/vendor/pcre/doc/pcrecpp.3

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  1. .TH PCRECPP 3
  2. .SH NAME
  3. PCRE - Perl-compatible regular expressions.
  4. .SH "SYNOPSIS OF C++ WRAPPER"
  5. .rs
  6. .sp
  7. .B #include <pcrecpp.h>
  8. .
  9. .SH DESCRIPTION
  10. .rs
  11. .sp
  12. The C++ wrapper for PCRE was provided by Google Inc. Some additional
  13. functionality was added by Giuseppe Maxia. This brief man page was constructed
  14. from the notes in the \fIpcrecpp.h\fP file, which should be consulted for
  15. further details.
  16. .
  17. .
  18. .SH "MATCHING INTERFACE"
  19. .rs
  20. .sp
  21. The "FullMatch" operation checks that supplied text matches a supplied pattern
  22. exactly. If pointer arguments are supplied, it copies matched sub-strings that
  23. match sub-patterns into them.
  24. .sp
  25. Example: successful match
  26. pcrecpp::RE re("h.*o");
  27. re.FullMatch("hello");
  28. .sp
  29. Example: unsuccessful match (requires full match):
  30. pcrecpp::RE re("e");
  31. !re.FullMatch("hello");
  32. .sp
  33. Example: creating a temporary RE object:
  34. pcrecpp::RE("h.*o").FullMatch("hello");
  35. .sp
  36. You can pass in a "const char*" or a "string" for "text". The examples below
  37. tend to use a const char*. You can, as in the different examples above, store
  38. the RE object explicitly in a variable or use a temporary RE object. The
  39. examples below use one mode or the other arbitrarily. Either could correctly be
  40. used for any of these examples.
  41. .P
  42. You must supply extra pointer arguments to extract matched subpieces.
  43. .sp
  44. Example: extracts "ruby" into "s" and 1234 into "i"
  45. int i;
  46. string s;
  47. pcrecpp::RE re("(\e\ew+):(\e\ed+)");
  48. re.FullMatch("ruby:1234", &s, &i);
  49. .sp
  50. Example: does not try to extract any extra sub-patterns
  51. re.FullMatch("ruby:1234", &s);
  52. .sp
  53. Example: does not try to extract into NULL
  54. re.FullMatch("ruby:1234", NULL, &i);
  55. .sp
  56. Example: integer overflow causes failure
  57. !re.FullMatch("ruby:1234567891234", NULL, &i);
  58. .sp
  59. Example: fails because there aren't enough sub-patterns:
  60. !pcrecpp::RE("\e\ew+:\e\ed+").FullMatch("ruby:1234", &s);
  61. .sp
  62. Example: fails because string cannot be stored in integer
  63. !pcrecpp::RE("(.*)").FullMatch("ruby", &i);
  64. .sp
  65. The provided pointer arguments can be pointers to any scalar numeric
  66. type, or one of:
  67. .sp
  68. string (matched piece is copied to string)
  69. StringPiece (StringPiece is mutated to point to matched piece)
  70. T (where "bool T::ParseFrom(const char*, int)" exists)
  71. NULL (the corresponding matched sub-pattern is not copied)
  72. .sp
  73. The function returns true iff all of the following conditions are satisfied:
  74. .sp
  75. a. "text" matches "pattern" exactly;
  76. .sp
  77. b. The number of matched sub-patterns is >= number of supplied
  78. pointers;
  79. .sp
  80. c. The "i"th argument has a suitable type for holding the
  81. string captured as the "i"th sub-pattern. If you pass in
  82. void * NULL for the "i"th argument, or a non-void * NULL
  83. of the correct type, or pass fewer arguments than the
  84. number of sub-patterns, "i"th captured sub-pattern is
  85. ignored.
  86. .sp
  87. CAVEAT: An optional sub-pattern that does not exist in the matched
  88. string is assigned the empty string. Therefore, the following will
  89. return false (because the empty string is not a valid number):
  90. .sp
  91. int number;
  92. pcrecpp::RE::FullMatch("abc", "[a-z]+(\e\ed+)?", &number);
  93. .sp
  94. The matching interface supports at most 16 arguments per call.
  95. If you need more, consider using the more general interface
  96. \fBpcrecpp::RE::DoMatch\fP. See \fBpcrecpp.h\fP for the signature for
  97. \fBDoMatch\fP.
  98. .
  99. .SH "QUOTING METACHARACTERS"
  100. .rs
  101. .sp
  102. You can use the "QuoteMeta" operation to insert backslashes before all
  103. potentially meaningful characters in a string. The returned string, used as a
  104. regular expression, will exactly match the original string.
