list: implement list_for_each_rev()

diff --git a/ccan/list/list.h b/ccan/list/list.h
index 18f077aec20418c65711230ff051bc85670a2cbb..bda2922bc37b7b8dc22ec5482b5e6d75513c1eb7 100644 (file)
--- a/ccan/list/list.h
+++ b/ccan/list/list.h
@@ -315,6 +315,24 @@ static inline void list_del_from(struct list_head *h, struct list_node *n)
             &i->member != &(h)->n;                                     \
             i = container_of_var(i->member.next, i, member))
 
+/**
+ * list_for_each_rev - iterate through a list backwards.
+ * @h: the list_head
+ * @i: the structure containing the list_node
+ * @member: the list_node member of the structure
+ *
+ * This is a convenient wrapper to iterate @i over the entire list.  It's
+ * a for loop, so you can break and continue as normal.
+ *
+ * Example:
+ *     list_for_each_rev(&parent->children, child, list)
+ *             printf("Name: %s\n", child->name);
+ */
+#define list_for_each_rev(h, i, member)                                        \
+       for (i = container_of_var(list_debug(h)->n.prev, i, member);    \
+            &i->member != &(h)->n;                                     \
+            i = container_of_var(i->member.prev, i, member))
+
 /**
  * list_for_each_safe - iterate through a list, maybe during deletion
  * @h: the list_head

diff --git a/ccan/list/test/run.c b/ccan/list/test/run.c
index f80e364a276c1dd466737a80186db60f99cc57f3..4ac2dcda34e3eb5ebdc50aca20ea8ac1e379505a 100644 (file)
--- a/ccan/list/test/run.c
+++ b/ccan/list/test/run.c
@@ -22,7 +22,7 @@ int main(int argc, char *argv[])
        unsigned int i;
        struct list_head list = LIST_HEAD_INIT(list);
 
-       plan_tests(49);
+       plan_tests(53);
        /* Test LIST_HEAD, LIST_HEAD_INIT, list_empty and check_list */
        ok1(list_empty(&static_list));
        ok1(list_check(&static_list, NULL));
@@ -104,6 +104,25 @@ int main(int argc, char *argv[])
        }
        ok1(i == 3);
 
+       /* Test list_for_each_rev. */
+       i = 0;
+       list_for_each_rev(&parent.children, c, list) {
+               switch (i++) {
+               case 0:
+                       ok1(c == &c3);
+                       break;
+               case 1:
+                       ok1(c == &c2);
+                       break;
+               case 2:
+                       ok1(c == &c1);
+                       break;
+               }
+               if (i > 2)
+                       break;
+       }
+       ok1(i == 3);
+
        /* Test list_for_each_safe, list_del and list_del_from. */
        i = 0;
        list_for_each_safe(&parent.children, c, n, list) {