gistfile1.txt

void testM()
{


    
    // 37 78 81 85 27 68  07 4d 21 11 20 11 71 05 57 65 00 00
    // 37 78 81 85 27 68  07 4d 21 11 20 11 71  5 57 65 00 00
    // track2 4-bit BCD encode
    std::string track2 = "377881852768074=211120117105576500001";
    std::string encoded = "";
    uint8_t acc = 0;
    bool full = false;
    for (uint8_t c : track2)
    {
        if (!full)
        {
            acc = c - 0x30;
            acc <<= 4;
            full = !full;
        }
        else
        {
            acc |= c - 0x30;
            std::cout<<
                std::hex<< unsigned(acc) << " ";
            encoded.append(1, acc);
            acc = 0;
            full = !full;
        }
    }
}
///https://ryandeangraham.medium.com/track2-character-encoding-61d6150ecb95