trunk/doc/pcrecpp.3

.TH PCRECPP 3
.SH NAME
PCRE - Perl-compatible regular expressions.
.SH "SYNOPSIS OF C++ WRAPPER"
.rs
.sp
.B #include <pcrecpp.h>
.PP
.SM
.br
.SH DESCRIPTION
.rs
.sp
The C++ wrapper for PCRE was provided by Google Inc. Some additional
functionality was added by Giuseppe Maxia. This brief man page was constructed
from the notes in the \fIpcrecpp.h\fP file, which should be consulted for
further details.
.
.
.SH "MATCHING INTERFACE"
.rs
.sp
The "FullMatch" operation checks that supplied text matches a supplied pattern
exactly. If pointer arguments are supplied, it copies matched sub-strings that
match sub-patterns into them.
.sp
  Example: successful match
     pcrecpp::RE re("h.*o");
     re.FullMatch("hello");
.sp
  Example: unsuccessful match (requires full match):
     pcrecpp::RE re("e");
     !re.FullMatch("hello");
.sp
  Example: creating a temporary RE object:
     pcrecpp::RE("h.*o").FullMatch("hello");
.sp
You can pass in a "const char*" or a "string" for "text". The examples below
tend to use a const char*. You can, as in the different examples above, store
the RE object explicitly in a variable or use a temporary RE object. The
examples below use one mode or the other arbitrarily. Either could correctly be
used for any of these examples.
.P
You must supply extra pointer arguments to extract matched subpieces.
.sp
  Example: extracts "ruby" into "s" and 1234 into "i"
     int i;
     string s;
     pcrecpp::RE re("(\e\ew+):(\e\ed+)");
     re.FullMatch("ruby:1234", &s, &i);
.sp
  Example: does not try to extract any extra sub-patterns
     re.FullMatch("ruby:1234", &s);
.sp
  Example: does not try to extract into NULL
     re.FullMatch("ruby:1234", NULL, &i);
.sp
  Example: integer overflow causes failure
     !re.FullMatch("ruby:1234567891234", NULL, &i);
.sp
  Example: fails because there aren't enough sub-patterns:
     !pcrecpp::RE("\e\ew+:\e\ed+").FullMatch("ruby:1234", &s);
.sp
  Example: fails because string cannot be stored in integer
     !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
.sp
The provided pointer arguments can be pointers to any scalar numeric
type, or one of:
.sp
   string        (matched piece is copied to string)
   StringPiece   (StringPiece is mutated to point to matched piece)
   T             (where "bool T::ParseFrom(const char*, int)" exists)
   NULL          (the corresponding matched sub-pattern is not copied)
.sp
The function returns true iff all of the following conditions are satisfied:
.sp
  a. "text" matches "pattern" exactly;
.sp
  b. The number of matched sub-patterns is >= number of supplied
     pointers;
.sp
  c. The "i"th argument has a suitable type for holding the
     string captured as the "i"th sub-pattern. If you pass in
     NULL for the "i"th argument, or pass fewer arguments than
     number of sub-patterns, "i"th captured sub-pattern is
     ignored.
.sp
The matching interface supports at most 16 arguments per call.
If you need more, consider using the more general interface
\fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for
\fBDoMatch\fP.
.
.SH "PARTIAL MATCHES"
.rs
.sp
You can use the "PartialMatch" operation when you want the pattern
to match any substring of the text.
.sp
  Example: simple search for a string:
     pcrecpp::RE("ell").PartialMatch("hello");
.sp
  Example: find first number in a string:
     int number;
     pcrecpp::RE re("(\e\ed+)");
     re.PartialMatch("x*100 + 20", &number);
     assert(number == 100);
.
.
.SH "UTF-8 AND THE MATCHING INTERFACE"
.rs
.sp
By default, pattern and text are plain text, one byte per character. The UTF8
flag, passed to the constructor, causes both pattern and string to be treated
as UTF-8 text, still a byte stream but potentially multiple bytes per
character. In practice, the text is likelier to be UTF-8 than the pattern, but
the match returned may depend on the UTF8 flag, so always use it when matching
UTF8 text. For example, "." will match one byte normally but with UTF8 set may
match up to three bytes of a multi-byte character.
