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1 nigel 77 <html>
2     <head>
3     <title>pcrecpp specification</title>
4     </head>
5     <body bgcolor="#FFFFFF" text="#00005A" link="#0066FF" alink="#3399FF" vlink="#2222BB">
6     <h1>pcrecpp man page</h1>
7     <p>
8     Return to the <a href="index.html">PCRE index page</a>.
9     </p>
10     <p>
11     This page is part of the PCRE HTML documentation. It was generated automatically
12     from the original man page. If there is any nonsense in it, please consult the
13     man page, in case the conversion went wrong.
14     <br>
15     <ul>
16     <li><a name="TOC1" href="#SEC1">SYNOPSIS OF C++ WRAPPER</a>
17     <li><a name="TOC2" href="#SEC2">DESCRIPTION</a>
18     <li><a name="TOC3" href="#SEC3">MATCHING INTERFACE</a>
19 nigel 93 <li><a name="TOC4" href="#SEC4">QUOTING METACHARACTERS</a>
20     <li><a name="TOC5" href="#SEC5">PARTIAL MATCHES</a>
21     <li><a name="TOC6" href="#SEC6">UTF-8 AND THE MATCHING INTERFACE</a>
23     <li><a name="TOC8" href="#SEC8">SCANNING TEXT INCREMENTALLY</a>
24     <li><a name="TOC9" href="#SEC9">PARSING HEX/OCTAL/C-RADIX NUMBERS</a>
25     <li><a name="TOC10" href="#SEC10">REPLACING PARTS OF STRINGS</a>
26     <li><a name="TOC11" href="#SEC11">AUTHOR</a>
27 nigel 77 </ul>
28     <br><a name="SEC1" href="#TOC1">SYNOPSIS OF C++ WRAPPER</a><br>
29     <P>
30     <b>#include &#60;pcrecpp.h&#62;</b>
31     </P>
32     <P>
33     </P>
34     <br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
35     <P>
36 nigel 81 The C++ wrapper for PCRE was provided by Google Inc. Some additional
37     functionality was added by Giuseppe Maxia. This brief man page was constructed
38     from the notes in the <i>pcrecpp.h</i> file, which should be consulted for
39     further details.
40 nigel 77 </P>
41     <br><a name="SEC3" href="#TOC1">MATCHING INTERFACE</a><br>
42     <P>
43     The "FullMatch" operation checks that supplied text matches a supplied pattern
44     exactly. If pointer arguments are supplied, it copies matched sub-strings that
45     match sub-patterns into them.
46     <pre>
47     Example: successful match
48     pcrecpp::RE re("h.*o");
49     re.FullMatch("hello");
51     Example: unsuccessful match (requires full match):
52     pcrecpp::RE re("e");
53     !re.FullMatch("hello");
55     Example: creating a temporary RE object:
56     pcrecpp::RE("h.*o").FullMatch("hello");
57     </pre>
58     You can pass in a "const char*" or a "string" for "text". The examples below
59     tend to use a const char*. You can, as in the different examples above, store
60     the RE object explicitly in a variable or use a temporary RE object. The
61     examples below use one mode or the other arbitrarily. Either could correctly be
62     used for any of these examples.
63     </P>
64     <P>
65     You must supply extra pointer arguments to extract matched subpieces.
66     <pre>
67     Example: extracts "ruby" into "s" and 1234 into "i"
68     int i;
69     string s;
70     pcrecpp::RE re("(\\w+):(\\d+)");
71     re.FullMatch("ruby:1234", &s, &i);
73     Example: does not try to extract any extra sub-patterns
74     re.FullMatch("ruby:1234", &s);
76     Example: does not try to extract into NULL
77     re.FullMatch("ruby:1234", NULL, &i);
79     Example: integer overflow causes failure
80     !re.FullMatch("ruby:1234567891234", NULL, &i);
82     Example: fails because there aren't enough sub-patterns:
83     !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
85     Example: fails because string cannot be stored in integer
86     !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
87     </pre>
88     The provided pointer arguments can be pointers to any scalar numeric
89     type, or one of:
90     <pre>
91     string (matched piece is copied to string)
92     StringPiece (StringPiece is mutated to point to matched piece)
93     T (where "bool T::ParseFrom(const char*, int)" exists)
94     NULL (the corresponding matched sub-pattern is not copied)
95     </pre>
96     The function returns true iff all of the following conditions are satisfied:
97     <pre>
98     a. "text" matches "pattern" exactly;
100     b. The number of matched sub-patterns is &#62;= number of supplied
101     pointers;
103     c. The "i"th argument has a suitable type for holding the
104     string captured as the "i"th sub-pattern. If you pass in
105     NULL for the "i"th argument, or pass fewer arguments than
106     number of sub-patterns, "i"th captured sub-pattern is
107     ignored.
