Ar::Semaphore Class Reference

#include <ar_classes.h>

Inheritance diagram for Ar::Semaphore:

Description

Counting semaphore class.

See also

Semaphore::Guard

Collaboration diagram for Ar::Semaphore:

Public Member Functions
	Semaphore ()
	Default constructor.
	Semaphore (const char *name, unsigned count=1)
	Constructor.
	~Semaphore ()
	Destructor. More...
ar_status_t	get (uint32_t timeout=kArInfiniteTimeout)
	Acquire the semaphore. More...
unsigned	getCount () const
	Returns the current semaphore count.
const char *	getName () const
	Get the semaphore's name.
ar_status_t	init (const char *name, unsigned count=1)
	Initialiser. More...
ar_status_t	put ()
	Release the semaphore. More...

Constructor & Destructor Documentation

~Semaphore()

Ar::Semaphore::~Semaphore ( )

inline

Destructor.

Any threads on the blocked list will be unblocked immediately. Their return status from the get() method will be kArObjectDeletedError.

Member Function Documentation

get()

ar_status_t Ar::Semaphore::get ( uint32_t  timeout = kArInfiniteTimeout )

inline

Acquire the semaphore.

The semaphore count is decremented. If the count is 0 upon entering this method then the caller thread is blocked until the count reaches 1. Threads are unblocked in the order in which they were blocked. Priority is not taken into consideration, so priority inversions are possible.

Note

This function may be called from interrupt context only if the timeout parameter is set to kArNoTimeout (or 0).

Parameters

timeout

The maximum number of milliseconds that the caller is willing to wait in a blocked state before the semaphore can be obtained. If this value is 0, or kArNoTimeout, then this method will return immediately if the semaphore cannot be obtained. Setting the timeout to kArInfiniteTimeout will cause the thread to wait forever for a chance to get the semaphore.

Return values

kArSuccess	The semaphore was obtained without error.
kArTimeoutError	The specified amount of time has elapsed before the semaphore could be obtained.
kArObjectDeletedError	Another thread deleted the semaphore while the caller was blocked on it.
kArNotFromInterruptError	A non-zero timeout is not alllowed from the interrupt context.

init()

ar_status_t Ar::Semaphore::init ( const char *  name, unsigned  count = 1  )

inline

Initialiser.

Parameters

name	Pass a name for the semaphore. If NULL is passed the name will be set to an empty string.
count	The initial semaphore count. Setting this value to 0 will cause the first call to get() to block until put() is called. A value of 1 or greater will allow that many calls to get() to succeed.

Return values

kArSuccess

Semaphore initialised successfully.

put()

ar_status_t Ar::Semaphore::put ( )

inline

Release the semaphore.

The semaphore count is incremented.

Note

This call is safe from interrupt context.

Return values

kArSuccess

The semaphore was released without error.