HDF5 1.14.5
API Reference
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The Identifiers (H5I) module contains functions to define new identifier types. For convenience, handles of type hid_t can then be associated with the new identifier types and user objects.
New identifier types can be created by registering a new identifier type with the HDF5 library. Once a new identifier type has bee registered, it can be used to generate identifiers for user objects.
User-defined identifier types can be searched and iterated.
Like library-defined identifiers, user-defined identifiers and identifier types are reference counted, and the reference counts can be manipulated accordingly.
User-defined identifiers no longer in use should be deleted or reclaimed, and identifier types should be destroyed if they are no longer required.
Create | Read |
---|---|
void * H5allocate_memory(size_t size, hbool_t clear) Allocates memory that will be freed later internally. herr_t H5Iclear_type(H5I_type_t type, hbool_t force) Deletes all identifiers of the given type. herr_t H5Idestroy_type(H5I_type_t type) Removes an identifier type and all identifiers within that type. hid_t H5Iregister(H5I_type_t type, const void *object) Registers an object under a type and returns an ID for it. H5I_type_t H5Iregister_type(size_t hash_size, unsigned reserved, H5I_free_t free_func) Creates and returns a new ID type. | herr_t H5Inmembers(H5I_type_t type, hsize_t *num_members) Returns the number of identifiers in a given identifier type. |
Update | Delete |
int H5Idec_type_ref(H5I_type_t type) Decrements the reference count on an identifier type. |
Functions | |
hid_t | H5Iregister (H5I_type_t type, const void *object) |
Registers an object under a type and returns an ID for it. | |
void * | H5Iobject_verify (hid_t id, H5I_type_t type) |
Returns the object referenced by an ID. | |
void * | H5Iremove_verify (hid_t id, H5I_type_t type) |
Removes an ID from its type. | |
H5I_type_t | H5Iregister_type (size_t hash_size, unsigned reserved, H5I_free_t free_func) |
Creates and returns a new ID type. | |
herr_t | H5Iclear_type (H5I_type_t type, hbool_t force) |
Deletes all identifiers of the given type. | |
herr_t | H5Idestroy_type (H5I_type_t type) |
Removes an identifier type and all identifiers within that type. | |
int | H5Iinc_type_ref (H5I_type_t type) |
Increments the reference count on an ID type. | |
int | H5Idec_type_ref (H5I_type_t type) |
Decrements the reference count on an identifier type. | |
int | H5Iget_type_ref (H5I_type_t type) |
Retrieves the reference count on an ID type. | |
void * | H5Isearch (H5I_type_t type, H5I_search_func_t func, void *key) |
Finds the memory referred to by an ID within the given ID type such that some criterion is satisfied. | |
herr_t | H5Iiterate (H5I_type_t type, H5I_iterate_func_t op, void *op_data) |
Calls a callback for each member of the identifier type specified. | |
herr_t | H5Inmembers (H5I_type_t type, hsize_t *num_members) |
Returns the number of identifiers in a given identifier type. | |
htri_t | H5Itype_exists (H5I_type_t type) |
Determines whether an identifier type is registered. | |
herr_t H5Iclear_type | ( | H5I_type_t | type, |
hbool_t | force | ||
) |
Deletes all identifiers of the given type.
[in] | type | Identifier of identifier type which is to be cleared of identifiers |
[in] | force | Whether or not to force deletion of all identifiers |
H5Iclear_type() deletes all identifiers of the type identified by the argument type
.
The identifier type's free function is first called on all of these identifiers to free their memory, then they are removed from the type.
If the force
flag is set to false, only those identifiers whose reference counts are equal to 1 will be deleted, and all other identifiers will be entirely unchanged. If the force flag is true, all identifiers of this type will be deleted.
int H5Idec_type_ref | ( | H5I_type_t | type | ) |
Decrements the reference count on an identifier type.
[in] | type | The identifier of the type whose reference count is to be decremented |
H5Idec_type_ref() decrements the reference count on an identifier type. The reference count is used by the library to indicate when an identifier type can be destroyed. If the reference count reaches zero, this function will destroy it.
The type parameter is the identifier for the identifier type whose reference count is to be decremented. This identifier must have been created by a call to H5Iregister_type().
herr_t H5Idestroy_type | ( | H5I_type_t | type | ) |
Removes an identifier type and all identifiers within that type.
[in] | type | Identifier of identifier type which is to be destroyed |
H5Idestroy_type deletes an entire identifier type type
. All identifiers of this type are destroyed and no new identifiers of this type can be registered.
The type's free function is called on all of the identifiers which are deleted by this function, freeing their memory. In addition, all memory used by this type's hash table is freed.
Since the H5I_type_t values of destroyed identifier types are reused when new types are registered, it is a good idea to set the variable holding the value of the destroyed type to H5I_UNINIT.
int H5Iget_type_ref | ( | H5I_type_t | type | ) |
Retrieves the reference count on an ID type.
[in] | type | The identifier of the type whose reference count is to be retrieved |
H5Iget_type_ref() retrieves the reference count on an ID type. The reference count is used by the library to indicate when an ID type can be destroyed.
The type parameter is the identifier for the ID type whose reference count is to be retrieved. This identifier must have been created by a call to H5Iregister_type().
int H5Iinc_type_ref | ( | H5I_type_t | type | ) |
Increments the reference count on an ID type.
[in] | type | The identifier of the type whose reference count is to be incremented |
H5Iinc_type_ref() increments the reference count on an ID type. The reference count is used by the library to indicate when an ID type can be destroyed.
