Introduction to HDF5 
HDF5 User Guide 
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And in this document, the HDF5 Reference Manual  
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H5S: Dataspace Interface

Dataspace Object API Functions

These functions create and manipulate the dataspace in which to store the elements of a dataset.

The C Interfaces:
  • H5Screate
  • H5Scopy
  • H5Sclose
  • H5Screate_simple
  • H5Sis_simple
  • H5Soffset_simple
  • H5Sget_simple_extent_dims
  • H5Sget_simple_extent_ndims
  •       
  • H5Sget_simple_extent_npoints
  • H5Sget_simple_extent_type
  • H5Sextent_copy
  • H5Sset_extent_simple
  • H5Sset_extent_none
  • H5Sget_select_npoints
  • H5Sget_select_hyper_nblocks
  • H5Sget_select_hyper_blocklist
  •       
  • H5Sget_select_elem_npoints
  • H5Sget_select_elem_pointlist
  • H5Sget_select_bounds
  • H5Sselect_elements
  • H5Sselect_all
  • H5Sselect_none
  • H5Sselect_valid
  • H5Sselect_hyperslab
  • The FORTRAN90 Interfaces:
    In general, each FORTRAN90 subroutine performs exactly the same task as the corresponding C function. The links below go to the C function descriptions, which serve as general descriptions for both. A button, under Non-C API(s) at the end of the C function description, opens an external browser window displaying the FORTRAN90-specific information. You will probably want to adjust the size and location of this external window so that both browser windows are visible and to facilitate moving easily between them.
  • h5screate_f
  • h5scopy_f
  • h5sclose_f
  • h5screate_simple_f
  • h5sis_simple_f
  • h5soffset_simple_f
  • h5sget_simple_extent_dims_f
  •       
  • h5sget_simple_extent_ndims_f
  • h5sget_simple_extent_npoints_f
  • h5sget_simple_extent_type_f
  • h5sextent_copy_f
  • h5sset_extent_simple_f
  • h5sset_extent_none_f
  • h5sget_select_npoints_f
  •       
  • h5sselect_elements_f
  • h5sselect_all_f
  • h5sselect_none_f
  • h5sselect_valid_f
  • h5sselect_hyperslab_f
  • The following H5S functions are included in the HDF5 specification, but have not yet been implemented. They are described in the The Dataspace Interface (H5S) section of the HDF5 User's Guide..
    • H5Scommit
    • H5Sis_subspace
    • H5Slock
          
    • H5Sopen
    • H5Sselect_op
    • H5Sselect_order
          
    • H5Ssubspace
    • H5Ssubspace_name
    • H5Ssubspace_location


    Name: H5Screate
    Signature:
    hid_t H5Screate(H5S_class_t type)
    Purpose:
    Creates a new dataspace of a specified type.
    Description:
    H5Screate creates a new dataspace of a particular type. The types currently supported are H5S_SCALAR and H5S_SIMPLE; others are planned to be added later.
    Parameters:
    H5S_class_t type
    The type of dataspace to be created.
    Returns:
    Returns a dataspace identifier if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Screate_simple
    Signature:
    hid_t H5Screate_simple(int rank, const hsize_t * dims, const hsize_t * maxdims )
    Purpose:
    Creates a new simple data space and opens it for access.
    Description:
    H5Screate_simple creates a new simple data space and opens it for access. The rank is the number of dimensions used in the dataspace. The dims argument is the size of the simple dataset and the maxdims argument is the upper limit on the size of the dataset. maxdims may be the null pointer in which case the upper limit is the same as dims. If an element of maxdims is zero then the corresponding dimension is unlimited, otherwise no element of maxdims should be smaller than the corresponding element of dims. The dataspace identifier returned from this function should be released with H5Sclose or resource leaks will occur.
    Parameters:
    int rank
    Number of dimensions of dataspace.
    const hsize_t * dims
    An array of the size of each dimension.
    const hsize_t * maxdims
    An array of the maximum size of each dimension.
    Returns:
    Returns a dataspace identifier if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Scopy
    Signature:
    hid_t H5Scopy(hid_t space_id )
    Purpose:
    Creates an exact copy of a dataspace.
    Description:
    H5Scopy creates a new dataspace which is an exact copy of the dataspace identified by space_id. The dataspace identifier returned from this function should be released with H5Sclose or resource leaks will occur.
    Parameters:
    hid_t space_id
    Identifier of dataspace to copy.
    Returns:
    Returns a dataspace identifier if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sselect_elements
    Signature:
    herr_t H5Sselect_elements(hid_t space_id, H5S_seloper_t op, const size_t num_elements, const hssize_t *coord[ ] )
    Purpose:
    Selects array elements to be included in the selection for a dataspace.
    Description:
    H5Sselect_elements selects array elements to be included in the selection for the space_id dataspace. The number of elements selected must be set with the num_elements. The coord array is a two-dimensional array of size dataspace rank by num_elements (ie. a list of coordinates in the array). The order of the element coordinates in the coord array also specifies the order in which the array elements are iterated through when I/O is performed. Duplicate coordinate locations are not checked for.

