jade.util
Class RWLock

java.lang.Object
  jade.util.RWLock

Direct Known Subclasses:

SynchList

public class RWLock
extends java.lang.Object

This class provides support for synchronizing threads acting on a generic resource in such a way that - If a thread is writing the resource no other thread can act on it in any way - Several threads can read the resource at the same time - If one or more threads are reading the resource no thread can write it

Author:

Giovanni Caire - TILab

Constructor Summary

RWLock()
Default constructor.

Method Summary

protected void	onWriteEnd() This placeholder method is called every time a thread actually releases the protected resource with writing privileges (this means that, in case of multiple recursive unlocking by the same thread, this method is called only the last time).
protected void	onWriteStart() This placeholder method is called every time a thread actually acquires the protected resource with writing privileges (this means that, in case of multiple recursive locking by the same thread, this method is called only the first time).
void	readLock() Acquire the protected resource with reading privileges.
void	readUnlock() Release the protected resource, previously acquired with reading privileges.
void	writeLock() Acquire the protected resource with writing privileges.
void	writeUnlock() Release the protected resource, previously acquired with writing privileges.

Methods inherited from class java.lang.Object

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

Constructor Detail

RWLock

public RWLock()

Default constructor.

Method Detail

writeLock

public void writeLock()

Acquire the protected resource with writing privileges. Only one writer at a time can access the protected resource, and no readers can access it at the same time. The locking is recursive (i.e. the same thread can acquire the lock multiple times, but must unlock it a matching number of times to actually free the protected resource).

writeUnlock

public void writeUnlock()

Release the protected resource, previously acquired with writing privileges.

readLock

public void readLock()

Acquire the protected resource with reading privileges. Many readers can access the protected resource at the same time, but no writer can access it while at least one reader is present. The locking is recursive (i.e. the same thread can acquire the lock multiple times, but must unlock it a matching number of times to actually free the protected resource).

readUnlock

public void readUnlock()

Release the protected resource, previously acquired with reading privileges.

onWriteStart

protected void onWriteStart()

This placeholder method is called every time a thread actually acquires the protected resource with writing privileges (this means that, in case of multiple recursive locking by the same thread, this method is called only the first time). Subclasses can exploit this to transparently trigger a resource acquisition prolog.

onWriteEnd

protected void onWriteEnd()

This placeholder method is called every time a thread actually releases the protected resource with writing privileges (this means that, in case of multiple recursive unlocking by the same thread, this method is called only the last time). Subclasses can exploit this to transparently trigger a resource release epilog.