uk.ac.starlink.table.formats

Class StreamStarTable

java.lang.Object

uk.ac.starlink.table.AbstractStarTable

uk.ac.starlink.table.formats.StreamStarTable

All Implemented Interfaces:

java.io.Closeable, java.lang.AutoCloseable, StarTable

Direct Known Subclasses:

AsciiStarTable, CsvStarTable

public abstract class StreamStarTable
extends AbstractStarTable

Abstract superclass for tables which reads a stream of characters to obtain the row data and metadata. Since metadata is typically scarce in such tables, the strategy is to make one pass through the data attempting to work out column types etc at table initialisation time, and to make a further pass through for each required RowSequence, using the metadata obtained earlier.

Since:

21 Sep 2004

See Also:

RowEvaluator

Field Summary

Fields

Modifier and Type	Field and Description
protected static char	END Char representation of -1 (as returned end-of-stream read)

Constructor Summary

Constructors

Modifier	Constructor and Description
protected	StreamStarTable() Constructor.

Method Summary

Modifier and Type	Method and Description
int	getColumnCount() Returns the number of columns in this table.
ColumnInfo	getColumnInfo(int icol) Returns the object describing the data in a given column.
protected java.io.PushbackInputStream	getInputStream() Convenience method which returns a buffered pushback stream based on this table's data source.
long	getRowCount() Returns the number of rows in this table, if known.
RowSequence	getRowSequence() Returns an object which can iterate over all the rows in the table sequentially.
protected void	init(DataSource datsrc) Initialises the table from the input stream.
protected abstract RowEvaluator.Metadata	obtainMetadata() Obtains column metadata for this table, probably by reading through the rows once and using a RowEvaluator.
protected abstract java.util.List<java.lang.String>	readRow(java.io.PushbackInputStream in) Reads the next row of data from a given stream.

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

checkedLongToInt, close, getCell, getColumnAuxDataInfos, getName, getParameters, getRow, getRowAccess, getRowSplittable, getURL, isRandom, setName, setParameters, setURL

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.StarTable

getParameterByName, setParameter

Field Detail

END

protected static final char END

Char representation of -1 (as returned end-of-stream read)

See Also:

Constant Field Values

Constructor Detail

StreamStarTable

protected StreamStarTable()

Constructor. This doesn't perform any processing; you must call init(uk.ac.starlink.util.DataSource) before doing anything with the constructed table. It is arranged this way so that the initialisation is able to call overridden methods in subclasses, which is a Bad thing to do from a constructor.

Method Detail

init

protected void init(DataSource datsrc)
             throws TableFormatException,
                    java.io.IOException

Initialises the table from the input stream. This method calls obtainMetadata(), which probably reads through some or all of the stream.

Parameters:

datsrc - data source from which the stream can be obtained

Throws:

TableFormatException

java.io.IOException

getColumnCount

public int getColumnCount()

Description copied from interface: StarTable

Returns the number of columns in this table.

Specified by:

getColumnCount in interface StarTable

Specified by:

getColumnCount in class AbstractStarTable

Returns:

the number of columns

getRowCount

public long getRowCount()

Description copied from interface: StarTable

Returns the number of rows in this table, if known. If the number of rows cannot be (easily) determined, a value of -1 will be returned.

Specified by:

getRowCount in interface StarTable

Specified by:

getRowCount in class AbstractStarTable

Returns:

the number of rows, or -1

getColumnInfo

public ColumnInfo getColumnInfo(int icol)

Description copied from interface: StarTable

Returns the object describing the data in a given column.

Specified by:

getColumnInfo in interface StarTable

Specified by:

getColumnInfo in class AbstractStarTable

Parameters:

icol - the column for which header information is required

Returns:

a ValueInfo object for column icol

getRowSequence

public RowSequence getRowSequence()
                           throws java.io.IOException

Description copied from interface: StarTable

Returns an object which can iterate over all the rows in the table sequentially. Each such returned object is safe for use within a single thread, but not in general from multiple threads concurrently.

Specified by:

getRowSequence in interface StarTable

Specified by:

getRowSequence in class AbstractStarTable

Returns:

new RowSequence

Throws:

java.io.IOException - if there is an error providing access

getInputStream

protected java.io.PushbackInputStream getInputStream()
                                              throws java.io.IOException

Convenience method which returns a buffered pushback stream based on this table's data source.

Returns:

input stream containing source data

Throws:

java.io.IOException

obtainMetadata

protected abstract RowEvaluator.Metadata obtainMetadata()
                                                 throws TableFormatException,
                                                        java.io.IOException

Obtains column metadata for this table, probably by reading through the rows once and using a RowEvaluator.

Returns:

information about the table represented by the character stream

Throws:

TableFormatException - if the data doesn't represent this kind of table

java.io.IOException - if I/O error is encountered

readRow

protected abstract java.util.List<java.lang.String> readRow(java.io.PushbackInputStream in)
                                                     throws TableFormatException,
                                                            java.io.IOException

Reads the next row of data from a given stream. Ignorable rows are skipped; comments may be stashed away.

Parameters:

in - input stream

Returns:

list of Strings one for each cell in the row, or null for end of stream

Throws:

TableFormatException - if the data doesn't represent this kind of table

java.io.IOException - if I/O error is encountered