学习/linux/list.h_双链表实现
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linux-3.5/include/linux/list.h
使用只含指针域的双向循环链表进行链表的操作。
下面是我选取部分list.h中代码：
1 #ifndef _LINUX_LIST_H 2 #define _LINUX_LIST_H 3 4 struct list_head { 5 struct list_head *next, *prev; 6 }; 7 /* 8 * Simple doubly linked list implementation. 9 * 10 * Some of the internal functions ("__xxx") are useful when 11 * manipulating whole lists rather than single entries, as 12 * sometimes we already know the next/prev entries and we can 13 * generate better code by using them directly rather than 14 * using the generic single-entry routines. 15 */ 16 17 #define LIST_HEAD_INIT(name) { &(name), &(name) } 18 19 #define LIST_HEAD(name) \\ 20 struct list_head name = LIST_HEAD_INIT(name) 21 22 static inline void INIT_LIST_HEAD(struct list_head *list) 23 { 24 list->next = list; 25 list->prev = list; 26 } 27 28 /* 29 * Insert a new entry between two known consecutive entries. 30 * 31 * This is only for internal list manipulation where we know 32 * the prev/next entries already! 33 */ 34 #ifndef CONFIG_DEBUG_LIST 35 static inline void __list_add(struct list_head *new, 36 struct list_head *prev, 37 struct list_head *next) 38 { 39 next->prev = new; 40 new->next = next; 41 new->prev = prev; 42 prev->next = new; 43 } 44 #else 45 extern void __list_add(struct list_head *new, 46 struct list_head *prev, 47 struct list_head *next); 48 #endif 49 50 /** 51 * list_add - add a new entry 52 * @new: new entry to be added 53 * @head: list head to add it after 54 * 55 * Insert a new entry after the specified head. 56 * This is good for implementing stacks. 57 */ 58 static inline void list_add(struct list_head *new, struct list_head *head) 59 { 60 __list_add(new, head, head->next); 61 } 62 63 64 /** 65 * list_add_tail - add a new entry 66 * @new: new entry to be added 67 * @head: list head to add it before 68 * 69 * Insert a new entry before the specified head. 70 * This is useful for implementing queues. 71 */ 72 static inline void list_add_tail(struct list_head *new, struct list_head *head) 73 { 74 __list_add(new, head->prev, head); 75 } 76 77 /* 78 * Delete a list entry by making the prev/next entries 79 * point to each other. 80 * 81 * This is only for internal list manipulation where we know 82 * the prev/next entries already! 83 */ 84 static inline void __list_del(struct list_head * prev, struct list_head * next) 85 { 86 next->prev = prev; 87 prev->next = next; 88 } 89 90 /** 91 * list_del - deletes entry from list. 92 * @entry: the element to delete from the list. 93 * Note: list_empty() on entry does not return true after this, the entry is 94 * in an undefined state. 95 */ 96 #ifndef CONFIG_DEBUG_LIST 97 static inline void __list_del_entry(struct list_head *entry) 98 { 99 __list_del(entry->prev, entry->next); 100 } 101 #endif 102 103 /** 104 * list_replace - replace old entry by new one 105 * @old : the element to be replaced 106 * @new : the new element to insert 107 * 108 * If @old was empty, it will be overwritten. 109 */ 110 static inline void list_replace(struct list_head *old, 111 struct list_head *new) 112 { 113 new->next = old->next; 114 new->next->prev = new; 115 new->prev = old->prev; 116 new->prev->next = new; 117 } 118 119 static inline void list_replace_init(struct list_head *old, 120 struct list_head *new) 121 { 122 list_replace(old, new); 123 INIT_LIST_HEAD(old); 124 } 125 126 /** 127 * list_del_init - deletes entry from list and reinitialize it. 128 * @entry: the element to delete from the list. 129 */ 130 static inline void list_del_init(struct list_head *entry) 131 { 132 __list_del_entry(entry); 133 INIT_LIST_HEAD(entry); 134 } 135 136 /** 137 * list_move - delete from one list and add as another\'s head 138 * @list: the entry to move 139 * @head: the head that will precede our entry 140 */ 141 static inline void list_move(struct list_head *list, struct list_head *head) 142 { 143 __list_del_entry(list); 144 list_add(list, head); 145 } 146 147 /** 148 * list_move_tail - delete from one list and add as another\'s tail 149 * @list: the entry to move 150 * @head: the head that will follow our entry 151 */ 152 static inline void list_move_tail(struct list_head *list, 153 struct list_head *head) 154 { 155 __list_del_entry(list); 156 list_add_tail(list, head); 157 } 158 159 /** 160 * list_is_last - tests whether @list is the last entry in list @head 161 * @list: the entry to test 162 * @head: the head of the list 163 */ 164 static inline int list_is_last(const struct list_head *list, 165 const struct list_head *head) 166 { 167 return list->next == head; 168 } 169 170 /** 171 * list_empty - tests whether a list is empty 172 * @head: the list to test. 173 */ 174 static inline int list_empty(const struct list_head *head) 175 { 176 return head->next == head; 177 } 178 179 /** 180 * list_empty_careful - tests whether a list is empty and not being modified 181 * @head: the list to test 182 * 183 * Description: 184 * tests whether a list is empty _and_ checks that no other CPU might be 185 * in the process of modifying either member (next or prev) 186 * 187 * NOTE: using list_empty_careful() without synchronization 188 * can only be safe if the only activity that can happen 189 * to the list entry is list_del_init(). Eg. it cannot be used 190 * if another CPU could re-list_add() it. 191 */ 192 static inline int list_empty_careful(const struct list_head *head) 193 { 194 struct list_head *next = head->next; 195 return (next == head) && (next == head->prev); 196 } 197 198 /** 199 * list_rotate_left - rotate the list to the left 200 * @head: the head of the list 201 */ 202 static inline void list_rotate_left(struct list_head *head) 203 { 204 struct list_head *first; 205 206 if (!list_empty(head)) { 207 first = head->next; 208 list_move_tail(first, head); 209 } 210 } 211 212 /** 213 * list_is_singular - tests whether a list has just one entry. 214 * @head: the list to test. 215 */ 216 static inline int list_is_singular(const struct list_head *head) 217 { 218 return !list_empty(head) && (head->next == head->prev); 219 } 220 221 static inline void __list_cut_position(struct list_head *list, 222 struct list_head *head, struct list_head *entry) 223 { 224 struct list_head *new_first = entry->next; 225 list->next = head->next; 226 list->next->prev = list; 227 list->prev = entry; 228 entry->next = list; 229 head->next = new_first; 230 new_first->prev = head; 231 } 232 233 /** 234 * list_cut_position - cut a list into two 235 * @list: a new list to add all removed entries 236 * @head: a list with entries 237 * @entry: an entry within head, could be the head itself 238 * and if so we won\'t cut the list 239 * 240 * This helper moves the initial part of @head, up to and 241 * including @entry, from @head to @list. You should 242 * pass on @entry an element you know is on @head. @list 243 * should be an empty list or a list you do not care about 244 * losing its data. 245 * 246 */ 247 static inline void list_cut_position(struct list_head *list, 248 struct list_head *head, struct list_head *entry) 249 { 250 if (list_empty(head)) 251 return; 252 if (list_is_singular(head) && 253 (head->next != entry && head != entry)) 254 return; 255 if (entry == head) 256 INIT_LIST_HEAD(list); 257 else 258 __list_cut_position(list, head, entry); 259 } 260 261 static inline void __list_splice(const struct list_head *list, 262 struct list_head *prev, 263 struct list_head *next) 264 { 265 struct list_head *first = list->next; 266 struct list_head *last = list->prev; 267 268 first->prev = prev; 269 prev->next = first; 270 271 last->next = next; 272 next->prev = last; 273 } 274 275 /** 276 * list_splice - join two lists, this is designed for stacks 277 * @list: the new list to add. 278 * @head: the place to add it in the first list. 279 */ 280 static inline void list_splice(const struct list_head *list, 281 struct list_head *head) 282 { 283 if (!list_empty(list)) 284 __list_splice(list, head, head->next); 285 } 286 287 /** 288 * list_splice_tail - join two lists, each list being a queue 289 * @list: the new list to add. 290 * @head: the place to add it in the first list. 291 */ 292 static inline void list_splice_tail(struct list_head *list, 293 struct list_head *head) 294 { 295 if (!list_empty(list)) 296 __list_splice(list, head->prev, head); 297 } 298 299 /** 300 * list_splice_init - join two lists and reinitialise the emptied list. 301 * @list: the new list to add. 302 * @head: the place to add it in the first list. 303 * 304 * The list at @list is reinitialised 305 */ 306 static inline void list_splice_init(struct list_head *list, 307 struct list_head *head) 308 { 309 if (!list_empty(list)) { 310 __list_splice(list, head, head->next); 311 INIT_LIST_HEAD(list); 312 } 313 } 314 315 /** 316 * list_splice_tail_init - join two lists and reinitialise the emptied list 317 * @list: the new list to add. 318 * @head: the place to add it in the first list. 319 * 320 * Each of the lists is a queue. 321 * The list at @list is reinitialised 322 */ 323 static inline void list_splice_tail_init(struct list_head *list, 324 struct list_head *head) 325 { 326 if (!list_empty(list)) { 327 __list_splice(list, head->prev, head); 328 INIT_LIST_HEAD(list); 329 } 330 } 331 332 /** 333 * list_entry - get the struct for this entry 334 * @ptr: the &struct list_head pointer. 