Dataset (HDFView 2.14)

Object
- hdf.object.HObject
- - hdf.object.Dataset

All Implemented Interfaces:

DataFormat, Serializable

Direct Known Subclasses:

CompoundDS, ScalarDS
```
public abstract class Dataset
extends HObject
```
The abstract class provides general APIs to create and manipulate dataset objects, and retrieve dataset properties, datatype and dimension sizes.
This class provides two convenient functions, read()/write(), to read/write data values. Reading/writing data may take many library calls if we use the library APIs directly. The read() and write functions hide all the details of these calls from users.
For more details on dataset, see HDF5 User's Guide

Version:

1.1 9/4/2007

Author:

Peter X. Cao

See Also:

ScalarDS, CompoundDS, Serialized Form

Field Summary

Fields
Modifier and Type	Field and Description
`protected long[]`	`chunkSize` The array of dimension sizes for a chunk.
`protected String`	`compression` The compression information.
`static String`	`compression_gzip_txt`
`protected boolean`	`convertByteToString` Flag to indicate if the byte[] array is converted to strings
`protected Object`	`convertedBuf` The array that holds the converted data of unsigned C-type integers.
`protected Object`	`data` The memory buffer that holds the raw data of the dataset.
`protected Datatype`	`datatype` The datatype object of the dataset.
`protected String[]`	`dimNames` Array of strings that represent the dimension names.
`protected long[]`	`dims` The current dimension sizes of the dataset
`protected boolean`	`enumConverted` Flag to indicate if the enum data is converted to strings.
`protected String`	`filters` The filters information.
`protected boolean`	`isDataLoaded` Flag to indicate if data values are loaded into memory.
`protected long[]`	`maxDims` The max dimension sizes of the dataset
`protected long`	`nPoints` The number of data points in the memory buffer.
`protected Object`	`originalBuf` The data buffer that contains the raw data directly reading from file (before any data conversion).
`protected int`	`rank` The number of dimensions of the dataset.
`protected long[]`	`selectedDims` Array that contains the number of data points selected (for read/write) in each dimension.
`protected int[]`	`selectedIndex` Array that contains the indices of the dimensions selected for display.
`protected long[]`	`selectedStride` The number of elements to move from the start location in each dimension.
`protected long[]`	`startDims` The starting position of each dimension of a selected subset.
`protected String`	`storage` The storage information.
`protected String`	`storage_layout` The storage layout information.

Fields inherited from class hdf.object.HObject
fileFormat, linkTargetObjName, oid, separator

Constructor Summary

Constructors
Constructor and Description
`Dataset(FileFormat theFile, String name, String path)` Constructs a Dataset object with a given file, name and path.
`Dataset(FileFormat theFile, String name, String path, long[] oid)` Deprecated. Not for public use in the future. Using `Dataset(FileFormat, String, String)`