.sp
  Example:
     pcrecpp::RE_Options options;
     options.set_utf8();
     pcrecpp::RE re(utf8_pattern, options);
     re.FullMatch(utf8_string);
.sp
  Example: using the convenience function UTF8():
     pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
     re.FullMatch(utf8_string);
.sp
NOTE: The UTF8 flag is ignored if pcre was not configured with the
      --enable-utf8 flag.
.
.
.SH "PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE"
.rs
.sp
PCRE defines some modifiers to change the behavior of the regular expression
engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
pass such modifiers to a RE class. Currently, the following modifiers are
supported:
.sp
   modifier              description               Perl corresponding
.sp
   PCRE_CASELESS         case insensitive match      /i
   PCRE_MULTILINE        multiple lines match        /m
   PCRE_DOTALL           dot matches newlines        /s
   PCRE_DOLLAR_ENDONLY   $ matches only at end       N/A
   PCRE_EXTRA            strict escape parsing       N/A
   PCRE_EXTENDED         ignore whitespaces          /x
   PCRE_UTF8             handles UTF8 chars          built-in
   PCRE_UNGREEDY         reverses * and *?           N/A
   PCRE_NO_AUTO_CAPTURE  disables capturing parens   N/A (*)
.sp
(*) Both Perl and PCRE allow non capturing parentheses by means of the
"?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
capture, while (ab|cd) does.
.P
For a full account on how each modifier works, please check the
PCRE API reference page.
.P
For each modifier, there are two member functions whose name is made
out of the modifier in lowercase, without the "PCRE_" prefix. For
instance, PCRE_CASELESS is handled by
.sp
  bool caseless()
.sp
which returns true if the modifier is set, and
.sp
  RE_Options & set_caseless(bool)
.sp
which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
accessed through the \fBset_match_limit()\fR and \fBmatch_limit()\fR member
functions. Setting \fImatch_limit\fR to a non-zero value will limit the
execution of pcre to keep it from doing bad things like blowing the stack or
taking an eternity to return a result. A value of 5000 is good enough to stop
stack blowup in a 2MB thread stack. Setting \fImatch_limit\fR to zero disables
match limiting. Alternatively, you can call \fBmatch_limit_recursion()\fP
which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
recurses. \fBmatch_limit()\fP limits the number of matches PCRE does;
\fBmatch_limit_recursion()\fP limits the depth of internal recursion, and
therefore the amount of stack that is used.
.P
Normally, to pass one or more modifiers to a RE class, you declare
a \fIRE_Options\fR object, set the appropriate options, and pass this
object to a RE constructor. Example:
.sp
   RE_options opt;
   opt.set_caseless(true);
   if (RE("HELLO", opt).PartialMatch("hello world")) ...
.sp
RE_options has two constructors. The default constructor takes no arguments and
creates a set of flags that are off by default. The optional parameter
\fIoption_flags\fR is to facilitate transfer of legacy code from C programs.
This lets you do
.sp
   RE(pattern,
     RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
.sp
However, new code is better off doing
.sp
   RE(pattern,
     RE_Options().set_caseless(true).set_multiline(true))
       .PartialMatch(str);
.sp
If you are going to pass one of the most used modifiers, there are some
convenience functions that return a RE_Options class with the
appropriate modifier already set: \fBCASELESS()\fR, \fBUTF8()\fR,
\fBMULTILINE()\fR, \fBDOTALL\fR(), and \fBEXTENDED()\fR.
.P
If you need to set several options at once, and you don't want to go through
the pains of declaring a RE_Options object and setting several options, there
is a parallel method that give you such ability on the fly. You can concatenate
several \fBset_xxxxx()\fR member functions, since each of them returns a
reference to its class object. For example, to pass PCRE_CASELESS,
PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
.sp
   RE(" ^ xyz \e\es+ .* blah$",
     RE_Options()
       .set_caseless(true)
       .set_extended(true)
       .set_multiline(true)).PartialMatch(sometext);
.sp
.
