bool is_gzipped(std::string filename) {
    std::ifstream in_file;
    char byte1, byte2;

    in_file.open(filename, ios::binary|ios::ate);
    if (in_file.is_open()) {
        in_file.seekg(0, ios::beg);
        std::string bytes;
        in_file.read(&byte1, 1);
        in_file.read(&byte2, 1);
        in_file.close();
    } else {
        throw std::exception();
    }

    return (reinterpret_cast<unsigned char &>(byte1) == 0x1f) &&
           (reinterpret_cast<unsigned char &>(byte2) == 0x8b);
}