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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     <li><a name="TOC4" href="#SEC4">PARTIAL MATCHES</a>
20     <li><a name="TOC5" href="#SEC5">UTF-8 AND THE MATCHING INTERFACE</a>
21 nigel 81 <li><a name="TOC6" href="#SEC6">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a>
22     <li><a name="TOC7" href="#SEC7">SCANNING TEXT INCREMENTALLY</a>
23     <li><a name="TOC8" href="#SEC8">PARSING HEX/OCTAL/C-RADIX NUMBERS</a>
24     <li><a name="TOC9" href="#SEC9">REPLACING PARTS OF STRINGS</a>
25     <li><a name="TOC10" href="#SEC10">AUTHOR</a>
26 nigel 77 </ul>
27     <br><a name="SEC1" href="#TOC1">SYNOPSIS OF C++ WRAPPER</a><br>
28     <P>
29     <b>#include &#60;pcrecpp.h&#62;</b>
30     </P>
31     <P>
32     </P>
33     <br><a name="SEC2" href="#TOC1">DESCRIPTION</a><br>
34     <P>
35 nigel 81 The C++ wrapper for PCRE was provided by Google Inc. Some additional
36     functionality was added by Giuseppe Maxia. This brief man page was constructed
37     from the notes in the <i>pcrecpp.h</i> file, which should be consulted for
38     further details.
39 nigel 77 </P>
40     <br><a name="SEC3" href="#TOC1">MATCHING INTERFACE</a><br>
41     <P>
42     The "FullMatch" operation checks that supplied text matches a supplied pattern
43     exactly. If pointer arguments are supplied, it copies matched sub-strings that
44     match sub-patterns into them.
45     <pre>
46     Example: successful match
47     pcrecpp::RE re("h.*o");
48     re.FullMatch("hello");
49    
50     Example: unsuccessful match (requires full match):
51     pcrecpp::RE re("e");
52     !re.FullMatch("hello");
53    
54     Example: creating a temporary RE object:
55     pcrecpp::RE("h.*o").FullMatch("hello");
56     </pre>
57     You can pass in a "const char*" or a "string" for "text". The examples below
58     tend to use a const char*. You can, as in the different examples above, store
59     the RE object explicitly in a variable or use a temporary RE object. The
60     examples below use one mode or the other arbitrarily. Either could correctly be
61     used for any of these examples.
62     </P>
63     <P>
64     You must supply extra pointer arguments to extract matched subpieces.
65     <pre>
66     Example: extracts "ruby" into "s" and 1234 into "i"
67     int i;
68     string s;
69     pcrecpp::RE re("(\\w+):(\\d+)");
70     re.FullMatch("ruby:1234", &s, &i);
71    
72     Example: does not try to extract any extra sub-patterns
73     re.FullMatch("ruby:1234", &s);
74    
75     Example: does not try to extract into NULL
76     re.FullMatch("ruby:1234", NULL, &i);
77    
78     Example: integer overflow causes failure
79     !re.FullMatch("ruby:1234567891234", NULL, &i);
80    
81     Example: fails because there aren't enough sub-patterns:
82     !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
83    
84     Example: fails because string cannot be stored in integer
85     !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
86     </pre>
87     The provided pointer arguments can be pointers to any scalar numeric
88     type, or one of:
89     <pre>
90     string (matched piece is copied to string)
91     StringPiece (StringPiece is mutated to point to matched piece)
92     T (where "bool T::ParseFrom(const char*, int)" exists)
93     NULL (the corresponding matched sub-pattern is not copied)
94     </pre>
95     The function returns true iff all of the following conditions are satisfied:
96     <pre>
97     a. "text" matches "pattern" exactly;
98    
99     b. The number of matched sub-patterns is &#62;= number of supplied
100     pointers;
101    
102     c. The "i"th argument has a suitable type for holding the
103     string captured as the "i"th sub-pattern. If you pass in
104     NULL for the "i"th argument, or pass fewer arguments than
105     number of sub-patterns, "i"th captured sub-pattern is
106     ignored.
107     </pre>
108     The matching interface supports at most 16 arguments per call.
109     If you need more, consider using the more general interface
110     <b>pcrecpp::RE::DoMatch</b>. See <b>pcrecpp.h</b> for the signature for
111     <b>DoMatch</b>.
