Module org.hdfgroup.object
Package hdf.object.h5

# Class H5Datatype

Object
hdf.object.HObject
hdf.object.Datatype
hdf.object.h5.H5Datatype

All Implemented Interfaces:
  `MetaDataContainer`, `Serializable`

public class H5Datatype extends Datatype
This class defines HDF5 datatype characteristics and APIs for a data type.

This class provides several methods to convert an HDF5 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
  `H5Datatype​(int tclass, int tsize, int torder, int tsign)`
  Constructs a Datatype with specified class, size, byte order and sign.
  `H5Datatype​(int tclass, int tsize, int torder, int tsign, Datatype tbase)`
  Constructs a Datatype with specified class, size, byte order and sign.
  `H5Datatype​(int tclass, int tsize, int torder, int tsign, Datatype tbase, Datatype pbase)`
  Constructs a Datatype with specified class, size, byte order and sign.
  `H5Datatype​(FileFormat theFile, long nativeID)`
  Constructs a Datatype with a given native datatype identifier.
  `H5Datatype​(FileFormat theFile, long nativeID, Datatype pbase)`
  Constructs a Datatype with a given native datatype identifier.
  `H5Datatype​(FileFormat theFile, String name, String path)`
  Constructs an named HDF5 data type object for a given file, dataset name and group path.
  `H5Datatype​(FileFormat theFile, String name, String path, long[] oid)`
  Deprecated.
  Not for public use in the future.

- ## Method Summary

  Modifier and Type
  Method
  Description
  `static Object`
  `allocateArray​(H5Datatype dtype, int nPoints)`
  Allocates a one-dimensional array of byte, short, int, long, float, double, or String to store data in memory.
  `byte[]`
  `bigDecimalToByte​(int start, int len, BigDecimal[] data)`
  Convert from an array of BigDecimal into an array of bytes
  `byte[]`
  `bigDecimalToByte​(BigDecimal[] data, int start)`
  Convert from a single BigDecimal object from an array of BigDecimal into an array of bytes
  `BigDecimal`
  `byteToBigDecimal​(byte[] data, int start)`
  Convert 4 bytes from an array of bytes into a single BigDecimal
  `BigDecimal[]`
  `byteToBigDecimal​(int start, int len, byte[] data)`
  Convert a range from an array of bytes into an array of BigDecimal
  `void`
  `close​(long tid)`
  Closes a datatype identifier.
  `byte[]`
  `convertBigDecimalToByte​(BigDecimal num)`
  Convert a BigDecimal to a byte array .
  `BigDecimal`
  `convertByteToBigDecimal​(byte[] raw)`
  Convert byte array data to a BigDecimal.
  `Object[]`
  `convertEnumNameToValue​(String[] in)`
  Converts names in an Enumeration Datatype to values.
  `String[]`
  `convertEnumValueToName​(Object inValues)`
  Converts values in an Enumeration Datatype to names.
  `long`
  `createCompoundFieldType​(String memberName)`
  Creates a datatype of a compound with one field.
  `long`
  `createNative()`
  Converts the datatype object to a native datatype.
  `static void`
  `extractCompoundInfo​(H5Datatype dtype, String name, List<String> names, List<Datatype> flatListTypes)`
  Extracts compound information into flat structure.
  `void`
  `fromNative​(long tid)`
  Set datatype characteristics (class, size, byte order and sign) from a given datatype identifier.
  `static long`
  `getDatatypeSize​(long tid)`
  Returns the size (in bytes) of a given datatype identifier.
  `String`
  `getDescription()`
  Returns a short text description of this datatype.
  `List<Attribute>`
  `getMetadata()`
  Retrieves the object's metadata, such as attributes, from the file.
  `List<Attribute>`
  `getMetadata​(int... attrPropList)`
  `int`
  `getNativeStrPad()`
  `long`
  `getReferenceType()`
  If the datatype is a reference, then return the type.
  `boolean`
  `hasAttribute()`
  Check if the object has any attributes attached.
  `boolean`
  `isReference()`
  `boolean`
  `isRefObj()`
  `boolean`
  `isRegRef()`
  `boolean`
  `isText()`
  `static boolean`
  `isUnsigned​(long tid)`
  Checks if a datatype specified by the identifier is an unsigned integer.
  `long`
  `open()`
  Opens access to a named datatype.
  `void`
  `removeMetadata​(Object info)`
  Deletes an existing piece of metadata from this object.
  `void`
  `setFullname​(String newPath, String newName)`
  `void`
  `setName​(String newName)`
  Sets the name of the object.
  `static long`
  `toNative​(long tid)`
  `void`
  `writeMetadata​(Object info)`
  Writes a specific piece of metadata (such as an attribute) into the file.
  `static boolean`
  `zeroArrayCheck​(byte[] refarr)`
  Checks if a reference datatype is all zero.

