vcan_msg_status
===============

Here is the definition::

  typedef enum
    { VCAN_OK=0,
      VCAN_ACCESS_ERR  =  1,/* access error, see errorcode ! */
      VCAN_TM_OUT      =  2,/* timeout occured */
      VCAN_LOST        =  4,/* some data was lost */
      VCAN_OLD         =  8,/* the data was already read (no new data
                               present) */
      VCAN_INCONSISTENT= 16,/* indicates that (due to overload or a missing
                               object-owner) there may be inconsistent data) */
      VCAN_TX_ERR      = 32,/* transmission error, the transmission was 
                               cancelled due to an error, this concerns 
                               writing and remote-transfers (see also 
                               errorcode) */
      VCAN_Q_OVERFLOW  = 64,/* queue overflow, (vcan_queue_read), the object
                               data is valid but there was an internal
                               queue overflow*/
      VCAN_Q_IGNORE    =128,/* the result of the function vcan_queue_readnow
                               has to be ignored, actually there was no CAN 
                               event although the user process received a 
                               signal. */
      VCAN_WAIT        =256 /* vcan_writetimed: user has still to wait before 
                               data can be sent */
    } vcan_msg_status;

This is the status that is returned when an action is performed on a
message. Only the ``vcan_message`` - structure has a field of this type.
The status-flags can be combined, since they are powers of 2.  Testing for a
single status-flag is done as follows::

  /* be 'status' a variable with several status-flags */
  /* test for 'VCAN_LOST' : */
  if (status & VCAN_LOST)
    printf("data was lost!!!\n");
  /* test for 'VCAN_OLD': */
  if (status & VCAN_OLD)
    printf("only old data was read!\n");

Explanation of the status-flags:

VCAN_OK
  There was no error.

VCAN_ACCESS_ERR
  There was an error, the error-code can be found in the message's
  error-variable.

VCAN_TM_OUT
  A timeout occured. Note that for ordinary reads (not remote-reads) a
  timeout is not viewed as an error and there is no additional error-flag
  set or error-code returned.  functions 

VCAN_LOST
  A message (data from the CAN bus) was lost.

VCAN_OLD
  The data has already been read before, so OLD data was returned.

VCAN_INCONSISTENT
  Inconsistent data was returned. The data consists of old and new data from
  the CAN bus that are mixed up.

VCAN_TX_ERR
  A transmission error was recognized. The transmission was not performed
  correctly. This error can also be signalled on remote-transfers when
  remote-read is used (since there is a *sending* of a remote frame
  involved).

VCAN_Q_OVERFLOW
  There was an overflow in the internal event-queue.  Events on some
  event-objects were lost.

VCAN_Q_IGNORE
  The result of the function ``vcan_queue_readnow`` has to be ignored. The
  user-process received a signal although there was no CAN event. This can
  sometimes happen in conjunction with signal-event objects.

VCAN_WAIT
  This status can only be returned when VCAN_WRITETIMED is used. In this
  case the specified inhibit-time has not yet been passed, the user program
  has to wait.