Module org.hdfgroup.object
Package hdf.object.h4

# Class H4File

Object
File
hdf.object.FileFormat
hdf.object.h4.H4File

All Implemented Interfaces:
  `Serializable`, `Comparable<File>`

public class H4File extends FileFormat
This class provides file level APIs. File access APIs include retrieving the file hierarchy, opening and closing file, and writing file content to disk.

Version:
  2.4 9/4/2007
Author:
  Peter X. Cao
See Also:
  Serialized Form

- ## Field Summary

  ### Fields inherited from class hdf.object.FileFormat

  `CREATE, fid, FILE_CREATE_DELETE, FILE_CREATE_EARLY_LIB, FILE_CREATE_OPEN, FILE_OBJ_SEP, FILE_TYPE_HDF4, FILE_TYPE_HDF5, FILE_TYPE_NC3, fullFileName, isReadOnly, OPEN_NEW, READ, WRITE`

  ### Fields inherited from class java.io.File

  `pathSeparator, pathSeparatorChar, separator, separatorChar`

- ## Constructor Summary

  Constructors
  Constructor
  Description
  `H4File()`
  Creates an H4File with read write access.
  `H4File​(String pathname)`
  Creates an H4File with read write access.
  `H4File​(String fileName, int access)`
  Creates an H4File instance with specified file name and access.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `void`
  `close()`
  Closes file associated with this instance.
  `HObject`
  `copy​(HObject srcObj, Group dstGroup, String dstName)`
  Copy an object to a group.
  `Datatype`
  `createDatatype​(int tclass, int tsize, int torder, int tsign)`
  Creates a new datatype in memory.
  `Datatype`
  `createDatatype​(int tclass, int tsize, int torder, int tsign, Datatype tbase)`
  Creates a new datatype in memory.
  `FileFormat`
  `createFile​(String filename, int createFlag)`
  Creates an HDF4 file with the specified name and returns a new H4File instance associated with the file.
  `Group`
  `createGroup​(String name, Group pgroup)`
  Creates a new group with specified name in existing group.
  `Dataset`
  `createImage​(String name, Group pgroup, Datatype type, long[] dims, long[] maxdims, long[] chunks, int gzip, int ncomp, int interlace, Object data)`
  Creates a new image in a file.
  `FileFormat`
  `createInstance​(String filename, int access)`
  Creates an H4File instance with specified file name and access.
  `Datatype`
  `createNamedDatatype​(Datatype tnative, String name)`
  Creates a named datatype in a file.
  `Dataset`
  `createScalarDS​(String name, Group pgroup, Datatype type, long[] dims, long[] maxdims, long[] chunks, int gzip, Object fillValue, Object data)`
  Creates a new dataset in a file with/without chunking/compression.
  `void`
  `delete​(HObject obj)`
  Delete an object from the file.
  `HObject`
  `get​(String path)`
  Get an individual HObject with a given path.
  `(package private) long`
  `getGRAccessID()`
  Returns the GR identifier, which is returned from GRstart(fid).
  `int`
  `getIndexOrder​(String strorder)`
  `int`
  `getIndexType​(String strtype)`
  `String`
  `getLibversion()`
  Returns the version of the HDF4 library.
  `HObject`
  `getRootObject()`
  Returns the root object for the file associated with this instance.
  `(package private) long`
  `getSDAccessID()`
  Returns the SDS identifier, which is returned from SDstart(fname, flag).
  `boolean`
  `isThisType​(FileFormat fileformat)`
  Checks if the given file format is an HDF4 file.
  `boolean`
  `isThisType​(String filename)`
  Checks if the given file is an HDF4 file or netCDF.
  `long`
  `open()`
  Opens file and returns a file identifier.
  `void`
  `setIndexOrder​(int indexOrder)`
  `void`
  `setIndexType​(int indexType)`
  `void`
  `setNewLibBounds​(String lowStr, String highStr)`
  Sets the bounds of new library versions.
  `void`
  `writeAttribute​(HObject obj, Attribute attr, boolean isSDglobalAttr)`
  Creates a new attribute and attaches it to the object if the attribute does not exist.