    The selection operator op determines how the new selection is to be combined with the previously existing selection for the dataspace. The following operators are supported:

    H5S_SELECT_SET Replaces the existing selection with the parameters from this call. Overlapping blocks are not supported with this operator.
    H5S_SELECT_OR Adds the new selection to the existing selection.
    When operators other than H5S_SELECT_SET are used to combine a new selection with an existing selection, the selection ordering is reset to 'C' array ordering.
    Parameters:
    hid_t space_id
    Identifier of the dataspace.
    H5S_seloper_t op
    operator specifying how the new selection is to be combined with the existing selection for the dataspace.
    const size_t num_elements
    Number of elements to be selected.
    const hssize_t *coord[ ]
    A 2-dimensional array specifying the coordinates of the elements being selected.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sselect_all
    Signature:
    herr_t H5Sselect_all(hid_t space_id)
    Purpose:
    Selects the entire dataspace.
    Description:
    H5Sselect_all selects the entire extent of the dataspace space_id.

    More specifically, H5Sselect_all selects the special 5S_SELECT_ALL region for the dataspace space_id. H5S_SELECT_ALL selects the entire dataspace for any dataspace it is applied to.

    Parameters:
    hid_t space_id
    IN: The identifier for the dataspace in which the selection is being made.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sselect_none
    Signature:
    herr_t H5Sselect_none(hid_t space_id)
    Purpose:
    Resets the selection region to include no elements.
    Description:
    H5Sselect_none resets the selection region for the dataspace space_id to include no elements.
    Parameters:
    hid_t space_id
    IN: The identifier for the dataspace in which the selection is being reset.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sselect_valid
    Signature:
    htri_t H5Sselect_valid(hid_t space_id)
    Purpose:
    Verifies that the selection is within the extent of the dataspace.
    Description:
    H5Sselect_valid verifies that the selection for the dataspace space_id is within the extent of the dataspace if the current offset for the dataspace is used.
    Parameters:
    hid_t space_id
    The identifier for the dataspace being queried.
    Returns:
    Returns a positive value, for TRUE, if the selection is contained within the extent or 0 (zero), for FALSE, if it is not. Returns a negative value on error conditions such as the selection or extent not being defined.
    Non-C API(s):

    Name: H5Sget_simple_extent_npoints
    Signature:
    hsize_t H5Sget_simple_extent_npoints(hid_t space_id)
    Purpose:
    Determines the number of elements in a dataspace.
    Description:
    H5Sget_simple_extent_npoints determines the number of elements in a dataspace. For example, a simple 3-dimensional dataspace with dimensions 2, 3, and 4 would have 24 elements.
    Parameters:
    hid_t space_id
    ID of the dataspace object to query
    Returns:
    Returns the number of elements in the dataspace if successful; otherwise returns 0.
    Non-C API(s):

