cdm/src/main/java/ucar/nc2/iosp/hdf5/H5iosp.java
private Array readData(ucar.nc2.Variable v2, long dataPos, Section wantSection) throws IOException, InvalidRangeException {
    H5header.Vinfo vinfo = (H5header.Vinfo) v2.getSPobject();
    DataType dataType = v2.getDataType();
    Object data;
    Layout layout;

    if (vinfo.useFillValue) { // fill value only
      Object pa = IospHelper.makePrimitiveArray((int) wantSection.computeSize(), dataType, vinfo.getFillValue());
      if (dataType == DataType.CHAR)
        pa = IospHelper.convertByteToChar((byte[]) pa);
      return Array.factory(dataType, wantSection.getShape(), pa);
    }

    if (vinfo.mfp != null) { // filtered
      if (debugFilter) System.out.println("read variable filtered " + v2.getFullName() + " vinfo = " + vinfo);
      assert vinfo.isChunked;
      ByteOrder bo = (vinfo.typeInfo.endian == 0) ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN;
      layout = new H5tiledLayoutBB(v2, wantSection, raf, vinfo.mfp.getFilters(), bo);
      if (vinfo.typeInfo.isVString) {
        data = readFilteredStringData((LayoutBB) layout);
      } else{
        data = IospHelper.readDataFill((LayoutBB) layout, v2.getDataType(), vinfo.getFillValue());
      }

    } else { // normal case
      if (debug) System.out.println("read variable " + v2.getFullName() + " vinfo = " + vinfo);

      DataType readDtype = v2.getDataType();
      int elemSize = v2.getElementSize();
      Object fillValue = vinfo.getFillValue();
      int endian = vinfo.typeInfo.endian;

      // fill in the wantSection
      wantSection = Section.fill(wantSection, v2.getShape());

      if (vinfo.typeInfo.hdfType == 2) { // time
        readDtype = vinfo.mdt.timeType;
        elemSize = readDtype.getSize();
        fillValue = N3iosp.getFillValueDefault(readDtype);

      } else if (vinfo.typeInfo.hdfType == 8) { // enum
        H5header.TypeInfo baseInfo = vinfo.typeInfo.base;
        readDtype = baseInfo.dataType;
        elemSize = readDtype.getSize();
        fillValue = N3iosp.getFillValueDefault(readDtype);
        endian = baseInfo.endian;

      } else if (vinfo.typeInfo.hdfType == 9) { // vlen
        elemSize = vinfo.typeInfo.byteSize;
        endian = vinfo.typeInfo.endian;
        //wantSection = wantSection.removeVlen(); // remove vlen dimension
      }

      if (vinfo.isChunked) {
        layout = new H5tiledLayout((H5header.Vinfo) v2.getSPobject(), readDtype, wantSection);
      } else {
        layout = new LayoutRegular(dataPos, elemSize, v2.getShape(), wantSection);
      }
      data = readData(vinfo, v2, layout, readDtype, wantSection.getShape(), fillValue, endian);
    }

    if (data instanceof Array)
      return (Array) data;
    else if (dataType == DataType.STRUCTURE)
      return convertStructure((Structure) v2, layout, wantSection.getShape(), (byte[]) data);  // LOOK
    else
      return Array.factory(dataType, wantSection.getShape(), data);
  }
private Array readData(ucar.nc2.Variable v2, long dataPos, Section wantSection) throws IOException, InvalidRangeException {
    H5header.Vinfo vinfo = (H5header.Vinfo) v2.getSPobject();
    DataType dataType = v2.getDataType();
    Object data;
    Layout layout;

    if (vinfo.useFillValue) { // fill value only
      Object pa = IospHelper.makePrimitiveArray((int) wantSection.computeSize(), dataType, vinfo.getFillValue());
      if (dataType == DataType.CHAR)
        pa = IospHelper.convertByteToChar((byte[]) pa);
      return Array.factory(dataType, wantSection.getShape(), pa);
    }

    if (vinfo.mfp != null) { // filtered
      if (debugFilter) System.out.println("read variable filtered " + v2.getFullName() + " vinfo = " + vinfo);
      assert vinfo.isChunked;
      ByteOrder bo = (vinfo.typeInfo.endian == 0) ? ByteOrder.BIG_ENDIAN : ByteOrder.LITTLE_ENDIAN;
      layout = new H5tiledLayoutBB(v2, wantSection, raf, vinfo.mfp.getFilters(), bo);
      if (vinfo.typeInfo.isVString) {
        data = readFilteredStringData((LayoutBB) layout);
      } else{
        data = IospHelper.readDataFill((LayoutBB) layout, v2.getDataType(), vinfo.getFillValue());
      }

    } else { // normal case
      if (debug) System.out.println("read variable " + v2.getFullName() + " vinfo = " + vinfo);

      DataType readDtype = v2.getDataType();
      int elemSize = v2.getElementSize();
      Object fillValue = vinfo.getFillValue();
      int endian = vinfo.typeInfo.endian;

      // fill in the wantSection
      wantSection = Section.fill(wantSection, v2.getShape());

      if (vinfo.typeInfo.hdfType == 2) { // time
        readDtype = vinfo.mdt.timeType;
        elemSize = readDtype.getSize();
        fillValue = N3iosp.getFillValueDefault(readDtype);

      } else if (vinfo.typeInfo.hdfType == 8) { // enum
        H5header.TypeInfo baseInfo = vinfo.typeInfo.base;
        readDtype = baseInfo.dataType;
        elemSize = readDtype.getSize();
        fillValue = N3iosp.getFillValueDefault(readDtype);
        endian = baseInfo.endian;

      } else if (vinfo.typeInfo.hdfType == 9) { // vlen
        elemSize = vinfo.typeInfo.byteSize;
        endian = vinfo.typeInfo.endian;
        //wantSection = wantSection.removeVlen(); // remove vlen dimension
      }

      if (vinfo.isChunked) {
        layout = new H5tiledLayout((H5header.Vinfo) v2.getSPobject(), readDtype, wantSection);
      } else {
        layout = new LayoutRegular(dataPos, elemSize, v2.getShape(), wantSection);
      }
      data = readData(vinfo, v2, layout, readDtype, wantSection.getShape(), fillValue, endian);
    }

    if (data instanceof Array)
      return (Array) data;
    else if (dataType == DataType.STRUCTURE)
      return convertStructure((Structure) v2, layout, wantSection.getShape(), (byte[]) data);  // LOOK
    else
      return Array.factory(dataType, wantSection.getShape(), data);
  }
all the work is here, so can be called recursively