uk.ac.starlink.votable

Class VOTableFitsTableWriter

java.lang.Object

uk.ac.starlink.table.StreamStarTableWriter

uk.ac.starlink.fits.AbstractFitsTableWriter

uk.ac.starlink.votable.VOTableFitsTableWriter

All Implemented Interfaces:

MultiStarTableWriter, StarTableWriter

Direct Known Subclasses:

ColFitsPlusTableWriter, FitsPlusTableWriter

public abstract class VOTableFitsTableWriter
extends AbstractFitsTableWriter

TableWriter which writes table data into the first extension of a FITS file, Unlike FitsTableWriter however, the primary extension is not left contentless, instead it gets the text of a DATA-less VOTable written into it. This VOTable describes the metadata of the table. Tables stored using this (non-standard) mechanism have all the rich metadata associated with VOTables, and benefit from the compactness of FITS tables, withouth the considerable disadvantage of being split into two files.

Since:

26 Aug 2004

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	VOTableFitsTableWriter(java.lang.String formatName) Constructor.

Method Summary

Modifier and Type	Method and Description
protected abstract void	customisePrimaryHeader(nom.tam.fits.Header hdr) Hook for adding custom entries to the FITS header which is written to the primary HDU.
boolean	isMagic(byte[] buffer) Determines whether a given byte buffer looks like it contains the start of a primary header written by this writer.
protected boolean	isMagic(int icard, java.lang.String key, java.lang.String value) Tests a header card to see if it looks like part of the magic number for the format written by this handler.
void	setAllowSignedByte(boolean allowSignedByte) Configures how Byte-valued columns are written.
void	setVotableVersion(VOTableVersion votVersion) Sets the version of the VOTable standard to use for encoding metadata in the primary HDU.
void	writeStarTables(TableSequence tableSeq, java.io.OutputStream out) Writes tables.

Methods inherited from class uk.ac.starlink.fits.AbstractFitsTableWriter

addMetadata, createSerializer, getAllowSignedByte, getAllowZeroLengthString, getConfig, getCurrentDate, getFormatName, getMimeType, getPadCharacter, getWide, getWriteDate, setAllowZeroLengthString, setFormatName, setPadCharacter, setWide, setWriteDate, writePrimaryHDU, writeStarTable, writeStarTables, writeTableHDU

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

writeStarTable, writeStarTable

Methods inherited from class java.lang.Object

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

Methods inherited from interface uk.ac.starlink.table.StarTableWriter

looksLikeFile, writeStarTable

Constructor Detail

VOTableFitsTableWriter

protected VOTableFitsTableWriter(java.lang.String formatName)

Constructor.

Parameters:

formatName - handler format name

Method Detail

setAllowSignedByte

public void setAllowSignedByte(boolean allowSignedByte)

Description copied from class: AbstractFitsTableWriter

Configures how Byte-valued columns are written. This is a bit fiddly, since java bytes are signed, but FITS 8-bit integers are unsigned. If true, they are written as FITS unsigned 8-bit integers with an offset, as discussed in the FITS standard (TFORMn='B', TZERO=-128). If false, they are written as FITS signed 16-bit integers.

Overrides:

setAllowSignedByte in class AbstractFitsTableWriter

Parameters:

allowSignedByte - true to write offset bytes, false to write shorts

writeStarTables

public void writeStarTables(TableSequence tableSeq,
                            java.io.OutputStream out)
                     throws java.io.IOException

Description copied from class: AbstractFitsTableWriter

Writes tables. Calls AbstractFitsTableWriter.writePrimaryHDU(java.io.DataOutput) to write the primary HDU. Subclasses which want to put something related to the input tables into the primary HDU will need to override this method (writeStarTables).

Specified by:

writeStarTables in interface MultiStarTableWriter

Overrides:

writeStarTables in class AbstractFitsTableWriter

Parameters:

tableSeq - sequence of tables to write

out - destination stream

Throws:

java.io.IOException

setVotableVersion

public void setVotableVersion(VOTableVersion votVersion)

Sets the version of the VOTable standard to use for encoding metadata in the primary HDU.

Parameters:

votVersion - VOTable version to use

customisePrimaryHeader

protected abstract void customisePrimaryHeader(nom.tam.fits.Header hdr)
                                        throws nom.tam.fits.HeaderCardException

Hook for adding custom entries to the FITS header which is written to the primary HDU. This is called just after the required cards (SIMPLE, BITPIX, NAXIS, NAXIS1 ) are added and just before the EXTEND card.

Parameters:

hdr - header

Throws:

nom.tam.fits.HeaderCardException

isMagic

public boolean isMagic(byte[] buffer)

Determines whether a given byte buffer looks like it contains the start of a primary header written by this writer. Calls the protected isMagic(int,java.lang.String,java.lang.String) method.

Parameters:

buffer - start of a file

Returns:

true iff buffer looks like it contains a file written by this handler

isMagic

protected boolean isMagic(int icard,
                          java.lang.String key,
                          java.lang.String value)

Tests a header card to see if it looks like part of the magic number for the format written by this handler. The VOTableFitsTableWriter implementation tests that the first four cards read:

    SIMPLE = T
    BITPIX = 8
    NAXIS  = 1
    NAXIS1 = ???
 

Subclasses may override this to add tests for later cards (as written in customisePrimaryHeader(nom.tam.fits.Header)).

Parameters:

icard - 0-based card index

key - card name

value - card value

Returns:

true iff the presented card is one that could have been written by this writer