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1 <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">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 </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 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 </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 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 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 <br><a name="SEC4" href="#TOC1">QUOTING METACHARACTERS</a><br>
122 <P>
123 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 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 <br><a name="SEC6" href="#TOC1">UTF-8 AND THE MATCHING INTERFACE</a><br>
151 <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>
176 <P>
177 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 which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
214 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 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 </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 <br><a name="SEC8" href="#TOC1">SCANNING TEXT INCREMENTALLY</a><br>
270 <P>
271 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 <br><a name="SEC9" href="#TOC1">PARSING HEX/OCTAL/C-RADIX NUMBERS</a><br>
303 <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 <br><a name="SEC10" href="#TOC1">REPLACING PARTS OF STRINGS</a><br>
321 <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 <br><a name="SEC11" href="#TOC1">AUTHOR</a><br>
353 <P>
354 The C++ wrapper was contributed by Google Inc.
355 <br>
356 Copyright &copy; 2006 Google Inc.
357 <p>
358 Return to the <a href="index.html">PCRE index page</a>.
359 </p>

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