Last modified: 16 September 2014
Name: H5Tregister
Signature:
  herr_t `H5Tregister`( H5T_pers_t `type`, const char * `name`, hid_t `src_id`, hid_t `dst_id`, H5T_conv_t `func` )

Purpose:
  Registers a conversion function.

Description:
  `H5Tregister` registers a hard or soft conversion function for a datatype conversion path.

  The parameter `type` indicates whether a conversion function is hard (`H5T_PERS_HARD`) or soft (`H5T_PERS_SOFT`). User-defined functions employing compiler casting are designated as hard; other user-defined conversion functions registered with the HDF5 Library (with `H5Tregister`) are designated as soft. The HDF5 Library also has its own hard and soft conversion functions.

  A conversion path can have only one hard function. When `type` is `H5T_PERS_HARD`, `func` replaces any previous hard function.

  When `type` is `H5T_PERS_SOFT`, `H5Tregister` adds the function to the end of the master soft list and replaces the soft function in all applicable existing conversion paths. Soft functions are used when determining which conversion function is appropriate for this path.

  The `name` is used only for debugging and should be a short identifier for the function.

  The path is specified by the source and destination datatypes `src_id` and `dst_id`. For soft conversion functions, only the class of these types is important.

  The type of the conversion function pointer is declared as:

      typedef herr_t (*H5T_conv_t) (hid_t src_id,
                                    hid_t dst_id,
                                    H5T_cdata_t *cdata,
                                    size_t nelmts,
                                    size_t buf_stride,
                                    size_t bkg_stride,
                                    void *buf,
                                    void *bkg,
                                    hid_t dset_xfer_plist)

  The `H5T_cdata_t` struct is declared as:

      typedef struct *H5T_cdata_t (H5T_cmd_t command,
                                   H5T_bkg_t need_bkg,
                                   hbool_t *recalc,
                                   void *priv)

Programming Note for C++ Developers Using C Functions:

  If a C routine that takes a function pointer as an argument is called from within C++ code, the C routine should be returned from normally.

  Examples of this kind of routine include callbacks such as `H5Pset_elink_cb` and `H5Pset_type_conv_cb` and functions such as `H5Tconvert` and `H5Ewalk2`.

  Exiting the routine in its normal fashion allows the HDF5 C Library to clean up its work properly. In other words, if the C++ application jumps out of the routine back to the C++ “catch” statement, the library is not given the opportunity to close any temporary data structures that were set up when the routine was called. The C++ application should save some state as the routine is started so that any problem that occurs might be diagnosed.

Parameters:

  H5T_pers_t `type` | IN: Conversion function type: `` `H5T_PERS_HARD` for hard conversion functions `` `H5T_PERS_SOFT` for soft conversion functions
  const char * `name` | IN: Name displayed in diagnostic output
  hid_t `src_id` | IN: Identifier of source datatype
  hid_t `dst_id` | IN: Identifier of destination datatype
  H5T_conv_t `func` | IN: Function to convert between source and destination datatypes

Returns:
  Returns a non-negative value if successful; otherwise returns a negative value.

Fortran90 Interface:
  None.

History:

  Release | C
  1.6.3 | The following change occurred in the `H5Tconv_t` function: `nelmts` parameter type changed to size_t.