Question

So I have the following string of data, which is being received through a TCP winsock connection, and would like to do an advanced tokenization, into a vector of structs, where each struct represents one record.

std::string buf = "44:william:adama:commander:stuff\n33:luara:roslin:president:data\n"

struct table_t
{
    std::string key;
    std::string first;
    std::string last;
    std::string rank;
    std::additional;
};

Each record in the string is delimited by a carriage return. My attempt at splitting up the records, but not yet splitting up the fields:

    void tokenize(std::string& str, std::vector< string >records)
{
    // Skip delimiters at beginning.
    std::string::size_type lastPos = str.find_first_not_of("\n", 0);
    // Find first "non-delimiter".
    std::string::size_type pos     = str.find_first_of("\n", lastPos);
    while (std::string::npos != pos || std::string::npos != lastPos)
    {
        // Found a token, add it to the vector.
        records.push_back(str.substr(lastPos, pos - lastPos));
        // Skip delimiters.  Note the "not_of"
        lastPos = str.find_first_not_of("\n", pos);
        // Find next "non-delimiter"
        pos = str.find_first_of("\n", lastPos);
    }
}

It seems totally unnecessary to repeat all of that code again to further tokenize each record via the colon (internal field separator) into the struct and push each struct into a vector. I’m sure there is a better way of doing this, or perhaps the design is in itself wrong.

Thank you for any help.

Answer 1

For breaking the string up into records, I’d use istringstream, if only
because that will simplify the changes later when I want to read from
a file. For tokenizing, the most obvious solution is boost::regex, so:

std::vector<table_t> parse( std::istream& input )
{
    std::vector<table_t> retval;
    std::string line;
    while ( std::getline( input, line ) ) {
        static boost::regex const pattern(
            "\([^:]*\):\([^:]*\):\([^:]*\):\([^:]*\):\([^:]*\)" );
        boost::smatch matched;
        if ( !regex_match( line, matched, pattern ) ) {
            //  Error handling...
        } else {
            retval.push_back(
                table_t( matched[1], matched[2], matched[3],
                         matched[4], matched[5] ) );
        }
    }
    return retval;
}

(I’ve assumed the logical constructor for table_t. Also: there’s a very
long tradition in C that names ending in _t are typedef’s, so you’re
probably better off finding some other convention.)