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

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

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

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

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

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

- ## Constructor Details

  - ### H5Datatype

    public H5Datatype​(FileFormat theFile, String name, String path)
    Constructs an named HDF5 data type object for a given file, dataset name and group path.

    The datatype object represents an existing named datatype in file. For example,

         new H5Datatype(file, "dtype1", "/g0")

    constructs a datatype object that corresponds to the dataset,"dset1", at group "/g0".
    Parameters:
      `theFile` - the file that contains the datatype.
      `name` - the name of the dataset such as "dset1".
      `path` - the group path to the dataset such as "/g0/".

  - ### H5Datatype

    @Deprecated public H5Datatype​(FileFormat theFile, String name, String path, long[] oid)
    Deprecated.
    Not for public use in the future.
    Using `H5Datatype(FileFormat, String, String)`
    Parameters:
      `theFile` - the file that contains the datatype.
      `name` - the name of the dataset such as "dset1".
      `path` - the group path to the dataset such as "/g0/".
      `oid` - the oid of the dataset.

  - ### H5Datatype

    public H5Datatype​(int tclass, int tsize, int torder, int tsign) throws Exception
    Constructs a Datatype with specified class, size, byte order and sign.

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

    1. to create unsigned native integer
       H5Datatype type = new H5Dataype(Datatype.CLASS_INTEGER, Datatype.NATIVE, Datatype.NATIVE, Datatype.SIGN_NONE);
    2. to create 16-bit signed integer with big endian
       H5Datatype type = new H5Dataype(Datatype.CLASS_INTEGER, 2, Datatype.ORDER_BE, Datatype.NATIVE);
    3. to create native float
       H5Datatype type = new H5Dataype(Datatype.CLASS_FLOAT, Datatype.NATIVE, Datatype.NATIVE, Datatype.NATIVE);
    4. to create 64-bit double
       H5Datatype type = new H5Dataype(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. For string datatypes, -1 is also a valid value (to create a variable-length string).
      `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

  - ### H5Datatype

    public H5Datatype​(int tclass, int tsize, int torder, int tsign, Datatype tbase) throws Exception
    Constructs a Datatype with specified class, size, byte order and sign.

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

    1. to create unsigned native integer
       H5Datatype type = new H5Dataype(Datatype.CLASS_INTEGER, Datatype.NATIVE, Datatype.NATIVE, Datatype.SIGN_NONE);
    2. to create 16-bit signed integer with big endian
       H5Datatype type = new H5Dataype(Datatype.CLASS_INTEGER, 2, Datatype.ORDER_BE, Datatype.NATIVE);
    3. to create native float
       H5Datatype type = new H5Dataype(Datatype.CLASS_FLOAT, Datatype.NATIVE, Datatype.NATIVE, Datatype.NATIVE);
    4. to create 64-bit double
       H5Datatype type = new H5Dataype(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. For string datatypes, -1 is also a valid value (to create a variable-length string).
      `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.
      `tbase` - the base datatype of the new datatype
    Throws:
      `Exception` - if there is an error

  - ### H5Datatype

    public H5Datatype​(int tclass, int tsize, int torder, int tsign, Datatype tbase, Datatype pbase) throws Exception
    Constructs a Datatype with specified class, size, byte order and sign.

