X-Git-Url: https://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Flist%2Flist.h;h=4a18f02d9c90e6465781582f54996afd402f6ee6;hp=58c0a97c43246185e2dcb17adb103a922f19e277;hb=7b1223717acffcdbbc7d0545cd3ce4a9935278ea;hpb=a8b248ea9de55316cac4423a99a727ca7b54e0fc

diff --git a/ccan/list/list.h b/ccan/list/list.h
index 58c0a97c..4a18f02d 100644
--- a/ccan/list/list.h
+++ b/ccan/list/list.h
@@ -1,7 +1,10 @@
+/* Licensed under BSD-MIT - 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
@@ -39,7 +42,7 @@ struct list_head
 };
 
 /**
- * list_check - check a list for consistency
+ * list_check - check head of a list for consistency
  * @h: the list_head
  * @abortstr: the location to print on aborting, or NULL.
  *
@@ -51,54 +54,93 @@ struct list_head
  * Returns the list head if the list is consistent, NULL if not (it
  * can never return NULL if @abortstr is set).
  *
+ * See also: list_check_node()
+ *
  * Example:
  *	static void dump_parent(struct parent *p)
  *	{
  *		struct child *c;
  *
- *		printf("%s (%u children):\n", p->name, parent->num_children);
+ *		printf("%s (%u children):\n", p->name, p->num_children);
  *		list_check(&p->children, "bad child list");
  *		list_for_each(&p->children, c, list)
  *			printf(" -> %s\n", c->name);
  *	}
  */
-struct list_head *list_check(struct list_head *h, const char *abortstr);
+struct list_head *list_check(const struct list_head *h, const char *abortstr);
+
+/**
+ * list_check_node - check node of a list for consistency
+ * @n: the list_node
+ * @abortstr: the location to print on aborting, or NULL.
+ *
+ * Check consistency of the list node is in (it must be in one).
+ *
+ * See also: list_check()
+ *
+ * Example:
+ *	static void dump_child(const struct child *c)
+ *	{
+ *		list_check_node(&c->list, "bad child list");
+ *		printf("%s\n", c->name);
+ *	}
+ */
+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_init - initialize a list_head
- * @h: the list_head to set to the empty list
+ * 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:
- *	list_head_init(&parent->children);
- *	parent->num_children = 0;
+ *	static struct list_head my_list = LIST_HEAD_INIT(my_list);
  */
-static inline void list_head_init(struct list_head *h)
-{
-	h->n.next = h->n.prev = &h->n;
-}
+#define LIST_HEAD_INIT(name) { { &name.n, &name.n } }
 
 /**
- * LIST_HEAD - define and initalized empty list_head
+ * 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.
  *
- * Example:
- *	// Header:
- *	extern struct list_head my_list;
+ * See also:
+ *	LIST_HEAD_INIT, list_head_init()
  *
- *	// C file:
- *	LIST_HEAD(my_list);
+ * 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
+ * @h: the list_head to set to the empty list
+ *
+ * Example:
+ *	...
+ *	struct parent *parent = malloc(sizeof(*parent));
+ *
+ *	list_head_init(&parent->children);
+ *	parent->num_children = 0;
+ */
+static inline void list_head_init(struct list_head *h)
+{
+	h->n.next = h->n.prev = &h->n;
+}
 
 /**
  * list_add - add an entry at the start of a linked list.
@@ -107,6 +149,9 @@ static inline void list_head_init(struct list_head *h)
  *
  * The list_node does not need to be initialized; it will be overwritten.
  * Example:
+ *	struct child *child = malloc(sizeof(*child));
+ *
+ *	child->name = "marvin";
  *	list_add(&parent->children, &child->list);
  *	parent->num_children++;
  */
@@ -116,7 +161,7 @@ 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);
 }
 
 /**
@@ -135,22 +180,43 @@ 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_del - delete an entry from a linked list.
+ * 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 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;
@@ -158,18 +224,33 @@ 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(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);
 }
 
 /**
@@ -179,9 +260,11 @@ static inline bool list_empty(struct list_head *h)
  * @member: the list_node member of the type
  *
  * Example:
- *	struct child *c;
  *	// First list entry is children.next; convert back to child.
- *	c = list_entry(parent->children.next, struct child, list);
+ *	child = list_entry(parent->children.n.next, struct child, list);
+ *
+ * See Also:
+ *	list_top(), list_for_each()
  */
 #define list_entry(n, type, member) container_of(n, type, member)
 
@@ -197,20 +280,41 @@ static inline bool list_empty(struct list_head *h)
  *	struct child *first;
  *	first = list_top(&parent->children, struct child, list);
  */
-#define list_top(h, type, member) \
-	list_entry(_list_top(h), type, member)	
+#define list_top(h, type, member)					\
+	((type *)list_top_((h), list_off_(type, member)))
 
-static inline struct list_node *_list_top(struct list_head *h)
+static inline const void *list_top_(const struct list_head *h, size_t off)
 {
-	(void)debug_list(h);
 	if (list_empty(h))
 		return NULL;
-	return h->n.next;
+	return (const char *)h->n.next - off;
 }
 
 /**
- * list_for_each - iterate through a list.
+ * list_tail - get the last entry in a list
  * @h: the list_head
+ * @type: the type of the entry
+ * @member: the list_node member of the type
+ *
+ * If the list is empty, returns NULL.
+ *
+ * Example:
+ *	struct child *last;
+ *	last = list_tail(&parent->children, struct child, list);
+ */
+#define list_tail(h, 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 (warning: evaluated multiple times!)
  * @i: the structure containing the list_node
  * @member: the list_node member of the structure
  *
@@ -218,14 +322,29 @@ static inline struct list_node *_list_top(struct list_head *h)
  * a for loop, so you can break and continue as normal.
  *
  * Example:
- *	struct child *c;
- *	list_for_each(&parent->children, c, list)
- *		printf("Name: %s\n", c->name);
+ *	list_for_each(&parent->children, child, list)
+ *		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);	\
+	list_for_each_off(h, i, list_off_var_(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.next, i, member))
+	     i = container_of_var(i->member.prev, i, member))
 
 /**
  * list_for_each_safe - iterate through a list, maybe during deletion
@@ -239,15 +358,112 @@ static inline struct list_node *_list_top(struct list_head *h)
  * @nxt is used to hold the next element, so you can delete @i from the list.
  *
  * Example:
- *	struct child *c, *n;
- *	list_for_each_safe(&parent->children, c, n, list) {
- *		list_del(&c->list);
+ *	struct child *next;
+ *	list_for_each_safe(&parent->children, child, next, list) {
+ *		list_del(&child->list);
  *		parent->num_children--;
  *	}
  */
 #define list_for_each_safe(h, i, nxt, member)				\
-	for (i = container_of_var(debug_list(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))
+	list_for_each_safe_off(h, i, nxt, list_off_var_(i, member))
+
+/**
+ * list_for_each_off - iterate through a list of memory regions.
+ * @h: the list_head
+ * @i: the pointer to a memory region wich contains list node data.
+ * @off: offset(relative to @i) at which list node data resides.
+ *
+ * This is a low-level wrapper to iterate @i over the entire list, used to
+ * implement all oher, more high-level, for-each constructs. It's a for loop,
+ * so you can break and continue as normal.
+ *
+ * WARNING! Being the low-level macro that it is, this wrapper doesn't know
+ * nor care about the type of @i. The only assumtion made is that @i points
+ * to a chunk of memory that at some @offset, relative to @i, contains a
+ * properly filled `struct node_list' which in turn contains pointers to
+ * memory chunks and it's turtles all the way down. Whith all that in mind
+ * remember that given the wrong pointer/offset couple this macro will
+ * happilly churn all you memory untill SEGFAULT stops it, in other words
+ * caveat emptor.
+ *
+ * It is worth mentioning that one of legitimate use-cases for that wrapper
+ * is operation on opaque types with known offset for `struct list_node'
+ * member(preferably 0), because it allows you not to disclose the type of
+ * @i.
+ *
+ * Example:
+ *	list_for_each_off(&parent->children, child,
+ *				offsetof(struct child, list))
+ *		printf("Name: %s\n", child->name);
+ */
+#define list_for_each_off(h, i, off)                                    \
+  for (i = list_node_to_off_(list_debug(h)->n.next, (off));             \
+       list_node_from_off_((void *)i, (off)) != &(h)->n;                \
+       i = list_node_to_off_(list_node_from_off_((void *)i, (off))->next, \
+                             (off)))
+
+/**
+ * list_for_each_safe_off - iterate through a list of memory regions, maybe
+ * during deletion
+ * @h: the list_head
+ * @i: the pointer to a memory region wich contains list node data.
+ * @nxt: the structure containing the list_node
+ * @off: offset(relative to @i) at which list node data resides.
+ *
+ * For details see `list_for_each_off' and `list_for_each_safe'
+ * descriptions.
+ *
+ * Example:
+ *	list_for_each_safe_off(&parent->children, child,
+ *		next, offsetof(struct child, list))
+ *		printf("Name: %s\n", child->name);
+ */
+#define list_for_each_safe_off(h, i, nxt, off)                          \
+  for (i = list_node_to_off_(list_debug(h)->n.next, (off)),             \
+         nxt = list_node_to_off_(list_node_from_off_(i, (off))->next,   \
+                                 (off));                                \
+       list_node_from_off_(i, (off)) != &(h)->n;                        \
+       i = nxt,                                                         \
+         nxt = list_node_to_off_(list_node_from_off_(i, (off))->next,   \
+                                 (off)))
+
+
+/* Other -off variants. */
+#define list_entry_off(n, type, off)		\
+	((type *)list_node_from_off_((n), (off)))
+
+#define list_head_off(h, type, off)		\
+	((type *)list_head_off((h), (off)))
+
+#define list_tail_off(h, type, off)		\
+	((type *)list_tail_((h), (off)))
+
+#define list_add_off(h, n, off)                 \
+	list_add((h), list_node_from_off_((n), (off)))
+
+#define list_del_off(n, off)                    \
+	list_del(list_node_from_off_((n), (off)))
+
+#define list_del_from_off(h, n, off)			\
+	list_del_from(h, list_node_from_off_((n), (off)))
+
+/* Offset helper functions so we only single-evaluate. */
+static inline void *list_node_to_off_(struct list_node *node, size_t off)
+{
+	return (void *)((char *)node - off);
+}
+static inline struct list_node *list_node_from_off_(void *ptr, size_t off)
+{
+	return (struct list_node *)((char *)ptr + off);
+}
+
+/* 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))
+
+#define list_off_var_(var, member)			\
+	(container_off_var(var, member) +		\
+	 check_type(var->member, struct list_node))
+
 #endif /* CCAN_LIST_H */