[Pcre-svn] [1220] code/trunk/doc: Documentation update.

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Sujet: [Pcre-svn] [1220] code/trunk/doc: Documentation update.
Revision: 1220
          http://www.exim.org/viewvc/pcre2?view=rev&revision=1220
Author:   ph10
Date:     2020-02-16 17:47:14 +0000 (Sun, 16 Feb 2020)
Log Message:
-----------
Documentation update.


Modified Paths:
--------------
    code/trunk/doc/html/pcre2api.html
    code/trunk/doc/pcre2.txt


Modified: code/trunk/doc/html/pcre2api.html
===================================================================
--- code/trunk/doc/html/pcre2api.html    2020-02-16 17:46:40 UTC (rev 1219)
+++ code/trunk/doc/html/pcre2api.html    2020-02-16 17:47:14 UTC (rev 1220)
@@ -3309,13 +3309,13 @@
 option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to return just the
 replacement string(s). The default action is to perform just one replacement if
 the pattern matches, but there is an option that requests multiple replacements
-(see PCRE2_SUBSTITUTE_GLOBAL below for details).
+(see PCRE2_SUBSTITUTE_GLOBAL below).
 </P>
 <P>
 If successful, <b>pcre2_substitute()</b> returns the number of substitutions
 that were carried out. This may be zero if no match was found, and is never
 greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set. A negative value is
-returned if an error is detected (see below for details).
+returned if an error is detected.
 </P>
 <P>
 Matches in which a \K item in a lookahead in the pattern causes the match to
@@ -3333,10 +3333,11 @@
 allocate memory for the compiled code.
 </P>
 <P>
-If an external <i>match_data</i> block is provided, its contents afterwards
-are those set by the final call to <b>pcre2_match()</b>. For global changes,
-this will have ended in a no-match error. The contents of the ovector within
-the match data block may or may not have been changed.
+If <i>match_data</i> is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set, the
+provided block is used for all calls to <b>pcre2_match()</b>, and its contents
+afterwards are the result of the final call. For global changes, this will
+always be a no-match error. The contents of the ovector within the match data
+block may or may not have been changed.
 </P>
 <P>
 As well as the usual options for <b>pcre2_match()</b>, a number of additional
@@ -3350,17 +3351,24 @@
 having to repeat the match.
 </P>
 <P>
-The <i>code</i> argument is not used for the first substitution when
-PCRE2_SUBSTITUTE_MATCHED is set, but if PCRE2_SUBSTITUTE_GLOBAL is also set,
-<b>pcre2_match()</b> will be called after the first substitution to check for
-further matches, and the contents of the <i>match_data</i> block will be
-changed.
+The contents of the externally supplied match data block are not changed when
+PCRE2_SUBSTITUTE_MATCHED is set. If PCRE2_SUBSTITUTE_GLOBAL is also set,
+<b>pcre2_match()</b> is called after the first substitution to check for further
+matches, but this is done using an internally obtained match data block, thus
+always leaving the external block unchanged.
 </P>
 <P>
-The default is to return a copy of the subject string with matched substrings 
-replaced. However, if PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the 
-replacement substrings are returned. In the global case, multiple replacements 
-are concatenated in the output buffer. Substitution callouts (see
+The <i>code</i> argument is not used for matching before the first substitution
+when PCRE2_SUBSTITUTE_MATCHED is set, but it must be provided, even when
+PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains information such as the
+UTF setting and the number of capturing parentheses in the pattern.
+</P>
+<P>
+The default action of <b>pcre2_substitute()</b> is to return a copy of the
+subject string with matched substrings replaced. However, if
+PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set, only the replacement substrings are
+returned. In the global case, multiple replacements are concatenated in the
+output buffer. Substitution callouts (see
 <a href="#subcallouts">below)</a>
 can be used to separate them if necessary.
 </P>
@@ -3367,8 +3375,9 @@
 <P>
 The <i>outlengthptr</i> argument of <b>pcre2_substitute()</b> must point to a
 variable that contains the length, in code units, of the output buffer. If the
-function is successful, the value is updated to contain the length of the new
-string, excluding the trailing zero that is automatically added.
+function is successful, the value is updated to contain the length in code
+units of the new string, excluding the trailing zero that is automatically
+added.
 </P>
 <P>
 If the function is not successful, the value set via <i>outlengthptr</i> depends
@@ -3375,20 +3384,35 @@
 on the type of error. For syntax errors in the replacement string, the value is
 the offset in the replacement string where the error was detected. For other
 errors, the value is PCRE2_UNSET by default. This includes the case of the
-output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set
-(see below), in which case the value is the minimum length needed, including
-space for the trailing zero. Note that in order to compute the required length,
-<b>pcre2_substitute()</b> has to simulate all the matching and copying, instead
-of giving an error return as soon as the buffer overflows. Note also that the
-length is in code units, not bytes.
+output buffer being too small, unless PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set.
 </P>
 <P>
-The replacement string, which is interpreted as a UTF string in UTF mode,
-is checked for UTF validity unless the PCRE2_NO_UTF_CHECK option is set. If the
-PCRE2_SUBSTITUTE_LITERAL option is set, it is not interpreted in any way. By
-default, however, a dollar character is an escape character that can specify
-the insertion of characters from capture groups and names from (*MARK) or other
-control verbs in the pattern. The following forms are always recognized:
+PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is
+too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If
+this option is set, however, <b>pcre2_substitute()</b> continues to go through
+the motions of matching and substituting (without, of course, writing anything)
+in order to compute the size of buffer that is needed. This value is passed
+back via the <i>outlengthptr</i> variable, with the result of the function still
+being PCRE2_ERROR_NOMEMORY.
+</P>
+<P>
+Passing a buffer size of zero is a permitted way of finding out how much memory
+is needed for given substitution. However, this does mean that the entire
+operation is carried out twice. Depending on the application, it may be more
+efficient to allocate a large buffer and free the excess afterwards, instead of
+using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH.
+</P>
+<P>
+The replacement string, which is interpreted as a UTF string in UTF mode, is
+checked for UTF validity unless PCRE2_NO_UTF_CHECK is set. An invalid UTF
+replacement string causes an immediate return with the relevant UTF error code.
+</P>
+<P>
+If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is not interpreted
+in any way. By default, however, a dollar character is an escape character that
+can specify the insertion of characters from capture groups and names from
+(*MARK) or other control verbs in the pattern. The following forms are always
+recognized:
 <pre>
   $$                  insert a dollar character
   $&#60;n&#62; or ${&#60;n&#62;}      insert the contents of group &#60;n&#62;
@@ -3436,22 +3460,6 @@
 this case, the offset is advanced by two characters.
 </P>
 <P>
-PCRE2_SUBSTITUTE_OVERFLOW_LENGTH changes what happens when the output buffer is
-too small. The default action is to return PCRE2_ERROR_NOMEMORY immediately. If
-this option is set, however, <b>pcre2_substitute()</b> continues to go through
-the motions of matching and substituting (without, of course, writing anything)
-in order to compute the size of buffer that is needed. This value is passed
-back via the <i>outlengthptr</i> variable, with the result of the function still
-being PCRE2_ERROR_NOMEMORY.
-</P>
-<P>
-Passing a buffer size of zero is a permitted way of finding out how much memory
-is needed for given substitution. However, this does mean that the entire
-operation is carried out twice. Depending on the application, it may be more
-efficient to allocate a large buffer and free the excess afterwards, instead of
-using PCRE2_SUBSTITUTE_OVERFLOW_LENGTH.
-</P>
-<P>
 PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that do
 not appear in the pattern to be treated as unset groups. This option should be
 used with care, because it means that a typo in a group name or number no
@@ -3907,7 +3915,7 @@
 </P>
 <br><a name="SEC42" href="#TOC1">REVISION</a><br>
 <P>
-Last updated: 22 January 2020
+Last updated: 16 February 2020
 <br>
 Copyright &copy; 1997-2020 University of Cambridge.
 <br>


