uk.ac.starlink.table

Class OnceRowPipe

java.lang.Object

uk.ac.starlink.table.OnceRowPipe

All Implemented Interfaces:

Closeable, AutoCloseable, RowData, RowPipe, RowSequence, TableSink, Sequence

public class OnceRowPipe
extends Object
implements RowPipe, RowSequence

Streaming RowPipe implementation which provides a one-shot table. The returned table is unusual in that it can only return a RowSequence once. This violates the normal rules of the StarTable interface. Any calls beyond the first to waitForStarTable().getRowSequence() will throw a UnrepeatableSequenceException.

Since:

10 Feb 2005

Author:

Mark Taylor (Starlink)

Constructor Summary

Constructors

Constructor and Description
OnceRowPipe() Constructs a new streaming row store with a default buffer size.
OnceRowPipe(int queueSize) Constructs a new streaming row store with a given buffer size.

Method Summary

Modifier and Type	Method and Description
void	acceptMetadata(StarTable meta) Takes delivery of a row-less StarTable object which defines the metadata of the table to be transmitted.
void	acceptRow(Object[] row) Takes delivery of one row of data.
void	close() Indicates that this sequence will not be required any more.
void	endRows() Signals that there are no more rows to be transmitted.
Object	getCell(int icol) Returns the contents of a cell in the current row.
Object[]	getRow() Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table.
boolean	next() Attempts to advance the current row to the next one.
void	setError(IOException error) May be called by the writing stream to set an I/O error on the pipe.
StarTable	waitForStarTable() Returns a non-random table whose first call to getRowSequence will return a sequence that steps through the same rows which are being written to this sink.

Methods inherited from class java.lang.Object

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

Constructor Detail

OnceRowPipe

public OnceRowPipe()

Constructs a new streaming row store with a default buffer size.

OnceRowPipe

public OnceRowPipe(int queueSize)

Constructs a new streaming row store with a given buffer size.

Parameters:

queueSize - the maximum number of rows buffered between write and read before acceptRow will block

Method Detail

setError

public void setError(IOException error)

Description copied from interface: RowPipe

May be called by the writing stream to set an I/O error on the pipe. This error should be passed on to the reading end by throwing an error with e as its cause from one of the read methods. If an error has already been set by a previous call of this method, this has no effect (only the first error is set).

Specified by:

setError in interface RowPipe

Parameters:

error - exception to pass to readers

acceptMetadata

public void acceptMetadata(StarTable meta)

Description copied from interface: TableSink

Takes delivery of a row-less StarTable object which defines the metadata of the table to be transmitted. If the number of rows that will be transmitted via subsequent calls to acceptRow is known, this value should be made available as the row count of meta (StarTable.getRowCount()); if it is not known, the row count should be -1. However, this object should not attempt to read any of meta's cell data.

The data to be transmitted in subsequent calls of acceptRow must match the metadata transmitted in this call in the same way that rows of a StarTable must match its own metadata (number and content clases of columns etc). If this sink cannot dispose of a table corresponding to meta then it may throw a TableFormatException - this may be the case if for instance meta has columns with types that this sink can't deal with.

Specified by:

acceptMetadata in interface TableSink

Parameters:

meta - table metadata object

acceptRow

public void acceptRow(Object[] row)
               throws IOException

Description copied from interface: TableSink

Takes delivery of one row of data. row is an array of objects comprising the contents of one row of the table being transmitted. The number and classes of the elements of row are described by the metadata object previously accepted.

Specified by:

acceptRow in interface TableSink

Parameters:

row - table data row

Throws:

IOException

endRows

public void endRows()

Description copied from interface: TableSink

Signals that there are no more rows to be transmitted.

Specified by:

endRows in interface TableSink

waitForStarTable

public StarTable waitForStarTable()
                           throws IOException

Returns a non-random table whose first call to getRowSequence will return a sequence that steps through the same rows which are being written to this sink. The getRowSequence method can only be called once; any subsequent attempts to call it will result in a UnrepeatableSequenceException. This method will block until acceptMetadata(uk.ac.starlink.table.StarTable) has been called.

Specified by:

waitForStarTable in interface RowPipe

Returns:

one-shot streaming sequential table

Throws:

IOException - if one has previously been set using setError(java.io.IOException)

next

public boolean next()
             throws IOException

Description copied from interface: RowSequence

Attempts to advance the current row to the next one. If true is returned the attempt has been successful, and if false is returned there are no more rows in this sequence. Since the initial position of a RowSequence is before the first row, this method must be called before current row data can be accessed using the RowSequence.getCell(int) or RowSequence.getRow() methods.

Specified by:

next in interface RowSequence

Specified by:

next in interface Sequence

Returns:

true iff this sequence has been advanced to the next row

Throws:

IOException - if there is some error

getRow

public Object[] getRow()

Description copied from interface: RowSequence

Returns the contents of the current table row, as an array with the same number of elements as there are columns in this table. An unchecked exception will be thrown if there is no current row (next has not yet been called).

Specified by:

getRow in interface RowData

Specified by:

getRow in interface RowSequence

Returns:

an array of the objects in each cell in row irow

getCell

public Object getCell(int icol)

Description copied from interface: RowSequence

Returns the contents of a cell in the current row. The class of the returned object should be the same as, or a subclass of, the class returned by getColumnInfo(icol).getContentClass(). An unchecked exception will be thrown if there is no current row (next has not yet been called).

Specified by:

getCell in interface RowData

Specified by:

getCell in interface RowSequence

Parameters:

icol - column index

Returns:

the contents of cell icol in the current row

close

public void close()

Description copied from interface: RowSequence

Indicates that this sequence will not be required any more. This should release resources associated with this object. The effect of calling any of the other methods following a close is undefined.

Specified by:

close in interface Closeable

Specified by:

close in interface AutoCloseable

Specified by:

close in interface RowSequence