Semaphore Class Reference

Overview

A wrapper class for the EtcPal counting semaphore type.

Usage example:

etcpal::Semaphore sem;
 
void main()
{
  // Install interrupt/signal handler and/or enable interrupts...
 
  while(true)
  {
    if (sem.Wait())
    {
      // Service the interrupt.
      // Because this is a counting semaphore, we will enter this block once for every time the
      // interrupt is received.
    }
  }
}
 
// An interrupt or signal handler installed to handle some event
void InterruptHandler()
{
  // We've received an event. Notify the service thread that a new event has occurred.
  sem.PostFromIsr();
}

See sem (Counting Semaphores) for more information.

Public Member Functions
	Semaphore (unsigned int initial_count=0, unsigned int max_count=kDefaultMaxCount)
	Create a new semaphore.
	~Semaphore ()
	Destroy the semaphore.
	Semaphore (const Semaphore &other)=delete
Semaphore &	operator= (const Semaphore &other)=delete
	Semaphore (Semaphore &&other)=delete
Semaphore &	operator= (Semaphore &&other)=delete
bool	Wait ()
	Wait for the semaphore. More...
bool	TryWait (int timeout_ms=0)
	Wait for the semaphore until either it is received or a timeout expires. More...
bool	Post ()
	Post the semaphore. More...
bool	PostFromIsr ()
	Post the semaphore from an interrupt context. More...
etcpal_sem_t &	get ()
	Get a reference to the underlying etcpal_sem_t type.

Static Public Attributes
static constexpr unsigned int	kDefaultMaxCount = 50
	The default value used for the semaphore's max_count. More...

Member Function Documentation

Post()

bool Post ( )

inline

Post the semaphore.

See etcpal_sem_post().

PostFromIsr()

bool PostFromIsr ( )

inline

Post the semaphore from an interrupt context.

NOTE: Only meaningful on some platforms. See the table in sem (Counting Semaphores) and etcpal_sem_post_from_isr() for more information. On platforms on which it is not meaningful, executes the equivalent of Post().

TryWait()

bool TryWait ( int  timeout_ms = 0 )

inline

Wait for the semaphore until either it is received or a timeout expires.

NOTE: Timeouts other than 0 or ETCPAL_WAIT_FOREVER are typically only honored on real-time platforms. See the table in sem (Counting Semaphores) for more information. On platforms where timeouts are not honored, passing 0 for timeout_ms returns immediately whether the semaphore was available and taken, while any other value executes the equivalent of Wait().

Parameters

timeout_ms

How long to wait for the semaphore, in milliseconds.

Returns

The result of etcpal_sem_timed_wait() on the underlying semaphore.

Wait()

bool Wait ( )

inline

Wait for the semaphore.

Returns

The result of etcpal_sem_wait() on the underlying semaphore.

Field Documentation

kDefaultMaxCount

constexpr unsigned int kDefaultMaxCount = 50

staticconstexpr

The default value used for the semaphore's max_count.

This is not honored on all platforms - see sem (Counting Semaphores) for more information.

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

• include/etcpal/cpp/sem.h