net.sf.asyncobjects.util
Class Semaphore

java.lang.Object
  net.sf.asyncobjects.AsyncUnicastServer<ASemaphore>
      net.sf.asyncobjects.util.Semaphore

All Implemented Interfaces:

AsyncObject, ExplicitSharing, ASemaphore

public class Semaphore
extends AsyncUnicastServer<ASemaphore>
implements ASemaphore

Asynchronous semaphore service. It works both throw proxy and when used directly in the single thread. This class maintains positive and negative permits separtely. Positive permits is what is avaialbe for the current aquire call. Negative permits is what is scheduled.

Author:

const

Constructor Summary

Semaphore(int permits)
Create semaphore with specified number of permits.

Method Summary

Promise<Void>	acquire()
Promise<Void>	acquire(int number) Aquiree a number of permits
Promise<Integer>	availablePermits() This is amount of permits that are released but have not yet been acquired with a ASemaphore.acquire(int) call.
Promise<Integer>	drainPermits() Drain all available permits.
Promise<Integer>	permitsBalance()
void	release() Release a permit
void	release(int number) Release a number of permits

Methods inherited from class net.sf.asyncobjects.AsyncUnicastServer

dereference, export, isImmediate, myVat, promise

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface net.sf.asyncobjects.AsyncObject

dereference, isImmediate

Constructor Detail

Semaphore

public Semaphore(int permits)

Create semaphore with specified number of permits. It could be negative.

Parameters:

permits - amount of permits.

Method Detail

acquire

public Promise<Void> acquire()

Specified by:

acquire in interface ASemaphore

Returns:

when aquired one permit

See Also:

ASemaphore.acquire()

acquire

public Promise<Void> acquire(int number)

Description copied from interface: ASemaphore

Aquiree a number of permits

Specified by:

acquire in interface ASemaphore

Parameters:

number - amount of permits to aquired

Returns:

when permits are aquired

See Also:

ASemaphore.acquire(int)

availablePermits

public Promise<Integer> availablePermits()

Description copied from interface: ASemaphore

This is amount of permits that are released but have not yet been acquired with a ASemaphore.acquire(int) call. If there are pending ASemaphore.acquire(int) call, this could happen due to several reasons:

• the ASemaphore.acquire(int) call could be not yet awaken.
• the argument of ASemaphore.acquire(int) is greater than amount of available permits.

Specified by:

availablePermits in interface ASemaphore

Returns:

amount of currently available permits.

See Also:

ASemaphore.availablePermits()

permitsBalance

public Promise<Integer> permitsBalance()

Specified by:

permitsBalance in interface ASemaphore

Returns:

return an permits balance. The sum of permits requested by pending ASemaphore.acquire(int) calls is substracted from available permits.

See Also:

ASemaphore.permitsBalance()

drainPermits

public Promise<Integer> drainPermits()

Description copied from interface: ASemaphore

Drain all available permits. Note that this method waits until at least zero permits available. If less than zero permits available, the method blocks.

Specified by:

drainPermits in interface ASemaphore

Returns:

amount of permits that were available.

See Also:

ASemaphore.drainPermits()

release

public void release()

Description copied from interface: ASemaphore

Release a permit

Specified by:

release in interface ASemaphore

See Also:

ASemaphore.release()

release

public void release(int number)

Description copied from interface: ASemaphore

Release a number of permits

Specified by:

release in interface ASemaphore

Parameters:

number - a number of permits

See Also:

ASemaphore.release(int)