Modified: code/trunk/doc/pcre2.txt
===================================================================
--- code/trunk/doc/pcre2.txt    2020-02-16 17:46:40 UTC (rev 1219)
+++ code/trunk/doc/pcre2.txt    2020-02-16 17:47:14 UTC (rev 1220)
@@ -3200,13 +3200,13 @@
        There is an option (see PCRE2_SUBSTITUTE_REPLACEMENT_ONLY below) to re-
        turn  just  the replacement string(s). The default action is to perform
        just one replacement if the pattern matches, but  there  is  an  option
-       that  requests multiple replacements (see PCRE2_SUBSTITUTE_GLOBAL below
-       for details).
+       that  requests  multiple  replacements (see PCRE2_SUBSTITUTE_GLOBAL be-
+       low).


        If successful, pcre2_substitute() returns the number  of  substitutions
        that  were  carried out. This may be zero if no match was found, and is
        never greater than one unless PCRE2_SUBSTITUTE_GLOBAL is set.  A  nega-
-       tive value is returned if an error is detected (see below for details).
+       tive value is returned if an error is detected.


        Matches  in  which  a  \K item in a lookahead in the pattern causes the
        match to end before it starts are not supported, and give  rise  to  an
@@ -3221,75 +3221,98 @@
        ment  functions from the match context, if provided, or else those that
        were used to allocate memory for the compiled code.


-       If an external match_data block is provided,  its  contents  afterwards
-       are  those  set by the final call to pcre2_match(). For global changes,
-       this will have ended in a no-match error. The contents of  the  ovector
-       within the match data block may or may not have been changed.
+       If match_data is not NULL and PCRE2_SUBSTITUTE_MATCHED is not set,  the
+       provided block is used for all calls to pcre2_match(), and its contents
+       afterwards are the result of the final call. For global  changes,  this
+       will always be a no-match error. The contents of the ovector within the
+       match data block may or may not have been changed.


-       As  well as the usual options for pcre2_match(), a number of additional
-       options can be set in the options argument of pcre2_substitute().   One
-       such  option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an external
-       match_data block must be provided, and it must have been  used  for  an
-       external  call  to pcre2_match(). The data in the match_data block (re-
+       As well as the usual options for pcre2_match(), a number of  additional
+       options  can be set in the options argument of pcre2_substitute().  One
+       such option is PCRE2_SUBSTITUTE_MATCHED. When this is set, an  external
+       match_data  block  must  be provided, and it must have been used for an
+       external call to pcre2_match(). The data in the match_data  block  (re-
        turn code, offset vector) is used for the first substitution instead of
-       calling  pcre2_match()  from  within pcre2_substitute(). This allows an
+       calling pcre2_match() from within pcre2_substitute().  This  allows  an
        application to check for a match before choosing to substitute, without
        having to repeat the match.


-       The  code  argument  is  not  used  for  the  first  substitution  when
-       PCRE2_SUBSTITUTE_MATCHED is set, but if PCRE2_SUBSTITUTE_GLOBAL is also
-       set, pcre2_match() will be called after the first substitution to check
-       for further matches, and the contents of the match_data block  will  be
-       changed.
+       The contents of the  externally  supplied  match  data  block  are  not
+       changed   when   PCRE2_SUBSTITUTE_MATCHED   is  set.  If  PCRE2_SUBSTI-
+       TUTE_GLOBAL is also set, pcre2_match() is called after the  first  sub-
+       stitution  to  check for further matches, but this is done using an in-
+       ternally obtained match data block, thus always  leaving  the  external
+       block unchanged.


