core/queue: Implement a new queue_iter

I plan to remove the containers/queue implementation, so we need a new
iterator for queue access.

Signed-off-by: Anna Schumaker <Anna@OcarinaProject.net>

include/core/queue.h

@@ -53,6 +53,12 @@ struct queue_ops {
 };
 
 
+struct queue_iter {
+	GList *it_iter; /* The current link in the GQueue.   */
+	guint  it_pos;  /* The current index into the queue. */
+};
+
+
 struct queue {
 	unsigned int   q_flags;   /* The queue's set of flags.               */
 	unsigned int   q_length;  /* The queue's total runtime (in seconds). */
@@ -65,6 +71,47 @@ struct queue {
 };
 
 
+
+/* Called to initialize a queue iterator. */
+static inline void queue_iter_init(struct queue *queue, struct queue_iter *it)
+{
+	it->it_iter = g_queue_peek_head_link(&queue->q_tracks._queue);
+	it->it_pos  = g_queue_link_index(&queue->q_tracks._queue, it->it_iter);
+}
+
+/* Called to advance a queue iterator by one step. */
+static inline void queue_iter_next(struct queue_iter *it)
+{
+	it->it_iter = g_list_next(it->it_iter);
+	it->it_pos++;
+}
+
+/* Called to rewind a queue iterator by one step. */
+static inline void queue_iter_prev(struct queue_iter *it)
+{
+	it->it_iter = g_list_previous(it->it_iter);
+	it->it_pos--;
+}
+
+/* Called to set a queue iterator to a specific position. */
+static inline void queue_iter_set(struct queue *queue, struct queue_iter *it,
+				  unsigned int pos)
+{
+	it->it_iter = g_queue_peek_nth_link(&queue->q_tracks._queue, pos);
+	it->it_pos  = pos;
+}
+
+/* Called to access the value of a queue iterator. */
+static inline struct track *queue_iter_val(struct queue_iter *it)
+{
+	return (it->it_iter) ? it->it_iter->data : NULL;
+}
+
+#define queue_for_each(queue, it) \
+	for (queue_iter_init(queue, it); (it)->it_iter; queue_iter_next(it))
+
+
+
 /* Called to initialize a queue. */
 void queue_init(struct queue *, unsigned int, const struct queue_ops *);
 

tests/core/queue.c

@@ -111,6 +111,7 @@ static void __test_deinit_core()
 static void test_init()
 {
 	struct queue q;
+	struct queue_iter it;
 
 	__test_init_core();
 
@@ -125,6 +126,11 @@ static void test_init()
 	test_equal((void *)q.q_ops,  NULL);
 	test_equal((void *)queue_next(&q), (void *)NULL);
 
+	queue_iter_init(&q, &it);
+	g_assert_null(it.it_iter);
+	g_assert_cmpuint(it.it_pos, ==, (unsigned int)-1);
+	g_assert_null(queue_iter_val(&it));
+
 	queue_deinit(&q);
 	test_equal(count_deinit, 0);
 
@@ -193,6 +199,7 @@ static void test_stress(unsigned int N)
 {
 	unsigned int ex_length = 0;
 	unsigned int ex_size   = N;
+	struct queue_iter it;
 	struct track *track;
 	unsigned int i;
 	struct queue q;
@@ -214,6 +221,23 @@ static void test_stress(unsigned int N)
 	test_equal(q.q_length,     ex_length);
 	test_equal(queue_size(&q), ex_size);
 
+	/* queue_iter_init() */
+	if (N > 0) {
+		queue_iter_init(&q, &it);
+		g_assert_nonnull(it.it_iter);
+		g_assert_cmpuint(it.it_pos, ==, 0);
+	}
+
+	/* queue_for_each() */
+	i = 0;
+	queue_for_each(&q, &it) {
+		g_assert_cmpuint(it.it_pos, ==, i);
+		g_assert(queue_iter_val(&it) == track_get(i % 13));
+		i++;
+	}
+	g_assert_cmpuint(i, ==, N);
+	g_assert_cmpuint(queue_size(&q), ==, ex_size);
+
 	/* queue_remove_all() */
 	track = track_get(0);
 	ex_length -= track->tr_length * (N / 13);