queue: added queue_shuffle_order()

The function shuffles the virtual order of songs, but does not move
them physically.  This is used in random mode.

The new function replaces playlist.c's randomizeOrder() function,
which was aware of playlist.current and playlist.queued.  The latter
is always -1 anyway, and the former as preserved by the caller, by
converting playlist.current to a position, and then back to an order
number.

src/playlist.c

@@ -79,7 +79,6 @@ static int playlist_noGoToNext;
 bool playlist_saveAbsolutePaths = DEFAULT_PLAYLIST_SAVE_ABSOLUTE_PATHS;
 
 static void playPlaylistOrderNumber(int orderNum);
-static void randomizeOrder(int start, int end);
 
 static void incrPlaylistVersion(void)
 {
@@ -412,11 +411,20 @@ playlist_queue_song_order(unsigned order)
 
 static void queueNextSongInPlaylist(void)
 {
+	assert(playlist.queued < 0);
+
 	if (playlist.current + 1 < (int)queue_length(&playlist.queue)) {
 		playlist_queue_song_order(playlist.current + 1);
 	} else if (!queue_is_empty(&playlist.queue) && playlist.queue.repeat) {
-		if (queue_length(&playlist.queue) > 1 && playlist.queue.random)
-			randomizeOrder(0, queue_length(&playlist.queue) - 1);
+		if (playlist.queue.random) {
+			unsigned current_position =
+				queue_order_to_position(&playlist.queue,
+							playlist.current);
+			queue_shuffle_order(&playlist.queue);
+			playlist.current =
+				queue_position_to_order(&playlist.queue,
+							current_position);
+		}
 
 		playlist_queue_song_order(0);
 	}
@@ -650,8 +658,16 @@ void stopPlaylist(void)
 	playlist.queued = -1;
 	playlist_state = PLAYLIST_STATE_STOP;
 	playlist_noGoToNext = 0;
-	if (playlist.queue.random)
-		randomizeOrder(0, queue_length(&playlist.queue) - 1);
+
+	if (playlist.queue.random) {
+		unsigned current_position =
+			queue_order_to_position(&playlist.queue,
+						playlist.current);
+		queue_shuffle_order(&playlist.queue);
+		playlist.current =
+			queue_position_to_order(&playlist.queue,
+						current_position);
+	}
 }
 
 static void playPlaylistOrderNumber(int orderNum)
@@ -696,7 +712,7 @@ enum playlist_result playPlaylist(int song, int stopOnError)
 
 	if (playlist.queue.random) {
 		if (song == -1 && playlist_state == PLAYLIST_STATE_PLAY) {
-			randomizeOrder(0, queue_length(&playlist.queue) - 1);
+			queue_shuffle_order(&playlist.queue);
 		} else {
 			if (song >= 0)
 				i = queue_position_to_order(&playlist.queue, song);
@@ -787,7 +803,7 @@ void nextSongInPlaylist(void)
 	if (next_order == 0) {
 		assert(playlist.queue.repeat);
 
-		randomizeOrder(0, queue_length(&playlist.queue) - 1);
+		queue_shuffle_order(&playlist.queue);
 	}
 
 	playPlaylistOrderNumber(next_order);
@@ -928,27 +944,6 @@ static void orderPlaylist(void)
 	queue_restore_order(&playlist.queue);
 }
 
-static void randomizeOrder(int start, int end)
-{
-	int i;
-	int ri;
-
-	g_debug("playlist: randomize from %i to %i\n", start, end);
-
-	if (playlist_state == PLAYLIST_STATE_PLAY &&
-	    playlist.queued >= start && playlist.queued <= end)
-		clearPlayerQueue();
-
-	for (i = start; i <= end; i++) {
-		ri = g_rand_int_range(g_rand, i, end + 1);
-		if (ri == playlist.current)
-			playlist.current = i;
-		else if (i == playlist.current)
-			playlist.current = ri;
-		queue_swap_order(&playlist.queue, i, ri);
-	}
-}
-
 void setPlaylistRandomStatus(bool status)
 {
 	if (status == playlist.queue.random)
@@ -960,13 +955,18 @@ void setPlaylistRandomStatus(bool status)
 	playlist.queue.random = status;
 
 	if (playlist.queue.random) {
-		/*if(playlist_state==PLAYLIST_STATE_PLAY) {
-		  randomizeOrder(playlist.current+1,
-		  playlist.length-1);
-		  }
-		  else */ randomizeOrder(0, queue_length(&playlist.queue) - 1);
-		if (playlist.current >= 0) {
-			queue_swap_order(&playlist.queue, playlist.current, 0);
+		int current_position = playlist.current >= 0
+			? (int)queue_order_to_position(&playlist.queue,
+						       playlist.current)
+			: -1;
+
+		queue_shuffle_order(&playlist.queue);
+
+		if (current_position >= 0) {
+			unsigned current_order =
+				queue_position_to_order(&playlist.queue,
+							current_position);
+			queue_swap_order(&playlist.queue, 0, current_order);
 			playlist.current = 0;
 		}
 	} else

src/queue.c

@@ -242,6 +242,17 @@ queue_finish(struct queue *queue)
 	g_rand_free(queue->rand);
 }
 
+void
+queue_shuffle_order(struct queue *queue)
+{
+	assert(queue->random);
+
+	for (unsigned i = 0; i < queue->length; i++)
+		queue_swap_order(queue, i,
+				 g_rand_int_range(queue->rand, i,
+						  queue->length));
+}
+
 void
 queue_shuffle_range(struct queue *queue, unsigned start, unsigned end)
 {

src/queue.h

@@ -312,6 +312,13 @@ queue_restore_order(struct queue *queue)
 		queue->order[i] = i;
 }
 
+/**
+ * Shuffles the virtual order of songs, but does not move them
+ * physically.  This is used in random mode.
+ */
+void
+queue_shuffle_order(struct queue *queue);
+
 /**
  * Shuffles a (position) range in the queue.  The songs are physically
  * shuffled, not by using the "order" mapping.