-       The default is to return a copy of the subject string with matched sub-
-       strings replaced. However, if PCRE2_SUBSTITUTE_REPLACEMENT_ONLY is set,
-       only  the replacement substrings are returned. In the global case, mul-
-       tiple replacements are concatenated in the output buffer.  Substitution
-       callouts (see below) can be used to separate them if necessary.
+       The  code  argument is not used for matching before the first substitu-
+       tion when PCRE2_SUBSTITUTE_MATCHED is set, but  it  must  be  provided,
+       even  when  PCRE2_SUBSTITUTE_GLOBAL is not set, because it contains in-
+       formation such as the UTF setting and the number of capturing parenthe-
+       ses in the pattern.


-       The  outlengthptr  argument of pcre2_substitute() must point to a vari-
-       able that contains the length, in code units, of the output buffer.  If
-       the  function is successful, the value is updated to contain the length
-       of the new string, excluding the trailing zero  that  is  automatically
-       added.
+       The  default  action  of  pcre2_substitute() is to return a copy of the
+       subject string with matched substrings replaced. However, if PCRE2_SUB-
+       STITUTE_REPLACEMENT_ONLY  is  set,  only the replacement substrings are
+       returned. In the global case, multiple replacements are concatenated in
+       the  output  buffer.  Substitution  callouts (see below) can be used to
+       separate them if necessary.


-       If  the  function is not successful, the value set via outlengthptr de-
-       pends on the type of  error.  For  syntax  errors  in  the  replacement
+       The outlengthptr argument of pcre2_substitute() must point to  a  vari-
+       able  that contains the length, in code units, of the output buffer. If
+       the function is successful, the value is updated to contain the  length
+       in  code  units  of the new string, excluding the trailing zero that is
+       automatically added.
+
+       If the function is not successful, the value set via  outlengthptr  de-
+       pends  on  the  type  of  error.  For  syntax errors in the replacement
        string, the value is the offset in the replacement string where the er-
-       ror was detected. For other errors, the value  is  PCRE2_UNSET  by  de-
+       ror  was  detected.  For  other errors, the value is PCRE2_UNSET by de-
        fault. This includes the case of the output buffer being too small, un-
-       less PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set (see below), in which case
-       the  value is the minimum length needed, including space for the trail-
-       ing zero. Note that in order to compute the required length, pcre2_sub-
-       stitute() has to simulate all the matching and copying, instead of giv-
-       ing an error return as soon as the buffer overflows. Note also that the
-       length is in code units, not bytes.
+       less PCRE2_SUBSTITUTE_OVERFLOW_LENGTH is set.


+       PCRE2_SUBSTITUTE_OVERFLOW_LENGTH  changes  what happens when the output
+       buffer is too small. The default action is to return PCRE2_ERROR_NOMEM-
+       ORY  immediately.  If  this  option is set, however, pcre2_substitute()
+       continues to go through the motions of matching and substituting (with-
+       out,  of course, writing anything) in order to compute the size of buf-
+       fer that is needed. This value is  passed  back  via  the  outlengthptr
+       variable,  with  the  result  of  the  function  still  being PCRE2_ER-
+       ROR_NOMEMORY.
+
+       Passing a buffer size of zero is a permitted way  of  finding  out  how
+       much  memory  is needed for given substitution. However, this does mean
+       that the entire operation is carried out twice. Depending on the appli-
+       cation,  it  may  be more efficient to allocate a large buffer and free
+       the  excess  afterwards,  instead   of   using   PCRE2_SUBSTITUTE_OVER-
+       FLOW_LENGTH.
+
        The  replacement  string,  which  is interpreted as a UTF string in UTF
-       mode, is checked for UTF validity unless the PCRE2_NO_UTF_CHECK  option
-       is set. If the PCRE2_SUBSTITUTE_LITERAL option is set, it is not inter-
-       preted in any way. By default, however, a dollar character is an escape
-       character  that  can  specify  the insertion of characters from capture
-       groups and names from (*MARK) or other control verbs  in  the  pattern.
-       The following forms are always recognized:
+       mode, is checked for UTF validity unless PCRE2_NO_UTF_CHECK is set.  An
+       invalid UTF replacement string causes an immediate return with the rel-
+       evant UTF error code.


+       If PCRE2_SUBSTITUTE_LITERAL is set, the replacement string is  not  in-
+       terpreted in any way. By default, however, a dollar character is an es-
+       cape character that can specify the insertion of characters  from  cap-
+       ture  groups  and names from (*MARK) or other control verbs in the pat-
+       tern. The following forms are always recognized:
+
          $$                  insert a dollar character
          $<n> or ${<n>}      insert the contents of group <n>
          $*MARK or ${*MARK}  insert a control verb name


-       Either  a  group  number  or  a  group name can be given for <n>. Curly
-       brackets are required only if the following character would  be  inter-
+       Either a group number or a group name  can  be  given  for  <n>.  Curly
+       brackets  are  required only if the following character would be inter-
        preted as part of the number or name. The number may be zero to include
-       the entire matched string.   For  example,  if  the  pattern  a(b)c  is
-       matched  with "=abc=" and the replacement string "+$1$0$1+", the result
+       the  entire  matched  string.   For  example,  if  the pattern a(b)c is
+       matched with "=abc=" and the replacement string "+$1$0$1+", the  result
        is "=+babcb+=".


