Module org.hdfgroup.object

Package hdf.object.h4

Class H4Datatype

Object

hdf.object.HObject

hdf.object.Datatype

hdf.object.h4.H4Datatype

All Implemented Interfaces:

MetaDataContainer, Serializable

public class H4Datatype
extends Datatype

This class defines HDF4 data type characteristics and APIs for a data type.

This class provides several methods to convert an HDF4 datatype identifier to a datatype object, and vice versa. A datatype object is described by four basic fields: datatype class, size, byte order, and sign, while an HDF5 datatype is presented by a datatype identifier.

Version:

1.1 9/4/2007

Author:

Peter X. Cao

See Also:

Serialized Form

Field Summary

Fields inherited from class hdf.object.Datatype

arrayDims, baseType, CLASS_ARRAY, CLASS_BITFIELD, CLASS_CHAR, CLASS_COMPOUND, CLASS_ENUM, CLASS_FLOAT, CLASS_INTEGER, CLASS_NO_CLASS, CLASS_OPAQUE, CLASS_REFERENCE, CLASS_STRING, CLASS_TIME, CLASS_VLEN, compoundMemberNames, compoundMemberOffsets, compoundMemberTypes, datatypeClass, datatypeDescription, datatypeOrder, datatypeSign, datatypeSize, enumMembers, isNamed, isVariableStr, isVLEN, NATIVE, NSGN, ORDER_BE, ORDER_LE, ORDER_NONE, ORDER_VAX, SIGN_2, SIGN_NONE

Fields inherited from class hdf.object.HObject

fileFormat, linkTargetObjName, oid, SEPARATOR

Constructor Summary

Constructors

Constructor	Description
H4Datatype(int tclass, int tsize, int torder, int tsign)	Constructs a H4Datatype with specified class, size, byte order and sign.
H4Datatype(long nativeID)	Constructs a H4Datatype with a given native datatype identifier.

Method Summary

Modifier and Type	Method	Description
static Object	allocateArray(long datatype, int datasize)	Allocate a 1D array large enough to hold a multidimensional array of 'datasize' elements of 'datatype' numbers.
void	close(long id)	Closes a datatype identifier.
long	createNative()	Converts the datatype object to a native datatype.
void	fromNative(long tid)	Set datatype characteristics (class, size, byte order and sign) from a given datatype identifier.
String	getDescription()	Returns a short text description of this datatype.
List	getMetadata(int... attrPropList)
boolean	hasAttribute()	Check if the object has any attributes attached.
boolean	isText()
boolean	isUnsigned()	Checks if this datatype is unsigned.
static boolean	isUnsigned(long datatype)	Checks if the datatype is an unsigned integer.

Methods inherited from class hdf.object.Datatype

getArrayDims, getCompoundMemberNames, getCompoundMemberTypes, getDatatypeBase, getDatatypeClass, getDatatypeOrder, getDatatypeSign, getDatatypeSize, getEnumMembers, getEnumMembersAsString, getMetadata, isArray, isBitField, isChar, isCompound, isEnum, isFloat, isInteger, isNamed, isOpaque, isRef, isString, isVarStr, isVLEN, open, removeMetadata, setEnumMembers, toString, updateMetadata, writeMetadata

Methods inherited from class hdf.object.HObject

createFullname, debug, equals, equals, equalsOID, getFID, getFile, getFileFormat, getFullName, getLinkTargetObjName, getName, getOID, getPath, hashCode, setFullname, setLinkTargetObjName, setName, setPath

Methods inherited from class java.lang.Object

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

Constructor Details

H4Datatype

public H4Datatype(int tclass,
int tsize,
int torder,
int tsign)
           throws Exception

Constructs a H4Datatype with specified class, size, byte order and sign.