335 * @type: the type of the struct this is embedded in. 336 * @member: the name of the list_struct within the struct. 337 */ 338 #define list_entry(ptr, type, member) \\ 339 container_of(ptr, type, member) 340 341 /** 342 * list_first_entry - get the first element from a list 343 * @ptr: the list head to take the element from. 344 * @type: the type of the struct this is embedded in. 345 * @member: the name of the list_struct within the struct. 346 * 347 * Note, that list is expected to be not empty. 348 */ 349 #define list_first_entry(ptr, type, member) \\ 350 list_entry((ptr)->next, type, member) 351 352 /** 353 * list_for_each - iterate over a list 354 * @pos: the &struct list_head to use as a loop cursor. 355 * @head: the head for your list. 356 */ 357 #define list_for_each(pos, head) \\ 358 for (pos = (head)->next; pos != (head); pos = pos->next) 359 360 /** 361 * __list_for_each - iterate over a list 362 * @pos: the &struct list_head to use as a loop cursor. 363 * @head: the head for your list. 364 * 365 * This variant doesn\'t differ from list_for_each() any more. 366 * We don\'t do prefetching in either case. 367 */ 368 #define __list_for_each(pos, head) \\ 369 for (pos = (head)->next; pos != (head); pos = pos->next) 370 371 /** 372 * list_for_each_prev - iterate over a list backwards 373 * @pos: the &struct list_head to use as a loop cursor. 374 * @head: the head for your list. 375 */ 376 #define list_for_each_prev(pos, head) \\ 377 for (pos = (head)->prev; pos != (head); pos = pos->prev) 378 379 /** 380 * list_for_each_safe - iterate over a list safe against removal of list entry 381 * @pos: the &struct list_head to use as a loop cursor. 382 * @n: another &struct list_head to use as temporary storage 383 * @head: the head for your list. 384 */ 385 #define list_for_each_safe(pos, n, head) \\ 386 for (pos = (head)->next, n = pos->next; pos != (head); \\ 387 pos = n, n = pos->next) 388 389 /** 390 * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry 391 * @pos: the &struct list_head to use as a loop cursor. 392 * @n: another &struct list_head to use as temporary storage 393 * @head: the head for your list. 394 */ 395 #define list_for_each_prev_safe(pos, n, head) \\ 396 for (pos = (head)->prev, n = pos->prev; \\ 397 pos != (head); \\ 398 pos = n, n = pos->prev) 399 400 /** 401 * list_for_each_entry - iterate over list of given type 402 * @pos: the type * to use as a loop cursor. 403 * @head: the head for your list. 404 * @member: the name of the list_struct within the struct. 405 */ 406 #define list_for_each_entry(pos, head, member) \\ 407 for (pos = list_entry((head)->next, typeof(*pos), member); \\ 408 &pos->member != (head); \\ 409 pos = list_entry(pos->member.next, typeof(*pos), member)) 410 411 /** 412 * list_for_each_entry_reverse - iterate backwards over list of given type. 413 * @pos: the type * to use as a loop cursor. 414 * @head: the head for your list. 415 * @member: the name of the list_struct within the struct. 416 */ 417 #define list_for_each_entry_reverse(pos, head, member) \\ 418 for (pos = list_entry((head)->prev, typeof(*pos), member); \\ 419 &pos->member != (head); \\ 420 pos = list_entry(pos->member.prev, typeof(*pos), member)) 421 422 /** 423 * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue() 424 * @pos: the type * to use as a start point 425 * @head: the head of the list 426 * @member: the name of the list_struct within the struct. 427 * 428 * Prepares a pos entry for use as a start point in list_for_each_entry_continue(). 429 */ 430 #define list_prepare_entry(pos, head, member) \\ 431 ((pos) ? : list_entry(head, typeof(*pos), member)) 432 433 /** 434 * list_for_each_entry_continue - continue iteration over list of given type 435 * @pos: the type * to use as a loop cursor. 436 * @head: the head for your list. 437 * @member: the name of the list_struct within the struct. 438 * 439 * Continue to iterate over list of given type, continuing after 440 * the current position. 441 */ 442 #define list_for_each_entry_continue(pos, head, member) \\ 443 for (pos = list_entry(pos->member.next, typeof(*pos), member); \\ 444 &pos->member != (head); \\ 445 pos = list_entry(pos->member.next, typeof(*pos), member)) 446 447 /** 448 * list_for_each_entry_continue_reverse - iterate backwards from the given point 449 * @pos: the type * to use as a loop cursor. 450 * @head: the head for your list. Linux内核之数据双链表