  ### Methods inherited from class hdf.object.FileFormat

  `addFileExtension, addFileFormat, copy, create, createCompoundDS, createCompoundDS, createGcpl, createGroup, createLink, createLink, createLink, createScalarDS, exportDataset, findObject, findObject, getFID, getFileExtensions, getFileFormat, getFileFormatKeys, getFileFormats, getFilePath, getHObject, getHObject, getIndexOrderValue, getIndexTypeValue, getInstance, getLibBounds, getLibBoundsDescription, getMaxMembers, getNumberOfMembers, getStartMembers, initLibBounds, isReadOnly, open, open, removeFileFormat, renameAttribute, setLibBounds, setMaxMembers, setStartMembers`

  ### Methods inherited from class java.io.File

  `canExecute, canRead, canWrite, compareTo, createNewFile, createTempFile, createTempFile, delete, deleteOnExit, equals, exists, getAbsoluteFile, getAbsolutePath, getCanonicalFile, getCanonicalPath, getFreeSpace, getName, getParent, getParentFile, getPath, getTotalSpace, getUsableSpace, hashCode, isAbsolute, isDirectory, isFile, isHidden, lastModified, length, list, list, listFiles, listFiles, listFiles, listRoots, mkdir, mkdirs, renameTo, setExecutable, setExecutable, setLastModified, setReadable, setReadable, setReadOnly, setWritable, setWritable, toPath, toString, toURI, toURL`

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

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

- ## Constructor Details

  - ### H4File

    public H4File()
    Creates an H4File with read write access.

  - ### H4File

    public H4File​(String pathname)
    Creates an H4File with read write access.
    Parameters:
      `pathname` - The file path string.

  - ### H4File

    public H4File​(String fileName, int access)
    Creates an H4File instance with specified file name and access.

    The access parameter values and corresponding behaviors:

    - READ: Read-only access; open() will fail if file doesn't exist.
    - WRITE: Read/Write access; if file doesn't exist, open() will create it; open() will fail if read/write access not allowed.
    - CREATE: Read/Write access; create a new file or truncate an existing one; open() will fail if file can't be created or if file exists but can't be opened read/write.

    This constructor does not open the file for access, nor does it confirm that the file can later be opened read/write or created.

    The flag returned by `FileFormat.isReadOnly()` is set to true if the access parameter value is READ, even though the file isn't yet open.

    Parameters:
      `fileName` - A valid file name, with a relative or absolute path.
      `access` - The file access flag, which determines behavior when file is opened. Acceptable values are `READ, WRITE,` and `CREATE`.
    Throws:
      `NullPointerException` - If the `fileName` argument is `null`.

- ## Method Details

  - ### isThisType

    public boolean isThisType​(FileFormat fileformat)
    Checks if the given file format is an HDF4 file.
    Specified by:
      `isThisType` in class `FileFormat`
    Parameters:
      `fileformat` - the fileformat to be checked.
    Returns:
      true if the given file is an HDF4 file; otherwise returns false.
    See Also:
      `FileFormat.isThisType(String)`

  - ### isThisType

    public boolean isThisType​(String filename)
    Checks if the given file is an HDF4 file or netCDF. HDF4 library supports netCDF version 2.3.2. It only supports SDS APIs.
    Specified by:
      `isThisType` in class `FileFormat`
    Parameters:
      `filename` - the file to be checked.
    Returns:
      true if the given file is an HDF4 file; otherwise returns false.
    See Also:
      `FileFormat.isThisType(FileFormat)`

  - ### createFile

    public FileFormat createFile​(String filename, int createFlag) throws Exception
    Creates an HDF4 file with the specified name and returns a new H4File instance associated with the file.
    Overrides:
      `createFile` in class `FileFormat`
    Parameters:
      `filename` - The filename; a pathname string.
      `createFlag` - The creation flag, which determines behavior when the file already exists. Acceptable values are `FILE_CREATE_DELETE` and `FILE_CREATE_OPEN`.
    Returns:
      the FileFormat instance.
    Throws:
      `hdf.hdflib.HDFException` - If the file cannot be created or if createFlag has unexpected value.
      `NullPointerException` - If the `filename` argument is `null`.
      `UnsupportedOperationException` - If the implementing class does not support the file creation operation.
      `Exception` - If the file cannot be created or if the creation flag has an unexpected value. The exceptions thrown vary depending on the implementing class.
    See Also:
      `FileFormat.createFile(java.lang.String, int)`, `H4File(String, int)`

