X-Git-Url: http://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Flist%2Flist.h;h=5c9aa2a689ca38af5a03c5c7c928381bf7b3c443;hb=87f505a56eae7ef2a03a76b5b412d6bc46c58aae;hp=da2ac73537b6c9d46d67df62c51faa330c927e70;hpb=edfbb7f2d2dcd951e563fc2fe5bf2ab9603ae605;p=ccan

diff --git a/ccan/list/list.h b/ccan/list/list.h
index da2ac735..5c9aa2a6 100644
--- a/ccan/list/list.h
+++ b/ccan/list/list.h
@@ -1,8 +1,10 @@
+/* Licensed under LGPLv2.1+ - see LICENSE file for details */
 #ifndef CCAN_LIST_H
 #define CCAN_LIST_H
 #include <stdbool.h>
 #include <assert.h>
 #include <ccan/container_of/container_of.h>
+#include <ccan/check_type/check_type.h>
 
 /**
  * struct list_node - an entry in a doubly-linked list
@@ -278,8 +280,15 @@ static inline void list_del_from(struct list_head *h, struct list_node *n)
  *	struct child *first;
  *	first = list_top(&parent->children, struct child, list);
  */
-#define list_top(h, type, member) \
-	(list_empty(h) ? NULL : list_entry((h)->n.next, type, member))
+#define list_top(h, type, member)					\
+	((type *)list_top_((h), list_off_(type, member)))
+
+static inline const void *list_top_(const struct list_head *h, size_t off)
+{
+	if (list_empty(h))
+		return NULL;
+	return (const char *)h->n.next - off;
+}
 
 /**
  * list_tail - get the last entry in a list
@@ -294,11 +303,18 @@ static inline void list_del_from(struct list_head *h, struct list_node *n)
  *	last = list_tail(&parent->children, struct child, list);
  */
 #define list_tail(h, type, member) \
-	(list_empty(h) ? NULL : list_entry((h)->n.prev, type, member))
+	((type *)list_tail_((h), list_off_(type, member)))
+
+static inline const void *list_tail_(const struct list_head *h, size_t off)
+{
+	if (list_empty(h))
+		return NULL;
+	return (const char *)h->n.prev - off;
+}
 
 /**
  * list_for_each - iterate through a list.
- * @h: the list_head
+ * @h: the list_head (warning: evaluated multiple times!)
  * @i: the structure containing the list_node
  * @member: the list_node member of the structure
  *
@@ -314,6 +330,24 @@ 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
@@ -337,4 +371,10 @@ static inline void list_del_from(struct list_head *h, struct list_node *n)
 		nxt = container_of_var(i->member.next, i, member);	\
 	     &i->member != &(h)->n;					\
 	     i = nxt, nxt = container_of_var(i->member.next, i, member))
+
+/* Get the offset of the member, but make sure it's a list_node. */
+#define list_off_(type, member)					\
+	(container_off(type, member) +				\
+	 check_type(((type *)0)->member, struct list_node))
+
 #endif /* CCAN_LIST_H */