c++ misc code 继承和模板

#include <iostream>
#include <cstdint>
#include <atomic>

using namespace std;

template<typename ERange>
class CGlobalSeqT
{
public:
    typedef uint32_t SEQ_T;

    static SEQ_T Gen(bool next = true)
    {
        static CGlobalSeqT<ERange> instance;
        if (next)
        {
            return instance.Next();
        }
        else
        {
            instance.Reset();
            return 0;
        }
    }

private:
    CGlobalSeqT()
        : m_min((SEQ_T)ERange::MIN)
        , m_max((SEQ_T)ERange::MAX)
        , m_seq((SEQ_T)ERange::MIN - 1)
    {
        static_assert((SEQ_T)ERange::MIN < (SEQ_T)ERange::MAX, "invalid range");
    }

    inline uint32_t Next()
    {
        SEQ_T expected_max = m_max;
        if (m_seq.compare_exchange_strong(expected_max, m_min))
        {
            return m_min;
        }
        else
        {
            return ++m_seq;
        }
    }

    inline void Reset()
    {
        m_seq = m_min - 1;
    }

    SEQ_T m_min;
    SEQ_T m_max;
    std::atomic<SEQ_T> m_seq;
};

class CInboundGlobalSeq : public CGlobalSeqT<CInboundGlobalSeq>
{
public:
    enum ERange { MIN = 0, MAX = UINT32_MAX };
};

class COutboundGlobalSeq : public CGlobalSeqT<COutboundGlobalSeq>
{
public:
    enum ERange { MIN = 2000, MAX = 2002 };
};

int main()
{
    cout << "inbound:" << CInboundGlobalSeq::Gen() << "," << CInboundGlobalSeq::Gen() << endl;
    cout << "1.outbound:"
         << COutboundGlobalSeq::Gen() << ","
         << COutboundGlobalSeq::Gen() << ","
         << COutboundGlobalSeq::Gen() << ","
         << COutboundGlobalSeq::Gen() << endl;
    COutboundGlobalSeq::Gen(false);
    cout << "2.outbound:" << COutboundGlobalSeq::Gen() << "," << COutboundGlobalSeq::Gen() << endl;
    return 0;
}