.
.SH "SCANNING TEXT INCREMENTALLY"
.rs
.sp
The "Consume" operation may be useful if you want to repeatedly
match regular expressions at the front of a string and skip over
them as they match. This requires use of the "StringPiece" type,
which represents a sub-range of a real string. Like RE, StringPiece
is defined in the pcrecpp namespace.
.sp
  Example: read lines of the form "var = value" from a string.
     string contents = ...;                 // Fill string somehow
     pcrecpp::StringPiece input(contents);  // Wrap in a StringPiece

     string var;
     int value;
     pcrecpp::RE re("(\e\ew+) = (\e\ed+)\en");
     while (re.Consume(&input, &var, &value)) {
       ...;
     }
.sp
Each successful call to "Consume" will set "var/value", and also
advance "input" so it points past the matched text.
.P
The "FindAndConsume" operation is similar to "Consume" but does not
anchor your match at the beginning of the string. For example, you
could extract all words from a string by repeatedly calling
.sp
  pcrecpp::RE("(\e\ew+)").FindAndConsume(&input, &word)
.
.
.SH "PARSING HEX/OCTAL/C-RADIX NUMBERS"
.rs
.sp
By default, if you pass a pointer to a numeric value, the
corresponding text is interpreted as a base-10 number. You can
instead wrap the pointer with a call to one of the operators Hex(),
Octal(), or CRadix() to interpret the text in another base. The
CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
prefixes, but defaults to base-10.
.sp
  Example:
    int a, b, c, d;
    pcrecpp::RE re("(.*) (.*) (.*) (.*)");
    re.FullMatch("100 40 0100 0x40",
                 pcrecpp::Octal(&a), pcrecpp::Hex(&b),
                 pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
.sp
will leave 64 in a, b, c, and d.
.
.
.SH "REPLACING PARTS OF STRINGS"
.rs
.sp
You can replace the first match of "pattern" in "str" with "rewrite".
Within "rewrite", backslash-escaped digits (\e1 to \e9) can be
used to insert text matching corresponding parenthesized group
from the pattern. \e0 in "rewrite" refers to the entire matching
text. For example:
.sp
  string s = "yabba dabba doo";
  pcrecpp::RE("b+").Replace("d", &s);
.sp
will leave "s" containing "yada dabba doo". The result is true if the pattern
matches and a replacement occurs, false otherwise.
.P
\fBGlobalReplace\fP is like \fBReplace\fP except that it replaces all
occurrences of the pattern in the string with the rewrite. Replacements are
not subject to re-matching. For example:
.sp
  string s = "yabba dabba doo";
  pcrecpp::RE("b+").GlobalReplace("d", &s);
.sp
will leave "s" containing "yada dada doo". It returns the number of
replacements made.
.P
\fBExtract\fP is like \fBReplace\fP, except that if the pattern matches,
"rewrite" is copied into "out" (an additional argument) with substitutions.
The non-matching portions of "text" are ignored. Returns true iff a match
occurred and the extraction happened successfully;  if no match occurs, the
string is left unaffected.
.
.
.SH AUTHOR
.rs
.sp
The C++ wrapper was contributed by Google Inc.
.br
Copyright (c) 2005 Google Inc.
1	nigel	79	.TH PCRECPP 3
2	nigel	77	.SH NAME
3			PCRE - Perl-compatible regular expressions.
4			.SH "SYNOPSIS OF C++ WRAPPER"
5			.rs
6			.sp
7			.B #include <pcrecpp.h>
8			.PP
9			.SM
10			.br
11			.SH DESCRIPTION
12			.rs
13			.sp
14	nigel	81	The C++ wrapper for PCRE was provided by Google Inc. Some additional
15			functionality was added by Giuseppe Maxia. This brief man page was constructed
16			from the notes in the \fIpcrecpp.h\fP file, which should be consulted for
17			further details.
18	nigel	77	.
19			.
20			.SH "MATCHING INTERFACE"
21			.rs
22			.sp
23			The "FullMatch" operation checks that supplied text matches a supplied pattern
24			exactly. If pointer arguments are supplied, it copies matched sub-strings that
25			match sub-patterns into them.
