uk.ac.starlink.ttools.example
Class AllWiseTableBuilder

java.lang.Object
  extended by uk.ac.starlink.ttools.example.AllWiseTableBuilder
All Implemented Interfaces:
TableBuilder
Direct Known Subclasses:
AllWiseTableBuilder.Count, AllWiseTableBuilder.NoCount

public class AllWiseTableBuilder
extends Object
implements TableBuilder

TableBuilder implementation for the ASCII files comprising the AllWise data release. At time of writing these files are available from http://irsadist.ipac.caltech.edu/wise-allwise/. The files are formatted as pipe-separated ASCII, and optionally compressed. Note that reading seems to be considerably faster for the gzip than for the bzip2 form of the input files (though the gzip ones are a bit bigger).

For FITS output (though not colfits) two passes through the input ASCII file are required, the first one (much faster) just to count the rows. There are therefore two variants of this input handler, one which does a row count and one which does not. If the row count is known, it would be possible to adapt this handler so you tell it the row count up front and only one pass is required.

Since:
6 Feb 2014
Author:
Mark Taylor

Nested Class Summary
static class AllWiseTableBuilder.Count
          Input handler which reads AllWise ASCII files and does count the rows first.
static class AllWiseTableBuilder.NoCount
          Input handler which reads AllWise ASCII files and does not count the rows first.
 
Constructor Summary
AllWiseTableBuilder()
          Default mode constructor.
AllWiseTableBuilder(String name, boolean preCount)
          Configurable constructor.
 
Method Summary
 boolean canImport(DataFlavor flavor)
          Indicates whether this builder is able to turn a resource of media type indicated by flavor into a table.
static long countLines(DataSource datsrc)
          Counts the lines in the ASCII file at the given location.
 String getFormatName()
          Returns the name of the format which can be read by this handler.
 StarTable makeStarTable(DataSource datsrc, boolean wantRandom, StoragePolicy storagePolicy)
          Constructs a StarTable based on a given DataSource.
 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 java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

AllWiseTableBuilder

public AllWiseTableBuilder()
Default mode constructor.


AllWiseTableBuilder

public AllWiseTableBuilder(String name,
                           boolean preCount)
Configurable constructor.

Parameters:
name - handler name
preCount - true to return a table that knows its row count
Method Detail

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

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

makeStarTable

public StarTable makeStarTable(DataSource datsrc,
                               boolean wantRandom,
                               StoragePolicy storagePolicy)
                        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
storagePolicy - 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

streamStarTable

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

countLines

public static long countLines(DataSource datsrc)
                       throws IOException
Counts the lines in the ASCII file at the given location.

Parameters:
datsrc - data source
Returns:
number of '\n'-terminated lines in the file
Throws:
IOException


Copyright © 2015 Central Laboratory of the Research Councils. All Rights Reserved.