1/*
2 * Copyright © 2010 Intel Corporation
3 * Copyright © 2010 Francisco Jerez <currojerez@riseup.net>
4 *
5 * Permission is hereby granted, free of charge, to any person obtaining a
6 * copy of this software and associated documentation files (the "Software"),
7 * to deal in the Software without restriction, including without limitation
8 * the rights to use, copy, modify, merge, publish, distribute, sublicense,
9 * and/or sell copies of the Software, and to permit persons to whom the
10 * Software is furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice (including the next
13 * paragraph) shall be included in all copies or substantial portions of the
14 * Software.
15 *
16 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
17 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
18 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
19 * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
20 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
21 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
22 * IN THE SOFTWARE.
23 *
24 */
25
26#ifndef _XORG_LIST_H_
27#define _XORG_LIST_H_
28
29#include <stddef.h> /* offsetof() */
30
31/**
32 * @file Classic doubly-link circular list implementation.
33 * For real usage examples of the linked list, see the file test/list.c
34 *
35 * Example:
36 * We need to keep a list of struct foo in the parent struct bar, i.e. what
37 * we want is something like this.
38 *
39 *     struct bar {
40 *          ...
41 *          struct foo *list_of_foos; -----> struct foo {}, struct foo {}, struct foo{}
42 *          ...
43 *     }
44 *
45 * We need one list head in bar and a list element in all list_of_foos (both are of
46 * data type 'struct xorg_list').
47 *
48 *     struct bar {
49 *          ...
50 *          struct xorg_list list_of_foos;
51 *          ...
52 *     }
53 *
54 *     struct foo {
55 *          ...
56 *          struct xorg_list entry;
57 *          ...
58 *     }
59 *
60 * Now we initialize the list head:
61 *
62 *     struct bar bar;
63 *     ...
64 *     xorg_list_init(&bar.list_of_foos);
65 *
66 * Then we create the first element and add it to this list:
67 *
68 *     struct foo *foo = malloc(...);
69 *     ....
70 *     xorg_list_add(&foo->entry, &bar.list_of_foos);
71 *
72 * Repeat the above for each element you want to add to the list. Deleting
73 * works with the element itself.
74 *      xorg_list_del(&foo->entry);
75 *      free(foo);
76 *
77 * Note: calling xorg_list_del(&bar.list_of_foos) will set bar.list_of_foos to an empty
78 * list again.
79 *
80 * Looping through the list requires a 'struct foo' as iterator and the
81 * name of the field the subnodes use.
82 *
83 * struct foo *iterator;
84 * xorg_list_for_each_entry(iterator, &bar.list_of_foos, entry) {
85 *      if (iterator->something == ...)
86 *             ...
87 * }
88 *
89 * Note: You must not call xorg_list_del() on the iterator if you continue the
90 * loop. You need to run the safe for-each loop instead:
91 *
92 * struct foo *iterator, *next;
93 * xorg_list_for_each_entry_safe(iterator, next, &bar.list_of_foos, entry) {
94 *      if (...)
95 *              xorg_list_del(&iterator->entry);
96 * }
97 *
98 */
99
100/**
101 * The linkage struct for list nodes. This struct must be part of your
102 * to-be-linked struct. struct xorg_list is required for both the head of the
103 * list and for each list node.
104 *
105 * Position and name of the struct xorg_list field is irrelevant.
106 * There are no requirements that elements of a list are of the same type.
107 * There are no requirements for a list head, any struct xorg_list can be a list
108 * head.
109 */
110struct xorg_list {
111    struct xorg_list *next, *prev;
112};
113
114/**
115 * Initialize the list as an empty list.
116 *
117 * Example:
118 * xorg_list_init(&bar->list_of_foos);
119 *
120 * @param list The list to initialize
121 */
122static inline void
123xorg_list_init(struct xorg_list *list)
124{
125    list->next = list->prev = list;
126}
127
128static inline void
129__xorg_list_add(struct xorg_list *entry,
130                struct xorg_list *prev, struct xorg_list *next)
131{
132    next->prev = entry;
133    entry->next = next;
134    entry->prev = prev;
135    prev->next = entry;
136}
137
138/**
139 * Insert a new element after the given list head. The new element does not
140 * need to be initialised as empty list.