26			.sp
27			Example: successful match
28			pcrecpp::RE re("h.*o");
29			re.FullMatch("hello");
30			.sp
31			Example: unsuccessful match (requires full match):
32			pcrecpp::RE re("e");
33			!re.FullMatch("hello");
34			.sp
35			Example: creating a temporary RE object:
36			pcrecpp::RE("h.*o").FullMatch("hello");
37			.sp
38			You can pass in a "const char*" or a "string" for "text". The examples below
39			tend to use a const char*. You can, as in the different examples above, store
40			the RE object explicitly in a variable or use a temporary RE object. The
41			examples below use one mode or the other arbitrarily. Either could correctly be
42			used for any of these examples.
43			.P
44			You must supply extra pointer arguments to extract matched subpieces.
45			.sp
46			Example: extracts "ruby" into "s" and 1234 into "i"
47			int i;
48			string s;
49			pcrecpp::RE re("(\e\ew+):(\e\ed+)");
50			re.FullMatch("ruby:1234", &s, &i);
51			.sp
52			Example: does not try to extract any extra sub-patterns
53			re.FullMatch("ruby:1234", &s);
54			.sp
55			Example: does not try to extract into NULL
56			re.FullMatch("ruby:1234", NULL, &i);
57			.sp
58			Example: integer overflow causes failure
59			!re.FullMatch("ruby:1234567891234", NULL, &i);
60			.sp
61			Example: fails because there aren't enough sub-patterns:
62			!pcrecpp::RE("\e\ew+:\e\ed+").FullMatch("ruby:1234", &s);
63			.sp
64			Example: fails because string cannot be stored in integer
65			!pcrecpp::RE("(.*)").FullMatch("ruby", &i);
66			.sp
67			The provided pointer arguments can be pointers to any scalar numeric
68			type, or one of:
69			.sp
70			string (matched piece is copied to string)
71			StringPiece (StringPiece is mutated to point to matched piece)
72			T (where "bool T::ParseFrom(const char*, int)" exists)
73			NULL (the corresponding matched sub-pattern is not copied)
74			.sp
75			The function returns true iff all of the following conditions are satisfied:
76			.sp
77			a. "text" matches "pattern" exactly;
78			.sp
79			b. The number of matched sub-patterns is >= number of supplied
80			pointers;
81			.sp
82			c. The "i"th argument has a suitable type for holding the
83			string captured as the "i"th sub-pattern. If you pass in
84			NULL for the "i"th argument, or pass fewer arguments than
85			number of sub-patterns, "i"th captured sub-pattern is
86			ignored.
87			.sp
88			The matching interface supports at most 16 arguments per call.
89			If you need more, consider using the more general interface
90			\fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for
91			\fBDoMatch\fP.
92			.
93			.SH "PARTIAL MATCHES"
94			.rs
95			.sp
96			You can use the "PartialMatch" operation when you want the pattern
97			to match any substring of the text.
98			.sp
99			Example: simple search for a string:
100			pcrecpp::RE("ell").PartialMatch("hello");
101			.sp
102			Example: find first number in a string:
103			int number;
104			pcrecpp::RE re("(\e\ed+)");
105			re.PartialMatch("x*100 + 20", &number);
106			assert(number == 100);
107			.
108			.
109			.SH "UTF-8 AND THE MATCHING INTERFACE"
110			.rs
111			.sp
112			By default, pattern and text are plain text, one byte per character. The UTF8
113			flag, passed to the constructor, causes both pattern and string to be treated
114			as UTF-8 text, still a byte stream but potentially multiple bytes per
115			character. In practice, the text is likelier to be UTF-8 than the pattern, but
116			the match returned may depend on the UTF8 flag, so always use it when matching
117			UTF8 text. For example, "." will match one byte normally but with UTF8 set may
118			match up to three bytes of a multi-byte character.
