A basic Unix I/O device, such as a named pipe, or a watched file. More...

#include <UnixIODevice.h>

Inheritance diagram for nidas::core::UnixIODevice:

[legend]

Public Member Functions
	UnixIODevice ()
	Constructor.

	UnixIODevice (const std::string &name)
	Constructor, passing the name of the device.

	~UnixIODevice ()
	Destructor.

int	getReadFd () const
	The file descriptor used when reading from this device.

int	getWriteFd () const
	The file descriptor used when writing to this device.

void	open (int flags)
	open the device.

size_t	read (void *buf, size_t len)
	Read from the device.

size_t	read (void *buf, size_t len, int msecTimeout)
	Read from the device with a timeout in milliseconds.

size_t	write (const void *buf, size_t len)
	Write to the device.

void	ioctl (int request, void *buf, size_t)

void	close ()
	close the device

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

virtual const std::string &	getName () const

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

Protected Attributes
int	_fd

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

Detailed Description

A basic Unix I/O device, such as a named pipe, or a watched file.

Constructor & Destructor Documentation

◆ UnixIODevice() [1/2]

nidas::core::UnixIODevice::UnixIODevice ( )

inline

Constructor.

Does not open any actual device.

◆ UnixIODevice() [2/2]

nidas::core::UnixIODevice::UnixIODevice ( const std::string & name )

inline

Constructor, passing the name of the device.

Does not open the device.

References nidas::core::IODevice::setName().

◆ ~UnixIODevice()

nidas::core::UnixIODevice::~UnixIODevice ( )

inline

Destructor.

Does not close the device.

Member Function Documentation

◆ close()

void nidas::core::UnixIODevice::close ( )

inlinevirtual

close the device

Exceptions

nidas::util::IOException

Implements nidas::core::IODevice.

References _fd, close(), fd, and nidas::core::IODevice::getName().

Referenced by close().

◆ getBytesAvailable()

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

inlinevirtualinherited

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, nidas::core::IODevice::getName(), nidas::core::IODevice::getReadFd(), and nidas::core::IODevice::ioctl().

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