Module org.hdfgroup.object
Package hdf.object

# Class HObject

Object
hdf.object.HObject

All Implemented Interfaces:
  `Serializable`

Direct Known Subclasses:
  `Dataset`, `Datatype`, `Group`, `H5Link`

public abstract class HObject extends Object implements Serializable
The HObject class is the root class of all the HDF data objects. Every data class has HObject as a superclass. All objects implement the methods of this class. The following is the inherited structure of HDF Objects.

                                     HObject
              __________________________|________________________________
              |                         |                               |
            Group                    Dataset                        Datatype
              |                _________|___________                    |
              |                |                   |                    |
              |             ScalarDS          CompoundDS                |
              |                |                   |                    |
        ---------------------Implementing classes such as-------------------------
          ____|____       _____|______        _____|_____          _____|_____
          |       |       |          |        |         |          |         |
       H5Group H4Group H5ScalarDS H4ScalarDS H5CompDS H4CompDS H5Datatype H4Datatype

All HDF4 and HDF5 data objects are inherited from HObject. At the top level of the hierarchy, both HDF4 and HDF5 have the same super-classes, such as Group and Dataset. At the bottom level of the hierarchy, HDF4 and HDF5 objects have their own implementation, such as H5Group, H5ScalarDS, H5CompoundDS, and H5Datatype.

Warning: HDF4 and HDF5 may have multiple links to the same object. Data objects in this model do not deal with multiple links. Users may create duplicate copies of the same data object with different paths. Applications should check the OID of the data object to avoid duplicate copies of the same object.

HDF4 objects are uniquely identified by the OID (tag_id, ref_id) pair. The ref_id is the object reference count. The tag_id is a pre-defined number to identify the type of object. For example, DFTAG_RI is for raster image, DFTAG_SD is for scientific dataset, and DFTAG_VG is for Vgroup.

HDF5 objects are uniquely identified by the OID containing just the object reference. The OID is usually obtained by H5Rcreate(). The following example shows how to retrieve an object ID from a file:

     // retrieve the object ID
     try {
         byte[] ref_buf = H5.H5Rcreate(h5file.getFID(), this.getFullName(), HDF5Constants.H5R_OBJECT, -1);
         long[] oid = new long[1];
         oid[0] = HDFNativeData.byteToLong(ref_buf, 0);
     } catch (Exception ex) {
     }

Version:
  2.0 4/2/2018
Author:
  Peter X. Cao, Jordan T. Henderson
See Also:
  hdf.object.DataFormat, Serialized Form

- ## Field Summary

  Fields
  Modifier and Type
  Field
  Description
  `protected FileFormat`
  `fileFormat`
  The file which contains the object
  `protected String`
  `linkTargetObjName`
  The name of the Target Object that is being linked to.
  `protected long[]`
  `oid`
  Array of long integer storing unique identifier for the object.
  `static String`
  `SEPARATOR`
  The separator of object path, i.e.

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `HObject()`
  Constructs an instance of a data object without name and path.
  `HObject​(FileFormat theFile, String theName, String thePath)`
  Constructs an instance of a data object with specific name and path.
  `HObject​(FileFormat theFile, String theName, String thePath, long[] oid)`
  Deprecated.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `abstract void`
  `close​(long id)`
  Closes access to the object.
  `String`
  `createFullname​(String thePath, String theName)`
  `protected void`
  `debug​(Object msg)`
  Print out debug information
  `boolean`
  `equals​(HObject obj)`
  Returns whether this HObject is equal to the specified HObject by comparing their OIDs.
  `boolean`
  `equals​(Object obj)`
  `boolean`
  `equalsOID​(long[] theID)`
  Checks if the OID of the object is the same as the given object identifier within the same file.
  `long`
  `getFID()`
  Returns the file identifier of of the file containing the object.
  `String`
  `getFile()`
  Returns the name of the file that contains this data object.
  `FileFormat`
  `getFileFormat()`
  Returns the file that contains the object.
  `String`
  `getFullName()`
  Returns the full name (group path + object name) of the object.
  `String`
  `getLinkTargetObjName()`
  Returns the name of the target object that is linked to.
  `String`
  `getName()`
  Returns the name of the object.
  `long[]`
  `getOID()`
  Returns a cloned copy of the object identifier.
  `String`
  `getPath()`
  Returns the group path of the object.
  `int`
  `hashCode()`
  `abstract long`
  `open()`
  Opens an existing object such as a dataset or group for access.
  `void`
  `setFullname​(String thePath, String theName)`
  `void`
  `setLinkTargetObjName​(String targetObjName)`
  Sets the name of the target object that is linked to.
  `void`
  `setName​(String newName)`
  Sets the name of the object.
  `void`
  `setPath​(String newPath)`
  Sets the path of the object.
  `String`
  `toString()`
  Returns the name of the object.

  ### Methods inherited from class java.lang.Object

  `clone, finalize, getClass, notify, notifyAll, wait, wait, wait`

- ## Field Details

  - ### SEPARATOR

    public static final String SEPARATOR
    The separator of object path, i.e. "/".
    See Also:
      Constant Field Values

  - ### fileFormat

    protected final FileFormat fileFormat
    The file which contains the object

  - ### oid

    protected long[] oid
    Array of long integer storing unique identifier for the object.

    HDF4 objects are uniquely identified by a (tag_id, ref_id) pair. i.e. oid[0] = tag, oid[1] = ref_id.
    HDF5 objects are uniquely identified by an object reference. i.e. oid[0] = obj_id.

