Signature:

  SUBROUTINE h5ovisit_f(object_id, index_type, order, op, op_data, &
            return_value, hdferr)
    INTEGER(HID_T), INTENT(IN) :: object_id
    INTEGER, INTENT(IN) :: index_type 
    INTEGER, INTENT(IN) :: order

    TYPE(C_FUNPTR):: op
    TYPE(C_PTR)   :: op_data
    INTEGER, INTENT(OUT) :: return_value
    INTEGER, INTENT(OUT) :: hdferr

Inputs:

  object_id  - Identifier of the object at which the recursive iteration 
                begins.
  index_type - Type of index; valid values include:
                H5_INDEX_NAME_F
                H5_INDEX_CRT_ORDER_F
  order      - Order in which index is traversed; valid values include:
                H5_ITER_DEC_F
                H5_ITER_INC_F
                H5_ITER_NATIVE_F
  op         - Callback function passing data regarding the group to the 
               calling application
  op_data    - User-defined pointer to data required by the application 
               for its processing of the group

Outputs:

  return_value - Returns the return value of the first operator that 
                 returns a positive value, or zero if all members were 
                 processed with no operator returning non-zero.
  hdferr       - Returns 0 if successful and -1 if fails.