学习/linux/list.h_双链表实现

linux-3.5/include/linux/list.h

使用只含指针域的双向循环链表进行链表的操作。

下面是我选取部分list.h中代码：

 #ifndef _LINUX_LIST_H
 #define _LINUX_LIST_H

 struct list_head {
     struct list_head *next, *prev;
 };
 /*
  * Simple doubly linked list implementation.
  *
  * Some of the internal functions ("__xxx") are useful when
  * manipulating whole lists rather than single entries, as
  * sometimes we already know the next/prev entries and we can
  * generate better code by using them directly rather than
  * using the generic single-entry routines.
  */

 #define LIST_HEAD_INIT(name) { &(name), &(name) }

 #define LIST_HEAD(name) \
     struct list_head name = LIST_HEAD_INIT(name)

 static inline void INIT_LIST_HEAD(struct list_head *list)
 {
     list->next = list;
     list->prev = list;
 }

 /*
  * Insert a new entry between two known consecutive entries.
  *
  * This is only for internal list manipulation where we know
  * the prev/next entries already!
  */
 #ifndef CONFIG_DEBUG_LIST
 static inline void __list_add(struct list_head *new,
                   struct list_head *prev,
                   struct list_head *next)
 {
     next->prev = new;
     new->next = next;
     new->prev = prev;
     prev->next = new;
 }
 #else
 extern void __list_add(struct list_head *new,
                   struct list_head *prev,
                   struct list_head *next);
 #endif

 /**
  * list_add - add a new entry
  * @new: new entry to be added
  * @head: list head to add it after
  *
  * Insert a new entry after the specified head.
  * This is good for implementing stacks.
  */
 static inline void list_add(struct list_head *new, struct list_head *head)
 {
     __list_add(new, head, head->next);
 }

 /**
  * list_add_tail - add a new entry
  * @new: new entry to be added
  * @head: list head to add it before
  *
  * Insert a new entry before the specified head.
  * This is useful for implementing queues.
  */
 static inline void list_add_tail(struct list_head *new, struct list_head *head)
 {
     __list_add(new, head->prev, head);
 }

 /*
  * Delete a list entry by making the prev/next entries
  * point to each other.
  *
  * This is only for internal list manipulation where we know
  * the prev/next entries already!
  */
 static inline void __list_del(struct list_head * prev, struct list_head * next)
 {
     next->prev = prev;
     prev->next = next;
 }

 /**
  * list_del - deletes entry from list.
  * @entry: the element to delete from the list.
  * Note: list_empty() on entry does not return true after this, the entry is
  * in an undefined state.
  */
 #ifndef CONFIG_DEBUG_LIST
 static inline void __list_del_entry(struct list_head *entry)
 {
     __list_del(entry->prev, entry->next);
 }
 #endif

 /**
  * list_replace - replace old entry by new one
  * @old : the element to be replaced
  * @new : the new element to insert
  *
  * If @old was empty, it will be overwritten.
  */
 static inline void list_replace(struct list_head *old,
                 struct list_head *new)
 {
     new->next = old->next;
     new->next->prev = new;
     new->prev = old->prev;
     new->prev->next = new;
 }

 static inline void list_replace_init(struct list_head *old,
                     struct list_head *new)
 {
     list_replace(old, new);
     INIT_LIST_HEAD(old);
 }

 /**
  * list_del_init - deletes entry from list and reinitialize it.
  * @entry: the element to delete from the list.
  */
 static inline void list_del_init(struct list_head *entry)
 {
     __list_del_entry(entry);
     INIT_LIST_HEAD(entry);
 }

 /**
  * list_move - delete from one list and add as another's head
  * @list: the entry to move
  * @head: the head that will precede our entry
  */
 static inline void list_move(struct list_head *list, struct list_head *head)
 {
     __list_del_entry(list);
     list_add(list, head);
 }

 /**
  * list_move_tail - delete from one list and add as another's tail
  * @list: the entry to move
  * @head: the head that will follow our entry
  */
 static inline void list_move_tail(struct list_head *list,
                   struct list_head *head)
 {
     __list_del_entry(list);
     list_add_tail(list, head);
 }

 /**
  * list_is_last - tests whether @list is the last entry in list @head
  * @list: the entry to test
  * @head: the head of the list
  */
 static inline int list_is_last(const struct list_head *list,
                 const struct list_head *head)
 {
     return list->next == head;
 }

 /**
  * list_empty - tests whether a list is empty
  * @head: the list to test.
  */
 static inline int list_empty(const struct list_head *head)
 {
     return head->next == head;
 }

