Pcre class Reference

The library "pcre++" defines a class named "Pcre" which you can use to search in strings using reular expressions as well as getting matched sub strings. It does currently not support all features, which the underlying PCRE library provides, but the most important stuff is implemented.

/*
 *
 *  This file  is part of the PCRE++ Class Library.
 *
 *  By  accessing  this software,  PCRE++, you  are  duly informed
 *  of and agree to be  bound  by the  conditions  described below
 *  in this notice:
 *
 *  This software product,  PCRE++,  is developed by Thomas Linden
 *  and  copyrighted (C) 2002  by  Thomas Linden,  with all rights 
 *  reserved.
 *
 *  There  is no charge for PCRE++ software.  You can redistribute
 *  it and/or modify it under the terms of the GNU  Lesser General
 *  Public License, which is incorporated by reference herein.
 *
 *  PCRE++ is distributed WITHOUT ANY WARRANTY, IMPLIED OR EXPRESS,
 *  OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE or that
 *  the use of it will not infringe on any third party's intellec-
 *  tual property rights.
 *
 *  You should have received a copy of the GNU Lesser General Public
 *  License along with PCRE++.  Copies can also be obtained from:
 *
 *    http://www.gnu.org/licenses/lgpl.txt
 *
 *  or by writing to:
 *
 *  Free Software Foundation, Inc.
 *  59 Temple Place, Suite 330
 *  Boston, MA 02111-1307
 *  USA
 *
 *  Or contact:
 *
 *   "Thomas Linden" <tom@daemon.de>
 *
 *
 */


/* you need to include the pcre++ header file */
#include <pcre++.h>
#include <iostream>

using namespace std;

void regex() {
    /*
     * define a string with a regular expression
     */
    string expression = "([a-z]*) ([0-9]+)";

    /*
     * this is the string in which we want to search
     */
    string stuff = "hallo 11 robert";

    cout << "  searching in \"" << stuff << "\" for regex \""
         << expression << "\":" << endl;

    /*
     * Create a new Pcre object, search case-insensitive ("i")
     */
    Pcre reg(expression, "i");
    
    /*
     * see if the expression matched
     */
    if(reg.search(stuff) == true) {

      /*
       * see if the expression generated any substrings
       */
      if(reg.num_matches >= 1) {

        /*
         * print out the number of substrings
         */
        cout << "  generated " << reg.matches() << " substrings:" << endl;
          
        /*
         * iterate over the matched sub strings
         */
        for(int pos=0; pos < reg.matches(); pos++) {
          /* print out each substring */
          cout << "  substring " << pos << ": " << reg.get_match(pos);
          /* print out the start/end offset of the current substring
           * within the searched string(stuff)
           */
          cout << " (start: " << reg.get_match_start(pos) << ", end: "
               << reg.get_match_end(pos) << ")" << endl;
        }
      }
      else {
        /*
         * we had a match, but it generated no substrings, for whatever reason
         */
        cout << "   it matched, but there where no substrings." << endl;
      }
    }
    else {
      /*
       * no match at all
       */
      cout << "   didn't match." << endl;
    }
}



void replace() {
    /*
     * Sample of replace() usage
     */
    string orig = "Hans ist 22 Jahre alt. Er ist 8 Jahre älter als Fred.";
    cout << "   orig: " << orig << endl;

    /*
     * define a regex for digits (character class)
     */
    Pcre p(" ([0-9]+) ");

    /*
     * replace the 1st occurence of [0-9]+ with "zweiundzwanzig"
     */
    string n = p.replace(orig, " zweiundzwanzig($1) ");

    /*
     * prints out: "Hans ist zweiundzwanzig Jahre alt. Er ist 8 Jahre älter
     * als Fred."
     */
    cout << "   new: " << n << endl; 
}


void replace_multi() {
  /*
   * Sample of replace() usage with multiple substrings
   */
  string orig = " 08:23 ";
  cout << "   orig: " << orig << endl;
  
  /*
   * create regex which, if it matches, creates 3 substrings
   */
  Pcre reg(" ([0-9]+)(:)([0-9]+) ", "sig");

  /*
   * remove $2 (":")
   * re-use $1 ("08") and $3 ("23") in the replace string
   */
  string n  = reg.replace(orig, "$1 Stunden und $3 Minuten");