141 * The list changes from:
142 *      head → some element → ...
143 * to
144 *      head → new element → older element → ...
145 *
146 * Example:
147 * struct foo *newfoo = malloc(...);
148 * xorg_list_add(&newfoo->entry, &bar->list_of_foos);
149 *
150 * @param entry The new element to prepend to the list.
151 * @param head The existing list.
152 */
153static inline void
154xorg_list_add(struct xorg_list *entry, struct xorg_list *head)
155{
156    __xorg_list_add(entry, head, head->next);
157}
158
159/**
160 * Append a new element to the end of the list given with this list head.
161 *
162 * The list changes from:
163 *      head → some element → ... → lastelement
164 * to
165 *      head → some element → ... → lastelement → new element
166 *
167 * Example:
168 * struct foo *newfoo = malloc(...);
169 * xorg_list_append(&newfoo->entry, &bar->list_of_foos);
170 *
171 * @param entry The new element to prepend to the list.
172 * @param head The existing list.
173 */
174static inline void
175xorg_list_append(struct xorg_list *entry, struct xorg_list *head)
176{
177    __xorg_list_add(entry, head->prev, head);
178}
179
180static inline void
181__xorg_list_del(struct xorg_list *prev, struct xorg_list *next)
182{
183    next->prev = prev;
184    prev->next = next;
185}
186
187/**
188 * Remove the element from the list it is in. Using this function will reset
189 * the pointers to/from this element so it is removed from the list. It does
190 * NOT free the element itself or manipulate it otherwise.
191 *
192 * Using xorg_list_del on a pure list head (like in the example at the top of
193 * this file) will NOT remove the first element from
194 * the list but rather reset the list as empty list.
195 *
196 * Example:
197 * xorg_list_del(&foo->entry);
198 *
199 * @param entry The element to remove.
200 */
201static inline void
202xorg_list_del(struct xorg_list *entry)
203{
204    __xorg_list_del(entry->prev, entry->next);
205    xorg_list_init(entry);
206}
207
208/**
209 * Check if the list is empty.
210 *
211 * Example:
212 * xorg_list_is_empty(&bar->list_of_foos);
213 *
214 * @return True if the list is empty or False if the list contains one or more
215 * elements.
216 */
217static inline int
218xorg_list_is_empty(struct xorg_list *head)
219{
220    return head->next == head;
221}
222
223/**
224 * Returns a pointer to the container of this list element.
225 *
226 * Example:
227 * struct foo* f;
228 * f = container_of(&foo->entry, struct foo, entry);
229 * assert(f == foo);
230 *
231 * @param ptr Pointer to the struct xorg_list.
232 * @param type Data type of the list element.
233 * @param member Member name of the struct xorg_list field in the list element.
234 * @return A pointer to the data struct containing the list head.
235 */
236#ifndef container_of
237#define container_of(ptr, type, member) \
238    (type *)((char *)(ptr) - offsetof(type, member))
239#endif
240
241/**
242 * Alias of container_of
243 */
244#define xorg_list_entry(ptr, type, member) \
245    container_of(ptr, type, member)
246
247/**
248 * Retrieve the first list entry for the given list pointer.
249 *
250 * Example:
251 * struct foo *first;
252 * first = xorg_list_first_entry(&bar->list_of_foos, struct foo, list_of_foos);
253 *
254 * @param ptr The list head
255 * @param type Data type of the list element to retrieve
256 * @param member Member name of the struct xorg_list field in the list element.
257 * @return A pointer to the first list element.
258 */
259#define xorg_list_first_entry(ptr, type, member) \
260    xorg_list_entry((ptr)->next, type, member)
261
262/**
263 * Retrieve the last list entry for the given listpointer.
