Regex: Update PCRE to v8.35.
I was über lazy at first, so took libs from SM. But actually it's quite easy to compile, so let's update to latest version \o/.
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Arkshine
@ -64,23 +64,63 @@ it is processed as if it were
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<br>
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<br>
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Notice that there is a callout before and after each parenthesis and
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alternation bar. Automatic callouts can be used for tracking the progress of
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pattern matching. The
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<a href="pcretest.html"><b>pcretest</b></a>
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command has an option that sets automatic callouts; when it is used, the output
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indicates how the pattern is matched. This is useful information when you are
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trying to optimize the performance of a particular pattern.
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alternation bar. If the pattern contains a conditional group whose condition is
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an assertion, an automatic callout is inserted immediately before the
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condition. Such a callout may also be inserted explicitly, for example:
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<pre>
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(?(?C9)(?=a)ab|de)
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</pre>
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This applies only to assertion conditions (because they are themselves
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independent groups).
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</P>
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<P>
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The use of callouts in a pattern makes it ineligible for optimization by the
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just-in-time compiler. Studying such a pattern with the PCRE_STUDY_JIT_COMPILE
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option always fails.
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Automatic callouts can be used for tracking the progress of pattern matching.
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The
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<a href="pcretest.html"><b>pcretest</b></a>
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program has a pattern qualifier (/C) that sets automatic callouts; when it is
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used, the output indicates how the pattern is being matched. This is useful
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information when you are trying to optimize the performance of a particular
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pattern.
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</P>
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<br><a name="SEC3" href="#TOC1">MISSING CALLOUTS</a><br>
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<P>
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You should be aware that, because of optimizations in the way PCRE matches
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patterns by default, callouts sometimes do not happen. For example, if the
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pattern is
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You should be aware that, because of optimizations in the way PCRE compiles and
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matches patterns, callouts sometimes do not happen exactly as you might expect.
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</P>
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<P>
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At compile time, PCRE "auto-possessifies" repeated items when it knows that
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what follows cannot be part of the repeat. For example, a+[bc] is compiled as
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if it were a++[bc]. The <b>pcretest</b> output when this pattern is anchored and
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then applied with automatic callouts to the string "aaaa" is:
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<pre>
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--->aaaa
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+0 ^ ^
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+1 ^ a+
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+3 ^ ^ [bc]
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No match
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</pre>
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This indicates that when matching [bc] fails, there is no backtracking into a+
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and therefore the callouts that would be taken for the backtracks do not occur.
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You can disable the auto-possessify feature by passing PCRE_NO_AUTO_POSSESS
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to <b>pcre_compile()</b>, or starting the pattern with (*NO_AUTO_POSSESS). If
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this is done in <b>pcretest</b> (using the /O qualifier), the output changes to
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this:
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<pre>
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--->aaaa
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+0 ^ ^
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+1 ^ a+
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+3 ^ ^ [bc]
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+3 ^ ^ [bc]
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+3 ^ ^ [bc]
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+3 ^^ [bc]
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No match
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</pre>
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This time, when matching [bc] fails, the matcher backtracks into a+ and tries
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again, repeatedly, until a+ itself fails.
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</P>
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<P>
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Other optimizations that provide fast "no match" results also affect callouts.
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For example, if the pattern is
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<pre>
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ab(?C4)cd
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</pre>
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@ -104,11 +144,11 @@ callouts such as the example above are obeyed.
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<br><a name="SEC4" href="#TOC1">THE CALLOUT INTERFACE</a><br>
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<P>
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During matching, when PCRE reaches a callout point, the external function
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defined by <i>pcre_callout</i> or <i>pcre[16|32]_callout</i> is called
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(if it is set). This applies to both normal and DFA matching. The only
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argument to the callout function is a pointer to a <b>pcre_callout</b>
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or <b>pcre[16|32]_callout</b> block.
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These structures contains the following fields:
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defined by <i>pcre_callout</i> or <i>pcre[16|32]_callout</i> is called (if it is
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set). This applies to both normal and DFA matching. The only argument to the
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callout function is a pointer to a <b>pcre_callout</b> or
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<b>pcre[16|32]_callout</b> block. These structures contains the following
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fields:
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<pre>
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int <i>version</i>;
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int <i>callout_number</i>;
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@ -141,10 +181,10 @@ automatically generated callouts).
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<P>
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The <i>offset_vector</i> field is a pointer to the vector of offsets that was
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passed by the caller to the matching function. When <b>pcre_exec()</b> or
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<b>pcre[16|32]_exec()</b> is used, the contents can be inspected, in order to extract
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substrings that have been matched so far, in the same way as for extracting
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substrings after a match has completed. For the DFA matching functions, this
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field is not useful.
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<b>pcre[16|32]_exec()</b> is used, the contents can be inspected, in order to
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extract substrings that have been matched so far, in the same way as for
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extracting substrings after a match has completed. For the DFA matching
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functions, this field is not useful.
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</P>
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<P>
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The <i>subject</i> and <i>subject_length</i> fields contain copies of the values
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@ -171,8 +211,10 @@ functions are used, because they do not support captured substrings.
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</P>
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<P>
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The <i>capture_last</i> field contains the number of the most recently captured
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substring. If no substrings have been captured, its value is -1. This is always
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the case for the DFA matching functions.
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substring. However, when a recursion exits, the value reverts to what it was
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outside the recursion, as do the values of all captured substrings. If no
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substrings have been captured, the value of <i>capture_last</i> is -1. This is
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always the case for the DFA matching functions.
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</P>
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<P>
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The <i>callout_data</i> field contains a value that is passed to a matching
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@ -203,11 +245,12 @@ same callout number. However, they are set for all callouts.
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</P>
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<P>
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The <i>mark</i> field is present from version 2 of the callout structure. In
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callouts from <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> it contains a pointer to
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the zero-terminated name of the most recently passed (*MARK), (*PRUNE), or
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(*THEN) item in the match, or NULL if no such items have been passed. Instances
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of (*PRUNE) or (*THEN) without a name do not obliterate a previous (*MARK). In
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callouts from the DFA matching functions this field always contains NULL.
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callouts from <b>pcre_exec()</b> or <b>pcre[16|32]_exec()</b> it contains a
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pointer to the zero-terminated name of the most recently passed (*MARK),
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(*PRUNE), or (*THEN) item in the match, or NULL if no such items have been
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passed. Instances of (*PRUNE) or (*THEN) without a name do not obliterate a
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previous (*MARK). In callouts from the DFA matching functions this field always
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contains NULL.
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</P>
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<br><a name="SEC5" href="#TOC1">RETURN VALUES</a><br>
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<P>
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@ -234,9 +277,9 @@ Cambridge CB2 3QH, England.
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</P>
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<br><a name="SEC7" href="#TOC1">REVISION</a><br>
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<P>
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Last updated: 24 June 2012
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Last updated: 12 November 2013
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<br>
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Copyright © 1997-2012 University of Cambridge.
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Copyright © 1997-2013 University of Cambridge.
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<br>
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<p>
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Return to the <a href="index.html">PCRE index page</a>.
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