  /*
   * prints the result: "08 Stunden und 23 Minuten"
   */
  cout << "   new:  " << n  << endl;
}


void normalize() {
  /*
   * another sample to check if normalizing using replace() works
   */
  string orig = "Heute   ist ein  schoener  Tag        gell?";
  cout << "   orig: " << orig << endl;

  /*
   * create regex for normalizing whitespace
   */
  Pcre reg("[\\s]+", "gs");

  /*
   * do the normalizing process
   */
  string n = reg.replace(orig, " ");

  /*
   * prints the result, should be: "Heute ist ein schoener Tag , gell?"
   */
  cout << "   new:  " << n  << endl;
}


void split() {
  /*
   * Sample of split() usage
   */
      string sp_orig = "was21willst2387461du3alter!";
      cout << "   orig: " << sp_orig << endl;

      /*
       * define a regex for digits (character class)
       */
      string delimiter = "[0-9]+";

      /*
       * new Pcre object, match globally ("g" flag)
       */
      Pcre S(delimiter, "g");

      /*
       * split "was21willst2387461du3alter!" by digits
       */
      Array splitted = S.split(sp_orig);
      
      /*
       * iterate over the resulting list
       */
      cout << "   splitted: ";
      for(ArrayIterator A = splitted.begin(); A != splitted.end(); ++A)
        cout << *A << " ";
      cout << endl;
}


void ex() {
  /*
   * Pcre::exception Test
   */
  
  /*
   * this will generate only one substring, "This"
   */
  Pcre ex("([a-z]+)", "i");
  if(ex.search("This is a test.")) {
    cout << "  trying to access a non-existing substring:" << endl;
    cout << "  substring 2: " << ex.get_match(1) << endl; 
  }
}


void mycopy() {
  /*
   * Sample use of copy contsructor and operator=
   */
    cout << "  initializing reg1(([a-z]+?)" << endl;
    Pcre reg1("^([a-z]+?)");

    /*
     * create an empty Pcre objects
     */
    Pcre reg2;
    
    /*
     * copy reg1 to reg2 (operator=)
     */
    cout << "  copying reg1 to new Pcre object reg2" << endl;
    reg2 = reg1;

    /*
     * using the copy constructor to initialize the 3rd object
     */
    cout << "  creating a new Pcre object reg3 from reg2" << endl;
    Pcre reg3(reg2);

    /*
     * doing regular stuff on reg3
     */
    if(reg3.search("anton"))
      cout << "  string 'anton' matched using reg3 object" << endl;
}

void multisearch() {
  Pcre reg("([^\\n]+\\n)");
  string str = "\nline1\nline2\nline3\n";
  size_t pos = 0;

  while (pos <= str.length()) {
    if( reg.search(str, pos)) {
      pos = reg.get_match_end(0);
      cout << "   pos: " << pos << " match: " << reg.get_match(0);
    }
    else
      break;
  }
}

int main() {
  /* 
   * the Pcre class throws errors via exceptions
   */
  try {
    cout << endl << "SEARCH() sample:" << endl;
    regex();

    cout << endl << "REPLACE() sample:" << endl;
    replace();

    cout << endl << "Multiple REPLACE() sample:" << endl;
    replace_multi();

    cout << endl << "Normalizing REPLACE() sample:" << endl;
    normalize();

    cout << endl << "SPLIT() sample:" << endl;
    split();

    cout << endl << "COPY+Operator sample:" << endl;
    mycopy();

    cout << endl << "Multi line search test:" << endl;
    multisearch();

    cout << endl << "Pcre::exception test:" << endl;
    ex();

    exit(0);
  }
  catch (Pcre::exception &E) {
    /*
     * the Pcre class has thrown an exception
     */
    cerr << "Pcre++ error: " << E.what() << endl;
    exit(-1);
  }
  exit(0);
}

Compile your programs which use the prce++ class using the following command line:

   g++ -c yourcode.o `pcre-config --cflags` `pcre++-config --cflags`
   g++ yourcode.o `pcre-config --libs` `pcre++-config --libs` -o yourprogram

If you want to learn more about regular expressions which can be used with pcre++, then please read the following documentation: perlre - Perl regular expressions

The pcre library itself does also contain some usefull documentation, which maybe interesting for you: PCRE manual page

Constructor & Destructor Documentation

Pcre::Pcre

(

)

Empty Constructor. Create a new empty Pcre object. This is the simplest constructor available, you might consider one of the other constructors as a better solution. You need to initialize thie Pcre object, if you use the empty constructor. You can use one of the two available operator= operators to assign it an expression or a Pcre copy.