    Name: H5Sget_select_npoints
    Signature:
    hssize_t H5Sget_select_npoints(hid_t space_id)
    Purpose:
    Determines the number of elements in a dataspace selection.
    Description:
    H5Sget_select_npoints determines the number of elements in the current selection of a dataspace.
    Parameters:
    hid_t space_id
    Dataspace identifier.
    Returns:
    Returns the number of elements in the selection if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sget_simple_extent_ndims
    Signature:
    int H5Sget_simple_extent_ndims(hid_t space_id)
    Purpose:
    Determines the dimensionality of a dataspace.
    Description:
    H5Sget_simple_extent_ndims determines the dimensionality (or rank) of a dataspace.
    Parameters:
    hid_t space_id
    Identifier of the dataspace
    Returns:
    Returns the number of dimensions in the dataspace if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sget_simple_extent_dims
    Signature:
    int H5Sget_simple_extent_dims(hid_t space_id, hsize_t *dims, hsize_t *maxdims )
    Purpose:
    Retrieves dataspace dimension size and maximum size.
    Description:
    H5Sget_simple_extent_dims returns the size and maximum sizes of each dimension of a dataspace through the dims and maxdims parameters.

    Either or both of dims and maxdims may be NULL.

    Parameters:
    hid_t space_id
    IN: Identifier of the dataspace object to query
    hsize_t *dims
    OUT: Pointer to array to store the size of each dimension.
    hsize_t *maxdims
    OUT: Pointer to array to store the maximum size of each dimension.
    Returns:
    Returns the number of dimensions in the dataspace if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sget_simple_extent_type
    Signature:
    H5S_class_t H5Sget_simple_extent_type(hid_t space_id)
    Purpose:
    Determine the current class of a dataspace.
    Description:
    H5Sget_simple_extent_type queries a dataspace to determine the current class of a dataspace.

    The function returns a class name, one of the following: H5S_SCALAR, H5S_SIMPLE, or H5S_NONE.

    Parameters:
    hid_t space_id
    Dataspace identifier.
    Returns:
    Returns a dataspace class name if successful; otherwise H5S_NO_CLASS (-1).
    Non-C API(s):

    Name: H5Sset_extent_simple
    Signature:
    herr_t H5Sset_extent_simple(hid_t space_id, int rank, const hsize_t *current_size, const hsize_t *maximum_size )
    Purpose:
    Sets or resets the size of an existing dataspace.
    Description:
    H5Sset_extent_simple sets or resets the size of an existing dataspace.

    rank is the dimensionality, or number of dimensions, of the dataspace.

    current_size is an array of size rank which contains the new size of each dimension in the dataspace. maximum_size is an array of size rank which contains the maximum size of each dimension in the dataspace.

    Any previous extent is removed from the dataspace, the dataspace type is set to H5S_SIMPLE, and the extent is set as specified.

    Parameters:
    hid_t space_id
    Dataspace identifier.
    int rank
    Rank, or dimensionality, of the dataspace.
    const hsize_t *current_size
    Array containing current size of dataspace.
    const hsize_t *maximum_size
    Array containing maximum size of dataspace.
    Returns:
    Returns a dataspace identifier if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sis_simple
    Signature:
    htri_t H5Sis_simple(hid_t space_id)
    Purpose:
    Determines whether a dataspace is a simple dataspace.
    Description:
    H5Sis_simple determines whether a dataspace is a simple dataspace. [Currently, all dataspace objects are simple dataspaces, complex dataspace support will be added in the future]
    Parameters:
    hid_t space_id
    Identifier of the dataspace to query
    Returns:
    When successful, returns a positive value, for TRUE, or 0 (zero), for FALSE. Otherwise returns a negative value.
    Non-C API(s):

    Name: H5Soffset_simple
    Signature:
    herr_t H5Soffset_simple(hid_t space_id, const hssize_t *offset )
    Purpose:
    Sets the offset of a simple dataspace.
    Description:
    H5Soffset_simple sets the offset of a simple dataspace space_id. The offset array must be the same number of elements as the number of dimensions for the dataspace. If the offset array is set to NULL, the offset for the dataspace is reset to 0.

    This function allows the same shaped selection to be moved to different locations within a dataspace without requiring it to be redefined.

