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1 /*
2  * libwebsockets - small server side websockets and web server implementation
3  *
4  * Copyright (C) 2010 - 2019 Andy Green <andy@warmcat.com>
5  *
6  * Permission is hereby granted, free of charge, to any person obtaining a copy
7  * of this software and associated documentation files (the "Software"), to
8  * deal in the Software without restriction, including without limitation the
9  * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
10  * sell copies of the Software, and to permit persons to whom the Software is
11  * furnished to do so, subject to the following conditions:
12  *
13  * The above copyright notice and this permission notice shall be included in
14  * all copies or substantial portions of the 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 THE
19  * 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 /** \defgroup ll linked-lists
26 * ##Linked list apis
27 *
28 * simple single and doubly-linked lists
29 */
30 ///@{
31 
32 /**
33  * lws_start_foreach_ll(): linkedlist iterator helper start
34  *
35  * \param type: type of iteration, eg, struct xyz *
36  * \param it: iterator var name to create
37  * \param start: start of list
38  *
39  * This helper creates an iterator and starts a while (it) {
40  * loop.  The iterator runs through the linked list starting at start and
41  * ends when it gets a NULL.
42  * The while loop should be terminated using lws_start_foreach_ll().
43  */
44 #define lws_start_foreach_ll(type, it, start)\
45 { \
46 	type it = start; \
47 	while (it) {
48 
49 /**
50  * lws_end_foreach_ll(): linkedlist iterator helper end
51  *
52  * \param it: same iterator var name given when starting
53  * \param nxt: member name in the iterator pointing to next list element
54  *
55  * This helper is the partner for lws_start_foreach_ll() that ends the
56  * while loop.
57  */
58 
59 #define lws_end_foreach_ll(it, nxt) \
60 		it = it->nxt; \
61 	} \
62 }
63 
64 /**
65  * lws_start_foreach_ll_safe(): linkedlist iterator helper start safe against delete
66  *
67  * \param type: type of iteration, eg, struct xyz *
68  * \param it: iterator var name to create
69  * \param start: start of list
70  * \param nxt: member name in the iterator pointing to next list element
71  *
72  * This helper creates an iterator and starts a while (it) {
73  * loop.  The iterator runs through the linked list starting at start and
74  * ends when it gets a NULL.
75  * The while loop should be terminated using lws_end_foreach_ll_safe().
76  * Performs storage of next increment for situations where iterator can become invalidated
77  * during iteration.
78  */
79 #define lws_start_foreach_ll_safe(type, it, start, nxt)\
80 { \
81 	type it = start; \
82 	while (it) { \
83 		type next_##it = it->nxt;
84 
85 /**
86  * lws_end_foreach_ll_safe(): linkedlist iterator helper end (pre increment storage)
87  *
88  * \param it: same iterator var name given when starting
89  *
90  * This helper is the partner for lws_start_foreach_ll_safe() that ends the
91  * while loop. It uses the precreated next_ variable already stored during
92  * start.
93  */
94 
95 #define lws_end_foreach_ll_safe(it) \
96 		it = next_##it; \
97 	} \
98 }
99 
100 /**
101  * lws_start_foreach_llp(): linkedlist pointer iterator helper start
102  *
103  * \param type: type of iteration, eg, struct xyz **
104  * \param it: iterator var name to create
105  * \param start: start of list
106  *
107  * This helper creates an iterator and starts a while (it) {
108  * loop.  The iterator runs through the linked list starting at the
109  * address of start and ends when it gets a NULL.
110  * The while loop should be terminated using lws_start_foreach_llp().
111  *
112  * This helper variant iterates using a pointer to the previous linked-list
113  * element.  That allows you to easily delete list members by rewriting the
114  * previous pointer to the element's next pointer.
115  */
116 #define lws_start_foreach_llp(type, it, start)\
117 { \
118 	type it = &(start); \
119 	while (*(it)) {
120 
121 #define lws_start_foreach_llp_safe(type, it, start, nxt)\
122 { \
123 	type it = &(start); \
124 	type next; \
125 	while (*(it)) { \
126 		next = &((*(it))->nxt); \
127 
128 /**
129  * lws_end_foreach_llp(): linkedlist pointer iterator helper end
130  *
131  * \param it: same iterator var name given when starting
132  * \param nxt: member name in the iterator pointing to next list element
133  *
134  * This helper is the partner for lws_start_foreach_llp() that ends the
135  * while loop.
