uk.ac.starlink.table

Class WrapperStarTable

java.lang.Object

uk.ac.starlink.table.WrapperStarTable

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, StarTable

Direct Known Subclasses:

ColumnPermutedStarTable, ColumnStoreStarTable, ConcatStarTable, EmptyStarTable, ExplodedStarTable, MetaCopyStarTable, ProgressBarStarTable, ProgressLineStarTable, RowPermutedStarTable, RowSubsetStarTable, SelectorStarTable

public class WrapperStarTable
extends java.lang.Object
implements StarTable

StarTable which wraps another StarTable. This class acts as a wrapper around an existing 'base' StarTable object; almost all its methods are implemented by forwarding to the corresponding methods of that base table. The exception is the getURL() method which returns null as an indication that the actual table is not a persistent one (though it may be based on, and even identical to, a persistent one).

This class is provided so that it can be extended by subclasses which modify the view of the base table in useful ways.

Subclasses should take care to ensure that all the data access methods are overridden in a consistent way: getCell(long, int), getRow(long), getRowSequence(), getRowAccess() and getRowSplittable().

See Also:

WrapperRowSequence

Field Summary

Fields

Modifier and Type	Field and Description
protected StarTable	baseTable

Constructor Summary

Constructors

Constructor and Description
WrapperStarTable(StarTable baseTable) Constructs a new WrapperStarTable from a given base table.

Method Summary

Modifier and Type	Method and Description
static int	checkedLongToInt(long lval) Convenience method to get an int value from a long.
void	close() Relinquishes any resources associated with this table.
StarTable	getBaseTable() Returns the base table underlying this wrapper table.
java.lang.Object	getCell(long irow, int icol) Returns the contents of a given table cell.
java.util.List<ValueInfo>	getColumnAuxDataInfos() Returns an ordered list of ValueInfo objects representing the auxiliary metadata returned by getColumnInfo(int).getAuxData() calls.
int	getColumnCount() Returns the number of columns in this table.
ColumnInfo	getColumnInfo(int icol) Returns the object describing the data in a given column.
java.lang.String	getName() Returns the name of this table, if it has one.
DescribedValue	getParameterByName(java.lang.String parname) Returns a parameter (table-wide metadata item) of this table located by its name.
java.util.List<DescribedValue>	getParameters() Returns a list of table parameters, that is metadata items which pertain to the entire table.
java.lang.Object[]	getRow(long irow) Returns the contents of a given table row.
RowAccess	getRowAccess() Returns an object which can provide random access to this table's data, if random access is implemented.
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.
java.net.URL	getURL() Initially returns null to indicate that this table itself is not persistent.
boolean	isRandom() Indicates whether random access is provided by this table.
void	setName(java.lang.String name) Sets the name of this table.
void	setParameter(DescribedValue dval) Adds the given DescribedValue to the list of parameter metadata objects associated with this table.
void	setURL(java.net.URL url) Sets the URL of this table.
java.lang.String	toString() Returns an indication of the wrapper structure of this table.

Methods inherited from class java.lang.Object

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

Field Detail

baseTable

protected StarTable baseTable

Constructor Detail

WrapperStarTable

public WrapperStarTable(StarTable baseTable)

Constructs a new WrapperStarTable from a given base table.

Parameters:

baseTable - the table to which methods invoked upon the new wrapper table will be forwarded

Method Detail

getBaseTable

public StarTable getBaseTable()

Returns the base table underlying this wrapper table.

Returns:

the table to which methods invoked upon this wrappter table are forwarded

getColumnCount

public int getColumnCount()

Description copied from interface: StarTable

Returns the number of columns in this table.

Specified by:

getColumnCount in interface StarTable

Returns:

the number of columns

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

Returns:

the number of rows, or -1

getURL

public java.net.URL getURL()

Initially returns null to indicate that this table itself is not persistent.

Specified by:

getURL in interface StarTable

Returns:

the URL of this table, or null if none is known

setURL

public void setURL(java.net.URL url)

Description copied from interface: StarTable

Sets the URL of this table. It ought to be possible in principle to reconstruct this table by reading the resource at url. If called, the supplied url should provide the return value for subsequent calls of StarTable.getURL().

Specified by:

setURL in interface StarTable

Parameters:

url - table URL

getName

public java.lang.String getName()

Description copied from interface: StarTable

Returns the name of this table, if it has one. The meaning of the name is not defined, but it will typically be a short string of text indicating the identity of this table.

Specified by:

getName in interface StarTable

Returns:

a name for this table, or null if no suitable one exists

setName

public void setName(java.lang.String name)

Description copied from interface: StarTable

Sets the name of this table. If called, the supplied name should provide the return value for subsequent calls of StarTable.getName().

Specified by:

setName in interface StarTable

Parameters:

name - table name

getParameters

public java.util.List<DescribedValue> getParameters()

Description copied from interface: StarTable

Returns a list of table parameters, that is metadata items which pertain to the entire table.