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

    1. to create unsigned native integer
       H5Datatype type = new H5Dataype(Datatype.CLASS_INTEGER, Datatype.NATIVE, Datatype.NATIVE, Datatype.SIGN_NONE);
    2. to create 16-bit signed integer with big endian
       H5Datatype type = new H5Dataype(Datatype.CLASS_INTEGER, 2, Datatype.ORDER_BE, Datatype.NATIVE);
    3. to create native float
       H5Datatype type = new H5Dataype(Datatype.CLASS_FLOAT, Datatype.NATIVE, Datatype.NATIVE, Datatype.NATIVE);
    4. to create 64-bit double
       H5Datatype type = new H5Dataype(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. For string datatypes, -1 is also a valid value (to create a variable-length string).
      `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.
      `tbase` - the base datatype of the new datatype
      `pbase` - the parent datatype of the new datatype
    Throws:
      `Exception` - if there is an error

  - ### H5Datatype

    public H5Datatype​(FileFormat theFile, long nativeID) throws Exception
    Constructs a Datatype with a given native datatype identifier.

    For example, if the datatype identifier is a 32-bit unsigned integer created from HDF5,

         int tid = H5.H5Tcopy(HDF5Constants.H5T_NATIVE_UNINT32);
         Datatype dtype = new Datatype(tid);

    will construct a datatype equivalent to new Datatype(Datatype.CLASS_INTEGER, 4, Datatype.NATIVE, Datatype.SIGN_NONE);
    Parameters:
      `theFile` - the file that contains the datatype.
      `nativeID` - the native datatype identifier.
    Throws:
      `Exception` - if there is an error
    See Also:
      `fromNative(long nativeID)`

  - ### H5Datatype

    public H5Datatype​(FileFormat theFile, long nativeID, Datatype pbase) throws Exception
    Constructs a Datatype with a given native datatype identifier.

    For example, if the datatype identifier is a 32-bit unsigned integer created from HDF5,

         int tid = H5.H5Tcopy(HDF5Constants.H5T_NATIVE_UNINT32);
         Datatype dtype = new Datatype(tid);

    will construct a datatype equivalent to new Datatype(Datatype.CLASS_INTEGER, 4, Datatype.NATIVE, Datatype.SIGN_NONE);
    Parameters:
      `theFile` - the file that contains the datatype.
      `nativeID` - the native datatype identifier.
      `pbase` - the parent datatype of the new datatype
    Throws:
      `Exception` - if there is an error
    See Also:
      `fromNative(long nativeID)`

- ## Method Details

  - ### open

    public long open()
    Opens access to a named datatype.

    It calls H5.H5Topen(loc, name).

    Overrides:
      `open` in class `Datatype`
    Returns:
      the datatype identifier if successful; otherwise returns negative value.
    See Also:
      `H5.H5Topen(long, String, long)`

  - ### close

    public void close​(long tid)
    Closes a datatype identifier.

    It calls H5.H5close(tid).

    Specified by:
      `close` in class `Datatype`
    Parameters:
      `tid` - the datatype ID to close

  - ### 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.

  - ### convertEnumValueToName

    public String[] convertEnumValueToName​(Object inValues) throws hdf.hdf5lib.exceptions.HDF5Exception
    Converts values in an Enumeration Datatype to names.

    This method searches the identified enumeration datatype for the values appearing in `inValues` and returns the names corresponding to those values. If a given value is not found in the enumeration datatype, the name corresponding to that value will be set to `"ENUM ERR value"` in the string array that is returned.

    If the method fails in general, null will be returned instead of a String array. An empty `inValues` parameter would cause general failure.

    Parameters:
      `inValues` - The array of enumerations values to be converted.
    Returns:
      The string array of names if successful; otherwise return null.
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception` - If there is an error at the HDF5 library level.

  - ### convertEnumNameToValue

    public Object[] convertEnumNameToValue​(String[] in) throws hdf.hdf5lib.exceptions.HDF5Exception
    Converts names in an Enumeration Datatype to values.

    This method searches the identified enumeration datatype for the names appearing in `inValues` and returns the values corresponding to those names.

