jdbm.recman
Class PageHeader

java.lang.Object
  jdbm.recman.PageHeader

All Implemented Interfaces:

BlockView

public class PageHeader
extends Object
implements BlockView

This class represents a page header. It is the common superclass for all different page views. It contains the following information:

1. 2 bytes: the short block type code
2. 8 bytes: the long block id of the next block in the block list
3. 8 bytes: the long block id of the previous block in the block list
4. 4 bytes: the size of this page

The page header block view hence sees 18 bytes of page header data.

Field Summary

protected BlockIo	blockIo the page header block this view is associated with
protected static short	SIZE the size of this page header

Constructor Summary

protected

PageHeader(BlockIo blockIo) Constructs a PageHeader object from a block

Method Summary

protected void	paranoiaMagicOk() For paranoia mode
String	toString()

Methods inherited from class java.lang.Object

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

Field Detail

SIZE

protected static final short SIZE

the size of this page header

See Also:

Constant Field Values

blockIo

protected BlockIo blockIo

the page header block this view is associated with

Constructor Detail

PageHeader

protected PageHeader(BlockIo blockIo)

Constructs a PageHeader object from a block

Parameters:

blockIo - The block that contains the page header

Throws:

IOException - if the block is too short to keep the page header.

Method Detail

paranoiaMagicOk

protected void paranoiaMagicOk()

For paranoia mode

toString

public String toString()

Overrides:

toString in class Object