Unfortunately the Data File Data Source is in one of our private repositories, so I cannot link you to the source code directly.

The parser being used is a au.com.bytecode.opencsv.CSVReader.CSVReader which is getting its separator, quote character, and escape character from the AbstractCSVDataSource class, unless you override the methods providing these in your implementing class, i.e.

@Override
public char getSeparatorCharacter() {
    return ','; //split on commas
}

@Override
public char getQuoteCharacter() {
    return '"'; //unless the commas are in quote pairs
}

@Override
public char getEscapeCharacter() {
    return '\\';
}

It will pass each line that it reads as it reads and parses it to the import row function.