    Parameters:
    hid_t space_id
    IN: The identifier for the dataspace object to reset.
    const hssize_t *offset
    IN: The offset at which to position the selection.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sextent_copy
    Signature:
    herr_t H5Sextent_copy(hid_t dest_space_id, hid_t source_space_id )
    Purpose:
    Copies the extent of a dataspace.
    Description:
    H5Sextent_copy copies the extent from source_space_id to dest_space_id. This action may change the type of the dataspace.
    Parameters:
    hid_t dest_space_id
    IN: The identifier for the dataspace to which the extent is copied.
    hid_t source_space_id
    IN: The identifier for the dataspace from which the extent is copied.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sset_extent_none
    Signature:
    herr_t H5Sset_extent_none(hid_t space_id)
    Purpose:
    Removes the extent from a dataspace.
    Description:
    H5Sset_extent_none removes the extent from a dataspace and sets the type to H5S_NO_CLASS.
    Parameters:
    hid_t space_id
    The identifier for the dataspace from which the extent is to be removed.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sselect_hyperslab
    Signature:
    herr_t H5Sselect_hyperslab(hid_t space_id, H5S_seloper_t op, const hssize_t *start, const hsize_t *stride, const hsize_t *count, const hsize_t *block )
    Purpose:
    Selects a hyperslab region to add to the current selected region.
    Description:
    H5Sselect_hyperslab selects a hyperslab region to add to the current selected region for the dataspace specified by space_id.

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

    The selection operator op determines how the new selection is to be combined with the already existing selection for the dataspace.

    The following operators are supported:

    H5S_SELECT_SET Replaces the existing selection with the parameters from this call. Overlapping blocks are not supported with this operator.
    H5S_SELECT_OR Adds the new selection to the existing selection.

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

    The stride array chooses array locations from the dataspace with each value in the stride array determining how many elements to move in each dimension. Setting a value in the stride array to 1 moves to each element in that dimension of the dataspace; setting a value of 2 in a location in the stride array moves to every other element in that dimension of the dataspace. In other words, the stride determines the number of elements to move from the start location in each dimension. Stride values of 0 are not allowed. If the stride parameter is NULL, a contiguous hyperslab is selected (as if each value in the stride array was set to all 1's).

    The count array determines how many blocks to select from the dataspace, in each dimension.

    The block array determines the size of the element block selected from the dataspace. If the block parameter is set to NULL, the block size defaults to a single element in each dimension (as if the block array was set to all 1's).

    For example, in a 2-dimensional dataspace, setting start to [1,1], stride to [4,4], count to [3,7], and block to [2,2] selects 21 2x2 blocks of array elements starting with location (1,1) and selecting blocks at locations (1,1), (5,1), (9,1), (1,5), (5,5), etc.

    Regions selected with this function call default to C order iteration when I/O is performed.

    Parameters:
    hid_t space_id
    IN: Identifier of dataspace selection to modify
    H5S_seloper_t op
    IN: Operation to perform on current selection.
    const hssize_t *start
    IN: Offset of start of hyperslab
    const hsize_t *count
    IN: Number of blocks included in hyperslab.
    const hsize_t *stride
    IN: Hyperslab stride.
    const hsize_t *block
    IN: Size of block in hyperslab.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Name: H5Sget_select_hyper_nblocks
    Signature:
    hssize_t H5Sget_select_hyper_nblocks(hid_t space_id )
    Purpose:
    Get number of hyperslab blocks.
    Description:
    H5Sget_select_hyper_nblocks returns the number of hyperslab blocks in the current dataspace selection.
    Parameters:
    hid_t space_id
    IN: Identifier of dataspace to query.
    Returns:
    Returns the number of hyperslab blocks in the current dataspace selection if successful. Otherwise returns a negative value.

    Name: H5Sget_select_hyper_blocklist
    Signature:
    herr_t H5Sget_select_hyper_blocklist(hid_t space_id, hsize_t startblock, hsize_t numblocks, hsize_t *buf )
    Purpose:
    Gets the list of hyperslab blocks currently selected.
    Description:
    H5Sget_select_hyper_blocklist returns a list of the hyperslab blocks currently selected. Starting with the startblock-th block in the list of blocks, numblocks blocks are put into the user's buffer. If the user's buffer fills up before numblocks blocks are inserted, the buffer will contain only as many blocks as fit.

