def decode_packet_number(truncated: int, num_bits: int, expected: int) -> int:
    """
    Recover a packet number from a truncated packet number.

    See: Appendix A - Sample Packet Number Decoding Algorithm
    """
    window = 1 << num_bits
    half_window = window // 2
    candidate = (expected & ~(window - 1)) | truncated
    if candidate <= expected - half_window and candidate < (1 << 62) - window:
        return candidate + window
    elif candidate > expected + half_window and candidate >= window:
        return candidate - window
    else:
        return candidate

    Recover a packet number from a truncated packet number.

    See: Appendix A - Sample Packet Number Decoding Algorithm
    
src/aioquic/quic/packet.py