-       $*MARK inserts the name from the last encountered backtracking  control
-       verb  on the matching path that has a name. (*MARK) must always include
-       a name, but the other verbs need not.  For  example,  in  the  case  of
+       $*MARK  inserts the name from the last encountered backtracking control
+       verb on the matching path that has a name. (*MARK) must always  include
+       a  name,  but  the  other  verbs  need not. For example, in the case of
        (*MARK:A)(*PRUNE) the name inserted is "A", but for (*MARK:A)(*PRUNE:B)
-       the relevant name is "B". This facility can be used to  perform  simple
+       the  relevant  name is "B". This facility can be used to perform simple
        simultaneous substitutions, as this pcre2test example shows:


          /(*MARK:pear)apple|(*MARK:orange)lemon/g,replace=${*MARK}
@@ -3297,15 +3320,15 @@
           2: pear orange


        PCRE2_SUBSTITUTE_GLOBAL causes the function to iterate over the subject
-       string, replacing every matching substring. If this option is not  set,
-       only  the  first matching substring is replaced. The search for matches
-       takes place in the original subject string (that is, previous  replace-
-       ments  do  not  affect  it).  Iteration is implemented by advancing the
-       startoffset value for each search, which is always  passed  the  entire
+       string,  replacing every matching substring. If this option is not set,
+       only the first matching substring is replaced. The search  for  matches
+       takes  place in the original subject string (that is, previous replace-
+       ments do not affect it).  Iteration is  implemented  by  advancing  the
+       startoffset  value  for  each search, which is always passed the entire
        subject string. If an offset limit is set in the match context, search-
        ing stops when that limit is reached.


-       You can restrict the effect of a global substitution to  a  portion  of
+       You  can  restrict  the effect of a global substitution to a portion of
        the subject string by setting either or both of startoffset and an off-
        set limit. Here is a pcre2test example:


@@ -3313,87 +3336,71 @@
          ABC ABC ABC ABC\=offset=3,offset_limit=12
           2: ABC A!C A!C ABC


-       When continuing with global substitutions after  matching  a  substring
+       When  continuing  with  global substitutions after matching a substring
        with zero length, an attempt to find a non-empty match at the same off-
        set is performed.  If this is not successful, the offset is advanced by
        one character except when CRLF is a valid newline sequence and the next
-       two characters are CR, LF. In this case, the offset is advanced by  two
+       two  characters are CR, LF. In this case, the offset is advanced by two
        characters.


-       PCRE2_SUBSTITUTE_OVERFLOW_LENGTH  changes  what happens when the output
-       buffer is too small. The default action is to return PCRE2_ERROR_NOMEM-
-       ORY  immediately.  If  this  option is set, however, pcre2_substitute()
-       continues to go through the motions of matching and substituting (with-
-       out,  of course, writing anything) in order to compute the size of buf-
-       fer that is needed. This value is  passed  back  via  the  outlengthptr
-       variable,  with  the  result  of  the  function  still  being PCRE2_ER-
-       ROR_NOMEMORY.
-
-       Passing a buffer size of zero is a permitted way  of  finding  out  how
-       much  memory  is needed for given substitution. However, this does mean
-       that the entire operation is carried out twice. Depending on the appli-
-       cation,  it  may  be more efficient to allocate a large buffer and free
-       the  excess  afterwards,  instead   of   using   PCRE2_SUBSTITUTE_OVER-
-       FLOW_LENGTH.
-
        PCRE2_SUBSTITUTE_UNKNOWN_UNSET causes references to capture groups that
        do not appear in the pattern to be treated as unset groups. This option
-       should  be used with care, because it means that a typo in a group name
+       should be used with care, because it means that a typo in a group  name
        or number no longer causes the PCRE2_ERROR_NOSUBSTRING error.


        PCRE2_SUBSTITUTE_UNSET_EMPTY causes unset capture groups (including un-
-       known  groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be treated
-       as empty strings when inserted as described above. If  this  option  is
+       known groups when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set) to be  treated
+       as  empty  strings  when inserted as described above. If this option is
        not set, an attempt to insert an unset group causes the PCRE2_ERROR_UN-
-       SET error. This option does not  influence  the  extended  substitution
+       SET  error.  This  option  does not influence the extended substitution
        syntax described below.


-       PCRE2_SUBSTITUTE_EXTENDED  causes extra processing to be applied to the
-       replacement string. Without this option, only the dollar  character  is
-       special,  and  only  the  group insertion forms listed above are valid.
+       PCRE2_SUBSTITUTE_EXTENDED causes extra processing to be applied to  the
+       replacement  string.  Without this option, only the dollar character is
+       special, and only the group insertion forms  listed  above  are  valid.
        When PCRE2_SUBSTITUTE_EXTENDED is set, two things change:


-       Firstly, backslash in a replacement string is interpreted as an  escape
+       Firstly,  backslash in a replacement string is interpreted as an escape
        character. The usual forms such as \n or \x{ddd} can be used to specify
-       particular character codes, and backslash followed by any  non-alphanu-
-       meric  character  quotes  that character. Extended quoting can be coded
+       particular  character codes, and backslash followed by any non-alphanu-
+       meric character quotes that character. Extended quoting  can  be  coded
        using \Q...\E, exactly as in pattern strings.


-       There are also four escape sequences for forcing the case  of  inserted
-       letters.   The  insertion  mechanism has three states: no case forcing,
+       There  are  also four escape sequences for forcing the case of inserted
+       letters.  The insertion mechanism has three states:  no  case  forcing,
        force upper case, and force lower case. The escape sequences change the
        current state: \U and \L change to upper or lower case forcing, respec-
-       tively, and \E (when not terminating a \Q quoted sequence)  reverts  to
-       no  case  forcing. The sequences \u and \l force the next character (if
-       it is a letter) to upper or lower  case,  respectively,  and  then  the
+       tively,  and  \E (when not terminating a \Q quoted sequence) reverts to
+       no case forcing. The sequences \u and \l force the next  character  (if
+       it  is  a  letter)  to  upper or lower case, respectively, and then the
        state automatically reverts to no case forcing. Case forcing applies to
-       all inserted  characters, including those from capture groups and  let-
+       all  inserted  characters, including those from capture groups and let-
        ters within \Q...\E quoted sequences.