Method Summary

All Methods Static Methods Instance Methods Abstract Methods Concrete Methods Deprecated Methods
Modifier and Type	Method and Description
`static String[]`	`byteToString(byte[] bytes, int length)` Converts an array of bytes into an array of Strings for a fixed string dataset.
`void`	`clear()` Clears memory held by the dataset, such as the data buffer.
`void`	`clearData()` Clears the current data buffer in memory and forces the next read() to load the data from file.
`static Object`	`convertFromUnsignedC(Object data_in)` Deprecated. Not for public use in the future. Using `convertFromUnsignedC(Object, Object)`
`static Object`	`convertFromUnsignedC(Object data_in, Object data_out)` Converts one-dimension array of unsigned C-type integers to a new array of appropriate Java integer in memory.
`static Object`	`convertToUnsignedC(Object data_in)` Deprecated. Not for public use in the future. Using `convertToUnsignedC(Object, Object)`
`static Object`	`convertToUnsignedC(Object data_in, Object data_out)` Converts the array of converted unsigned integers back to unsigned C-type integer data in memory.
`abstract Dataset`	`copy(Group pgroup, String name, long[] dims, Object data)` Creates a new dataset and writes the data buffer to the new dataset.
`long[]`	`getChunkSize()` Returns the array that contains the dimension sizes of the chunk of the dataset.
`String`	`getCompression()` Returns the string representation of compression information.
`boolean`	`getConvertByteToString()` Returns the flag that indicates if a byte array is converted to a string array.
`Object`	`getData()` Returns the data buffer of the dataset in memory.
`abstract Datatype`	`getDatatype()` Returns the datatype object of the dataset.
`String[]`	`getDimNames()` Returns the array of strings that represent the dimension names.
`long[]`	`getDims()` Returns the array that contains the dimension sizes of the dataset.
`String`	`getFilters()` Returns the string representation of filter information.
`int`	`getHeight()` Returns the dimension size of the vertical axis.
`long[]`	`getMaxDims()` Returns the array that contains the max dimension sizes of the dataset.
`Class`	`getOriginalClass()` Get Class of the original data buffer if converted.
`int`	`getRank()` Returns the rank (number of dimensions) of the dataset.
`long[]`	`getSelectedDims()` Returns the dimension sizes of the selected subset.
`int[]`	`getSelectedIndex()` Returns the indices of display order.
`int`	`getSize(int tid)` Returns the size in bytes of a given datatype.
`long[]`	`getStartDims()` Returns the starting position of a selected subset.
`String`	`getStorage()` Returns the string representation of storage information.
`String`	`getStorageLayout()` Returns the string representation of storage layout information.
`long[]`	`getStride()` Returns the selectedStride of the selected dataset.
`int`	`getWidth()` Returns the dimension size of the horizontal axis.
`abstract void`	`init()` Retrieves datatype and dataspace information from file and sets the dataset in memory.
`boolean`	`isEnumConverted()` Get flag that indicate if enum data is converted to strings.
`boolean`	`isString(int tid)` Checks if a given datatype is a string.
`abstract Object`	`read()` Reads the data from file.
`abstract byte[]`	`readBytes()` Reads the raw data of the dataset from file to a byte array.
`void`	`setConvertByteToString(boolean b)` Sets the flag that indicates if a byte array is converted to a string array.
`void`	`setData(Object d)` Deprecated. 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.
`void`	`setEnumConverted(boolean b)` Set flag that indicate if enum data is converted to strings.
`static byte[]`	`stringToByte(String[] strings, int length)` Converts a string array into an array of bytes for a fixed string dataset.
`void`	`write()` Writes the memory buffer of this dataset to file.
`abstract void`	`write(Object buf)` Writes a memory buffer to the dataset in file.

Methods inherited from class hdf.object.HObject
close, debug, equals, equalsOID, getFID, getFile, getFileFormat, getFullName, getLinkTargetObjName, getName, getOID, getPath, open, setLinkTargetObjName, setName, setPath, toString

Methods inherited from class Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

Methods inherited from interface hdf.object.DataFormat
getMetadata, hasAttribute, removeMetadata, updateMetadata, writeMetadata

Field Detail
- data
```
protected Object data
```
  The memory buffer that holds the raw data of the dataset.
- rank
```
protected int rank
```
  The number of dimensions of the dataset.
- dims
```
protected long[] dims
```
  The current dimension sizes of the dataset
- maxDims
```
protected long[] maxDims
```
  The max dimension sizes of the dataset
- selectedDims
```
protected long[] selectedDims
```
  Array that contains the number of data points selected (for read/write) in each dimension.
  The selected size must be less than or equal to the current dimension size. A subset of a rectangle selection is defined by the starting position and selected sizes.
  For example, if a 4 X 5 dataset is as follows:
```
     0,  1,  2,  3,  4
    10, 11, 12, 13, 14
    20, 21, 22, 23, 24
    30, 31, 32, 33, 34
 long[] dims = {4, 5};
 long[] startDims = {1, 2};
 long[] selectedDims = {3, 3};
 then the following subset is selected by the startDims and selectedDims above:
     12, 13, 14
     22, 23, 24
     32, 33, 34
 
