+/* 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 (struct serial *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)
+{
+ struct serial *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. */
+
+static void
+push_event (void *context)
+{
+ struct serial *scb = context;
+ scb->async_state = NOTHING_SCHEDULED; /* Timers are one-off */
+ scb->async_handler (scb, scb->async_context);
+ /* re-schedule */
+ reschedule (scb);
+}
+
+/* Put the SERIAL device into/out-of ASYNC mode. */
+
+void
+ser_unix_async (struct serial *scb,
+ int async_p)
+{
+ if (async_p)
+ {
+ /* Force a re-schedule. */
+ scb->async_state = NOTHING_SCHEDULED;
+ if (serial_debug_p (scb))
+ fprintf_unfiltered (gdb_stdlog, "[fd%d->asynchronous]\n",
+ scb->fd);
+ reschedule (scb);
+ }
+ else
+ {
+ if (serial_debug_p (scb))
+ fprintf_unfiltered (gdb_stdlog, "[fd%d->synchronous]\n",
+ scb->fd);
+ /* De-schedule whatever tasks are currently scheduled. */
+ switch (scb->async_state)
+ {
+ case FD_SCHEDULED:
+ delete_file_handler (scb->fd);
+ break;
+ NOTHING_SCHEDULED:
+ break;
+ default: /* TIMER SCHEDULED */
+ delete_timer (scb->async_state);
+ break;
+ }
+ }
+}
+