Package org.h2.util

Class CacheLRU

java.lang.Object

org.h2.util.CacheLRU

All Implemented Interfaces:

Cache

public class CacheLRU
extends java.lang.Object
implements Cache

A cache implementation based on the last recently used (LRU) algorithm.

Field Summary

Fields

Modifier and Type	Field	Description
private boolean	fifo	Use First-In-First-Out (don't move recently used items to the front of the queue).
private CacheObject	head
private int	len	The number of cache buckets.
private int	mask
private long	maxMemory	The maximum memory, in words (4 bytes each).
private long	memory	The current memory used in this cache, in words (4 bytes each).
private int	recordCount
(package private) static java.lang.String	TYPE_NAME
private CacheObject[]	values
private CacheWriter	writer

Constructor Summary

Constructors

Constructor	Description
CacheLRU(CacheWriter writer, int maxMemoryKb, boolean fifo)

Method Summary

Modifier and Type	Method	Description
private void	addToFront(CacheObject rec)
void	clear()	Clear the cache.
CacheObject	find(int pos)	Get an element from the cache if it is available.
CacheObject	get(int pos)	Get an element in the cache if it is available.
java.util.ArrayList<CacheObject>	getAllChanged()	Get all objects in the cache that have been changed.
static Cache	getCache(CacheWriter writer, java.lang.String cacheType, int cacheSize)	Create a cache of the given type and size.
int	getMaxMemory()	Get the maximum memory to be used.
int	getMemory()	Get the used size in KB.
void	put(CacheObject rec)	Add an element to the cache.
boolean	remove(int pos)	Remove an object from the cache.
private void	removeFromLinkedList(CacheObject rec)
private void	removeOld()
private void	removeOldIfRequired()
void	setMaxMemory(int maxKb)	Set the maximum memory to be used by this cache.
CacheObject	update(int pos, CacheObject rec)	Update an element in the cache.

Methods inherited from class java.lang.Object

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

Field Detail

TYPE_NAME

static final java.lang.String TYPE_NAME

See Also:

Constant Field Values

writer

private final CacheWriter writer

fifo

private final boolean fifo

Use First-In-First-Out (don't move recently used items to the front of the queue).

head

private final CacheObject head

mask

private final int mask

values

private CacheObject[] values

recordCount

private int recordCount

len

private final int len

The number of cache buckets.

maxMemory

private long maxMemory

The maximum memory, in words (4 bytes each).

memory

private long memory

The current memory used in this cache, in words (4 bytes each).

Constructor Detail

CacheLRU

CacheLRU(CacheWriter writer,
         int maxMemoryKb,
         boolean fifo)

Method Detail

getCache

public static Cache getCache(CacheWriter writer,
                             java.lang.String cacheType,
                             int cacheSize)

Create a cache of the given type and size.

Parameters:

writer - the cache writer

cacheType - the cache type

cacheSize - the size

Returns:

the cache object

clear

public void clear()

Description copied from interface: Cache

Clear the cache.

Specified by:

clear in interface Cache

put

public void put(CacheObject rec)

Description copied from interface: Cache

Add an element to the cache. Other items may fall out of the cache because of this. It is not allowed to add the same record twice.

Specified by:

put in interface Cache

Parameters:

rec - the object

update

public CacheObject update(int pos,
                          CacheObject rec)

Description copied from interface: Cache

Update an element in the cache. This will move the item to the front of the list.

Specified by:

update in interface Cache

Parameters:

pos - the unique key of the element

rec - the element

Returns:

the element

removeOldIfRequired

private void removeOldIfRequired()

removeOld

private void removeOld()

addToFront

private void addToFront(CacheObject rec)

removeFromLinkedList

private void removeFromLinkedList(CacheObject rec)

remove

public boolean remove(int pos)

Description copied from interface: Cache

Remove an object from the cache.

Specified by:

remove in interface Cache

Parameters:

pos - the unique key of the element

Returns:

true if the key was in the cache

find

public CacheObject find(int pos)

Description copied from interface: Cache

Get an element from the cache if it is available. This will not move the item to the front of the list.

Specified by:

find in interface Cache

Parameters:

pos - the unique key of the element

Returns:

the element or null

get

public CacheObject get(int pos)

Description copied from interface: Cache

Get an element in the cache if it is available. This will move the item to the front of the list.

Specified by:

get in interface Cache

Parameters:

pos - the unique key of the element

Returns:

the element or null

getAllChanged

public java.util.ArrayList<CacheObject> getAllChanged()

Description copied from interface: Cache

Get all objects in the cache that have been changed.

Specified by:

getAllChanged in interface Cache

Returns:

the list of objects

setMaxMemory

public void setMaxMemory(int maxKb)

Description copied from interface: Cache

Set the maximum memory to be used by this cache.

Specified by:

setMaxMemory in interface Cache

Parameters:

maxKb - the maximum size in KB

getMaxMemory

public int getMaxMemory()

Description copied from interface: Cache

Get the maximum memory to be used.

Specified by:

getMaxMemory in interface Cache

Returns:

the maximum size in KB

getMemory

public int getMemory()

Description copied from interface: Cache

Get the used size in KB.

Specified by:

getMemory in interface Cache

Returns:

the current size in KB