uk.ac.starlink.pds4

Class Pds4TableBuilder

java.lang.Object

uk.ac.starlink.table.formats.DocumentedTableBuilder

uk.ac.starlink.pds4.Pds4TableBuilder

All Implemented Interfaces:

Documented, DocumentedIOHandler, MultiTableBuilder, TableBuilder

public class Pds4TableBuilder
extends DocumentedTableBuilder
implements MultiTableBuilder

TableBuilder implementation for the NASA PDSv4 format.

Since:

24 Nov 2021

Author:

Mark Taylor

See Also:

https://pds.nasa.gov/datastandards/documents/

Constructor Summary

Constructors

Constructor and Description
Pds4TableBuilder() Constructor.

Method Summary

Modifier and Type	Method and Description
boolean	canImport(DataFlavor flavor) Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table.
boolean	canStream() No chance of streaming a format which stores the data in a different file.
boolean	docIncludesExample() Indicates whether the serialization of some (short) example table should be added to the user documentation for this handler.
boolean	getCheckMagic() Indicates whether handler will attempt to guess by looking at the file whether it is PDS4.
String	getFormatName() Returns the name of the format which can be read by this handler.
boolean	getObservationalOnly() Indicates whether only tables within File_Area_Observational elements of the PDS4 label are interpreted as StarTables.
String	getXmlDescription() Returns user-directed documentation in XML format.
static boolean	isMagic(byte[] intro) Determines whether a byte buffer contains what looks like the start of a PDS4 file.
StarTable	makeStarTable(DataSource datsrc, boolean wantRandom, StoragePolicy storage) Constructs a StarTable based on a given DataSource.
TableSequence	makeStarTables(DataSource datsrc, StoragePolicy storage) Constructs a sequence of StarTables based on a given DataSource.
void	setCheckMagic(boolean checkMagic) Sets whether the handler will attempt to guess by looking at the file whether it appears to be a PDS4 file before attempting to parse it as one.
void	setObservationalOnly(boolean observationalOnly) Sets whether only tables within File_Area_Observational elements of the PDS4 label are interpreted as StarTables.
void	streamStarTable(InputStream in, TableSink sink, String pos) Reads a table from an input stream and writes it a row at a time to a sink.

Methods inherited from class uk.ac.starlink.table.formats.DocumentedTableBuilder

getExtensions, looksLikeFile

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.TableBuilder

looksLikeFile

Methods inherited from interface uk.ac.starlink.table.formats.DocumentedIOHandler

matchesExtension, readText, toLink

Constructor Detail

Pds4TableBuilder

public Pds4TableBuilder()

Constructor.

Method Detail

getFormatName

public String getFormatName()

Description copied from interface: TableBuilder

Returns the name of the format which can be read by this handler. Matching against this string may be used by callers to identify or select this handler from a list.

Specified by:

getFormatName in interface TableBuilder

Returns:

one-word description of this handler's format

getXmlDescription

public String getXmlDescription()

Description copied from interface: Documented

Returns user-directed documentation in XML format.

The output should be a sequence of one or more <P> elements, using XHTML-like XML. Since rendering may be done in a number of contexts however, use of the full range of XHTML elements is discouraged. Where possible, the content should stick to simple markup such as the elements P, A, UL, OL, LI, DL, DT, DD EM, STRONG, I, B, CODE, TT, PRE.

Specified by:

getXmlDescription in interface Documented

Returns:

XML description of this object

docIncludesExample

public boolean docIncludesExample()

Description copied from interface: DocumentedIOHandler

Indicates whether the serialization of some (short) example table should be added to the user documentation for this handler. Binary formats, or instances for which the Documented.getXmlDescription() method already includes some example output, should return false.

Specified by:

docIncludesExample in interface DocumentedIOHandler

Returns:

true if the user documentation would benefit from the addition of an example serialization

canImport

public boolean canImport(DataFlavor flavor)

Description copied from interface: TableBuilder

Indicates whether this builder is able to turn a resource of media type indicated by 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[])).

Specified by:

canImport in interface TableBuilder

Parameters:

flavor - the DataFlavor whose suitability as stream input is to be assessed

Returns:

true iff this builder reckons it stands a good chance of turning a stream of type flavor into a StarTable

canStream

public boolean canStream()

No chance of streaming a format which stores the data in a different file.