        Note that case forcing sequences such as \U...\E do not nest. For exam-
-       ple, the result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc";  the  final
-       \E  has  no  effect.  Note  also  that the PCRE2_ALT_BSUX and PCRE2_EX-
+       ple,  the  result of processing "\Uaa\LBB\Ecc\E" is "AAbbcc"; the final
+       \E has no effect. Note  also  that  the  PCRE2_ALT_BSUX  and  PCRE2_EX-
        TRA_ALT_BSUX options do not apply to replacement strings.


-       The second effect of setting PCRE2_SUBSTITUTE_EXTENDED is to  add  more
-       flexibility  to  capture  group  substitution. The syntax is similar to
+       The  second  effect of setting PCRE2_SUBSTITUTE_EXTENDED is to add more
+       flexibility to capture group substitution. The  syntax  is  similar  to
        that used by Bash:


          ${<n>:-<string>}
          ${<n>:+<string1>:<string2>}


-       As before, <n> may be a group number or a name. The first  form  speci-
-       fies  a  default  value. If group <n> is set, its value is inserted; if
-       not, <string> is expanded and the  result  inserted.  The  second  form
-       specifies  strings that are expanded and inserted when group <n> is set
-       or unset, respectively. The first form is just a  convenient  shorthand
+       As  before,  <n> may be a group number or a name. The first form speci-
+       fies a default value. If group <n> is set, its value  is  inserted;  if
+       not,  <string>  is  expanded  and  the result inserted. The second form
+       specifies strings that are expanded and inserted when group <n> is  set
+       or  unset,  respectively. The first form is just a convenient shorthand
        for


          ${<n>:+${<n>}:<string>}


-       Backslash  can  be  used to escape colons and closing curly brackets in
-       the replacement strings. A change of the case forcing  state  within  a
-       replacement  string  remains  in  force  afterwards,  as  shown in this
+       Backslash can be used to escape colons and closing  curly  brackets  in
+       the  replacement  strings.  A change of the case forcing state within a
+       replacement string remains  in  force  afterwards,  as  shown  in  this
        pcre2test example:


          /(some)?(body)/substitute_extended,replace=${1:+\U:\L}HeLLo
@@ -3402,8 +3409,8 @@
              somebody
           1: HELLO


-       The PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these  extended
-       substitutions.  However,  PCRE2_SUBSTITUTE_UNKNOWN_UNSET does cause un-
+       The  PCRE2_SUBSTITUTE_UNSET_EMPTY option does not affect these extended
+       substitutions. However, PCRE2_SUBSTITUTE_UNKNOWN_UNSET does  cause  un-
        known groups in the extended syntax forms to be treated as unset.


        If  PCRE2_SUBSTITUTE_LITERAL  is  set,  PCRE2_SUBSTITUTE_UNKNOWN_UNSET,
@@ -3412,8 +3419,8 @@


    Substitution errors


-       In the event of an error, pcre2_substitute() returns a  negative  error
-       code.  Except for PCRE2_ERROR_NOMATCH (which is never returned), errors
+       In  the  event of an error, pcre2_substitute() returns a negative error
+       code. Except for PCRE2_ERROR_NOMATCH (which is never returned),  errors
        from pcre2_match() are passed straight back.


        PCRE2_ERROR_NOSUBSTRING is returned for a non-existent substring inser-
@@ -3420,29 +3427,29 @@
        tion, unless PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set.


        PCRE2_ERROR_UNSET is returned for an unset substring insertion (includ-
-       ing an unknown substring when  PCRE2_SUBSTITUTE_UNKNOWN_UNSET  is  set)
-       when  the simple (non-extended) syntax is used and PCRE2_SUBSTITUTE_UN-
+       ing  an  unknown  substring when PCRE2_SUBSTITUTE_UNKNOWN_UNSET is set)
+       when the simple (non-extended) syntax is used and  PCRE2_SUBSTITUTE_UN-
        SET_EMPTY is not set.


-       PCRE2_ERROR_NOMEMORY is returned  if  the  output  buffer  is  not  big
+       PCRE2_ERROR_NOMEMORY  is  returned  if  the  output  buffer  is not big
        enough. If the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option is set, the size
-       of buffer that is needed is returned via outlengthptr. Note  that  this
+       of  buffer  that is needed is returned via outlengthptr. Note that this
        does not happen by default.


        PCRE2_ERROR_NULL is returned if PCRE2_SUBSTITUTE_MATCHED is set but the
        match_data argument is NULL.


-       PCRE2_ERROR_BADREPLACEMENT is used for miscellaneous syntax  errors  in
-       the  replacement  string,  with  more particular errors being PCRE2_ER-
+       PCRE2_ERROR_BADREPLACEMENT  is  used for miscellaneous syntax errors in
+       the replacement string, with more  particular  errors  being  PCRE2_ER-
        ROR_BADREPESCAPE (invalid escape sequence), PCRE2_ERROR_REPMISSINGBRACE
-       (closing  curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION (syntax
-       error in extended group substitution),  and  PCRE2_ERROR_BADSUBSPATTERN
+       (closing curly bracket not found), PCRE2_ERROR_BADSUBSTITUTION  (syntax
+       error  in  extended group substitution), and PCRE2_ERROR_BADSUBSPATTERN
        (the pattern match ended before it started or the match started earlier
-       than the current position in the subject, which can  happen  if  \K  is
+       than  the  current  position  in the subject, which can happen if \K is
        used in an assertion).


        As for all PCRE2 errors, a text message that describes the error can be
-       obtained by calling the pcre2_get_error_message()  function  (see  "Ob-
+       obtained  by  calling  the pcre2_get_error_message() function (see "Ob-
        taining a textual error message" above).


