New package: list, complete reimplementation of Linux's list macros.

list/_info.c

+#include <stdio.h>
+#include <string.h>
+#include "config.h"
+
+/**
+ * list - double linked list routines
+ *
+ * The list header contains routines for manipulating double linked lists.
+ * It defined two types: struct list_head used for anchoring lists, and
+ * struct list_node which is usually embedded in the structure which is placed
+ * in the list.
+ *
+ * Example:
+ *	#include <err.h>
+ *	#include "list/list.h"
+ *
+ *	struct parent {
+ *		const char *name;
+ *		struct list_head children;
+ *		unsigned int num_children;
+ *	};
+ *
+ *	struct child {
+ *		const char *name;
+ *		struct list_node list;
+ *	};
+ *
+ *	int main(int argc, char *argv[])
+ *	{
+ *		struct parent p;
+ *		struct child *c;
+ *		unsigned int i;
+ *
+ *		if (argc < 2)
+ *			errx(1, "Usage: %s parent children...", argv[0]);
+ *
+ *		p.name = argv[1];
+ *		for (i = 2; i < argc, i++) {
+ *			c = malloc(sizeof(*c));
+ *			c->name = argv[i];
+ *			list_add(&p.children, &c->list);
+ *			p.num_children++;
+ *		}
+ *
+ *		printf("%s has %u children:", p.name, p.num_children);
+ *		list_for_each(&p.children, c, list)
+ *			printf("%s ", c->name);
+ *		printf("\n");
+ *		return 0;
+ *	}
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		printf("container_of\n");
+		return 0;
+	}
+
+	return 1;
+}

list/list.c

+#include <stdio.h>
+#include <stdlib.h>
+#include "list/list.h"
+
+struct list_head *list_check(struct list_head *h, const char *abortstr)
+{
+	struct list_node *n, *p;
+	int count = 0;
+
+	if (h->n.next == &h->n) {
+		if (h->n.prev != &h->n) {
+			if (!abortstr)
+				return NULL;
+			fprintf(stderr, "%s: prev corrupt in empty %p\n",
+				abortstr, h);
+			abort();
+		}
+		return h;
+	}
+
+	for (p = &h->n, n = h->n.next; n != &h->n; p = n, n = n->next) {
+		count++;
+		if (n->prev != p) {
+			if (!abortstr)
+				return NULL;
+			fprintf(stderr,
+				"%s: prev corrupt in node %p (%u) of %p\n",
+				abortstr, n, count, h);
+			abort();
+		}
+	}
+	return h;
+}

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 */

list/test/run.c

+#include "list/list.h"
+#include "tap.h"
+#include "list/list.c"
+
+struct parent {
+	const char *name;
+	struct list_head children;
+	unsigned int num_children;
+};
+
+struct child {
+	const char *name;
+	struct list_node list;
+};
+
+static LIST_HEAD(static_list);
+
+int main(int argc, char *argv[])
+{
+	struct parent parent;
+	struct child c1, c2, c3, *c, *n;
+	unsigned int i;
+
+	plan_tests(41);
+	/* Test LIST_HEAD, list_empty and check_list */
+	ok1(list_empty(&static_list));
+	ok1(list_check(&static_list, NULL));
+
+	parent.num_children = 0;
+	list_head_init(&parent.children);
+	/* Test list_head_init */
+	ok1(list_empty(&parent.children));
+	ok1(list_check(&parent.children, NULL));
+
+	c2.name = "c2";
+	list_add(&parent.children, &c2.list);
+	/* Test list_add and !list_empty. */
+	ok1(!list_empty(&parent.children));
+	ok1(c2.list.next == &parent.children.n);
+	ok1(c2.list.prev == &parent.children.n);
+	ok1(parent.children.n.next == &c2.list);
+	ok1(parent.children.n.prev == &c2.list);
+	/* Test list_check */
+	ok1(list_check(&parent.children, NULL));
+
+	c1.name = "c1";
+	list_add(&parent.children, &c1.list);
+	/* Test list_add and !list_empty. */
+	ok1(!list_empty(&parent.children));
+	ok1(c2.list.next == &parent.children.n);
+	ok1(c2.list.prev == &c1.list);
+	ok1(parent.children.n.next == &c1.list);
+	ok1(parent.children.n.prev == &c2.list);
+	ok1(c1.list.next == &c2.list);
+	ok1(c1.list.prev == &parent.children.n);
+	/* Test list_check */
+	ok1(list_check(&parent.children, NULL));
+
+	c3.name = "c3";
+	list_add_tail(&parent.children, &c3.list);
+	/* Test list_add_tail and !list_empty. */
+	ok1(!list_empty(&parent.children));
+	ok1(parent.children.n.next == &c1.list);
+	ok1(parent.children.n.prev == &c3.list);
+	ok1(c1.list.next == &c2.list);
+	ok1(c1.list.prev == &parent.children.n);
+	ok1(c2.list.next == &c3.list);
+	ok1(c2.list.prev == &c1.list);
+	ok1(c3.list.next == &parent.children.n);
+	ok1(c3.list.prev == &c2.list);
+	/* Test list_check */
+	ok1(list_check(&parent.children, NULL));
+
+	/* Test list_top */
+	ok1(list_top(&parent.children, struct child, list) == &c1);
+
+	/* Test list_for_each. */
+	i = 0;
+	list_for_each(&parent.children, c, list) {
+		switch (i++) {
+		case 0:
+			ok1(c == &c1);
+			break;
+		case 1:
+			ok1(c == &c2);
+			break;
+		case 2:
+			ok1(c == &c3);
+			break;
+		}
+		if (i > 2)
+			break;
+	}
+	ok1(i == 3);
+
+	/* Test list_for_each_safe and list_del. */
+	i = 0;
+	list_for_each_safe(&parent.children, c, n, list) {
+		switch (i++) {
+		case 0:
+			ok1(c == &c1);
+			break;
+		case 1:
+			ok1(c == &c2);
+			break;
+		case 2:
+			ok1(c == &c3);
+			break;
+		}
+		list_del(&c->list);
+		ok1(list_check(&parent.children, NULL));
+		if (i > 2)
+			break;
+	}
+	ok1(i == 3);
+	ok1(list_empty(&parent.children));
+	return exit_status();
+}