linked_list: Implement linked_list_take

common/linked_list.c

@@ -32,3 +32,17 @@ bool linked_list_empty(struct linked_list *list) {
 	assert(list->prev != NULL && list->next != NULL);
 	return list->next == list;
 }
+
+void linked_list_take(struct linked_list *target, struct linked_list *source) {
+	if (linked_list_empty(source)) {
+		linked_list_init(target);
+		return;
+	}
+
+	target->next = source->next;
+	target->prev = source->prev;
+	target->next->prev = target;
+	target->prev->next = target;
+
+	linked_list_init(source);
+}

include/linked_list.h

@@ -12,5 +12,6 @@ void linked_list_init(struct linked_list *list);
 void linked_list_insert(struct linked_list *list, struct linked_list *elem);
 void linked_list_remove(struct linked_list *elem);
 bool linked_list_empty(struct linked_list *list);
+void linked_list_take(struct linked_list *target, struct linked_list *source);
 
 #endif

libseat/backend/seatd.c

@@ -204,14 +204,8 @@ static int queue_event(struct backend_seatd *backend, int opcode) {
 }
 
 static void execute_events(struct backend_seatd *backend) {
-	struct linked_list list = {
+	struct linked_list list;
-		.next = backend->pending_events.next,
+	linked_list_take(&list, &backend->pending_events);
-		.prev = backend->pending_events.prev,
-	};
-	list.next->prev = &list;
-	list.prev->next = &list;
-
-	linked_list_init(&backend->pending_events);
 	while (!linked_list_empty(&list)) {
 		struct pending_event *ev = (struct pending_event *)list.next;
 		int opcode = ev->opcode;

tests/linked_list.c

@@ -201,6 +201,47 @@ static void test_linked_list_loop_iterate(void) {
 	assert(cnt == 3);
 }
 
+static void test_linked_list_take_empty(void) {
+	struct linked_list list1, list2;
+	linked_list_init(&list1);
+
+	linked_list_take(&list2, &list1);
+
+	assert(linked_list_empty(&list1));
+	assert(linked_list_empty(&list2));
+}
+
+static void test_linked_list_take_single(void) {
+	struct linked_list list1, list2;
+	linked_list_init(&list1);
+
+	struct list_elem elem1 = {{0}, NULL};
+	linked_list_insert(&list1, &elem1.link);
+
+	linked_list_take(&list2, &list1);
+
+	assert(linked_list_empty(&list1));
+	assert(list2.next == &elem1.link && list2.prev == &elem1.link);
+	assert(elem1.link.next == &list2 && elem1.link.prev == &list2);
+}
+
+static void test_linked_list_take_many(void) {
+	struct linked_list list1, list2;
+	linked_list_init(&list1);
+
+	struct list_elem elem1 = {{0}, NULL};
+	struct list_elem elem2 = {{0}, NULL};
+	linked_list_insert(&list1, &elem2.link);
+	linked_list_insert(&list1, &elem1.link);
+
+	linked_list_take(&list2, &list1);
+
+	assert(linked_list_empty(&list1));
+	assert(list2.next == &elem1.link && list2.prev == &elem2.link);
+	assert(elem1.link.next == &elem2.link && elem1.link.prev == &list2);
+	assert(elem2.link.next == &list2 && elem2.link.prev == &elem1.link);
+}
+
 int main(int argc, char *argv[]) {
 	(void)argc;
 	(void)argv;
@@ -214,6 +255,9 @@ int main(int argc, char *argv[]) {
 	test_linked_list_remove_loop();
 	test_linked_list_manual_iterate();
 	test_linked_list_loop_iterate();
+	test_linked_list_take_empty();
+	test_linked_list_take_single();
+	test_linked_list_take_many();
 
 	return 0;
 }