number, as described in the section on duplicate         terns with the same number, as described in the  section  on  duplicate
2526         subpattern numbers in the pcrepattern page, you  cannot  use  names  to         subpattern  numbers  in  the  pcrepattern page, you cannot use names to
2527         distinguish  the  different subpatterns, because names are not included         distinguish the different subpatterns, because names are  not  included
2528         in the compiled code. The matching process uses only numbers. For  this         in  the compiled code. The matching process uses only numbers. For this
2529         reason,  the  use of different names for subpatterns of the same number         reason, the use of different names for subpatterns of the  same  number
2530         causes an error at compile time.         causes an error at compile time.
2531    
2532    
# Line 2530  DUPLICATE SUBPATTERN NAMES Line 2535  DUPLICATE SUBPATTERN NAMES
2535         int pcre_get_stringtable_entries(const pcre *code,         int pcre_get_stringtable_entries(const pcre *code,
2536              const char *name, char **first, char **last);              const char *name, char **first, char **last);
2537    
2538         When a pattern is compiled with the  PCRE_DUPNAMES  option,  names  for         When  a  pattern  is  compiled with the PCRE_DUPNAMES option, names for
2539         subpatterns  are not required to be unique. (Duplicate names are always         subpatterns are not required to be unique. (Duplicate names are  always
2540         allowed for subpatterns with the same number, created by using the  (?|         allowed  for subpatterns with the same number, created by using the (?|
2541         feature.  Indeed,  if  such subpatterns are named, they are required to         feature. Indeed, if such subpatterns are named, they  are  required  to
2542         use the same names.)         use the same names.)
2543    
2544         Normally, patterns with duplicate names are such that in any one match,         Normally, patterns with duplicate names are such that in any one match,
2545         only  one of the named subpatterns participates. An example is shown in         only one of the named subpatterns participates. An example is shown  in
2546         the pcrepattern documentation.         the pcrepattern documentation.
2547    
2548         When   duplicates   are   present,   pcre_copy_named_substring()    and         When    duplicates   are   present,   pcre_copy_named_substring()   and
2549         pcre_get_named_substring()  return the first substring corresponding to         pcre_get_named_substring() return the first substring corresponding  to
2550         the given name that is set. If  none  are  set,  PCRE_ERROR_NOSUBSTRING         the  given  name  that  is set. If none are set, PCRE_ERROR_NOSUBSTRING
2551         (-7)  is  returned;  no  data  is returned. The pcre_get_stringnumber()         (-7) is returned; no  data  is  returned.  The  pcre_get_stringnumber()
2552         function returns one of the numbers that are associated with the  name,         function  returns one of the numbers that are associated with the name,
2553         but it is not defined which it is.         but it is not defined which it is.
2554    
2555         If  you want to get full details of all captured substrings for a given         If you want to get full details of all captured substrings for a  given
2556         name, you must use  the  pcre_get_stringtable_entries()  function.  The         name,  you  must  use  the pcre_get_stringtable_entries() function. The
2557         first argument is the compiled pattern, and the second is the name. The         first argument is the compiled pattern, and the second is the name. The
2558         third and fourth are pointers to variables which  are  updated  by  the         third  and  fourth  are  pointers to variables which are updated by the
2559         function. After it has run, they point to the first and last entries in         function. After it has run, they point to the first and last entries in
2560         the name-to-number table  for  the  given  name.  The  function  itself         the  name-to-number  table  for  the  given  name.  The function itself
2561         returns  the  length  of  each entry, or PCRE_ERROR_NOSUBSTRING (-7) if         returns the length of each entry,  or  PCRE_ERROR_NOSUBSTRING  (-7)  if
2562         there are none. The format of the table is described above in the  sec-         there  are none. The format of the table is described above in the sec-
2563         tion  entitled  Information  about  a  pattern.  Given all the relevant         tion entitled Information about a  pattern.   Given  all  the  relevant
2564         entries for the name, you can extract each of their numbers, and  hence         entries  for the name, you can extract each of their numbers, and hence
2565         the captured data, if any.         the captured data, if any.
2566    
2567    
2568  FINDING ALL POSSIBLE MATCHES  FINDING ALL POSSIBLE MATCHES
2569    
2570         The  traditional  matching  function  uses a similar algorithm to Perl,         The traditional matching function uses a  similar  algorithm  to  Perl,
2571         which stops when it finds the first match, starting at a given point in         which stops when it finds the first match, starting at a given point in
2572         the  subject.  If you want to find all possible matches, or the longest         the subject. If you want to find all possible matches, or  the  longest
2573         possible match, consider using the alternative matching  function  (see         possible  match,  consider using the alternative matching function (see
2574         below)  instead.  If you cannot use the alternative function, but still         below) instead. If you cannot use the alternative function,  but  still
2575         need to find all possible matches, you can kludge it up by  making  use         need  to  find all possible matches, you can kludge it up by making use
2576         of the callout facility, which is described in the pcrecallout documen-         of the callout facility, which is described in the pcrecallout documen-
2577         tation.         tation.
