uk.ac.starlink.ttools.calc

Class CacheRowPipe

java.lang.Object

uk.ac.starlink.ttools.calc.CacheRowPipe

All Implemented Interfaces:

RowPipe, TableSink

public class CacheRowPipe
extends Object
implements RowPipe

RowPipe implementation which caches the data to provide a random-access StarTable.

The current implementation simply delegates to a OnceRowPipe and caches the result before returning it from waitForStarTable. This is crude, and means that the output rows don't start to come until all the input rows have been written to the pipe (so there's not much point using a pipe). A future implementation should get smarter with threads to improve this.

Since:

14 Oct 2011

Author:

Mark Taylor

Constructor Summary

Constructors

Constructor and Description
CacheRowPipe() Constructor.

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	endRows() Signals that there are no more rows to be transmitted.
void	setError(IOException err) May be called by the writing stream to set an I/O error on the pipe.
StarTable	waitForStarTable() Returns a multiply-readable random access table.

Methods inherited from class java.lang.Object

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

Constructor Detail

CacheRowPipe

public CacheRowPipe()

Constructor.

Method Detail

acceptMetadata

public void acceptMetadata(StarTable meta)
                    throws TableFormatException

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

Throws:

TableFormatException - if this sink cannot accept table rows matching the given metadata

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()
             throws IOException

Description copied from interface: TableSink

Signals that there are no more rows to be transmitted.

Specified by:

endRows in interface TableSink

Throws:

IOException

setError

public void setError(IOException err)

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:

err - exception to pass to readers

waitForStarTable

public StarTable waitForStarTable()
                           throws IOException

Returns a multiply-readable random access table.

Specified by:

waitForStarTable in interface RowPipe

Returns:

random access, multiply readable table with the same content as the rows accepted by this pipe

Throws:

IOException