112     </P>
113     <br><a name="SEC4" href="#TOC1">PARTIAL MATCHES</a><br>
114     <P>
115     You can use the "PartialMatch" operation when you want the pattern
116     to match any substring of the text.
117     <pre>
118     Example: simple search for a string:
119     pcrecpp::RE("ell").PartialMatch("hello");
120    
121     Example: find first number in a string:
122     int number;
123     pcrecpp::RE re("(\\d+)");
124     re.PartialMatch("x*100 + 20", &number);
125     assert(number == 100);
126     </PRE>
127     </P>
128     <br><a name="SEC5" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
129     <P>
130     By default, pattern and text are plain text, one byte per character. The UTF8
131     flag, passed to the constructor, causes both pattern and string to be treated
132     as UTF-8 text, still a byte stream but potentially multiple bytes per
133     character. In practice, the text is likelier to be UTF-8 than the pattern, but
134     the match returned may depend on the UTF8 flag, so always use it when matching
135     UTF8 text. For example, "." will match one byte normally but with UTF8 set may
136     match up to three bytes of a multi-byte character.
137     <pre>
138     Example:
139     pcrecpp::RE_Options options;
140     options.set_utf8();
141     pcrecpp::RE re(utf8_pattern, options);
142     re.FullMatch(utf8_string);
143    
144     Example: using the convenience function UTF8():
145     pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
146     re.FullMatch(utf8_string);
147     </pre>
148     NOTE: The UTF8 flag is ignored if pcre was not configured with the
149     <pre>
150     --enable-utf8 flag.
151     </PRE>
152     </P>
153 nigel 81 <br><a name="SEC6" href="#TOC1">PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE</a><br>
154 nigel 77 <P>
155 nigel 81 PCRE defines some modifiers to change the behavior of the regular expression
156     engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
157     pass such modifiers to a RE class. Currently, the following modifiers are
158     supported:
159     <pre>
160     modifier description Perl corresponding
161    
162     PCRE_CASELESS case insensitive match /i
163     PCRE_MULTILINE multiple lines match /m
164     PCRE_DOTALL dot matches newlines /s
165     PCRE_DOLLAR_ENDONLY $ matches only at end N/A
166     PCRE_EXTRA strict escape parsing N/A
167     PCRE_EXTENDED ignore whitespaces /x
168     PCRE_UTF8 handles UTF8 chars built-in
169     PCRE_UNGREEDY reverses * and *? N/A
170     PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
171     </pre>
172     (*) Both Perl and PCRE allow non capturing parentheses by means of the
173     "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
174     capture, while (ab|cd) does.
175     </P>
176     <P>
177     For a full account on how each modifier works, please check the
178     PCRE API reference page.
179     </P>
180     <P>
181     For each modifier, there are two member functions whose name is made
182     out of the modifier in lowercase, without the "PCRE_" prefix. For
183     instance, PCRE_CASELESS is handled by
184     <pre>
185     bool caseless()
186     </pre>
187     which returns true if the modifier is set, and
188     <pre>
189     RE_Options & set_caseless(bool)
190     </pre>
191 nigel 87 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
192 nigel 81 accessed through the <b>set_match_limit()</b> and <b>match_limit()</b> member
193     functions. Setting <i>match_limit</i> to a non-zero value will limit the
194     execution of pcre to keep it from doing bad things like blowing the stack or
195     taking an eternity to return a result. A value of 5000 is good enough to stop
196     stack blowup in a 2MB thread stack. Setting <i>match_limit</i> to zero disables
197 nigel 87 match limiting. Alternatively, you can call <b>match_limit_recursion()</b>
198     which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
199     recurses. <b>match_limit()</b> limits the number of matches PCRE does;
200     <b>match_limit_recursion()</b> limits the depth of internal recursion, and
201     therefore the amount of stack that is used.
202 nigel 81 </P>
203     <P>
204     Normally, to pass one or more modifiers to a RE class, you declare
205     a <i>RE_Options</i> object, set the appropriate options, and pass this
206     object to a RE constructor. Example:
207     <pre>
208     RE_options opt;
209     opt.set_caseless(true);
210     if (RE("HELLO", opt).PartialMatch("hello world")) ...