119			.sp
120			Example:
121			pcrecpp::RE_Options options;
122			options.set_utf8();
123			pcrecpp::RE re(utf8_pattern, options);
124			re.FullMatch(utf8_string);
125			.sp
126			Example: using the convenience function UTF8():
127			pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
128			re.FullMatch(utf8_string);
129			.sp
130			NOTE: The UTF8 flag is ignored if pcre was not configured with the
131			--enable-utf8 flag.
132			.
133			.
134	nigel	81	.SH "PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE"
135			.rs
136			.sp
137			PCRE defines some modifiers to change the behavior of the regular expression
138			engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
139			pass such modifiers to a RE class. Currently, the following modifiers are
140			supported:
141			.sp
142			modifier description Perl corresponding
143			.sp
144			PCRE_CASELESS case insensitive match /i
145			PCRE_MULTILINE multiple lines match /m
146			PCRE_DOTALL dot matches newlines /s
147			PCRE_DOLLAR_ENDONLY $ matches only at end N/A
148			PCRE_EXTRA strict escape parsing N/A
149			PCRE_EXTENDED ignore whitespaces /x
150			PCRE_UTF8 handles UTF8 chars built-in
151			PCRE_UNGREEDY reverses * and *? N/A
152			PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
153			.sp
154			(*) Both Perl and PCRE allow non capturing parentheses by means of the
155			"?:" modifier within the pattern itself. e.g. (?:ab\|cd) does not
156			capture, while (ab\|cd) does.
157			.P
158			For a full account on how each modifier works, please check the
159			PCRE API reference page.
160			.P
161			For each modifier, there are two member functions whose name is made
162			out of the modifier in lowercase, without the "PCRE_" prefix. For
163			instance, PCRE_CASELESS is handled by
164			.sp
165			bool caseless()
166			.sp
167			which returns true if the modifier is set, and
168			.sp
169			RE_Options & set_caseless(bool)
170			.sp
171	nigel	87	which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
172	nigel	81	accessed through the \fBset_match_limit()\fR and \fBmatch_limit()\fR member
173			functions. Setting \fImatch_limit\fR to a non-zero value will limit the
174			execution of pcre to keep it from doing bad things like blowing the stack or
175			taking an eternity to return a result. A value of 5000 is good enough to stop
176			stack blowup in a 2MB thread stack. Setting \fImatch_limit\fR to zero disables
177	nigel	87	match limiting. Alternatively, you can call \fBmatch_limit_recursion()\fP
178			which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
179			recurses. \fBmatch_limit()\fP limits the number of matches PCRE does;
180			\fBmatch_limit_recursion()\fP limits the depth of internal recursion, and
181			therefore the amount of stack that is used.
182	nigel	81	.P
183			Normally, to pass one or more modifiers to a RE class, you declare
184			a \fIRE_Options\fR object, set the appropriate options, and pass this
185			object to a RE constructor. Example:
186			.sp
187			RE_options opt;
188			opt.set_caseless(true);
189			if (RE("HELLO", opt).PartialMatch("hello world")) ...
190			.sp
191			RE_options has two constructors. The default constructor takes no arguments and
192			creates a set of flags that are off by default. The optional parameter
193			\fIoption_flags\fR is to facilitate transfer of legacy code from C programs.
194			This lets you do
195			.sp
196			RE(pattern,
197			RE_Options(PCRE_CASELESS\|PCRE_MULTILINE)).PartialMatch(str);
198			.sp
199			However, new code is better off doing
200			.sp
201			RE(pattern,
202			RE_Options().set_caseless(true).set_multiline(true))
203			.PartialMatch(str);
204			.sp
205			If you are going to pass one of the most used modifiers, there are some
206			convenience functions that return a RE_Options class with the
207			appropriate modifier already set: \fBCASELESS()\fR, \fBUTF8()\fR,
208			\fBMULTILINE()\fR, \fBDOTALL\fR(), and \fBEXTENDED()\fR.
