| /* |
| * libwebsockets - small server side websockets and web server implementation |
| * |
| * Copyright (C) 2010 - 2019 Andy Green <andy@warmcat.com> |
| * |
| * Permission is hereby granted, free of charge, to any person obtaining a copy |
| * of this software and associated documentation files (the "Software"), to |
| * deal in the Software without restriction, including without limitation the |
| * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or |
| * sell copies of the Software, and to permit persons to whom the Software is |
| * furnished to do so, subject to the following conditions: |
| * |
| * The above copyright notice and this permission notice shall be included in |
| * all copies or substantial portions of the Software. |
| * |
| * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR |
| * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, |
| * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE |
| * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER |
| * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING |
| * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS |
| * IN THE SOFTWARE. |
| */ |
| |
| #include "private-lib-core.h" |
| |
| #ifdef LWS_HAVE_SYS_TYPES_H |
| #include <sys/types.h> |
| #endif |
| |
| void |
| lws_dll_add_head(struct lws_dll *d, struct lws_dll *phead) |
| { |
| if (!lws_dll_is_detached(d, phead)) { |
| assert(0); /* only wholly detached things can be added */ |
| return; |
| } |
| |
| /* our next guy is current first guy, if any */ |
| if (phead->next != d) |
| d->next = phead->next; |
| |
| /* if there is a next guy, set his prev ptr to our next ptr */ |
| if (d->next) |
| d->next->prev = d; |
| /* there is nobody previous to us, we are the head */ |
| d->prev = NULL; |
| |
| /* set the first guy to be us */ |
| phead->next = d; |
| |
| /* if there was nothing on the list before, we are also now the tail */ |
| if (!phead->prev) |
| phead->prev = d; |
| |
| assert(d->prev != d); |
| assert(d->next != d); |
| } |
| |
| void |
| lws_dll_add_tail(struct lws_dll *d, struct lws_dll *phead) |
| { |
| if (!lws_dll_is_detached(d, phead)) { |
| assert(0); /* only wholly detached things can be added */ |
| return; |
| } |
| |
| /* our previous guy is current last guy */ |
| d->prev = phead->prev; |
| /* if there is a prev guy, set his next ptr to our prev ptr */ |
| if (d->prev) |
| d->prev->next = d; |
| /* our next ptr is NULL */ |
| d->next = NULL; |
| /* set the last guy to be us */ |
| phead->prev = d; |
| |
| /* list head is also us if we're the first */ |
| if (!phead->next) |
| phead->next = d; |
| |
| assert(d->prev != d); |
| assert(d->next != d); |
| } |
| |
| void |
| lws_dll_insert(struct lws_dll *n, struct lws_dll *target, |
| struct lws_dll *phead, int before) |
| { |
| if (!lws_dll_is_detached(n, phead)) { |
| assert(0); /* only wholly detached things can be inserted */ |
| return; |
| } |
| if (!target) { |
| /* |
| * the case where there's no target identified degenerates to |
| * a simple add at head or tail |
| */ |
| if (before) { |
| lws_dll_add_head(n, phead); |
| return; |
| } |
| lws_dll_add_tail(n, phead); |
| return; |
| } |
| |
| /* |
| * in the case there's a target "cursor", we have to do the work to |
| * stitch the new guy in appropriately |
| */ |
| |
| if (before) { |
| /* |
| * we go before dd |
| * DDp <-> DD <-> DDn --> DDp <-> us <-> DD <-> DDn |
| */ |
| /* we point forward to dd */ |
| n->next = target; |
| /* we point back to what dd used to point back to */ |
| n->prev = target->prev; |
| /* DDp points forward to us now */ |
| if (target->prev) |
| target->prev->next = n; |
| /* DD points back to us now */ |
| target->prev = n; |
| |
| /* if target was the head, we are now the head */ |
| if (phead->next == target) |
| phead->next = n; |
| |
| /* since we are before another guy, we cannot become the tail */ |
| |
| } else { |
| /* |
| * we go after dd |
| * DDp <-> DD <-> DDn --> DDp <-> DD <-> us <-> DDn |
| */ |
| /* we point forward to what dd used to point forward to */ |
| n->next = target->next; |
| /* we point back to dd */ |
| n->prev = target; |
| /* DDn points back to us */ |
| if (target->next) |
| target->next->prev = n; |
| /* DD points forward to us */ |
| target->next = n; |
| |
| /* if target was the tail, we are now the tail */ |
| if (phead->prev == target) |
| phead->prev = n; |
| |
| /* since we go after another guy, we cannot become the head */ |
| } |
| } |
| |
| /* situation is: |
| * |
| * HEAD: struct lws_dll * = &entry1 |
| * |
| * Entry 1: struct lws_dll .pprev = &HEAD , .next = Entry 2 |
| * Entry 2: struct lws_dll .pprev = &entry1 , .next = &entry2 |
| * Entry 3: struct lws_dll .pprev = &entry2 , .next = NULL |
| * |
| * Delete Entry1: |
| * |
| * - HEAD = &entry2 |
| * - Entry2: .pprev = &HEAD, .next = &entry3 |
| * - Entry3: .pprev = &entry2, .next = NULL |
| * |
| * Delete Entry2: |
| * |
| * - HEAD = &entry1 |
| * - Entry1: .pprev = &HEAD, .next = &entry3 |
| * - Entry3: .pprev = &entry1, .next = NULL |
| * |
| * Delete Entry3: |
| * |
| * - HEAD = &entry1 |
| * - Entry1: .pprev = &HEAD, .next = &entry2 |
| * - Entry2: .pprev = &entry1, .next = NULL |
| * |
| */ |
| |
| void |
| lws_dll_remove(struct lws_dll *d) |
| { |
| if (!d->prev && !d->next) |
| return; |
| |
| /* |
| * remove us |
| * |
| * USp <-> us <-> USn --> USp <-> USn |
| */ |
| |
| /* if we have a next guy, set his prev to our prev */ |
| if (d->next) |
| d->next->prev = d->prev; |
| |
| /* set our prev guy to our next guy instead of us */ |
| if (d->prev) |
| d->prev->next = d->next; |
| |
| /* we're out of the list, we should not point anywhere any more */ |
| d->prev = NULL; |
| d->next = NULL; |
| } |
| |
| void |
| lws_dll_remove_track_tail(struct lws_dll *d, struct lws_dll *phead) |
| { |
| if (lws_dll_is_detached(d, phead)) { |
| assert(phead->prev != d); |
| assert(phead->next != d); |
| return; |
| } |
| |
| /* if we have a next guy, set his prev to our prev */ |
| if (d->next) |
| d->next->prev = d->prev; |
| |
| /* if we have a previous guy, set his next to our next */ |
| if (d->prev) |
| d->prev->next = d->next; |
| |
| if (phead->prev == d) |
| phead->prev = d->prev; |
| |
| if (phead->next == d) |
| phead->next = d->next; |
| |
| /* we're out of the list, we should not point anywhere any more */ |
| d->prev = NULL; |
| d->next = NULL; |
| } |
| |
| |
| int |
| lws_dll_foreach_safe(struct lws_dll *phead, void *user, |
| int (*cb)(struct lws_dll *d, void *user)) |
| { |
| lws_start_foreach_dll_safe(struct lws_dll *, p, tp, phead->next) { |
| if (cb(p, user)) |
| return 1; |
| } lws_end_foreach_dll_safe(p, tp); |
| |
| return 0; |
| } |