hdf5/examples/Attributes.txt
2020-04-20 18:12:00 -05:00

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Attribute Examples:
H5Acreate2 example: Show how to create an attribute for a dataset and a group
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{
hid_t file;
hid_t group;
hid_t dataset;
hid_t attr;
hid_t dataspace;
int32 attr_data;
int rank;
size_t dimsf[2];
/* Open the file */
file=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
/* Describe the size of the array and create the data space */
rank=2;
dimsf[0] = H5S_UNLIMITED;
dimsf[1] = H5S_UNLIMITED;
dataspace = H5Screate_simple(rank, dimsf, NULL);
/* Create a dataset */
dataset = H5Dcreate2(file, "Dataset1", H5T_UINT8, dataspace, H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
<Write data to first dataset>
/* Create an attribute for the dataset */
attr = H5Acreate2(dataset, "Attr1", H5T_INT32, H5S_SCALAR, H5P_DEFAULT, H5P_DEFAULT);
/* Write attribute information */
H5Awrite(attr, H5T_INT32, &attr_data);
/* Close attribute */
H5Aclose(attr);
/* Close dataset */
H5Dclose(dataset);
/* Create a group */
group = H5Gcreate2(file, "/Group One", H5P_DEFAULT, H5P_DEFAULT, H5P_DEFAULT);
/* Create an attribute for the dataset */
attr = H5Acreate2(group, "Attr1", H5T_INT32, H5S_SCALAR, H5P_DEFAULT, H5P_DEFAULT);
/* Write attribute information */
H5Awrite(attr, H5T_INT32, &attr_data);
/* Close attribute */
H5Aclose(attr);
/* Close the group */
H5Gclose(group);
/* Close file */
H5Fclose(file);
}
H5Aiterate example: Print all the names of attributes of a dataset, without
any buffers.
---------------------
herr_t print_names (hid_t loc_id, const char *name, void *opdata)
{
puts (name);
return 0;
}
{
H5Aiterate (dataset_or_group_id, NULL, print_names, NULL);
}
H5Aread Example: Attach to an attribute of a dataset and read in attr. data
----------------
{
hid_t file;
hid_t dataset;
hid_t attr;
int32 attr_data;
/* Open the file */
file=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
/* Open the dataset */
dataset=H5Dopen2(file, "Dataset1", H5P_DEFAULT);
/* Get the OID of the attribute */
attr=H5Aopen(dataset, "Attr1", H5P_DEFAULT);
/* Read attribute */
H5Aread(attr,H5T_INT32,attr_data);
/* Close attribute dataset */
H5Aclose(attr);
/* Close first dataset */
H5Dclose(dataset);
/* Close file */
H5Fclose(file);
}
H5Alink Example: Shows how to share an attribute between two datasets.
----------------
{
hid_t file;
hid_t dataset1, dataset2;
hid_t attr;
/* Open the file */
file=H5Fopen("example.h5", H5F_ACC_RDWR, H5P_DEFAULT);
/* Open the first dataset */
dataset1=H5Dopen2(file, "Dataset1", H5P_DEFAULT);
/* Open the first dataset */
dataset2=H5Dopen2(file, "Dataset2", H5P_DEFAULT);
/* Get the OID of the attribute */
attr=H5Aopen(dataset1, "Foo", H5P_DEFAULT);
/*
* Create an attribute in the second dataset to the attribute in dataset1,
* changing the name of the attribute information in dataset2.
*/
H5Alink(dataset2, attr, "Bar");
/* Close attribute dataset */
H5Aclose(attr);
/* Close datasets */
H5Dclose(dataset1);
H5Dclose(dataset2);
/* Close file */
H5Fclose(file);
}