de.lmu.ifi.dbs.elki.persistent

Class OnDiskArrayPageFile<P extends Page>

java.lang.Object

de.lmu.ifi.dbs.elki.persistent.AbstractPageFile<P>

de.lmu.ifi.dbs.elki.persistent.AbstractStoringPageFile<P>

de.lmu.ifi.dbs.elki.persistent.OnDiskArrayPageFile<P>

Type Parameters:

P - Page type

All Implemented Interfaces:

PageFile<P>

public class OnDiskArrayPageFile<P extends Page>
extends AbstractStoringPageFile<P>

A OnDiskArrayPageFile stores objects persistently that implement the Page interface. For convenience each page is represented by a single file. All pages are stored in a specified directory.

Author:

Elke Achtert

Field Summary

Fields

Modifier and Type	Field and Description
private static int	EMPTY_PAGE Indicates an empty page.
private boolean	existed Whether or not the file originally existed
private OnDiskArray	file The file storing the pages.
private File	filename The file name to use
private static int	FILLED_PAGE Indicates a filled page.
protected PageHeader	header The header of this page file.
private static Logging	LOG Class logger.

Fields inherited from class de.lmu.ifi.dbs.elki.persistent.AbstractStoringPageFile

emptyPages, nextPageID, pageSize

Constructor Summary

Constructors

Constructor and Description
OnDiskArrayPageFile(int pageSize, String fileName) Creates a new OnDiskArrayPageFile from an existing file.

Method Summary

Methods

Modifier and Type	Method and Description
private P	byteBufferToPage(ByteBuffer buffer) Reconstruct a serialized object from the specified byte array.
void	clear() Clears this PageFile.
void	close() Closes this file.
void	deletePage(int pageID) Deletes the node with the specified id from this file.
protected Logging	getLogger() Get the class logger.
boolean	initialize(PageHeader header) Initialize the page file with the given header - return "true" if the file already existed.
private byte[]	pageToByteArray(P page) Serializes an object into a byte array.
P	readPage(int pageID) Reads the page with the given id from this file.
void	writePage(int pageID, P page) Write page to disk.

Methods inherited from class de.lmu.ifi.dbs.elki.persistent.AbstractStoringPageFile

getNextPageID, getPageSize, logStatistics, setNextPageID, setPageID

Methods inherited from class de.lmu.ifi.dbs.elki.persistent.AbstractPageFile

countRead, countWrite, writePage

Methods inherited from class java.lang.Object

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

Field Detail

LOG

private static final Logging LOG

Class logger.

EMPTY_PAGE

private static final int EMPTY_PAGE

Indicates an empty page.

See Also:

Constant Field Values

FILLED_PAGE

private static final int FILLED_PAGE

Indicates a filled page.

See Also:

Constant Field Values

filename

private File filename

The file name to use

file

private OnDiskArray file

The file storing the pages.

header

protected PageHeader header

The header of this page file.

existed

private final boolean existed

Whether or not the file originally existed

Constructor Detail

OnDiskArrayPageFile

public OnDiskArrayPageFile(int pageSize,
                   String fileName)

Creates a new OnDiskArrayPageFile from an existing file.

Parameters:

pageSize - page size

fileName - the name of the file

Method Detail

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.

Specified by:

deletePage in interface PageFile<P extends Page>

Overrides:

deletePage in class AbstractStoringPageFile<P extends Page>

Parameters:

pageID - the id of the node to be deleted

writePage

public void writePage(int pageID,
             P page)

Write page to disk.

Specified by:

writePage in class AbstractPageFile<P extends Page>

Parameters:

pageID - page id

page - the page which has to be written to disk

close

public void close()

Closes this file.

Specified by:

close in interface PageFile<P extends Page>

Overrides:

close in class AbstractPageFile<P extends Page>

clear

public void clear()

Clears this PageFile.

byteBufferToPage

private P byteBufferToPage(ByteBuffer buffer)

Reconstruct a serialized object from the specified byte array.

Parameters:

buffer - the buffer from which the object should be reconstructed

Returns:

a serialized object from the specified byte array

pageToByteArray

private byte[] pageToByteArray(P page)

Serializes an object into a byte array.

Parameters:

page - the object to be serialized

Returns:

the byte array

initialize

public boolean initialize(PageHeader header)

Description copied from class: AbstractStoringPageFile

Initialize the page file with the given header - return "true" if the file already existed.

Specified by:

initialize in interface PageFile<P extends Page>

Overrides:

initialize in class AbstractStoringPageFile<P extends Page>

Parameters:

header - Header

Returns:

true when the file already existed.

getLogger

protected Logging getLogger()

Description copied from class: AbstractPageFile

Get the class logger.

Specified by:

getLogger in class AbstractPageFile<P extends Page>

Returns:

Logger