RTT::os::Semaphore Class Reference

An object oriented wrapper around a counting semaphore. More...

#include <rtt/os/Semaphore.hpp>

List of all members.

Public Member Functions
	Semaphore (int count)
	Initialize a Semaphore with an initial count.
	~Semaphore ()
	Destroy a Semaphore.
void	wait ()
	Lower this semaphore and return if value() is non zero.
void	signal ()
	Raise this semaphore and signal one thread waiting on this semaphore.
bool	trywait ()
	Try to wait on this semaphore.
bool	waitUntil (Seconds abs_time)
	Wait on this semaphore until a maximum absolute time.
bool	waitUntil (nsecs abs_time)
	Wait on this semaphore until a maximum absolute time.
int	value ()
	Return the current count of this semaphore.

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Detailed Description

An object oriented wrapper around a counting semaphore.

It works like a traffic light on which a thread can wait() until the sempahore's value becomes positive, otherwise it blocks. Another thread then needs to signal() the semaphore. One thread which is waiting will then be awakened, if none is waiting, the first thread calling wait() will continue directly (and decrease the value by 1).

Warning:

Semaphore instances should only be created in soft realtime, since the initialisation of a semaphore can not be done in hard realtime.

Definition at line 61 of file Semaphore.hpp.

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Constructor & Destructor Documentation

RTT::os::Semaphore::Semaphore

(

int

count

)

[inline]

Initialize a Semaphore with an initial count.

See also:

value() to retrieve the current count.

Definition at line 70 of file Semaphore.hpp.

References rtos_sem_init().

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Member Function Documentation

bool RTT::os::Semaphore::trywait

(

)

[inline]

Try to wait on this semaphore.

Returns:

true when the locking succeeded ( this->value() was > 0), false otherwise ( this->value() was = 0 )

Definition at line 106 of file Semaphore.hpp.

void RTT::os::Semaphore::wait

(

)

[inline]

Lower this semaphore and return if value() is non zero.

Or wait if value() is zero until a signal occurs.

Definition at line 87 of file Semaphore.hpp.

bool RTT::os::Semaphore::waitUntil

(

Seconds

abs_time

)

[inline]

Wait on this semaphore until a maximum absolute time.

Parameters:

abs_time

Absolute time in seconds until which to wait on this semaphore.

Return values:

true	if the semaphore was signaled before abs_time expired.
false	if the semaphore was not signaled.

See also:

rtos_get_time_ns() to get the current time in nano seconds.

Definition at line 120 of file Semaphore.hpp.

bool RTT::os::Semaphore::waitUntil

(

nsecs

abs_time

)

[inline]

Wait on this semaphore until a maximum absolute time.

Parameters:

abs_time

Absolute time in nano seconds until which to wait on this semaphore.

Return values:

true	if the semaphore was signaled before abs_time expired.
false	if the semaphore was not signaled.

See also:

rtos_get_time_ns() to get the current time in nano seconds.

Definition at line 134 of file Semaphore.hpp.

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

• rtt/os/Semaphore.hpp