uk.ac.starlink.table

Class RowSubsetStarTable

java.lang.Object

uk.ac.starlink.table.WrapperStarTable

uk.ac.starlink.table.RowSubsetStarTable

All Implemented Interfaces:

Closeable, AutoCloseable, StarTable

public class RowSubsetStarTable
extends WrapperStarTable

Wraps a StarTable to present only a subset of its rows. A BitSet is used to keep track of which rows in the base table should be visible from this one; a set (true) bit in the mask indicates a row in the base table which will be visible in this one. It is the responsibility of the user to ensure that no bits in the mask are set beyond the end of the underlying table - behaviour is undefined in the case that this condition is violated (but probably procured RowSequence objects will misbehave).

Author:

Mark Taylor (Starlink)

Field Summary

Fields inherited from class uk.ac.starlink.table.WrapperStarTable

baseTable

Constructor Summary

Constructors

Constructor and Description
RowSubsetStarTable(StarTable baseTable) Constructs a new RowSubsetStarTable with no rows showing, in which a set bit in the mask indicates a visible row.
RowSubsetStarTable(StarTable baseTable, BitSet mask) Constructs a new RowSubsetStarTable with a given mask.

Method Summary

Modifier and Type	Method and Description
BitSet	getMask() Returns the bit mask which defines which rows are seen.
long	getRowCount() Returns the number of rows in this table, if known.
RowSequence	getRowSequence() Returns an object which can iterate over all the rows in the table sequentially.
RowSplittable	getRowSplittable() Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.
boolean	isRandom() Returns false.
void	setMask(BitSet mask) Sets the mask which determines which rows are seen.

Methods inherited from class uk.ac.starlink.table.WrapperStarTable

checkedLongToInt, close, getBaseTable, getCell, getColumnAuxDataInfos, getColumnCount, getColumnInfo, getName, getParameterByName, getParameters, getRow, getRowAccess, getURL, setName, setParameter, setURL, toString

Methods inherited from class java.lang.Object

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

Constructor Detail

RowSubsetStarTable

public RowSubsetStarTable(StarTable baseTable)

Constructs a new RowSubsetStarTable with no rows showing, in which a set bit in the mask indicates a visible row.

Parameters:

baseTable - base table which provides the underlying data

RowSubsetStarTable

public RowSubsetStarTable(StarTable baseTable,
                          BitSet mask)

Constructs a new RowSubsetStarTable with a given mask.

Parameters:

baseTable - base table which provides the underlying data

mask - bitmask determining which rows in baseTable are seen

Method Detail

getMask

public BitSet getMask()

Returns the bit mask which defines which rows are seen.

Returns:

row mask

setMask

public void setMask(BitSet mask)

Sets the mask which determines which rows are seen.

Parameters:

mask - row mask

isRandom

public boolean isRandom()

Returns false.

Specified by:

isRandom in interface StarTable

Overrides:

isRandom in class WrapperStarTable

Returns:

true if table random access methods are available

getRowCount

public long getRowCount()

Description copied from interface: StarTable

Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.

Specified by:

getRowCount in interface StarTable

Overrides:

getRowCount in class WrapperStarTable

Returns:

the number of rows, or -1

getRowSequence

public RowSequence getRowSequence()
                           throws IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowSequence in interface StarTable

Overrides:

getRowSequence in class WrapperStarTable

Returns:

new RowSequence

Throws:

IOException - if there is an error providing access

getRowSplittable

public RowSplittable getRowSplittable()
                               throws IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table, but which may also be requested to split recursively for potentially parallel processing.

The return value must be non-null, and may provide splitting arrangements specially appropriate for the implementation. If this table 'wraps' an upstream table, it is usually best to base the implementation on calls to the the upstream getRowSplittable method, so that upstream policy about how to divide up the table is respected. However, implementations without special requirements may return Tables.getDefaultRowSplittable(this).

Specified by:

getRowSplittable in interface StarTable

Overrides:

getRowSplittable in class WrapperStarTable

Returns:

new RowSplittable

Throws:

IOException

See Also:

RowRunner