211     </pre>
212     RE_options has two constructors. The default constructor takes no arguments and
213     creates a set of flags that are off by default. The optional parameter
214     <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
215     This lets you do
216     <pre>
217     RE(pattern,
218     RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
219     </pre>
220     However, new code is better off doing
221     <pre>
222     RE(pattern,
223     RE_Options().set_caseless(true).set_multiline(true))
224     .PartialMatch(str);
225     </pre>
226     If you are going to pass one of the most used modifiers, there are some
227     convenience functions that return a RE_Options class with the
228     appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
229     <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
230     </P>
231     <P>
232     If you need to set several options at once, and you don't want to go through
233     the pains of declaring a RE_Options object and setting several options, there
234     is a parallel method that give you such ability on the fly. You can concatenate
235     several <b>set_xxxxx()</b> member functions, since each of them returns a
236     reference to its class object. For example, to pass PCRE_CASELESS,
237     PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
238     <pre>
239     RE(" ^ xyz \\s+ .* blah$",
240     RE_Options()
241     .set_caseless(true)
242     .set_extended(true)
243     .set_multiline(true)).PartialMatch(sometext);
244    
245     </PRE>
246     </P>
247     <br><a name="SEC7" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
248     <P>
249 nigel 77 The "Consume" operation may be useful if you want to repeatedly
250     match regular expressions at the front of a string and skip over
251     them as they match. This requires use of the "StringPiece" type,
252     which represents a sub-range of a real string. Like RE, StringPiece
253     is defined in the pcrecpp namespace.
254     <pre>
255     Example: read lines of the form "var = value" from a string.
256     string contents = ...; // Fill string somehow
257     pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
258     </PRE>
259     </P>
260     <P>
261     <pre>
262     string var;
263     int value;
264     pcrecpp::RE re("(\\w+) = (\\d+)\n");
265     while (re.Consume(&input, &var, &value)) {
266     ...;
267     }
268     </pre>
269     Each successful call to "Consume" will set "var/value", and also
270     advance "input" so it points past the matched text.
271     </P>
272     <P>
273     The "FindAndConsume" operation is similar to "Consume" but does not
274     anchor your match at the beginning of the string. For example, you
275     could extract all words from a string by repeatedly calling
276     <pre>
277     pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
278     </PRE>
279     </P>
280 nigel 81 <br><a name="SEC8" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
281 nigel 77 <P>
282     By default, if you pass a pointer to a numeric value, the
283     corresponding text is interpreted as a base-10 number. You can
284     instead wrap the pointer with a call to one of the operators Hex(),
285     Octal(), or CRadix() to interpret the text in another base. The
286     CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
287     prefixes, but defaults to base-10.
288     <pre>
289     Example:
290     int a, b, c, d;
291     pcrecpp::RE re("(.*) (.*) (.*) (.*)");
292     re.FullMatch("100 40 0100 0x40",
293     pcrecpp::Octal(&a), pcrecpp::Hex(&b),
294     pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
295     </pre>
296     will leave 64 in a, b, c, and d.
297     </P>
298 nigel 81 <br><a name="SEC9" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
299 nigel 77 <P>
300     You can replace the first match of "pattern" in "str" with "rewrite".
301     Within "rewrite", backslash-escaped digits (\1 to \9) can be
302     used to insert text matching corresponding parenthesized group
303     from the pattern. \0 in "rewrite" refers to the entire matching
304     text. For example:
305     <pre>
306     string s = "yabba dabba doo";
307     pcrecpp::RE("b+").Replace("d", &s);
308     </pre>
309     will leave "s" containing "yada dabba doo". The result is true if the pattern
310     matches and a replacement occurs, false otherwise.
311     </P>
312     <P>
313     <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
314     occurrences of the pattern in the string with the rewrite. Replacements are
315     not subject to re-matching. For example:
316     <pre>
317     string s = "yabba dabba doo";
318     pcrecpp::RE("b+").GlobalReplace("d", &s);
319     </pre>
320     will leave "s" containing "yada dada doo". It returns the number of
321     replacements made.
322     </P>
323     <P>
324     <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
325     "rewrite" is copied into "out" (an additional argument) with substitutions.
326     The non-matching portions of "text" are ignored. Returns true iff a match
327     occurred and the extraction happened successfully; if no match occurs, the
328     string is left unaffected.
329     </P>
330 nigel 81 <br><a name="SEC10" href="#TOC1">AUTHOR</a><br>
331 nigel 77 <P>
332     The C++ wrapper was contributed by Google Inc.
333     <br>
334     Copyright &copy; 2005 Google Inc.
335     <p>
336     Return to the <a href="index.html">PCRE index page</a>.
337     </p>

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