The following is a list of a few examples of H4Datatype:

1. to create unsigned native integer
   H4Datatype type = new H4Dataype(Datatype.CLASS_INTEGER, Datatype.NATIVE, Datatype.NATIVE, Datatype.SIGN_NONE);
2. to create 16-bit signed integer with big endian
   H4Datatype type = new H4Dataype(Datatype.CLASS_INTEGER, 2, Datatype.ORDER_BE, Datatype.NATIVE);
3. to create native float
   H4Datatype type = new H4Dataype(Datatype.CLASS_FLOAT, Datatype.NATIVE, Datatype.NATIVE, Datatype.NATIVE);
4. to create 64-bit double
   H4Datatype type = new H4Dataype(Datatype.CLASS_FLOAT, 8, Datatype.NATIVE, Datatype.NATIVE);

Parameters:

tclass - the class of the datatype, e.g. CLASS_INTEGER, CLASS_FLOAT and etc.

tsize - the size of the datatype in bytes, e.g. for a 32-bit integer, the size is 4. Valid values are NATIVE or a positive value.

torder - the byte order of the datatype. Valid values are ORDER_LE, ORDER_BE, ORDER_VAX, ORDER_NONE and NATIVE.

tsign - the sign of the datatype. Valid values are SIGN_NONE, SIGN_2 and NATIVE.

Throws:

Exception - if there is an error

H4Datatype

public H4Datatype(long nativeID)
           throws Exception

Constructs a H4Datatype with a given native datatype identifier.

For example,

 Datatype dtype = new H4Datatype(HDFConstants.DFNT_INT32);
 

will construct a datatype equivalent to

 new H4Datatype(Datatype.CLASS_INTEGER, 4, Datatype.NATIVE, Datatype.SIGN_NONE);
 

Parameters:

nativeID - the native datatype identifier.

Throws:

Exception - if there is an error

See Also:

fromNative(long nativeID)

Method Details

hasAttribute

public boolean hasAttribute()

Description copied from interface: MetaDataContainer

Check if the object has any attributes attached.

Returns:

true if it has any attributes, false otherwise.

fromNative

public void fromNative(long tid)

Description copied from class: Datatype

Set datatype characteristics (class, size, byte order and sign) from a given datatype identifier.

Sub-classes must implement it so that this datatype will be converted accordingly.

For example, if the type identifier is a 64-bit unsigned integer created from HDF5,

 H5Datatype dtype = new H5Datatype();
 dtype.fromNative(HDF5Constants.H5T_NATIVE_UNINT32);
 

Where dtype is equivalent to
new H5Datatype(CLASS_INTEGER, 4, NATIVE, SIGN_NONE);

Specified by:

fromNative in class Datatype

Parameters:

tid - the datatype identifier.

allocateArray

public static final Object allocateArray(long datatype,
int datasize)
                                  throws OutOfMemoryError

Allocate a 1D array large enough to hold a multidimensional array of 'datasize' elements of 'datatype' numbers.

Parameters:

datatype - the data type

datasize - the size of the data array

Returns:

an array of 'datasize' numbers of datatype.

Throws:

OutOfMemoryError - if the array cannot be allocated

getDescription

public String getDescription()

Description copied from class: Datatype

Returns a short text description of this datatype.

Overrides:

getDescription in class Datatype

Returns:

a short text description of this datatype

isUnsigned

public boolean isUnsigned()

Description copied from class: Datatype

Checks if this datatype is unsigned.

Overrides:

isUnsigned in class Datatype

Returns:

true if the datatype is unsigned; otherwise, returns false.

isUnsigned

public static final boolean isUnsigned(long datatype)

Checks if the datatype is an unsigned integer.

Parameters:

datatype - the data type.

Returns:

True is the datatype is an unsigned integer; otherwise returns false.

isText

public boolean isText()

Specified by:

isText in class Datatype

createNative

public long createNative()

Description copied from class: Datatype

Converts the datatype object to a native datatype. Subclasses must implement it so that this datatype will be converted accordingly. Use close() to close the native identifier; otherwise, the datatype will be left open.

For example, a HDF5 datatype created from

 H5Dataype dtype = new H5Datatype(CLASS_INTEGER, 4, NATIVE, SIGN_NONE);
 int tid = dtype.createNative();
 

The "tid" will be the HDF5 datatype id of a 64-bit unsigned integer, which is equivalent to

 int tid = H5.H5Tcopy(HDF5Constants.H5T_NATIVE_UNINT32);
 

Specified by:

createNative in class Datatype

Returns:

the identifier of the native datatype.

close

public void close(long id)

Description copied from class: Datatype

Closes a datatype identifier.

Sub-classes must replace this default implementation.

Specified by:

close in class Datatype

Parameters:

id - the datatype identifier to close.

getMetadata

public List getMetadata(int... attrPropList)
                 throws Exception

Throws:

Exception