hdf.object

Class Attribute

Object

hdf.object.Attribute

All Implemented Interfaces:

Metadata, Serializable

public class Attribute
extends Object
implements Metadata

An attribute is a (name, value) pair of metadata attached to a primary data object such as a dataset, group or named datatype.

Like a dataset, an attribute has a name, datatype and dataspace.

For more details on attributes, HDF5 User's Guide

The following code is an example of an attribute with 1D integer array of two elements.

 // Example of creating a new attribute
 // The name of the new attribute
 String name = "Data range";
 // Creating an unsigned 1-byte integer datatype
 Datatype type = new Datatype(Datatype.CLASS_INTEGER, // class
                              1,                      // size in bytes
                              Datatype.ORDER_LE,      // byte order
                              Datatype.SIGN_NONE);    // signed or unsigned
 // 1-D array of size two
 long[] dims = {2};
 // The value of the attribute
 int[] value = {0, 255};
 // Create a new attribute
 Attribute dataRange = new Attribute(name, type, dims);
 // Set the attribute value
 dataRange.setValue(value);
 // See FileFormat.writeAttribute() for how to attach an attribute to an object,

Version:

1.1 9/4/2007

Author:

Peter X. Cao

See Also:

, Datatype, Serialized Form

Field Summary

Fields

Modifier and Type	Field and Description
protected boolean	isScalar flag to indicate if the dataset is a single scalar point

Constructor Summary

Constructors

Constructor and Description
Attribute(String attrName, Datatype attrType, long[] attrDims) Create an attribute with specified name, data type and dimension sizes.
Attribute(String attrName, Datatype attrType, long[] attrDims, Object attrValue) Create an attribute with specific name and value.

Method Summary

Modifier and Type	Method and Description
long[]	getDataDims() Returns the dimension sizes of the data value of the attribute.
String	getName() Returns the name of the attribute.
Object	getProperty(String key) get a property for a given key.
Collection<String>	getPropertyKeys() get all property keys.
int	getRank() Returns the rank (number of dimensions) of the attribute.
Datatype	getType() Returns the datatype of the attribute.
Object	getValue() Returns the value of the attribute.
boolean	isScalar()
boolean	isUnsigned() Checks if the data type of this attribute is an unsigned integer.
void	setProperty(String key, Object value) set a property for the attribute.
void	setValue(Object theValue) Sets the value of the attribute.
String	toString() Return the name of the attribute.
String	toString(String delimiter) Returns a string representation of the data value of the attribute.

Methods inherited from class Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Field Detail

isScalar

protected boolean isScalar

flag to indicate if the dataset is a single scalar point

Constructor Detail

Attribute

public Attribute(String attrName,
                 Datatype attrType,
                 long[] attrDims)

Create an attribute with specified name, data type and dimension sizes. For scalar attribute, the dimension size can be either an array of size one or null, and the rank can be either 1 or zero. Attribute is a general class and is independent of file format, e.g., the implementation of attribute applies to both HDF4 and HDF5.

The following example creates a string attribute with the name "CLASS" and value "IMAGE".

 long[] attrDims = { 1 };
 String attrName = "CLASS";
 String[] classValue = { "IMAGE" };
 Datatype attrType = new H5Datatype(Datatype.CLASS_STRING, classValue[0].length() + 1, -1, -1);
 Attribute attr = new Attribute(attrName, attrType, attrDims);
 attr.setValue(classValue);
 

Parameters:

attrName - the name of the attribute.

attrType - the datatype of the attribute.

attrDims - the dimension sizes of the attribute, null for scalar attribute

See Also:

Datatype

Attribute

public Attribute(String attrName,
                 Datatype attrType,
                 long[] attrDims,
                 Object attrValue)

Create an attribute with specific name and value. For scalar attribute, the dimension size can be either an array of size one or null, and the rank can be either 1 or zero. Attribute is a general class and is independent of file format, e.g., the implementation of attribute applies to both HDF4 and HDF5.

The following example creates a string attribute with the name "CLASS" and value "IMAGE".

 long[] attrDims = { 1 };
 String attrName = "CLASS";
 String[] classValue = { "IMAGE" };
 Datatype attrType = new H5Datatype(Datatype.CLASS_STRING, classValue[0].length() + 1, -1, -1);
 Attribute attr = new Attribute(attrName, attrType, attrDims, classValue);
 

Parameters:

attrName - the name of the attribute.

attrType - the datatype of the attribute.

attrDims - the dimension sizes of the attribute, null for scalar attribute

attrValue - the value of the attribute, null if no value

See Also:

Datatype

Method Detail

getValue

public Object getValue()

Returns the value of the attribute. For an atomic datatype, this will be a 1D array of integers, floats and strings. For a compound datatype, it will be a 1D array of strings with field members separated by a comma. For example, "{0, 10.5}, {255, 20.0}, {512, 30.0}" is a compound attribute of {int, float} of three data points.

Specified by:

getValue in interface Metadata

Returns:

the value of the attribute, or null if failed to retrieve data from file.

setProperty

public void setProperty(String key,
                        Object value)

set a property for the attribute.

Parameters:

key - the attribute Map key

value - the attribute Map value

getProperty

public Object getProperty(String key)

get a property for a given key.

Parameters:

key - the attribute Map key

Returns:

the property

getPropertyKeys

public Collection<String> getPropertyKeys()

get all property keys.

Returns:

the Collection of property keys

setValue

public void setValue(Object theValue)

Sets the value of the attribute. It returns null if it failed to retrieve the name from file.

Specified by:

setValue in interface Metadata

Parameters:

theValue - The value of the attribute to set

getName

public String getName()

Returns the name of the attribute.

Returns:

the name of the attribute.

getRank

public int getRank()

Returns the rank (number of dimensions) of the attribute. It returns a negative number if it failed to retrieve the dimension information from file.

Returns:

the number of dimensions of the attribute.

getDataDims

public long[] getDataDims()

Returns the dimension sizes of the data value of the attribute. It returns null if it failed to retrieve the dimension information from file.

Returns:

the dimension sizes of the attribute.

getType

public Datatype getType()

Returns the datatype of the attribute. It returns null if it failed to retrieve the datatype information from file.

Returns:

the datatype of the attribute.

isScalar

public boolean isScalar()

Returns:

true if the data is a single scalar point; otherwise, returns false.

isUnsigned

public boolean isUnsigned()

Checks if the data type of this attribute is an unsigned integer.

Returns:

true if the data type of the attribute is an unsigned integer; otherwise returns false.

toString

public String toString()

Return the name of the attribute.

Overrides:

toString in class Object

See Also:

toString(String delimiter)

toString

public String toString(String delimiter)

Returns a string representation of the data value of the attribute. For example, "0, 255".

For a compound datatype, it will be a 1D array of strings with field members separated by the delimiter. For example, "{0, 10.5}, {255, 20.0}, {512, 30.0}" is a compound attribute of {int, float} of three data points.

Parameters:

delimiter - The delimiter used to separate individual data points. It can be a comma, semicolon, tab or space. For example, toString(",") will separate data by commas.

Returns:

the string representation of the data values.