209			.P
210			If you need to set several options at once, and you don't want to go through
211			the pains of declaring a RE_Options object and setting several options, there
212			is a parallel method that give you such ability on the fly. You can concatenate
213			several \fBset_xxxxx()\fR member functions, since each of them returns a
214			reference to its class object. For example, to pass PCRE_CASELESS,
215			PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
216			.sp
217			RE(" ^ xyz \e\es+ .* blah$",
218			RE_Options()
219			.set_caseless(true)
220			.set_extended(true)
221			.set_multiline(true)).PartialMatch(sometext);
222			.sp
223			.
224			.
225	nigel	77	.SH "SCANNING TEXT INCREMENTALLY"
226			.rs
227			.sp
228			The "Consume" operation may be useful if you want to repeatedly
229			match regular expressions at the front of a string and skip over
230			them as they match. This requires use of the "StringPiece" type,
231			which represents a sub-range of a real string. Like RE, StringPiece
232			is defined in the pcrecpp namespace.
233			.sp
234			Example: read lines of the form "var = value" from a string.
235			string contents = ...; // Fill string somehow
236			pcrecpp::StringPiece input(contents); // Wrap in a StringPiece
237
238			string var;
239			int value;
240			pcrecpp::RE re("(\e\ew+) = (\e\ed+)\en");
241			while (re.Consume(&input, &var, &value)) {
242			...;
243			}
244			.sp
245			Each successful call to "Consume" will set "var/value", and also
246			advance "input" so it points past the matched text.
247			.P
248			The "FindAndConsume" operation is similar to "Consume" but does not
249			anchor your match at the beginning of the string. For example, you
250			could extract all words from a string by repeatedly calling
251			.sp
252			pcrecpp::RE("(\e\ew+)").FindAndConsume(&input, &word)
253			.
254			.
255			.SH "PARSING HEX/OCTAL/C-RADIX NUMBERS"
256			.rs
257			.sp
258			By default, if you pass a pointer to a numeric value, the
259			corresponding text is interpreted as a base-10 number. You can
260			instead wrap the pointer with a call to one of the operators Hex(),
261			Octal(), or CRadix() to interpret the text in another base. The
262			CRadix operator interprets C-style "0" (base-8) and "0x" (base-16)
263			prefixes, but defaults to base-10.
264			.sp
265			Example:
266			int a, b, c, d;
267			pcrecpp::RE re("(.) (.) (.) (.)");
268			re.FullMatch("100 40 0100 0x40",
269			pcrecpp::Octal(&a), pcrecpp::Hex(&b),
270			pcrecpp::CRadix(&c), pcrecpp::CRadix(&d));
271			.sp
272			will leave 64 in a, b, c, and d.
273			.
274			.
275			.SH "REPLACING PARTS OF STRINGS"
276			.rs
277			.sp
278			You can replace the first match of "pattern" in "str" with "rewrite".
279			Within "rewrite", backslash-escaped digits (\e1 to \e9) can be
280			used to insert text matching corresponding parenthesized group
281			from the pattern. \e0 in "rewrite" refers to the entire matching
282			text. For example:
283			.sp
284			string s = "yabba dabba doo";
285			pcrecpp::RE("b+").Replace("d", &s);
286			.sp
287			will leave "s" containing "yada dabba doo". The result is true if the pattern
288			matches and a replacement occurs, false otherwise.
289			.P
290			\fBGlobalReplace\fP is like \fBReplace\fP except that it replaces all
291			occurrences of the pattern in the string with the rewrite. Replacements are
292			not subject to re-matching. For example:
293			.sp
294			string s = "yabba dabba doo";
295			pcrecpp::RE("b+").GlobalReplace("d", &s);
296			.sp
297			will leave "s" containing "yada dada doo". It returns the number of
298			replacements made.
299			.P
300			\fBExtract\fP is like \fBReplace\fP, except that if the pattern matches,
301			"rewrite" is copied into "out" (an additional argument) with substitutions.
302			The non-matching portions of "text" are ignored. Returns true iff a match
303			occurred and the extraction happened successfully; if no match occurs, the
304			string is left unaffected.
305			.
306			.
307			.SH AUTHOR
308			.rs
309			.sp
310			The C++ wrapper was contributed by Google Inc.
311			.br
312			Copyright (c) 2005 Google Inc.