src/basic/list.h

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2 #pragma once
   3
   4 /***
   5   This file is part of systemd.
   6
   7   Copyright 2010 Lennart Poettering
   8 ***/
   9
  10 /* The head of the linked list. Use this in the structure that shall
  11  * contain the head of the linked list */
  12 #define LIST_HEAD(t,name)                                               \
  13         t *name
  14
  15 /* The pointers in the linked list's items. Use this in the item structure */
  16 #define LIST_FIELDS(t,name)                                             \
  17         t *name##_next, *name##_prev
  18
  19 /* Initialize the list's head */
  20 #define LIST_HEAD_INIT(head)                                            \
  21         do {                                                            \
  22                 (head) = NULL; }                                        \
  23         while (false)
  24
  25 /* Initialize a list item */
  26 #define LIST_INIT(name,item)                                            \
  27         do {                                                            \
  28                 typeof(*(item)) *_item = (item);                        \
  29                 assert(_item);                                          \
  30                 _item->name##_prev = _item->name##_next = NULL;         \
  31         } while (false)
  32
  33 /* Prepend an item to the list */
  34 #define LIST_PREPEND(name,head,item)                                    \
  35         do {                                                            \
  36                 typeof(*(head)) **_head = &(head), *_item = (item);     \
  37                 assert(_item);                                          \
  38                 if ((_item->name##_next = *_head))                      \
  39                         _item->name##_next->name##_prev = _item;        \
  40                 _item->name##_prev = NULL;                              \
  41                 *_head = _item;                                         \
  42         } while (false)
  43
  44 /* Append an item to the list */
  45 #define LIST_APPEND(name,head,item)                                     \
  46         do {                                                            \
  47                 typeof(*(head)) *_tail;                                 \
  48                 LIST_FIND_TAIL(name,head,_tail);                        \
  49                 LIST_INSERT_AFTER(name,head,_tail,item);                \
  50         } while (false)
  51
  52 /* Remove an item from the list */
  53 #define LIST_REMOVE(name,head,item)                                     \
  54         do {                                                            \
  55                 typeof(*(head)) **_head = &(head), *_item = (item);     \
  56                 assert(_item);                                          \
  57                 if (_item->name##_next)                                 \
  58                         _item->name##_next->name##_prev = _item->name##_prev; \
  59                 if (_item->name##_prev)                                 \
  60                         _item->name##_prev->name##_next = _item->name##_next; \
  61                 else {                                                  \
  62                         assert(*_head == _item);                        \
  63                         *_head = _item->name##_next;                    \
  64                 }                                                       \
  65                 _item->name##_next = _item->name##_prev = NULL;         \
  66         } while (false)
  67
  68 /* Find the head of the list */
  69 #define LIST_FIND_HEAD(name,item,head)                                  \
  70         do {                                                            \
  71                 typeof(*(item)) *_item = (item);                        \
  72                 if (!_item)                                             \
  73                         (head) = NULL;                                  \
  74                 else {                                                  \
  75                         while (_item->name##_prev)                      \
  76                                 _item = _item->name##_prev;             \
  77                         (head) = _item;                                 \
  78                 }                                                       \
  79         } while (false)
  80
  81 /* Find the tail of the list */
  82 #define LIST_FIND_TAIL(name,item,tail)                                  \
  83         do {                                                            \
  84                 typeof(*(item)) *_item = (item);                        \
  85                 if (!_item)                                             \
  86                         (tail) = NULL;                                  \
  87                 else {                                                  \
  88                         while (_item->name##_next)                      \
  89                                 _item = _item->name##_next;             \
  90                         (tail) = _item;                                 \
  91                 }                                                       \
  92         } while (false)
  93
  94 /* Insert an item after another one (a = where, b = what) */
