EventDetect::SharedMemoryTimestampExporter Class Reference

Manages a POSIX shared memory segment for exporting timestamps. Stores an array of two int64_t: {update_time, last_active_time}. Handles creation, mapping, updating, and cleanup via RAII. More...

#include <event_detect.h>

Public Member Functions
	SharedMemoryTimestampExporter (const std::string &name)
	Construct with the desired shared memory name. More...
	~SharedMemoryTimestampExporter ()
	Destructor handles unmapping and potentially unlinking the shared memory.
	SharedMemoryTimestampExporter (const SharedMemoryTimestampExporter &)=delete
SharedMemoryTimestampExporter &	operator= (const SharedMemoryTimestampExporter &)=delete
	SharedMemoryTimestampExporter (SharedMemoryTimestampExporter &&)=delete
SharedMemoryTimestampExporter &	operator= (SharedMemoryTimestampExporter &&)=delete
bool	CreateOrOpen (mode_t mode=0666)
	Creates (if necessary) and opens the shared memory segment, sets its size (to sizeof(int64_t[2])), and maps it for writing. Must be called before UpdateTimestamps or IsInitialized. More...
bool	UpdateTimestamps (int64_t update_time, int64_t last_active_time)
	Updates both timestamps in the mapped shared memory. More...
bool	IsInitialized () const
	Checks if the shared memory was successfully initialized (opened and mapped). More...
bool	UnlinkSegment ()
	Explicitly unlinks the shared memory segment. Call during clean shutdown if desired. Idempotent. More...

Private Member Functions
void	Cleanup ()
	Performs resource cleanup (munmap). Called by destructor.

Private Attributes
std::mutex	mtx_shmem
	This protects against multiple threads in the event_detect process from simultaneously accessing and writing to the shared memory segment. It does NOT protect from another process encountering a torn read. I would prefer to use a pthread_mutex_t in the shmem data structure and manege the mutex across the writer and reader, but the BOINC architect does not believe this is necessary in practice given the small size and low frequency of writing and reading.
std::string	m_shm_name
int	m_shm_fd
int64_t *	m_mapped_ptr
const size_t	m_size
bool	m_is_creator
std::atomic< bool >	m_is_initialized

Detailed Description

Manages a POSIX shared memory segment for exporting timestamps. Stores an array of two int64_t: {update_time, last_active_time}. Handles creation, mapping, updating, and cleanup via RAII.

Constructor & Destructor Documentation

SharedMemoryTimestampExporter()

SharedMemoryTimestampExporter::SharedMemoryTimestampExporter ( const std::string &  name )

explicit

Construct with the desired shared memory name.

Parameters

name	Must start with '/' (e.g., "/idle_detect_shmem").

Member Function Documentation

CreateOrOpen()

bool SharedMemoryTimestampExporter::CreateOrOpen

(

mode_t

mode = 0666

)

Creates (if necessary) and opens the shared memory segment, sets its size (to sizeof(int64_t[2])), and maps it for writing. Must be called before UpdateTimestamps or IsInitialized.

Parameters

mode	Permissions (e.g., 0666 or 0660) to use if creating the segment.

Returns

True on success, false on any failure (shm_open, ftruncate, mmap).

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IsInitialized()

bool SharedMemoryTimestampExporter::IsInitialized

(

)

const

Checks if the shared memory was successfully initialized (opened and mapped).

Returns

True if initialized and ready for updates, false otherwise.

UnlinkSegment()

bool SharedMemoryTimestampExporter::UnlinkSegment

(

)

Explicitly unlinks the shared memory segment. Call during clean shutdown if desired. Idempotent.

Returns

True if unlink succeeded or segment already gone, false on error.

UpdateTimestamps()

bool SharedMemoryTimestampExporter::UpdateTimestamps	(	int64_t	update_time,
		int64_t	last_active_time
	)

Updates both timestamps in the mapped shared memory.

Parameters

update_time	The timestamp of the current update cycle.
last_active_time	The calculated overall last active time.

Returns

True if updated successfully, false if not initialized or pointer is invalid.

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

• event_detect.h
• event_detect.cpp