    Substitution callouts
@@ -3451,15 +3458,15 @@
          int (*callout_function)(pcre2_substitute_callout_block *, void *),
          void *callout_data);


-       The  pcre2_set_substitution_callout() function can be used to specify a
-       callout function for pcre2_substitute(). This information is passed  in
+       The pcre2_set_substitution_callout() function can be used to specify  a
+       callout  function for pcre2_substitute(). This information is passed in
        a match context. The callout function is called after each substitution
        has been processed, but it can cause the replacement not to happen. The
-       callout  function is not called for simulated substitutions that happen
+       callout function is not called for simulated substitutions that  happen
        as a result of the PCRE2_SUBSTITUTE_OVERFLOW_LENGTH option.


        The first argument of the callout function is a pointer to a substitute
-       callout  block structure, which contains the following fields, not nec-
+       callout block structure, which contains the following fields, not  nec-
        essarily in this order:


          uint32_t    version;
@@ -3470,9 +3477,9 @@
          uint32_t    oveccount;
          PCRE2_SIZE  output_offsets[2];


-       The version field contains the version number of the block format.  The
-       current  version  is  0.  The version number will increase in future if
-       more fields are added, but the intention is never to remove any of  the
+       The  version field contains the version number of the block format. The
+       current version is 0. The version number will  increase  in  future  if
+       more  fields are added, but the intention is never to remove any of the
        existing fields.


        The subscount field is the number of the current match. It is 1 for the
@@ -3479,25 +3486,25 @@
        first callout, 2 for the second, and so on. The input and output point-
        ers are copies of the values passed to pcre2_substitute().


-       The  ovector  field points to the ovector, which contains the result of
+       The ovector field points to the ovector, which contains the  result  of
        the most recent match. The oveccount field contains the number of pairs
        that are set in the ovector, and is always greater than zero.


-       The  output_offsets  vector  contains the offsets of the replacement in
-       the output string. This has already been processed for dollar  and  (if
+       The output_offsets vector contains the offsets of  the  replacement  in
+       the  output  string. This has already been processed for dollar and (if
        requested) backslash substitutions as described above.


-       The  second  argument  of  the  callout function is the value passed as
-       callout_data when the function was registered. The  value  returned  by
+       The second argument of the callout function  is  the  value  passed  as
+       callout_data  when  the  function was registered. The value returned by
        the callout function is interpreted as follows:


-       If  the  value is zero, the replacement is accepted, and, if PCRE2_SUB-
-       STITUTE_GLOBAL is set, processing continues with a search for the  next
-       match.  If  the  value  is not zero, the current replacement is not ac-
-       cepted. If the value is greater than zero,  processing  continues  when
-       PCRE2_SUBSTITUTE_GLOBAL  is set. Otherwise (the value is less than zero
-       or PCRE2_SUBSTITUTE_GLOBAL is not set), the the rest of  the  input  is
-       copied  to the output and the call to pcre2_substitute() exits, return-
+       If the value is zero, the replacement is accepted, and,  if  PCRE2_SUB-
+       STITUTE_GLOBAL  is set, processing continues with a search for the next
+       match. If the value is not zero, the current  replacement  is  not  ac-
+       cepted.  If  the  value is greater than zero, processing continues when
+       PCRE2_SUBSTITUTE_GLOBAL is set. Otherwise (the value is less than  zero
+       or  PCRE2_SUBSTITUTE_GLOBAL  is  not set), the the rest of the input is
+       copied to the output and the call to pcre2_substitute() exits,  return-
        ing the number of matches so far.



@@ -3506,56 +3513,56 @@
        int pcre2_substring_nametable_scan(const pcre2_code *code,
          PCRE2_SPTR name, PCRE2_SPTR *first, PCRE2_SPTR *last);


-       When a pattern is compiled with the PCRE2_DUPNAMES  option,  names  for
-       capture  groups  are not required to be unique. Duplicate names are al-
-       ways allowed for groups with the same number, created by using the  (?|
+       When  a  pattern  is compiled with the PCRE2_DUPNAMES option, names for
+       capture groups are not required to be unique. Duplicate names  are  al-
+       ways  allowed for groups with the same number, created by using the (?|
        feature. Indeed, if such groups are named, they are required to use the
        same names.


-       Normally, patterns that use duplicate names are such that  in  any  one
-       match,  only  one of each set of identically-named groups participates.
+       Normally,  patterns  that  use duplicate names are such that in any one
+       match, only one of each set of identically-named  groups  participates.
        An example is shown in the pcre2pattern documentation.


-       When  duplicates   are   present,   pcre2_substring_copy_byname()   and
-       pcre2_substring_get_byname()  return  the first substring corresponding
-       to the given name that is set. Only if none are set is  PCRE2_ERROR_UN-
-       SET  is  returned.  The pcre2_substring_number_from_name() function re-
-       turns the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are  duplicate
+       When   duplicates   are   present,   pcre2_substring_copy_byname()  and
+       pcre2_substring_get_byname() return the first  substring  corresponding
+       to  the given name that is set. Only if none are set is PCRE2_ERROR_UN-
+       SET is returned. The  pcre2_substring_number_from_name()  function  re-
+       turns  the error PCRE2_ERROR_NOUNIQUESUBSTRING when there are duplicate
        names.


-       If  you want to get full details of all captured substrings for a given
-       name, you must use the pcre2_substring_nametable_scan()  function.  The
-       first  argument is the compiled pattern, and the second is the name. If
-       the third and fourth arguments are NULL, the function returns  a  group
+       If you want to get full details of all captured substrings for a  given
+       name,  you  must use the pcre2_substring_nametable_scan() function. The
+       first argument is the compiled pattern, and the second is the name.  If
+       the  third  and fourth arguments are NULL, the function returns a group
        number for a unique name, or PCRE2_ERROR_NOUNIQUESUBSTRING otherwise.


        When the third and fourth arguments are not NULL, they must be pointers
-       to variables that are updated by the function. After it has  run,  they
+       to  variables  that 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, and the function returns the length of each entry  in  code
-       units.  In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there are
+       given  name,  and the function returns the length of each entry in code
+       units. In both cases, PCRE2_ERROR_NOSUBSTRING is returned if there  are
        no entries for the given name.


