RingBuffer Class Reference

Class to manage a Ring Buffer placed in an IPC shared memory. More...

#include <RingBuffer.h>

Collaboration diagram for RingBuffer:

Public Member Functions
	RingBuffer (int nwords=c_DefaultSize)
	Constructor to create a new shared memory in private space. More...
	RingBuffer (const std::string &name, unsigned int nwords=0)
	Constructor to create/attach named shared memory in global space.
	~RingBuffer ()
	Destructor.
void	openSHM (int nwords)
	open shared memory
void	cleanup ()
	Function to detach and remove shared memory.
int	insq (const int *buf, int size, bool checkTx=false)
	Append a buffer to the RingBuffer.
int	remq (int *buf)
	Pick up a buffer from the RingBuffer.
int	spyq (int *buf) const
	Prefetch a buffer from the RingBuffer w/o removing it.
int	numq () const
	Returns number of entries/buffers in the RingBuffer.
void	txAttached ()
	Increase the number of attached Tx counter.
void	txDetached ()
	Decrease the number of attached Tx counter.
void	kill ()
	Cause termination of reading processes (if they use isDead()). More...
bool	isDead () const
	If True, the ring buffer is empty and has no attached Tx modules (i.e. More...
bool	allRxWaiting () const
	True if and only if buffer is empty and nbusy == 0. More...
int	clear ()
	Clear the RingBuffer.
void	forceClear ()
	Forcefully clear the RingBuffer with resetting semaphore.
int	tryClear ()
	Clear the RingBuffer, if the semaphore isn't locked at the moment. More...
int	shmid () const
	Return ID of the shared memory.
void	dump_db ()
	Print some info on the RingBufInfo structure.
int	ninsq () const
	Return number of insq() calls for current buffer.
int	nremq () const
	Return number of remq() calls for current buffer.
int	insq_counter () const
	Return number of insq() calls.
int	remq_counter () const
	Return number of remq() calls.
void	dumpInfo () const
	Dump contents of RingBufInfo metadata.

Static Public Attributes
static const int	c_DefaultSize = 15000000
	Standard size of buffer, in integers (~60MB). More...

Private Attributes
bool	m_new {true}
	True if we created the ring buffer ourselves (and need to clean it).
bool	m_file {false}
	True if m_pathfd needs to be closed.
std::string	m_pathname {""}
	Path for identifying shared memory if named ring buffer is created.
int	m_pathfd { -1}
	Associated file descriptor.
key_t	m_shmkey {IPC_PRIVATE}
	SHM key, see shmget(2).
key_t	m_semkey {IPC_PRIVATE}
	Semaphore key, see semget(2).
std::string	m_semshmFileName {""}
	file path containing ids of shm and sema for private shared mem, used for easier cleanup if we fail to do things properly
bool	m_procIsBusy {false}
	Is this process currently processing events from this RingBuffer? More...
int	m_shmid { -1}
	ID of shared memory segment. More...
int *	m_shmadr {nullptr}
	Address of attached shared memory segment. More...
int	m_shmsize { -1}
	Size of shared memory segment, in bytes.
struct RingBufInfo *	m_bufinfo {nullptr}
	structure to manage ring buffer. More...
int *	m_buftop {nullptr}
	Points to memory after the end of m_bufinfo.
int	m_semid { -1}
	Semaphore ID.
int	m_remq_counter {0}
	count remq() calls.
int	m_insq_counter {0}
	count insq() calls.

Detailed Description

Class to manage a Ring Buffer placed in an IPC shared memory.

Definition at line 39 of file RingBuffer.h.

Constructor & Destructor Documentation

RingBuffer()

RingBuffer ( int  nwords = c_DefaultSize )

explicit

Constructor to create a new shared memory in private space.

Parameters

nwords

Ring buffer size in integers

Definition at line 32 of file RingBuffer.cc.

{
  openSHM(size);
  B2DEBUG(32, "RingBuffer initialization done");
}

Member Function Documentation

allRxWaiting()

bool allRxWaiting

(

)

const

True if and only if buffer is empty and nbusy == 0.

Called in Tx to see if all events of the current run have been processed

Definition at line 400 of file RingBuffer.cc.

isDead()

bool isDead

(

)

const

If True, the ring buffer is empty and has no attached Tx modules (i.e.

no new data is going to be added). Processes should then stop.

Definition at line 394 of file RingBuffer.cc.

kill()

void kill

(

)

Cause termination of reading processes (if they use isDead()).

Assumed to be atomic.

Definition at line 389 of file RingBuffer.cc.

tryClear()

int tryClear

(

)

Clear the RingBuffer, if the semaphore isn't locked at the moment.

See SemaphoreLocker::isLocked() for details

Definition at line 450 of file RingBuffer.cc.

Member Data Documentation

c_DefaultSize

const int c_DefaultSize = 15000000

static

Standard size of buffer, in integers (~60MB).

Needs to be large enough to contain any event, but adds to total memory use of basf2.

Definition at line 42 of file RingBuffer.h.

m_bufinfo

struct RingBufInfo* m_bufinfo {nullptr}

private

structure to manage ring buffer.

Placed on top of the shared memory.

Definition at line 129 of file RingBuffer.h.

m_procIsBusy

bool m_procIsBusy {false}

private

Is this process currently processing events from this RingBuffer?

set during remq() with value depending on wether data was returned. Always false for a process that is only using insq().

Definition at line 124 of file RingBuffer.h.

m_shmadr

int* m_shmadr {nullptr}

private

Address of attached shared memory segment.

(See shmat(2))

Definition at line 127 of file RingBuffer.h.

m_shmid

int m_shmid { -1}

private

ID of shared memory segment.

(See shmget(2))

Definition at line 126 of file RingBuffer.h.

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

• framework/pcore/include/RingBuffer.h
• framework/pcore/src/RingBuffer.cc