output: use GTimer instead of time_t for reopen after failure

time() is not a monotonic timer, and MPD might get confused by clock
skews.  clock_gettime() provides a monotonic clock, but is not
portable to non-POSIX systems (i.e. Windows).  This patch uses GLib's
GTimer API, which aims to be portable.

src/output_all.c

@@ -162,8 +162,14 @@ static void audio_output_wait_all(void)
 static void
 audio_output_all_reset_reopen(void)
 {
-	for (unsigned i = 0; i < num_audio_outputs; ++i)
-		audio_outputs[i].reopen_after = 0;
+	for (unsigned i = 0; i < num_audio_outputs; ++i) {
+		struct audio_output *ao = &audio_outputs[i];
+
+		if (!ao->open && ao->fail_timer != NULL) {
+			g_timer_destroy(ao->fail_timer);
+			ao->fail_timer = NULL;
+		}
+	}
 }
 
 static void

src/output_command.c

@@ -38,7 +38,6 @@ audio_output_enable_index(unsigned idx)
 
 	ao = audio_output_get(idx);
 
-	ao->reopen_after = 0;
 	ao->enabled = true;
 	idle_add(IDLE_OUTPUT);
 

src/output_control.c

@@ -24,6 +24,12 @@
 #include <assert.h>
 #include <stdlib.h>
 
+enum {
+	/** after a failure, wait this number of seconds before
+	    automatically reopening the device */
+	REOPEN_AFTER = 10,
+};
+
 struct notify audio_output_client_notify;
 
 static void ao_command_wait(struct audio_output *ao)
@@ -53,7 +59,10 @@ bool
 audio_output_open(struct audio_output *ao,
 		  const struct audio_format *audio_format)
 {
-	ao->reopen_after = 0;
+	if (ao->fail_timer != NULL) {
+		g_timer_destroy(ao->fail_timer);
+		ao->fail_timer = NULL;
+	}
 
 	if (ao->open &&
 	    audio_format_equals(audio_format, &ao->in_audio_format)) {
@@ -90,7 +99,8 @@ audio_output_update(struct audio_output *ao,
 		    const struct audio_format *audio_format)
 {
 	if (ao->enabled) {
-		if (ao->reopen_after == 0 || time(NULL) > ao->reopen_after)
+		if (ao->fail_timer == NULL ||
+		    g_timer_elapsed(ao->fail_timer, NULL) > REOPEN_AFTER)
 			audio_output_open(ao, audio_format);
 	} else if (audio_output_is_open(ao))
 		audio_output_close(ao);
@@ -127,14 +137,22 @@ void audio_output_cancel(struct audio_output *ao)
 
 void audio_output_close(struct audio_output *ao)
 {
+	assert(!ao->open || ao->fail_timer == NULL);
+
 	if (ao->open)
 		ao_command(ao, AO_COMMAND_CLOSE);
+	else if (ao->fail_timer != NULL) {
+		g_timer_destroy(ao->fail_timer);
+		ao->fail_timer = NULL;
+	}
 }
 
 void audio_output_finish(struct audio_output *ao)
 {
 	audio_output_close(ao);
 
+	assert(ao->fail_timer == NULL);
+
 	if (ao->thread != NULL) {
 		ao_command(ao, AO_COMMAND_KILL);
 		g_thread_join(ao->thread);

src/output_init.c

@@ -93,7 +93,7 @@ audio_output_init(struct audio_output *ao, const struct config_param *param)
 	ao->plugin = plugin;
 	ao->enabled = config_get_block_bool(param, "enabled", true);
 	ao->open = false;
-	ao->reopen_after = 0;
+	ao->fail_timer = NULL;
 
 	pcm_convert_init(&ao->convert_state);
 

src/output_internal.h

@@ -65,10 +65,11 @@ struct audio_output {
 	bool open;
 
 	/**
-	 * If not zero, the device has failed, and should not be
-	 * reopened automatically before this time stamp.
+	 * If not NULL, the device has failed, and this timer is used
+	 * to estimate how long it should stay disabled (unless
+	 * explicitly reopened with "play").
 	 */
-	time_t reopen_after;
+	GTimer *fail_timer;
 
 	/**
 	 * The audio_format in which audio data is received from the

src/output_thread.c

@@ -29,12 +29,6 @@
 #undef G_LOG_DOMAIN
 #define G_LOG_DOMAIN "output"
 
-enum {
-	/** after a failure, wait this number of seconds before
-	    automatically reopening the device */
-	REOPEN_AFTER = 10,
-};
-
 static void ao_command_finished(struct audio_output *ao)
 {
 	assert(ao->command != AO_COMMAND_NONE);
@@ -129,6 +123,7 @@ static gpointer audio_output_task(gpointer arg)
 
 		case AO_COMMAND_OPEN:
 			assert(!ao->open);
+			assert(ao->fail_timer == NULL);
 
 			error = NULL;
 			ret = ao_plugin_open(ao->plugin, ao->data,
@@ -145,7 +140,7 @@ static gpointer audio_output_task(gpointer arg)
 					  error->message);
 				g_error_free(error);
 
-				ao->reopen_after = time(NULL) + REOPEN_AFTER;
+				ao->fail_timer = g_timer_new();
 			}
 
 			ao_command_finished(ao);