Arp::System::Commons::Threading::Semaphore Class Reference

Implementation of named or unnamed semaphore used to synchronize processes and threads. More...

#include <Semaphore.hpp>

Public Member Functions
	Semaphore (size_t initialValue)
	Constructs an unnamed Semaphore, i.e. local, instance. More...
	Semaphore (const String &name, size_t initialValue)
	Constructs a named Semaphore instance. More...
	Semaphore (const String &name)
	Opens a named Semaphore instance. More...
virtual	~Semaphore (void)
	Destructs this instance and frees all resources. More...
void	Post (void)
	Increments the internal counter. More...
bool	Wait (size_t timeout=0)
	Tries to decrements the internal counter. More...
bool	TryWait (void)
	Like Wait but returns immediately if the semaphore could not be decremented. More...
size_t	GetValue (void)
	Returns the current value of the internal counter. More...
String	GetName (void)
	Returns the name of a named semaphore. More...

Detailed Description

Implementation of named or unnamed semaphore used to synchronize processes and threads.

Semaphores are mainly integer based counters. Whenever one of the wait-methods are called on an instance, the internal counter is decremeneted by one. If the current value of the counter on an invocation of Wait is zero, than the call blocks until another thread calls Post on the same semaphore instance.

Constructor & Destructor Documentation

Semaphore() [1/3]

Arp::System::Commons::Threading::Semaphore::Semaphore ( size_t  initialValue )

explicit

Constructs an unnamed Semaphore, i.e. local, instance.

Local semaphores can only be used inside the same memory space, i.e. from tasks inside the same process.

Parameters

initialValue

The initial value of the semaphore.

Exceptions

Arp::System::Commons::InvalidOperationException

if the semaphore could not be created.

Semaphore() [2/3]

Arp::System::Commons::Threading::Semaphore::Semaphore	(	const String &	name,
		size_t	initialValue
	)

Constructs a named Semaphore instance.

Named semaphores can be used for synchronization purposes between processes not only between threads of the same process.

Parameters

name	A name identifying the semaphore in the root file s
initialValue	The initial value of the semaphore.

Exceptions

Arp::System::Commons::InvalidOperationException	if the semaphore could not be created.
Arp::System::Commons::Io::AlreadyExistsException	if a semaphore with the same name already exists.

Semaphore() [3/3]

Arp::System::Commons::Threading::Semaphore::Semaphore ( const String &  name )

explicit

Opens a named Semaphore instance.

Tries to open the semaphore identified by name. If no such semaphore exists, an exception is thrown.

Parameters

name	Name of the semaphore to open.

Exceptions

Arp::System::Commons::InvalidOperationException

if the semaphore could not be created.

~Semaphore()

virtual Arp::System::Commons::Threading::Semaphore::~Semaphore ( void  )

virtual

Destructs this instance and frees all resources.

Member Function Documentation

GetName()

String Arp::System::Commons::Threading::Semaphore::GetName

(

void

)

Returns the name of a named semaphore.

Returns

Name if this instance is a named semaphore, otherwise an emptry string is returned.

GetValue()

size_t Arp::System::Commons::Threading::Semaphore::GetValue

(

void

)

Returns the current value of the internal counter.

Returns

Current value of internal counter.

Exceptions

Arp::Exception

with detailed error message in case operation fails.

Post()

void Arp::System::Commons::Threading::Semaphore::Post

(

void

)

Increments the internal counter.

Exceptions

Arp::Exception

with detailed error message in case operation fails.

TryWait()

bool Arp::System::Commons::Threading::Semaphore::TryWait

(

void

)

Like Wait but returns immediately if the semaphore could not be decremented.

Returns

True if semaphore is decremented, otherwise false is returned.

Exceptions

Arp::Exception

with detailed error message in case operation fails.

Wait()

bool Arp::System::Commons::Threading::Semaphore::Wait

(

size_t

timeout = 0

)

Tries to decrements the internal counter.

If the counter is zero at invocation, the call blocks until the counter is incremented by a call to Post.

Returns

True if the semaphore was successfully decremented, otherwise false.

Exceptions

Arp::Exception

with detailed error message in case operation fails.

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

• Arp/System/Commons/Threading/Semaphore.hpp