2578    
2579         What you have to do is to insert a callout right at the end of the pat-         What you have to do is to insert a callout right at the end of the pat-
2580         tern.   When your callout function is called, extract and save the cur-         tern.  When your callout function is called, extract and save the  cur-
2581         rent matched substring. Then return  1,  which  forces  pcre_exec()  to         rent  matched  substring.  Then  return  1, which forces pcre_exec() to
2582         backtrack  and  try other alternatives. Ultimately, when it runs out of         backtrack and try other alternatives. Ultimately, when it runs  out  of
2583         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.         matches, pcre_exec() will yield PCRE_ERROR_NOMATCH.
2584    
2585    
# Line 2585  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2590  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2590              int options, int *ovector, int ovecsize,              int options, int *ovector, int ovecsize,
2591              int *workspace, int wscount);              int *workspace, int wscount);
2592    
2593         The function pcre_dfa_exec()  is  called  to  match  a  subject  string         The  function  pcre_dfa_exec()  is  called  to  match  a subject string
2594         against  a  compiled pattern, using a matching algorithm that scans the         against a compiled pattern, using a matching algorithm that  scans  the
2595         subject string just once, and does not backtrack.  This  has  different         subject  string  just  once, and does not backtrack. This has different
2596         characteristics  to  the  normal  algorithm, and is not compatible with         characteristics to the normal algorithm, and  is  not  compatible  with
2597         Perl. Some of the features of PCRE patterns are not  supported.  Never-         Perl.  Some  of the features of PCRE patterns are not supported. Never-
2598         theless,  there are times when this kind of matching can be useful. For         theless, there are times when this kind of matching can be useful.  For
2599         a discussion of the two matching algorithms, and  a  list  of  features         a  discussion  of  the  two matching algorithms, and a list of features
2600         that  pcre_dfa_exec() does not support, see the pcrematching documenta-         that pcre_dfa_exec() does not support, see the pcrematching  documenta-
2601         tion.         tion.
2602    
2603         The arguments for the pcre_dfa_exec() function  are  the  same  as  for         The  arguments  for  the  pcre_dfa_exec()  function are the same as for
2604         pcre_exec(), plus two extras. The ovector argument is used in a differ-         pcre_exec(), plus two extras. The ovector argument is used in a differ-
2605         ent way, and this is described below. The other  common  arguments  are         ent  way,  and  this is described below. The other common arguments are
2606         used  in  the  same way as for pcre_exec(), so their description is not         used in the same way as for pcre_exec(), so their  description  is  not
2607         repeated here.         repeated here.
2608    
2609         The two additional arguments provide workspace for  the  function.  The         The  two  additional  arguments provide workspace for the function. The
2610         workspace  vector  should  contain at least 20 elements. It is used for         workspace vector should contain at least 20 elements. It  is  used  for
2611         keeping  track  of  multiple  paths  through  the  pattern  tree.  More         keeping  track  of  multiple  paths  through  the  pattern  tree.  More
2612         workspace  will  be  needed for patterns and subjects where there are a         workspace will be needed for patterns and subjects where  there  are  a
2613         lot of potential matches.         lot of potential matches.
2614    
2615         Here is an example of a simple call to pcre_dfa_exec():         Here is an example of a simple call to pcre_dfa_exec():
# Line 2626  MATCHING A PATTERN: THE ALTERNATIVE FUNC Line 2631  MATCHING A PATTERN: THE ALTERNATIVE FUNC
2631    
2632     Option bits for pcre_dfa_exec()     Option bits for pcre_dfa_exec()
2633    
2634         The unused bits of the options argument  for  pcre_dfa_exec()  must  be         The  unused  bits  of  the options argument for pcre_dfa_exec() must be
2635         zero.  The  only  bits  that  may  be  set are PCRE_ANCHORED, PCRE_NEW-         zero. The only bits  that  may  be  set  are  PCRE_ANCHORED,  PCRE_NEW-
2636         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,         LINE_xxx,        PCRE_NOTBOL,        PCRE_NOTEOL,        PCRE_NOTEMPTY,
2637         PCRE_NOTEMPTY_ATSTART, PCRE_NO_UTF8_CHECK, PCRE_PARTIAL_HARD, PCRE_PAR-         PCRE_NOTEMPTY_ATSTART,      PCRE_NO_UTF8_CHECK,       PCRE_BSR_ANYCRLF,
2638         TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART. All  but  the  last         PCRE_BSR_UNICODE,  PCRE_NO_START_OPTIMIZE, PCRE_PARTIAL_HARD, PCRE_PAR-
2639           TIAL_SOFT, PCRE_DFA_SHORTEST, and PCRE_DFA_RESTART.  All but  the  last
2640         four  of  these  are  exactly  the  same  as  for pcre_exec(), so their         four  of  these  are  exactly  the  same  as  for pcre_exec(), so their
2641         description is not repeated here.         description is not repeated here.
2642    
# Line 2753  AUTHOR Line 2759  AUTHOR
2759    
2760  REVISION  REVISION
2761    
2762         Last updated: 01 June 2010         Last updated: 15 June 2010
2763         Copyright (c) 1997-2010 University of Cambridge.         Copyright (c) 1997-2010 University of Cambridge.
2764  ------------------------------------------------------------------------------  ------------------------------------------------------------------------------
2765    

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