Boost logo

Boost :

From: Dick Bridges (dbridges_at_[hidden])
Date: 2006-01-02 19:57:02

I am trying to use Xpressive for parsing string-based message buffers.

The messages start with a fixed string and end with an "empty" line

(similar in form to HTTP). There is an example in the code below.


Following a successful search, I'd like to be able process messages

in the buffer with something like this pseudo code:


  for each message

    for each name_value pair

      make_pair(name, value)

  prepend what.suffix() to the next packet


The examples of repeating an embedded regex I found in the

.pdf and the examples subdirectory seemed close to what I need

but I have not been able to make them work.


Here is code that is the closest I've been able to get:


#include <iostream>

#include <boost/xpressive/xpressive.hpp>


using namespace std;

using namespace boost::xpressive;



main(int argc, char **argv) {


  std::string buffer =


    "Volume = 1\r\n"

    "Other1= 2\r\n"


    "Other =4\r\n"



    "Volume = 5\r\n"

    "Other1= 6\r\n"


    "Other =8\r\n"



    "Volume = 9\r\n"

    "Other1= 0\r\n"



    sregex name_value_pair_ =

      (+alnum >> *_s >> "=" >> *_s >> +_d >> *_s >> _ln);


    sregex message_ =

      (*_s >> "FROGGIE" >> _ln >> +name_value_pair_ >> _ln);


    sregex re_ = +(s1= message_);


    smatch what;


    if( regex_search( buffer, what, re_ ) ) {


      cout << "\n<what.size()>" << what.size() << "</what.size()>"

        << "\n<what[0]>\n" << what[0] << "</what[0]>"

      << "\n<what[1]>\n" << what[1] << "</what[1]>"

      << "\n<what[2]>\n" << what[2] << "</what[2]>"

      << "\n<what.suffix()>\n" << what.suffix() << "</what.suffix()>"

      << endl;



} // main


I am not very accomplished with regular expressions but what[0] and

what.suffix() look correct and I hoped that what.size() held the

number of messages and what[1] and what[2] accessed each in turn.

I clearly did not understand.





Volume = 1

Other1= 2


Other =4



Volume = 5

Other1= 6


Other =8





Volume = 5

Other1= 6


Other =8







Volume = 9

Other1= 0




OS is Linux Core 3 2.6.9-1.667. Compiler is gcc 3.4.4-linux.

Xpressive README.txt (in the .zip) says "xpressive 0.9.8d".


If someone could point me in the right direction, I'd surely

appreciate it.



Dick Bridges


Boost list run by bdawes at, gregod at, cpdaniel at, john at