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H5: General Library Functions

These functions serve general-purpose needs of the HDF5 library and it users.

The C Interfaces:
             

Alphabetical Listing
             

The FORTRAN90 Interfaces:
In general, each FORTRAN90 subroutine performs exactly the same task as the corresponding C function.
             

Name: H5check_version
Signature:
herr_t H5check_version(unsigned majnum, unsigned minnum, unsigned relnum )
Purpose:
Verifies that library versions are consistent.
Description:
H5check_version verifies that the arguments provided with the function call match the version numbers compiled into the library.

H5check_version serves two slightly differing purposes.

First, the function is intended to be called by the user to verify that the version of the header files compiled into an application matches the version of the HDF5 library being used. One may look at the H5check definition in the file H5public.h as an example.

Due to the risks of data corruption or segmentation faults, H5check_version causes the application to abort if the version numbers do not match. The abort is achieved by means of a call to the standard C function abort().

Note that H5check_version verifies only the major and minor version numbers and the release number; it does not verify the sub-release value as that should be an empty string for any official release. This means that any two incompatible library versions must have different {major,minor,release} numbers. (Notice the reverse is not necessarily true.)

Secondarily, H5check_version verifies that the library version identifiers H5_VERS_MAJOR, H5_VERS_MINOR, H5_VERS_RELEASE, H5_VERS_SUBRELEASE, and H5_VERS_INFO are consistent. This is designed to catch source code inconsistencies, but does not generate the fatal error as in the first stage because this inconsistency does not cause errors in the data files. If this check reveals inconsistencies, the library issues a warning but the function does not fail.

Parameters:
Returns:
Returns a non-negative value if successful. Upon failure, this function causes the application to abort.
Fortran90 Interface: h5check_version_f 
SUBROUTINE h5check_version_f(hdferr) 
  IMPLICIT NONE
  INTEGER, INTENT(IN)  :: majnum      ! The major version of the library
  INTEGER, INTENT(IN)  :: minnum      ! The minor version of the library
  INTEGER, INTENT(IN)  :: relnum      ! The release number 
  INTEGER, INTENT(OUT) :: hdferr      ! Error code

END SUBROUTINE h5check_version_f
History:
Name: H5close
Signature:
herr_t H5close(void)
Purpose:
Flushes all data to disk, closes file identifiers, and cleans up memory.
Description:
H5close flushes all data to disk, closes all file identifiers, and cleans up all memory used by the library. This function is generally called when the application calls exit(), but may be called earlier in event of an emergency shutdown or out of desire to free all resources used by the HDF5 library.

h5close_f and h5open_f are required calls in Fortran90 applications.

Parameters:
None.
Returns:
Returns a non-negative value if successful; otherwise returns a negative value.
Fortran90 Interface: h5close_f 
SUBROUTINE h5close_f(hdferr) 
  IMPLICIT NONE
  INTEGER, INTENT(OUT) :: hdferr      ! Error code

END SUBROUTINE h5close_f
Name: H5dont_atexit
Signature:
herr_t H5dont_atexit(void)
Purpose:
Instructs library not to install atexit cleanup routine.
Description:
H5dont_atexit indicates to the library that an atexit() cleanup routine should not be installed. The major purpose for this is in situations where the library is dynamically linked into an application and is un-linked from the application before exit() gets called. In those situations, a routine installed with atexit() would jump to a routine which was no longer in memory, causing errors.

In order to be effective, this routine must be called before any other HDF function calls, and must be called each time the library is loaded/linked into the application (the first time and after it's been un-loaded).

Parameters:
None.
Returns:
Returns a non-negative value if successful; otherwise returns a negative value.
Fortran90 Interface: h5dont_atexit_f 
SUBROUTINE h5dont_atexit_f(hdferr) 
  IMPLICIT NONE
  INTEGER, INTENT(OUT) :: hdferr      ! Error code

END SUBROUTINE h5dont_atexit_f
History:
Name: H5garbage_collect
Signature:
herr_t H5garbage_collect(void)
Purpose:
Garbage collects on all free-lists of all types.
Description:
H5garbage_collect walks through all the garbage collection routines of the library, freeing any unused memory.

