Writing an IOSP for Netdf-Java version 4

Version 4.0 of Netcdf-Java has two new methods (in red), and one method has been removed. It also uses Section objects instead of List<Range>.

public interface ucar.nc2.IOServiceProvider {

  // Check if this is a valid file for this IOServiceProvider.
  public boolean isValidFile( ucar.unidata.io.RandomAccessFile raf) throws IOException;

  // Open existing file, and populate ncfile with it.
  public void open(ucar.unidata.io.RandomAccessFile raf, NetcdfFile ncfile, CancelTask cancelTask) throws IOException;

  // Read data from a top level Variable and return a memory resident Array.
  public ucar.ma2.Array readData(ucar.nc2.Variable v2, Section section) throws java.io.IOException, ucar.ma2.InvalidRangeException;

  // Read data from a top level Variable and send data to a WritableByteChannel.
  public long readData(ucar.nc2.Variable v2, Section section, WritableByteChannel channel)
         throws java.io.IOException, ucar.ma2.InvalidRangeException;

  // Read data from a Variable that is nested in one or more Structures.
  // If there are no Structures in the file, this will never be called.
  public ucar.ma2.Array readNestedData(ucar.nc2.Variable v2, Section section) throws IOException, ucar.ma2.InvalidRangeException;

  // Close the file.
  public void close() throws IOException;

  // Extend the file if needed in a way that is compatible with the current metadata.
  public boolean syncExtend() throws IOException;

  // Check if file has changed, and reread metadata if needed.
  public boolean sync() throws IOException;

  // A way to communicate arbitrary information to an iosp.
  public Object sendIospMessage( Object message);
  public void setSpecial( Object special);

  // print Debug info for this object.
  public String toStringDebug(Object o);

  // Show debug / underlying implementation details
  public String getDetailInfo();

}

A Section is a container for a List of Range objects:

 public class ucar.ma2.Section {
   public List<Range> getRanges();
   public int[] getOrigin();
   public int[] getShape();
   public int[] getStride();
   ...
 }

Its best to extend ucar.nc2.iosp.AbstractIOServiceProvider. In the simplest case, you only have to implement 4 methods.

public class Example extends AbstractIOServiceProvider {

  public boolean isValidFile(RandomAccessFile raf) throws IOException {}

  public void open(RandomAccessFile raf, NetcdfFile ncfile, CancelTask cancelTask) throws IOException {}

  public Array readData(Variable v2, Section wantSection) throws IOException, InvalidRangeException {}

  public void close() throws IOException {}
}

This document is maintained by John Caron and was last updated on Aug 3, 2007