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2  * Copyright by The HDF Group.                                               *
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13 
14 /************************************************************
15   This example shows how to read and write opaque datatypes
16   to an attribute.  The program first writes opaque data to
17   an attribute with a dataspace of DIM0, then closes the
18   file. Next, it reopens the file, reads back the data, and
19   outputs it to the screen.
20  ************************************************************/
21 
22 package examples.datatypes;
23 
24 import hdf.hdf5lib.H5;
25 import hdf.hdf5lib.HDF5Constants;
26 
27 public class H5Ex_T_OpaqueAttribute {
28     private static String FILENAME = "H5Ex_T_OpaqueAttribute.h5";
29     private static String DATASETNAME = "DS1";
30     private static String ATTRIBUTENAME = "A1";
31     private static final int DIM0 = 4;
32     private static final int LEN = 7;
33     private static final int RANK = 1;
34 
CreateDataset()35     private static void CreateDataset() {
36         long file_id = -1;
37         long dataspace_id = -1;
38         long datatype_id = -1;
39         long dataset_id = -1;
40         long attribute_id = -1;
41         long[] dims = { DIM0 };
42         byte[] dset_data = new byte[DIM0 * LEN];
43         byte[] str_data = { 'O', 'P', 'A', 'Q', 'U', 'E' };
44 
45         // Initialize data.
46         for (int indx = 0; indx < DIM0; indx++) {
47             for (int jndx = 0; jndx < LEN - 1; jndx++)
48                 dset_data[jndx + indx * LEN] = str_data[jndx];
49             dset_data[LEN - 1 + indx * LEN] = (byte) (indx + '0');
50         }
51 
52         // Create a new file using default properties.
53         try {
54             file_id = H5.H5Fcreate(FILENAME, HDF5Constants.H5F_ACC_TRUNC, HDF5Constants.H5P_DEFAULT,
55                     HDF5Constants.H5P_DEFAULT);
56         }
57         catch (Exception e) {
58             e.printStackTrace();
59         }
60 
61         // Create dataset with a scalar dataspace.
62         try {
63             dataspace_id = H5.H5Screate(HDF5Constants.H5S_SCALAR);
64             if (dataspace_id >= 0) {
65                 dataset_id = H5.H5Dcreate(file_id, DATASETNAME, HDF5Constants.H5T_STD_I32LE, dataspace_id,
66                         HDF5Constants.H5P_DEFAULT, HDF5Constants.H5P_DEFAULT, HDF5Constants.H5P_DEFAULT);
67                 H5.H5Sclose(dataspace_id);
68                 dataspace_id = -1;
69             }
70         }
71         catch (Exception e) {
72             e.printStackTrace();
73         }
74 
75         // Create opaque datatype and set the tag to something appropriate.
76         // For this example we will write and view the data as a character
77         // array.
78         try {
79             datatype_id = H5.H5Tcreate(HDF5Constants.H5T_OPAQUE, (long)LEN);
80             if (datatype_id >= 0)
81                 H5.H5Tset_tag(datatype_id, "Character array");
82         }
83         catch (Exception e) {
84             e.printStackTrace();
85         }
86 
87         // Create dataspace. Setting maximum size to NULL sets the maximum
88         // size to be the current size.
89         try {
90             dataspace_id = H5.H5Screate_simple(RANK, dims, null);
91         }
92         catch (Exception e) {
93             e.printStackTrace();
94         }
95 
96         // Create the attribute and write the array data to it.
97         try {
98             if ((dataset_id >= 0) && (datatype_id >= 0) && (dataspace_id >= 0))
99                 attribute_id = H5.H5Acreate(dataset_id, ATTRIBUTENAME, datatype_id, dataspace_id,
100                         HDF5Constants.H5P_DEFAULT, HDF5Constants.H5P_DEFAULT);
101         }
102         catch (Exception e) {
103             e.printStackTrace();
104         }
105 
106         // Write the dataset.
107         try {
108             if ((attribute_id >= 0) && (datatype_id >= 0))
109                 H5.H5Awrite(attribute_id, datatype_id, dset_data);
110         }
111         catch (Exception e) {
112             e.printStackTrace();
113         }
114 
115         // End access to the dataset and release resources used by it.
116         try {
117             if (attribute_id >= 0)
118                 H5.H5Aclose(attribute_id);
119         }
120         catch (Exception e) {
121             e.printStackTrace();
122         }
123 
124         try {
125             if (dataset_id >= 0)
126                 H5.H5Dclose(dataset_id);
127         }
128         catch (Exception e) {
129             e.printStackTrace();
130         }
131 
132         // Terminate access to the data space.
133         try {
134             if (dataspace_id >= 0)
135                 H5.H5Sclose(dataspace_id);
136         }
137         catch (Exception e) {
138             e.printStackTrace();
139         }
140 
141         try {
142             if (datatype_id >= 0)
143                 H5.H5Tclose(datatype_id);
144         }
145         catch (Exception e) {
146             e.printStackTrace();
147         }
148 
149         // Close the file.
