BSsync
Class Semaphore

java.lang.Object
  BSsync.Semaphore

public class Semaphore
extends java.lang.Object

Base class for counting semaphores. Conceptually, a semaphore maintains a set of permits. Each acquire() blocks if necessary until a permit is available, and then takes it. Each release adds a permit. However, no actual permit objects are used; the Semaphore just keeps a count of the number available and acts accordingly.

A semaphore initialized to 1 can serve as a mutual exclusion lock.

This implementation makes NO guarantees about the order in which threads will acquire permits

Field Summary

protected int	permits_ current number of available permits
static boolean	verbose Set this variable to true for debugging output

Constructor Summary

Semaphore(int initialPermits)
Create a Semaphore with the given initial number of permits.

Semaphore(int initialPermits, java.lang.String name)
Create a named Semaphore with the given initial number of permits.

Method Summary

void	acquire() Wait until a permit is available, and take one
void	release() Release a permit

Methods inherited from class java.lang.Object

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

Field Detail

verbose

public static boolean verbose

Set this variable to true for debugging output

permits_

protected int permits_

current number of available permits

Constructor Detail

Semaphore

public Semaphore(int initialPermits)

Create a Semaphore with the given initial number of permits. Using a seed of one makes the semaphore act as a mutual exclusion lock. Negative seeds are also allowed, in which case no acquires will proceed until the number of releases has pushed the number of permits past 0.

Parameters:

initialPermits - initial value of the Semaphore

Semaphore

public Semaphore(int initialPermits,
                 java.lang.String name)

Create a named Semaphore with the given initial number of permits. the name is only used for debugging output. Using a seed of one makes the semaphore act as a mutual exclusion lock. Negative seeds are also allowed, in which case no acquires will proceed until the number of releases has pushed the number of permits past 0.

Parameters:

initialPermits - initial value of the Semaphore

name - name of the Semaphore

Method Detail

acquire

public void acquire()

Wait until a permit is available, and take one

release

public void release()

Release a permit