Returns:: A new empty Pcre object

Definition at line 86 of file pcre++.cc.

Pcre::Pcre

(

const std::string &

expression

)

Constructor. Compile the given pattern. An Pcre object created this way can be used multiple times to do searches.

Parameters:

expression

a string, which must be a valid perl regular expression.

Returns:: A new Pcre object, which holds te compiled pattern.

See also:: Pcre(const std::string& expression, const std::string& flags)

Definition at line 49 of file pcre++.cc.

Pcre::Pcre	(	const std::string &	expression,
		const std::string &	flags
	)

Constructor. Compile the given pattern. An Pcre object created this way can be used multiple times to do searches.

Parameters:

expression	a string, which must be a valid perl regular expression.
flags	can be one or more of the following letters:

i Search case insensitive.

m Match on multiple lines, thus ^ and $ are interpreted as the start and end of the entire string, not of a single line.

s A dot in an expression matches newlines too(which is normally not the case).

x Whitespace characters will be ignored (except within character classes or if escaped).

g Match multiple times. This flags affects only the behavior of the replace(const std::string& piece, const std::string& with) method.

Returns:: A new Pcre object, which holds te compiled pattern.

See also:: Pcre(const std::string& expression)

Definition at line 57 of file pcre++.cc.

Pcre::~Pcre

(

)

Destructor. The desturcor will automatically invoked if the object is no more used. It frees all the memory allocated by pcre++.

Definition at line 99 of file pcre++.cc.

References num_matches.

Member Function Documentation

string Pcre::get_match

(

int

pos

)

Get a substring at a known position. This method throws an out-of-range exception if the given position is invalid.

Parameters:

pos

the position of the substring to return. Identical to perl's $1..$n.

Returns:: the substring at the given position.

Example:

 
 std::string mysub = regex.get_match(1);

Get the first substring that metched the expression in the "regex" object.

Definition at line 59 of file get.cc.

References ArrayIterator, and num_matches.

int Pcre::get_match_end

(

)

Get the end position of the entire match within the searched string. This method returns the character position of the last character of the entire match within the searched string.

Returns:: the integer character position of the last character of the entire match.

Example:


 Pcre regex("([0-9]+)\s([a-z]+)");     // search for the date(makes 2 substrings
 regex.search("The 11th september.");  // do the search on this string
 int pos = regex.get_match_end();      // returns 17, because "11th september", which is
                                           // the entire match, ends at the
                                       // 17th character inside the search string.

See also:

int get_match_start()

int get_match_start(int pos)

int get_match_end(int pos)

Definition at line 76 of file get.cc.

Referenced by replace().

int Pcre::get_match_end

(

int

pos

)

Get the end position of a substring within the searched string. This method returns the character position of the last character of a substring withing the searched string.

Parameters:

pos

the position of the substring. Identical to perl's $1..$n.

Returns:: the integer character position of the last character of a substring. Positions are starting at 0.

Example:


 Pcre regex("([0-9]+)");               // search for numerical characters
 regex.search("The 11th september.");  // do the search on this string
 std::string day = regex.get_match(1);      // returns "11"
 int pos = regex.get_match_end(1);     // returns 5, because "11" ends at the
                                       // 5th character inside the search string.

See also:

int get_match_start(int pos)

int get_match_start()

int get_match_end()

Definition at line 95 of file get.cc.

References num_matches.

size_t Pcre::get_match_length

(

int

pos

)

Get the length of a substring at a known position. This method throws an out-of-range exception if the given position is invalid.

Parameters:

pos

the position of the substring-length to return. Identical to perl's $1..$n.

Returns:: the length substring at the given position.

Definition at line 109 of file get.cc.

References ArrayIterator, and num_matches.

int Pcre::get_match_start

(

)

Get the start position of the entire match within the searched string. This method returns the character position of the first character of the entire match within the searched string.

Returns:: the integer character position of the first character of the entire match.

Example:


 Pcre regex("([0-9]+)\s([a-z]+)");     // search for the date(makes 2 substrings
 regex.search("The 11th september.");  // do the search on this string
 int pos = regex.get_match_start();    // returns 4, because "11th september" begins at the
                                       // 4th character inside the search string.

See also:

int get_match_start(int pos)

int get_match_end(int pos)

int get_match_end()

Definition at line 69 of file get.cc.

Referenced by replace().

int Pcre::get_match_start

(

int

pos

)

Get the start position of a substring within the searched string. This method returns the character position of the first character of a substring withing the searched string.