        The format of the name table is described above in the section entitled
-       Information  about  a  pattern.  Given all the relevant entries for the
-       name, you can extract each of their numbers,  and  hence  the  captured
+       Information about a pattern. Given all the  relevant  entries  for  the
+       name,  you  can  extract  each of their numbers, and hence the captured
        data.



FINDING ALL POSSIBLE MATCHES AT ONE POSITION

-       The  traditional  matching  function  uses a similar algorithm to Perl,
-       which stops when it finds the first match at a given point in the  sub-
+       The traditional matching function uses a  similar  algorithm  to  Perl,
+       which  stops when it finds the first match at a given point in the sub-
        ject. If you want to find all possible matches, or the longest possible
-       match at a given position,  consider  using  the  alternative  matching
-       function  (see  below) instead. If you cannot use the alternative func-
+       match  at  a  given  position,  consider using the alternative matching
+       function (see below) instead. If you cannot use the  alternative  func-
        tion, you can kludge it up by making use of the callout facility, which
        is described in the pcre2callout documentation.


        What you have to do is to insert a callout right at the end of the pat-
-       tern.  When your callout function is called, extract and save the  cur-
-       rent  matched  substring.  Then return 1, which forces pcre2_match() to
-       backtrack and try other alternatives. Ultimately, when it runs  out  of
+       tern.   When your callout function is called, extract and save the cur-
+       rent matched substring. Then return 1, which  forces  pcre2_match()  to
+       backtrack  and  try other alternatives. Ultimately, when it runs out of
        matches, pcre2_match() will yield PCRE2_ERROR_NOMATCH.



@@ -3567,26 +3574,26 @@
          pcre2_match_context *mcontext,
          int *workspace, PCRE2_SIZE wscount);


-       The  function  pcre2_dfa_match()  is  called  to match a subject string
-       against a compiled pattern, using a matching algorithm that  scans  the
+       The function pcre2_dfa_match() is called  to  match  a  subject  string
+       against  a  compiled pattern, using a matching algorithm that scans the
        subject string just once (not counting lookaround assertions), and does
-       not backtrack.  This has different characteristics to the normal  algo-
-       rithm,  and  is not compatible with Perl. Some of the features of PCRE2
-       patterns are not supported.  Nevertheless, there are  times  when  this
-       kind  of  matching  can be useful. For a discussion of the two matching
+       not  backtrack.  This has different characteristics to the normal algo-
+       rithm, and is not compatible with Perl. Some of the features  of  PCRE2
+       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 pcre2_dfa_match() does not sup-
        port, see the pcre2matching documentation.


-       The  arguments  for  the pcre2_dfa_match() function are the same as for
+       The arguments for the pcre2_dfa_match() function are the  same  as  for
        pcre2_match(), plus two extras. The ovector within the match data block
        is used in a different way, and this is described below. The other com-
-       mon arguments are used in the same way as for pcre2_match(),  so  their
+       mon  arguments  are used in the same way as for pcre2_match(), 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
+       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 is needed for patterns and subjects where there are a lot  of
+       workspace  is needed for patterns and subjects where there are a lot of
        potential matches.


        Here is an example of a simple call to pcre2_dfa_match():
@@ -3606,45 +3613,45 @@


    Option bits for pcre_dfa_match()


-       The  unused  bits of the options argument for pcre2_dfa_match() must be
-       zero.  The  only   bits   that   may   be   set   are   PCRE2_ANCHORED,
-       PCRE2_COPY_MATCHED_SUBJECT,  PCRE2_ENDANCHORED, PCRE2_NOTBOL, PCRE2_NO-
+       The unused bits of the options argument for pcre2_dfa_match()  must  be
+       zero.   The   only   bits   that   may   be   set  are  PCRE2_ANCHORED,
+       PCRE2_COPY_MATCHED_SUBJECT, PCRE2_ENDANCHORED, PCRE2_NOTBOL,  PCRE2_NO-
        TEOL,   PCRE2_NOTEMPTY,   PCRE2_NOTEMPTY_ATSTART,   PCRE2_NO_UTF_CHECK,
-       PCRE2_PARTIAL_HARD,    PCRE2_PARTIAL_SOFT,    PCRE2_DFA_SHORTEST,   and
-       PCRE2_DFA_RESTART. All but the last four of these are exactly the  same
+       PCRE2_PARTIAL_HARD,   PCRE2_PARTIAL_SOFT,    PCRE2_DFA_SHORTEST,    and
+       PCRE2_DFA_RESTART.  All but the last four of these are exactly the same
        as for pcre2_match(), so their description is not repeated here.


          PCRE2_PARTIAL_HARD
          PCRE2_PARTIAL_SOFT


-       These  have  the  same general effect as they do for pcre2_match(), but
-       the details are slightly different. When PCRE2_PARTIAL_HARD is set  for
-       pcre2_dfa_match(),  it  returns  PCRE2_ERROR_PARTIAL  if the end of the
+       These have the same general effect as they do  for  pcre2_match(),  but
+       the  details are slightly different. When PCRE2_PARTIAL_HARD is set for
+       pcre2_dfa_match(), it returns PCRE2_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 already been found. When PCRE2_PARTIAL_SOFT  is  set,  the
-       return  code  PCRE2_ERROR_NOMATCH is converted into PCRE2_ERROR_PARTIAL
-       if the end of the subject is  reached,  there  have  been  no  complete
+       matches  have  already  been found. When PCRE2_PARTIAL_SOFT is set, the
+       return code PCRE2_ERROR_NOMATCH is converted  into  PCRE2_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 por-
-       tion of the string that was inspected when the  longest  partial  match
+       tion  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
+       more  detailed  discussion  of partial and multi-segment matching, with
        examples, in the pcre2partial documentation.


