1 /* SPDX-License-Identifier: GPL-2.0 */
2 #ifndef LIST_H
3 #define LIST_H
4
5 #include <stddef.h>
6
7 #include "list_types.h"
8
9 /* Are two types/vars the same type (ignoring qualifiers)? */
10 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
11
12 /**
13 * container_of - cast a member of a structure out to the containing structure
14 * @ptr: the pointer to the member.
15 * @type: the type of the container struct this is embedded in.
16 * @member: the name of the member within the struct.
17 *
18 */
19 #define container_of(ptr, type, member) ({ \
20 void *__mptr = (void *)(ptr); \
21 _Static_assert(__same_type(*(ptr), ((type *)0)->member) || \
22 __same_type(*(ptr), void), \
23 "pointer type mismatch in container_of()"); \
24 ((type *)(__mptr - offsetof(type, member))); })
25
26 #define LIST_POISON1 ((void *) 0x100)
27 #define LIST_POISON2 ((void *) 0x122)
28
29 /*
30 * Circular doubly linked list implementation.
31 *
32 * Some of the internal functions ("__xxx") are useful when
33 * manipulating whole lists rather than single entries, as
34 * sometimes we already know the next/prev entries and we can
35 * generate better code by using them directly rather than
36 * using the generic single-entry routines.
37 */
38
39 #define LIST_HEAD_INIT(name) { &(name), &(name) }
40
41 #define LIST_HEAD(name) \
42 struct list_head name = LIST_HEAD_INIT(name)
43
44 /**
45 * INIT_LIST_HEAD - Initialize a list_head structure
46 * @list: list_head structure to be initialized.
47 *
48 * Initializes the list_head to point to itself. If it is a list header,
49 * the result is an empty list.
50 */
INIT_LIST_HEAD(struct list_head * list)51 static inline void INIT_LIST_HEAD(struct list_head *list)
52 {
53 list->next = list;
54 list->prev = list;
55 }
56
57 /*
58 * Insert a new entry between two known consecutive entries.
59 *
60 * This is only for internal list manipulation where we know
61 * the prev/next entries already!
62 */
__list_add(struct list_head * new,struct list_head * prev,struct list_head * next)63 static inline void __list_add(struct list_head *new,
64 struct list_head *prev,
65 struct list_head *next)
66 {
67 next->prev = new;
68 new->next = next;
69 new->prev = prev;
70 prev->next = new;
71 }
72
73 /**
74 * list_add - add a new entry
75 * @new: new entry to be added
76 * @head: list head to add it after
77 *
78 * Insert a new entry after the specified head.
79 * This is good for implementing stacks.
80 */
list_add(struct list_head * new,struct list_head * head)81 static inline void list_add(struct list_head *new, struct list_head *head)
82 {
83 __list_add(new, head, head->next);
84 }
85
86 /**
87 * list_add_tail - add a new entry
88 * @new: new entry to be added
89 * @head: list head to add it before
90 *
91 * Insert a new entry before the specified head.
92 * This is useful for implementing queues.
93 */
list_add_tail(struct list_head * new,struct list_head * head)94 static inline void list_add_tail(struct list_head *new, struct list_head *head)
95 {
96 __list_add(new, head->prev, head);
97 }
98
99 /*
100 * Delete a list entry by making the prev/next entries
101 * point to each other.
102 *
103 * This is only for internal list manipulation where we know
104 * the prev/next entries already!
105 */
__list_del(struct list_head * prev,struct list_head * next)106 static inline void __list_del(struct list_head *prev, struct list_head *next)
107 {
108 next->prev = prev;
109 prev->next = next;
110 }
111
__list_del_entry(struct list_head * entry)112 static inline void __list_del_entry(struct list_head *entry)
113 {
114 __list_del(entry->prev, entry->next);
115 }
116
117 /**
118 * list_del - deletes entry from list.
119 * @entry: the element to delete from the list.
120 * Note: list_empty() on entry does not return true after this, the entry is
121 * in an undefined state.