Parameters:

pos

the position of the substring. Identical to perl's $1..$n.

Returns:: the integer character position of the first character of a substring. Positions are starting at 0.

Example:

 
 Pcre regex("([0-9]+)");               // search for numerical characters
 regex.search("The 11th september.");  // do the search on this string
 std::string day = regex.get_match(1);      // returns "11"
 int pos = regex.get_match_start(1);   // returns 4, because "11" begins at the
                                       // 4th character inside the search string.

See also:

int get_match_end(int pos)

int get_match_end()

int get_match_start()

Definition at line 83 of file get.cc.

References num_matches.

Array * Pcre::get_sub_strings

(

)

Return a vector of substrings, if any.

Returns:: a pointer to an Array, which may be NULL, if no substrings has been found.

See also:: Array

Definition at line 52 of file get.cc.

References Array.

bool Pcre::matched ( ) [inline]

Test if a search was successfull. This method must be invoked after calling search().

Returns:: boolean true if the search was successfull at all, or false if not.

Definition at line 409 of file pcre++.h.

Referenced by replace().

int Pcre::matches ( ) [inline]

Get the number of substrings generated by pcre++.

Returns:: the number of substrings generated by pcre++.

Definition at line 414 of file pcre++.h.

Referenced by replace().

const Pcre & Pcre::operator=

(

const Pcre &

)

Operator =.

Parameters:

&P	an Pcre object

Returns:: a new Pcre object

Example:

 Pcre reg1("^[a-z]+?");
 Pcre reg2;
 reg2 = reg1;

Definition at line 132 of file pcre++.cc.

References _expression, _flags, case_t, and global_t.

const Pcre & Pcre::operator=

(

const std::string &

expression

)

Operator =.

Parameters:

expression

a valid regular expression.

Returns:: a new Pcre object.

Example:

 Pcre regex = "(A+?)";

Definition at line 121 of file pcre++.cc.

string Pcre::replace	(	const std::string &	piece,
		const std::string &	with
	)

Replace parts of a string using regular expressions. This method is the counterpart of the perl s/// operator. It replaces the substrings which matched the given regular expression (given to the constructor) with the supplied string.

Parameters:

piece	the string in which you want to search and replace.
with	the string which you want to place on the positions which match the expression (given to the constructor).

Definition at line 50 of file replace.cc.

References __pcredebug, did_match, get_match_end(), get_match_start(), matched(), matches(), num_matches, and search().

bool Pcre::search	(	const std::string &	stuff,
		int	OffSet
	)

Do a search on the given string beginning at the given offset. This method does the actual search on the given string.

Parameters:

stuff	the string in which you want to search for something.
OffSet	the offset where to start the search.

Returns:: boolean true if the regular expression matched. false if not.

See also:: bool search(const std::string& stuff)

Definition at line 83 of file search.cc.

bool Pcre::search

(

const std::string &

stuff

)

Do a search on the given string. This method does the actual search on the given string.

Parameters:

stuff

the string in which you want to search for something.

Returns:: boolean true if the regular expression matched. false if not.

See also:: bool search(const std::string& stuff, int OffSet)

Definition at line 87 of file search.cc.

Referenced by replace().

Member Data Documentation

bool Pcre::did_match

Definition at line 169 of file pcre++.h.

Referenced by replace().


Public Member Functions
	Pcre ()
	Pcre (const std::string &expression)
	Pcre (const std::string &expression, const std::string &flags)
	Pcre (const Pcre &P)
const Pcre &	operator= (const std::string &expression)
const Pcre &	operator= (const Pcre &P)
	~Pcre ()
bool	search (const std::string &stuff)
bool	search (const std::string &stuff, int OffSet)
Array *	get_sub_strings ()
std::string	get_match (int pos)
int	get_match_start (int pos)
int	get_match_end (int pos)
int	get_match_start ()
int	get_match_end ()
size_t	get_match_length (int pos)
bool	matched ()
int	matches ()
Array	split (const std::string &piece)
Array	split (const std::string &piece, int limit)
Array	split (const std::string &piece, int limit, int start_offset)
Array	split (const std::string &piece, int limit, int start_offset, int end_offset)
Array	split (const std::string &piece, std::vector< int > positions)
std::string	replace (const std::string &piece, const std::string &with)
Public Attributes
bool	did_match
int	num_matches

Pcre Class Reference

Public Member Functions

Public Attributes

Detailed Description

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation