X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Flist%2Flist.h;h=1feb58919142fc3bbe6d0eee23418ca52c27c6e9;hp=c4956a0d03814145a4d42e3b11a8bce93a611484;hb=c1e57dbfbd00dee590ab0403763796bff0e2eb2e;hpb=22ffb884ca6a5f16517e49e051d8fb5a22e5049d

diff --git a/ccan/list/list.h b/ccan/list/list.h
index c4956a0d..1feb5891 100644
--- a/ccan/list/list.h
+++ b/ccan/list/list.h
@@ -1,6 +1,8 @@
+/* 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>
 
 /**
@@ -86,23 +88,42 @@ struct list_node *list_check_node(const struct list_node *n,
 				  const char *abortstr);
 
 #ifdef CCAN_LIST_DEBUG
-#define debug_list(h) list_check((h), __func__)
+#define list_debug(h) list_check((h), __func__)
+#define list_debug_node(n) list_check_node((n), __func__)
 #else
-#define debug_list(h) (h)
+#define list_debug(h) (h)
+#define list_debug_node(n) (n)
 #endif
 
 /**
- * LIST_HEAD - define and initalize an empty list_head
+ * LIST_HEAD_INIT - initializer for an empty list_head
+ * @name: the name of the list.
+ *
+ * Explicit initializer for an empty list.
+ *
+ * See also:
+ *	LIST_HEAD, list_head_init()
+ *
+ * Example:
+ *	static struct list_head my_list = LIST_HEAD_INIT(my_list);
+ */
+#define LIST_HEAD_INIT(name) { { &name.n, &name.n } }
+
+/**
+ * LIST_HEAD - define and initialize an empty list_head
  * @name: the name of the list.
  *
  * The LIST_HEAD macro defines a list_head and initializes it to an empty
  * list.  It can be prepended by "static" to define a static list_head.
  *
+ * See also:
+ *	LIST_HEAD_INIT, list_head_init()
+ *
  * Example:
  *	static LIST_HEAD(my_global_list);
  */
 #define LIST_HEAD(name) \
-	struct list_head name = { { &name.n, &name.n } }
+	struct list_head name = LIST_HEAD_INIT(name)
 
 /**
  * list_head_init - initialize a list_head
@@ -139,7 +160,7 @@ static inline void list_add(struct list_head *h, struct list_node *n)
 	n->prev = &h->n;
 	h->n.next->prev = n;
 	h->n.next = n;
-	(void)debug_list(h);
+	(void)list_debug(h);
 }
 
 /**
@@ -158,22 +179,43 @@ static inline void list_add_tail(struct list_head *h, struct list_node *n)
 	n->prev = h->n.prev;
 	h->n.prev->next = n;
 	h->n.prev = n;
-	(void)debug_list(h);
+	(void)list_debug(h);
+}
+
+/**
+ * list_empty - is a list empty?
+ * @h: the list_head
+ *
+ * If the list is empty, returns true.
+ *
+ * Example:
+ *	assert(list_empty(&parent->children) == (parent->num_children == 0));
+ */
+static inline bool list_empty(const struct list_head *h)
+{
+	(void)list_debug(h);
+	return h->n.next == &h->n;
 }
 
 /**
- * list_del - delete an entry from a linked list.
+ * list_del - delete an entry from an (unknown) linked list.
  * @n: the list_node to delete from the list.
  *
+ * Note that this leaves @n in an undefined state; it can be added to
+ * another list, but not deleted again.
+ *
+ * See also:
+ *	list_del_from()
+ *
  * Example:
  *	list_del(&child->list);
  *	parent->num_children--;
  */
 static inline void list_del(struct list_node *n)
 {
+	(void)list_debug_node(n);
 	n->next->prev = n->prev;
 	n->prev->next = n->next;
-	(void)debug_list(n->next);
 #ifdef CCAN_LIST_DEBUG
 	/* Catch use-after-del. */
 	n->next = n->prev = NULL;
@@ -181,18 +223,33 @@ static inline void list_del(struct list_node *n)
 }
 
 /**
- * list_empty - is a list empty?
- * @h: the list_head
+ * list_del_from - delete an entry from a known linked list.
+ * @h: the list_head the node is in.
+ * @n: the list_node to delete from the list.
  *
- * If the list is empty, returns true.
+ * This explicitly indicates which list a node is expected to be in,
+ * which is better documentation and can catch more bugs.
+ *
+ * See also: list_del()
  *
  * Example:
- *	assert(list_empty(&parent->children) == (parent->num_children == 0));
+ *	list_del_from(&parent->children, &child->list);
+ *	parent->num_children--;
  */
-static inline bool list_empty(const struct list_head *h)
+static inline void list_del_from(struct list_head *h, struct list_node *n)
 {
-	(void)debug_list(h);
-	return h->n.next == &h->n;
+#ifdef CCAN_LIST_DEBUG
+	{
+		/* Thorough check: make sure it was in list! */
+		struct list_node *i;
+		for (i = h->n.next; i != n; i = i->next)
+			assert(i != &h->n);
+	}
+#endif /* CCAN_LIST_DEBUG */
+
+	/* Quick test that catches a surprising number of bugs. */
+	assert(!list_empty(h));
+	list_del(n);
 }
 
 /**
@@ -222,8 +279,15 @@ static inline bool list_empty(const struct list_head *h)
  *	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), container_off((h)->n.next, 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
@@ -238,11 +302,18 @@ static inline bool list_empty(const struct list_head *h)
  *	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), container_off((h)->n.next, 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
  *
@@ -254,10 +325,28 @@ static inline bool list_empty(const struct list_head *h)
  *		printf("Name: %s\n", child->name);
  */
 #define list_for_each(h, i, member)					\
-	for (i = container_of_var(debug_list(h)->n.next, i, member);	\
+	for (i = container_of_var(list_debug(h)->n.next, i, member);	\
 	     &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
@@ -277,7 +366,7 @@ static inline bool list_empty(const struct list_head *h)
  *	}
  */
 #define list_for_each_safe(h, i, nxt, member)				\
-	for (i = container_of_var(debug_list(h)->n.next, i, member),	\
+	for (i = container_of_var(list_debug(h)->n.next, i, member),	\
 		nxt = container_of_var(i->member.next, i, member);	\
 	     &i->member != &(h)->n;					\
 	     i = nxt, nxt = container_of_var(i->member.next, i, member))