264 *
265 * Example:
266 * struct foo *first;
267 * first = xorg_list_last_entry(&bar->list_of_foos, struct foo, list_of_foos);
268 *
269 * @param ptr The list head
270 * @param type Data type of the list element to retrieve
271 * @param member Member name of the struct xorg_list field in the list element.
272 * @return A pointer to the last list element.
273 */
274#define xorg_list_last_entry(ptr, type, member) \
275    xorg_list_entry((ptr)->prev, type, member)
276
277#ifdef HAVE_TYPEOF
278#define __container_of(ptr, sample, member)			\
279    container_of(ptr, typeof(*sample), member)
280#else
281/* This implementation of __container_of has undefined behavior according
282 * to the C standard, but it works in many cases.  If your compiler doesn't
283 * support typeof() and fails with this implementation, please try a newer
284 * compiler.
285 */
286#define __container_of(ptr, sample, member)                            \
287    (void *)((char *)(ptr)                                             \
288            - ((char *)&(sample)->member - (char *)(sample)))
289#endif
290
291/**
292 * Loop through the list given by head and set pos to struct in the list.
293 *
294 * Example:
295 * struct foo *iterator;
296 * xorg_list_for_each_entry(iterator, &bar->list_of_foos, entry) {
297 *      [modify iterator]
298 * }
299 *
300 * This macro is not safe for node deletion. Use xorg_list_for_each_entry_safe
301 * instead.
302 *
303 * @param pos Iterator variable of the type of the list elements.
304 * @param head List head
305 * @param member Member name of the struct xorg_list in the list elements.
306 *
307 */
308#define xorg_list_for_each_entry(pos, head, member)			\
309    for (pos = NULL,                                                    \
310         pos = __container_of((head)->next, pos, member);		\
311	 &pos->member != (head);					\
312	 pos = __container_of(pos->member.next, pos, member))
313
314/**
315 * Loop through the list, keeping a backup pointer to the element. This
316 * macro allows for the deletion of a list element while looping through the
317 * list.
318 *
319 * See xorg_list_for_each_entry for more details.
320 */
321#define xorg_list_for_each_entry_safe(pos, tmp, head, member)		\
322    for (pos = NULL,                                                    \
323         pos = __container_of((head)->next, pos, member),		\
324	 tmp = __container_of(pos->member.next, pos, member);		\
325	 &pos->member != (head);					\
326	 pos = tmp, tmp = __container_of(pos->member.next, tmp, member))
327
328/* NULL-Terminated List Interface
329 *
330 * The interface below does _not_ use the struct xorg_list as described above.
331 * It is mainly for legacy structures that cannot easily be switched to
332 * struct xorg_list.
333 *
334 * This interface is for structs like
335 *      struct foo {
336 *          [...]
337 *          struct foo *next;
338 *           [...]
339 *      };
340 *
341 * The position and field name of "next" are arbitrary.
342 */
343
344/**
345 * Init the element as null-terminated list.
346 *
347 * Example:
348 * struct foo *list = malloc();
349 * nt_list_init(list, next);
350 *
351 * @param list The list element that will be the start of the list
352 * @param member Member name of the field pointing to next struct
353 */
354#define nt_list_init(_list, _member) \
355	(_list)->_member = NULL
356
357/**
358 * Returns the next element in the list or NULL on termination.
359 *
360 * Example:
361 * struct foo *element = list;
362 * while ((element = nt_list_next(element, next)) { }
363 *
364 * This macro is not safe for node deletion. Use nt_list_for_each_entry_safe
365 * instead.
366 *
367 * @param list The list or current element.
368 * @param member Member name of the field pointing to next struct.
369 */
370#define nt_list_next(_list, _member) \
371	(_list)->_member
372
373/**
374 * Iterate through each element in the list.
375 *
376 * Example:
377 * struct foo *iterator;
378 * nt_list_for_each_entry(iterator, list, next) {
379 *      [modify iterator]
380 * }
381 *
382 * @param entry Assigned to the current list element
383 * @param list The list to iterate through.
384 * @param member Member name of the field pointing to next struct.
