ncsa.hdf.object
Class Attribute

java.lang.Object
  ncsa.hdf.object.Attribute

All Implemented Interfaces:

java.io.Serializable, Metadata

public class Attribute
extends java.lang.Object
implements Metadata

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

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

For more details on attibutes, see HDF5 User's Guide

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

 // Example of creatinge 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,




See Also:

, Datatype, Serialized Form

Field Summary

static long

serialVersionUID

Constructor Summary

Attribute(java.lang.String attrName, Datatype attrType, long[] attrDims)
Create an attribute with specified name, data type and dimension sizes.

Attribute(java.lang.String attrName, Datatype attrType, long[] attrDims, java.lang.Object attrValue)
Create an attribute with specific name and value.

Method Summary

long[]	getDataDims() Returns the dimension sizes of the data value of the attribute.
java.lang.String	getName() Returns the name of the attribute.
int	getRank() Returns the rank (number of dimensions) of the attribute.
Datatype	getType() Returns the datatype of the attribute.
java.lang.Object	getValue() Returns the value of the attribute.
boolean	isUnsigned() Checks if the data type of this attribute is an unsigned integer.
void	setValue(java.lang.Object theValue) Sets the value of the attribute.
java.lang.String	toString(java.lang.String delimiter) Returns a string representation of the data value of the attribute.

Methods inherited from class java.lang.Object

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

Field Detail

serialVersionUID

public static final long serialVersionUID

See Also:

HObject.serialVersionUID, Constant Field Values

Constructor Detail

Attribute

public Attribute(java.lang.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(java.lang.String attrName,
                 Datatype attrType,
                 long[] attrDims,
                 java.lang.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 java.lang.Object getValue()

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

setValue

public void setValue(java.lang.Object theValue)

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

Specified by:

setValue in interface Metadata

Parameters:

theValue - The value of the attribute to set

getName

public java.lang.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 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 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 failed to retrieve the datatype information from file.

Returns:

the datatype of the attribute.

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 java.lang.String toString(java.lang.String delimiter)

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

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

Parameters:

delimiter - The delimiter to separate individual data point. It can be comma, semicolon, tab or space. For example, to String(",") will separate data by comma.

Returns:

the string representation of the data values.