Parse a CSV file with Qt with regex or by specifying the characters delimiters, escape and quote

CSVParser.cpp

class CSVParser
{
public:
    CSVParser() {}

    static int parseString(QString &buffer, QStringList &fields, QString delimChars, QString quoteChars, QString escapeChars) {
        QString field;             // String in which to accumulate next field
        bool escaped = false;      // Next char is escaped
        bool quoted = false;       // In quotes
        QChar quoteChar = 0;       // Actual quote character used to open quotes
        bool started = false;      // Non-blank chars in field or quotes started
        bool ended = false;        // Quoted field ended
        QString endChars = "\n\r";
        int cp = 0;                // Pointer to the next character in the buffer
        int cpmax = buffer.size(); // End of string

        while ( true )
        {
          QChar c = buffer[cp];
          cp++;

          // If end of line then if escaped or buffered then try to get more...
          if ( cp > cpmax )
          {
            if ( quoted || escaped )
            {
                return 0;
            }
            break;
          }

          // If escaped, then just append the character
          if ( escaped )
          {
            field.append( c );
            escaped = false;
            continue;
          }

          // Determine if this is a special character - test each class in turn
          // Note that delimiters are not valid as quotes or escape character
          //
          // Somewhat convoluted logic around quote and escape chars is
          // to enforce logic for escape characters that are also quote characters.
          // These escapes can only escape themselves and only in quotes using them
          // as delimiters!

          bool isQuote = false;
          bool isEscape = false;
          bool isDelim = delimChars.contains( c );
          if ( ! isDelim )
          {
            bool isQuoteChar = quoteChars.contains( c );
            isQuote = quoted ? c == quoteChar : isQuoteChar;
            isEscape = escapeChars.contains( c );
            if ( isQuoteChar && isEscape ) isEscape = isQuote;
          }

          // Start or end of quote ...
          if ( isQuote )
          {
            // quote char in quoted field
            if ( quoted )
            {
              // if is also escape and next character is quote, then
              // escape the quote..
              if ( isEscape && buffer[cp] == quoteChar )
              {
                field.append( quoteChar );
                cp++;
              }
              // Otherwise end of quoted field
              else
              {
                quoted = false;
                ended =  true;
              }
            }
            // quote char at start of field .. start of quoted fields
            else if ( ! started )
            {
              field.clear();
              quoteChar = c;
              quoted = true;
              started = true;
            }
            // Cannot have a quote embedded in a field
            else
            {
              fields.clear();
              return 0;
            }
          }
          // If escape char, then next char is escaped...
          else if ( isEscape )
          {
            escaped = true;
          }
          // If within quotes, then append to the string
          else if ( quoted )
          {
            field.append( c );
          }
          // If it is a delimiter, then end of field...
          else if ( isDelim )
          {
            fields.append(field);

            // Clear the field
            field.clear();
            started = false;
            ended = false;
          }
          // End of the string
          else if (endChars.contains(c))
          {
              break;
          }
          // Whitespace is permitted before the start of a field, or
          // after the end..
          else if ( c.isSpace() )
          {
            if ( ! ended ) field.append( c );
          }
          // Other chars permitted if not after quoted field
          else
          {
            if ( ended )
            {
              fields.clear();
              return 0;
            }
            field.append( c );
            started = true;
          }
        }
        // If reached the end of the record, then add the last field...
        if ( started )
        {
          fields.append(field);
        }

        return 1;
    }

    static int parseRegEx(QString &buffer, QStringList &fields, QString regEx) {
        QRegExp rx(regEx);

        if(!rx.isValid()) {
            return 0;
        }
        int pos = rx.indexIn(buffer);
        if(pos == -1) {
            return 0;
        }
        QStringList list = rx.capturedTexts();
        for(int i=1;i<list.count();++i){
            fields.append(list[i]);
        }
        return 1;
    }

    static int parseCSV(QString filename, QVector<QMap<QString,QString> > &fields, QString delim, QString quote="\"", QString escape="\\") {
        QFile file(filename);
        if (!file.open(QIODevice::ReadOnly)) {
            return 1;
        }

        // The file necessarly has a header
        QStringList headerLine;
        QString line = QString(file.readLine()).split(QRegExp("[\r\n]")).at(0);
        parseString(line,headerLine,delim,quote,escape);
        while (!file.atEnd()) {
            line = QString(file.readLine()).split(QRegExp("[\r\n]")).at(0);
            if(line.isEmpty())
                continue;
            QStringList values;
            parseString(line,values,delim,quote,escape);
            QMap<QString,QString> map = QMap<QString,QString>();
            for (int i = 0; i < values.length(); i++) {
                map.insert(headerLine.at(i), values.at(i)); // maps the header with corresponding value
            }
            fields.append(map);
        }

        file.close();

        return 0;
    }
};