150         try {
151             if (file_id >= 0)
152                 H5.H5Fclose(file_id);
153         }
154         catch (Exception e) {
155             e.printStackTrace();
156         }
157 
158     }
159 
ReadDataset()160     private static void ReadDataset() {
161         long file_id = -1;
162         long datatype_id = -1;
163         long dataspace_id = -1;
164         long dataset_id = -1;
165         long attribute_id = -1;
166         long type_len = -1;
167         long[] dims = { DIM0 };
168         byte[] dset_data;
169         String tag_name = null;
170 
171         // Open an existing file.
172         try {
173             file_id = H5.H5Fopen(FILENAME, HDF5Constants.H5F_ACC_RDONLY, HDF5Constants.H5P_DEFAULT);
174         }
175         catch (Exception e) {
176             e.printStackTrace();
177         }
178 
179         // Open an existing dataset.
180         try {
181             if (file_id >= 0)
182                 dataset_id = H5.H5Dopen(file_id, DATASETNAME, HDF5Constants.H5P_DEFAULT);
183         }
184         catch (Exception e) {
185             e.printStackTrace();
186         }
187 
188         try {
189             if (dataset_id >= 0)
190                 attribute_id = H5.H5Aopen_by_name(dataset_id, ".", ATTRIBUTENAME, HDF5Constants.H5P_DEFAULT,
191                         HDF5Constants.H5P_DEFAULT);
192         }
193         catch (Exception e) {
194             e.printStackTrace();
195         }
196 
197         // Get datatype and properties for the datatype.
198         try {
199             if (attribute_id >= 0)
200                 datatype_id = H5.H5Aget_type(attribute_id);
201             if (datatype_id >= 0) {
202                 type_len = H5.H5Tget_size(datatype_id);
203                 tag_name = H5.H5Tget_tag(datatype_id);
204             }
205         }
206         catch (Exception e) {
207             e.printStackTrace();
208         }
209 
210         // Get dataspace and allocate memory for read buffer.
211         try {
212             if (attribute_id >= 0)
213                 dataspace_id = H5.H5Aget_space(attribute_id);
214         }
215         catch (Exception e) {
216             e.printStackTrace();
217         }
218 
219         try {
220             if (dataspace_id >= 0)
221                 H5.H5Sget_simple_extent_dims(dataspace_id, dims, null);
222         }
223         catch (Exception e) {
224             e.printStackTrace();
225         }
226 
227         // Allocate buffer.
228         dset_data = new byte[(int) (dims[0] * type_len)];
229 
230         // Read data.
231         try {
232             if ((attribute_id >= 0) && (datatype_id >= 0))
233                 H5.H5Aread(attribute_id, datatype_id, dset_data);
234         }
235         catch (Exception e) {
236             e.printStackTrace();
237         }
238 
239         // Output the data to the screen.
240         System.out.println("Datatype tag for " + ATTRIBUTENAME + " is: \"" + tag_name + "\"");
241         for (int indx = 0; indx < dims[0]; indx++) {
242             System.out.print(ATTRIBUTENAME + "[" + indx + "]: ");
243             for (int jndx = 0; jndx < type_len; jndx++) {
244                 char temp = (char) dset_data[jndx + indx * (int)type_len];
245                 System.out.print(temp);
246             }
247             System.out.println("");
248         }
249         System.out.println();
250 
251         // End access to the dataset and release resources used by it.
252         try {
253             if (attribute_id >= 0)
254                 H5.H5Aclose(attribute_id);
255         }
256         catch (Exception e) {
257             e.printStackTrace();
258         }
259 
260         try {
261             if (dataset_id >= 0)
262                 H5.H5Dclose(dataset_id);
263         }
264         catch (Exception e) {
265             e.printStackTrace();
266         }
267 
268         // Terminate access to the data space.
269         try {
270             if (dataspace_id >= 0)
271                 H5.H5Sclose(dataspace_id);
272         }
273         catch (Exception e) {
274             e.printStackTrace();
275         }
276 
277         try {
278             if (datatype_id >= 0)
279                 H5.H5Tclose(datatype_id);
280         }
281         catch (Exception e) {
282             e.printStackTrace();
283         }
284 
285         // Close the file.
286         try {
287             if (file_id >= 0)
288                 H5.H5Fclose(file_id);
289         }
290         catch (Exception e) {
291             e.printStackTrace();
292         }
293 
294     }
295 
main(String[] args)296     public static void main(String[] args) {
297         H5Ex_T_OpaqueAttribute.CreateDataset();
298         // Now we begin the read section of this example. Here we assume
299         // the dataset and array have the same name and rank, but can have
300         // any size. Therefore we must allocate a new array to read in
301         // data using malloc().
302         H5Ex_T_OpaqueAttribute.ReadDataset();
303     }
304 
305 }
306