```
- startDims
```
protected long[] startDims
```
  The starting position of each dimension of a selected subset. With both the starting position and selected sizes, the subset of a rectangle selection is fully defined.
- selectedIndex
```
protected final int[] selectedIndex
```
  Array that contains the indices of the dimensions selected for display.
  selectedIndex[] is provided for two purposes:
  1. selectedIndex[] is used to indicate the order of dimensions for display, i.e. selectedIndex[0] = row, selectedIndex[1] = column and selectedIndex[2] = depth. For example, for a four dimension dataset, if selectedIndex[] is {1, 2, 3}, then dim[1] is selected as row index, dim[2] is selected as column index and dim[3] is selected as depth index.
  2. selectedIndex[] is also used to select dimensions for display for datasets with three or more dimensions. We assume that applications such as HDFView can only display data up to three dimensions (a 2D spreadsheet/image with a third dimension that the 2D spreadsheet/image is cut from). For datasets with more than three dimensions, we need selectedIndex[] to store which three dimensions are chosen for display. For example, for a four dimension dataset, if selectedIndex[] = {1, 2, 3}, then dim[1] is selected as row index, dim[2] is selected as column index and dim[3] is selected as depth index. dim[0] is not selected. Its location is fixed at 0 by default.
- selectedStride
```
protected long[] selectedStride
```
  The number of elements to move from the start location in each dimension. For example, if selectedStride[0] = 2, every other data point is selected along dim[0].
- chunkSize
```
protected long[] chunkSize
```
  The array of dimension sizes for a chunk.
- compression
```
protected String compression
```
  The compression information.
- compression_gzip_txt
```
public static final String compression_gzip_txt
```
  See Also:
  
  Constant Field Values
- filters
```
protected String filters
```
  The filters information.
- storage_layout
```
protected String storage_layout
```
  The storage layout information.
- storage
```
protected String storage
```
  The storage information.
- datatype
```
protected Datatype datatype
```
  The datatype object of the dataset.
- dimNames
```
protected String[] dimNames
```
  Array of strings that represent the dimension names. It is null if dimension names do not exist.
- convertByteToString
```
protected boolean convertByteToString
```
  Flag to indicate if the byte[] array is converted to strings
- isDataLoaded
```
protected boolean isDataLoaded
```
  Flag to indicate if data values are loaded into memory.
- nPoints
```
protected long nPoints
```
  The number of data points in the memory buffer.
- originalBuf
```
protected Object originalBuf
```
  The data buffer that contains the raw data directly reading from file (before any data conversion).
- convertedBuf
```
protected Object convertedBuf
```
  The array that holds the converted data of unsigned C-type integers.
  For example, Suppose that the original data is an array of unsigned 16-bit short integers. Since Java does not support unsigned integer, the data is converted to an array of 32-bit singed integer. In that case, the converted buffer is the array of 32-bit singed integer.
- enumConverted
```
protected boolean enumConverted
```
  Flag to indicate if the enum data is converted to strings.

Constructor Detail
- Dataset
```
public Dataset(FileFormat theFile,
               String name,
               String path)
```
  Constructs a Dataset object with a given file, name and path.
  
  Parameters:
  
  theFile - the file that contains the dataset.
  
  name - the name of the Dataset, e.g. "dset1".
  
  path - the full group path of this Dataset, e.g. "/arrays/".
- Dataset
```
@Deprecated
public Dataset(FileFormat theFile,
                           String name,
                           String path,
                           long[] oid)
```
  Deprecated. Not for public use in the future.
  Using Dataset(FileFormat, String, String)
  
  Parameters:
  
  theFile - the file that contains the dataset.
  
  name - the name of the Dataset, e.g. "dset1".
  
  path - the full group path of this Dataset, e.g. "/arrays/".
  
  oid - the oid of this Dataset.