136  */
137 
138 #define lws_end_foreach_llp(it, nxt) \
139 		it = &(*(it))->nxt; \
140 	} \
141 }
142 
143 #define lws_end_foreach_llp_safe(it) \
144 		it = next; \
145 	} \
146 }
147 
148 #define lws_ll_fwd_insert(\
149 	___new_object,	/* pointer to new object */ \
150 	___m_list,	/* member for next list object ptr */ \
151 	___list_head	/* list head */ \
152 		) {\
153 		___new_object->___m_list = ___list_head; \
154 		___list_head = ___new_object; \
155 	}
156 
157 #define lws_ll_fwd_remove(\
158 	___type,	/* type of listed object */ \
159 	___m_list,	/* member for next list object ptr */ \
160 	___target,	/* object to remove from list */ \
161 	___list_head	/* list head */ \
162 	) { \
163                 lws_start_foreach_llp(___type **, ___ppss, ___list_head) { \
164                         if (*___ppss == ___target) { \
165                                 *___ppss = ___target->___m_list; \
166                                 break; \
167                         } \
168                 } lws_end_foreach_llp(___ppss, ___m_list); \
169 	}
170 
171 
172 /*
173  * doubly linked-list
174  */
175 
176 #if defined (LWS_WITH_DEPRECATED_LWS_DLL)
177 
178 /*
179  * This is going away in v4.1.  You can set the cmake option above to keep it
180  * around temporarily.  Migrate your stuff to the more capable and robust
181  * lws_dll2 below
182  */
183 
184 struct lws_dll {
185 	struct lws_dll *prev;
186 	struct lws_dll *next;
187 };
188 
189 /*
190  * these all point to the composed list objects... you have to use the
191  * lws_container_of() helper to recover the start of the containing struct
192  */
193 
194 #define lws_dll_add_front lws_dll_add_head
195 
196 LWS_VISIBLE LWS_EXTERN void
197 lws_dll_add_head(struct lws_dll *d, struct lws_dll *phead);
198 
199 LWS_VISIBLE LWS_EXTERN void
200 lws_dll_add_tail(struct lws_dll *d, struct lws_dll *phead);
201 
202 LWS_VISIBLE LWS_EXTERN void
203 lws_dll_insert(struct lws_dll *d, struct lws_dll *target,
204 	       struct lws_dll *phead, int before);
205 
206 static LWS_INLINE struct lws_dll *
lws_dll_get_head(struct lws_dll * phead)207 lws_dll_get_head(struct lws_dll *phead) { return phead->next; }
208 
209 static LWS_INLINE struct lws_dll *
lws_dll_get_tail(struct lws_dll * phead)210 lws_dll_get_tail(struct lws_dll *phead) { return phead->prev; }
211 
212 /*
213  * caution, this doesn't track the tail in the head struct.  Use
214  * lws_dll_remove_track_tail() instead of this if you want tail tracking.  Using
215  * this means you can't use lws_dll_add_tail() amd
216  */
217 LWS_VISIBLE LWS_EXTERN void
218 lws_dll_remove(struct lws_dll *d) LWS_WARN_DEPRECATED;
219 
220 LWS_VISIBLE LWS_EXTERN void
221 lws_dll_remove_track_tail(struct lws_dll *d, struct lws_dll *phead);
222 
223 /* another way to do lws_start_foreach_dll_safe() on a list via a cb */
224 
225 LWS_VISIBLE LWS_EXTERN int
226 lws_dll_foreach_safe(struct lws_dll *phead, void *user,
227 		     int (*cb)(struct lws_dll *d, void *user));
228 
229 #define lws_dll_is_detached(___dll, __head) \
230 	(!(___dll)->prev && !(___dll)->next && (__head)->prev != (___dll))
231 
232 #endif
233 
234 /*
235  * lws_dll2_owner / lws_dll2 : more capable version of lws_dll.  Differences:
236  *
237  *  - there's an explicit lws_dll2_owner struct which holds head, tail and
238  *    count of members.
