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1/*
2 * Copyright (C) 2002 Free Software Foundation, Inc.
3 * (originally part of the GNU C Library and Userspace RCU)
4 * Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
5 *
6 * Copyright (C) 2009 Pierre-Marc Fournier
7 * Conversion to RCU list.
8 * Copyright (C) 2010 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
9 *
10 * This library is free software; you can redistribute it and/or
11 * modify it under the terms of the GNU Lesser General Public
12 * License as published by the Free Software Foundation; either
13 * version 2.1 of the License, or (at your option) any later version.
14 *
15 * This library is distributed in the hope that it will be useful,
16 * but WITHOUT ANY WARRANTY; without even the implied warranty of
17 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
18 * Lesser General Public License for more details.
19 *
20 * You should have received a copy of the GNU Lesser General Public
21 * License along with this library; if not, see
22 * <https://www.gnu.org/licenses/>.
23 */
24
25#ifndef LIST_H
26#define LIST_H 1
27
28/*
29 * The definitions of this file are adopted from those which can be
30 * found in the Linux kernel headers to enable people familiar with the
31 * latter find their way in these sources as well.
32 */
33
34/* Basic type for the double-link list. */
35struct list_head {
36 struct list_head *next, *prev;
37};
38
39/* avoid conflicts with BSD-only sys/queue.h */
40#undef LIST_HEAD
41/* Define a variable with the head and tail of the list. */
42#define LIST_HEAD(name) \
43 struct list_head name = { &(name), &(name) }
44
45/* Initialize a new list head. */
46#define INIT_LIST_HEAD(ptr) \
47 (ptr)->next = (ptr)->prev = (ptr)
48
49#define LIST_HEAD_INIT(name) { \
50 .next = &(name), \
51 .prev = &(name), \
52}
53
54/* Add new element at the head of the list. */
55static inline void list_add(struct list_head *newp, struct list_head *head)
56{
57 head->next->prev = newp;
58 newp->next = head->next;
59 newp->prev = head;
60 head->next = newp;
61}
62
63/* Add new element at the tail of the list. */
64static inline void list_add_tail(struct list_head *newp, struct list_head *head)
65{
66 head->prev->next = newp;
67 newp->next = head;
68 newp->prev = head->prev;
69 head->prev = newp;
70}
71
72/* Remove element from list. */
73static inline void __list_del(struct list_head *prev, struct list_head *next)
74{
75 next->prev = prev;
76 prev->next = next;
77}
78
79/* Remove element from list. */
80static inline void list_del(struct list_head *elem)
81{
82 __list_del(elem->prev, elem->next);
83}
84
85/* Remove element from list, initializing the element's list pointers. */
86static inline void list_del_init(struct list_head *elem)
87{
88 list_del(elem);
89 INIT_LIST_HEAD(elem);
90}
91
92/* Delete from list, add to another list as head. */
93static inline void list_move(struct list_head *elem, struct list_head *head)
94{
95 __list_del(elem->prev, elem->next);
96 list_add(elem, head);
97}
98
99/* Replace an old entry. */
100static inline void list_replace(struct list_head *old, struct list_head *newp)
101{
102 newp->next = old->next;
103 newp->prev = old->prev;
104 newp->prev->next = newp;
105 newp->next->prev = newp;
106}
107
108/* Join two lists. */
109static inline void list_splice(struct list_head *add, struct list_head *head)
110{
111 /* Do nothing if the list which gets added is empty. */
112 if (add != add->next) {
113 add->next->prev = head;
114 add->prev->next = head->next;
115 head->next->prev = add->prev;
116 head->next = add->next;
117 }
118}
119
120/* Get typed element from list at a given position. */
121#define list_entry(ptr, type, member) \
122 ((type *) ((char *) (ptr) - offsetof(type, member)))
123
124/* Get first entry from a list. */
125#define list_first_entry(ptr, type, member) \
126 list_entry((ptr)->next, type, member)
127
128/* Iterate forward over the elements of the list. */
129#define list_for_each(pos, head) \
130 for (pos = (head)->next; pos != (head); pos = pos->next)
131
132/*
133 * Iterate forward over the elements list. The list elements can be
134 * removed from the list while doing this.
135 */
136#define list_for_each_safe(pos, p, head) \
137 for (pos = (head)->next, p = pos->next; \
138 pos != (head); \
139 pos = p, p = pos->next)
140
141/* Iterate backward over the elements of the list. */
142#define list_for_each_prev(pos, head) \
143 for (pos = (head)->prev; pos != (head); pos = pos->prev)
144
145/*
146 * Iterate backwards over the elements list. The list elements can be
147 * removed from the list while doing this.
148 */
149#define list_for_each_prev_safe(pos, p, head) \
150 for (pos = (head)->prev, p = pos->prev; \
151 pos != (head); \
152 pos = p, p = pos->prev)
153
154static inline int list_empty(struct list_head *head)
155{
156 return head == head->next;
157}
158
159static inline void list_replace_init(struct list_head *old,
160 struct list_head *newp)
161{
162 struct list_head *head = old->next;
163
164 list_del(old);
165 list_add_tail(newp, head);
166 INIT_LIST_HEAD(old);
167}
168
169/*
170 * This is exactly the same as a normal list_head, except that it can be
171 * declared volatile (e.g., if you have a list that may be accessed from signal
172 * handlers).
173 */
174struct volatile_list_head {
175 volatile struct volatile_list_head *next, *prev;
176};
177
178#define VOLATILE_LIST_HEAD(name) \
179 volatile struct volatile_list_head name = { &(name), &(name) }
180
181static inline void __volatile_list_del(volatile struct volatile_list_head *prev,
182 volatile struct volatile_list_head *next)
183{
184 next->prev = prev;
185 prev->next = next;
186}
187
188static inline void volatile_list_del(volatile struct volatile_list_head *elem)
189{
190 __volatile_list_del(elem->prev, elem->next);
191}
192
193static inline int volatile_list_empty(volatile struct volatile_list_head *head)
194{
195 return head == head->next;
196}
197
198static inline void volatile_list_add(volatile struct volatile_list_head *newp,
199 volatile struct volatile_list_head *head)
200{
201 head->next->prev = newp;
202 newp->next = head->next;
203 newp->prev = head;
204 head->next = newp;
205}
206
207#endif /* LIST_H */