Template class problem

[costingeana]

Hi!



I am new in Visual C++ and now I face with a problem.



I have the below code written into a header file. At compile time I get the following error:



error C2248: 'CRCTable' : cannot access private struct declared in class 'CRCHash<unsigned long,-306674912,-1,-1>'

see declaration of 'CRCTable'

while compiling class-template static data member 'const struct CRCHash<unsigned long,-306674912,-1,-1>::CRCTable CRCHash<unsigned long,-306674912,-1,-1>::Table'



What shoul I do to get rid of this error?

Thanks in advance!

#ifndef CRCHashH
#define CRCHashH
 
//******************************************************************************
// Template class 'CRCHash' implements mirror-algorithm of CRC calculation.
 
template <typename T, const T POLYNOM, const T INITIAL, const T FINAL>
class CRCHash
    {
    private:
        T CRC;
        struct CRCTable { T Data[256]; CRCTable(void); };
        static const CRCTable Table;
    public:
        CRCHash(void) : CRC(INITIAL) {;};
        CRCHash(const CRCHash & iCRCHash) : CRC(iCRCHash.CRC) {;};
        void Reset(void) { CRC = INITIAL; };
        void Update(const void *Buffer, size_t Length);
        inline void Update(unsigned char Value);
        T Evaluate(void) const { return CRC ^ FINAL; };
        static T Evaluate(const void *Buffer, size_t Length);
    };
 
template <typename T, T POLYNOM, T INITIAL, T FINAL>
    const CRCHash<T, POLYNOM, INITIAL, FINAL>::CRCTable
        CRCHash<T, POLYNOM, INITIAL, FINAL>::Table;
 
//******************************************************************************
 
 
template <typename T, T POLYNOM, T INITIAL, T FINAL>
    CRCHash<T, POLYNOM, INITIAL, FINAL>::
        CRCTable::CRCTable(void)
            {
            for (int i = 0, t = 0; i < 256; t = 8, i++)
                {
                Data[i] = i;
                while (t--) Data[i] = Data[i] >> 1 ^ (Data[i] & 1 ? POLYNOM :0);
                }
            }
 
//******************************************************************************
 
template <typename T, T POLYNOM, T INITIAL, T FINAL>
    void CRCHash<T, POLYNOM, INITIAL, FINAL>::
        Update(unsigned char Value)
            {
            CRC = CRC >> 8 ^ Table.Data[Value ^ CRC & 0xFFU];
            }
 
//******************************************************************************
 
template <typename T, T POLYNOM, T INITIAL, T FINAL>
    void CRCHash<T, POLYNOM, INITIAL, FINAL>::
        Update(const void *Buffer, size_t Length)
           {
           register const unsigned char * Block =
               static_cast<const unsigned char *>(Buffer);
           while (Length--) Update(*Block++);
           }
 
//******************************************************************************
 
template <typename T, T POLYNOM, T INITIAL, T FINAL>
    T CRCHash<T, POLYNOM, INITIAL, FINAL>::
        Evaluate(const void *Buffer, size_t Length)
            {
            CRCHash Instance;
            Instance.Update(Buffer, Length);
            return Instance.Evaluate();
            }
 
//******************************************************************************
 
typedef unsigned char  CRC08;
typedef unsigned short CRC16;
typedef unsigned long  CRC32;
 
class CRC08Hash : public CRCHash<CRC08, 0x8CU, 0xFFU, 0xFFU> {};
class CRC16Hash : public CRCHash<CRC16, 0xA001U, 0x0000U, 0x0000U> {};
class CRC32Hash : public CRCHash<CRC32, 0xEDB88320UL, 0xFFFFFFFFUL, 0xFFFFFFFFUL> {};
 
//******************************************************************************
 
// typedef unsigned __int64 CRC64;
// class CRC64Hash : public CRCHash<CRC64, 0x000000000000001BUI64, 0xFFFFFFFFFFFFFFFFUI64, 0xFFFFFFFFFFFFFFFFUI64> {};
 
//******************************************************************************
 
#endif

[Savage]

This compiles in Borland C++ builder..but in VC++(although I didn't tested,I sawed this from your post) it doesn't,it's whining about that static member of yours,Table when it reaches:

 class CRC32Hash : public CRCHash<CRC32, 0xEDB88320UL, 0xFFFFFFFFUL, 0xFFFFFFFFUL> {};

I wanted to ask you for what purposes do you need that member to be static?
Have you tried compiling without static keyword at Table definition?

Savage