C / C++ / MFC

#define BLOCK_SOCK_TIMEOUT 15

class CBlockingSocketFile : public CFile  
{
	DECLARE_DYNAMIC(CBlockingSocketFile)
public:
//Constructors
	CBlockingSocketFile(CBlockingSocket *pNewSocket);
	virtual ~CBlockingSocketFile();

// Implementation
public:
	CBlockingSocket * pSocket;

	virtual UINT Read(void * pBuffer, UINT nBytes);
	virtual void Write(const void* pBuffer, UINT nBytes);
	virtual void Close();

private:
// Unsupported APIs
	virtual BOOL Open(LPCTSTR lpszFileName, UINT nOpenFlags, CFileException* pError = NULL);
	virtual CFile* Duplicate() const;
	virtual DWORD GetPosition() const;
	virtual LONG Seek(LONG lOff, UINT nFrom);
	virtual void SetLength(DWORD dwNewLen);
	virtual DWORD GetLength() const;
	virtual void LockRange(DWORD dwPos, DWORD dwCount);
	virtual void UnlockRange(DWORD dwPos, DWORD dwCount);
	virtual void Flush();
	virtual void Abort();
};

IMPLEMENT_DYNAMIC(CBlockingSocketFile, CFile);

//////////////////////////////////////////////////////////////////////
// Construction/Destruction
//////////////////////////////////////////////////////////////////////

CBlockingSocketFile::CBlockingSocketFile(CBlockingSocket *pNewSocket)
{
	if(pNewSocket == NULL) {
		DEBUG_LOG("CBlockingSocketFile constructor: NULL pointer assignment.");
		AfxThrowUserException();
	}
	pSocket = pNewSocket;
}

CBlockingSocketFile::~CBlockingSocketFile()
{

}

UINT CBlockingSocketFile::Read(void *pBuffer, UINT nBytes)
{
	return pSocket->Receive((char *)pBuffer, (const int)nBytes, BLOCK_SOCK_TIMEOUT);
}

void CBlockingSocketFile::Write(const void *pBuffer, UINT nBytes)
{
	pSocket->Write((const char*)pBuffer, (const int)nBytes, BLOCK_SOCK_TIMEOUT);
}

void CBlockingSocketFile::Close()
{
	pSocket->Close();
}

// Unsupported APIs
BOOL Open(LPCTSTR lpszFileName, UINT nOpenFlags, CFileException* pError = NULL)
{ 
	return false;
}

CFile* Duplicate(){return NULL;}
DWORD GetPosition(){return 0;}
LONG Seek(LONG lOff, UINT nFrom){return 0;}
void SetLength(DWORD dwNewLen){}
DWORD GetLength(){return 0;}
void LockRange(DWORD dwPos, DWORD dwCount){}
void UnlockRange(DWORD dwPos, DWORD dwCount){}
void Flush(){}
void Abort(){}

<br />
// workaround 1<br />
<br />
if (fp = fopen(filename, "cwt"), fp != NULL)<br />
{<br />
  // do stuff<br />
}<br />
else<br />
  perror( ... );<br />
<br />
// the inclusion of the 'c' switch caused<br />
// a)  fopen() to return NULL<br />
// b)  perror() to report "no error"<br />
<br />
// workaround 2<br />
<br />
if (h = _open(filename, _O_CREAT|_O_TRUNC|_O_WRONLY|_O_TEXT), h != -1)<br />
{<br />
  // do stuff<br />
}<br />
else<br />
  perror( ... );<br />
<br />
// resorting to raw I/O was less ambiguous ...<br />
// _open returned -1<br />
// perror() reported Permission denied for reasons which are simply beyond me<br />