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HDF5
1.15.0.fc88fcd
API Reference
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Use the functions in this module to manage the life cycle of HDF5 library instances.
Create | Read |
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herr_t H5is_library_threadsafe(hbool_t *is_ts) Determines whether the HDF5 library was built with the thread-safety feature enabled. herr_t H5get_libversion(unsigned *majnum, unsigned *minnum, unsigned *relnum) Returns the HDF library release number. | |
Update | Delete |
60 if (H5set_free_list_limits(512 * 1024, 32 * 1024, 2048 * 1024, 128 * 1024, 8192 * 1024, 512 * 1024) <
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) Sets free-list size limits. | herr_t H5atclose(H5_atclose_func_t func, void *ctx) Registers a callback for the library to invoke when it's closing. |
Functions | |
herr_t | H5open (void) |
Initializes the HDF5 library. More... | |
herr_t | H5atclose (H5_atclose_func_t func, void *ctx) |
Registers a callback for the library to invoke when it's closing. More... | |
herr_t | H5close (void) |
Flushes all data to disk, closes all open objects, and releases memory. More... | |
herr_t | H5dont_atexit (void) |
Instructs library not to install atexit() cleanup routine. More... | |
herr_t | H5garbage_collect (void) |
Garbage collects on all free-lists of all types. More... | |
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) |
Sets free-list size limits. More... | |
herr_t | H5get_free_list_sizes (size_t *reg_size, size_t *arr_size, size_t *blk_size, size_t *fac_size) |
Gets the current size of the free lists used to manage memory. More... | |
herr_t | H5get_libversion (unsigned *majnum, unsigned *minnum, unsigned *relnum) |
Returns the HDF library release number. More... | |
herr_t | H5check_version (unsigned majnum, unsigned minnum, unsigned relnum) |
Verifies that HDF5 library versions are consistent. More... | |
herr_t | H5is_library_terminating (hbool_t *is_terminating) |
Checks whether the HDF5 library is closing. More... | |
herr_t | H5is_library_threadsafe (hbool_t *is_ts) |
Determines whether the HDF5 library was built with the thread-safety feature enabled. More... | |
herr_t | H5free_memory (void *mem) |
Frees memory allocated by the HDF5 library. More... | |
void * | H5allocate_memory (size_t size, hbool_t clear) |
Allocates memory that will be freed later internally. More... | |
void * | H5resize_memory (void *mem, size_t size) |
Resizes and, if required, re-allocates memory that will later be freed internally by the HDF5 library. More... | |
void* H5allocate_memory | ( | size_t | size, |
hbool_t | clear | ||
) |
Allocates memory that will be freed later internally.
[in] | size | The size in bytes of the buffer to be allocated |
[in] | clear | Flag whether the new buffer is to be initialized with 0 |
H5allocate_memory() allocates a memory buffer of size bytes that will later be freed internally by the HDF5 library.
The boolean clear
parameter specifies whether the buffer should be initialized. If clear is true
, all bits in the buffer are to be set to 0 (zero); if clear is false
, the buffer will not be initialized.
This function is intended to have the semantics of malloc() and calloc(). However, unlike malloc() and calloc(), which allow for a "special" pointer to be returned instead of NULL, this function always returns NULL on failure or when size is set to 0 (zero).
herr_t H5atclose | ( | H5_atclose_func_t | func, |
void * | ctx | ||
) |
Registers a callback for the library to invoke when it's closing.
[in] | func | The function pointer to invoke |
[in] | ctx | Context to pass to func when invoked |
H5atclose() registers a callback that the HDF5 library will invoke when closing. The full capabilities of the HDF5 library are available to callbacks invoked through this mechanism, and library shutdown will only begin in earnest when all callbacks have been invoked and have returned.
Registered callbacks are invoked in LIFO order, similar to the Standard C 'atexit' routine. For example, if 'func1' is registered, then 'func2', when the library is closing 'func2', will be invoked first, then 'func1'.
The ctx
pointer will be passed to func
when it's invoked. NULL is allowed for ctx
.
If the HDF5 library is initialized and closed more than once, the func
callback must be registered within each open/close cycle.
herr_t H5check_version | ( | unsigned | majnum, |
unsigned | minnum, | ||
unsigned | relnum | ||
) |
Verifies that HDF5 library versions are consistent.
[in] | majnum | HDF5 library major version number |
[in] | minnum | HDF5 library minor version number |
[in] | relnum | HDF5 library release number |
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 example:
An official HDF5 release is labelled as follows: HDF5 Release <majnum>.<minnum>.<relnum>
For example, in HDF5 Release 1.8.5:
majnum
. minnum
. 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 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.
herr_t H5close | ( | void | ) |
Flushes all data to disk, closes all open objects, and releases memory.
H5close() flushes all data to disk, closes all open HDF5 objects, and cleans up all memory used by the HDF5 library. This function is generally called when the application calls exit(), but may be called earlier in the event of an emergency shutdown or out of a desire to free all resources used by the HDF5 library.
herr_t H5dont_atexit | ( | void | ) |
Instructs library not to install atexit() cleanup routine.
H5dont_atexit() indicates to the library that an atexit() cleanup routine should not be installed. The major purpose for using this function 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 that was no longer in memory, causing errors.
herr_t H5free_memory | ( | void * | mem | ) |
Frees memory allocated by the HDF5 library.