The type parameter is the identifier for the ID type whose reference count is to be incremented. This identifier must have been created by a call to H5Iregister_type().
herr_t H5Iiterate | ( | H5I_type_t | type, |
H5I_iterate_func_t | op, | ||
void * | op_data | ||
) |
Calls a callback for each member of the identifier type specified.
[in] | type | The identifier type |
[in] | op | The callback function |
[in,out] | op_data | The data for the callback function |
op
H5Iiterate() calls the callback function op
for each member of the identifier type type
. The callback function type for op
, H5I_iterate_func_t, is defined in H5Ipublic.h as:
op
takes as parameters the identifier and a pass through of op_data
, and returns an herr_t.
A positive return from op will cause the iteration to stop and H5Iiterate() will return the value returned by op
. A negative return from op
will cause the iteration to stop and H5Iiterate() will return failure. A zero return from op
will allow iteration to continue, as long as there are other identifiers remaining in type.
herr_t H5Inmembers | ( | H5I_type_t | type, |
hsize_t * | num_members | ||
) |
Returns the number of identifiers in a given identifier type.
[in] | type | The identifier type |
[out] | num_members | Number of identifiers of the specified identifier type |
H5Inmembers() returns the number of identifiers of the identifier type specified in type
.
The number of identifiers is returned in num_members
. If no identifiers of this type have been registered, the type does not exist, or it has been destroyed, num_members
is returned with the value 0.
void * H5Iobject_verify | ( | hid_t | id, |
H5I_type_t | type | ||
) |
Returns the object referenced by an ID.
[in] | id | ID to be dereferenced |
[in] | type | The identifier type |
id
on success, NULL on failure.H5Iobject_verify() returns a pointer to the memory referenced by id after verifying that id
is of type type
. This function is analogous to dereferencing a pointer in C with type checking.
hid_t H5Iregister | ( | H5I_type_t | type, |
const void * | object | ||
) |
Registers an object under a type and returns an ID for it.
[in] | type | The identifier of the type of the new ID |
[in] | object | Pointer to object for which a new ID is created |
H5Iregister() creates and returns a new ID for an object.
The type
parameter is the identifier for the ID type to which this new ID will belong. This identifier must have been created by a call to H5Iregister_type().
The object
parameter is a pointer to the memory which the new ID will be a reference to. This pointer will be stored by the library and returned via a call to H5Iobject_verify().
H5I_type_t H5Iregister_type | ( | size_t | hash_size, |
unsigned | reserved, | ||
H5I_free_t | free_func | ||
) |
Creates and returns a new ID type.
[in] | hash_size | Minimum hash table size (in entries) used to store IDs for the new type (unused in 1.8.13 and later) |
[in] | reserved | Number of reserved IDs for the new type |
[in] | free_func | Function used to deallocate space for a single ID |
H5Iregister_type() allocates space for a new ID type and returns an identifier for it.
The hash_size
parameter indicates the minimum size of the hash table used to store IDs in the new type. This parameter is unused in 1.8.13 and later, when the implementation of ID storage changed.
The reserved
parameter indicates the number of IDs in this new type to be reserved. Reserved IDs are valid IDs which are not associated with any storage within the library.
The free_func
parameter is a function pointer to a function which returns an herr_t and accepts a void*
. The purpose of this function is to deallocate memory for a single ID. It will be called by H5Iclear_type() and H5Idestroy_type() on each ID. This function is NOT called by H5Iremove_verify(). The void*
will be the same pointer which was passed in to the H5Iregister() function. The free_func
function should return 0 on success and -1 on failure.
void * H5Iremove_verify | ( | hid_t | id, |
H5I_type_t | type | ||
) |
Removes an ID from its type.
[in] | id | The ID to be removed from its type |
[in] | type | The identifier type |
id
on success, NULL on failure.H5Iremove_verify() first ensures that id
belongs to type
. If so, it removes id
from its type and returns the pointer to the memory it referred to. This pointer is the same pointer that was placed in storage by H5Iregister(). If id does not belong to type
, then NULL is returned.
The id
parameter is the ID which is to be removed from its type.
The type
parameter is the identifier for the ID type which id
is supposed to belong to. This identifier must have been created by a call to H5Iregister_type().
id
refers to. The pointer returned by H5Iregister() must be deallocated by the user to avoid memory leaks.void * H5Isearch | ( | H5I_type_t | type, |
H5I_search_func_t | func, | ||
void * | key | ||
) |
Finds the memory referred to by an ID within the given ID type such that some criterion is satisfied.
[in] | type | The identifier of the type to be searched |
[in] | func | The function defining the search criteria |
[in] | key | A key for the search function |
H5Isearch() searches through a given ID type to find an object that satisfies the criteria defined by func
. If such an object is found, the pointer to the memory containing this object is returned. Otherwise, NULL is returned. To do this, func
is called on every member of type type
. The first member to satisfy func
is returned.
The type
parameter is the identifier for the ID type which is to be searched. This identifier must have been created by a call to H5Iregister_type().
The parameter func
is a function pointer to a function which takes three parameters. The first parameter is a void*
and will be a pointer to the object to be tested. This is the same object that was placed in storage using H5Iregister(). The second parameter is a hid_t and is the ID of the object to be tested. The last parameter is a void*
. This is the key
parameter and can be used however the user finds helpful, or it can be ignored if it is not needed. func
returns 0 if the object it is testing does not pass its criteria. A non-zero value should be returned if the object does pass its criteria. H5I_search_func_t is defined in H5Ipublic.h and is shown below.
The key
parameter will be passed to the search function as a parameter. It can be used to further define the search at run-time.
htri_t H5Itype_exists | ( | H5I_type_t | type | ) |
Determines whether an identifier type is registered.
[in] | type | Identifier type |
H5Itype_exists() determines whether the given identifier type, type
, is registered with the library.