函数指针数组

//函数指针数组

static NTSTATUS (*fcntab[])(PDEVICE_EXTENSION pdx, PIRP Irp) = 
	{
		DefaultPnpHandler,		// IRP_MN_START_DEVICE
		DefaultPnpHandler,		// IRP_MN_QUERY_REMOVE_DEVICE
		HandleRemoveDevice,		// IRP_MN_REMOVE_DEVICE
		DefaultPnpHandler,		// IRP_MN_CANCEL_REMOVE_DEVICE
		DefaultPnpHandler,		// IRP_MN_STOP_DEVICE
		DefaultPnpHandler,		// IRP_MN_QUERY_STOP_DEVICE
		DefaultPnpHandler,		// IRP_MN_CANCEL_STOP_DEVICE
		DefaultPnpHandler,		// IRP_MN_QUERY_DEVICE_RELATIONS
		DefaultPnpHandler,		// IRP_MN_QUERY_INTERFACE
		DefaultPnpHandler,		// IRP_MN_QUERY_CAPABILITIES
		DefaultPnpHandler,		// IRP_MN_QUERY_RESOURCES
		DefaultPnpHandler,		// IRP_MN_QUERY_RESOURCE_REQUIREMENTS
		DefaultPnpHandler,		// IRP_MN_QUERY_DEVICE_TEXT
		DefaultPnpHandler,		// IRP_MN_FILTER_RESOURCE_REQUIREMENTS
		DefaultPnpHandler,		// 
		DefaultPnpHandler,		// IRP_MN_READ_CONFIG
		DefaultPnpHandler,		// IRP_MN_WRITE_CONFIG
		DefaultPnpHandler,		// IRP_MN_EJECT
		DefaultPnpHandler,		// IRP_MN_SET_LOCK
		DefaultPnpHandler,		// IRP_MN_QUERY_ID
		DefaultPnpHandler,		// IRP_MN_QUERY_PNP_DEVICE_STATE
		DefaultPnpHandler,		// IRP_MN_QUERY_BUS_INFORMATION
		DefaultPnpHandler,		// IRP_MN_DEVICE_USAGE_NOTIFICATION
		DefaultPnpHandler,		// IRP_MN_SURPRISE_REMOVAL
	};

根据ULONG fcn = stack->MinorFunction;，判断要调用哪一个函数，既没有用if-else,也没有用switch-case

/************************************************************************
* 函数名称:HelloWDMPnp
* 功能描述:对即插即用IRP进行处理
* 参数列表:
      fdo:功能设备对象
      Irp:从IO请求包
* 返回 值:返回状态
*************************************************************************/
#pragma PAGEDCODE
NTSTATUS HelloWDMPnp(IN PDEVICE_OBJECT fdo,
                        IN PIRP Irp)
{
	PAGED_CODE();

	KdPrint(("Enter HelloWDMPnp\n"));
	NTSTATUS status = STATUS_SUCCESS;
	PDEVICE_EXTENSION pdx = (PDEVICE_EXTENSION) fdo->DeviceExtension;//得到设备扩展结构
	PIO_STACK_LOCATION stack = IoGetCurrentIrpStackLocation(Irp);//得到当前IRP的堆栈
	static NTSTATUS (*fcntab[])(PDEVICE_EXTENSION pdx, PIRP Irp) = 
	{
		DefaultPnpHandler,		// IRP_MN_START_DEVICE
		DefaultPnpHandler,		// IRP_MN_QUERY_REMOVE_DEVICE
		HandleRemoveDevice,		// IRP_MN_REMOVE_DEVICE
		DefaultPnpHandler,		// IRP_MN_CANCEL_REMOVE_DEVICE
		DefaultPnpHandler,		// IRP_MN_STOP_DEVICE
		DefaultPnpHandler,		// IRP_MN_QUERY_STOP_DEVICE
		DefaultPnpHandler,		// IRP_MN_CANCEL_STOP_DEVICE
		DefaultPnpHandler,		// IRP_MN_QUERY_DEVICE_RELATIONS
		DefaultPnpHandler,		// IRP_MN_QUERY_INTERFACE
		DefaultPnpHandler,		// IRP_MN_QUERY_CAPABILITIES
		DefaultPnpHandler,		// IRP_MN_QUERY_RESOURCES
		DefaultPnpHandler,		// IRP_MN_QUERY_RESOURCE_REQUIREMENTS
		DefaultPnpHandler,		// IRP_MN_QUERY_DEVICE_TEXT
		DefaultPnpHandler,		// IRP_MN_FILTER_RESOURCE_REQUIREMENTS
		DefaultPnpHandler,		// 
		DefaultPnpHandler,		// IRP_MN_READ_CONFIG
		DefaultPnpHandler,		// IRP_MN_WRITE_CONFIG
		DefaultPnpHandler,		// IRP_MN_EJECT
		DefaultPnpHandler,		// IRP_MN_SET_LOCK
		DefaultPnpHandler,		// IRP_MN_QUERY_ID
		DefaultPnpHandler,		// IRP_MN_QUERY_PNP_DEVICE_STATE
		DefaultPnpHandler,		// IRP_MN_QUERY_BUS_INFORMATION
		DefaultPnpHandler,		// IRP_MN_DEVICE_USAGE_NOTIFICATION
		DefaultPnpHandler,		// IRP_MN_SURPRISE_REMOVAL
	};

	ULONG fcn = stack->MinorFunction;
	if (fcn >= arraysize(fcntab))
	{						// unknown function
		status = DefaultPnpHandler(pdx, Irp); // some function we don't know about
		return status;
	}						// unknown function

#if DBG
	static char* fcnname[] = 
	{
		"IRP_MN_START_DEVICE",
		"IRP_MN_QUERY_REMOVE_DEVICE",
		"IRP_MN_REMOVE_DEVICE",
		"IRP_MN_CANCEL_REMOVE_DEVICE",
		"IRP_MN_STOP_DEVICE",
		"IRP_MN_QUERY_STOP_DEVICE",
		"IRP_MN_CANCEL_STOP_DEVICE",
		"IRP_MN_QUERY_DEVICE_RELATIONS",
		"IRP_MN_QUERY_INTERFACE",
		"IRP_MN_QUERY_CAPABILITIES",
		"IRP_MN_QUERY_RESOURCES",
		"IRP_MN_QUERY_RESOURCE_REQUIREMENTS",
		"IRP_MN_QUERY_DEVICE_TEXT",
		"IRP_MN_FILTER_RESOURCE_REQUIREMENTS",
		"",
		"IRP_MN_READ_CONFIG",
		"IRP_MN_WRITE_CONFIG",
		"IRP_MN_EJECT",
		"IRP_MN_SET_LOCK",
		"IRP_MN_QUERY_ID",
		"IRP_MN_QUERY_PNP_DEVICE_STATE",
		"IRP_MN_QUERY_BUS_INFORMATION",
		"IRP_MN_DEVICE_USAGE_NOTIFICATION",
		"IRP_MN_SURPRISE_REMOVAL",
	};

	KdPrint(("PNP Request (%s)\n", fcnname[fcn]));
#endif // DBG

	status = (*fcntab[fcn])(pdx, Irp);
	KdPrint(("Leave HelloWDMPnp\n"));
	return status;
}