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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.
             

Last modified: 30 July 2010
Name: H5check_version
Signature:
herr_t H5check_version( unsigned majnum, unsigned minnum, unsigned relnum )

Purpose:
Verifies that HDF5 library versions are consistent.

Description:
H5check_version verifies that the version of the HDF5 library with which an application was compiled, as indicated by the passed parameters, matches the version of the HDF5 library against which the application is currently linked.

majnum is the major version number of the HDF library with which the application was compiled, minnum is the minor version number, and relnum is the release number. Consider the following illustration:

An official HDF5 release is labelled as follows:
     HDF5 Release <majnum>.<minnum>.<relnum>
For example, in HDF5 Release 1.8.5:
  • 1 is the major version number, majnum.
  • 8 is the minor version number, minnum.
  • 5 is the release number, relnum.

As stated above, H5check_version first verifies that the version of the HDF5 library with which an application was compiled matches the version of the HDF5 library against which the application is currently linked. If this check fails, H5check_version causes the application to abort (by means of a standard C abort() call) and prints information that is usually useful for debugging. This precaution is is taken to avoid the risks of data corruption or segmentation faults.

The most common cause of this failure is that an application was compiled with one version of HDF5 and is dynamically linked with a different version different version.

If the above test passes, H5check_version proceeds to verify the consistency of additional library version information. This is designed to catch source code inconsistencies that do not normally cause failures; if this check reveals an inconsistency, an informational warning is printed but the application is allowed to run.

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:
Last modified: 24 July 2009
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(majnum, minnum, relnum, 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
Last modified: 6 May 2010
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. The types of free lists used are as follows:

The parameters specify global and per-list limits; for example, reg_global_limit and reg_list_limit limit the accumulated size of all regular free lists and the size of each individual regular free list, respectively. 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  
Collective Calls in Parallel  
(PDF of complete manual formatted as print volume)   
The HDF Group Help Desk:
Describes HDF5 Release 1.6.10, November 2009