ccan/list: new list_{del,node}_init functions

* ccan/list/list.h (list_del_init, list_node_init): new functions
  for multiple list_del() calls
  [ccan ec8654d94d3c5c47aa5f82698f7e8048c79765b1] (Rusty Russell)

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47577 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Sun Sep 14 08:41:44 2014  Eric Wong  <e@80x24.org>
+
+	* ccan/list/list.h (list_del_init, list_node_init): new functions
+	  for multiple list_del() calls
+	  [ccan ec8654d94d3c5c47aa5f82698f7e8048c79765b1] (Rusty Russell)
+
 Sat Sep 13 22:19:26 2014  Bernard Potocki  <bernard.potocki@imanel.org>
 
 	* hash.c (rb_hash_aset): fix misleading example which may suggest

ccan/list/list.h

@@ -91,6 +91,18 @@ static inline void list_head_init(struct list_head *h)
 	h->n.next = h->n.prev = &h->n;
 }
 
+/**
+ * list_node_init - initialize a list_node
+ * @n: the list_node to link to itself.
+ *
+ * You don't need to use this normally!  But it lets you list_del(@n)
+ * safely.
+ */
+static inline void list_node_init(struct list_node *n)
+{
+	n->next = n->prev = n;
+}
+
 /**
  * list_add - add an entry at the start of a linked list.
  * @h: the list_head to add the node to
@@ -183,7 +195,7 @@ static inline int list_empty_nodebug(const struct list_head *h)
  * another list, but not deleted again.
  *
  * See also:
- *	list_del_from()
+ *	list_del_from(), list_del_init()
  *
  * Example:
  *	list_del(&child->list);
@@ -201,6 +213,27 @@ static inline void list_del_(struct list_node *n, const char* abortstr)
 #endif
 }
 
+/**
+ * list_del_init - delete a node, and reset it so it can be deleted again.
+ * @n: the list_node to be deleted.
+ *
+ * list_del(@n) or list_del_init() again after this will be safe,
+ * which can be useful in some cases.
+ *
+ * See also:
+ *	list_del_from(), list_del()
+ *
+ * Example:
+ *	list_del_init(&child->list);
+ *	parent->num_children--;
+ */
+#define list_del_init(n) list_del_init_(n, LIST_LOC)
+static inline void list_del_init_(struct list_node *n, const char *abortstr)
+{
+	list_del_(n, abortstr);
+	list_node_init(n);
+}
+
 /**
  * list_del_from - delete an entry from a known linked list.
  * @h: the list_head the node is in.