Method Detail

clear
```
public void clear()
```
Clears memory held by the dataset, such as the data buffer.

init
```
public abstract void init()
```
Retrieves datatype and dataspace information from file and sets the dataset in memory.
The init() is designed to support lazy operation in a dataset object. When a data object is retrieved from file, the datatype, dataspace and raw data are not loaded into memory. When it is asked to read the raw data from file, init() is first called to get the datatype and dataspace information, then load the raw data from file.
init() is also used to reset the selection of a dataset (start, stride and count) to the default, which is the entire dataset for 1D or 2D datasets. In the following example, init() at step 1) retrieves datatype and dataspace information from file. getData() at step 3) reads only one data point. init() at step 4) resets the selection to the whole dataset. getData() at step 4) reads the values of whole dataset into memory.
```
 dset = (Dataset) file.get(NAME_DATASET);

 // 1) get datatype and dataspace information from file
 dset.init();
 rank = dset.getRank(); // rank = 2, a 2D dataset
 count = dset.getSelectedDims();
 start = dset.getStartDims();
 dims = dset.getDims();

 // 2) select only one data point
 for (int i = 0; i < rank; i++) {
     start[0] = 0;
     count[i] = 1;
 }

 // 3) read one data point
 data = dset.getData();

 // 4) reset selection to the whole dataset
 dset.init();

 // 5) clean the memory data buffer
 dset.clearData();

 // 6) Read the whole dataset
 data = dset.getData();
 
```

getRank
```
public final int getRank()
```
Returns the rank (number of dimensions) of the dataset.

Returns:

the number of dimensions of the dataset.

getDims
```
public final long[] getDims()
```
Returns the array that contains the dimension sizes of the dataset.

Returns:

the dimension sizes of the dataset.

getMaxDims
```
public final long[] getMaxDims()
```
Returns the array that contains the max dimension sizes of the dataset.

Returns:

the max dimension sizes of the dataset.

getSelectedDims
```
public final long[] getSelectedDims()
```
Returns the dimension sizes of the selected subset.
The SelectedDims is the number of data points of the selected subset. Applications can use this array to change the size of selected subset. The selected size must be less than or equal to the current dimension size. Combined with the starting position, selected sizes and stride, the subset of a rectangle selection is fully defined.
For example, if a 4 X 5 dataset is as follows:
```
     0,  1,  2,  3,  4
    10, 11, 12, 13, 14
    20, 21, 22, 23, 24
    30, 31, 32, 33, 34
 long[] dims = {4, 5};
 long[] startDims = {1, 2};
 long[] selectedDims = {3, 3};
 long[] selectedStride = {1, 1};
 then the following subset is selected by the startDims and selectedDims
     12, 13, 14
     22, 23, 24
     32, 33, 34
 
```
Returns:

the dimension sizes of the selected subset.

getStartDims

public final long[] getStartDims()

Returns the starting position of a selected subset.

Applications can use this array to change the starting position of a selection. Combined with the selected dimensions, selected sizes and stride, the subset of a rectangle selection is fully defined.

For example, if a 4 X 5 dataset is as follows:

     0,  1,  2,  3,  4
    10, 11, 12, 13, 14
    20, 21, 22, 23, 24
    30, 31, 32, 33, 34
 long[] dims = {4, 5};
 long[] startDims = {1, 2};
 long[] selectedDims = {3, 3};
 long[] selectedStride = {1, 1};
 then the following subset is selected by the startDims and selectedDims
     12, 13, 14
     22, 23, 24
     32, 33, 34

Returns:: the starting position of a selected subset.

getStride
```
public final long[] getStride()
```
Returns the selectedStride of the selected dataset.
Applications can use this array to change how many elements to move in each dimension. Combined with the starting position and selected sizes, the subset of a rectangle selection is defined.
For example, if a 4 X 5 dataset is as follows:
```
     0,  1,  2,  3,  4
    10, 11, 12, 13, 14
    20, 21, 22, 23, 24
    30, 31, 32, 33, 34
 long[] dims = {4, 5};
 long[] startDims = {0, 0};
 long[] selectedDims = {2, 2};
 long[] selectedStride = {2, 3};
 then the following subset is selected by the startDims and selectedDims
     0,   3
     20, 23
 
```
Returns:

the selectedStride of the selected dataset.

setConvertByteToString
```
public final void setConvertByteToString(boolean b)
```
Sets the flag that indicates if a byte array is converted to a string array.
In a string dataset, the raw data from file is stored in a byte array. By default, this byte array is converted to an array of strings. For a large dataset (e.g. more than one million strings), the conversion takes a long time and requires a lot of memory space to store the strings. In some applications, such a conversion can be delayed. For example, A GUI application may convert only the part of the strings that is visible to the users, not the entire data array.
setConvertByteToString(boolean b) allows users to set the flag so that applications can choose to perform the byte-to-string conversion or not. If the flag is set to false, the getData() returns an array of byte instead of an array of strings.

