+
+\f
+/* Event handling for ASYNC serial code.
+
+ At any time the SERIAL device either: has an empty FIFO and is
+ waiting on a FD event; or has a non-empty FIFO/error condition and
+ is constantly scheduling timer events.
+
+ ASYNC only stops pestering its client when it is de-async'ed or it
+ is told to go away. */
+
+/* Value of scb->async_state: */
+enum {
+ /* >= 0 (TIMER_SCHEDULED) */
+ /* The ID of the currently scheduled timer event. This state is
+ rarely encountered. Timer events are one-off so as soon as the
+ event is delivered the state is shanged to NOTHING_SCHEDULED. */
+ FD_SCHEDULED = -1,
+ /* The fd_event() handler is scheduled. It is called when ever the
+ file descriptor becomes ready. */
+ NOTHING_SCHEDULED = -2
+ /* Either no task is scheduled (just going into ASYNC mode) or a
+ timer event has just gone off and the current state has been
+ forced into nothing scheduled. */
+};
+
+/* Identify and schedule the next ASYNC task based on scb->async_state
+ and scb->buf* (the input FIFO). A state machine is used to avoid
+ the need to make redundant calls into the event-loop - the next
+ scheduled task is only changed when needed. */
+
+static void
+reschedule (serial_t scb)
+{
+ if (SERIAL_IS_ASYNC_P (scb))
+ {
+ int next_state;
+ switch (scb->async_state)
+ {
+ case FD_SCHEDULED:
+ if (scb->bufcnt == 0)
+ next_state = FD_SCHEDULED;
+ else
+ {
+ delete_file_handler (scb->fd);
+ next_state = create_timer (0, push_event, scb);
+ }
+ break;
+ case NOTHING_SCHEDULED:
+ if (scb->bufcnt == 0)
+ {
+ add_file_handler (scb->fd, fd_event, scb);
+ next_state = FD_SCHEDULED;
+ }
+ else
+ {
+ next_state = create_timer (0, push_event, scb);
+ }
+ break;
+ default: /* TIMER SCHEDULED */
+ if (scb->bufcnt == 0)
+ {
+ delete_timer (scb->async_state);
+ add_file_handler (scb->fd, fd_event, scb);
+ next_state = FD_SCHEDULED;
+ }
+ else
+ next_state = scb->async_state;
+ break;
+ }
+ if (SERIAL_DEBUG_P (scb))
+ {
+ switch (next_state)
+ {
+ case FD_SCHEDULED:
+ if (scb->async_state != FD_SCHEDULED)
+ fprintf_unfiltered (gdb_stdlog, "[fd%d->fd-scheduled]\n",
+ scb->fd);
+ break;
+ default: /* TIMER SCHEDULED */
+ if (scb->async_state == FD_SCHEDULED)
+ fprintf_unfiltered (gdb_stdlog, "[fd%d->timer-scheduled]\n",
+ scb->fd);
+ break;
+ }
+ }
+ scb->async_state = next_state;
+ }
+}
+
+/* FD_EVENT: This is scheduled when the input FIFO is empty (and there
+ is no pending error). As soon as data arrives, it is read into the
+ input FIFO and the client notified. The client should then drain
+ the FIFO using readchar(). If the FIFO isn't immediatly emptied,
+ push_event() is used to nag the client until it is. */
+
+static void
+fd_event (int error, void *context)
+{
+ serial_t scb = context;
+ if (error != 0)
+ {
+ scb->bufcnt = SERIAL_ERROR;
+ }
+ else if (scb->bufcnt == 0)
+ {
+ /* Prime the input FIFO. The readchar() function is used to
+ pull characters out of the buffer. See also
+ generic_readchar(). */
+ int nr;
+ do
+ {
+ nr = read (scb->fd, scb->buf, BUFSIZ);
+ }
+ while (nr == -1 && errno == EINTR);
+ if (nr == 0)
+ {
+ scb->bufcnt = SERIAL_EOF;
+ }
+ else if (nr > 0)
+ {
+ scb->bufcnt = nr;
+ scb->bufp = scb->buf;
+ }
+ else
+ {
+ scb->bufcnt = SERIAL_ERROR;
+ }
+ }
+ scb->async_handler (scb, scb->async_context);
+ reschedule (scb);
+}
+
+/* PUSH_EVENT: The input FIFO is non-empty (or there is a pending
+ error). Nag the client until all the data has been read. In the
+ case of errors, the client will need to close or de-async the
+ device before naging stops. */
+