[ VIGRA Homepage | Function Index | Class Index | Namespaces | File List | Main Page ]

details HDF5HandleShared Class Reference VIGRA

Wrapper for shared hid_t objects. More...

#include <vigra/hdf5impex.hxx>

Public Member Functions

herr_t close ()
 Close the handle if this is the unique (i.e. last) owner. More...
 
hid_t get () const
 Get a temporary hid_t object for the contained handle. Do not call a close function on the return value - a crash will be likely otherwise.
 
 HDF5HandleShared ()
 Default constructor. Creates a NULL handle.
 
 HDF5HandleShared (hid_t h, Destructor destructor, const char *error_message)
 Create a shared wrapper for a plain hid_t object. More...
 
 HDF5HandleShared (HDF5HandleShared const &h)
 Copy constructor. Shares ownership with the RHS handle (analogous to std::shared_ptr).
 
 operator hid_t () const
 Convert to a plain hid_t object. More...
 
bool operator!= (HDF5HandleShared const &h) const
 Inequality comparison of the contained handle.
 
bool operator!= (hid_t h) const
 Inequality comparison of the contained handle.
 
HDF5HandleSharedoperator= (HDF5HandleShared const &h)
 Assignment. Call close() for the present LHS handle and share ownership with the RHS handle (analogous to std::shared_ptr).
 
bool operator== (HDF5HandleShared const &h) const
 Equality comparison of the contained handle.
 
bool operator== (hid_t h) const
 Equality comparison of the contained handle.
 
void reset (hid_t h, Destructor destructor, const char *error_message)
 Reset the handle to a new value. More...
 
void swap (HDF5HandleShared &h)
 Swap the contents of two handle wrappers. More...
 
bool unique () const
 Check if this is the unique owner of the conatined handle. More...
 
size_t use_count () const
 Get the number of owners of the contained handle.
 
 ~HDF5HandleShared ()
 Destructor (calls close())
 

Detailed Description

Wrapper for shared hid_t objects.

This class offers the functionality of std::shared_ptr for HDF5 handles (type hid_t). Unfortunately, std::shared_ptr cannot be used directly for this purpose because it only works with pointers, whereas hid_t is an integer type.

Newly created or opened HDF5 handles are stored as objects of type hid_t. When the handle is no longer needed, the appropriate close function must be called. However, if a function is aborted by an exception, this is difficult to ensure. Class HDF5HandleShared is a smart pointer that solves this problem by calling the close function in the destructor of the handle's last owner (This is analogous to how std::shared_ptr calls 'delete' on the contained pointer). A pointer to the close function must be passed to the constructor, along with an error message that is raised when creation/opening fails.

When a HDF5HandleShared is created or assigned from another one, ownership is shared between the two handles, and the value returned by use_count() increases by one.

Since HDF5HandleShared objects are convertible to hid_t, they can be used in the code in place of the latter.

Usage:

HDF5HandleShared file_id(H5Fopen(filename, H5F_ACC_RDWR, H5P_DEFAULT),
&H5Fclose,
"Error message when H5Fopen() fails.");
... // use file_id in the same way as a plain hid_t object
// share ownership between same_id and file_id
HDF5HandleShared same_id(file_id);
assert(same_id.use_count() == 2);
assert(same_id.get() == file_id.get());

#include <vigra/hdf5impex.hxx>
Namespace: vigra


The documentation for this class was generated from the following file:

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de)
Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany

html generated using doxygen and Python
vigra 1.10.0 (Thu Jan 8 2015)