122 */
list_del(struct list_head * entry)123 static inline void list_del(struct list_head *entry)
124 {
125 __list_del_entry(entry);
126 entry->next = LIST_POISON1;
127 entry->prev = LIST_POISON2;
128 }
129
130 /**
131 * list_is_head - tests whether @list is the list @head
132 * @list: the entry to test
133 * @head: the head of the list
134 */
list_is_head(const struct list_head * list,const struct list_head * head)135 static inline int list_is_head(const struct list_head *list, const struct list_head *head)
136 {
137 return list == head;
138 }
139
140 /**
141 * list_empty - tests whether a list is empty
142 * @head: the list to test.
143 */
list_empty(const struct list_head * head)144 static inline int list_empty(const struct list_head *head)
145 {
146 return head->next == head;
147 }
148
149 /**
150 * list_entry - get the struct for this entry
151 * @ptr: the &struct list_head pointer.
152 * @type: the type of the struct this is embedded in.
153 * @member: the name of the list_head within the struct.
154 */
155 #define list_entry(ptr, type, member) \
156 container_of(ptr, type, member)
157
158 /**
159 * list_first_entry - get the first element from a list
160 * @ptr: the list head to take the element from.
161 * @type: the type of the struct this is embedded in.
162 * @member: the name of the list_head within the struct.
163 *
164 * Note, that list is expected to be not empty.
165 */
166 #define list_first_entry(ptr, type, member) \
167 list_entry((ptr)->next, type, member)
168
169 /**
170 * list_next_entry - get the next element in list
171 * @pos: the type * to cursor
172 * @member: the name of the list_head within the struct.
173 */
174 #define list_next_entry(pos, member) \
175 list_entry((pos)->member.next, typeof(*(pos)), member)
176
177 /**
178 * list_entry_is_head - test if the entry points to the head of the list
179 * @pos: the type * to cursor
180 * @head: the head for your list.
181 * @member: the name of the list_head within the struct.
182 */
183 #define list_entry_is_head(pos, head, member) \
184 (&pos->member == (head))
185
186 /**
187 * list_for_each_entry - iterate over list of given type
188 * @pos: the type * to use as a loop cursor.
189 * @head: the head for your list.
190 * @member: the name of the list_head within the struct.
191 */
192 #define list_for_each_entry(pos, head, member) \
193 for (pos = list_first_entry(head, typeof(*pos), member); \
194 !list_entry_is_head(pos, head, member); \
195 pos = list_next_entry(pos, member))
196
197 /**
198 * list_for_each_entry_safe - iterate over list of given type. Safe against removal of list entry
199 * @pos: the type * to use as a loop cursor.
200 * @n: another type * to use as temporary storage
201 * @head: the head for your list.
202 * @member: the name of the list_head within the struct.
203 */
204 #define list_for_each_entry_safe(pos, n, head, member) \
205 for (pos = list_first_entry(head, typeof(*pos), member), \
206 n = list_next_entry(pos, member); \
207 !list_entry_is_head(pos, head, member); \
208 pos = n, n = list_next_entry(n, member))
209
210 /*
211 * Double linked lists with a single pointer list head.
212 * Mostly useful for hash tables where the two pointer list head is
213 * too wasteful.
214 * You lose the ability to access the tail in O(1).
215 */
216
217 #define HLIST_HEAD_INIT { .first = NULL }
218
219 /**
220 * hlist_add_head - add a new entry at the beginning of the hlist
221 * @n: new entry to be added
222 * @h: hlist head to add it after
223 *
224 * Insert a new entry after the specified head.
225 * This is good for implementing stacks.
226 */
hlist_add_head(struct hlist_node * n,struct hlist_head * h)227 static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
228 {
229 struct hlist_node *first = h->first;
230
231 n->next = first;
232 if (first)
233 first->pprev = &n->next;
234 h->first = n;
235 n->pprev = &h->first;
236 }
237
238 #define hlist_entry(ptr, type, member) container_of(ptr, type, member)
239
240 #define hlist_entry_safe(ptr, type, member) \
241 ({ typeof(ptr) ____ptr = (ptr); \
242 ____ptr ? hlist_entry(____ptr, type, member) : NULL; \
243 })
244
245 /**
246 * hlist_for_each_entry - iterate over list of given type
247 * @pos: the type * to use as a loop cursor.
248 * @head: the head for your list.
249 * @member: the name of the hlist_node within the struct.
250 */
251 #define hlist_for_each_entry(pos, head, member) \
252 for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\
253 pos; \
254 pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))
255
256 #endif /* LIST_H */
257