org.basex.data
Class DiskData

java.lang.Object
  org.basex.data.Data
      org.basex.data.DiskData

public final class DiskData
extends Data

This class stores and organizes the node table and the index structures for textual content. All nodes in the table are accessed by their implicit pre value. Some restrictions on the data are currently given:

• The table is limited to 2^31 entries (pre values are signed int's)
• A maximum of 2^16 different tag and attribute names is allowed
• A tag can have a maximum of 256 attributes

Each node occupies 128 bits. The current storage layout looks like follows:

 ELEMENT NODES:
 - Byte     0:  KIND: Node kind (ELEM)
 - Byte   1-2:  NSPC: Namespace (4), NS Definition flag (1) and Name (11 bits)
 - Byte     3:  ATTS: Number of attributes
 - Byte  4- 7:  DIST: Distance to parent node
 - Byte  8-11:  SIZE: Number of descendants
 - Byte 12-15:  UNID: Unique Node ID
 DOCUMENT NODES:
 - Byte     0:  KIND: Node kind (DOC)
 - Byte  3- 7:  TEXT: Text reference
 - Byte  8-11:  SIZE: Number of descendants
 - Byte 12-15:  UNID: Unique Node ID
 TEXT NODES:
 - Byte     0:  KIND: Node kind (TEXT/COMM/PI)
 - Byte  3- 7:  TEXT: Text reference
 - Byte  8-11:  DIST: Distance to parent node
 - Byte 12-15:  UNID: Unique Node ID
 ATTRIBUTE NODES:
 - Byte     0:  KIND: Node kind (ATTR)
 - Byte   1-2:  NSPC: Namespace (4) and Name (11 bits)
 - Byte  3- 7:  TEXT: Attribute value reference
 - Byte    11:  DIST: Distance to parent node
 - Byte 12-15:  UNID: Unique Node ID
 

Author:

Workgroup DBIS, University of Konstanz 2005-08, ISC License, Christian Gruen, Tim Petrowsky

Field Summary

Fields inherited from class org.basex.data.Data

ATTR, atts, COMM, DOC, ELEM, fs, meta, nameID, ns, PI, size, sizeID, skel, tags, TEXT

Constructor Summary

DiskData(java.lang.String db)
Default Constructor.

DiskData(java.lang.String db, boolean index)
Constructor, specifying if indexes are to be opened as well.

Method Summary

int	attLen(int pre) Returns an attribute value length.
int	attNameID(int pre) Returns an attribute name id (reference to the attribute name index).
int	attNS(int pre) Returns an attribute namespace (reference to the attribute namespace).
double	attNum(int pre) Returns an attribute value as double value.
int	attSize(int pre, int kind) Returns a number of attributes.
byte[]	attValue(int pre) Returns an attribute value.
void	close() Closes the current database.
void	closeIndex(IndexToken.Type index) Closes the specified index.
void	cls() Closes the database without writing data back to disk.
void	delete(int pre) Deletes a node and its descendants.
void	flush() Flushes the table data.
int	id(int pre) Returns a unique node id.
void	insert(int pre, int par, byte[] name, byte[] val) Inserts an attribute.
void	insert(int pre, int par, byte[] val, int kind) Inserts a tag name, text node, comment or processing instruction.
void	insert(int pre, int par, Data dt) Insert a data instance at the specified pre value.
int	kind(int pre) Returns a node kind.
int[]	ns(int pre) Returns namespace key and value ids.
int	parent(int pre, int kind) Returns a pre value of the parent node.
int	pre(int id) Returns a pre value.
void	setIndex(IndexToken.Type type, Index index) Assigns the specified index.
int	size(int pre, int k) Returns a size value (number of descendant table entries).
int	tagID(int pre) Returns a tag id (reference to the tag index).
int	tagNS(int pre) Returns a tag namespace (reference to the tag namespace).
byte[]	text(int pre) Returns a text.
int	textLen(int pre) Returns a text length.
double	textNum(int pre) Returns a text as double value.
void	update(int pre, byte[] val) Updates a tag name, text node, comment or processing instruction.
void	update(int pre, byte[] name, byte[] val) Updates an attribute name and value.

Methods inherited from class org.basex.data.Data

atom, atomNum, attName, attNameID, attValue, doc, ids, info, initNames, nrIDs, tag, tagID, update

Methods inherited from class java.lang.Object

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

Constructor Detail

DiskData

public DiskData(java.lang.String db)
         throws java.io.IOException

Default Constructor.

Parameters:

db - name of database

Throws:

java.io.IOException - IO Exception

DiskData

public DiskData(java.lang.String db,
                boolean index)
         throws java.io.IOException

Constructor, specifying if indexes are to be opened as well.

Parameters:

db - name of database

index - open indexes

Throws:

java.io.IOException - IO Exception

Method Detail

flush

public void flush()

Description copied from class: Data

Flushes the table data.

Specified by:

flush in class Data

close

public void close()
           throws java.io.IOException

Description copied from class: Data

Closes the current database.

Specified by:

close in class Data

Throws:

java.io.IOException - in case the database could not be closed

cls

public void cls()
         throws java.io.IOException

Closes the database without writing data back to disk.