  - ### createInstance

    public FileFormat createInstance​(String filename, int access) throws Exception
    Creates an H4File instance with specified file name and access.
    Specified by:
      `createInstance` in class `FileFormat`
    Parameters:
      `filename` - The filename; a pathname string.
      `access` - The file access flag, which determines behavior when file is opened. Acceptable values are `READ, WRITE,` and `CREATE`.
    Returns:
      the FileFormat instance.
    Throws:
      `NullPointerException` - If the `filename` argument is `null`.
      `Exception` - If the instance cannot be created or if the access flag has an unexpected value. The exceptions thrown vary depending on the implementing class.
    See Also:
      `FileFormat.createInstance(java.lang.String, int)`, `H4File(String, int)`

  - ### open

    public long open() throws Exception
    Description copied from class: `FileFormat`
    Opens file and returns a file identifier.

    This method uses the `filename` and `access` parameters specified in the createFile(), createInstance(), or getInstance() call to open the file. It returns the file identifier if successful, or a negative value in case of failure.

    The method also loads the file structure and basic information (name, type) for data objects in the file into the FileFormat instance. It does not load the contents of any data object.

    The structure of the file is stored in a tree starting from the root object.

    Specified by:
      `open` in class `FileFormat`
    Returns:
      File identifier if successful; otherwise -1.
    Throws:
      `Exception` - If the file cannot be opened. The exceptions thrown vary depending on the implementing class.
    See Also:
      `FileFormat.createFile(String, int)`, `FileFormat.createInstance(String, int)`, `FileFormat.getInstance(String)`, `FileFormat.getRootObject()`

  - ### close

    public void close() throws hdf.hdflib.HDFException
    Description copied from class: `FileFormat`
    Closes file associated with this instance. This method closes the file associated with this FileFormat instance, as well as all objects associated with the file.
    Specified by:
      `close` in class `FileFormat`
    Throws:
      `hdf.hdflib.HDFException`
    See Also:
      `FileFormat.open()`

  - ### getRootObject

    public HObject getRootObject()
    Description copied from class: `FileFormat`
    Returns the root object for the file associated with this instance.

    The root object is an HObject that represents the root group of a file. If the file has not yet been opened, or if there is no file associated with this instance, `null` will be returned.

    Starting from the root, applications can descend through the tree structure and navigate among the file's objects. In the tree structure, internal items represent non-empty groups. Leaf items represent datasets, named datatypes, or empty groups.

    Specified by:
      `getRootObject` in class `FileFormat`
    Returns:
      The root object of the file, or `null` if there is no associated file or if the associated file has not yet been opened.
    See Also:
      `FileFormat.open()`

  - ### createGroup

    public Group createGroup​(String name, Group pgroup) throws Exception
    Description copied from class: `FileFormat`
    Creates a new group with specified name in existing group.

    If the parent group is null, the new group will be created in the root group.

    Specified by:
      `createGroup` in class `FileFormat`
    Parameters:
      `name` - The name of the new group.
      `pgroup` - The parent group, or null.
    Returns:
      The new group if successful; otherwise returns null.
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### createDatatype

    public Datatype createDatatype​(int tclass, int tsize, int torder, int tsign) throws Exception
    Description copied from class: `FileFormat`
    Creates a new datatype in memory.

    The following code creates an instance of H5Datatype in memory.

         H5File file = (H5File) h5file.createInstance("test_hdf5.h5", FileFormat.WRITE);
         H5Datatype dtype = file.createDatatype(
                                     Datatype.CLASS_INTEGER,
                                     4,
                                     Datatype.NATIVE,
                                     Datatype.NATIVE);

    Specified by:
      `createDatatype` in class `FileFormat`
    Parameters:
      `tclass` - class of datatype, e.g. Datatype.CLASS_INTEGER
      `tsize` - size of the datatype in bytes, e.g. 4 for 32-bit integer.
      `torder` - order of the byte endian, e.g. Datatype.ORDER_LE.
      `tsign` - signed or unsigned of an integer, e.g. Datatype.SIGN_NONE.
    Returns:
      The new datatype object if successful; otherwise returns null.
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### createDatatype

    public Datatype createDatatype​(int tclass, int tsize, int torder, int tsign, Datatype tbase) throws Exception
    Description copied from class: `FileFormat`
    Creates a new datatype in memory.

