Semaphore Class Reference

A classic semaphore synchronization primitive. More...

List of all members.

Public Member Functions
	Semaphore (int initial_count)
	Semaphore ()
	acquire ()
	Decrements the internal count.
int	getCount ()
	Returns the current semaphore count.
	output (ostream out)
int	release ()
	Increments the semaphore's internal count.
bool	tryAcquire ()
	If the semaphore can be acquired without blocking, does so and returns true.

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Detailed Description

A classic semaphore synchronization primitive.

A semaphore manages an internal counter which is decremented by each acquire() call and incremented by each release() call. The counter can never go below zero; when acquire() finds that it is zero, it blocks, waiting until some other thread calls release().

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Constructor & Destructor Documentation

Semaphore

(

int

initial_count

)

Semaphore

(

)

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Member Function Documentation

acquire

(

)

Decrements the internal count.

If the count was already at zero, blocks until the count is nonzero, then decrements it.

int getCount

(

)

Returns the current semaphore count.

Note that this call is not thread-safe (the count may change at any time).

output

(

ostream

out

)

int release

(

)

Increments the semaphore's internal count.

This may wake up another thread blocked on acquire().

Returns the count of the semaphore upon release.

bool tryAcquire

(

)

If the semaphore can be acquired without blocking, does so and returns true.

Otherwise, returns false.