ncsa.hdf.object.h4
Class H4Vdata

java.lang.Object
  extended byncsa.hdf.object.HObject
      extended byncsa.hdf.object.Dataset
          extended byncsa.hdf.object.CompoundDS
              extended byncsa.hdf.object.h4.H4Vdata
All Implemented Interfaces:
DataFormat, java.io.Serializable

public class H4Vdata
extends CompoundDS

H4Vdata describes a multi-dimension array of HDF4 vdata, inheriting CompoundDS.

A vdata is like a table that consists of 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. Vdatas are uniquely identified by a name, a class, and a series of individual field names.

How to Select a Subset

Dataset defines APIs for read, write and subet a dataset. No function is defined to select a subset of a data array. The selection is done in an implicit way. Function calls to dimension information such as getSelectedDims() return an array of dimension values, which is a reference to the array in the dataset object. Changes of the array outside the dataset object directly change the values of the array in the dataset object. It is like pointers in C.

The following is an example of how to make a subset. In the example, the dataset is a 4-dimension with size of [200][100][50][10], i.e. dims[0]=200; dims[1]=100; dims[2]=50; dims[3]=10;
We want to select every other data points in dims[1] and dims[2]

     int rank = dataset.getRank();   // number of dimension of the dataset
     long[] dims = dataset.getDims(); // the dimension sizes of the dataset
     long[] selected = dataset.getSelectedDims(); // the selected size of the dataet
     long[] start = dataset.getStartDims(); // the off set of the selection
     long[] stride = dataset.getStride(); // the stride of the dataset
     int[]  selectedIndex = dataset.getSelectedIndex(); // the selected dimensions for display

     // select dim1 and dim2 as 2D data for display,and slice through dim0
     selectedIndex[0] = 1;
     selectedIndex[1] = 2;
     selectedIndex[1] = 0;

     // reset the selection arrays
     for (int i=0; i

 

See Also:
Serialized Form

Field Summary
 
Fields inherited from class ncsa.hdf.object.CompoundDS
isMemberSelected, memberDims, memberNames, memberOrders, memberTypes, numberOfMembers
 
Fields inherited from class ncsa.hdf.object.Dataset
chunkSize, compression, data, datatype, dimNames, dims, H5Z_FILTER_CONFIG_DECODE_ENABLED, H5Z_FILTER_CONFIG_ENCODE_ENABLED, rank, selectedDims, selectedIndex, selectedStride, startDims
 
Fields inherited from class ncsa.hdf.object.HObject
hasAttribute, oid, separator
 
Constructor Summary
H4Vdata(FileFormat fileFormat, java.lang.String name, java.lang.String path)
           
H4Vdata(FileFormat fileFormat, java.lang.String name, java.lang.String path, long[] oid)
          Creates an H4Vdata object with specific name and path.
 
Method Summary
 void close(int vsid)
          Closes access to this object.
 Dataset copy(Group pgroup, java.lang.String dname, long[] dims, java.lang.Object data)
          Copy this dataset to another group.
 Datatype getDatatype()
          returns the datatype of this dataset.
 int getFieldCount()
          Returns the number of fields.
 int[] getFieldOrders()
          Returns the orders of fields
 java.util.List getMetadata()
          Loads the metadata such as attributes and type of the the data object into memory if the metadata is not loaded.
 int getRecordCount()
          Returns the number of records.
 void init()
          Initializes the H4Vdata such as dimension sizes of this dataset.
 int open()
          Opens access to this object.
 java.lang.Object read()
          Loads and returns the data value from file.
 byte[] readBytes()
          Read data values of this dataset into byte array.
 void removeMetadata(java.lang.Object info)
          Deletes an existing metadata from this data object.
 void write(java.lang.Object buf)
          Write data values into file.
 void writeMetadata(java.lang.Object info)
          Saves a specific metadata into file.
 
