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Update documentation for scan_substring; also some code trailing space tidies

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Philip Hazel
2024-08-30 17:31:55 +01:00
parent bb2b1d03fd
commit 7a0eda1f66
18 changed files with 537 additions and 266 deletions
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doc/html/pcre2matching.html
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@@ -27,7 +27,7 @@ please consult the man page, in case the conversion went wrong.
This document describes the two different algorithms that are available in
PCRE2 for matching a compiled regular expression against a given subject
string. The "standard" algorithm is the one provided by the <b>pcre2_match()</b>
function. This works in the same as Perl's matching function, and provide a
function. This works in the same as Perl's matching function, and provides a
Perl-compatible matching operation. The just-in-time (JIT) optimization that is
described in the
<a href="pcre2jit.html"><b>pcre2jit</b></a>
@@ -42,7 +42,7 @@ these are described below.
<P>
When there is only one possible way in which a given subject string can match a
pattern, the two algorithms give the same answer. A difference arises, however,
when there are multiple possibilities. For example, if the pattern
when there are multiple possibilities. For example, if the anchored pattern
<pre>
^&#60;.*&#62;
</pre>
@@ -115,9 +115,9 @@ algorithm after the first match (which is necessarily the shortest) is found.
</P>
<P>
Note that the size of vector needed to contain all the results depends on the
number of simultaneous matches, not on the number of parentheses in the
pattern. Using <b>pcre2_match_data_create_from_pattern()</b> to create the match
data block is therefore not advisable when doing DFA matching.
number of simultaneous matches, not on the number of capturing parentheses in
the pattern. Using <b>pcre2_match_data_create_from_pattern()</b> to create the
match data block is therefore not advisable when doing DFA matching.
</P>
<P>
Note also that all the matches that are found start at the same point in the
@@ -166,37 +166,43 @@ possibilities, and PCRE2's implementation of this algorithm does not attempt to
do this. This means that no captured substrings are available.
</P>
<P>
3. Because no substrings are captured, backreferences within the pattern are
not supported.
3. Because no substrings are captured, a number of related features are not
available:
<br>
<br>
(a) Backreferences;
<br>
<br>
(b) Conditional expressions that use a backreference as the condition or test
for a specific group recursion;
<br>
<br>
(c) Script runs;
<br>
<br>
(d) Scan substring assertions.
</P>
<P>
4. For the same reason, conditional expressions that use a backreference as the
condition or test for a specific group recursion are not supported.
</P>
<P>
5. Again for the same reason, script runs are not supported.
</P>
<P>
6. Because many paths through the tree may be active, the \K escape sequence,
4. Because many paths through the tree may be active, the \K escape sequence,
which resets the start of the match when encountered (but may be on some paths
and not on others), is not supported.
</P>
<P>
7. Callouts are supported, but the value of the <i>capture_top</i> field is
5. Callouts are supported, but the value of the <i>capture_top</i> field is
always 1, and the value of the <i>capture_last</i> field is always 0.
</P>
<P>
8. The \C escape sequence, which (in the standard algorithm) always matches a
single code unit, even in a UTF mode, is not supported in these modes, because
6. The \C escape sequence, which (in the standard algorithm) always matches a
single code unit, even in a UTF mode, is not supported in UTF modes because
the alternative algorithm moves through the subject string one character (not
code unit) at a time, for all active paths through the tree.
</P>
<P>
9. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) are not
7. Except for (*FAIL), the backtracking control verbs such as (*PRUNE) are not
supported. (*FAIL) is supported, and behaves like a failing negative assertion.
</P>
<P>
10. The PCRE2_MATCH_INVALID_UTF option for <b>pcre2_compile()</b> is not
8. The PCRE2_MATCH_INVALID_UTF option for <b>pcre2_compile()</b> is not
supported by <b>pcre2_dfa_match()</b>.
</P>
<br><a name="SEC5" href="#TOC1">ADVANTAGES OF THE ALTERNATIVE ALGORITHM</a><br>
@@ -223,15 +229,18 @@ because it has to search for all possible matches, but is also because it is
less susceptible to optimization.
</P>
<P>
2. Capturing parentheses, backreferences, script runs, and matching within
invalid UTF string are not supported.
2. Capturing parentheses and other features such as backreferences that rely on
them are not supported.
</P>
<P>
3. Although atomic groups are supported, their use does not provide the
3. Matching within invalid UTF strings is not supported.
</P>
<P>
4. Although atomic groups are supported, their use does not provide the
performance advantage that it does for the standard algorithm.
</P>
<P>
4. JIT optimization is not supported.
5. JIT optimization is not supported.
</P>
<br><a name="SEC7" href="#TOC1">AUTHOR</a><br>
<P>
@@ -244,7 +253,7 @@ Cambridge, England.
</P>
<br><a name="SEC8" href="#TOC1">REVISION</a><br>
<P>
Last updated: 19 January 2024
Last updated: 30 August 2024
<br>
Copyright &copy; 1997-2024 University of Cambridge.
<br>