    The following code creates an instance of H5Datatype in memory.

         H5File file = (H5File) h5file.createInstance("test_hdf5.h5", FileFormat.WRITE);
         H5Datatype dtype = file.createDatatype(
                                     Datatype.CLASS_INTEGER,
                                     4,
                                     Datatype.NATIVE,
                                     Datatype.NATIVE,
                                     basetype);

    Overrides:
      `createDatatype` in class `FileFormat`
    Parameters:
      `tclass` - class of datatype, e.g. Datatype.CLASS_INTEGER
      `tsize` - size of the datatype in bytes, e.g. 4 for 32-bit integer.
      `torder` - order of the byte endian, e.g. Datatype.ORDER_LE.
      `tsign` - signed or unsigned of an integer, e.g. Datatype.SIGN_NONE.
      `tbase` - the base datatype of the new datatype
    Returns:
      The new datatype object if successful; otherwise returns null.
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### createNamedDatatype

    public Datatype createNamedDatatype​(Datatype tnative, String name) throws Exception
    Description copied from class: `FileFormat`
    Creates a named datatype in a file.

    The following code creates a named datatype in a file.

         H5File file = (H5File) h5file.createInstance("test_hdf5.h5", FileFormat.WRITE);
         H5Datatype dtype = file.createNamedDatatype(
                                     nativetype,
                                     "Native Integer");

    Overrides:
      `createNamedDatatype` in class `FileFormat`
    Parameters:
      `tnative` - the native datatype of the new datatype
      `name` - name of the datatype to create, e.g. "Native Integer".
    Returns:
      The new datatype if successful; otherwise returns null.
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### createScalarDS

    public Dataset createScalarDS​(String name, Group pgroup, Datatype type, long[] dims, long[] maxdims, long[] chunks, int gzip, Object fillValue, Object data) throws Exception
    Description copied from class: `FileFormat`
    Creates a new dataset in a file with/without chunking/compression.

    The following example creates a 2D integer dataset of size 100X50 at the root group in an HDF5 file.

         String name = "2D integer";
         Group pgroup = (Group) getRootObject();
         Datatype dtype = new H5Datatype(Datatype.CLASS_INTEGER, // class
                 4, // size in bytes
                 Datatype.ORDER_LE, // byte order
                 Datatype.SIGN_NONE); // unsigned
         long[] dims = { 100, 50 };
         long[] maxdims = dims;
         long[] chunks = null; // no
         // chunking
         int gzip = 0; // no compression
         Object data = null; // no initial data values
         Dataset d = (H5File) file.createScalarDS(name, pgroup, dtype, dims, maxdims, chunks, gzip, data);

    Specified by:
      `createScalarDS` in class `FileFormat`
    Parameters:
      `name` - name of the new dataset, e.g. "2D integer"
      `pgroup` - parent group where the new dataset is created.
      `type` - datatype of the new dataset.
      `dims` - dimension sizes of the new dataset, e.g. long[] dims = {100, 50}.
      `maxdims` - maximum dimension sizes of the new dataset, null if maxdims is the same as dims.
      `chunks` - chunk sizes of the new dataset, null if no chunking.
      `gzip` - GZIP compression level (1 to 9), 0 or negative values if no compression.
      `fillValue` - default value.
      `data` - data written to the new dataset, null if no data is written to the new dataset.
    Returns:
      The new dataset if successful; otherwise returns null
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### createImage

    public Dataset createImage​(String name, Group pgroup, Datatype type, long[] dims, long[] maxdims, long[] chunks, int gzip, int ncomp, int interlace, Object data) throws Exception
    Description copied from class: `FileFormat`
    Creates a new image in a file.

    The following example creates a 2D image of size 100X50 in a root group.