Throws:

java.io.IOException - I/O exception

closeIndex

public void closeIndex(IndexToken.Type index)
                throws java.io.IOException

Description copied from class: Data

Closes the specified index.

Specified by:

closeIndex in class Data

Parameters:

index - index to be closed

Throws:

java.io.IOException - in case the index could not be closed

setIndex

public void setIndex(IndexToken.Type type,
                     Index index)

Description copied from class: Data

Assigns the specified index.

Specified by:

setIndex in class Data

Parameters:

type - index to be opened

index - index instance

id

public int id(int pre)

Description copied from class: Data

Returns a unique node id.

Specified by:

id in class Data

Parameters:

pre - pre value

Returns:

node id

pre

public int pre(int id)

Description copied from class: Data

Returns a pre value.

Specified by:

pre in class Data

Parameters:

id - unique node id

Returns:

pre value or -1 if id was not found

kind

public int kind(int pre)

Description copied from class: Data

Returns a node kind.

Specified by:

kind in class Data

Parameters:

pre - pre value

Returns:

node kind

parent

public int parent(int pre,
                  int kind)

Description copied from class: Data

Returns a pre value of the parent node.

Specified by:

parent in class Data

Parameters:

pre - pre value

kind - node kind

Returns:

pre value of the parent node

attSize

public int attSize(int pre,
                   int kind)

Description copied from class: Data

Returns a number of attributes.

Specified by:

attSize in class Data

Parameters:

pre - pre value

kind - node kind

Returns:

number of attributes

size

public int size(int pre,
                int k)

Description copied from class: Data

Returns a size value (number of descendant table entries).

Specified by:

size in class Data

Parameters:

pre - pre value

k - node kind

Returns:

size value

tagID

public int tagID(int pre)

Description copied from class: Data

Returns a tag id (reference to the tag index).

Specified by:

tagID in class Data

Parameters:

pre - pre value

Returns:

token reference

tagNS

public int tagNS(int pre)

Description copied from class: Data

Returns a tag namespace (reference to the tag namespace).

Specified by:

tagNS in class Data

Parameters:

pre - pre value

Returns:

token reference

ns

public int[] ns(int pre)

Description copied from class: Data

Returns namespace key and value ids.

Specified by:

ns in class Data

Parameters:

pre - pre value

Returns:

key and value ids

attNameID

public int attNameID(int pre)

Description copied from class: Data

Returns an attribute name id (reference to the attribute name index).

Specified by:

attNameID in class Data

Parameters:

pre - pre value

Returns:

token reference

attNS

public int attNS(int pre)

Description copied from class: Data

Returns an attribute namespace (reference to the attribute namespace).

Specified by:

attNS in class Data

Parameters:

pre - pre value

Returns:

token reference

text

public byte[] text(int pre)

Description copied from class: Data

Returns a text.

Specified by:

text in class Data

Parameters:

pre - pre value

Returns:

atomized value

attValue

public byte[] attValue(int pre)

Description copied from class: Data

Returns an attribute value.

Specified by:

attValue in class Data

Parameters:

pre - pre value

Returns:

atomized value

textNum

public double textNum(int pre)

Description copied from class: Data

Returns a text as double value.

Specified by:

textNum in class Data

Parameters:

pre - pre value

Returns:

numeric value

attNum

public double attNum(int pre)

Description copied from class: Data

Returns an attribute value as double value.

Specified by:

attNum in class Data

Parameters:

pre - pre value

Returns:

numeric value

textLen

public int textLen(int pre)

Description copied from class: Data

Returns a text length.

Specified by:

textLen in class Data

Parameters:

pre - pre value

Returns:

length

attLen

public int attLen(int pre)

Description copied from class: Data

Returns an attribute value length.

Specified by:

attLen in class Data

Parameters:

pre - pre value

Returns:

length

update

public void update(int pre,
                   byte[] val)

Description copied from class: Data

Updates a tag name, text node, comment or processing instruction.

Specified by:

update in class Data

Parameters:

pre - pre of the text node to change

val - value to be updated

update

public void update(int pre,
                   byte[] name,
                   byte[] val)

Description copied from class: Data

Updates an attribute name and value.

Specified by:

update in class Data

Parameters:

pre - pre of node to insert after

name - attribute name

val - attribute value

delete

public void delete(int pre)

Description copied from class: Data

Deletes a node and its descendants.

Specified by:

delete in class Data

Parameters:

pre - pre value of the node to delete

insert

public void insert(int pre,
                   int par,
                   byte[] val,
                   int kind)

Description copied from class: Data

Inserts a tag name, text node, comment or processing instruction.

Specified by:

insert in class Data

Parameters:

pre - pre value

par - parent of node

val - value to be inserted

kind - node kind

insert

public void insert(int pre,
                   int par,
                   byte[] name,
                   byte[] val)

Description copied from class: Data

Inserts an attribute.

Specified by:

insert in class Data

Parameters:

pre - pre value

par - parent of node

name - attribute name

val - attribute value

insert

public void insert(int pre,
                   int par,
                   Data dt)

Description copied from class: Data

Insert a data instance at the specified pre value. Note that the specified data instance must differ from this instance.

Specified by:

insert in class Data

Parameters:

pre - pre value

par - parent of node

dt - data instance to copy from