MFC CString转化为char*

如题  CString转化为char*

char* str2char(CString str)

{
char *ptr;
#ifdef _UNICODE
LONG len;
len = WideCharToMultiByte(CP_ACP, 0, str, -1, NULL, 0, NULL, NULL);
ptr = new char[len + 1];
memset(ptr, 0, len + 1);
WideCharToMultiByte(CP_ACP, 0, str, -1, ptr, len + 1, NULL, NULL);
#else
ptr = new char[str.GetAllocLength() + 1];
sprintf(ptr, _T("%s"), str);
#endif
return ptr;
}