385 */
386#define nt_list_for_each_entry(_entry, _list, _member)			\
387	for (_entry = _list; _entry; _entry = (_entry)->_member)
388
389/**
390 * Iterate through each element in the list, keeping a backup pointer to the
391 * element. This macro allows for the deletion of a list element while
392 * looping through the list.
393 *
394 * See nt_list_for_each_entry for more details.
395 *
396 * @param entry Assigned to the current list element
397 * @param tmp The pointer to the next element
398 * @param list The list to iterate through.
399 * @param member Member name of the field pointing to next struct.
400 */
401#define nt_list_for_each_entry_safe(_entry, _tmp, _list, _member)	\
402	for (_entry = _list, _tmp = (_entry) ? (_entry)->_member : NULL;\
403		_entry;							\
404		_entry = _tmp, _tmp = (_tmp) ? (_tmp)->_member: NULL)
405
406/**
407 * Append the element to the end of the list. This macro may be used to
408 * merge two lists.
409 *
410 * Example:
411 * struct foo *elem = malloc(...);
412 * nt_list_init(elem, next)
413 * nt_list_append(elem, list, struct foo, next);
414 *
415 * Resulting list order:
416 * list_item_0 -> list_item_1 -> ... -> elem_item_0 -> elem_item_1 ...
417 *
418 * @param entry An entry (or list) to append to the list
419 * @param list The list to append to. This list must be a valid list, not
420 * NULL.
421 * @param type The list type
422 * @param member Member name of the field pointing to next struct
423 */
424#define nt_list_append(_entry, _list, _type, _member)		        \
425    do {								\
426	_type *__iterator = _list;					\
427	while (__iterator->_member) { __iterator = __iterator->_member;}\
428	__iterator->_member = _entry;					\
429    } while (0)
430
431/**
432 * Insert the element at the next position in the list. This macro may be
433 * used to insert a list into a list.
434 *
435 * struct foo *elem = malloc(...);
436 * nt_list_init(elem, next)
437 * nt_list_insert(elem, list, struct foo, next);
438 *
439 * Resulting list order:
440 * list_item_0 -> elem_item_0 -> elem_item_1 ... -> list_item_1 -> ...
441 *
442 * @param entry An entry (or list) to append to the list
443 * @param list The list to insert to. This list must be a valid list, not
444 * NULL.
445 * @param type The list type
446 * @param member Member name of the field pointing to next struct
447 */
448#define nt_list_insert(_entry, _list, _type, _member)			\
449    do {								\
450	nt_list_append((_list)->_member, _entry, _type, _member);	\
451	(_list)->_member = _entry;					\
452    } while (0)
453
454/**
455 * Delete the entry from the list by iterating through the list and
456 * removing any reference from the list to the entry.
457 *
458 * Example:
459 * struct foo *elem = <assign to right element>
460 * nt_list_del(elem, list, struct foo, next);
461 *
462 * @param entry The entry to delete from the list. entry is always
463 * re-initialized as a null-terminated list.
464 * @param list The list containing the entry, set to the new list without
465 * the removed entry.
466 * @param type The list type
467 * @param member Member name of the field pointing to the next entry
468 */
469#define nt_list_del(_entry, _list, _type, _member)		\
470	do {							\
471		_type *__e = _entry;				\
472		if (__e == NULL || _list == NULL) break;        \
473		if ((_list) == __e) {				\
474		    _list = __e->_member;			\
475		} else {					\
476		    _type *__prev = _list;			\
477		    while (__prev->_member && __prev->_member != __e)	\
478			__prev = nt_list_next(__prev, _member);	\
479		    if (__prev->_member)			\
480			__prev->_member = __e->_member;		\
481		}						\
482		nt_list_init(__e, _member);			\
483	} while(0)
484
485/**
486 * DO NOT USE THIS.
487 * This is a remainder of the xfree86 DDX attempt of having a set of generic
488 * list functions. Unfortunately, the xf86OptionRec uses it and we can't
489 * easily get rid of it. Do not use for new code.
490 */
491typedef struct generic_list_rec {
492    void *next;
493} GenericListRec, *GenericListPtr, *glp;
494
495#endif
496