  - ### linkTargetObjName

    protected String linkTargetObjName
    The name of the Target Object that is being linked to.

- ## Constructor Details

  - ### HObject

    public HObject()
    Constructs an instance of a data object without name and path.

  - ### HObject

    public HObject​(FileFormat theFile, String theName, String thePath)
    Constructs an instance of a data object with specific name and path.

    For example, in H5ScalarDS(h5file, "dset", "/arrays"), "dset" is the name of the dataset, "/arrays" is the group path of the dataset.

    Parameters:
      `theFile` - the file that contains the data object.
      `theName` - the name of the data object, e.g. "dset".
      `thePath` - the group path of the data object, e.g. "/arrays".

  - ### HObject

    @Deprecated public HObject​(FileFormat theFile, String theName, String thePath, long[] oid)
    Deprecated.
    Constructs an instance of a data object with specific name and path.

    For example, in H5ScalarDS(h5file, "dset", "/arrays"), "dset" is the name of the dataset, "/arrays" is the group path of the dataset.

    Parameters:
      `theFile` - the file that contains the data object.
      `theName` - the name of the data object, e.g. "dset".
      `thePath` - the group path of the data object, e.g. "/arrays".
      `oid` - the ids of the data object.

- ## Method Details

  - ### debug

    protected final void debug​(Object msg)
    Print out debug information

    Parameters:
      `msg` - the debug message to print

  - ### getFile

    public final String getFile()
    Returns the name of the file that contains this data object.

    The file name is necessary because the file of this data object is uniquely identified when multiple files are opened by an application at the same time.

    Returns:
      The full path (path + name) of the file.

  - ### getName

    public final String getName()
    Returns the name of the object. For example, "Raster Image #2".
    Returns:
      The name of the object.

  - ### getLinkTargetObjName

    public final String getLinkTargetObjName()
    Returns the name of the target object that is linked to.
    Returns:
      The name of the object that is linked to.

  - ### setLinkTargetObjName

    public final void setLinkTargetObjName​(String targetObjName)
    Sets the name of the target object that is linked to.
    Parameters:
      `targetObjName` - The new name of the object.

  - ### getFullName

    public final String getFullName()
    Returns the full name (group path + object name) of the object. For example, "/Images/Raster Image #2"
    Returns:
      The full name (group path + object name) of the object.

  - ### getPath

    public final String getPath()
    Returns the group path of the object. For example, "/Images".
    Returns:
      The group path of the object.

  - ### setName

    public void setName​(String newName) throws Exception
    Sets the name of the object. setName (String newName) changes the name of the object in the file.
    Parameters:
      `newName` - The new name of the object.
    Throws:
      `Exception` - if name is root or contains separator

  - ### setPath

    public void setPath​(String newPath) throws Exception
    Sets the path of the object.

    setPath() is needed to change the path for an object when the name of a group containing the object is changed by setName(). The path of the object in memory under this group should be updated to the new path to the group. Unlike setName(), setPath() does not change anything in file.

    Parameters:
      `newPath` - The new path of the object.
    Throws:
      `Exception` - if a failure occurred

  - ### setFullname

    public void setFullname​(String thePath, String theName) throws Exception
    Throws:
      `Exception`

  - ### createFullname

    public String createFullname​(String thePath, String theName)

  - ### open

    public abstract long open()
    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.
    Returns:
      the object identifier if successful; otherwise returns a negative value.
    See Also:
      `close(long)`

  - ### close

    public abstract void close​(long id)
    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.

    Parameters:
      `id` - The object identifier.

  - ### getFID

    public final long getFID()
    Returns the file identifier of of the file containing the object.
    Returns:
      the file identifier of of the file containing the object.

  - ### getFileFormat

    public final FileFormat getFileFormat()
    Returns the file that contains the object.
    Returns:
      The file that contains the object.

  - ### getOID

    public final long[] getOID()
    Returns a cloned copy of the object identifier.

    The object OID cannot be modified once it is created. getOID() clones the object OID to ensure the object OID cannot be modified outside of this class.

    Returns:
      the cloned copy of the object OID.

  - ### equalsOID

    public final boolean equalsOID​(long[] theID)
    Checks if the OID of the object is the same as the given object identifier within the same file.

    HDF4 and HDF5 data objects are identified by their unique OIDs. A data object in a file may have multiple logical names , which are represented in a graph structure as separate objects.

    The HObject.equalsOID(long[] theID) can be used to check if two data objects with different names are pointed to the same object within the same file.

    Parameters:
      `theID` - The list object identifiers.
    Returns:
      true if the ID of the object equals the given OID; otherwise, returns false.

  - ### toString

    public String toString()
    Returns the name of the object.

    This method overwrites the toString() method in the Java Object class (the root class of all Java objects) so that it returns the name of the HObject instead of the name of the class.

    For example, toString() returns "Raster Image #2" instead of "hdf.object.h4.H4SDS".

    Overrides:
      `toString` in class `Object`
    Returns:
      The name of the object.

  - ### equals

    public boolean equals​(HObject obj)
    Returns whether this HObject is equal to the specified HObject by comparing their OIDs.
    Parameters:
      `obj` - The object
    Returns:
      true if the object is equal by OID

  - ### equals

    public boolean equals​(Object obj)
    Overrides:
      `equals` in class `Object`

  - ### hashCode

    public int hashCode()
    Overrides:
      `hashCode` in class `Object`