Package nom.tam.image.compression.hdu

Class CompressedTableData

java.lang.Object

nom.tam.fits.Data

nom.tam.fits.AbstractTableData

nom.tam.fits.BinaryTable

nom.tam.image.compression.hdu.CompressedTableData

All Implemented Interfaces:

Cloneable, FitsElement, TableData

public class CompressedTableData
extends BinaryTable

FITS representation of a compressed binary table. It itself is a binary table, but one in which each row represents the compressed image of one or more rows of the original table.

See Also:

• CompressedTableHDU

Nested Class Summary

Nested classes/interfaces inherited from class nom.tam.fits.BinaryTable

BinaryTable.ColumnDesc

Constructor Summary

Constructors

Constructor	Description
CompressedTableData()	Creates a new empty compressed table data to be initialized at a later point
CompressedTableData(Header header)	Creates a new compressed table data based on the prescription of the supplied header.

Method Summary

Modifier and Type	Method	Description
void	compress(Header header)	(for internal use) This should only be called by CompressedTableHDU, and should have reduced visibility accordingly.
long	defragment()	Defragments the heap area of this table, compacting the heap area, and returning the number of bytes by which the heap size has been reduced.
void	fillHeader(Header h)
void	prepareUncompressedData(ColumnTable<?> data)	Deprecated. (for internal use) This should only be called by CompressedTableHDU, and its visibility will be reduced accordingly in the future, not to mention that it should take a BinaryTable as its argument.

Methods inherited from class nom.tam.fits.BinaryTable

addBitsColumn, addColumn, addColumn, addComplexColumn, addFlattenedColumn, addRow, addStringColumn, addVariableSizeColumn, compact, containsHeap, convertToBits, copy, createColumnDataFor, deleteColumns, deleteRows, fromColumnMajor, fromRowMajor, get, getArrayElement, getArrayElementAs, getBases, getColumn, getData, getDescriptor, getDescriptor, getDescriptor, getDimens, getDouble, getElement, getFlatColumns, getFlattenedColumn, getLogical, getLong, getModelRow, getNCols, getNRows, getNumber, getRawElement, getRow, getSizes, getString, getTypes, indexOf, parseTDims, read, reserveHeapSpace, reserveRowSpace, set, setColumn, setComplexColumn, setElement, setFlattenedColumn, setRow, toHDU, updateAfterDelete, write

Methods inherited from class nom.tam.fits.Data

calcChecksum, detach, getFileOffset, getKernel, getSize, isDeferred, isEmpty, reset, rewrite, rewriteable

Methods inherited from class java.lang.Object

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

Methods inherited from interface nom.tam.fits.TableData

addRowEntries, setRowEntries

Constructor Details

CompressedTableData

public CompressedTableData()

Creates a new empty compressed table data to be initialized at a later point

CompressedTableData

public CompressedTableData(Header header)
                    throws FitsException

Creates a new compressed table data based on the prescription of the supplied header.

Parameters:

header - The header that describes the compressed table

Throws:

FitsException - If the header is invalid or could not be accessed.

Method Details

compress

public void compress(Header header)
              throws FitsException

(for internal use) This should only be called by CompressedTableHDU, and should have reduced visibility accordingly.

Parameters:

header - the compressed header

Throws:

FitsException - if the table cannot be compressed.

defragment

public long defragment()
                throws FitsException

Description copied from class: BinaryTable

Defragments the heap area of this table, compacting the heap area, and returning the number of bytes by which the heap size has been reduced. When tables with variable-sized columns are modified, the heap may retain old data as columns are removed or elements get replaced with new data of different size. The data order in the heap may also get jumbled, causing what would appear to be sequential reads to jump all over the heap space with the caching. And, depending on how the heap was constructed in the first place, it may not be optimal for the row-after-row table access that is the most typical use case.

This method rebuilds the heap by taking elements in table read order (by rows, and columns) and puts them on a new heap.

For best squential read performance, you should defragment all tables that have been built column-by-column before writing them to a FITS file. The only time defragmentation is really not needed is if the table was built row-by-row, with no modifications to variable-length content after the fact.

Overrides:

defragment in class BinaryTable

Returns:

the number of bytes by which the heap has shrunk as a result of defragmentation.

Throws:

FitsException - if there was an error accessing the heap or the main data table comntaining the heap locators. In case of an error the table content may be left in a damaged state.

See Also:

• BinaryTable.compact()
• BinaryTable.setElement(int, int, Object)
• BinaryTable.addColumn(Object)
• BinaryTable.deleteColumns(int, int)
• BinaryTable.setColumn(int, Object)

fillHeader

public void fillHeader(Header h)
                throws FitsException

Overrides:

fillHeader in class BinaryTable

Throws:

FitsException

prepareUncompressedData

public void prepareUncompressedData(ColumnTable<?> data)
                             throws FitsException

Deprecated.

(for internal use) This should only be called by CompressedTableHDU, and its visibility will be reduced accordingly in the future, not to mention that it should take a BinaryTable as its argument.

Parameters:

data - The original (uncompressed) table data.

Throws:

FitsException