Package uk.ac.starlink.table

Class OnceRowPipe

  • All Implemented Interfaces:
    java.io.Closeable, java.lang.AutoCloseable, RowData, RowPipe, RowSequence, TableSink, uk.ac.starlink.util.Sequence
    public class OnceRowPipe
extends java.lang.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 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

      All Methods Instance Methods Concrete Methods 
      Modifier and Type Method 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​(java.lang.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.
      java.lang.Object getCell​(int icol)
      Returns the contents of a cell in the current row.
      java.lang.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​(java.io.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​(java.io.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​(java.lang.Object[] row)
               throws java.io.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:
        java.io.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

      • next

        public boolean next()
             throws java.io.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 uk.ac.starlink.util.Sequence
        Returns:
        true iff this sequence has been advanced to the next row
        Throws:
        java.io.IOException - if there is some error

      • getRow

        public java.lang.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 java.lang.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 java.lang.AutoCloseable
        Specified by:
        close in interface java.io.Closeable
        Specified by:
        close in interface RowSequence