          PCRE2_DFA_SHORTEST


-       Setting  the PCRE2_DFA_SHORTEST option causes the matching algorithm to
+       Setting the PCRE2_DFA_SHORTEST option causes the matching algorithm  to
        stop as soon as it has found one match. Because of the way the alterna-
-       tive  algorithm  works, this is necessarily the shortest possible match
+       tive algorithm works, this is necessarily the shortest  possible  match
        at the first possible matching point in the subject string.


          PCRE2_DFA_RESTART


-       When pcre2_dfa_match() returns a partial match, it is possible to  call
+       When  pcre2_dfa_match() returns a partial match, it is possible to call
        it again, with additional subject characters, and have it continue with
        the same match. The PCRE2_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
+       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
        pcre2partial documentation.


@@ -3652,8 +3659,8 @@

        When pcre2_dfa_match() succeeds, it may have matched more than one sub-
        string 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,
+       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


          <.*>
@@ -3668,80 +3675,80 @@
          <something> <something else>
          <something>


-       On success, the yield of the function is a number  greater  than  zero,
-       which  is  the  number  of  matched substrings. The offsets of the sub-
-       strings are returned in the ovector, and can be extracted by number  in
-       the  same way as for pcre2_match(), but the numbers bear no relation to
-       any capture groups that may exist in the pattern, because DFA  matching
+       On  success,  the  yield of the function is a number greater than zero,
+       which is the number of matched substrings.  The  offsets  of  the  sub-
+       strings  are returned in the ovector, and can be extracted by number in
+       the same way as for pcre2_match(), but the numbers bear no relation  to
+       any  capture groups that may exist in the pattern, because DFA matching
        does not support capturing.


-       Calls  to the convenience functions that extract substrings by name re-
+       Calls to the convenience functions that extract substrings by name  re-
        turn the error PCRE2_ERROR_DFA_UFUNC (unsupported function) if used af-
-       ter  a  DFA match. The convenience functions that extract substrings by
+       ter a DFA match. The convenience functions that extract  substrings  by
        number never return PCRE2_ERROR_NOSUBSTRING.


-       The matched strings are stored in  the  ovector  in  reverse  order  of
-       length;  that  is,  the longest matching string is first. If there were
-       too many matches to fit into the ovector, the yield of the function  is
+       The  matched  strings  are  stored  in  the ovector in reverse order of
+       length; that is, the longest matching string is first.  If  there  were
+       too  many matches to fit into the ovector, the yield of the function is
        zero, and the vector is filled with the longest matches.


-       NOTE:  PCRE2'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++". For DFA
-       matching, this means that only one possible match is found. If you  re-
+       NOTE: PCRE2'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++". For  DFA
+       matching,  this means that only one possible match is found. If you re-
        ally do want multiple matches in such cases, either use an ungreedy re-
-       peat such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when  com-
+       peat  such as "a\d+?" or set the PCRE2_NO_AUTO_POSSESS option when com-
        piling.


    Error returns from pcre2_dfa_match()


        The pcre2_dfa_match() function returns a negative number when it fails.
-       Many of the errors are the same  as  for  pcre2_match(),  as  described
+       Many  of  the  errors  are  the same as for pcre2_match(), as described
        above.  There are in addition the following errors that are specific to
        pcre2_dfa_match():


          PCRE2_ERROR_DFA_UITEM


-       This return is given if pcre2_dfa_match() encounters  an  item  in  the
-       pattern  that it does not support, for instance, the use of \C in a UTF
+       This  return  is  given  if pcre2_dfa_match() encounters an item in the
+       pattern that it does not support, for instance, the use of \C in a  UTF
        mode or a backreference.


          PCRE2_ERROR_DFA_UCOND


-       This return is given if pcre2_dfa_match() encounters a  condition  item
+       This  return  is given if pcre2_dfa_match() encounters a condition item
        that uses a backreference for the condition, or a test for recursion in
        a specific capture group. These are not supported.


          PCRE2_ERROR_DFA_UINVALID_UTF


-       This return is given if pcre2_dfa_match() is called for a pattern  that
-       was  compiled  with  PCRE2_MATCH_INVALID_UTF. This is not supported for
+       This  return is given if pcre2_dfa_match() is called for a pattern that
+       was compiled with PCRE2_MATCH_INVALID_UTF. This is  not  supported  for
        DFA matching.


          PCRE2_ERROR_DFA_WSSIZE


-       This return is given if pcre2_dfa_match() runs  out  of  space  in  the
+       This  return  is  given  if  pcre2_dfa_match() runs out of space in the
        workspace vector.


          PCRE2_ERROR_DFA_RECURSE


        When a recursion or subroutine call is processed, the matching function
-       calls itself recursively, using private  memory  for  the  ovector  and
-       workspace.   This  error  is given if the internal ovector is not large
-       enough. This should be extremely rare, as a  vector  of  size  1000  is
+       calls  itself  recursively,  using  private  memory for the ovector and
+       workspace.  This error is given if the internal ovector  is  not  large
+       enough.  This  should  be  extremely  rare, as a vector of size 1000 is
        used.


          PCRE2_ERROR_DFA_BADRESTART


-       When  pcre2_dfa_match()  is  called  with the PCRE2_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
+       When pcre2_dfa_match() is called  with  the  PCRE2_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

-       pcre2build(3),   pcre2callout(3),    pcre2demo(3),    pcre2matching(3),
+       pcre2build(3),    pcre2callout(3),    pcre2demo(3),   pcre2matching(3),
        pcre2partial(3), pcre2posix(3), pcre2sample(3), pcre2unicode(3).



@@ -3754,7 +3761,7 @@

REVISION

-       Last updated: 22 January 2020
+       Last updated: 16 February 2020
        Copyright (c) 1997-2020 University of Cambridge.
 ------------------------------------------------------------------------------