Hyperslab Selections

Selecting a Portion of a Dataspace

Programming Example

Description

5 x 6 array:

		X	X	X	X
		X	X	X	X
		X	X	X	X

Then it reads the hyperslab from this file into a 2-dimensional plane (size 7 x 7) of a 3-dimensional array (size 7 x 7 x 3), as follows (with Dimension 0 offset by 3):

X	X	X	X
X	X	X	X
X	X	X	X

To obtain the example, download:

• H5Sselect_hyperslab / h5sselect_hyperslab_f selects a hyperslab region to add to the current selected region for a specified dataspace.

  C:

      herr_t H5Sselect_hyperslab (hid_t space_id, H5S_seloper_t operator,
          const hsize_t *start, const hsize_t *stride,
          const hsize_t *count, const hsize_t *block ) 
  

  FORTRAN:

      h5sselect_hyperslab_f (space_id, operator, start, count, &
                             hdferr, stride, block)
  
              space_id    IN: INTEGER(HID_T) 
              operator    IN: INTEGER 
              start       IN: INTEGER(HSIZE_T), DIMENSION(*)
              count       IN: INTEGER(HSIZE_T), DIMENSION(*)
              hdferr     OUT: INTEGER
              stride      IN: INTEGER(HSIZE_T), DIMENSION(*), OPTIONAL
              block       IN: INTEGER(HSIZE_T), DIMENSION(*), OPTIONAL 
  

  • The parameter space_id is the dataspace identifier for the specified dataspace.

  • The parameter operator can be set to one of the following:

    H5S_SELECT_SET (H5S_SELECT_SET_F in FORTRAN)

    Replace the existing selection with the parameters from this call. Overlapping blocks are not supported with this operator.

    H5S_SELECT_OR (H5S_SELECT_OR_F in FORTRAN)

    Add the new selection to the existing selection.

  • The start array determines the starting coordinates of the hyperslab to select.

  • The stride array indicates which elements along a dimension are to be selected.

  • The count array determines how many positions to select from the dataspace in each dimension.

  • The block array determines the size of the element block selected by the dataspace.

  • In C, a non-negative value is returned if successful, and a negative value otherwise. In FORTRAN, the return value is returned in hdferr: 0 if successful and -1 otherwise.

  The start, stride, count, and block arrays must be the same size as the rank of the dataspace.

• The examples introduce the following call:

  H5Dget_space / h5dget_space_f:

  Returns an identifier for a copy of the dataspace of a dataset.

• The C example also introduces the following calls:

  H5Sget_simple_extent_dims:

  Returns the size and maximum size of each dimension of a dataspace.

  H5Sget_simple_extent_ndims:

  Determines the dimensionality (or rank) of a dataspace.

  The FORTRAN example does not use these calls, though they are available as h5sget_simple_extent_dims_f and h5sget_simple_extent_ndims_f.