queue: added queue_shuffle_order_last()

src/playlist.c

@@ -442,12 +442,9 @@ addSongToPlaylist(struct song *song, unsigned *added_id)
 			start = playlist.queued + 1;
 		else
 			start = playlist.current + 1;
-		if (start < queue_length(&playlist.queue)) {
-			unsigned swap = g_rand_int_range(g_rand, start,
+		if (start < queue_length(&playlist.queue))
+			queue_shuffle_order_last(&playlist.queue, start,
 						 queue_length(&playlist.queue));
-			queue_swap_order(&playlist.queue,
-					 queue_length(&playlist.queue) - 1, swap);
-		}
 	}
 
 	incrPlaylistVersion();

src/queue.c

@@ -255,6 +255,13 @@ queue_shuffle_order(struct queue *queue)
 }
 
 void
+queue_shuffle_order_last(struct queue *queue, unsigned start, unsigned end)
+{
+	queue_swap_order(queue, end - 1,
+			 g_rand_int_range(queue->rand, start, end));
+}
+
+void
 queue_shuffle_range(struct queue *queue, unsigned start, unsigned end)
 {
 	assert(start <= end);

src/queue.h

@@ -320,6 +320,14 @@ void
 queue_shuffle_order(struct queue *queue);
 
 /**
+ * Shuffles the virtual order of the last song in the specified
+ * (order) range.  This is used in random mode after a song has been
+ * appended by queue_append().
+ */
+void
+queue_shuffle_order_last(struct queue *queue, unsigned start, unsigned end);
+
+/**
  * Shuffles a (position) range in the queue.  The songs are physically
  * shuffled, not by using the "order" mapping.
  */