Parameters:

b - convert bytes to strings if b is true; otherwise, if false, do not convert bytes to strings.

getConvertByteToString
```
public final boolean getConvertByteToString()
```
Returns the flag that indicates if a byte array is converted to a string array.

Returns:

true if byte array is converted to string; otherwise, returns false if there is no conversion.

read
```
public abstract 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.
How to Select a Subset
A selection is specified by three arrays: start, stride and count.
1. start: offset of a selection
2. stride: determines how many elements to move in each dimension
3. count: number of elements to select in each dimension
getStartDims(), getStride() and getSelectedDims() returns the start, stride and count arrays respectively. Applications can make a selection by changing the values of the arrays.
The following example shows how to make a subset. In the example, the dataset is a 4-dimensional array 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 point in dims[1] and dims[2]
```
 int rank = dataset.getRank(); // number of dimensions of the dataset
 long[] dims = dataset.getDims(); // the dimension sizes of the dataset
 long[] selected = dataset.getSelectedDims(); // the selected size of the dataset
 long[] start = dataset.getStartDims(); // the offset 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 < rank; i++) {
     start[i] = 0;
     selected[i] = 1;
     stride[i] = 1;
 }

 // set stride to 2 on dim1 and dim2 so that every other data point is
 // selected.
 stride[1] = 2;
 stride[2] = 2;

 // set the selection size of dim1 and dim2
 selected[1] = dims[1] / stride[1];
 selected[2] = dims[1] / stride[2];

 // when dataset.getData() is called, the selection above will be used since
 // the dimension arrays are passed by reference. Changes of these arrays
 // outside the dataset object directly change the values of these array
 // in the dataset object.
 
```
For ScalarDS, the memory data buffer is a one-dimensional array of byte, short, int, float, double or String type based on the datatype of the dataset.
For CompoundDS, the memory data object is an java.util.List object. Each element of the list is a data array that corresponds to a compound field.
For example, if compound dataset "comp" has the following nested structure, and member datatypes
```
 comp --> m01 (int)
 comp --> m02 (float)
 comp --> nest1 --> m11 (char)
 comp --> nest1 --> m12 (String)
 comp --> nest1 --> nest2 --> m21 (long)
 comp --> nest1 --> nest2 --> m22 (double)
 
```
getData() returns a list of six arrays: {int[], float[], char[], String[], long[] and double[]}.
Returns:

the data read from file.

Throws:

Exception - if object can not be read

OutOfMemoryError - if memory is exhausted

See Also:

getData()

readBytes
```
public abstract byte[] readBytes()
                          throws Exception
```
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.

Returns:

the byte array of the raw data.

Throws:

Exception - if data can not be read

write
```
public abstract void write(Object buf)
                    throws Exception
```
Writes a memory buffer to the dataset in file.

Parameters:

buf - the data to write

Throws:

Exception - if data can not be written

write
```
public final void write()
                 throws Exception
```
Writes the memory buffer of this dataset to file.

Throws:

Exception - if buffer can not be written

copy
```
public abstract Dataset copy(Group pgroup,
                             String name,
                             long[] dims,
                             Object data)
                      throws Exception
```
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.

Parameters:

pgroup - the group which the dataset is copied to.

name - the name of the new dataset.

dims - the dimension sizes of the the new dataset.

data - the data values of the subset to be copied.

Returns:

the new dataset.

Throws:

Exception - if dataset can not be copied

getDatatype
```
public abstract Datatype getDatatype()
```
Returns the datatype object of the dataset.

Returns:

the datatype object of the dataset.

getData
```
public final Object getData()
                     throws Exception,
                            OutOfMemoryError
```
Returns the data buffer of the dataset in memory.
If data is already loaded into memory, returns the data; otherwise, calls read() to read data from file into a memory buffer and returns the memory buffer.
By default, the whole dataset is read into memory. Users can also select a subset to read. Subsetting is done in an implicit way.
How to Select a Subset
A selection is specified by three arrays: start, stride and count.
1. start: offset of a selection
2. stride: determines how many elements to move in each dimension
3. count: number of elements to select in each dimension
getStartDims(), getStride() and getSelectedDims() returns the start, stride and count arrays respectively. Applications can make a selection by changing the values of the arrays.
The following example shows how to make a subset. In the example, the dataset is a 4-dimensional array 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 point in dims[1] and dims[2]
```
 int rank = dataset.getRank(); // number of dimensions 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 offset 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 < rank; i++) {
     start[i] = 0;
     selected[i] = 1;
     stride[i] = 1;
 }