    Parameters:
      `in` - The array of enumerations names to be converted.
    Returns:
      The int array of values if successful; otherwise return null.
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception` - If there is an error at the HDF5 library level.

  - ### bigDecimalToByte

    public byte[] bigDecimalToByte​(int start, int len, BigDecimal[] data)
    Convert from an array of BigDecimal into an array of bytes
    Parameters:
      `start` - The position in the input array of BigDecimal to start
      `len` - The number of 'BigDecimal' to convert
      `data` - The input array of BigDecimal
    Returns:
      an array of bytes

  - ### bigDecimalToByte

    public byte[] bigDecimalToByte​(BigDecimal[] data, int start)
    Convert from a single BigDecimal object from an array of BigDecimal into an array of bytes
    Parameters:
      `start` - The position in the input array of BigDecimal to start
      `data` - The input Float
    Returns:
      an array of bytes

  - ### convertBigDecimalToByte

    public byte[] convertBigDecimalToByte​(BigDecimal num)
    Convert a BigDecimal to a byte array .
    Parameters:
      `num` - The BigDecimal number to convert
    Returns:
      A byte array representing the BigDecimal.

  - ### byteToBigDecimal

    public BigDecimal[] byteToBigDecimal​(int start, int len, byte[] data)
    Convert a range from an array of bytes into an array of BigDecimal
    Parameters:
      `start` - The position in the input array of bytes to start
      `len` - The number of 'BigDecimal' to convert
      `data` - The input array of bytes
    Returns:
      an array of 'len' BigDecimal

  - ### byteToBigDecimal

    public BigDecimal byteToBigDecimal​(byte[] data, int start)
    Convert 4 bytes from an array of bytes into a single BigDecimal
    Parameters:
      `start` - The position in the input array of bytes to start
      `data` - The input array of bytes
    Returns:
      The BigDecimal value of the bytes.

  - ### convertByteToBigDecimal

    public BigDecimal convertByteToBigDecimal​(byte[] raw)
    Convert byte array data to a BigDecimal.
    Parameters:
      `raw` - The byte array to convert to a BigDecimal
    Returns:
      A BigDecimal representing the byte array.

  - ### 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.

  - ### toNative

    public static long toNative​(long tid)
    Parameters:
      `tid` - the datatype identification disk.
    Returns:
      the memory datatype identifier if successful, and negative otherwise.

  - ### 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.

  - ### allocateArray

    public static final Object allocateArray​(H5Datatype dtype, int nPoints) throws OutOfMemoryError
    Allocates a one-dimensional array of byte, short, int, long, float, double, or String to store data in memory. For example,

         long tid = H5.H5Tcopy(HDF5Constants.H5T_NATIVE_INT32);
         int[] data = (int[]) H5Datatype.allocateArray(datatype, 100);

    returns a 32-bit integer array of size 100.
    Parameters:
      `dtype` - the type.
      `nPoints` - the total number of data points of the array.
    Returns:
      the array object if successful; otherwise, return null.
    Throws:
      `OutOfMemoryError` - If there is a failure.

  - ### getDatatypeSize

    public static final long getDatatypeSize​(long tid)
    Returns the size (in bytes) of a given datatype identifier.

    It basically just calls H5Tget_size(tid).

    Parameters:
      `tid` - The datatype identifier.
    Returns:
      The size of the datatype in bytes.
    See Also:
      `H5.H5Tget_size(long)`

  - ### 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 static final boolean isUnsigned​(long tid)
    Checks if a datatype specified by the identifier is an unsigned integer.
    Parameters:
      `tid` - the datatype ID to be checked.
    Returns:
      true is the datatype is an unsigned integer; otherwise returns false.

  - ### getMetadata

    public List<Attribute> getMetadata() throws hdf.hdf5lib.exceptions.HDF5Exception
    Description copied from interface: `MetaDataContainer`
    Retrieves the object's metadata, such as attributes, from the file.

    Metadata, such as attributes, is stored in a List.