         String name = "2D image";
         Group pgroup = (Group) getRootObject();
         Datatype dtype = new H5Datatype(Datatype.CLASS_INTEGER, 1, Datatype.NATIVE, Datatype.SIGN_NONE);
         long[] dims = {100, 50};
         long[] maxdims = dims;
         long[] chunks = null; // no chunking
         int gzip = 0; // no compression
         int ncomp = 3; // RGB true color image
         int interlace = ScalarDS.INTERLACE_PIXEL;
         Object data = null; // no initial data values
         Dataset d = (H5File) file.createScalarDS(name, pgroup, dtype, dims, maxdims, chunks, gzip, ncomp, interlace, data);

    Specified by:
      `createImage` in class `FileFormat`
    Parameters:
      `name` - name of the new image, "2D image".
      `pgroup` - parent group where the new image is created.
      `type` - datatype of the new image.
      `dims` - dimension sizes of the new dataset, e.g. long[] dims = {100, 50}.
      `maxdims` - maximum dimension sizes of the new dataset, null if maxdims is the same as dims.
      `chunks` - chunk sizes of the new dataset, null if no chunking.
      `gzip` - GZIP compression level (1 to 9), 0 or negative values if no compression.
      `ncomp` - number of components of the new image, e.g. int ncomp = 3; // RGB true color image.
      `interlace` - interlace mode of the image. Valid values are ScalarDS.INTERLACE_PIXEL, ScalarDS.INTERLACE_PLANEL and ScalarDS.INTERLACE_LINE.
      `data` - data value of the image, null if no data.
    Returns:
      The new image object if successful; otherwise returns null
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### delete

    public void delete​(HObject obj) throws Exception
    Delete an object from the file.
    Specified by:
      `delete` in class `FileFormat`
    Parameters:
      `obj` - the data object to delete.
    Throws:
      `Exception` - if the object can not be deleted

  - ### copy

    public HObject copy​(HObject srcObj, Group dstGroup, String dstName) throws Exception
    Copy an object to a group.
    Specified by:
      `copy` in class `FileFormat`
    Parameters:
      `srcObj` - the object to copy.
      `dstGroup` - the destination group.
      `dstName` - The name of the new object. If dstName is null, the name of srcObj will be used.
    Returns:
      the destination group, if the copy was successful, or null otherwise.
    Throws:
      `Exception` - if the object can not be copied

  - ### writeAttribute

    public void writeAttribute​(HObject obj, Attribute attr, boolean isSDglobalAttr) throws hdf.hdflib.HDFException
    Creates a new attribute and attaches it to the object if the attribute does not exist. Otherwise, just update the value of the attribute.
    Specified by:
      `writeAttribute` in class `FileFormat`
    Parameters:
      `obj` - the object which the attribute is to be attached to.
      `attr` - the attribute to attach.
      `isSDglobalAttr` - The indicator if the given attribute exists.
    Throws:
      `hdf.hdflib.HDFException` - if the attribute can not be written

  - ### getGRAccessID

    long getGRAccessID()
    Returns the GR identifier, which is returned from GRstart(fid).
    Returns:
      the identifier.

  - ### getSDAccessID

    long getSDAccessID()
    Returns the SDS identifier, which is returned from SDstart(fname, flag).
    Returns:
      the identifier.

  - ### getLibversion

    public String getLibversion()
    Returns the version of the HDF4 library.
    Specified by:
      `getLibversion` in class `FileFormat`
    Returns:
      The library version.

  - ### get

    public HObject get​(String path) throws Exception
    Get an individual HObject with a given path. It does not load the whole file structure.
    Specified by:
      `get` in class `FileFormat`
    Parameters:
      `path` - the path of the object
    Returns:
      The object if it exists in the file; otherwise `null`.
    Throws:
      `Exception` - if the object cannot be found

  - ### setNewLibBounds

    public void setNewLibBounds​(String lowStr, String highStr) throws Exception
    Description copied from class: `FileFormat`
    Sets the bounds of new library versions.
    Overrides:
      `setNewLibBounds` in class `FileFormat`
    Parameters:
      `lowStr` - The earliest version of the library.
      `highStr` - The latest version of the library.
    Throws:
      `Exception` - The exceptions thrown vary depending on the implementing class.

  - ### getIndexType

    public int getIndexType​(String strtype)
    Overrides:
      `getIndexType` in class `FileFormat`

  - ### setIndexType

    public void setIndexType​(int indexType)
    Overrides:
      `setIndexType` in class `FileFormat`

  - ### getIndexOrder

    public int getIndexOrder​(String strorder)
    Overrides:
      `getIndexOrder` in class `FileFormat`

  - ### setIndexOrder

    public void setIndexOrder​(int indexOrder)
    Overrides:
      `setIndexOrder` in class `FileFormat`