 // set stride to 2 on dim1 and dim2 so that every other data point is
 // selected.
 stride[1] = 2;
 stride[2] = 2;

 // set the selection size of dim1 and dim2
 selected[1] = dims[1] / stride[1];
 selected[2] = dims[1] / stride[2];

 // when dataset.getData() is called, the selection above will be used since
 // the dimension arrays are passed by reference. Changes of these arrays
 // outside the dataset object directly change the values of these array
 // in the dataset object.
 
```
For ScalarDS, the memory data buffer is a one-dimensional array of byte, short, int, float, double or String type based on the datatype of the dataset.
For CompoundDS, the memory data object is an java.util.List object. Each element of the list is a data array that corresponds to a compound field.
For example, if compound dataset "comp" has the following nested structure, and member datatypes
```
 comp --> m01 (int)
 comp --> m02 (float)
 comp --> nest1 --> m11 (char)
 comp --> nest1 --> m12 (String)
 comp --> nest1 --> nest2 --> m21 (long)
 comp --> nest1 --> nest2 --> m22 (double)
 
```
getData() returns a list of six arrays: {int[], float[], char[], String[], long[] and double[]}.
Returns:

the memory buffer of the dataset.

Throws:

Exception - if object can not be read

OutOfMemoryError - if memory is exhausted

setData
```
@Deprecated
public final void setData(Object d)
```
Deprecated. 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.

Parameters:

d - the object data

clearData
```
public void clearData()
```
Clears the current data buffer in memory and forces the next read() to load the data from file.
The function read() loads data from file into memory only if the data is not read. If data is already in memory, read() just returns the memory buffer. Sometimes we want to force read() to re-read data from file. For example, when the selection is changed, we need to re-read the data.

See Also:

getData(), read()

getHeight
```
public final int getHeight()
```
Returns the dimension size of the vertical axis.
This function is used by GUI applications such as HDFView. GUI applications display a dataset in a 2D table or 2D image. The display order is specified by the index array of selectedIndex as follow:

selectedIndex[0] -- height

The vertical axis

selectedIndex[1] -- width

The horizontal axis

selectedIndex[2] -- depth

The depth axis is used for 3 or more dimensional datasets.

Applications can use getSelectedIndex() to access and change the display order. For example, in a 2D dataset of 200x50 (dim0=200, dim1=50), the following code will set the height=200 and width=50.
```
 int[] selectedIndex = dataset.getSelectedIndex();
 selectedIndex[0] = 0;
 selectedIndex[1] = 1;
 
```
Returns:

the size of dimension of the vertical axis.

See Also:

getSelectedIndex(), getWidth()

getWidth
```
public final int getWidth()
```
Returns the dimension size of the horizontal axis.
This function is used by GUI applications such as HDFView. GUI applications display a dataset in 2D Table or 2D Image. The display order is specified by the index array of selectedIndex as follow:

selectedIndex[0] -- height

The vertical axis

selectedIndex[1] -- width

The horizontal axis

selectedIndex[2] -- depth

The depth axis, which is used for 3 or more dimension datasets.

Applications can use getSelectedIndex() to access and change the display order. For example, in a 2D dataset of 200x50 (dim0=200, dim1=50), the following code will set the height=200 and width=100.
```
 int[] selectedIndex = dataset.getSelectedIndex();
 selectedIndex[0] = 0;
 selectedIndex[1] = 1;
 
```
Returns:

the size of dimension of the horizontal axis.

See Also:

getSelectedIndex(), getHeight()

getSelectedIndex
```
public final int[] getSelectedIndex()
```
Returns the indices of display order.
selectedIndex[] is provided for two purposes:
1. selectedIndex[] is used to indicate the order of dimensions for display. selectedIndex[0] is for the row, selectedIndex[1] is for the column and selectedIndex[2] for the depth.
  For example, for a four dimension dataset, if selectedIndex[] = {1, 2, 3}, then dim[1] is selected as row index, dim[2] is selected as column index and dim[3] is selected as depth index.
