2 * Copyright (c) 2008, 2009, 2010, 2011, 2013, 2015 Nicira, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
19 /* Doubly linked list. */
24 #include "openvswitch/list.h"
26 static inline void list_init(struct ovs_list *);
27 static inline void list_poison(struct ovs_list *);
30 static inline void list_insert(struct ovs_list *, struct ovs_list *);
31 static inline void list_splice(struct ovs_list *before, struct ovs_list *first,
32 struct ovs_list *last);
33 static inline void list_push_front(struct ovs_list *, struct ovs_list *);
34 static inline void list_push_back(struct ovs_list *, struct ovs_list *);
35 static inline void list_replace(struct ovs_list *, const struct ovs_list *);
36 static inline void list_moved(struct ovs_list *, const struct ovs_list *orig);
37 static inline void list_move(struct ovs_list *dst, struct ovs_list *src);
40 static inline struct ovs_list *list_remove(struct ovs_list *);
41 static inline struct ovs_list *list_pop_front(struct ovs_list *);
42 static inline struct ovs_list *list_pop_back(struct ovs_list *);
45 static inline struct ovs_list *list_front(const struct ovs_list *);
46 static inline struct ovs_list *list_back(const struct ovs_list *);
48 /* List properties. */
49 static inline size_t list_size(const struct ovs_list *);
50 static inline bool list_is_empty(const struct ovs_list *);
51 static inline bool list_is_singleton(const struct ovs_list *);
52 static inline bool list_is_short(const struct ovs_list *);
54 #define LIST_FOR_EACH(ITER, MEMBER, LIST) \
55 for (INIT_CONTAINER(ITER, (LIST)->next, MEMBER); \
56 &(ITER)->MEMBER != (LIST); \
57 ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.next, MEMBER))
58 #define LIST_FOR_EACH_CONTINUE(ITER, MEMBER, LIST) \
59 for (INIT_CONTAINER(ITER, (ITER)->MEMBER.next, MEMBER); \
60 &(ITER)->MEMBER != (LIST); \
61 ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.next, MEMBER))
62 #define LIST_FOR_EACH_REVERSE(ITER, MEMBER, LIST) \
63 for (INIT_CONTAINER(ITER, (LIST)->prev, MEMBER); \
64 &(ITER)->MEMBER != (LIST); \
65 ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.prev, MEMBER))
66 #define LIST_FOR_EACH_REVERSE_CONTINUE(ITER, MEMBER, LIST) \
67 for (ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.prev, MEMBER); \
68 &(ITER)->MEMBER != (LIST); \
69 ASSIGN_CONTAINER(ITER, (ITER)->MEMBER.prev, MEMBER))
70 #define LIST_FOR_EACH_SAFE(ITER, NEXT, MEMBER, LIST) \
71 for (INIT_CONTAINER(ITER, (LIST)->next, MEMBER); \
72 (&(ITER)->MEMBER != (LIST) \
73 ? INIT_CONTAINER(NEXT, (ITER)->MEMBER.next, MEMBER), 1 \
76 #define LIST_FOR_EACH_POP(ITER, MEMBER, LIST) \
77 while (!list_is_empty(LIST) \
78 && (INIT_CONTAINER(ITER, list_pop_front(LIST), MEMBER), 1))
80 /* Inline implementations. */
82 /* Initializes 'list' as an empty list. */
84 list_init(struct ovs_list *list)
86 list->next = list->prev = list;
89 /* Initializes 'list' with pointers that will (probably) cause segfaults if
90 * dereferenced and, better yet, show up clearly in a debugger. */
92 list_poison(struct ovs_list *list)
94 memset(list, 0xcc, sizeof *list);
97 /* Inserts 'elem' just before 'before'. */
99 list_insert(struct ovs_list *before, struct ovs_list *elem)
101 elem->prev = before->prev;
103 before->prev->next = elem;
107 /* Removes elements 'first' though 'last' (exclusive) from their current list,
108 then inserts them just before 'before'. */
110 list_splice(struct ovs_list *before, struct ovs_list *first, struct ovs_list *last)
117 /* Cleanly remove 'first'...'last' from its current list. */
118 first->prev->next = last->next;
119 last->next->prev = first->prev;
121 /* Splice 'first'...'last' into new list. */
122 first->prev = before->prev;
124 before->prev->next = first;
128 /* Inserts 'elem' at the beginning of 'list', so that it becomes the front in
131 list_push_front(struct ovs_list *list, struct ovs_list *elem)
133 list_insert(list->next, elem);
136 /* Inserts 'elem' at the end of 'list', so that it becomes the back in
139 list_push_back(struct ovs_list *list, struct ovs_list *elem)
141 list_insert(list, elem);
144 /* Puts 'elem' in the position currently occupied by 'position'.
