How do I implement a CString hash function for use with std::unordered_map?

Question

I want to declare :

std::unordered_map m_mapMyMap;

But when I build I got an error telling me that the standard C++

Answer 1

Based on the MS STL implementation for std::string I created the following methods which can be used for std::unordered_set and std::unordered_map:

namespace std {
    template <>
    struct hash
    {   // hash functor for CString
        size_t operator()(const CString& _Keyval) const
        {   // hash _Keyval to size_t value by pseudorandomizing transform
            return (_Hash_seq((const unsigned char*)(LPCWSTR)_Keyval, _Keyval.GetLength() * sizeof(wchar_t)));
        }
    };

    template <>
    struct hash
    {   // hash functor for CStringA
        size_t operator()(const CStringA& _Keyval) const
        {   // hash _Keyval to size_t value by pseudorandomizing transform
            return (_Hash_seq((const unsigned char*)(LPCSTR)_Keyval, _Keyval.GetLength() * sizeof(char)));
        }
    };
}

Or even more generic:

namespace std {
    template
    struct hash> : public unary_function, size_t>
    {   // hash functor for CStringT
        typedef CStringT _Kty;

        size_t operator()(const _Kty& _Keyval) const
        {   // hash _Keyval to size_t value by pseudorandomizing transform
            return (_Hash_seq((const unsigned char*)(StringTraits::PCXSTR)_Keyval,
                _Keyval.GetLength() * sizeof(BaseType)));
        }
    };
}