  105. .sp
  106. Example:
  107. string quoted = RE::QuoteMeta(unquoted);
  108. .sp
  109. Note that it's legal to escape a character even if it has no special meaning in
  110. a regular expression -- so this function does that. (This also makes it
  111. identical to the perl function of the same name; see "perldoc -f quotemeta".)
  112. For example, "1.5-2.0?" becomes "1\e.5\e-2\e.0\e?".
  113. .
  114. .SH "PARTIAL MATCHES"
  115. .rs
  116. .sp
  117. You can use the "PartialMatch" operation when you want the pattern
  118. to match any substring of the text.
  119. .sp
  120. Example: simple search for a string:
  121. pcrecpp::RE("ell").PartialMatch("hello");
  122. .sp
  123. Example: find first number in a string:
  124. int number;
  125. pcrecpp::RE re("(\e\ed+)");
  126. re.PartialMatch("x*100 + 20", &number);
  127. assert(number == 100);
  128. .
  129. .
  130. .SH "UTF-8 AND THE MATCHING INTERFACE"
  131. .rs
  132. .sp
  133. By default, pattern and text are plain text, one byte per character. The UTF8
  134. flag, passed to the constructor, causes both pattern and string to be treated
  135. as UTF-8 text, still a byte stream but potentially multiple bytes per
  136. character. In practice, the text is likelier to be UTF-8 than the pattern, but
  137. the match returned may depend on the UTF8 flag, so always use it when matching
  138. UTF8 text. For example, "." will match one byte normally but with UTF8 set may
  139. match up to three bytes of a multi-byte character.
  140. .sp
  141. Example:
  142. pcrecpp::RE_Options options;
  143. options.set_utf8();
  144. pcrecpp::RE re(utf8_pattern, options);
  145. re.FullMatch(utf8_string);
  146. .sp
  147. Example: using the convenience function UTF8():
  148. pcrecpp::RE re(utf8_pattern, pcrecpp::UTF8());
  149. re.FullMatch(utf8_string);
  150. .sp
  151. NOTE: The UTF8 flag is ignored if pcre was not configured with the
  152. --enable-utf8 flag.
  153. .
  154. .
  155. .SH "PASSING MODIFIERS TO THE REGULAR EXPRESSION ENGINE"
  156. .rs
  157. .sp
  158. PCRE defines some modifiers to change the behavior of the regular expression
  159. engine. The C++ wrapper defines an auxiliary class, RE_Options, as a vehicle to
  160. pass such modifiers to a RE class. Currently, the following modifiers are
  161. supported:
  162. .sp
  163. modifier description Perl corresponding
  164. .sp
  165. PCRE_CASELESS case insensitive match /i
  166. PCRE_MULTILINE multiple lines match /m
  167. PCRE_DOTALL dot matches newlines /s
  168. PCRE_DOLLAR_ENDONLY $ matches only at end N/A
  169. PCRE_EXTRA strict escape parsing N/A
  170. PCRE_EXTENDED ignore whitespaces /x
  171. PCRE_UTF8 handles UTF8 chars built-in
  172. PCRE_UNGREEDY reverses * and *? N/A
  173. PCRE_NO_AUTO_CAPTURE disables capturing parens N/A (*)
  174. .sp
  175. (*) Both Perl and PCRE allow non capturing parentheses by means of the
  176. "?:" modifier within the pattern itself. e.g. (?:ab|cd) does not
  177. capture, while (ab|cd) does.
  178. .P
  179. For a full account on how each modifier works, please check the
  180. PCRE API reference page.
  181. .P
  182. For each modifier, there are two member functions whose name is made
  183. out of the modifier in lowercase, without the "PCRE_" prefix. For
  184. instance, PCRE_CASELESS is handled by
  185. .sp
  186. bool caseless()
  187. .sp
  188. which returns true if the modifier is set, and
  189. .sp
  190. RE_Options & set_caseless(bool)
  191. .sp
  192. which sets or unsets the modifier. Moreover, PCRE_EXTRA_MATCH_LIMIT can be
  193. accessed through the \fBset_match_limit()\fR and \fBmatch_limit()\fR member
  194. functions. Setting \fImatch_limit\fR to a non-zero value will limit the
  195. execution of pcre to keep it from doing bad things like blowing the stack or
  196. taking an eternity to return a result. A value of 5000 is good enough to stop
  197. stack blowup in a 2MB thread stack. Setting \fImatch_limit\fR to zero disables
  198. match limiting. Alternatively, you can call \fBmatch_limit_recursion()\fP
  199. which uses PCRE_EXTRA_MATCH_LIMIT_RECURSION to limit how much PCRE
  200. recurses. \fBmatch_limit()\fP limits the number of matches PCRE does;
  201. \fBmatch_limit_recursion()\fP limits the depth of internal recursion, and
  202. therefore the amount of stack that is used.
