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diff --git a/doc/pcrecpp.3 b/doc/pcrecpp.3 new file mode 100644 index 0000000..fbddd86 --- /dev/null +++ b/doc/pcrecpp.3 @@ -0,0 +1,348 @@ +.TH PCRECPP 3 "08 January 2012" "PCRE 8.30" +.SH NAME +PCRE - Perl-compatible regular expressions. +.SH "SYNOPSIS OF C++ WRAPPER" +.rs +.sp +.B #include <pcrecpp.h> +. +.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. Note that the C++ wrapper supports only the original 8-bit +PCRE library. There is no 16-bit or 32-bit support at present. +. +. +.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 + void * NULL for the "i"th argument, or a non-void * NULL + of the correct type, or pass fewer arguments than the + number of sub-patterns, "i"th captured sub-pattern is + ignored. +.sp +CAVEAT: An optional sub-pattern that does not exist in the matched +string is assigned the empty string. Therefore, the following will +return false (because the empty string is not a valid number): +.sp + int number; + pcrecpp::RE::FullMatch("abc", "[a-z]+(\e\ed+)?", &number); +.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. +.P +NOTE: Do not use \fBno_arg\fP, which is used internally to mark the end of a +list of optional arguments, as a placeholder for missing arguments, as this can +lead to segfaults. +. +. +.SH "QUOTING METACHARACTERS" +.rs +.sp +You can use the "QuoteMeta" operation to insert backslashes before all +potentially meaningful characters in a string. The returned string, used as a +regular expression, will exactly match the original string. +.sp + Example: + string quoted = RE::QuoteMeta(unquoted); +.sp +Note that it's legal to escape a character even if it has no special meaning in +a regular expression -- so this function does that. (This also makes it +identical to the perl function of the same name; see "perldoc -f quotemeta".) +For example, "1.5-2.0?" becomes "1\e.5\e-2\e.0\e?". +. +.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 white spaces /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()\fP and \fBmatch_limit()\fP member +functions. Setting \fImatch_limit\fP 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\fP 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\fP 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\fP 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()\fP, \fBUTF8()\fP, +\fBMULTILINE()\fP, \fBDOTALL\fP(), and \fBEXTENDED()\fP. +.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()\fP 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 +.sp + 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 +.nf +The C++ wrapper was contributed by Google Inc. +Copyright (c) 2007 Google Inc. +.fi +. +. +.SH REVISION +.rs +.sp +.nf +Last updated: 08 January 2012 +.fi |