2. selectedIndex[] is also used to select dimensions for display for datasets with three or more dimensions. We assume that applications such as HDFView can only display data values up to three dimensions (2D spreadsheet/image with a third dimension which the 2D spreadsheet/image is selected from). For datasets with more than three dimensions, we need selectedIndex[] to tell applications which three dimensions are chosen for display.
  For example, for a four dimension dataset, if selectedIndex[] = {1, 2, 3}, then dim[1] is selected as row index, dim[2] is selected as column index and dim[3] is selected as depth index. dim[0] is not selected. Its location is fixed at 0 by default.
Returns:

the array of the indices of display order.

getCompression
```
public final String getCompression()
```
Returns the string representation of compression information.
For example, "SZIP: Pixels per block = 8: H5Z_FILTER_CONFIG_DECODE_ENABLED".

Returns:

the string representation of compression information.

getFilters
```
public final String getFilters()
```
Returns the string representation of filter information.

Returns:

the string representation of filter information.

getStorageLayout
```
public final String getStorageLayout()
```
Returns the string representation of storage layout information.

Returns:

the string representation of storage layout information.

getStorage
```
public final String getStorage()
```
Returns the string representation of storage information.

Returns:

the string representation of storage information.

getChunkSize
```
public final long[] getChunkSize()
```
Returns the array that contains the dimension sizes of the chunk of the dataset. Returns null if the dataset is not chunked.

Returns:

the array of chunk sizes or returns null if the dataset is not chunked.

convertFromUnsignedC
```
@Deprecated
public static Object convertFromUnsignedC(Object data_in)
```
Deprecated. Not for public use in the future.
Using convertFromUnsignedC(Object, Object)

Parameters:

data_in - the object data

Returns:

the converted object

convertFromUnsignedC

public static Object convertFromUnsignedC(Object data_in,
                                          Object data_out)

Converts one-dimension array of unsigned C-type integers to a new array of appropriate Java integer in memory.

Since Java does not support unsigned integer, values of unsigned C-type integers must be converted into its appropriate Java integer. Otherwise, the data value will not displayed correctly. For example, if an unsigned C byte, x = 200, is stored into an Java byte y, y will be -56 instead of the correct value of 200.

Unsigned C integers are upgrade to Java integers according to the following table:

**Mapping Unsigned C Integers to Java Integers**
Unsigned C Integer	JAVA Integer
unsigned byte	signed short
unsigned short	signed int
unsigned int	signed long
unsigned long	signed long

NOTE: this conversion cannot deal with unsigned 64-bit integers. Therefore, the values of unsigned 64-bit datasets may be wrong in Java applications.

If memory data of unsigned integers is converted by convertFromUnsignedC(), convertToUnsignedC() must be called to convert the data back to unsigned C before data is written into file.

Parameters:: data_in - the input 1D array of the unsigned C-type integers.; data_out - the output converted (or upgraded) 1D array of Java integers.
Returns:: the upgraded 1D array of Java integers.
See Also:: convertToUnsignedC(Object, Object)

convertToUnsignedC
```
@Deprecated
public static Object convertToUnsignedC(Object data_in)
```
Deprecated. Not for public use in the future.
Using convertToUnsignedC(Object, Object)

Parameters:

data_in - the input 1D array of the unsigned C-type integers.

Returns:

the upgraded 1D array of Java integers.

convertToUnsignedC
```
public static Object convertToUnsignedC(Object data_in,
                                        Object data_out)
```
Converts the array of converted unsigned integers back to unsigned C-type integer data in memory.
If memory data of unsigned integers is converted by convertFromUnsignedC(), convertToUnsignedC() must be called to convert the data back to unsigned C before data is written into file.

Parameters:

data_in - the input array of the Java integer.

