Burger::Semaphore Class Reference

Class for creating a semaphore. More...

Public Member Functions
	Semaphore (uint32_t uCount=0) noexcept
	Initialize a semaphore.
	~Semaphore ()
	Shut down a semaphore.
eError	signal (void) noexcept
	Signal a semaphore.
eError	wait_for_signal (uint32_t uMilliseconds=0) noexcept
	Wait for a resource with a timeout.
uint32_t	get_value (void) const noexcept
	Get the current number of available resources.

Protected Attributes
volatile uint32_t	m_uCount
	Semaphore count value.

Private Member Functions
	Semaphore (const Semaphore &)=delete
Semaphore &	operator= (const Semaphore &)=delete
	Semaphore (Semaphore &&)=delete
Semaphore &	operator= (Semaphore &&)=delete

Detailed Description

Class for creating a semaphore.

---

In a multiprocessor system, it's necessary to have multiple resources available to multiple threads at the same time. To prevent resource starvation, this class is decremented until the number of available resources is exhausted and then it will halt future threads from executing until resources are made available via calls to signal().

Further reading http://en.wikipedia.org/wiki/Semaphore_(programming)

Note

On operating systems that don't have native semaphore support, such as MSDOS, this class will always return error codes for all calls.

See also

Mutex and Thread

Constructor & Destructor Documentation

Semaphore() [1/3]

Burger::Semaphore::Semaphore ( const Semaphore & )

privatedelete

Semaphore() [2/3]

Burger::Semaphore::Semaphore ( Semaphore && )

privatedelete

Semaphore() [3/3]

Burger::Semaphore::Semaphore ( uint32_t uCount = 0 )

noexcept

Initialize a semaphore.

---

Query the operating system for a semaphore and initialize it to the initial value.

Parameters

uCount

Initial number of resources available (0 means a empty semaphore)

See also

~Semaphore()

~Semaphore()

Burger::Semaphore::~Semaphore

(

)

Shut down a semaphore.

---

Release any operating system resources allocated in the creation of the semaphore.

Note

Care should be exercised in ensuring that all threads are are waiting on semaphores have been shutdown down already.

See also

Semaphore(uint32_t)

Member Function Documentation

get_value()

uint32_t Burger::Semaphore::get_value ( void ) const

inlinenoexcept

Get the current number of available resources.

---

Returns

The number of available resources.

See also

Semaphore(uint32_t)

operator=() [1/2]

Semaphore & Burger::Semaphore::operator= ( const Semaphore & )

privatedelete

operator=() [2/2]

Semaphore & Burger::Semaphore::operator= ( Semaphore && )

privatedelete

signal()

Burger::eError BURGER_API Burger::Semaphore::signal ( void )

noexcept

Signal a semaphore.

---

When a resource is made available, signal that one is available with this call. This function will increment the count, and may release a waiting thread.

Returns

Zero on success, nonzero in the case of a semaphore failure

See also

wait_for_signal(uint32_t)

wait_for_signal()

Burger::eError BURGER_API Burger::Semaphore::wait_for_signal ( uint32_t uMilliseconds = 0 )

noexcept

Wait for a resource with a timeout.

---

If the semaphore's resource count has not gone to zero or less, decrement the count and immediately return. Otherwise, block until another thread posts to the semaphore or the time in milliseconds has elapsed. If the timeout is zero, do not block.

Parameters

uMilliseconds

Number of milliseconds to wait for the resource, 0 means no wait, UINT32_MAX means never time out

Returns

Zero on success, kErrorTimeout on a timeout, or other error code in case of a semaphore failure

See also

signal(void)

Member Data Documentation

m_uCount

volatile uint32_t Burger::Semaphore::m_uCount

protected

Semaphore count value.