uk.ac.soton.ecs.grimoires.server.store
Class CopyOfReadWriteLock

java.lang.Object
  uk.ac.soton.ecs.grimoires.server.store.CopyOfReadWriteLock

public class CopyOfReadWriteLock

extends Object

A lock that allows multiple read access or single write access to some data at any one time. Reads are prioritised over writes so all reads are processed first. Before performing a read operation on the data in question, the client code should call beforeRead() on the associated lock, then call afterRead () afterwards. Similarly, before performing a write operation on the data, the client code should call beforeWrite() on the associated lock, then call afterWrite () afterwards.

This code is adapted from that in "Concurrent Programming in Java" by Doug Lea, published by Addison Wesley.

Version:

$Id: CopyOfReadWriteLock.java,v 1.1 2005/11/16 13:38:21 wf Exp $ Created: 29 April 2004,16:14 Copyright 2003 Simon Miles, Luc Moreau, Juri Papay

Author:

Simon Miles

Constructor Summary

CopyOfReadWriteLock()
Creates a new instance of ReadWriteLock

Method Summary

void	afterRead() Call after every read operation
void	afterWrite() Call after every write operation
protected boolean	allowReader() Multiple reads are allowed at the same time and reads are prioritised over writes.
protected boolean	allowWriter() A write can only take place when no other reads or writes are taking place
void	beforeRead() Call before every read operation
void	beforeWrite() Call before every write operation

Methods inherited from class java.lang.Object

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

Constructor Detail

CopyOfReadWriteLock

public CopyOfReadWriteLock()

Creates a new instance of ReadWriteLock

Method Detail

afterRead

public void afterRead()

Call after every read operation

afterWrite

public void afterWrite()

Call after every write operation

allowReader

protected boolean allowReader()

Multiple reads are allowed at the same time and reads are prioritised over writes. To change so that read and write are given the same priority, change the line to: return activeWriters == 0 && waitingWriters == 0;

allowWriter

protected boolean allowWriter()

A write can only take place when no other reads or writes are taking place

beforeRead

public void beforeRead()

Call before every read operation

beforeWrite

public void beforeWrite()

Call before every write operation