Specified by:

getParameters in interface StarTable

Returns:

a List of DescribedValue objects constituting table-wide metadata not covered elsewhere in this interface

getParameterByName

public DescribedValue getParameterByName(java.lang.String parname)

Description copied from interface: StarTable

Returns a parameter (table-wide metadata item) of this table located by its name. If more than one parameter with the given name exists, an arbitrary one will be returned. If no parameter with the given name exists, null will be returned.

Specified by:

getParameterByName in interface StarTable

Parameters:

parname - the name of the table parameter required

setParameter

public void setParameter(DescribedValue dval)

Description copied from interface: StarTable

Adds the given DescribedValue to the list of parameter metadata objects associated with this table. If an item in the parameter list with the same name as the supplied value already exists, it is removed from the list.

Specified by:

setParameter in interface StarTable

Parameters:

dval - the new parameter datum to add

getColumnInfo

public ColumnInfo getColumnInfo(int icol)

Description copied from interface: StarTable

Returns the object describing the data in a given column.

Specified by:

getColumnInfo in interface StarTable

Parameters:

icol - the column for which header information is required

Returns:

a ValueInfo object for column icol

getColumnAuxDataInfos

public java.util.List<ValueInfo> getColumnAuxDataInfos()

Description copied from interface: StarTable

Returns an ordered list of ValueInfo objects representing the auxiliary metadata returned by getColumnInfo(int).getAuxData() calls. The idea is that the resulting list can be used to find out the kind of per-column metadata which can be expected to be found in some or all columns of this table. Each item in the returned list should have a unique name, and other characteristics which are applicable to auxData items which may be returned from any of the columns in this table.

The order of the list may indicate some sort of natural ordering of these keys. The returned list is not guaranteed to be complete; it is legal to return an empty list if nothing is known about auxiliary metadata. The list ought not to contain duplicate elements.

Specified by:

getColumnAuxDataInfos in interface StarTable

Returns:

an unmodifiable ordered set of known metadata keys

See Also:

DefaultValueInfo.getAuxData()

getRowSequence

public RowSequence getRowSequence()
                           throws java.io.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

Returns:

new RowSequence

Throws:

java.io.IOException - if there is an error providing access

getRowAccess

public RowAccess getRowAccess()
                       throws java.io.IOException

Description copied from interface: StarTable

Returns an object which can provide random access to this table's data, if random access is implemented. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowAccess in interface StarTable

Returns:

new RowAccess

Throws:

java.io.IOException - if there is an error setting up access

getRowSplittable

public RowSplittable getRowSplittable()
                               throws java.io.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

Returns:

new RowSplittable

Throws:

java.io.IOException

See Also:

RowRunner

isRandom

public boolean isRandom()

Description copied from interface: StarTable

Indicates whether random access is provided by this table. Only if the result is true may the StarTable.getRowAccess(), StarTable.getRow(long) and StarTable.getCell(long, int) methods be used.

Specified by:

isRandom in interface StarTable

Returns:

true if table random access methods are available

getCell

public java.lang.Object getCell(long irow,
                                int icol)
                         throws java.io.IOException

Description copied from interface: StarTable

Returns the contents of a given table cell. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass().

This method is safe for concurrent use from multiple threads, but in general it is recommended to use a RowAccess instead.

Specified by:

getCell in interface StarTable

Parameters:

irow - the index of the cell's row

icol - the index of the cell's column

Returns:

the contents of this cell

Throws:

java.io.IOException - if there is an error reading the data

getRow

public java.lang.Object[] getRow(long irow)
                          throws java.io.IOException

Description copied from interface: StarTable

Returns the contents of a given table row. The returned value is equivalent to an array formed of all the objects returned by getCell(irow,icol) for all the columns icol in sequence.

This method is safe for concurrent use from multiple threads, but in general it is recommended to use a RowAccess instead.

Specified by:

getRow in interface StarTable

Parameters:

irow - the index of the row to retrieve

Returns:

an array of the objects in each cell in row irow

Throws:

java.io.IOException - if there is an error reading the data

close

public void close()
           throws java.io.IOException

Description copied from interface: StarTable

Relinquishes any resources associated with this table. This may do nothing, and calling it is often not required, but it provides an opportunity to force release of file descriptors or other resources that are not well handled by garbage collection if the table itself holds them. It is not intended for release of heap-based resources, for which garbage collection already provides adequate management.

Following a call to this method, any attempt to use this table or objects such as RowSequences obtained from it will result in undefined behaviour.

Specified by:

close in interface java.io.Closeable

Specified by:

close in interface java.lang.AutoCloseable

Specified by:

close in interface StarTable

Throws:

java.io.IOException

checkedLongToInt

public static int checkedLongToInt(long lval)

Convenience method to get an int value from a long. Invokes Tables.checkedLongToInt(long).

toString

public java.lang.String toString()

Returns an indication of the wrapper structure of this table.

Overrides:

toString in class java.lang.Object

Returns:

string representation