239  *
240  *  - list members all hold a pointer to their owner.  So user code does not
241  *    have to track anything about exactly what lws_dll2_owner list the object
242  *    is a member of.
243  *
244  *  - you can use lws_dll unless you want the member count or the ability to
245  *    not track exactly which list it's on.
246  *
247  *  - layout is compatible with lws_dll (but lws_dll apis will not update the
248  *    new stuff)
249  */
250 
251 
252 struct lws_dll2;
253 struct lws_dll2_owner;
254 
255 typedef struct lws_dll2 {
256 	struct lws_dll2		*prev;
257 	struct lws_dll2		*next;
258 	struct lws_dll2_owner	*owner;
259 } lws_dll2_t;
260 
261 typedef struct lws_dll2_owner {
262 	struct lws_dll2		*tail;
263 	struct lws_dll2		*head;
264 
265 	uint32_t		count;
266 } lws_dll2_owner_t;
267 
268 static LWS_INLINE int
lws_dll2_is_detached(const struct lws_dll2 * d)269 lws_dll2_is_detached(const struct lws_dll2 *d) { return !d->owner; }
270 
271 static LWS_INLINE const struct lws_dll2_owner *
lws_dll2_owner(const struct lws_dll2 * d)272 lws_dll2_owner(const struct lws_dll2 *d) { return d->owner; }
273 
274 static LWS_INLINE struct lws_dll2 *
lws_dll2_get_head(struct lws_dll2_owner * owner)275 lws_dll2_get_head(struct lws_dll2_owner *owner) { return owner->head; }
276 
277 static LWS_INLINE struct lws_dll2 *
lws_dll2_get_tail(struct lws_dll2_owner * owner)278 lws_dll2_get_tail(struct lws_dll2_owner *owner) { return owner->tail; }
279 
280 LWS_VISIBLE LWS_EXTERN void
281 lws_dll2_add_head(struct lws_dll2 *d, struct lws_dll2_owner *owner);
282 
283 LWS_VISIBLE LWS_EXTERN void
284 lws_dll2_add_tail(struct lws_dll2 *d, struct lws_dll2_owner *owner);
285 
286 LWS_VISIBLE LWS_EXTERN void
287 lws_dll2_remove(struct lws_dll2 *d);
288 
289 LWS_VISIBLE LWS_EXTERN int
290 lws_dll2_foreach_safe(struct lws_dll2_owner *owner, void *user,
291 		      int (*cb)(struct lws_dll2 *d, void *user));
292 
293 LWS_VISIBLE LWS_EXTERN void
294 lws_dll2_clear(struct lws_dll2 *d);
295 
296 LWS_VISIBLE LWS_EXTERN void
297 lws_dll2_owner_clear(struct lws_dll2_owner *d);
298 
299 LWS_VISIBLE LWS_EXTERN void
300 lws_dll2_add_before(struct lws_dll2 *d, struct lws_dll2 *after);
301 
302 LWS_VISIBLE LWS_EXTERN void
303 lws_dll2_add_sorted(lws_dll2_t *d, lws_dll2_owner_t *own,
304 		    int (*compare)(const lws_dll2_t *d, const lws_dll2_t *i));
305 
306 #if defined(_DEBUG)
307 void
308 lws_dll2_describe(struct lws_dll2_owner *owner, const char *desc);
309 #else
310 #define lws_dll2_describe(x, y)
311 #endif
312 
313 /*
314  * these are safe against the current container object getting deleted,
315  * since the hold his next in a temp and go to that next.  ___tmp is
316  * the temp.
317  */
318 
319 #define lws_start_foreach_dll_safe(___type, ___it, ___tmp, ___start) \
320 { \
321 	___type ___it = ___start; \
322 	while (___it) { \
323 		___type ___tmp = (___it)->next;
324 
325 #define lws_end_foreach_dll_safe(___it, ___tmp) \
326 		___it = ___tmp; \
327 	} \
328 }
329 
330 #define lws_start_foreach_dll(___type, ___it, ___start) \
331 { \
332 	___type ___it = ___start; \
333 	while (___it) {
334 
335 #define lws_end_foreach_dll(___it) \
336 		___it = (___it)->next; \
337 	} \
338 }
339 
340 ///@}
341 
342