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H5T_GET_NATIVE_TYPE

Returns the native datatype identifier of a specified datatype

Procedure:

H5T_GET_NATIVE_TYPE (dtype_id, direction)

Signature:

hid_t H5Tget_native_type( hid_t dtype_id, H5T_direction_t direction )

SUBROUTINE h5tget_native_type_f(dtype_id, direction, native_dtype_id, hdferr)
  IMPLICIT NONE
  INTEGER(HID_T), INTENT(IN) :: dtype_id  
                                    ! Datatype identifier
  INTEGER, INTENT(IN) :: direction  ! Direction of search:
                                    ! H5T_DIR_ASCEND_F = 1 in inscendent order
                                    ! H5T_DIR_DESCEND_F= 2 in descendent order
  INTEGER(HID_T), INTENT(OUT) :: native_dtype_id  
                                    ! The native datatype identifier
  INTEGER, INTENT(OUT) :: hdferr    ! Error code:
                                    ! 0 on success and -1 on failure
END SUBROUTINE h5tget_native_type_f

Parameters:
hid_t dtype_idIN: Datatype identifier for the dataset datatype
H5T_direction_t direction    IN: Direction of search

Description:

H5T_GET_NATIVE_TYPE returns the equivalent native datatype identifier (or handle) for the datatype specified in dtype_id.

H5T_GET_NATIVE_TYPE is designed primarily to facilitate use of the H5D_READ function, for which users otherwise must undertake a multi-step process to determine the native datatype of a dataset prior to reading it into memory. This function can be used for the following purposes:

  • To determine the native datatype of an atomic datatype
  • To determine the base datatype of an array, enumerated, or variable-length datatype
  • To determine the native atomic datatypes of the individual components of a compound datatype

For example, if dtype_id is a compound datatype, the returned datatype identifier will be for a similar compound datatype with each element converted to the corresponding native datatype; nested compound datatypes will be unwound. If dtype_id is an array, the returned datatype identifier will be for the native datatype of a single array element.

H5T_GET_NATIVE_TYPE selects the first matching native datatype from the following list:

        H5T_NATIVE_CHAR         
        H5T_NATIVE_SHORT        
        H5T_NATIVE_INT          
        H5T_NATIVE_LONG         
        H5T_NATIVE_LLONG        

        H5T_NATIVE_UCHAR
        H5T_NATIVE_USHORT
        H5T_NATIVE_UINT
        H5T_NATIVE_ULONG
        H5T_NATIVE_ULLONG

        H5T_NATIVE_FLOAT
        H5T_NATIVE_DOUBLE
        H5T_NATIVE_LDOUBLE

        H5T_NATIVE_B8
        H5T_NATIVE_B16
        H5T_NATIVE_B32
        H5T_NATIVE_B64

The direction parameter indicates the order in which the library searches for a native datatype match. Valid values for direction are as follows:

H5T_DIR_ASCENDSearches the above list in ascending size of the datatype,
i.e., from top to bottom. (Default)
H5T_DIR_DESCEND  Searches the above list in descending size of the datatype,
i.e., from bottom to top.

H5T_GET_NATIVE_TYPE is designed primarily for use with integer, floating point, and bitfield datatypes. String, time, opaque, and reference datatypes are returned as a copy of dtype_id. See above for compound, array, enumerated, and variable-length datatypes.

The identifier returned by H5T_GET_NATIVE_TYPE should eventually be closed by calling H5T_CLOSE to release resources.

Datatype Identifiers

Please note that a datatype is actually an object identifier or handle returned from opening the datatype. It is not persistent and its value can be different from one HDF5 session to the next.

H5T_EQUAL can be used to compare datatypes.

HDF5 High Level APIs that may also be of interest are:

Returns:

Returns the native datatype identifier (or handle) for the specified dataset datatype if successful; otherwise returns a negative value.

Example:

Coming Soon!

History:
Release    Change
1.6.0Function introduced in this release.

--- Last Modified: October 25, 2019 | 08:41 AM