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/*
 * Copyright (c) 1998-2018 John Caron and University Corporation for Atmospheric Research/Unidata
 * See LICENSE for license information.
 */
package ucar.nc2.iosp.hdf5;

import ucar.ma2.DataType;
import ucar.ma2.Section;
import ucar.nc2.iosp.LayoutTiled;
import ucar.nc2.iosp.Layout;
import java.io.IOException;

/**
 * Iterator to read/write subsets of an array.
 * This calculates byte offsets for HD5 chunked datasets.
 * Assumes that the data is stored in chunks, indexed by a Btree.
 * for unfiltered data only
 *
 * @author caron
 */
public class H5tiledLayout implements Layout {
  private LayoutTiled delegate;

  private Section want;
  private int[] chunkSize; // from the StorageLayout message (exclude the elemSize)
  private int elemSize; // last dimension of the StorageLayout message

  private boolean debug;

  /**
   * Constructor.
   * This is for HDF5 chunked data storage. The data is read by chunk, for efficency.
   *
   * @param vinfo the vinfo object for this variable
   * @param dtype type of data. may be different from v2.
   * @param wantSection the wanted section of data, contains a List of Range objects, must be complete
   * @throws java.io.IOException on io error
   */
  public H5tiledLayout(H5header.Vinfo vinfo, DataType dtype, Section wantSection) throws IOException {
    assert vinfo.isChunked;
    assert vinfo.btree != null;

    // we have to translate the want section into the same rank as the storageSize, in order to be able to call
    // Section.intersect(). It appears that storageSize (actually msl.chunkSize) may have an extra dimension, relative
    // to the Variable.
    if ((dtype == DataType.CHAR) && (wantSection.getRank() < vinfo.storageSize.length)) {
      this.want = Section.builder().appendRanges(wantSection.getRanges()).appendRange(1).build();
    } else {
      this.want = wantSection;
    }

    // one less chunk dimension, except in the case of char
    int nChunkDims = (dtype == DataType.CHAR) ? vinfo.storageSize.length : vinfo.storageSize.length - 1;
    this.chunkSize = new int[nChunkDims];
    System.arraycopy(vinfo.storageSize, 0, chunkSize, 0, nChunkDims);

    this.elemSize = vinfo.storageSize[vinfo.storageSize.length - 1]; // last one is always the elements size
    if (debug)
      System.out.println(" H5tiledLayout: " + this);

    // create the data chunk iterator
    LayoutTiled.DataChunkIterator iter = vinfo.btree.getDataChunkIteratorNoFilter(this.want, nChunkDims);
    delegate = new LayoutTiled(iter, chunkSize, elemSize, this.want);
  }

  public long getTotalNelems() {
    return delegate.getTotalNelems();
  }

  public int getElemSize() {
    return delegate.getElemSize();
  }

  public boolean hasNext() {
    return delegate.hasNext();
  }

  public Chunk next() {
    return delegate.next();
  }

  public String toString() {
    StringBuilder sbuff = new StringBuilder();
    sbuff.append("want=").append(want).append("; ");
    sbuff.append("chunkSize=[");
    for (int i = 0; i < chunkSize.length; i++) {
      if (i > 0)
        sbuff.append(",");
      sbuff.append(chunkSize[i]);
    }
    sbuff.append("] totalNelems=").append(getTotalNelems());
    sbuff.append(" elemSize=").append(elemSize);
    return sbuff.toString();
  }


}