/************************************************************
  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.
 ************************************************************/
package examples.datasets;

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

public class H5Ex_D_External {
	private static String FILENAME = "H5Ex_D_External.h5";
	private static String EXTERNALNAME = "H5Ex_D_External.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, HDF5Constants.H5P_DEFAULT, dcpl_id, HDF5Constants.H5P_DEFAULT);
		}
		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, HDF5Constants.H5P_DEFAULT);
		}
		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();
	}

}