    The block coordinates have the same dimensionality (rank) as the dataspace they are located within. The list of blocks is formatted as follows:
         <"start" coordinate>, immediately followed by
         <"opposite" corner coordinate>, followed by
         the next "start" and "opposite" coordinates,
         etc.
    until all of the selected blocks have been listed.

    No guarantee is implied as the order in which blocks are listed.

    Parameters:
    hid_t space_id
    IN: Dataspace identifier of selection to query.
    hsize_t startblock
    IN: Hyperslab block to start with.
    hsize_t numblocks
    IN: Number of hyperslab blocks to get.
    hsize_t *buf
    OUT: List of hyperslab blocks selected.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.

    Name: H5Sget_select_elem_npoints
    Signature:
    hssize_t H5Sget_select_elem_npoints(hid_t space_id )
    Purpose:
    Gets the number of element points in the current selection.
    Description:
    H5Sget_select_elem_npoints returns the number of element points in the current dataspace selection.
    Parameters:
    hid_t space_id
    IN: Identifier of dataspace to query.
    Returns:
    Returns the number of element points in the current dataspace selection if successful. Otherwise returns a negative value.

    Name: H5Sget_select_elem_pointlist
    Signature:
    herr_t H5Sget_select_elem_pointlist(hid_t space_id, hsize_t startpoint, hsize_t numpoints, hsize_t *buf )
    Purpose:
    Gets the list of element points currently selected.
    Description:
    H5Sget_select_elem_pointlist returns the list of element points in the current dataspace selection. Starting with the startpoint-th point in the list of points, numpoints points are put into the user's buffer. If the user's buffer fills up before numpoints points are inserted, the buffer will contain only as many points as fit.

    The element point coordinates have the same dimensionality (rank) as the dataspace they are located within. The list of element points is formatted as follows:
         <coordinate>, followed by
         the next coordinate,
         etc.
    until all of the selected element points have been listed.

    The points are returned in the order they will be iterated through when the selection is read/written from/to disk.

    Parameters:
    hid_t space_id
    IN: Dataspace identifier of selection to query.
    hsize_t startpoint
    IN: Element point to start with.
    hsize_t numpoints
    IN: Number of element points to get.
    hsize_t *buf
    OUT: List of element points selected.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.

    Name: H5Sget_select_bounds
    Signature:
    herr_t H5Sget_select_bounds(hid_t space_id, hsize_t *start, hsize_t *end )
    Purpose:
    Gets the bounding box containing the current selection.
    Description:
    H5Sget_select_bounds retrieves the coordinates of the bounding box containing the current selection and places them into user-supplied buffers.

    The start and end buffers must be large enough to hold the dataspace rank number of coordinates.

    The bounding box exactly contains the selection. I.e., if a 2-dimensional element selection is currently defined as containing the points (4,5), (6,8), and (10,7), then the bounding box will be (4, 5), (10, 8).

    The bounding box calculation includes the current offset of the selection within the dataspace extent.

    Calling this function on a none selection will return FAIL.

    Parameters:
    hid_t space_id
    IN: Identifier of dataspace to query.
    hsize_t *start
    OUT: Starting coordinates of the bounding box.
    hsize_t *end
    OUT: Ending coordinates of the bounding box, i.e., the coordinates of the diagonally opposite corner.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.

    Name: H5Sclose
    Signature:
    herr_t H5Sclose(hid_t space_id )
    Purpose:
    Releases and terminates access to a dataspace.
    Description:
    H5Sclose releases a dataspace. Further access through the dataspace identifier is illegal. Failure to release a dataspace with this call will result in resource leaks.
    Parameters:
    hid_t space_id
    Identifier of dataspace to release.
    Returns:
    Returns a non-negative value if successful; otherwise returns a negative value.
    Non-C API(s):

    Introduction to HDF5 
    HDF5 User Guide 
    Other HDF5 documents and links 
    And in this document, the HDF5 Reference Manual  
    H5   H5A   H5D   H5E   H5F   H5G   H5I   H5P  
    H5R   H5S   H5T   H5Z   Tools   Datatypes  

    HDF Help Desk
    Last modified: 12 June 2000
    Describes HDF5 Release 1.5, Unreleased Development Branch