carma::util::IPQbuffer Class Reference

Shared memory storage mechanism for an IPQ buffer. More...

#include <carma/util/IPQbuffer.h>

Inheritance diagram for carma::util::IPQbuffer:

Public Member Functions
virtual	~IPQbuffer ()
	Destructor. More...
Public Member Functions inherited from carma::util::IPQbufferBase
int	getElementSize () const
	Returns the size of each element in the queue in bytes. More...
::std::string	getFileName () const
	Get the filename. More...
unsigned int	getGetOffset () const
	Useful only for debugging. More...
unsigned int	getLostElementCount () const
	Get the number of elements lost on the last read. More...
unsigned int	getMaxOffset () const
	Useful only for debugging. More...
int	getNumAvailable () const
	Gets the number of unread elements available in the queue. More...
unsigned int	getPutOffset () const
	Used internally, but made public for debugging. More...
int	getQueueSize () const
	Returns the allocated size of the queue. More...
bool	isDataAvailable () const
	Checks to see if there are any unread elements (would a read not block?). More...
bool	isEmpty () const
	Checks to see if the queue is empty. More...
unsigned int	read ()
	Read the oldest unread element from the queue. More...
bool	readNewest ()
	Get the newest element from the queue (with locking). More...
bool	readNewestConditionalCopy ()
	Reads and copies the newest element from the queue into the localElement buffer, but only if has not been previously read. More...
void	setNoneAvailable ()
	Sets the number of available (unread) elements to zero (catches up) More...
virtual	~IPQbufferBase ()
	Destructor Making this d'tor virtual causes the d'tors of inheriting classes to be called first when the d'tor is called on this base class (polymorphic), followed by the base class d'tor. More...
Public Member Functions inherited from carma::util::IPQinterface
virtual int	getElementSize () const =0
	Returns the size of each element in the queue in bytes. More...
virtual ::std::string	getFileName () const =0
	Get the filename. More...
virtual unsigned int	getGetOffset () const =0
	Useful only for debugging. More...
virtual unsigned int	getLostElementCount () const =0
	Get the number of elements lost on the last read. More...
virtual unsigned int	getMaxOffset () const =0
	Useful only for debugging. More...
virtual int	getNumAvailable () const =0
	Gets the number of unread elements available in the queue. More...
virtual unsigned int	getPutOffset () const =0
virtual int	getQueueSize () const =0
	Returns the allocated size of the queue. More...
virtual bool	isDataAvailable () const =0
	Checks to see if there are any unread elements (would a read not block?). More...
virtual bool	isEmpty () const =0
	Checks to see if the queue is empty. More...
virtual unsigned int	read ()=0
	Read the oldest unread element from the queue. More...
virtual bool	readNewest ()=0
	Get the newest element from the queue (with locking). More...
virtual bool	readNewestConditionalCopy ()=0
	Reads and copies the newest element from the queue into the localElement buffer, but only if has not been previously read. More...
virtual void	setNoneAvailable ()=0
	Sets the number of available (unread) elements to zero (catches up) More...
virtual	~IPQinterface ()=0
	Destructor Making this d'tor virtual causes the d'tors of inheriting classes to be called first when the d'tor is called on this base class (polymorphic), followed by the base class d'tor. More...

Protected Member Functions
	IPQbuffer (void *localElement, int elementSize, const ::std::string &filename, bool isCreator=false, int nElements=0, unsigned int testOffset=0)
	Constructor. More...
Protected Member Functions inherited from carma::util::IPQbufferBase
::std::string	getTrimmedFilename ()
	Get the trimmed filename. More...
void	init ()
	This does all the real constructor work. More...
	IPQbufferBase (void *localElement, int elementSize, const ::std::string &filename, bool isCreator=false, int nElements=0, unsigned int testOffset=0)
	Constructor for a read/write queue. More...
void	trimShmemFilename ()
	Shared memory filenames must contain only one '/' and it must be the first character; this routine fixes up the filename. More...
void	write ()
	Put an element into the queue. More...
Protected Member Functions inherited from carma::util::IPQinterface
virtual void	write ()=0
	Useful only for debugging. More...

Additional Inherited Members
Protected Attributes inherited from carma::util::IPQbufferBase
bool	debug_
int	fileDescriptor_
const int	openMask_
const int	protectionMask_

Detailed Description

Shared memory storage mechanism for an IPQ buffer.

Once the shared memory is formed it persists as a file in /dev/shm. It can be manually deleted if so desired (say, if it corrupted). On Linux 2.4 kernels it can have a maximum size of one half of physical memory.

This class is a base class for reader and writer classes. See for e.g.

See Also

IPQreader, IPQwriter

Definition at line 37 of file IPQbuffer.h.

Constructor & Destructor Documentation

carma::util::IPQbuffer::IPQbuffer ( void *  localElement, int  elementSize, const ::std::string &  filename, bool  isCreator = false, int  nElements = 0, unsigned int  testOffset = 0  )

protected

Constructor.

Parameters

localElement	address of the data buffer for reads/writes
elementSize	of an individual queue element in bytes
filename	Shared memory filename. Must start with '/' and be less than 15 chars long.
isCreator	If true, create a new file if one doesn't exist, and make its size match nElements
nElements	Number of elements to allocate (queue length); ignored if not a creator.
testOffset	When shared memory is created, set the putoffset to have testOffset full queues before it wraps around. Obviously for testing wrap around; zero (default) inhibits this feature.

Exceptions

std::exception

virtual carma::util::IPQbuffer::~IPQbuffer ( )

virtual

Destructor.

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The documentation for this class was generated from the following file:

• carma/util/IPQbuffer.h