Module org.hdfgroup.object
Package hdf.object.nc2

Class NC2Attribute

Object
hdf.object.HObject
hdf.object.Dataset
hdf.object.ScalarDS
hdf.object.nc2.NC2Attribute
All Implemented Interfaces:
Attribute, DataFormat, Serializable
public class NC2Attribute extends ScalarDS implements Attribute
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);    // 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 hdf.object.FileFormat#writeAttribute(HObject, Attribute, boolean)
For an atomic datatype, the value of an Attribute 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.
Version:
2.0 4/2/2018
Author:
Peter X. Cao, Jordan T. Henderson
See Also:

  • Field Details

    • parentObject

      protected HObject parentObject
      The HObject to which this NC2Attribute is attached, Attribute interface

  • Constructor Details

    • NC2Attribute

      public NC2Attribute(HObject parentObj, 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 = null;
 try {
     attrType = new NC2Datatype(Datatype.CLASS_STRING, classValue[0].length() + 1, Datatype.NATIVE, Datatype.NATIVE);
 }
 catch (Exception ex) {}
 Attribute attr = new Attribute(attrName, attrType, attrDims);
 attr.setValue(classValue);
      Parameters:
      parentObj - the HObject to which this Attribute is attached.
      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:

    • NC2Attribute

      public NC2Attribute(HObject parentObj, 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 = null;
 try {
     attrType = new NC2Datatype(Datatype.CLASS_STRING, classValue[0].length() + 1, Datatype.NATIVE, Datatype.NATIVE);
 }
 catch (Exception ex) {}
 NC2Attribute attr = new NC2Attribute(attrName, attrType, attrDims, classValue);
      Parameters:
      parentObj - the HObject to which this Attribute is attached.
      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:

  • Method Details

    • open

      public long open()
      Description copied from class: HObject
      Opens an existing object such as a dataset or group for access. The return value is an object identifier obtained by implementing classes such as H5.H5Dopen(). This function is needed to allow other objects to be able to access the object. For instance, H5File class uses the open() function to obtain object identifier for copyAttributes(long src_id, long dst_id) and other purposes. The open() function should be used in pair with close(long) function.
      Specified by:
      open in class HObject
      Returns:
      the object identifier if successful; otherwise returns a negative value.
      See Also:

    • close

      public void close(long aid)
      Description copied from class: HObject
      Closes access to the object. Sub-classes must implement this interface because different data objects have their own ways of how the data resources are closed. For example, H5Group.close() calls the hdf.hdf5lib.H5.H5Gclose() method and closes the group resource specified by the group id.
      Specified by:
      close in class HObject
      Parameters:
      aid - The object identifier.

    • init

      public void init()
      Description copied from interface: DataFormat
      Set the initial state of all the variables
      Specified by:
      init in interface DataFormat

    • read

      public Object read() throws Exception, OutOfMemoryError
      Reads the data from file. read() reads the data from file to a memory buffer and returns the memory buffer. The dataset object does not hold the memory buffer. To store the memory buffer in the dataset object, one must call getData(). By default, the whole dataset is read into memory. Users can also select a subset to read. Subsetting is done in an implicit way.
      Specified by:
      read in interface DataFormat
      Returns:
      the data read from file.
      Throws:
      Exception - if object can not be read
      OutOfMemoryError - if memory is exhausted
      See Also:

    • write

      public void write(Object buf) throws Exception
      Writes a memory buffer to the object in the file.
      Specified by:
      write in interface DataFormat
      Parameters:
      buf - the data to write
      Throws:
      Exception - if data can not be written

    • copy

      public Dataset copy(Group pgroup, String dstName, long[] dims, Object buff) throws Exception
      Description copied from class: Dataset
      Creates a new dataset and writes the data buffer to the new dataset. This function allows applications to create a new dataset for a given data buffer. For example, users can select a specific interesting part from a large image and create a new image with the selection. The new dataset retains the datatype and dataset creation properties of this dataset.
      Specified by:
      copy in class Dataset
      Parameters:
      pgroup - the group which the dataset is copied to.
      dstName - the name of the new dataset.
      dims - the dimension sizes of the the new dataset.
      buff - the data values of the subset to be copied.
      Returns:
      the new dataset.
      Throws:
      Exception - if dataset can not be copied

    • readBytes

      public byte[] readBytes() throws Exception
      Description copied from class: Dataset
      Reads the raw data of the dataset from file to a byte array. readBytes() reads raw data to an array of bytes instead of array of its datatype. For example, for a one-dimension 32-bit integer dataset of size 5, readBytes() returns a byte array of size 20 instead of an int array of 5. readBytes() can be used to copy data from one dataset to another efficiently because the raw data is not converted to its native type, it saves memory space and CPU time.
      Specified by:
      readBytes in class Dataset
      Returns:
      the byte array of the raw data.
      Throws:
      Exception - if data can not be read

    • getParentObject

      public HObject getParentObject()
      Returns the HObject to which this Attribute is currently "attached".
      Specified by:
      getParentObject in interface Attribute
      Returns:
      the HObject to which this Attribute is currently "attached".

