The HDF5 specification defines the standard objects and storage for the
standard HDF5 objects. (For information about the HDF5 library, model and
specification, see the HDF documentation.) This document is an additional
specification do define a standard profile for how to store tables in HDF5.
Table data in HDF5 is stored as HDF5 datasets with standard attributes to define
the properties of the tables.
1. Overview
A generic table is a sequence of records, each record has a name and a type.
Table data is stored as an HDF5 one dimensional compound dataset. A table
is defined as a collection of records whose values are stored in fixed-length
fields. All records have the same structure and all values in each field have
the same data type.
The dataset for a table is distinguished from other datasets by giving
it an attribute "CLASS=TABLE".
Optional attributes allow the storage of a title for the Table and for
each column, and a fill value for each column.
2. Table Attributes
The attributes for the Table are strings. They are written with the H5LTset_attribute_string
Lite API function. "Required" attributes must always be used. "Optional" attributes
must be used when required.
Attributes
-
Attribute name="CLASS" (Required)
-
This attribute is type H5T_C_S1, with size 5.
-
For all Tables, the value of this attribute is "TABLE".
-
This attribute identifies this data set as intended to be interpreted as Table that conforms to the specifications on this page.
Attribute name="VERSION" (Required)
-
This attribute is of type H5T_C_S1, with size corresponding to the length
of the version string. This attribute identifies the version number
of this specification to which it conforms. The current version number
is "0.2".
-
Attribute name="TITLE" (Optional)
-
The TITLE is an optional String that is to be used as the
informative title of the whole table.
The TITLE is set with the parameter
table_title of the function
H5TBmake_table.
-
Attribute name="FIELD_(n)_NAME" (Required)
-
The FIELD_(n)_NAME is an optional String that is to be used as the
informative title of column n of the table.
For each of the fields the word FIELD_ is concatenated with
the zero based field (n) index together with the name of the field.
-
Attribute name="FIELD_(n)_FILL" (Optional)
-
The FIELD_(n)_FILL is an optional String that is the fill value for
column n of the table.
For each of the fields the word FIELD_ is concatenated with
the zero based field (n) index together with the fill value, if present.
This value is written only when a fill value is defined for the table.
Table 1. Attributes of an Image Dataset
| Attribute Name |
(R = Required
O= Optional) |
Type |
String Size |
Value |
| CLASS |
R |
String |
5 |
"TABLE" |
| VERSION |
R |
String |
3 |
"0.2" |
| TITLE |
O |
String |
|
|
| FIELD_(n)_NAME |
R |
String |
|
|
| FIELD_(n)_FILL |
O* |
String |
|
|
* The attribute FIELD_(n)_FILL is written to the table if a fill value is
specified on the creation of the Table. Otherwise, it is not.The following
section of code shows the calls necessary to the creation of a table.
/* Create a new HDF5 file using default properties. */
file_id = H5Fcreate( "my_table.h5", H5F_ACC_TRUNC, H5P_DEFAULT, H5P_DEFAULT );
/* Call the make table function */
H5TBmake_table( "Table Title", file_id, "Table1", NFIELDS, NRECORDS, dst_size,
field_names, dst_offset, field_type,
chunk_size, fill_data, compress, p_data )
/* Close the file. */
status = H5Fclose( file_id );