Class HObject

  • All Implemented Interfaces:
    java.io.Serializable, DataFormat
    Direct Known Subclasses:
    Dataset, Datatype, Group

    public abstract class HObject
    extends java.lang.Object
    implements java.io.Serializable, DataFormat
    The HObject class is the root class of all the HDF data objects. Every data class has HObject as a superclass. All objects (Groups and Datasets) 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 H4SclarDS 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 pathes. 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 of the (ref_id, tag_id) pair. The ref_id is the object reference count. 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 or 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:
    1.1 9/4/2007
    Author:
    Peter X. Cao
    See Also:
    ncsa.hdf.object.DataFormat, Serialized Form
    • Field Summary

      Fields 
      Modifier and Type Field Description
      protected FileFormat fileFormat
      The file which contains the object
      protected java.lang.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 java.lang.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, java.lang.String theName, java.lang.String thePath)
      Constructs an instance of a data object with specific name and path.
      HObject​(FileFormat theFile, java.lang.String theName, java.lang.String thePath, long[] oid)
      Deprecated.
      Not for public use in the future.
      Using HObject(FileFormat, String, String)
    • Method Summary

      All Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      abstract void close​(int id)
      Closes access to the object.
      protected void debug​(java.lang.Object msg)
      Print out debug information
      boolean equalsOID​(long[] theID)
      Checks if the OID of the object is the same as the given object identifier within the same file.
      int getFID()
      Returns the file identifier of of the file containing the object.
      java.lang.String getFile()
      Returns the name of the file that contains this data object.
      FileFormat getFileFormat()
      Returns the file that contains the object.
      java.lang.String getFullName()
      Returns the full name (group path + object name) of the object.
      java.lang.String getLinkTargetObjName()
      Returns the name of the target object that is linked to.
      java.lang.String getName()
      Returns the name of the object.
      long[] getOID()
      Returns a cloned copy of the object identifier.
      java.lang.String getPath()
      Returns the group path of the object.
      abstract int open()
      Opens an existing object such as dataset or group for access.
      void setLinkTargetObjName​(java.lang.String targetObjName)
      Sets the name of the target object that is linked to.
      void setName​(java.lang.String newName)
      Sets the name of the object.
      void setPath​(java.lang.String newPath)
      Sets the path of the object.
      java.lang.String toString()
      Returns the name of the object.
      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait
    • Field Detail

      • separator

        public static final java.lang.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 (ref_id, tag_id) pair. i.e. oid[0]=tag, oid[1]=ref.
        HDF5 objects are uniquely identified by an object reference.

      • linkTargetObjName

        protected java.lang.String linkTargetObjName
        The name of the Target Object that is being linked to.
    • Constructor Detail

      • HObject

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

        public HObject​(FileFormat theFile,
                       java.lang.String theName,
                       java.lang.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".
    • Method Detail

      • debug

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

        Parameters:
        msg - the debug message to print
      • getFile

        public final java.lang.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.

        Specified by:
        getFile in interface DataFormat
        Returns:
        The full path (path + name) of the file.
      • getName

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

        public final java.lang.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​(java.lang.String targetObjName)
        Sets the name of the target object that is linked to.
      • getFullName

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

        public void setName​(java.lang.String newName)
                     throws java.lang.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:
        java.lang.Exception
      • setPath

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

        setPath() is needed to change the path for an object when the name of a group conatining 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:
        java.lang.Exception
      • open

        public abstract int open()
        Opens an existing object such as 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(int src_id, int dst_id) and other purposes. The open() function should be used in pair with close(int) function.
        Returns:
        the object identifier if successful; otherwise returns a negative value.
        See Also:
        close(int)
      • close

        public abstract void close​(int 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 ncsa.hdf.hdf5lib.H5.H5Gclose() method and closes the group resource specified by the group id.

        Parameters:
        id - The object identifier.
      • getFID

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

        Returns:
        true if the ID of the object equals the given OID; otherwise, returns false.
      • 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. getIOD() clones the object OID to ensure the object OID cannot be modified outside of this class.

        Returns:
        the cloned copy of the object OID.
      • toString

        public java.lang.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 "ncsa.hdf.object.h4.H4SDS".

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