ccan/list/list.h

#ifndef CCAN_LIST_H
#define CCAN_LIST_H
#include <stdbool.h>
#include "container_of/container_of.h"

/**
 * struct list_node - an entry in a doubly-linked list
 * @next: next entry (self if empty)
 * @prev: previous entry (self if empty)
 *
 * This is used as an entry in a linked list.
 * Example:
 *	struct child {
 *		const char *name;
 *		// Linked list of all us children.
 *		struct list_node list;
 *	};
 */
struct list_node
{
	struct list_node *next, *prev;
};

/**
 * struct list_head - the head of a doubly-linked list
 * @h: the list_head (containing next and prev pointers)
 *
 * This is used as the head of a linked list.
 * Example:
 *	struct parent {
 *		const char *name;
 *		struct list_head children;
 *		unsigned int num_children;
 *	};
 */
struct list_head
{
	struct list_node n;
};

/**
 * list_check - check a list for consistency
 * @h: the list_head
 * @abortstr: the location to print on aborting, or NULL.
 *
 * Because list_nodes have redundant information, consistency checking between
 * the back and forward links can be done.  This is useful as a debugging check.
 * If @abortstr is non-NULL, that will be printed in a diagnostic if the list
 * is inconsistent, and the function will abort.
 *
 * Returns the list head if the list is consistent, NULL if not (it
 * can never return NULL if @abortstr is set).
 *
 * Example:
 *	static void dump_parent(struct parent *p)
 *	{
 *		struct child *c;
 *
 *		printf("%s (%u children):\n", p->name, parent->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);

#ifdef CCAN_LIST_DEBUG
#define debug_list(h) list_check((h), __func__)
#else
#define debug_list(h) (h)
#endif

/**
 * list_head_init - initialize a list_head
 * @h: the list_head to set to the empty list
 *
 * Example:
 *	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_HEAD - define and initalized 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;
 *
 *	// C file:
 *	LIST_HEAD(my_list);
 */
#define LIST_HEAD(name) \
	struct list_head name = { { &name.n, &name.n } }

/**
 * list_add - add an entry at the start of a linked list.
 * @h: the list_head to add the node to
 * @n: the list_node to add to the list.
 *
 * The list_node does not need to be initialized; it will be overwritten.
 * Example:
 *	list_add(&parent->children, &child->list);
 *	parent->num_children++;
 */
static inline void list_add(struct list_head *h, struct list_node *n)
{
	n->next = h->n.next;
	n->prev = &h->n;
	h->n.next->prev = n;
	h->n.next = n;
	(void)debug_list(h);
}

/**
 * list_add_tail - add an entry at the end of a linked list.
 * @h: the list_head to add the node to
 * @n: the list_node to add to the list.
 *
 * The list_node does not need to be initialized; it will be overwritten.
 * Example:
 *	list_add_tail(&parent->children, &child->list);
 *	parent->num_children++;
 */
static inline void list_add_tail(struct list_head *h, struct list_node *n)
{
	n->next = &h->n;
	n->prev = h->n.prev;
	h->n.prev->next = n;
	h->n.prev = n;
	(void)debug_list(h);
}

/**
 * list_del - delete an entry from a linked list.
 * @n: the list_node to delete from the list.
 *
 * Example:
 *	list_del(&child->list);
 *	parent->num_children--;
 */
static inline void list_del(struct list_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;
#endif
}

/**
 * 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(struct list_head *h)
{
	(void)debug_list(h);
	return h->n.next == &h->n;
}

/**
 * list_entry - convert a list_node back into the structure containing it.
 * @n: the list_node
 * @type: the type of the entry
 * @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);
 */
#define list_entry(n, type, member) container_of(n, type, member)

/**
 * list_top - get the first 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 *first;
 *	first = list_top(&parent->children, struct child, list);
 */
#define list_top(h, type, member) \
	list_entry(_list_top(h), type, member)	

static inline struct list_node *_list_top(struct list_head *h)
{
	(void)debug_list(h);
	if (list_empty(h))
		return NULL;
	return h->n.next;
}

/**
 * list_for_each - iterate through a list.
 * @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:
 *	struct child *c;
 *	list_for_each(&parent->children, c, list)
 *		printf("Name: %s\n", c->name);
 */
#define list_for_each(h, i, member)					\
	for (i = container_of_var(debug_list(h)->n.next, i, member);	\
	     &i->member != &(h)->n;					\
	     i = container_of_var(i->member.next, i, member))

/**
 * list_for_each_safe - iterate through a list, maybe during deletion
 * @h: the list_head
 * @i: the structure containing the list_node
 * @nxt: 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.  The extra variable
 * @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);
 *		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))
#endif /* CCAN_LIST_H */