It is not required that H5garbage_collect be called at any particular time; it is only necessary in certain situations where the application has performed actions that cause the library to allocate many objects. The application should call H5garbage_collect if it eventually releases those objects and wants to reduce the memory used by the library from the peak usage required.

The library automatically garbage collects all the free lists when the application ends.

Parameters:
None.
Returns:
Returns a non-negative value if successful; otherwise returns a negative value.
Fortran90 Interface: h5garbage_collect_f 
SUBROUTINE h5garbage_collect_f(hdferr) 
  IMPLICIT NONE
  INTEGER, INTENT(OUT) :: hdferr      ! Error code

END SUBROUTINE h5garbage_collect_f
History:
Name: H5get_libversion
Signature:
herr_t H5get_libversion(unsigned *majnum, unsigned *minnum, unsigned *relnum )
Purpose:
Returns the HDF library release number.
Description:
H5get_libversion retrieves the major, minor, and release numbers of the version of the HDF library which is linked to the application.
Parameters:
Returns:
Returns a non-negative value if successful; otherwise returns a negative value.
Fortran90 Interface: h5get_libversion_f 
SUBROUTINE h5get_libversion_f(hdferr) 
  IMPLICIT NONE
  INTEGER, INTENT(OUT) :: majnum      ! The major version of the library
  INTEGER, INTENT(OUT) :: minnum      ! The minor version of the library
  INTEGER, INTENT(OUT) :: relnum      ! The release number 
  INTEGER, INTENT(OUT) :: hdferr      ! Error code

END SUBROUTINE h5get_libversion_f
History:
Name: H5open
Signature:
herr_t H5open(void)
Purpose:
Initializes the HDF5 library.
Description:
H5open initialize the library.

When the HDF5 Library is employed in a C application, this function is normally called automatically, but if you find that an HDF5 library function is failing inexplicably, try calling this function first. If you wish to elimnate this possibility, it is safe to routinely call H5open before an application starts working with the library as there are no damaging side-effects in calling it more than once.

When the HDF5 Library is employed in a Fortran90 application, h5open_f initializes global variables (e.g. predefined types) and performs other tasks required to initialize the library. h5open_f and h5close_f are therefore required calls in Fortran90 applications.

Parameters:
None.
Returns:
Returns a non-negative value if successful; otherwise returns a negative value.
Fortran90 Interface: h5open_f 
SUBROUTINE h5open_f(hdferr) 
  IMPLICIT NONE
  INTEGER, INTENT(OUT) :: hdferr      ! Error code

END SUBROUTINE h5open_f
Name: H5set_free_list_limits
Signature:
herr_t H5set_free_list_limits(int reg_global_lim, int reg_list_lim, int arr_global_lim, int arr_list_lim, int blk_global_lim, int blk_list_lim )
Purpose:
Sets free-list size limits.
Description:
H5set_free_list_limits sets size limits on all types of free lists. The HDF5 library uses free lists internally to manage memory. There are three types of free lists: Alternate phrasing?:

These are global limits, but each limit applies only to free lists of the specified type. Therefore, if an application sets a 1Mb limit on each of the global lists, up to 3Mb of total storage might be allocated, 1Mb for each of the regular, array, and block type lists.

Using a value of -1 for a limit means that no limit is set for the specified type of free list.

Parameters:
Returns:
Returns a non-negative value if successful; otherwise returns a negative value.
Fortran90 Interface:
None.
History:
HDF5 documents and links 
Introduction to HDF5 
HDF5 User Guide 
 And in this document, the HDF5 Reference Manual  
H5   H5A   H5D   H5E   H5F   H5G   H5I   H5P  
H5R   H5S   H5T   H5Z   Tools   Datatypes  
(PDF of complete manual formatted as print volume)   
THG Help Desk:
Describes HDF5 Release 1.6.7, January 2008