[in] | mem | Buffer to be freed. Can be NULL |
H5free_memory() frees the memory that has been allocated by the caller with H5allocate_memory() or by the HDF5 library on behalf of the caller.
H5Tget_member_name() provides an example of memory allocation on behalf of the caller: The function returns a buffer containing the name of a compound datatype member. It is the caller's responsibility to eventually free that buffer with H5free_memory().
herr_t H5garbage_collect | ( | void | ) |
Garbage collects on all free-lists of all types.
H5garbage_collect() walks through all 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 for 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.
herr_t H5get_free_list_sizes | ( | size_t * | reg_size, |
size_t * | arr_size, | ||
size_t * | blk_size, | ||
size_t * | fac_size | ||
) |
Gets the current size of the free lists used to manage memory.
[out] | reg_size | The current size of all "regular" free list memory used |
[out] | arr_size | The current size of all "array" free list memory used |
[out] | blk_size | The current size of all "block" free list memory used |
[out] | fac_size | The current size of all "factory" free list memory used |
H5get_free_list_sizes() obtains the current size of the different kinds of free lists that the library uses to manage memory. The free list sizes can be set with H5set_free_list_limits() and garbage collected with H5garbage_collect(). These lists are global for the entire library.
herr_t H5get_libversion | ( | unsigned * | majnum, |
unsigned * | minnum, | ||
unsigned * | relnum | ||
) |
Returns the HDF library release number.
[out] | majnum | The major version number of the library |
[out] | minnum | The minor version number of the library |
[out] | relnum | The release version number of the library |
H5get_libversion() retrieves the major, minor, and release numbers of the version of the HDF5 library which is linked to the application.
Checks whether the HDF5 library is closing.
[out] | is_terminating | Flag indicating whether library is shutting down |
H5is_library_terminating() queries whether the HDF5 library is in the process of shutting down. The is_terminating
flag will only be set to true after shutdown starts, it will be false before the library has been initialized, while the library is initialized, and after it has been closed. The value of is_terminating
is undefined if this routine fails.
Determines whether the HDF5 library was built with the thread-safety feature enabled.
[out] | is_ts | Boolean value indicating whether the library was built with thread-safety enabled |
The HDF5 library, although not internally multi-threaded, can be built with a thread-safety feature enabled that protects internal data structures with a mutex. In certain circumstances, it may be useful to determine, at run-time, whether the linked HDF5 library was built with the thread-safety feature enabled.
herr_t H5open | ( | void | ) |
Initializes the HDF5 library.
H5open() initializes the HDF5 library.
When the HDF5 library is used in a C application, the library is automatically initialized when the first HDf5 function call is issued. If one finds that an HDF5 library function is failing inexplicably, H5open() can be called first. It is safe to call H5open() before an application issues any other function calls to the HDF5 library, as there are no damaging side effects in calling it more than once.
void* H5resize_memory | ( | void * | mem, |
size_t | size | ||
) |
Resizes and, if required, re-allocates memory that will later be freed internally by the HDF5 library.
[in] | mem | Pointer to a buffer to be resized. May be NULL |
[in] | size | New size of the buffer, in bytes |
H5resize_memory() takes a pointer to an existing buffer and resizes the buffer to match the value in size
. If necessary, the buffer is reallocated. If size
is 0, the buffer is released.
The input buffer must either be NULL or have been allocated by H5allocate_memory() since the input buffer may be freed by the library.
For certain behaviors, the pointer mem
may be passed in as NULL.
This function is intended to have the semantics of realloc():
H5resize_memory(buffer, size) | Resizes buffer. Returns pointer to resized buffer. |
H5resize_memory(NULL, size) | Allocates memory using HDF5 Library allocator. Returns pointer to new buffer |
H5resize_memory(buffer, 0) | Frees memory using HDF5 Library allocator. Returns NULL. |
H5resize_memory(NULL, 0) | Returns NULL (undefined in C standard). |
Unlike realloc(), which allows for a "special pointer to be returned instead of NULL, this function always returns NULL on failure or when size is 0 (zero).
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 | ||
) |
Sets free-list size limits.
[in] | reg_global_lim | The cumulative limit, in bytes, on memory used for all regular free lists (Default: 1MB) |
[in] | reg_list_lim | The limit, in bytes, on memory used for each regular free list (Default: 64KB) |
[in] | arr_global_lim | The cumulative limit, in bytes, on memory used for all array free lists (Default: 4MB) |
[in] | arr_list_lim | The limit, in bytes, on memory used for each array free list (Default: 256KB) |
[in] | blk_global_lim | The cumulative limit, in bytes, on memory used for all block free lists and, separately, for all factory free lists (Default: 16MB) |
[in] | blk_list_lim | The limit, in bytes, on memory used for each block or factory free list (Default: 1MB) |
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 4Mb of total storage might be allocated, 1Mb for each of the regular, array, block, and factory type lists.
The settings specified for block free lists are duplicated for factory free lists. Therefore, increasing the global limit on block free lists by x bytes will increase the potential free list memory usage by 2x bytes.
Using a value of -1 for a limit means that no limit is set for the specified type of free list.