A simple helper function to handle escapes in parsing, you may choose the kind of error handling you want (by return value or by exception) and it is really easily converted to C.

escapeChar.cpp

//#include <stdexcept>

/// @warning The parameter is also the return value.
/// @return true if the escape sequence was valid, false otherwise
bool escapeChar( char& c ) {
    switch( c ) {
        case 't':
            c = '\t';
            break;
        case 'n':
            c = '\n';
            break;
        case '\n':
            return true;
        case ' ':
        case '\\':
        case '"':
            break;
        default:
            //throw std::runtime_error("Undefined escape sequence.");
            return false;
    }
    return true;
}