/************************************************************

  This example shows how to read and write data to an
  external dataset.  The program first writes integers to an
  external dataset with dataspace dimensions of DIM_XxDIM_Y,
  then closes the file.  Next, it reopens the file, reads
  back the data, and outputs the name of the external data
  file and the data to the screen.

  This file is intended for use with HDF5 Library verion 1.6

 ************************************************************/
package datasets;

import ncsa.hdf.hdf5lib.H5;
import ncsa.hdf.hdf5lib.HDF5Constants;

public class H5Ex_D_External {
	private static String FILENAME = "h5ex_d_extern.h5";
	private static String EXTERNALNAME = "h5ex_d_extern.data";
	private static String DATASETNAME = "DS1";
	private static final int DIM_X = 4;
	private static final int DIM_Y = 7;
	private static final int RANK = 2;
	private static final int NAME_BUF_SIZE = 32;

	private static void writeExternal() {
		int file_id = -1;
		int dcpl_id = -1;
		int filespace_id = -1;
		int dataset_id = -1;
		long[] dims = { DIM_X, DIM_Y };
		int[][] dset_data = new int[DIM_X][DIM_Y];

		// Initialize the dataset.
		for (int indx = 0; indx < DIM_X; indx++)
			for (int jndx = 0; jndx < DIM_Y; jndx++)
				dset_data[indx][jndx] = indx * jndx - jndx;

		// Create a new file using default properties.
		try {
			file_id = H5.H5Fcreate(FILENAME, HDF5Constants.H5F_ACC_TRUNC,
					HDF5Constants.H5P_DEFAULT, HDF5Constants.H5P_DEFAULT);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Create dataspace. Setting maximum size to NULL sets the maximum
		// size to be the current size.
		try {
			filespace_id = H5.H5Screate_simple(RANK, dims, null);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Create the dataset creation property list.
		try {
			dcpl_id = H5.H5Pcreate(HDF5Constants.H5P_DATASET_CREATE);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// set the external file.
		try {
			if (dcpl_id >= 0)
				H5.H5Pset_external(dcpl_id, EXTERNALNAME, 0,
						HDF5Constants.H5F_UNLIMITED);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Create the HDF5Constants.dataset.
		try {
			if ((file_id >= 0) && (filespace_id >= 0) && (dcpl_id >= 0))
				dataset_id = H5.H5Dcreate(file_id, DATASETNAME,
						HDF5Constants.H5T_STD_I32LE, filespace_id, dcpl_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Write the dataset.
		try {
			H5.H5Dwrite(dataset_id, HDF5Constants.H5T_NATIVE_INT,
					HDF5Constants.H5S_ALL, HDF5Constants.H5S_ALL,
					HDF5Constants.H5P_DEFAULT, dset_data);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// End access to the dataset and release resources used by it.
		try {
			if (dataset_id >= 0)
				H5.H5Dclose(dataset_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Terminate access to the data space.
		try {
			if (filespace_id >= 0)
				H5.H5Sclose(filespace_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		try {
			if (dcpl_id >= 0)
				H5.H5Pclose(dcpl_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Close the file.
		try {
			if (file_id >= 0)
				H5.H5Fclose(file_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

	}

	private static void readExternal() {
		int file_id = -1;
		int dcpl_id = -1;
		int dataset_id = -1;
		int[][] dset_data = new int[DIM_X][DIM_Y];
		String[] Xname = new String[1];

		// Open file using the default properties.
		try {
			file_id = H5.H5Fopen(FILENAME, HDF5Constants.H5F_ACC_RDWR,
					HDF5Constants.H5P_DEFAULT);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Open dataset using the default properties.
		try {
			if (file_id >= 0)
				dataset_id = H5.H5Dopen(file_id, DATASETNAME);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Retrieve the dataset creation property list.
		try {
			if (dataset_id >= 0)
				dcpl_id = H5.H5Dget_create_plist(dataset_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Retrieve and print the name of the external file.
		long[] Xsize = new long[NAME_BUF_SIZE];
		try {
			if (dcpl_id >= 0)
				H5.H5Pget_external(dcpl_id, 0, Xsize.length, Xname, Xsize);
		}
		catch (Exception e) {
			e.printStackTrace();
		}
		System.out.println(DATASETNAME + " is stored in file: " + Xname[0]);

		// Read the data using the default properties.
		try {
			if (dataset_id >= 0)
				H5.H5Dread(dataset_id, HDF5Constants.H5T_NATIVE_INT,
						HDF5Constants.H5S_ALL, HDF5Constants.H5S_ALL,
						HDF5Constants.H5P_DEFAULT, dset_data);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Output the data to the screen.
		System.out.println(DATASETNAME + ":");
		for (int indx = 0; indx < DIM_X; indx++) {
			System.out.print(" [ ");
			for (int jndx = 0; jndx < DIM_Y; jndx++)
				System.out.print(dset_data[indx][jndx] + " ");
			System.out.println("]");
		}
		System.out.println();

		// Close the dataset.
		try {
			if (dataset_id >= 0)
				H5.H5Dclose(dataset_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		try {
			if (dcpl_id >= 0)
				H5.H5Pclose(dcpl_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}

		// Close the file.
		try {
			if (file_id >= 0)
				H5.H5Fclose(file_id);
		}
		catch (Exception e) {
			e.printStackTrace();
		}
	}

	public static void main(String[] args) {
		H5Ex_D_External.writeExternal();
		H5Ex_D_External.readExternal();
	}

}