An interface to an IO device. More...

#include <IODevice.h>

Inheritance diagram for nidas::core::IODevice:

[legend]

Public Member Functions
	IODevice ()

virtual	~IODevice ()

virtual void	setName (const std::string &val)
	Set the device name to be opened for this sensor.

virtual const std::string &	getName () const

virtual void	open (int flags)=0
	Open the device.

virtual int	getReadFd () const =0
	The file descriptor used when reading from this sensor.

virtual int	getWriteFd () const =0
	The file descriptor used when writing to this sensor.

virtual size_t	read (void *buf, size_t len)=0
	Read from the sensor.

virtual size_t	read (void *buf, size_t len, int msecTimeout)=0
	Read from the sensor with a millisecond timeout.

virtual size_t	getBytesAvailable () const
	Return how many bytes are available to read on this IODevice.

virtual size_t	write (const void *buf, size_t len)=0
	Write to the sensor.

virtual void	ioctl (int request, void *buf, size_t len)=0

virtual void	close ()=0
	Close the device.

Private Member Functions
	IODevice (const IODevice &)
	Derived classes don't implement copy so we won't here.

IODevice &	operator= (const IODevice &)
	Derived classes don't implement assignment so we won't here.

Private Attributes
std::string	_devname
	Whether to reopen this sensor on an IOException.

Detailed Description

An interface to an IO device.

The main user of this interface is DSMSensor, which contains an IODevice, using it to do I/O with the underlying device.

Constructor & Destructor Documentation

◆ IODevice() [1/2]

nidas::core::IODevice::IODevice ( )

inline

◆ ~IODevice()

virtual nidas::core::IODevice::~IODevice ( )

inlinevirtual

◆ IODevice() [2/2]

nidas::core::IODevice::IODevice ( const IODevice & )

private

Derived classes don't implement copy so we won't here.

Member Function Documentation

◆ close()

virtual void nidas::core::IODevice::close ( )

pure virtual

Close the device.

Exceptions

nidas::util::IOException

Implemented in nidas::core::ServerSocketIODevice, nidas::core::TCPSocketIODevice, nidas::core::UDPSocketIODevice, and nidas::core::UnixIODevice.

Referenced by nidas::core::DSMSensor::close().

◆ getBytesAvailable()

virtual size_t nidas::core::IODevice::getBytesAvailable ( ) const

inlinevirtual

Return how many bytes are available to read on this IODevice.

This method is only useful when ioctl FIONREAD is supported on this this IODevice, as for example with a UDP socket. It is not available, and not necessary, on most other devices, like serial ports, TCP sockets, or devices with nidas driver module support, in which case it will return an nidas::util::IOException. It is an optimization for use with UDP sockets, where after select determines that data is available on the socket file descriptor, a read will only read one datagram, even if there are more than one packet available, which would not be optimal if a sensor generated many small packets. Rather than returning back to select, we check if there are more datagrams to read. This is not necessary on other types of IODevices, where it is just a matter of using a big enough buffer to get all (or most) available data after a select.

According to man udp(7), FIONREAD will return 0 if the size of the next packet is 0. So, if select/poll indicate there is data available, one read at least should be done, just in case a sensor sends a datagram of length 0, otherwise it will never be consumed.

Exceptions

nidas::util::IOException

References err, getName(), getReadFd(), and ioctl().

Referenced by nidas::core::DSMSensor::getBytesAvailable().