DiskData

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org.basex.data
Class DiskData

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

public final class DiskData
extends Data
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 maximum of 2^4 different namespaces is allowed
A tag can have a maximum of 256 attributes

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

 COMMON ATTRIBUTES:
 - Byte     0:  KIND: Node kind (0-2)
 ELEMENT NODES:
 - Byte     0:  NSPC: Namespace (4-7), NS Definition flag (3)
 - Byte   1-2:  NAME: Name
 - 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  3- 7:  TEXT: Text reference
 - Byte  8-11:  SIZE: Number of descendants
 - Byte 12-15:  UNID: Unique Node ID
 TEXT NODES:
 - 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:  NSPC: Namespace (4-7)
 - Byte   1-2:  NAME: Name
 - 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 2005-09, ISC License, Christian Gruen, Tim Petrowsky

Nested Class Summary

Nested classes/interfaces inherited from class org.basex.data.Data
`Data.Type`

Field Summary
`TableAccess`	`table` Table access file.

Fields inherited from class org.basex.data.Data
`ATTR, atts, COMM, DOC, ELEM, fs, meta, nameID, ns, path, PI, sizeID, tags, TEXT`

Constructor Summary
`DiskData(MetaData md, Names nm, Names at, PathSummary ps, Namespaces n)` Internal constructor, specifying all meta data.
`DiskData(java.lang.String db, Prop pr)` Default constructor.

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`	`closeIndex(Data.Type type)` Closes the specified index.
`void`	`cls()` Internal method to close the database.
`void`	`delete(int pre)` Deletes a node and its descendants.
`void`	`flush()` Flushes the table data.
`int`	`getLock()` Returns the locking situation of the data.
`int`	`id(int pre)` Returns a unique node id.
`void`	`init()` Dissolves the references to often used tag names and attributes.
`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)` Inserts 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(Data.Type type, Index index)` Assigns the specified index.
`void`	`setLock(int l)` Locks and unlocks the data reference.
`int`	`size(int pre, int kind)` 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, attName, attNameID, attValue, close, doc, ids, info, nrIDs, tag, tagID, toString`

Methods inherited from class java.lang.Object
`equals, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Field Detail

table

public TableAccess table

Table access file.

Constructor Detail

DiskData

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

Default constructor.

Parameters:: db - name of database; pr - database properties
Throws:: java.io.IOException - IO Exception

DiskData

public DiskData(MetaData md,
                Names nm,
                Names at,
                PathSummary ps,
                Namespaces n)
         throws java.io.IOException

Internal constructor, specifying all meta data.

Parameters:: md - meta data; nm - tags; at - attributes; ps - path summary; n - namespaces
Throws:: java.io.IOException - IO Exception

Method Detail