  203. .P
  204. Normally, to pass one or more modifiers to a RE class, you declare
  205. a \fIRE_Options\fR object, set the appropriate options, and pass this
  206. object to a RE constructor. Example:
  207. .sp
  208. RE_options opt;
  209. opt.set_caseless(true);
  210. if (RE("HELLO", opt).PartialMatch("hello world")) ...
  211. .sp
  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. \fIoption_flags\fR is to facilitate transfer of legacy code from C programs.
  215. This lets you do
  216. .sp
  217. RE(pattern,
  218. RE_Options(PCRE_CASELESS|PCRE_MULTILINE)).PartialMatch(str);
  219. .sp
  220. However, new code is better off doing
  221. .sp
  222. RE(pattern,
  223. RE_Options().set_caseless(true).set_multiline(true))
  224. .PartialMatch(str);
  225. .sp
  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: \fBCASELESS()\fR, \fBUTF8()\fR,
  229. \fBMULTILINE()\fR, \fBDOTALL\fR(), and \fBEXTENDED()\fR.
  230. .P
  231. If you need to set several options at once, and you don't want to go through
  232. the pains of declaring a RE_Options object and setting several options, there
  233. is a parallel method that give you such ability on the fly. You can concatenate
  234. several \fBset_xxxxx()\fR member functions, since each of them returns a
  235. reference to its class object. For example, to pass PCRE_CASELESS,
  236. PCRE_EXTENDED, and PCRE_MULTILINE to a RE with one statement, you may write:
  237. .sp
  238. RE(" ^ xyz \e\es+ .* blah$",
  239. RE_Options()
  240. .set_caseless(true)
  241. .set_extended(true)
  242. .set_multiline(true)).PartialMatch(sometext);
  243. .sp
  244. .
  245. .
  246. .SH "SCANNING TEXT INCREMENTALLY"
  247. .rs
  248. .sp
  249. 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. .sp
  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. string var;
  259. int value;
  260. pcrecpp::RE re("(\e\ew+) = (\e\ed+)\en");
  261. while (re.Consume(&input, &var, &value)) {
  262. ...;
  263. }
  264. .sp
  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. The "FindAndConsume" operation is similar to "Consume" but does not
  269. anchor your match at the beginning of the string. For example, you
  270. could extract all words from a string by repeatedly calling
  271. .sp
  272. pcrecpp::RE("(\e\ew+)").FindAndConsume(&input, &word)
  273. .
  274. .
  275. .SH "PARSING HEX/OCTAL/C-RADIX NUMBERS"
  276. .rs
  277. .sp
  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. .sp
  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. .sp
  292. will leave 64 in a, b, c, and d.
  293. .
  294. .
  295. .SH "REPLACING PARTS OF STRINGS"
  296. .rs
  297. .sp
  298. You can replace the first match of "pattern" in "str" with "rewrite".
  299. Within "rewrite", backslash-escaped digits (\e1 to \e9) can be
  300. used to insert text matching corresponding parenthesized group
  301. from the pattern. \e0 in "rewrite" refers to the entire matching
  302. text. For example:
  303. .sp
  304. string s = "yabba dabba doo";
  305. pcrecpp::RE("b+").Replace("d", &s);
  306. .sp
  307. will leave "s" containing "yada dabba doo". The result is true if the pattern
  308. matches and a replacement occurs, false otherwise.
  309. .P
  310. \fBGlobalReplace\fP is like \fBReplace\fP except that it replaces all
  311. occurrences of the pattern in the string with the rewrite. Replacements are
  312. not subject to re-matching. For example:
  313. .sp
  314. string s = "yabba dabba doo";
  315. pcrecpp::RE("b+").GlobalReplace("d", &s);
  316. .sp
  317. will leave "s" containing "yada dada doo". It returns the number of
  318. replacements made.
  319. .P
  320. \fBExtract\fP is like \fBReplace\fP, 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. .
  326. .
  327. .SH AUTHOR
  328. .rs
  329. .sp
  330. .nf
  331. The C++ wrapper was contributed by Google Inc.
  332. Copyright (c) 2007 Google Inc.
  333. .fi
  334. .
  335. .
  336. .SH REVISION
  337. .rs
  338. .sp
  339. .nf
  340. Last updated: 12 November 2007
  341. .fi