ucar.nc2.iosp.Layout Maven / Gradle / Ivy

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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 java.io.IOException;

/**
 * Iterator to read/write subsets of a multidimensional array, finding the contiguous chunks.
 * The iteration is monotonic in both src and dest positions.
 * 
 * Example for Integers:
 *   int[] read( Layout index, int[] src) {
    int[] dest = new int[index.getTotalNelems()];
    while (index.hasNext()) {
      Layout.Chunk chunk = index.next();
      System.arraycopy(src, chunk.getSrcElem(), dest, chunk.getDestElem(), chunk.getNelems());
    }
    return dest;
  }

  int[] read( Layout index, RandomAccessFile raf) {
    int[] dest = new int[index.getTotalNelems()];
    while (index.hasNext()) {
      Layout.Chunk chunk = index.next();
      raf.seek( chunk.getSrcPos());
      raf.readInt(dest, chunk.getDestElem(), chunk.getNelems());
    }
    return dest;
  }

   // note src and dest misnamed
    void write( Layout index, int[] src, RandomAccessFile raf) {
      while (index.hasNext()) {
        Layout.Chunk chunk = index.next();
        raf.seek ( chunk.getSrcPos());
        for (int k=0; k
 *
 * @author caron
 * @since Jan 2, 2008
 */

public interface Layout {

  /**
   * Get total number of elements in the wanted subset.
   *
   * @return total number of elements in the wanted subset.
   */
  public long getTotalNelems();

  /**
   * Get size of each element in bytes.
   *
   * @return size of each element in bytes.
   */
  public int getElemSize();

  /**
   * Is there more to do
   *
   * @return true if theres more to do
   */
  public boolean hasNext();

  /**
   * Get the next chunk
   *
   * @return next chunk, or null if !hasNext()
   * @throws java.io.IOException on i/o error
   */
  public Chunk next() throws IOException;

  /**
   * A chunk of data that is contiguous in both the source and destination.
   * Read nelems from src at filePos, store in destination at startElem.
   * (or) Write nelems to file at filePos, from array at startElem.
   */
  public interface Chunk {

    /**
     * Get the position in source where to read or write: "file position"
     * @return position as a byte count into the source, eg a file
     */
    public long getSrcPos();

    /**
     * Get number of elements to transfer contiguously (Note: elements, not bytes)
     * @return number of elements to transfer
     */
    public int getNelems();

    /**
     * Get starting element position as a 1D element index into the destination, eg the requested array with shape "wantSection".
     * @return starting element in the array (Note: elements, not bytes)
     */
    public long getDestElem();
  }
}