include/linux/list.h

   1 #ifndef _LINUX_LIST_H
   2 #define _LINUX_LIST_H
   3
   4 #ifdef __KERNEL__
   5
   6 /*
   7  * Simple doubly linked list implementation.
   8  *
   9  * Some of the internal functions ("__xxx") are useful when
  10  * manipulating whole lists rather than single entries, as
  11  * sometimes we already know the next/prev entries and we can
  12  * generate better code by using them directly rather than
  13  * using the generic single-entry routines.
  14  */
  15
  16 struct list_head {
  17         struct list_head *next, *prev;
  18 };
  19
  20 #define LIST_HEAD_INIT(name) { &(name), &(name) }
  21
  22 #define LIST_HEAD(name) \
  23         struct list_head name = LIST_HEAD_INIT(name)
  24
  25 #define INIT_LIST_HEAD(ptr) do { \
  26         (ptr)->next = (ptr); (ptr)->prev = (ptr); \
  27 } while (0)
  28
  29 /*
  30  * Insert a new entry between two known consecutive entries.
  31  *
  32  * This is only for internal list manipulation where we know
  33  * the prev/next entries already!
  34  */
  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
  45 /**
  46  * list_add - add a new entry
  47  * @new: new entry to be added
  48  * @head: list head to add it after
  49  *
  50  * Insert a new entry after the specified head.
  51  * This is good for implementing stacks.
  52  */
  53 static __inline__ void list_add(struct list_head *new, struct list_head *head)
  54 {
  55         __list_add(new, head, head->next);
  56 }
  57
  58 /**
  59  * list_add_tail - add a new entry
  60  * @new: new entry to be added
  61  * @head: list head to add it before
  62  *
  63  * Insert a new entry before the specified head.
  64  * This is useful for implementing queues.
  65  */
  66 static __inline__ void list_add_tail(struct list_head *new, struct list_head *head)
  67 {
  68         __list_add(new, head->prev, head);
  69 }
  70
  71 /*
  72  * Delete a list entry by making the prev/next entries
  73  * point to each other.
  74  *
  75  * This is only for internal list manipulation where we know
  76  * the prev/next entries already!
  77  */
  78 static __inline__ void __list_del(struct list_head * prev,
  79                                   struct list_head * next)
  80 {
  81         next->prev = prev;
  82         prev->next = next;
  83 }
  84
  85 /**
  86  * list_del - deletes entry from list.
  87  * @entry: the element to delete from the list.
  88  * Note: list_empty on entry does not return true after this, the entry is in an undefined state.
  89  */
  90 static __inline__ void list_del(struct list_head *entry)
  91 {
  92         __list_del(entry->prev, entry->next);
  93 }
  94
  95 /**
  96  * list_del_init - deletes entry from list and reinitialize it.
  97  * @entry: the element to delete from the list.
  98  */
  99 static __inline__ void list_del_init(struct list_head *entry)
 100 {
 101         __list_del(entry->prev, entry->next);
 102         INIT_LIST_HEAD(entry);
 103 }
 104
 105 /**
 106  * list_empty - tests whether a list is empty
 107  * @head: the list to test.
 108  */
 109 static __inline__ int list_empty(struct list_head *head)
 110 {
 111         return head->next == head;
 112 }
 113
 114 /**
 115  * list_splice - join two lists
 116  * @list: the new list to add.
 117  * @head: the place to add it in the first list.
 118  */
 119 static __inline__ void list_splice(struct list_head *list, struct list_head *head)
 120 {
 121         struct list_head *first = list->next;
 122
 123         if (first != list) {
 124                 struct list_head *last = list->prev;
 125                 struct list_head *at = head->next;
 126
 127                 first->prev = head;
 128                 head->next = first;
 129
 130                 last->next = at;
 131                 at->prev = last;
 132         }
 133 }
 134
 135 /**
 136  * list_entry - get the struct for this entry
 137  * @ptr:        the &struct list_head pointer.
 138  * @type:       the type of the struct this is embedded in.
 139  * @member:     the name of the list_struct within the struct.
 140  */
 141 #define list_entry(ptr, type, member) \
 142         ((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
 143
 144 /**
 145  * list_for_each        -       iterate over a list
 146  * @pos:        the &struct list_head to use as a loop counter.
 147  * @head:       the head for your list.
 148  */
 149 #define list_for_each(pos, head) \
 150         for (pos = (head)->next; pos != (head); pos = pos->next)
 151
 152 #endif /* __KERNEL__ */
 153
 154 #endif