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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>
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");
50     Example: unsuccessful match (requires full match):
51     pcrecpp::RE re("e");
52     !re.FullMatch("hello");
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);
72     Example: does not try to extract any extra sub-patterns
73     re.FullMatch("ruby:1234", &s);
75     Example: does not try to extract into NULL
76     re.FullMatch("ruby:1234", NULL, &i);
78     Example: integer overflow causes failure
79     !re.FullMatch("ruby:1234567891234", NULL, &i);
81     Example: fails because there aren't enough sub-patterns:
82     !pcrecpp::RE("\\w+:\\d+").FullMatch("ruby:1234", &s);
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;
99     b. The number of matched sub-patterns is &#62;= number of supplied
100     pointers;
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");
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);
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
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     which sets or unsets the modifier. Moreover, PCRE_CONFIG_MATCH_LIMIT can be
192     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     match limiting.
198     </P>
199     <P>
200     Normally, to pass one or more modifiers to a RE class, you declare
201     a <i>RE_Options</i> object, set the appropriate options, and pass this
202     object to a RE constructor. Example:
203     <pre>
204     RE_options opt;
205     opt.set_caseless(true);
206     if (RE("HELLO", opt).PartialMatch("hello world")) ...
207     </pre>
208     RE_options has two constructors. The default constructor takes no arguments and
209     creates a set of flags that are off by default. The optional parameter
210     <i>option_flags</i> is to facilitate transfer of legacy code from C programs.
211     This lets you do
212     <pre>
213     RE(pattern,
214     RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
215     </pre>
216     However, new code is better off doing
217     <pre>
218     RE(pattern,
219     RE_Options().set_caseless(true).set_multiline(true))
220     .PartialMatch(str);
221     </pre>
222     If you are going to pass one of the most used modifiers, there are some
223     convenience functions that return a RE_Options class with the
224     appropriate modifier already set: <b>CASELESS()</b>, <b>UTF8()</b>,
225     <b>MULTILINE()</b>, <b>DOTALL</b>(), and <b>EXTENDED()</b>.
226     </P>
227     <P>
228     If you need to set several options at once, and you don't want to go through
229     the pains of declaring a RE_Options object and setting several options, there
230     is a parallel method that give you such ability on the fly. You can concatenate
231     several <b>set_xxxxx()</b> member functions, since each of them returns a
232     reference to its class object. For example, to pass PCRE_CASELESS,
233     PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
234     <pre>
235     RE(" ^ xyz \\s+ .* blah$",
236     RE_Options()
237     .set_caseless(true)
238     .set_extended(true)
239     .set_multiline(true)).PartialMatch(sometext);
241     </PRE>
242     </P>
243     <br><a name="SEC7" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
244     <P>
245 nigel 77 The "Consume" operation may be useful if you want to repeatedly
246     match regular expressions at the front of a string and skip over
247     them as they match. This requires use of the "StringPiece" type,
248     which represents a sub-range of a real string. Like RE, StringPiece
249     is defined in the pcrecpp namespace.
250     <pre>
251     Example: read lines of the form "var = value" from a string.
252     string contents = ...; // Fill string somehow
253     pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
254     </PRE>
255     </P>
256     <P>
257     <pre>
258     string var;
259     int value;
260     pcrecpp::RE re("(\\w+) = (\\d+)\n");
261     while (re.Consume(&input, &var, &value)) {
262     ...;
263     }
264     </pre>
265     Each successful call to "Consume" will set "var/value", and also
266     advance "input" so it points past the matched text.
267     </P>
268     <P>
269     The "FindAndConsume" operation is similar to "Consume" but does not
270     anchor your match at the beginning of the string. For example, you
271     could extract all words from a string by repeatedly calling
272     <pre>
273     pcrecpp::RE("(\\w+)").FindAndConsume(&input, &word)
274     </PRE>
275     </P>
276 nigel 81 <br><a name="SEC8" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
277 nigel 77 <P>
278     By default, if you pass a pointer to a numeric value, the
279     corresponding text is interpreted as a base-10 number. You can
280     instead wrap the pointer with a call to one of the operators Hex(),
281     Octal(), or CRadix() to interpret the text in another base. The
282     CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
283     prefixes, but defaults to base-10.
284     <pre>
285     Example:
286     int a, b, c, d;
287     pcrecpp::RE re("(.*) (.*) (.*) (.*)");
288     re.FullMatch("100 40 0100 0x40",
289     pcrecpp::Octal(&a), pcrecpp::Hex(&b),
290     pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
291     </pre>
292     will leave 64 in a, b, c, and d.
293     </P>
294 nigel 81 <br><a name="SEC9" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
295 nigel 77 <P>
296     You can replace the first match of "pattern" in "str" with "rewrite".
297     Within "rewrite", backslash-escaped digits (\1 to \9) can be
298     used to insert text matching corresponding parenthesized group
299     from the pattern. \0 in "rewrite" refers to the entire matching
300     text. For example:
301     <pre>
302     string s = "yabba dabba doo";
303     pcrecpp::RE("b+").Replace("d", &s);
304     </pre>
305     will leave "s" containing "yada dabba doo". The result is true if the pattern
306     matches and a replacement occurs, false otherwise.
307     </P>
308     <P>
309     <b>GlobalReplace</b> is like <b>Replace</b> except that it replaces all
310     occurrences of the pattern in the string with the rewrite. Replacements are
311     not subject to re-matching. For example:
312     <pre>
313     string s = "yabba dabba doo";
314     pcrecpp::RE("b+").GlobalReplace("d", &s);
315     </pre>
316     will leave "s" containing "yada dada doo". It returns the number of
317     replacements made.
318     </P>
319     <P>
320     <b>Extract</b> is like <b>Replace</b>, except that if the pattern matches,
321     "rewrite" is copied into "out" (an additional argument) with substitutions.
322     The non-matching portions of "text" are ignored. Returns true iff a match
323     occurred and the extraction happened successfully; if no match occurs, the
324     string is left unaffected.
325     </P>
326 nigel 81 <br><a name="SEC10" href="#TOC1">AUTHOR</a><br>
327 nigel 77 <P>
328     The C++ wrapper was contributed by Google Inc.
329     <br>
330     Copyright &copy; 2005 Google Inc.
331     <p>
332     Return to the <a href="index.html">PCRE index page</a>.
333     </p>

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