data_out - the output array of the unsigned C-type integer.

Returns:

the converted data of unsigned C-type integer array.

See Also:

convertFromUnsignedC(Object, Object)

byteToString
```
public static final String[] byteToString(byte[] bytes,
                                          int length)
```
Converts an array of bytes into an array of Strings for a fixed string dataset.
A C-string is an array of chars while an Java String is an object. When a string dataset is read into a Java application, the data is stored in an array of Java bytes. byteToString() is used to convert the array of bytes into an array of Java strings so that applications can display and modify the data content.
For example, the content of a two element C string dataset is {"ABC", "abc"}. Java applications will read the data into a byte array of {65, 66, 67, 97, 98, 99). byteToString(bytes, 3) returns an array of Java String of strs[0]="ABC", and strs[1]="abc".
If memory data of strings is converted to Java Strings, stringToByte() must be called to convert the memory data back to byte array before data is written to file.

Parameters:

bytes - the array of bytes to convert.

length - the length of string.

Returns:

the array of Java String.

See Also:

stringToByte(String[], int)

stringToByte
```
public static final byte[] stringToByte(String[] strings,
                                        int length)
```
Converts a string array into an array of bytes for a fixed string dataset.
If memory data of strings is converted to Java Strings, stringToByte() must be called to convert the memory data back to byte array before data is written to file.

Parameters:

strings - the array of string.

length - the length of string.

Returns:

the array of bytes.

See Also:

byteToString(byte[] bytes, int length)

getDimNames
```
public final String[] getDimNames()
```
Returns the array of strings that represent the dimension names. Returns null if there is no dimension name.
Some datasets have pre-defined names for each dimension such as "Latitude" and "Longitude". getDimNames() returns these pre-defined names.

Returns:

the names of dimensions, or null if there is no dimension name.

isString
```
public boolean isString(int tid)
```
Checks if a given datatype is a string. Sub-classes must replace this default implementation.

Parameters:

tid - The data type identifier.

Returns:

true if the datatype is a string; otherwise returns false.

getSize
```
public int getSize(int tid)
```
Returns the size in bytes of a given datatype. Sub-classes must replace this default implementation.

Parameters:

tid - The data type identifier.

Returns:

The size of the datatype

getOriginalClass
```
public final Class getOriginalClass()
```
Get Class of the original data buffer if converted.

Returns:

the Class of originalBuf

isEnumConverted
```
public boolean isEnumConverted()
```
Get flag that indicate if enum data is converted to strings.

Returns:

the enumConverted

setEnumConverted
```
public void setEnumConverted(boolean b)
```
Set flag that indicate if enum data is converted to strings.

Parameters:

b - the enumConverted to set

Class Dataset

Field Summary

Fields inherited from class hdf.object.HObject

Constructor Summary

Method Summary

Methods inherited from class hdf.object.HObject

Methods inherited from class Object

Methods inherited from interface hdf.object.DataFormat

Field Detail

data

rank

dims

maxDims

selectedDims

startDims

selectedIndex

selectedStride

chunkSize

compression

compression_gzip_txt

filters

storage_layout

storage

datatype

dimNames

convertByteToString

isDataLoaded

nPoints

originalBuf

convertedBuf

enumConverted

Constructor Detail

Dataset

Dataset

Method Detail

clear

init

getRank

getDims

getMaxDims

getSelectedDims

getStartDims

getStride

setConvertByteToString

getConvertByteToString

read

readBytes

write

write

copy

getDatatype

getData

setData

clearData

getHeight

getWidth

getSelectedIndex

getCompression

getFilters

getStorageLayout

getStorage

getChunkSize

convertFromUnsignedC

convertFromUnsignedC

convertToUnsignedC

convertToUnsignedC

byteToString

stringToByte

getDimNames

isString

getSize

getOriginalClass

isEnumConverted

setEnumConverted