#include <SharedMemory.h>

Collaboration diagram for SharedMemorySemaphore:

Public Member Functions
void	init (unsigned int value)

void	increment ()

void	decrement ()

bool	tryDecrement ()

bool	decrementTimeout (u64 seconds, u64 nanoseconds)

void	destroy ()

Private Attributes
sem_t	_sem

bool	_init = false

Detailed Description

A POSIX semaphore for shared memory. See https://linux.die.net/man/7/sem_overview for more deatils

Definition at line 27 of file SharedMemory.h.

Member Function Documentation

void SharedMemorySemaphore::decrement ( )

inline

If the semaphore's value is > 0, decrement the value. Otherwise, wait until its value is > 0, then decrement.

Definition at line 59 of file SharedMemory.h.

References _sem.

59 { sem_wait(&_sem); }

SharedMemorySemaphore::_sem

sem_t _sem

Definition: SharedMemory.h:89

Here is the caller graph for this function:

bool SharedMemorySemaphore::decrementTimeout	(	u64	seconds,
		u64	nanoseconds
	)

inline

Like decrement, but after waiting ms milliseconds, will give up Returns true if the semaphore is successfully decremented

Definition at line 72 of file SharedMemory.h.

References _sem.

                                                       {
     struct timespec ts;
     clock_gettime(CLOCK_REALTIME, &ts);
     ts.tv_nsec += nanoseconds;
     ts.tv_sec += seconds;
     ts.tv_sec += ts.tv_nsec / 1000000000;
     ts.tv_nsec %= 1000000000;
     return (sem_timedwait(&_sem, &ts) == 0);
   }

void SharedMemorySemaphore::destroy ( )

inline

Delete the semaphore. Note that deleting a semaphore in one process while another is still using it results in very strange behavior.

Definition at line 86 of file SharedMemory.h.

References _sem.

86 { sem_destroy(&_sem); }

SharedMemorySemaphore::_sem

sem_t _sem

Definition: SharedMemory.h:89

void SharedMemorySemaphore::increment ( )

inline

Increment the value of the semaphore.

Definition at line 53 of file SharedMemory.h.

References _sem.

53 { sem_post(&_sem); }

SharedMemorySemaphore::_sem

sem_t _sem

Definition: SharedMemory.h:89

void SharedMemorySemaphore::init ( unsigned int value )

inline

If semaphore is unitialized, initialize it and set its value. This can be called as many times as you want safely. It must be called at least once. Only one process needs to call this, even if it is used in multiple processes.

Note that if init() is called after the semaphore has been initialized, it will not change its value.

Parameters

value The initial value of the semaphore.

Definition at line 39 of file SharedMemory.h.

References _init, and _sem.

                                 {
     if (!_init) {
       if (sem_init(&_sem, 1, value)) {
         printf("[ERROR] Failed to initialize shared memory semaphore: %s\n",
                strerror(errno));
       } else {
         _init = true;
       }
     }
   }