net.sourceforge.jtds.jdbc

Class Semaphore

java.lang.Object

net.sourceforge.jtds.jdbc.Semaphore

public class Semaphore
extends java.lang.Object

Simple semaphore class used to serialize access requests over the network connection.

Based on the code originally written by Doug Lea. Once JDK 1.5 is the standard this class can be replaced by the java.util.concurrent.Sempahore class.

Version:

$Id: Semaphore.java,v 1.1 2004-12-20 15:51:17 alin_sinpalean Exp $

Author:

Mike Hutchinson

Field Summary

Fields

Modifier and Type	Field and Description
protected long	permits Current number of available permits.

Constructor Summary

Constructors

Constructor and Description
Semaphore(long initialPermits) Create a Semaphore with the given initial number of permits.

Method Summary

Methods

Modifier and Type	Method and Description
void	acquire() Wait until a permit is available, and take one.
boolean	attempt(long msecs) Wait at most msecs millisconds for a permit.
long	permits() Return the current number of available permits.
void	release() Release a permit.
void	release(long n) Release N permits.

Methods inherited from class java.lang.Object

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

Field Detail

permits

protected long permits

Current number of available permits.

Constructor Detail

Semaphore

public Semaphore(long 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.

Method Detail

acquire

public void acquire()
             throws java.lang.InterruptedException

Wait until a permit is available, and take one.

Throws:

java.lang.InterruptedException

attempt

public boolean attempt(long msecs)
                throws java.lang.InterruptedException

Wait at most msecs millisconds for a permit.

Throws:

java.lang.InterruptedException

release

public void release()

Release a permit.

release

public void release(long n)

Release N permits. release(n) is equivalent in effect to:

   for (int i = 0; i < n; ++i) release();
 

But may be more efficient in some semaphore implementations.

Throws:

java.lang.IllegalArgumentException - if n is negative

permits

public long permits()

Return the current number of available permits. Returns an accurate, but possibly unstable value, that may change immediately after returning.