145 * Afterward, 'position' is not part of a list. */
147 list_replace(struct ovs_list *element, const struct ovs_list *position)
149 element->next = position->next;
150 element->next->prev = element;
151 element->prev = position->prev;
152 element->prev->next = element;
155 /* Adjusts pointers around 'list' to compensate for 'list' having been moved
156 * around in memory (e.g. as a consequence of realloc()), with original
159 * ('orig' likely points to freed memory, but this function does not
160 * dereference 'orig', it only compares it to 'list'. In a very pedantic
161 * language lawyer sense, this still yields undefined behavior, but it works
162 * with actual compilers.) */
164 list_moved(struct ovs_list *list, const struct ovs_list *orig)
166 if (list->next == orig) {
169 list->prev->next = list->next->prev = list;
173 /* Initializes 'dst' with the contents of 'src', compensating for moving it
174 * around in memory. The effect is that, if 'src' was the head of a list, now
175 * 'dst' is the head of a list containing the same elements. */
177 list_move(struct ovs_list *dst, struct ovs_list *src)
180 list_moved(dst, src);
183 /* Removes 'elem' from its list and returns the element that followed it.
184 Undefined behavior if 'elem' is not in a list. */
185 static inline struct ovs_list *
186 list_remove(struct ovs_list *elem)
188 elem->prev->next = elem->next;
189 elem->next->prev = elem->prev;
193 /* Removes the front element from 'list' and returns it. Undefined behavior if
194 'list' is empty before removal. */
195 static inline struct ovs_list *
196 list_pop_front(struct ovs_list *list)
198 struct ovs_list *front = list->next;
204 /* Removes the back element from 'list' and returns it.
205 Undefined behavior if 'list' is empty before removal. */
206 static inline struct ovs_list *
207 list_pop_back(struct ovs_list *list)
209 struct ovs_list *back = list->prev;
215 /* Returns the front element in 'list_'.
216 Undefined behavior if 'list_' is empty. */
217 static inline struct ovs_list *
218 list_front(const struct ovs_list *list_)
220 struct ovs_list *list = CONST_CAST(struct ovs_list *, list_);
222 ovs_assert(!list_is_empty(list));
227 /* Returns the back element in 'list_'.
228 Undefined behavior if 'list_' is empty. */
229 static inline struct ovs_list *
230 list_back(const struct ovs_list *list_)
232 struct ovs_list *list = CONST_CAST(struct ovs_list *, list_);
234 ovs_assert(!list_is_empty(list));
239 /* Returns the number of elements in 'list'.
240 Runs in O(n) in the number of elements. */
242 list_size(const struct ovs_list *list)
244 const struct ovs_list *e;
247 for (e = list->next; e != list; e = e->next) {
253 /* Returns true if 'list' is empty, false otherwise. */
255 list_is_empty(const struct ovs_list *list)
257 return list->next == list;
260 /* Returns true if 'list' has exactly 1 element, false otherwise. */
262 list_is_singleton(const struct ovs_list *list)
264 return list_is_short(list) && !list_is_empty(list);
267 /* Returns true if 'list' has 0 or 1 elements, false otherwise. */
269 list_is_short(const struct ovs_list *list)
271 return list->next == list->prev;