de.lmu.ifi.dbs.elki.persistent
Class DefaultPageHeader

java.lang.Object
  de.lmu.ifi.dbs.elki.persistent.DefaultPageHeader

All Implemented Interfaces:

PageHeader

Direct Known Subclasses:

TreeIndexHeader

public class DefaultPageHeader
extends Object
implements PageHeader

Default implementation of a page header.

Author:

Elke Achtert

Field Summary

private static int	FILE_VERSION Version number of this header (magic number).
private int	pageSize The size of a page in bytes.
private static int	SIZE The size of this header in Bytes, which is 8 Bytes ( 4 Bytes for FILE_VERSION and 4 Bytes for pageSize).

Constructor Summary

DefaultPageHeader()
Empty constructor for serialization.

DefaultPageHeader(int pageSize)
Creates a new header with the specified parameters.

Method Summary

byte[]	asByteArray() Return the header as byte array
int	getPageSize() Returns the size of a page in Bytes.
int	getReservedPages() Returns the number of pages necessary for the header
void	readHeader(byte[] data) Initializes this header from the given Byte array.
void	readHeader(RandomAccessFile file) Initializes this header from the specified file.
int	size() Returns the value of SIZE).
void	writeHeader(RandomAccessFile file) Writes this header to the specified file.

Methods inherited from class java.lang.Object

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

Field Detail

SIZE

private static final int SIZE

The size of this header in Bytes, which is 8 Bytes ( 4 Bytes for FILE_VERSION and 4 Bytes for pageSize).

See Also:

Constant Field Values

FILE_VERSION

private static final int FILE_VERSION

Version number of this header (magic number).

See Also:

Constant Field Values

pageSize

private int pageSize

The size of a page in bytes.

Constructor Detail

DefaultPageHeader

public DefaultPageHeader()

Empty constructor for serialization.

DefaultPageHeader

public DefaultPageHeader(int pageSize)

Creates a new header with the specified parameters.

Parameters:

pageSize - the size of a page in bytes

Method Detail

size

public int size()

Returns the value of SIZE).

Specified by:

size in interface PageHeader

Returns:

the size of this header in Bytes

readHeader

public void readHeader(RandomAccessFile file)
                throws IOException

Initializes this header from the specified file. Looks for the right version and reads the integer value of pageSize from the file.

Specified by:

readHeader in interface PageHeader

Parameters:

file - the file to which this header belongs

Throws:

IOException - if an I/O-error occurs during reading

readHeader

public void readHeader(byte[] data)

Initializes this header from the given Byte array. Looks for the right version and reads the integer value of pageSize from the file.

Specified by:

readHeader in interface PageHeader

Parameters:

data - byte array with the page data.

writeHeader

public void writeHeader(RandomAccessFile file)
                 throws IOException

Writes this header to the specified file. Writes the version of this header and the integer value of pageSize to the file.

Specified by:

writeHeader in interface PageHeader

Parameters:

file - the file to which this header belongs

Throws:

IOException - IOException if an I/O-error occurs during writing

asByteArray

public byte[] asByteArray()

Description copied from interface: PageHeader

Return the header as byte array

Specified by:

asByteArray in interface PageHeader

Returns:

header as byte array

getPageSize

public int getPageSize()

Returns the size of a page in Bytes.

Specified by:

getPageSize in interface PageHeader

Returns:

the size of a page in Bytes

getReservedPages

public int getReservedPages()

Returns the number of pages necessary for the header

Specified by:

getReservedPages in interface PageHeader

Returns:

the number of pages