Specified by:

canStream in class DocumentedTableBuilder

Returns:

true iff this handler can read from streams

setCheckMagic

@ConfigMethod(property="checkmagic",
              doc="<p>Determines whether an initial test is made to see whether\nthe file looks like PDS4 before attempting to read it as one.\nThe tests are ad-hoc and look for certain elements\nand namespaces that are expected to appear near the start of\na table-containing PDS4 file, but it\'s not bulletproof.\nSetting this true is generally a good idea\nto avoid attempting to parse non-PDS4 files,\nbut you can set it false to attempt to read an PDS4 file\nthat starts with the wrong sequence.\n</p>",
              example="false")
public void setCheckMagic(boolean checkMagic)

Sets whether the handler will attempt to guess by looking at the file whether it appears to be a PDS4 file before attempting to parse it as one. This is generally a good idea, since otherwise it will attempt to parse any old file as PDS4 which may consume resources (especially if it's a large XML file), but you can set it false to try to parse PDS4 files with unexpected first few bytes.

Parameters:

checkMagic - true to require magic number presence

getCheckMagic

public boolean getCheckMagic()

Indicates whether handler will attempt to guess by looking at the file whether it is PDS4.

Returns:

magic checking flag

setObservationalOnly

@ConfigMethod(property="observational",
              doc="<p>Determines whether only tables within a\n<code>&lt;File_Area_Observational&gt;</code> element\nof the PDS4 label should be included.\nIf true, only observational tables are found,\nif false, other tables will be found as well.\n</p>",
              example="true")
public void setObservationalOnly(boolean observationalOnly)

Sets whether only tables within File_Area_Observational elements of the PDS4 label are interpreted as StarTables.

Parameters:

observationalOnly - if true, only observational tables are found, if false, others may be found as well

getObservationalOnly

public boolean getObservationalOnly()

Indicates whether only tables within File_Area_Observational elements of the PDS4 label are interpreted as StarTables.

Returns:

observational-only flag

streamStarTable

public void streamStarTable(InputStream in,
                            TableSink sink,
                            String pos)
                     throws TableFormatException

Description copied from interface: TableBuilder

Reads a table from an input stream and writes it a row at a time to a sink. Not all implementations will be able to do this; for instance, extracting the table from the data may be a two-pass process. Implementations which are unable to perform this function should throw a 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.

Specified by:

streamStarTable in interface TableBuilder

Parameters:

in - input stream containing table data

sink - destination of the table

pos - position identifier describing the location of the table within the stream; see DataSource.getPosition() (may be null)

Throws:

TableFormatException - if the table can't be streamed or the data is malformed

makeStarTable

public StarTable makeStarTable(DataSource datsrc,
                               boolean wantRandom,
                               StoragePolicy storage)
                        throws IOException

Description copied from interface: TableBuilder

Constructs a 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.

Specified by:

makeStarTable in interface TableBuilder

Parameters:

datsrc - the DataSource containing the table resource

wantRandom - whether, preferentially, a random access table should be returned

storage - a StoragePolicy object which may be used to supply scratch storage if the builder needs it

Returns:

a StarTable made out of datsrc

Throws:

TableFormatException - if the table is not of a kind that can be handled by this handler

IOException - if an unexpected I/O error occurs during processing

makeStarTables

public TableSequence makeStarTables(DataSource datsrc,
                                    StoragePolicy storage)
                             throws IOException

Description copied from interface: MultiTableBuilder

Constructs a sequence of StarTables based on a given DataSource. If the source is not recognised or this object does not know how to make tables 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.

If the position of the data source is not null, then this method should return a sequence containing a single table, the one which would be returned by the makeStarTable method with that position.

Specified by:

makeStarTables in interface MultiTableBuilder

Parameters:

datsrc - the DataSource containing the table resource

storage - a StoragePolicy object which may be used to supply scratch storage if the builder needs it

Returns:

an array of StarTables read from datsrc

Throws:

TableFormatException - if the table is not of a kind that can be handled by this handler

IOException - if an unexpected I/O error occurs during processing

isMagic

public static boolean isMagic(byte[] intro)

Determines whether a byte buffer contains what looks like the start of a PDS4 file. Not bulletproof.

Parameters:

intro - first few bytes of file

Returns:

true if the intro looks like the start of a PDS4 file