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## ncsa.hdf.object.h4
Class H4Datatype

    java.lang.Object
      ncsa.hdf.object.HObject
          ncsa.hdf.object.Datatype
              ncsa.hdf.object.h4.H4Datatype

All Implemented Interfaces:
  java.io.Serializable, DataFormat

    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 ncsa.hdf.object.Datatype
`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_VLEN, datatypeClass, datatypeOrder, datatypeSign, datatypeSize, dims, enumMembers, NATIVE, NSGN, ORDER_BE, ORDER_LE, ORDER_NONE, ORDER_VAX, SIGN_2, SIGN_NONE`

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

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

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

Methods inherited from class ncsa.hdf.object.Datatype
`getBasetype, getDatatypeClass, getDatatypeOrder, getDatatypeSign, getDatatypeSize, getEnumMembers, getMetadata, open, removeMetadata, setEnumMembers, writeMetadata`

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

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait`

Constructor Detail

### H4Datatype

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

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

  The following is a list of a few example of H5Datatype.

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

  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.
    `torder` - the byte order of the datatype. Valid values are ORDER_LE, ORDER_BE, ORDER_VAX and ORDER_NONE
    `tsign` - the sign of the datatype. Valid values are SIGN_NONE, SIGN_2 and MSGN

### H4Datatype

    public H4Datatype(int nativeID)

  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(CLASS_INTEGER, 4, NATIVE, SIGN_NONE);

  Parameters:
    `nativeID` - the native datatype identifier.
  See Also:
    `fromNative(int nativeID)`

Method Detail

### hasAttribute

    public boolean hasAttribute()

  Description copied from interface: `DataFormat`
  Check if the object has any attributes attached.

  Returns:
    true if it has any attribute(s), false otherwise.

### fromNative

    public void fromNative(int tid)

  Description copied from class: `Datatype`
  Set datatype characteristics (class, size, byte order and sign) from a given datatye identifier.

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

  For example, if the type identifier is a 32-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 java.lang.Object allocateArray(int datatype,
                                                       int datasize)
                                                throws java.lang.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:
    `java.lang.OutOfMemoryError`

### getDatatypeDescription

    public java.lang.String getDatatypeDescription()

  Description copied from class: `Datatype`
  Returns a short text description of this datatype.

  Overrides:
    `getDatatypeDescription` in class `Datatype`
  Returns:
    a short text description of this datatype

### getDatatypeDescription

    public static final java.lang.String getDatatypeDescription(int datatype)

  Returns the short description of a given datatype.

### isUnsigned

    public boolean isUnsigned()

  Description copied from class: `Datatype`
  Checks if this datatype is an unsigned integer.

  Specified by:
    `isUnsigned` in class `Datatype`
  Returns:
    true if the datatype is an unsigned integer; otherwise, returns false.

### isUnsigned

    public static final boolean isUnsigned(int 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.

### toNative

    public int toNative()

  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.toNative();

  There "tid" will be the HDF5 datatype id of a 32-bit unsigned integer, which is equivalent to

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

  Specified by:
    `toNative` in class `Datatype`
  Returns:
    the identifier of the native datatype.

### close

    public void close(int id)

  Description copied from class: `Datatype`
  Closes a datatype identifier.

  Sub-clases must replace this default implementation.

  Specified by:
    `close` in class `Datatype`
  Parameters:
    `id` - the datatype identifier to close.

### getMetadata

    public java.util.List getMetadata(int... attrPropList)
                               throws java.lang.Exception

  Throws:
    `java.lang.Exception`

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