 /**
  * list_empty_careful - tests whether a list is empty and not being modified
  * @head: the list to test
  *
  * Description:
  * tests whether a list is empty _and_ checks that no other CPU might be
  * in the process of modifying either member (next or prev)
  *
  * NOTE: using list_empty_careful() without synchronization
  * can only be safe if the only activity that can happen
  * to the list entry is list_del_init(). Eg. it cannot be used
  * if another CPU could re-list_add() it.
  */
 static inline int list_empty_careful(const struct list_head *head)
 {
     struct list_head *next = head->next;
     return (next == head) && (next == head->prev);
 }

 /**
  * list_rotate_left - rotate the list to the left
  * @head: the head of the list
  */
 static inline void list_rotate_left(struct list_head *head)
 {
     struct list_head *first;

     if (!list_empty(head)) {
         first = head->next;
         list_move_tail(first, head);
     }
 }

 /**
  * list_is_singular - tests whether a list has just one entry.
  * @head: the list to test.
  */
 static inline int list_is_singular(const struct list_head *head)
 {
     return !list_empty(head) && (head->next == head->prev);
 }

 static inline void __list_cut_position(struct list_head *list,
         struct list_head *head, struct list_head *entry)
 {
     struct list_head *new_first = entry->next;
     list->next = head->next;
     list->next->prev = list;
     list->prev = entry;
     entry->next = list;
     head->next = new_first;
     new_first->prev = head;
 }

 /**
  * list_cut_position - cut a list into two
  * @list: a new list to add all removed entries
  * @head: a list with entries
  * @entry: an entry within head, could be the head itself
  *    and if so we won't cut the list
  *
  * This helper moves the initial part of @head, up to and
  * including @entry, from @head to @list. You should
  * pass on @entry an element you know is on @head. @list
  * should be an empty list or a list you do not care about
  * losing its data.
  *
  */
 static inline void list_cut_position(struct list_head *list,
         struct list_head *head, struct list_head *entry)
 {
     if (list_empty(head))
         return;
     if (list_is_singular(head) &&
         (head->next != entry && head != entry))
         return;
     if (entry == head)
         INIT_LIST_HEAD(list);
     else
         __list_cut_position(list, head, entry);
 }

 static inline void __list_splice(const struct list_head *list,
                  struct list_head *prev,
                  struct list_head *next)
 {
     struct list_head *first = list->next;
     struct list_head *last = list->prev;

     first->prev = prev;
     prev->next = first;

     last->next = next;
     next->prev = last;
 }

 /**
  * list_splice - join two lists, this is designed for stacks
  * @list: the new list to add.
  * @head: the place to add it in the first list.
  */
 static inline void list_splice(const struct list_head *list,
                 struct list_head *head)
 {
     if (!list_empty(list))
         __list_splice(list, head, head->next);
 }

 /**
  * list_splice_tail - join two lists, each list being a queue
  * @list: the new list to add.
  * @head: the place to add it in the first list.
  */
 static inline void list_splice_tail(struct list_head *list,
                 struct list_head *head)
 {
     if (!list_empty(list))
         __list_splice(list, head->prev, head);
 }

 /**
  * list_splice_init - join two lists and reinitialise the emptied list.
  * @list: the new list to add.
  * @head: the place to add it in the first list.
  *
  * The list at @list is reinitialised
  */
 static inline void list_splice_init(struct list_head *list,
                     struct list_head *head)
 {
     if (!list_empty(list)) {
         __list_splice(list, head, head->next);
         INIT_LIST_HEAD(list);
     }
 }

 /**
  * list_splice_tail_init - join two lists and reinitialise the emptied list
  * @list: the new list to add.
  * @head: the place to add it in the first list.
  *
  * Each of the lists is a queue.
  * The list at @list is reinitialised
  */
 static inline void list_splice_tail_init(struct list_head *list,
                      struct list_head *head)
 {
     if (!list_empty(list)) {
         __list_splice(list, head->prev, head);
         INIT_LIST_HEAD(list);
     }
 }

 /**
  * list_entry - get the struct for this entry
  * @ptr:    the &struct list_head pointer.
  * @type:    the type of the struct this is embedded in.
  * @member:    the name of the list_struct within the struct.
  */
 #define list_entry(ptr, type, member) \
     container_of(ptr, type, member)

 /**
  * list_first_entry - get the first element from a list
  * @ptr:    the list head to take the element from.
  * @type:    the type of the struct this is embedded in.
  * @member:    the name of the list_struct within the struct.
  *
  * Note, that list is expected to be not empty.
  */
 #define list_first_entry(ptr, type, member) \
     list_entry((ptr)->next, type, member)

