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The NetCDF-Java Library is a Java interface to NetCDF files, as well as to many other types of scientific data formats.
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/*
 * Copyright 1998-2014 University Corporation for Atmospheric Research/Unidata
 *
 *   Portions of this software were developed by the Unidata Program at the
 *   University Corporation for Atmospheric Research.
 *
 *   Access and use of this software shall impose the following obligations
 *   and understandings on the user. The user is granted the right, without
 *   any fee or cost, to use, copy, modify, alter, enhance and distribute
 *   this software, and any derivative works thereof, and its supporting
 *   documentation for any purpose whatsoever, provided that this entire
 *   notice appears in all copies of the software, derivative works and
 *   supporting documentation.  Further, UCAR requests that the user credit
 *   UCAR/Unidata in any publications that result from the use of this
 *   software or in any product that includes this software. The names UCAR
 *   and/or Unidata, however, may not be used in any advertising or publicity
 *   to endorse or promote any products or commercial entity unless specific
 *   written permission is obtained from UCAR/Unidata. The user also
 *   understands that UCAR/Unidata is not obligated to provide the user with
 *   any support, consulting, training or assistance of any kind with regard
 *   to the use, operation and performance of this software nor to provide
 *   the user with any updates, revisions, new versions or "bug fixes."
 *
 *   THIS SOFTWARE IS PROVIDED BY UCAR/UNIDATA "AS IS" AND ANY EXPRESS OR
 *   IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
 *   WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 *   DISCLAIMED. IN NO EVENT SHALL UCAR/UNIDATA BE LIABLE FOR ANY SPECIAL,
 *   INDIRECT OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING
 *   FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
 *   NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
 *   WITH THE ACCESS, USE OR PERFORMANCE OF THIS SOFTWARE.
 */

package ucar.nc2.iosp;

import ucar.ma2.*;
import ucar.nc2.ParsedSectionSpec;
import ucar.nc2.Structure;
import ucar.nc2.NetcdfFile;
import ucar.nc2.Variable;
import ucar.nc2.util.CancelTask;
import ucar.unidata.io.RandomAccessFile;
import ucar.unidata.util.Format;

import java.io.File;
import java.io.IOException;
import java.io.OutputStream;
import java.nio.channels.WritableByteChannel;
import java.util.Formatter;

/**
 * Abstract base class for IOSP implementations that provides default implementations
 * of readToByteChannel(...) and readSection(...).
 *
 * Implementations should make sure to handle the RandomAccessFile properly by
 * doing one of the following:
 *
 * 

 *    Write your own open(...) and close() methods that keep track of the
 *     RandomAccessFile, be sure to close the RandomAccessFile in your close()
 *     method.
 *    Write your own open(...) and close() methods that call the open(...)
 *     and close() methods defined here, use the "raf" variable also defined
 *     here.
 *    Don't write an open(...) or close() method, so that those defined
 *     here are used.
 * 
 *
 */
public abstract class AbstractIOServiceProvider implements IOServiceProvider {

  /**
   * Subclasses that use AbstractIOServiceProvider.open(...) or .close()
   * should use this (instead of their own private variable).
   */
  protected ucar.unidata.io.RandomAccessFile raf;

  @Override
  public void open( RandomAccessFile raf, NetcdfFile ncfile, CancelTask cancelTask ) throws IOException {
    this.raf = raf;
  }

  @Override
  public void close() throws java.io.IOException {
    if (raf != null)
      raf.close();
    raf = null;
  }

  // default implementation, reads into an Array, then writes to WritableByteChannel
  // subclasses should override if possible
  // LOOK DataOutputStream uses big-endian
  @Override
  public long readToByteChannel(ucar.nc2.Variable v2, Section section, WritableByteChannel channel)
          throws java.io.IOException, ucar.ma2.InvalidRangeException {

    Array data = readData(v2, section);
    return IospHelper.copyToByteChannel(data,  channel);
  }

  public long readToOutputStream(ucar.nc2.Variable v2, Section section, OutputStream out)
          throws java.io.IOException, ucar.ma2.InvalidRangeException {

    Array data = readData(v2, section);
    return IospHelper.copyToOutputStream(data,  out);
  }

  public long streamToByteChannel(ucar.nc2.Variable v2, Section section, WritableByteChannel channel)
      throws java.io.IOException, ucar.ma2.InvalidRangeException {

    Array data = readData(v2, section);
    return IospHelper.copyToByteChannel(data,  channel);
  }

  @Override
  public ucar.ma2.Array readSection(ParsedSectionSpec cer) throws IOException, InvalidRangeException {
    return IospHelper.readSection(cer);  //  IOSPs can optimize by overriding
  }

  @Override
  public StructureDataIterator getStructureIterator(Structure s, int bufferSize) throws java.io.IOException {
    return null;
  }

  @Override
  public Object sendIospMessage(Object message) {
    if (message == NetcdfFile.IOSP_MESSAGE_RANDOM_ACCESS_FILE) {
      return raf;
    }
    return null;
  }

  @Override
  public boolean syncExtend() throws IOException {
    return false;
  }

  /**
   * Get last modified date of underlying file. If changes, will be discarded.
   * @return a sequence number (typically file date), 0 if cannot change
   */
  public long getLastModified() {
    if (raf != null) {
      return raf.getLastModified();
    }
    return 0;
  }

  @Override
  public String toStringDebug(Object o) {
    return "";
  }

  @Override
  public String getDetailInfo() {
    if (raf == null) return "";
    try {
      Formatter fout = new Formatter();
      double size = raf.length() / (1000.0 * 1000.0);
      fout.format(" raf = %s%n", raf.getLocation());
      fout.format(" size= %d (%s Mb)%n%n", raf.length(), Format.dfrac(size, 3));
      return fout.toString();

    } catch (IOException e) {
      return e.getMessage();
    }
  }


  @Override
  public String getFileTypeVersion() {
    return "N/A";
  }

}