Methods inherited from class ncsa.hdf.object.CompoundDS
getMemberCount, getMemberNames, getMemberOrders, getMemberTypes, getMemeberDims, getSelectedMemberCount, getSelectedMemberOrders, isMemberSelected, selectMember, setMemberSelection
 
Methods inherited from class ncsa.hdf.object.Dataset
byteToString, clearData, convertFromUnsignedC, convertToUnsignedC, getChunkSize, getCompression, getData, getDimNames, getDims, getHeight, getRank, getSelectedDims, getSelectedIndex, getStartDims, getStride, getWidth, setData, stringToByte, write
 
Methods inherited from class ncsa.hdf.object.HObject
equalsOID, getFID, getFile, getFileFormat, getName, getOID, getPath, hasAttribute, setName, setPath, toString
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
 

Constructor Detail

H4Vdata

public H4Vdata(FileFormat fileFormat,
               java.lang.String name,
               java.lang.String path)

H4Vdata

public H4Vdata(FileFormat fileFormat,
               java.lang.String name,
               java.lang.String path,
               long[] oid)
Creates an H4Vdata object with specific name and path.

Parameters:
fileFormat - the HDF file.
name - the name of this H4Vdata.
path - the full path of this H4Vdata.
oid - the unique identifier of this data object.
Method Detail

getDatatype

public Datatype getDatatype()
Description copied from class: Dataset
returns the datatype of this dataset.

Specified by:
getDatatype in class Dataset

copy

public Dataset copy(Group pgroup,
                    java.lang.String dname,
                    long[] dims,
                    java.lang.Object data)
             throws java.lang.Exception
Description copied from class: Dataset
Copy this dataset to another group.

Specified by:
copy in class Dataset
Parameters:
pgroup - the group which the dataset is copied to.
dname - the name of the new dataset.
dims - the dimension sizes of the the new dataset.
data - the data to be copied.
Returns:
the new dataset.
Throws:
java.lang.Exception

readBytes

public byte[] readBytes()
                 throws HDFException
Description copied from class: Dataset
Read data values of this dataset into byte array. readBytes() loads data as arry of bytes instead of array of its datatype. For example, for an one-dimension 32-bit integer dataset of size 5, the readBytes() returns of a byte array of size 20 instead of a int array of 5.

readBytes() is most used for copy data values, at which case, data do not need to be changed or displayed.

Specified by:
readBytes in class Dataset
Throws:
HDFException

read

public java.lang.Object read()
                      throws HDFException
Description copied from class: Dataset
Loads and returns the data value from file.

Specified by:
read in class Dataset
Throws:
HDFException

write

public void write(java.lang.Object buf)
           throws HDFException
Description copied from class: Dataset
Write data values into file.

Specified by:
write in class Dataset
Parameters:
buf - the data to write
Throws:
HDFException

getMetadata

public java.util.List getMetadata()
                           throws HDFException
Description copied from interface: DataFormat
Loads the metadata such as attributes and type of the the data object into memory if the metadata is not loaded. If the metadata is loaded, it returns the metadata. The metadata is stored as a collection of metadata ojbects in a List.

Returns:
the list of metadata objects.
Throws:
HDFException
See Also:
List

writeMetadata

public void writeMetadata(java.lang.Object info)
                   throws java.lang.Exception
Description copied from interface: DataFormat
Saves a specific metadata into file. If the metadata exists, it updates its value. If the metadata does not exists, it creates and attach the new metadata to the object and saves it into file.

Parameters:
info - the specific metadata.
Throws:
java.lang.Exception

removeMetadata

public void removeMetadata(java.lang.Object info)
                    throws HDFException
Description copied from interface: DataFormat
Deletes an existing metadata from this data object.

Parameters:
info - the metadata to delete.
Throws:
HDFException

open

public int open()
Description copied from class: HObject
Opens access to this object.

Sub-classes have to implement this interface so that different data objects have their own ways of how the data resources are opened.

Specified by:
open in class HObject
Returns:
the interface identifier for access this object.

close

public void close(int vsid)
Description copied from class: HObject
Closes access to this object.

Specified by:
close in class HObject
Parameters:
vsid - the object identifier. Sub-classes have to implement this interface so that different data objects have their own ways of how the data resources are closed.

init

public void init()
Initializes the H4Vdata such as dimension sizes of this dataset.

Specified by:
init in class Dataset

getRecordCount

public int getRecordCount()
Returns the number of records.


getFieldCount

public int getFieldCount()
Returns the number of fields.


getFieldOrders

public int[] getFieldOrders()
Returns the orders of fields