fix nowait for polling + add nonblocking example

Signed-off-by: Mattias Andrée <maandree@operamail.com>

2 files changed, 44 insertions, 20 deletions

diff --git a/src/bus.c b/src/bus.c
index 72747ea..4b2d0f9 100644
--- a/src/bus.c
+++ b/src/bus.c
@@ -745,14 +745,25 @@ done:
  * misbehave, is `bus_poll` is written to expect
  * this function to have been called.
  * 
- * @param   bus  Bus information
- * @return       0 on success, -1 on error
+ * @param   bus    Bus information
+ * @param   flags  `IPC_NOWAIT` if the bus should fail and set `errno` to
+ *                 `EAGAIN` if there isn't already a message available on
+ *                 the bus when `bus_poll` is called
+ * @return         0 on success, -1 on error
  */
 int
-bus_poll_start(bus_t *bus)
+bus_poll_start(bus_t *bus, int flags)
 {
 	bus->first_poll = 1;
-	return release_semaphore(bus, S, SEM_UNDO);
+	bus->flags = flags;
+	t(release_semaphore(bus, S, SEM_UNDO));
+	if (flags & BUS_NOWAIT) {
+		t(release_semaphore(bus, Q, 0));
+	}
+	return 0;
+
+fail:
+	return -1;
 }
 
 
@@ -779,29 +790,35 @@ bus_poll_stop(const bus_t *bus)
  * started, the caller of this function should then
  * either call `bus_poll` again or `bus_poll_stop`.
  * 
- * @param   bus    Bus information
- * @param   flags  `IPC_NOWAIT` if the bus should fail and set `errno` to
- *                 `EAGAIN` if this isn't already a message available on the bus
- * @return         The received message, `NULL` on error
+ * @param   bus  Bus information
+ * @return       The received message, `NULL` on error
  */
 const char *
-bus_poll(bus_t *bus, int flags)
+bus_poll(bus_t *bus)
 {
 	int state = 0, saved_errno;
-	(void) flags;
 	if (!bus->first_poll) {
 		t(release_semaphore(bus, W, SEM_UNDO));  state++;
 		t(acquire_semaphore(bus, S, SEM_UNDO));  state++;
 		t(zero_semaphore(bus, S, 0));
+#ifndef BUS_SEMAPHORES_ARE_SYNCHRONOUS_ME_HARDER
 		t(zero_semaphore(bus, N, 0));
+#endif
 		t(release_semaphore(bus, S, SEM_UNDO));  state--;
 		t(acquire_semaphore(bus, W, SEM_UNDO));  state--;
+		if (bus->flags & BUS_NOWAIT) {
+			t(release_semaphore(bus, Q, 0));
+		}
 	} else {
 		bus->first_poll = 0;
 	}
 	state--;
-	t(release_semaphore(bus, Q, 0));
-	t(zero_semaphore(bus, Q, F(BUS_NOWAIT, IPC_NOWAIT)));
+	if (bus->flags & BUS_NOWAIT) {
+		t(zero_semaphore(bus, Q, IPC_NOWAIT));
+	} else {
+		t(release_semaphore(bus, Q, 0));
+		t(zero_semaphore(bus, Q, 0));
+	}
 	return bus->message;
 
 fail:
diff --git a/src/bus.h b/src/bus.h
index 4f38067..2cd534b 100644
--- a/src/bus.h
+++ b/src/bus.h
@@ -105,6 +105,12 @@ typedef struct bus
 	 * if `bus_poll` failed during reading
 	 */
 	int first_poll;
+
+	/**
+	 * Flags used for polling
+	 */
+	int flags;
+
 } bus_t;
 
 
@@ -199,10 +205,13 @@ int bus_read(const bus_t *bus, int (*callback)(const char *message, void *user_d
  * misbehave, is `bus_poll` is written to expect
  * this function to have been called.
  * 
- * @param   bus  Bus information
- * @return       0 on success, -1 on error
+ * @param   bus    Bus information
+ * @param   flags  `IPC_NOWAIT` if the bus should fail and set `errno` to
+ *                 `EAGAIN` if there isn't already a message available on
+ *                 the bus when `bus_poll` is called
+ * @return         0 on success, -1 on error
  */
-int bus_poll_start(bus_t *bus);
+int bus_poll_start(bus_t *bus, int flags);
 
 /**
  * Announce that the thread has stopped listening on the bus.
@@ -222,12 +231,10 @@ int bus_poll_stop(const bus_t *bus);
  * started, the caller of this function should then
  * either call `bus_poll` again or `bus_poll_stop`.
  * 
- * @param   bus    Bus information
- * @param   flags  `IPC_NOWAIT` if the bus should fail and set `errno` to
- *                 `EAGAIN` if this isn't already a message available on the bus
- * @return         The received message, `NULL` on error
+ * @param   bus  Bus information
+ * @return       The received message, `NULL` on error
  */
-const char *bus_poll(bus_t *bus, int flags);
+const char *bus_poll(bus_t *bus);
 /* TODO bus_poll_timed */