    • setParentObject

      public void setParentObject(HObject pObj)
      Sets the HObject to which this Attribute is "attached".
      Specified by:
      setParentObject in interface Attribute
      Parameters:
      pObj - the new HObject to which this Attribute is "attached".

    • setProperty

      public void setProperty(String key, Object value)
      set a property for the attribute.
      Specified by:
      setProperty in interface 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.
      Specified by:
      getProperty in interface Attribute
      Parameters:
      key - the attribute Map key
      Returns:
      the property

    • getPropertyKeys

      public Collection<String> getPropertyKeys()
      get all property keys.
      Specified by:
      getPropertyKeys in interface Attribute
      Returns:
      the Collection of property keys

    • getAttributeName

      public final String getAttributeName()
      Returns the name of the object. For example, "Raster Image #2".
      Specified by:
      getAttributeName in interface Attribute
      Returns:
      The name of the object.

    • getAttributeData

      public final Object getAttributeData() throws Exception, OutOfMemoryError
      Retrieves the attribute data from the file.
      Specified by:
      getAttributeData in interface Attribute
      Returns:
      the attribute data.
      Throws:
      Exception - if the data can not be retrieved
      OutOfMemoryError

    • getAttributeDatatype

      public final Datatype getAttributeDatatype()
      Returns the datatype of the attribute.
      Specified by:
      getAttributeDatatype in interface Attribute
      Returns:
      the datatype of the attribute.

    • getAttributeSpaceType

      public final int getAttributeSpaceType()
      Returns the space type for the attribute. It returns a negative number if it failed to retrieve the type information from the file.
      Specified by:
      getAttributeSpaceType in interface Attribute
      Returns:
      the space type for the attribute.

    • getAttributeRank

      public final int getAttributeRank()
      Returns the rank (number of dimensions) of the attribute. It returns a negative number if it failed to retrieve the dimension information from the file.
      Specified by:
      getAttributeRank in interface Attribute
      Returns:
      the number of dimensions of the attribute.

    • getAttributePlane

      public final int getAttributePlane()
      Returns the selected size of the rows and columns of the attribute. It returns a negative number if it failed to retrieve the size information from the file.
      Specified by:
      getAttributePlane in interface Attribute
      Returns:
      the selected size of the rows and colums of the attribute.

    • getAttributeDims

      public final long[] getAttributeDims()
      Returns the array that contains the dimension sizes of the data value of the attribute. It returns null if it failed to retrieve the dimension information from the file.
      Specified by:
      getAttributeDims in interface Attribute
      Returns:
      the dimension sizes of the attribute.

    • isAttributeScalar

      public boolean isAttributeScalar()
      Specified by:
      isAttributeScalar in interface Attribute
      Returns:
      true if the data is a single scalar point; otherwise, returns false.

    • setAttributeData

      public void setAttributeData(Object d)
      Not for public use in the future. setData() is not safe to use because it changes memory buffer of the dataset object. Dataset operations such as write/read will fail if the buffer type or size is changed.
      Specified by:
      setAttributeData in interface Attribute
      Parameters:
      d - the object data -must be an array of Objects

    • writeAttribute

      public void writeAttribute() throws Exception
      Writes the memory buffer of this dataset to file.
      Specified by:
      writeAttribute in interface Attribute
      Throws:
      Exception - if buffer can not be written

    • writeAttribute

      public void writeAttribute(Object buf) throws Exception
      Writes the given data buffer into this attribute in a file. The data buffer is a vector that contains the data values of compound fields. The data is written into file as one data blob.
      Specified by:
      writeAttribute in interface Attribute
      Parameters:
      buf - The vector that contains the data values of compound fields.
      Throws:
      Exception - If there is an error at the library level.

    • toAttributeString

      public String toAttributeString(String delimiter)
      Returns a string representation of the data value. 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.
      Specified by:
      toAttributeString in interface Attribute
      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.

    • toAttributeString

      public String toAttributeString(String delimiter, int maxItems)
      Returns a string representation of the data value. 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.
      Specified by:
      toAttributeString in interface Attribute
      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.
      maxItems - The maximum number of Array values to return
      Returns:
      the string representation of the data values.