CppCoreGuidelines C.122 如果接口和实现要彻底分开，请使用抽象类作为接口

struct Device {
    virtual ~Device() = default;
    virtual void write(span<const char> outbuf) = 0;
    virtual void read(span<char> inbuf) = 0;
};

class D1 : public Device {
    // ... data ...

    void write(span<const char> outbuf) override;
    void read(span<char> inbuf) override;
};

class D2 : public Device {
    // ... different data ...

    void write(span<const char> outbuf) override;
    void read(span<char> inbuf) override;
};