www.pudn.com > WDM_CharSample.rar > OpenByIntf.cpp

// OpenByIntf.cpp - open device by device interface 
// Copyright (c) 1998 Compuware Corporation 
 
#define NOCRYPT			// prevent attempt to include missing files 
#define _INC_EXCPT		// prevent excpt.h from being included 
 
#include  
#include  
#include  
#include 	// DriverWorks 
 
// OpenByInterface 
// 
// Opens the nth device found with the given interface class 
 
HANDLE OpenByInterface( 
		GUID* pClassGuid,	// points to the GUID that identifies the interface class 
		DWORD instance,		// specifies which instance of the enumerated devices to open 
		PDWORD pError		// address of variable to receive error status 
		) 
{ 
	HANDLE hDev; 
	CDeviceInterfaceClass DevClass(pClassGuid, pError); 
 
	if (*pError != ERROR_SUCCESS) 
		return INVALID_HANDLE_VALUE; 
 
	CDeviceInterface DevInterface(&DevClass, instance, pError); 
 
	if (*pError != ERROR_SUCCESS) 
		return INVALID_HANDLE_VALUE; 
 
	hDev = CreateFile( 
		DevInterface.DevicePath(), 
		GENERIC_READ | GENERIC_WRITE, 
		FILE_SHARE_READ | FILE_SHARE_WRITE, 
		NULL, 
		OPEN_EXISTING, 
		FILE_ATTRIBUTE_NORMAL, 
		NULL 
		); 
 
	if (hDev == INVALID_HANDLE_VALUE) 
		*pError = GetLastError(); 
 
	return hDev; 
}