    Specified by:
      `getMetadata` in interface `MetaDataContainer`
    Overrides:
      `getMetadata` in class `Datatype`
    Returns:
      the list of metadata objects.
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception`

  - ### getMetadata

    public List<Attribute> getMetadata​(int... attrPropList) throws hdf.hdf5lib.exceptions.HDF5Exception
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception`

  - ### writeMetadata

    public void writeMetadata​(Object info) throws Exception
    Description copied from interface: `MetaDataContainer`
    Writes a specific piece of metadata (such as an attribute) into the file. If an HDF(4&5) attribute exists in the file, this method updates its value. If the attribute does not exist in the file, it creates the attribute in the file and attaches it to the object. It will fail to write a new attribute to the object where an attribute with the same name already exists. To update the value of an existing attribute in the file, one needs to get the instance of the attribute by getMetadata(), change its values, then use writeMetadata() to write the value.
    Specified by:
      `writeMetadata` in interface `MetaDataContainer`
    Overrides:
      `writeMetadata` in class `Datatype`
    Parameters:
      `info` - the metadata to write.
    Throws:
      `Exception` - if the metadata can not be written

  - ### removeMetadata

    public void removeMetadata​(Object info) throws hdf.hdf5lib.exceptions.HDF5Exception
    Description copied from interface: `MetaDataContainer`
    Deletes an existing piece of metadata from this object.
    Specified by:
      `removeMetadata` in interface `MetaDataContainer`
    Overrides:
      `removeMetadata` in class `Datatype`
    Parameters:
      `info` - the metadata to delete.
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception`

  - ### setName

    public void setName​(String newName) throws Exception
    Description copied from class: `HObject`
    Sets the name of the object. setName (String newName) changes the name of the object in the file.
    Overrides:
      `setName` in class `HObject`
    Parameters:
      `newName` - The new name of the object.
    Throws:
      `Exception` - if name is root or contains separator

  - ### setFullname

    public void setFullname​(String newPath, String newName) throws Exception
    Overrides:
      `setFullname` in class `HObject`
    Throws:
      `Exception`

  - ### isText

    public boolean isText()
    Specified by:
      `isText` in class `Datatype`

  - ### isRefObj

    public boolean isRefObj()

  - ### isRegRef

    public boolean isRegRef()

  - ### isReference

    public boolean isReference()

  - ### getReferenceType

    public long getReferenceType() throws hdf.hdf5lib.exceptions.HDF5Exception
    Description copied from class: `Datatype`
    If the datatype is a reference, then return the type.
    Overrides:
      `getReferenceType` in class `Datatype`
    Returns:
      the datatype reference type if successful; otherwise returns negative value.
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception`

  - ### zeroArrayCheck

    public static final boolean zeroArrayCheck​(byte[] refarr)
    Checks if a reference datatype is all zero.
    Parameters:
      `refarr` - the reference datatype data to be checked.
    Returns:
      true is the reference datatype data is all zero; otherwise returns false.

  - ### getNativeStrPad

    public int getNativeStrPad()

  - ### extractCompoundInfo

    public static void extractCompoundInfo​(H5Datatype dtype, String name, List<String> names, List<Datatype> flatListTypes)
    Extracts compound information into flat structure.

    For example, compound datatype "nest" has {nest1{a, b, c}, d, e} then extractCompoundInfo() will put the names of nested compound fields into a flat list as

         nest.nest1.a
         nest.nest1.b
         nest.nest1.c
         nest.d
         nest.e

    Parameters:
      `dtype` - the datatype to extract compound info from
      `name` - the name of the compound datatype
      `names` - the list to store the member names of the compound datatype
      `flatListTypes` - the list to store the nested member names of the compound datatype

  - ### createCompoundFieldType

    public long createCompoundFieldType​(String memberName) throws hdf.hdf5lib.exceptions.HDF5Exception
    Creates a datatype of a compound with one field.

    This function is needed to read/write data field by field.

    Parameters:
      `memberName` - The name of the datatype
    Returns:
      the identifier of the compound datatype.
    Throws:
      `hdf.hdf5lib.exceptions.HDF5Exception` - If there is an error at the HDF5 library level.