 /**
  * list_for_each    -    iterate over a list
  * @pos:    the &struct list_head to use as a loop cursor.
  * @head:    the head for your list.
  */
 #define list_for_each(pos, head) \
     for (pos = (head)->next; pos != (head); pos = pos->next)

 /**
  * __list_for_each    -    iterate over a list
  * @pos:    the &struct list_head to use as a loop cursor.
  * @head:    the head for your list.
  *
  * This variant doesn't differ from list_for_each() any more.
  * We don't do prefetching in either case.
  */
 #define __list_for_each(pos, head) \
     for (pos = (head)->next; pos != (head); pos = pos->next)

 /**
  * list_for_each_prev    -    iterate over a list backwards
  * @pos:    the &struct list_head to use as a loop cursor.
  * @head:    the head for your list.
  */
 #define list_for_each_prev(pos, head) \
     for (pos = (head)->prev; pos != (head); pos = pos->prev)

 /**
  * list_for_each_safe - iterate over a list safe against removal of list entry
  * @pos:    the &struct list_head to use as a loop cursor.
  * @n:        another &struct list_head to use as temporary storage
  * @head:    the head for your list.
  */
 #define list_for_each_safe(pos, n, head) \
     for (pos = (head)->next, n = pos->next; pos != (head); \
         pos = n, n = pos->next)

 /**
  * list_for_each_prev_safe - iterate over a list backwards safe against removal of list entry
  * @pos:    the &struct list_head to use as a loop cursor.
  * @n:        another &struct list_head to use as temporary storage
  * @head:    the head for your list.
  */
 #define list_for_each_prev_safe(pos, n, head) \
     for (pos = (head)->prev, n = pos->prev; \
          pos != (head); \
          pos = n, n = pos->prev)

 /**
  * list_for_each_entry    -    iterate over list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  */
 #define list_for_each_entry(pos, head, member)                \
     for (pos = list_entry((head)->next, typeof(*pos), member);    \
          &pos->member != (head);     \
          pos = list_entry(pos->member.next, typeof(*pos), member))

 /**
  * list_for_each_entry_reverse - iterate backwards over list of given type.
  * @pos:    the type * to use as a loop cursor.
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  */
 #define list_for_each_entry_reverse(pos, head, member)            \
     for (pos = list_entry((head)->prev, typeof(*pos), member);    \
          &pos->member != (head);     \
          pos = list_entry(pos->member.prev, typeof(*pos), member))

 /**
  * list_prepare_entry - prepare a pos entry for use in list_for_each_entry_continue()
  * @pos:    the type * to use as a start point
  * @head:    the head of the list
  * @member:    the name of the list_struct within the struct.
  *
  * Prepares a pos entry for use as a start point in list_for_each_entry_continue().
  */
 #define list_prepare_entry(pos, head, member) \
     ((pos) ? : list_entry(head, typeof(*pos), member))

 /**
  * list_for_each_entry_continue - continue iteration over list of given type
  * @pos:    the type * to use as a loop cursor.
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  *
  * Continue to iterate over list of given type, continuing after
  * the current position.
  */
 #define list_for_each_entry_continue(pos, head, member)         \
     for (pos = list_entry(pos->member.next, typeof(*pos), member);    \
          &pos->member != (head);    \
          pos = list_entry(pos->member.next, typeof(*pos), member))

 /**
  * list_for_each_entry_continue_reverse - iterate backwards from the given point
  * @pos:    the type * to use as a loop cursor.
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  *
  * Start to iterate over list of given type backwards, continuing after
  * the current position.
  */
 #define list_for_each_entry_continue_reverse(pos, head, member)        \
     for (pos = list_entry(pos->member.prev, typeof(*pos), member);    \
          &pos->member != (head);    \
          pos = list_entry(pos->member.prev, typeof(*pos), member))

 /**
  * list_for_each_entry_from - iterate over list of given type from the current point
  * @pos:    the type * to use as a loop cursor.
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  *
  * Iterate over list of given type, continuing from current position.
  */
 #define list_for_each_entry_from(pos, head, member)             \
     for (; &pos->member != (head);    \
          pos = list_entry(pos->member.next, typeof(*pos), member))

 /**
  * list_for_each_entry_safe - iterate over list of given type safe against removal of list entry
  * @pos:    the type * to use as a loop cursor.
  * @n:        another type * to use as temporary storage
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  */
 #define list_for_each_entry_safe(pos, n, head, member)            \
     for (pos = list_entry((head)->next, typeof(*pos), member),    \
         n = list_entry(pos->member.next, typeof(*pos), member);    \
          &pos->member != (head);                     \
          pos = n, n = list_entry(n->member.next, typeof(*n), member))