  95 #define LIST_INSERT_AFTER(name,head,a,b)                                \
  96         do {                                                            \
  97                 typeof(*(head)) **_head = &(head), *_a = (a), *_b = (b); \
  98                 assert(_b);                                             \
  99                 if (!_a) {                                              \
 100                         if ((_b->name##_next = *_head))                 \
 101                                 _b->name##_next->name##_prev = _b;      \
 102                         _b->name##_prev = NULL;                         \
 103                         *_head = _b;                                    \
 104                 } else {                                                \
 105                         if ((_b->name##_next = _a->name##_next))        \
 106                                 _b->name##_next->name##_prev = _b;      \
 107                         _b->name##_prev = _a;                           \
 108                         _a->name##_next = _b;                           \
 109                 }                                                       \
 110         } while (false)
 111
 112 /* Insert an item before another one (a = where, b = what) */
 113 #define LIST_INSERT_BEFORE(name,head,a,b)                               \
 114         do {                                                            \
 115                 typeof(*(head)) **_head = &(head), *_a = (a), *_b = (b); \
 116                 assert(_b);                                             \
 117                 if (!_a) {                                              \
 118                         if (!*_head) {                                  \
 119                                 _b->name##_next = NULL;                 \
 120                                 _b->name##_prev = NULL;                 \
 121                                 *_head = _b;                            \
 122                         } else {                                        \
 123                                 typeof(*(head)) *_tail = (head);        \
 124                                 while (_tail->name##_next)              \
 125                                         _tail = _tail->name##_next;     \
 126                                 _b->name##_next = NULL;                 \
 127                                 _b->name##_prev = _tail;                \
 128                                 _tail->name##_next = _b;                \
 129                         }                                               \
 130                 } else {                                                \
 131                         if ((_b->name##_prev = _a->name##_prev))        \
 132                                 _b->name##_prev->name##_next = _b;      \
 133                         else                                            \
 134                                 *_head = _b;                            \
 135                         _b->name##_next = _a;                           \
 136                         _a->name##_prev = _b;                           \
 137                 }                                                       \
 138         } while (false)
 139
 140 #define LIST_JUST_US(name,item)                                         \
 141         (!(item)->name##_prev && !(item)->name##_next)                  \
 142
 143 #define LIST_FOREACH(name,i,head)                                       \
 144         for ((i) = (head); (i); (i) = (i)->name##_next)
 145
 146 #define LIST_FOREACH_SAFE(name,i,n,head)                                \
 147         for ((i) = (head); (i) && (((n) = (i)->name##_next), 1); (i) = (n))
 148
 149 #define LIST_FOREACH_BEFORE(name,i,p)                                   \
 150         for ((i) = (p)->name##_prev; (i); (i) = (i)->name##_prev)
 151
 152 #define LIST_FOREACH_AFTER(name,i,p)                                    \
 153         for ((i) = (p)->name##_next; (i); (i) = (i)->name##_next)
 154
 155 /* Iterate through all the members of the list p is included in, but skip over p */
 156 #define LIST_FOREACH_OTHERS(name,i,p)                                   \
 157         for (({                                                         \
 158                 (i) = (p);                                              \
 159                 while ((i) && (i)->name##_prev)                         \
 160                         (i) = (i)->name##_prev;                         \
 161                 if ((i) == (p))                                         \
 162                         (i) = (p)->name##_next;                         \
 163              });                                                        \
 164              (i);                                                       \
 165              (i) = (i)->name##_next == (p) ? (p)->name##_next : (i)->name##_next)
 166
 167 /* Loop starting from p->next until p->prev.
 168    p can be adjusted meanwhile. */
 169 #define LIST_LOOP_BUT_ONE(name,i,head,p)                                \
 170         for ((i) = (p)->name##_next ? (p)->name##_next : (head);        \
 171              (i) != (p);                                                \
 172              (i) = (i)->name##_next ? (i)->name##_next : (head))
 173
 174 #define LIST_IS_EMPTY(head)                                             \
 175         (!(head))