C / C++ / MFC

class WinFileInInterface<br />
{<br />
public:<br />
	virtual BOOL Open(LPCTSTR lpszFileName) = 0;<br />
	virtual BOOL DoReadFile(LPVOID lpBuffer, DWORD nNumberOfBytesToRead) = 0;<br />
};<br />
<br />
class WinFileOutInterface<br />
{<br />
public:<br />
	virtual BOOL Open(LPCTSTR lpszFileName) = 0;<br />
	virtual BOOL DoWriteFile(LPCVOID lpBuffer, DWORD nNumberOfBytesToWrite) = 0;<br />
};

Compiling...
winiotest.cpp
C:\C++\Projects\[Tests]\winiotest\winiotest.cpp(29) : error C2259: 'CWinFileInOut' : cannot instantiate abstract class due to following members:
        c:\c++\projects\[tests]\winiotest\cwinfileio.h(109) : see declaration of 'CWinFileInOut'
C:\C++\Projects\[Tests]\winiotest\winiotest.cpp(29) : warning C4259: 'int __thiscall WinFileInInterface::DoReadFile(void *,unsigned long)' : pure virtual function was not defined
        c:\c++\projects\[tests]\winiotest\cwinfileio.h(73) : see declaration of 'DoReadFile'
C:\C++\Projects\[Tests]\winiotest\winiotest.cpp(29) : warning C4259: 'int __thiscall WinFileOutInterface::DoWriteFile(const void *,unsigned long)' : pure virtual function was not defined
        c:\c++\projects\[tests]\winiotest\cwinfileio.h(80) : see declaration of 'DoWriteFile'
C:\C++\Projects\[Tests]\winiotest\winiotest.cpp(29) : error C2259: 'CWinFileInOut' : cannot instantiate abstract class due to following members:
        c:\c++\projects\[tests]\winiotest\cwinfileio.h(109) : see declaration of 'CWinFileInOut'
C:\C++\Projects\[Tests]\winiotest\winiotest.cpp(29) : warning C4259: 'int __thiscall WinFileInInterface::DoReadFile(void *,unsigned long)' : pure virtual function was not defined
        c:\c++\projects\[tests]\winiotest\cwinfileio.h(73) : see declaration of 'DoReadFile'
C:\C++\Projects\[Tests]\winiotest\winiotest.cpp(29) : warning C4259: 'int __thiscall WinFileOutInterface::DoWriteFile(const void *,unsigned long)' : pure virtual function was not defined
        c:\c++\projects\[tests]\winiotest\cwinfileio.h(80) : see declaration of 'DoWriteFile'

struct WFIOInfo
{	HANDLE m_hFile;	
	DWORD m_dwBytes;
};

class WinFileInInterface
{
public:	
	virtual BOOL Open(LPCTSTR lpszFileName);	
	virtual BOOL DoReadFile(LPVOID lpBuffer, DWORD nNumberOfBytesToRead);
};

class WinFileOutInterface
{
public:	
	virtual BOOL Open(LPCTSTR lpszFileName);	
	virtual BOOL DoWriteFile(LPCVOID lpBuffer, DWORD nNumberOfBytesToWrite);
};

class CWinFileIn : private WFIOInfo, public WinFileInInterface
{
public:	
	virtual BOOL Open(LPCTSTR lpszFileName)	
	{return TRUE;}	
	virtual BOOL DoReadFile(LPVOID lpBuffer, DWORD nNumberOfBytesToRead)	
	{return ::ReadFile(m_hFile, lpBuffer, nNumberOfBytesToRead, &m_dwBytes, NULL);}
};

class CWinFileOut : private WFIOInfo, WinFileOutInterface
{
public:	
	virtual BOOL Open(LPCTSTR lpszFileName)	{return TRUE;}	
	virtual BOOL DoWriteFile(LPCVOID lpBuffer, DWORD nNumberOfBytesToWrite)
	{return ::WriteFile(m_hFile, lpBuffer, nNumberOfBytesToWrite, &m_dwBytes, NULL);}
};

class CWinFileInOut : private: WFIOInfo, 
		      public: WinFileInInterface, 
  		      public: WinFileOutInterface
{
public:	
	BOOL Open(LPCTSTR lpszFileName)	
	{	return TRUE;	}
};

"One must learn from the bite of the fire to leave it alone." - Native American Proverb