BiometricEvaluation::Process::Semaphore Class Reference

Represent a semaphore that can be used for interprocess communication. More...

#include <be_process_semaphore.h>

Public Member Functions
	Semaphore (const std::string &name, const mode_t mode, const int value, const bool force=false)
	Create a new named sempahore. More...
	Semaphore (const std::string &name)
	Open an existing named sempahore. More...
	~Semaphore ()
bool	wait (const bool interruptible)
	Wait indefinitely for the semaphore to unblock. More...
bool	trywait (const bool interruptible)
	Attempt to obtain the semaphore without blocking. More...
bool	timedwait (const uint64_t interval, const bool interruptible)
	Attempt to obtain the semaphore while blocking for at most the specified time interval. More...
void	post ()
	Post (increment) to the semaphore. More...
std::string	getName ()
	Obtain the name of the Semaphore. More...

Detailed Description

Represent a semaphore that can be used for interprocess communication.

Semaphores are shared counters with mutually exclusive modification properties. A counter value greater than zero means that a resource represented by the semaphore is available. A typical use is to grant exclusive access to a resource by allowing the counter to be valued at zero or one; this is known as a binary semaphore.

Note

The counter value is not exposed to clients of the object.

Because a Semaphore object wraps a system resource, the Semaphore can be passed to other functions, or inherited across a fork boundary.

Definition at line 42 of file be_process_semaphore.h.

Constructor & Destructor Documentation

Semaphore() [1/2]

BiometricEvaluation::Process::Semaphore::Semaphore	(	const std::string &	name,
		const mode_t	mode,
		const int	value,
		const bool	force = false
	)

Create a new named sempahore.

Parameters

[in]	name	The name of the semaphore, which must obey the syntax documented for the sem_open(2) call. If the semaphore already exists in the name space, construction will fail unless the force flag is true. In that case, the existing semaphore will be removed.
[in]	mode	The permission mode of the semaphore.
[in]	value	The initial value of the semaphore.
[in]	force	The semaphore is created, disassociating an existing semaphore of the same name.

Exceptions

Error::ObjectExists	The semaphore already exists with the given name.
Error::StrategyError	An error occurred when creating the semaphore.

Semaphore() [2/2]

BiometricEvaluation::Process::Semaphore::Semaphore

(

const std::string &

name

)

Open an existing named sempahore.

Parameters

[in]

name

The name of the semaphore, which must obey the syntax documented for the sem_open(2) call.

Exceptions

Error::ObjectDoesNotExist	A semaphore does not exist with the given name.
Error::StrategyError	An error occurred when creating the semaphore.

~Semaphore()

BiometricEvaluation::Process::Semaphore::~Semaphore

(

)

Member Function Documentation

wait()

bool BiometricEvaluation::Process::Semaphore::wait

(

const bool

interruptible

)

Wait indefinitely for the semaphore to unblock.

Parameters

[in]

interruptible

true if the function should return if waiting was interrupted, false otherwise.

Returns

true if the semaphore was obtained; false if not.

Exceptions

Error::ObjectDoesNotExist	The semaphore is no longer valid.
Error::StrategyError	System error obtaining the semaphore.

trywait()

bool BiometricEvaluation::Process::Semaphore::trywait

(

const bool

interruptible

)

Attempt to obtain the semaphore without blocking.

Parameters

[in]

interruptible

true if the function should return if waiting was interrupted, false otherwise.

Returns

true if the semaphore was obtained; false if not.

Exceptions

Error::ObjectDoesNotExist	The semaphore is no longer valid.
Error::StrategyError	System error obtaining the semaphore.

timedwait()

bool BiometricEvaluation::Process::Semaphore::timedwait	(	const uint64_t	interval,
		const bool	interruptible
	)

Attempt to obtain the semaphore while blocking for at most the specified time interval.

Parameters

[in]	interval	The max time to wait, in microseconds.
[in]	interruptible	true if the function should return if waiting was interrupted, false otherwise.

Returns

true if the semaphore was obtained; false if not.

Exceptions

Error::ObjectDoesNotExist	The semaphore is no longer valid.
Error::NotImplemented	Function is not implemented on the system. Applications should then call wait() or trywait().
Error::StrategyError	System error obtaining the semaphore.

post()

void BiometricEvaluation::Process::Semaphore::post

(

)

Post (increment) to the semaphore.

Exceptions

Error::ObjectDoesNotExist	The semaphore is no longer valid.
Error::StrategyError	System error obtaining the semaphore.

getName()

std::string BiometricEvaluation::Process::Semaphore::getName

(

)

Obtain the name of the Semaphore.

Returns

The name of the Sempahore.

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

• be_process_semaphore.h