108     </pre>
109 nigel 93 CAVEAT: An optional sub-pattern that does not exist in the matched
110     string is assigned the empty string. Therefore, the following will
111     return false (because the empty string is not a valid number):
112     <pre>
113     int number;
114     pcrecpp::RE::FullMatch("abc", "[a-z]+(\\d+)?", &number);
115     </pre>
116 nigel 77 The matching interface supports at most 16 arguments per call.
117     If you need more, consider using the more general interface
118     <b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for
119     <b>DoMatch</b>.
120     </P>
121 nigel 93 <br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br>
122 nigel 77 <P>
123 nigel 93 You can use the "QuoteMeta" operation to insert backslashes before all
124     potentially meaningful characters in a string. The returned string, used as a
125     regular expression, will exactly match the original string.
126     <pre>
127     Example:
128     string quoted = RE::QuoteMeta(unquoted);
129     </pre>
130     Note that it's legal to escape a character even if it has no special meaning in
131     a regular expression -- so this function does that. (This also makes it
132     identical to the perl function of the same name; see "perldoc -f quotemeta".)
133     For example, "1.5-2.0?" becomes "1\.5\-2\.0\?".
134     </P>
135     <br><a name="SEC5" href="#TOC1">PARTIAL MATCHES</a><br>
136     <P>
137 nigel 77 You can use the "PartialMatch" operation when you want the pattern
138     to match any substring of the text.
139     <pre>
140     Example: simple search for a string:
141     pcrecpp::RE("ell").PartialMatch("hello");
143     Example: find first number in a string:
144     int number;
145     pcrecpp::RE re("(\\d+)");
146     re.PartialMatch("x*100 + 20", &number);
147     assert(number == 100);
148     </PRE>
149     </P>
150 nigel 93 <br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
151 nigel 77 <P>
152     By default, pattern and text are plain text, one byte per character. The UTF8
153     flag, passed to the constructor, causes both pattern and string to be treated
154     as UTF-8 text, still a byte stream but potentially multiple bytes per
155     character. In practice, the text is likelier to be UTF-8 than the pattern, but
156     the match returned may depend on the UTF8 flag, so always use it when matching
157     UTF8 text. For example, "." will match one byte normally but with UTF8 set may
158     match up to three bytes of a multi-byte character.
159     <pre>
160     Example:
161     pcrecpp::RE_Options options;
162     options.set_utf8();
163     pcrecpp::RE re(utf8_pattern, options);
164     re.FullMatch(utf8_string);
166     Example: using the convenience function UTF8():
167     pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
168     re.FullMatch(utf8_string);
169     </pre>
170     NOTE: The UTF8 flag is ignored if pcre was not configured with the
171     <pre>
172     --enable-utf8 flag.
173     </PRE>
174     </P>
175 nigel 93 <br><a name="SEC7" href="#TOC1">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a><br>
176 nigel 77 <P>
177 nigel 81 PCRE defines some modifiers to change the behavior of the regular expression
178     engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
179     pass such modifiers to a RE class. Currently, the following modifiers are
180     supported:
181     <pre>
182     modifier description Perl corresponding
184     PCRE_CASELESS case insensitive match /i
185     PCRE_MULTILINE multiple lines match /m
186     PCRE_DOTALL dot matches newlines /s
187     PCRE_DOLLAR_ENDONLY $ matches only at end N/A
188     PCRE_EXTRA strict escape parsing N/A
189     PCRE_EXTENDED ignore whitespaces /x
190     PCRE_UTF8 handles UTF8 chars built-in
191     PCRE_UNGREEDY reverses * and *? N/A
192     PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
193     </pre>
194     (*) Both Perl and PCRE allow non capturing parentheses by means of the
195     "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
196     capture, while (ab|cd) does.
197     </P>
198     <P>
199     For a full account on how each modifier works, please check the
200     PCRE API reference page.
201     </P>
202     <P>
203     For each modifier, there are two member functions whose name is made
204     out of the modifier in lowercase, without the "PCRE_" prefix. For
205     instance, PCRE_CASELESS is handled by
206     <pre>
207     bool caseless()
208     </pre>
209     which returns true if the modifier is set, and
210     <pre>
211     RE_Options & set_caseless(bool)
212     </pre>
213 nigel 87 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
214 nigel 81 accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member
215     functions. Setting <i>match_limit</i> to a non-zero value will limit the
216     execution of pcre to keep it from doing bad things like blowing the stack or
217     taking an eternity to return a result. A value of 5000 is good enough to stop
218     stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables
219 nigel 87 match limiting. Alternatively, you can call <b>match_limit_recursion()</b>
220     which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
221     recurses. <b>match_limit()</b> limits the number of matches PCRE does;
222     <b>match_limit_recursion()</b> limits the depth of internal recursion, and
223     therefore the amount of stack that is used.
