de.lmu.ifi.dbs.elki.persistent
Class PageFile<P extends Page<P>>

java.lang.Object
  de.lmu.ifi.dbs.elki.persistent.PageFile<P>

Type Parameters:

P - Page type

All Implemented Interfaces:

CachedFile<P>

Direct Known Subclasses:

MemoryPageFile, OnDiskArrayPageFile, PersistentPageFile

public abstract class PageFile<P extends Page<P>>
extends Object
implements CachedFile<P>

Abstract class implementing general methods of a PageFile. A PageFile stores objects that implement the Page interface.

Author:

Elke Achtert

Field Summary

protected Cache<P>	cache The cache of this file.
protected Stack<Integer>	emptyPages A stack holding the empty page ids.
protected int	nextPageID The last page ID.
protected int	pageSize The size of a page in Bytes.
protected long	readAccess The read I/O-Access of this file.
protected long	writeAccess The write I/O-Access of this file.

Constructor Summary

protected

PageFile() Creates a new PageFile.

Method Summary

void	clear() Clears this PageFile.
void	close() Closes this file.
void	deletePage(int pageID) Deletes the node with the specified id from this file.
long	getLogicalPageAccess() Returns the logical read I/O-Accesses of this file.
private Integer	getNextEmptyPageID() Returns the next empty page id.
int	getNextPageID() Returns the next page id.
long	getPhysicalReadAccess() Returns the physical read I/O-Accesses of this file.
long	getPhysicalWriteAccess() Returns the physical write I/O-Accesses of this file.
protected void	initCache(int pageSize, int cacheSize, Cache<P> cache) Initializes the cache.
P	readPage(int pageID) Reads the page with the given id from this file.
void	resetPageAccess() Resets the counters for page accesses of this file and flushes the cache.
void	setCacheSize(int cacheSize) Sets the maximum size of the cache of this file.
void	setNextPageID(int nextPageID) Sets the next page id.
void	setPageID(P page) Sets the id of the given page.
int	writePage(P page) Writes a page into this file.

Methods inherited from class java.lang.Object

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

Methods inherited from interface de.lmu.ifi.dbs.elki.persistent.CachedFile

objectRemoved

Field Detail

cache

protected Cache<P extends Page<P>> cache

The cache of this file.

emptyPages

protected Stack<Integer> emptyPages

A stack holding the empty page ids.

nextPageID

protected int nextPageID

The last page ID.

readAccess

protected long readAccess

The read I/O-Access of this file.

writeAccess

protected long writeAccess

The write I/O-Access of this file.

pageSize

protected int pageSize

The size of a page in Bytes.

Constructor Detail

PageFile

protected PageFile()

Creates a new PageFile.

Method Detail

getPhysicalReadAccess

public final long getPhysicalReadAccess()

Returns the physical read I/O-Accesses of this file.

Returns:

Number of physical read I/O accesses

getPhysicalWriteAccess

public final long getPhysicalWriteAccess()

Returns the physical write I/O-Accesses of this file.

Returns:

Number of physical write I/O accesses

getLogicalPageAccess

public final long getLogicalPageAccess()

Returns the logical read I/O-Accesses of this file.

Returns:

Number of logical I/O accesses

resetPageAccess

public final void resetPageAccess()

Resets the counters for page accesses of this file and flushes the cache.

setPageID

public void setPageID(P page)

Sets the id of the given page.

Parameters:

page - the page to set the id

writePage

public final int writePage(P page)

Writes a page into this file. The method tests if the page has already an id, otherwise a new id is assigned and returned.

Parameters:

page - the page to be written

Returns:

the id of the page

readPage

public P readPage(int pageID)

Reads the page with the given id from this file.

Parameters:

pageID - the id of the page to be returned

Returns:

the page with the given pageId

deletePage

public void deletePage(int pageID)

Deletes the node with the specified id from this file.

Parameters:

pageID - the id of the node to be deleted

close

public void close()

Closes this file.

clear

public void clear()

Clears this PageFile.

setCacheSize

public void setCacheSize(int cacheSize)

Sets the maximum size of the cache of this file.

Parameters:

cacheSize -

initCache

protected void initCache(int pageSize,
                         int cacheSize,
                         Cache<P> cache)

Initializes the cache.

Parameters:

pageSize - the size of a page in Bytes

cacheSize - the size of the cache in Byte

cache - the class of the cache to be used

getNextEmptyPageID

private Integer getNextEmptyPageID()

Returns the next empty page id.

Returns:

the next empty page id

getNextPageID

public int getNextPageID()

Returns the next page id.

Returns:

the next page id

setNextPageID

public void setNextPageID(int nextPageID)

Sets the next page id.

Parameters:

nextPageID - the next page id to be set