 /**
  * list_for_each_entry_safe_continue - continue list iteration safe against removal
  * @pos:    the type * to use as a loop cursor.
  * @n:        another type * to use as temporary storage
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  *
  * Iterate over list of given type, continuing after current point,
  * safe against removal of list entry.
  */
 #define list_for_each_entry_safe_continue(pos, n, head, member)         \
     for (pos = list_entry(pos->member.next, typeof(*pos), member),         \
         n = list_entry(pos->member.next, typeof(*pos), member);        \
          &pos->member != (head);                        \
          pos = n, n = list_entry(n->member.next, typeof(*n), member))

 /**
  * list_for_each_entry_safe_from - iterate over list from current point safe against removal
  * @pos:    the type * to use as a loop cursor.
  * @n:        another type * to use as temporary storage
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  *
  * Iterate over list of given type from current point, safe against
  * removal of list entry.
  */
 #define list_for_each_entry_safe_from(pos, n, head, member)             \
     for (n = list_entry(pos->member.next, typeof(*pos), member);        \
          &pos->member != (head);                        \
          pos = n, n = list_entry(n->member.next, typeof(*n), member))

 /**
  * list_for_each_entry_safe_reverse - iterate backwards over list safe against removal
  * @pos:    the type * to use as a loop cursor.
  * @n:        another type * to use as temporary storage
  * @head:    the head for your list.
  * @member:    the name of the list_struct within the struct.
  *
  * Iterate backwards over list of given type, safe against removal
  * of list entry.
  */
 #define list_for_each_entry_safe_reverse(pos, n, head, member)        \
     for (pos = list_entry((head)->prev, typeof(*pos), member),    \
         n = list_entry(pos->member.prev, typeof(*pos), member);    \
          &pos->member != (head);                     \
          pos = n, n = list_entry(n->member.prev, typeof(*n), member))

 /**
  * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
  * @pos:    the loop cursor used in the list_for_each_entry_safe loop
  * @n:        temporary storage used in list_for_each_entry_safe
  * @member:    the name of the list_struct within the struct.
  *
  * list_safe_reset_next is not safe to use in general if the list may be
  * modified concurrently (eg. the lock is dropped in the loop body). An
  * exception to this is if the cursor element (pos) is pinned in the list,
  * and list_safe_reset_next is called after re-taking the lock and before
  * completing the current iteration of the loop body.
  */
 #define list_safe_reset_next(pos, n, member)                \
     n = list_entry(pos->member.next, typeof(*pos), member)

 /*
  * Double linked lists with a single pointer list head.
  * Mostly useful for hash tables where the two pointer list head is
  * too wasteful.
  * You lose the ability to access the tail in O(1).
  */

 #endif

list.h

测试用例：

 #include "list.h"
 #include <stdio.h>
 #include <stdlib.h>

 #define SZ 32

 #define CNT 66

 struct ourstu {
     char name[SZ];
     int num;
     struct list_head list;
 };
 #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)

 #define container_of(ptr, type, member) ({            \
     const typeof( ((type *))->member ) *__mptr = (ptr);    \
     (type *)( (char *)__mptr - offsetof(type,member) );})

 /*创建双向循环链表*/
 LIST_HEAD(head);

 static int demo_init(void)
 {
     int i;
     struct ourstu *stu;

     struct list_head *pos, *n;

     for (i = ; i < CNT; i++) {
         stu = malloc(sizeof(struct ourstu));
         if (NULL == stu) {
             goto error0;
         }
         stu->num =  + i;
         sprintf(stu->name, "spring%d", i);

         list_add_tail(&stu->list, &head);
     }

     list_for_each (pos, &head) {
         stu = container_of(pos, struct ourstu, list);
         printf("%s's number %d\n", stu->name, stu->num);
     }

     return ;

 error0:
     list_for_each_safe(pos, n, &head) {
         stu = container_of(pos, struct ourstu, list);
         printf("%s see bye...\n", stu->name);
         free(stu);
     }

     return -;
 }

 static void demo_exit(void)
 {
     struct list_head *n, *pos;
     struct ourstu *stu;

     list_for_each_safe(pos, n, &head) {
         stu = container_of(pos, struct ourstu, list);
         printf("%s say bye...\n", stu->name);
         free(stu);
     }

     printf("see you, kernel...\n");
 }

 int main()
 {
     demo_init();
     demo_exit();
 }

先学习到这，以后用到 list.h 中更多的再来补充。