224 nigel 81 </P>
225     <P>
226     Normally, to pass one or more modifiers to a RE class, you declare
227     a <i>RE_Options</i> object, set the appropriate options, and pass this
228     object to a RE constructor. Example:
229     <pre>
230     RE_options opt;
231     opt.set_caseless(true);
232     if (RE("HELLO", opt).PartialMatch("hello world")) ...
233     </pre>
234     RE_options has two constructors. The default constructor takes no arguments and
235     creates a set of flags that are off by default. The optional parameter
236     <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
237     This lets you do
238     <pre>
239     RE(pattern,
240     RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
241     </pre>
242     However, new code is better off doing
243     <pre>
244     RE(pattern,
245     RE_Options().set_caseless(true).set_multiline(true))
246     .PartialMatch(str);
247     </pre>
248     If you are going to pass one of the most used modifiers, there are some
249     convenience functions that return a RE_Options class with the
250     appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
251     <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
252     </P>
253     <P>
254     If you need to set several options at once, and you don't want to go through
255     the pains of declaring a RE_Options object and setting several options, there
256     is a parallel method that give you such ability on the fly. You can concatenate
257     several <b>set_xxxxx()</b> member functions, since each of them returns a
258     reference to its class object. For example, to pass PCRE_CASELESS,
259     PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
260     <pre>
261     RE(" ^ xyz \\s+ .* blah$",
262     RE_Options()
263     .set_caseless(true)
264     .set_extended(true)
265     .set_multiline(true)).PartialMatch(sometext);
267     </PRE>
268     </P>
269 nigel 93 <br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
270 nigel 81 <P>
271 nigel 77 The "Consume" operation may be useful if you want to repeatedly
272     match regular expressions at the front of a string and skip over
273     them as they match. This requires use of the "StringPiece" type,
274     which represents a sub-range of a real string. Like RE, StringPiece
275     is defined in the pcrecpp namespace.
276     <pre>
277     Example: read lines of the form "var = value" from a string.
278     string contents = ...; // Fill string somehow
279     pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
280     </PRE>
281     </P>
282     <P>
283     <pre>
284     string var;
285     int value;
286     pcrecpp::RE re("(\\w+) = (\\d+)\n");
287     while (re.Consume(&input, &var, &value)) {
288     ...;
289     }
290     </pre>
291     Each successful call to "Consume" will set "var/value", and also
292     advance "input" so it points past the matched text.
293     </P>
294     <P>
295     The "FindAndConsume" operation is similar to "Consume" but does not
296     anchor your match at the beginning of the string. For example, you
297     could extract all words from a string by repeatedly calling
298     <pre>
299     pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
300     </PRE>
301     </P>
302 nigel 93 <br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
303 nigel 77 <P>
304     By default, if you pass a pointer to a numeric value, the
305     corresponding text is interpreted as a base-10 number. You can
306     instead wrap the pointer with a call to one of the operators Hex(),
307     Octal(), or CRadix() to interpret the text in another base. The
308     CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
309     prefixes, but defaults to base-10.
310     <pre>
311     Example:
312     int a, b, c, d;
313     pcrecpp::RE re("(.*) (.*) (.*) (.*)");
314     re.FullMatch("100 40 0100 0x40",
315     pcrecpp::Octal(&a), pcrecpp::Hex(&b),
316     pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
317     </pre>
318     will leave 64 in a, b, c, and d.
319     </P>
320 nigel 93 <br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
321 nigel 77 <P>
322     You can replace the first match of "pattern" in "str" with "rewrite".
323     Within "rewrite", backslash-escaped digits (\1 to \9) can be
324     used to insert text matching corresponding parenthesized group
325     from the pattern. \0 in "rewrite" refers to the entire matching
326     text. For example:
327     <pre>
328     string s = "yabba dabba doo";
329     pcrecpp::RE("b+").Replace("d", &s);
330     </pre>
331     will leave "s" containing "yada dabba doo". The result is true if the pattern
332     matches and a replacement occurs, false otherwise.
333     </P>
334     <P>
335     <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
336     occurrences of the pattern in the string with the rewrite. Replacements are
337     not subject to re-matching. For example:
338     <pre>
339     string s = "yabba dabba doo";
340     pcrecpp::RE("b+").GlobalReplace("d", &s);
341     </pre>
342     will leave "s" containing "yada dada doo". It returns the number of
343     replacements made.
344     </P>
345     <P>
346     <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
347     "rewrite" is copied into "out" (an additional argument) with substitutions.
348     The non-matching portions of "text" are ignored. Returns true iff a match
349     occurred and the extraction happened successfully; if no match occurs, the
350     string is left unaffected.
351     </P>
352 nigel 93 <br><a name="SEC11" href="#TOC1">AUTHOR</a><br>
353 nigel 77 <P>
354     The C++ wrapper was contributed by Google Inc.
355     <br>
356 nigel 93 Copyright &copy; 2006 Google Inc.
357 nigel 77 <p>
358     Return to the <a href="index.html">PCRE index page</a>.
359     </p>

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