include: add list_append()

The existing list_add() prepends to the list, but in some cases we need the
list ordered in the way we append the elements.

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>
Reviewed-by: Chase Douglas <chase.douglas@canonical.com>

include/list.h

@@ -159,6 +159,28 @@ list_add(struct list *entry, struct list *head)
     __list_add(entry, head, head->next);
 }
 
+/**
+ * Append a new element to the end of the list given with this list head.
+ *
+ * The list changes from:
+ *      head → some element → ... → lastelement
+ * to
+ *      head → some element → ... → lastelement → new element
+ *
+ * Example:
+ * struct foo *newfoo = malloc(...);
+ * list_append(&newfoo->mylist, &foo->mylist);
+ *
+ * @param entry The new element to prepend to the list.
+ * @param head The existing list.
+ */
+static inline void
+list_append(struct list *entry, struct list *head)
+{
+    __list_add(entry, head->prev, head);
+}
+
+
 static inline void
 __list_del(struct list *prev, struct list *next)
 {

test/list.c

@@ -88,6 +88,36 @@ test_list_add(void)
     assert(memcmp(c, &child[2], sizeof(struct child)) == 0);
 };
 
+static void
+test_list_append(void)
+{
+    struct parent parent = {0};
+    struct child child[3];
+    struct child *c;
+    int i;
+
+    list_init(&parent.children);
+
+    list_append(&child[0].node, &parent.children);
+    assert(!list_is_empty(&parent.children));
+
+    c = list_first_entry(&parent.children, struct child, node);
+    assert(memcmp(c, &child[0], sizeof(struct child)) == 0);
+
+    list_append(&child[1].node, &parent.children);
+    c = list_first_entry(&parent.children, struct child, node);
+    assert(memcmp(c, &child[0], sizeof(struct child)) == 0);
+
+    list_append(&child[2].node, &parent.children);
+    c = list_first_entry(&parent.children, struct child, node);
+    assert(memcmp(c, &child[0], sizeof(struct child)) == 0);
+
+    i = 0;
+    list_for_each_entry(c, &parent.children, node) {
+        assert(memcmp(c, &child[i++], sizeof(struct child)) == 0);
+    }
+};
+
 static void
 test_list_del(void)
 {
@@ -325,6 +355,7 @@ int main(int argc, char** argv)
 {
     test_list_init();
     test_list_add();
+    test_list_append();
     test_list_del();
     test_list_for_each();