jdbm.htree

Class HashDirectory

java.lang.Object

jdbm.htree.HashNode

jdbm.htree.HashDirectory

All Implemented Interfaces:

java.io.Externalizable, java.io.Serializable

final class HashDirectory
extends HashNode
implements java.io.Externalizable

Hashtable directory page.

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
class	HashDirectory.HDIterator Utility class to enumerate keys/values in a HTree

Field Summary

Fields

Modifier and Type	Field and Description
private long[]	_children Record ids of children pages.
private byte	_depth Depth of this directory page, zero-based
private long	_recid This directory's record ID in the PageManager.
private RecordManager	_recman PageManager used to persist changes in directory and buckets
(package private) static int	BIT_SIZE Number of significant bits per directory level.
(package private) static int	MAX_CHILDREN Maximum number of children in a directory.
(package private) static int	MAX_DEPTH Maximum number of levels (zero-based) (4 * 8 bits = 32 bits, which is the size of an "int", and as you know, hashcodes in Java are "ints")
(package private) static long	serialVersionUID

Constructor Summary

Constructors

Constructor and Description
HashDirectory() Public constructor used by serialization
HashDirectory(byte depth) Construct a HashDirectory

Method Summary

Modifier and Type	Method and Description
(package private) java.lang.Object	get(java.lang.Object key) Returns the value which is associated with the given key.
(package private) long	getRecid() Get the record identifier used to load this hashtable.
private int	hashCode(java.lang.Object key) Calculates the hashcode of a key, based on the current directory depth.
(package private) int	hashMask() Calculates the hashmask of this directory.
(package private) boolean	isEmpty() Returns whether or not this directory is empty.
(package private) FastIterator	keys() Returns an enumeration of the keys contained in this
(package private) java.lang.Object	put(java.lang.Object key, java.lang.Object value) Associates the specified value with the specified key.
void	readExternal(java.io.ObjectInput in) Implement Externalizable interface
(package private) java.lang.Object	remove(java.lang.Object key) Remove the value which is associated with the given key.
(package private) void	setPersistenceContext(RecordManager recman, long recid) Sets persistence context.
(package private) FastIterator	values() Returns an enumeration of the values contained in this
void	writeExternal(java.io.ObjectOutput out) Implement Externalizable interface

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

static final long serialVersionUID

See Also:

Constant Field Values

MAX_CHILDREN

static final int MAX_CHILDREN

Maximum number of children in a directory. (Must be a power of 2 -- if you update this value, you must also update BIT_SIZE and MAX_DEPTH.)

See Also:

Constant Field Values

BIT_SIZE

static final int BIT_SIZE

Number of significant bits per directory level.

See Also:

Constant Field Values

MAX_DEPTH

static final int MAX_DEPTH

Maximum number of levels (zero-based) (4 * 8 bits = 32 bits, which is the size of an "int", and as you know, hashcodes in Java are "ints")

See Also:

Constant Field Values

_children

private long[] _children

Record ids of children pages.

_depth

private byte _depth

Depth of this directory page, zero-based

_recman

private transient RecordManager _recman

PageManager used to persist changes in directory and buckets

_recid

private transient long _recid

This directory's record ID in the PageManager. (transient)

Constructor Detail

HashDirectory

public HashDirectory()

Public constructor used by serialization

HashDirectory

HashDirectory(byte depth)

Construct a HashDirectory

Parameters:

depth - Depth of this directory page.

Method Detail

setPersistenceContext

void setPersistenceContext(RecordManager recman,
                           long recid)

Sets persistence context. This method must be called before any persistence-related operation.

Parameters:

recman - RecordManager which stores this directory

recid - Record id of this directory.

getRecid

long getRecid()

Get the record identifier used to load this hashtable.

isEmpty

boolean isEmpty()

Returns whether or not this directory is empty. A directory is empty when it no longer contains buckets or sub-directories.

get

java.lang.Object get(java.lang.Object key)
              throws java.io.IOException

Returns the value which is associated with the given key. Returns null if there is not association for this key.

Parameters:

key - key whose associated value is to be returned

Throws:

java.io.IOException

put

java.lang.Object put(java.lang.Object key,
                     java.lang.Object value)
              throws java.io.IOException

Associates the specified value with the specified key.

Parameters:

key - key with which the specified value is to be assocated.

value - value to be associated with the specified key.

Returns:

object which was previously associated with the given key, or null if no association existed.

Throws:

java.io.IOException

remove

java.lang.Object remove(java.lang.Object key)
                 throws java.io.IOException

Remove the value which is associated with the given key. If the key does not exist, this method simply ignores the operation.

Parameters:

key - key whose associated value is to be removed

Returns:

object which was associated with the given key, or null if no association existed with given key.

Throws:

java.io.IOException

hashCode

private int hashCode(java.lang.Object key)

Calculates the hashcode of a key, based on the current directory depth.

hashMask

int hashMask()

Calculates the hashmask of this directory. The hashmask is the bit mask applied to a hashcode to retain only bits that are relevant to this directory level.

keys

FastIterator keys()
           throws java.io.IOException

Returns an enumeration of the keys contained in this

Throws:

java.io.IOException

values

FastIterator values()
             throws java.io.IOException

Returns an enumeration of the values contained in this

Throws:

java.io.IOException

writeExternal

public void writeExternal(java.io.ObjectOutput out)
                   throws java.io.IOException

Implement Externalizable interface

Specified by:

writeExternal in interface java.io.Externalizable

Throws:

java.io.IOException

readExternal

public void readExternal(java.io.ObjectInput in)
                  throws java.io.IOException,
                         java.lang.ClassNotFoundException

Implement Externalizable interface

Specified by:

readExternal in interface java.io.Externalizable

Throws:

java.io.IOException

java.lang.ClassNotFoundException