问C++在模块之间共享数组元素，且仅具有少量字段的常量

EN

template <class T> class CProtectedArray {
private:
    T*              m_aItems;
    unsigned int*   m_aMask;
public:
    CProtectedArray(int cElem, bool fInitialProtect) : m_aItems(NULL)  {
        int cbElem = sizeof(T)*cElem;
        int cbMask = sizeof(int)*(cElem+31)/32;
        m_aItems = (T*)malloc(cbElem + cbMask);
        m_aMask = (unsigned int*)(m_aItems + cElem);
        memset(m_aItems, 0, cbElem);
        memset(m_aMask, fInitialProtect ? -1 : 0, cbMask);
    }
    ~CProtectedArray() {
        if (m_aItems)
            free(m_aItems);
    }
    bool IsProtected(int iItem)     { return !!(m_aMask[iItem>>5] & (1<<(iItem&31))); }
    void Protect(int iItem)         { m_aMask[iItem>>5] |= 1<<(iItem&31); }
    void UnProtect(int iItem)       { m_aMask[iItem>>5] &= ~(1<<(iItem&31)); }
    void Set(int iItem, T val) {
        if (!IsProtected(iItem))
            m_aItems[iItem] = val;
    }
};

int main(int argc, char* argv[])
{
    CProtectedArray<int> A(100, true);
    bool f = A.IsProtected(30);  // f = true
    A.Set(30, 23);  // nothing happens
    A.UnProtect(30); 
    f = A.IsProtected(30);  // f = false
    A.Set(30, 24); // sets element 30 to 24
    A.Protect(30); 
    f = A.IsProtected(30);  // f = true
    A.Set(30, 25);  // nothing happens
}