callback.cpp

opc的客户端程序,在csdn上下的,不过我想看看这里下的详细说明

//---------------------------------------------------------
// OPC Custom 2.0 Sample
// Asynchronous IO with MFC and ATL
// (c) Siemens AG 2000
//---------------------------------------------------------

//
// callback.cpp : Defines the class behaviors for the callback
//				  This callback object receives the connection point 
//				  callbacks from the OPC server
//

//#include "pre_opc.h"		// for OPC: include MFC, ATL and OPC header files - for OPC only
//#include "OPCDA_Async.h"	// include class declaration for application class
//#include "OPCDA_AsyncDlg.h" // include class declaration of dialog class
#include "stdafx.h"

#include "Callback.h"		// for OPC: include class declaration fpr this callback class


							// for OPC: prototype for a helper function to get OPC quality 
							//          text description from quality code

/////////////////////////////////////////////////////////////////////////////
//
// IOPCDataCallback - implementation

// OnDataChange called by OPC server when the OPC server has detected modified data 
// (being called only when group and item is set to active)

STDMETHODIMP COPCDataCallback:: OnDataChange( 
            /* [in] */ DWORD dwTransid,
            /* [in] */ OPCHANDLE hGroup,
            /* [in] */ HRESULT hrMasterquality,
            /* [in] */ HRESULT hrMastererror,
            /* [in] */ DWORD dwCount,
            /* [size_is][in] */ OPCHANDLE __RPC_FAR *phClientItems,
            /* [size_is][in] */ VARIANT __RPC_FAR *pvValues,
            /* [size_is][in] */ WORD __RPC_FAR *pwQualities,
            /* [size_is][in] */ FILETIME __RPC_FAR *pftTimeStamps,
            /* [size_is][in] */ HRESULT __RPC_FAR *pErrors)
	{
		
	    // The input parameters dwTransid, hGroup, hrMasterquality, hrMastererror, pErrors are not checked within this sample...	

		return S_OK;
	}

//
// OnReadComplete is being called by OPC server when an async read request has been carried out
//

STDMETHODIMP  COPCDataCallback::OnReadComplete( 
		/* [in] */ DWORD dwTransid,
		/* [in] */ OPCHANDLE hGroup,
		/* [in] */ HRESULT hrMasterquality,
		/* [in] */ HRESULT hrMastererror,
		/* [in] */ DWORD dwCount,
		/* [size_is][in] */ OPCHANDLE __RPC_FAR *phClientItems,
		/* [size_is][in] */ VARIANT __RPC_FAR *pvValues,
		/* [size_is][in] */ WORD __RPC_FAR *pwQualities,
		/* [size_is][in] */ FILETIME __RPC_FAR *pftTimeStamps,
		/* [size_is][in] */ HRESULT __RPC_FAR *pErrors)
	{
	
		
 	    // The input parameters dwTransid, hGroup, hrMasterquality, hrMastererror, pErrors are not checked within this sample...	

		return S_OK;
	}


//
// OnWriteComplete called by OPC server when an async write request has been carried out
//
STDMETHODIMP  COPCDataCallback::OnWriteComplete( 
        /* [in] */ DWORD dwTransid,
        /* [in] */ OPCHANDLE hGroup,
        /* [in] */ HRESULT hrMastererr,
        /* [in] */ DWORD dwCount,
        /* [size_is][in] */ OPCHANDLE __RPC_FAR *pClienthandles,
        /* [size_is][in] */ HRESULT __RPC_FAR *pErrors)
	{

		/* Display Error Text */


		return S_OK;
	}

//
// Converts opc quality codes into text strings
//