public class ColFitsPlusTableBuilder extends java.lang.Object implements TableBuilder
TableBuilder
interface which reads
tables stored in column-oriented FITS binary table format.
The table data is stored in a BINTABLE extension which has a single row;
each cell in this row contains the data for an entire column of the
represented table. The primary HDU contains a byte[] array giving
the table metadata as a VOTable, as for FitsPlusTableBuilder
.
If the VOTMETA card in the primary HDU does not have the value T,
the VOTable metadata array is ignored.
This rather specialised format may provide good performance for certain operations on very large, especially very wide, tables. Although it is FITS and can therefore be used in principle for data interchange, in practice most non-STIL processors are unlikely to be able to do much useful with it.
Constructor and Description |
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ColFitsPlusTableBuilder()
Default constructor.
|
ColFitsPlusTableBuilder(WideFits wide)
Constructor.
|
Modifier and Type | Method and Description |
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boolean |
canImport(java.awt.datatransfer.DataFlavor flavor)
Indicates whether this builder is able to turn a resource of
media type indicated by
flavor into a table. |
java.lang.String |
getFormatName()
Returns the name of the format which can be read by this handler.
|
static boolean |
isMagic(byte[] buffer)
Tests whether a given buffer contains bytes which might be the
first few bytes of a FitsPlus table.
|
boolean |
looksLikeFile(java.lang.String location)
Indicates whether the given location string is of a familiar form
for this builder.
|
StarTable |
makeStarTable(DataSource datsrc,
boolean wantRandom,
StoragePolicy policy)
Constructs a
StarTable based on a given DataSource . |
void |
streamStarTable(java.io.InputStream in,
TableSink sink,
java.lang.String pos)
Reads a table from an input stream and writes it a row at a time
to a sink.
|
public ColFitsPlusTableBuilder()
public ColFitsPlusTableBuilder(WideFits wide)
wide
- convention for representing extended columns;
use null to avoid use of extended columnspublic java.lang.String getFormatName()
TableBuilder
getFormatName
in interface TableBuilder
public boolean looksLikeFile(java.lang.String location)
TableBuilder
true
if there is
a good chance that a file with the given location
can be interpreted by this reader, for instance if it has a
suitable file extension.
This method may be used to guess, on a best-efforts basis, whether this builder is suitable for reading a file from a given location. Attempts may still be made to read inputs for which this method returns false. It is less important for builders that can recognise files by magic number, which is generally preferable to using filenames.
looksLikeFile
in interface TableBuilder
location
- the location string, such as a filename or URL
(not null)public void streamStarTable(java.io.InputStream in, TableSink sink, java.lang.String pos) throws TableFormatException
TableBuilder
TableFormatException
.
The input stream should be prepared for use prior to calling
this method, so implementations should not in general attempt to
decompress or buffer istrm
.
streamStarTable
in interface TableBuilder
in
- input stream containing table datasink
- destination of the tablepos
- position identifier describing the location of the
table within the stream;
see DataSource.getPosition()
(may be null)TableFormatException
- if the table can't be streamed or
the data is malformedpublic boolean canImport(java.awt.datatransfer.DataFlavor flavor)
TableBuilder
flavor
into a table.
It should return true
if it thinks that its
TableBuilder.streamStarTable(java.io.InputStream, uk.ac.starlink.table.TableSink, java.lang.String)
method stands a reasonable chance of
successfully constructing a StarTable
from a
DataSource
whose input stream is described by the
DataFlavor
flavor
.
It will typically make this determination based on the flavor's
MIME type.
This method should only return true
if the flavor looks like
it is targeted at this builder; for instance a builder which
uses a text-based format should return false for a
flavor which indicates a MIME type of text/plain
.
This method is used in supporting drag and drop functionality
(see StarTableFactory.canImport(java.awt.datatransfer.DataFlavor[])
).
canImport
in interface TableBuilder
flavor
- the DataFlavor whose suitability as stream input
is to be assessedtrue
iff this builder reckons it stands a good
chance of turning a stream of type flavor
into a
StarTable
public StarTable makeStarTable(DataSource datsrc, boolean wantRandom, StoragePolicy policy) throws java.io.IOException
TableBuilder
StarTable
based on a given DataSource
.
If the source is not recognised or this builder does not know
how to construct a table from it, then a
TableFormatException
should be thrown.
If this builder thinks it should be able to handle the source
but an error occurs during processing, an IOException
can be thrown.
The wantRandom
parameter is used to indicate whether,
ideally, a random-access table should be returned. There is no
requirement for the builder to honour this request, but if
it knows how to make both random and non-random tables, it can
use this flag to decide which to return.
Note: the presence of the wantRandom
parameter is somewhat misleading. TableBuilder implementations
usually should, and do, ignore it (it would be removed from the
interface if it were not for backward compatibility issues).
Regardless of the value of this parameter, implementations should
return a random-access table only if it is easy for them to do so;
in particular they should not use the supplied
storagePolicy
, or any other resource-expensive measure,
to randomise a sequential table just because the
wantRandom
parameter is true.
makeStarTable
in interface TableBuilder
datsrc
- the DataSource containing the table resourcewantRandom
- whether, preferentially, a random access table
should be returnedpolicy
- a StoragePolicy object which may be used to
supply scratch storage if the builder needs itdatsrc
TableFormatException
- if the table is not of a kind that
can be handled by this handlerjava.io.IOException
- if an unexpected I/O error occurs during processingpublic static boolean isMagic(byte[] buffer)
SIMPLE = T BITPIX = 8 NAXIS = 1 NAXIS1 = ??? COLFITS = T VOTMETA = T
buffer
- byte buffer containing leading few bytes of data