如下代码所示，一个头文件实现的双向链表，用c代码实现：

#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H#include "stddef.h"
#include "poison.h"#ifndef ARCH_HAS_PREFETCH
#define ARCH_HAS_PREFETCH
static inline void prefetch(const void *x) {;}
#endif/** 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.*/struct list_head {struct list_head *next, *prev;
};#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!*/
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;
}/*** 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.*/
static inline void list_del(struct list_head *entry)
{__list_del(entry->prev, entry->next);entry->next = LIST_POISON1;entry->prev = LIST_POISON2;
}/*** 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->prev, entry->next);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(list->prev, list->next);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(list->prev, list->next);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_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; prefetch(pos->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 differs from list_for_each() in that it's the* simplest possible list iteration code, no prefetching is done.* Use this for code that knows the list to be very short (empty* or 1 entry) most of the time.*/
#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; prefetch(pos->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; \prefetch(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);	\prefetch(pos->member.next), &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);	\prefetch(pos->member.prev), &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);	\prefetch(pos->member.next), &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);	\prefetch(pos->member.prev), &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 (; prefetch(pos->member.next), &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* @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* @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* @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))/** 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).*/struct hlist_head {struct hlist_node *first;
};struct hlist_node {struct hlist_node *next, **pprev;
};#define HLIST_HEAD_INIT { .first = NULL }
#define HLIST_HEAD(name) struct hlist_head name = {  .first = NULL }
#define INIT_HLIST_HEAD(ptr) ((ptr)->first = NULL)
static inline void INIT_HLIST_NODE(struct hlist_node *h)
{h->next = NULL;h->pprev = NULL;
}static inline int hlist_unhashed(const struct hlist_node *h)
{return !h->pprev;
}static inline int hlist_empty(const struct hlist_head *h)
{return !h->first;
}static inline void __hlist_del(struct hlist_node *n)
{struct hlist_node *next = n->next;struct hlist_node **pprev = n->pprev;*pprev = next;if (next)next->pprev = pprev;
}static inline void hlist_del(struct hlist_node *n)
{__hlist_del(n);n->next = LIST_POISON1;n->pprev = LIST_POISON2;
}static inline void hlist_del_init(struct hlist_node *n)
{if (!hlist_unhashed(n)) {__hlist_del(n);INIT_HLIST_NODE(n);}
}static inline void hlist_add_head(struct hlist_node *n, struct hlist_head *h)
{struct hlist_node *first = h->first;n->next = first;if (first)first->pprev = &n->next;h->first = n;n->pprev = &h->first;
}/* next must be != NULL */
static inline void hlist_add_before(struct hlist_node *n,struct hlist_node *next)
{n->pprev = next->pprev;n->next = next;next->pprev = &n->next;*(n->pprev) = n;
}static inline void hlist_add_after(struct hlist_node *n,struct hlist_node *next)
{next->next = n->next;n->next = next;next->pprev = &n->next;if(next->next)next->next->pprev  = &next->next;
}#define hlist_entry(ptr, type, member) container_of(ptr,type,member)#define hlist_for_each(pos, head) \for (pos = (head)->first; pos && ({ prefetch(pos->next); 1; }); \pos = pos->next)#define hlist_for_each_safe(pos, n, head) \for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \pos = n)/*** hlist_for_each_entry	- iterate over list of given type* @tpos:	the type * to use as a loop cursor.* @pos:	the &struct hlist_node to use as a loop cursor.* @head:	the head for your list.* @member:	the name of the hlist_node within the struct.*/
#define hlist_for_each_entry(tpos, pos, head, member)			 \for (pos = (head)->first;					 \pos && ({ prefetch(pos->next); 1;}) &&			 \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = pos->next)/*** hlist_for_each_entry_continue - iterate over a hlist continuing after current point* @tpos:	the type * to use as a loop cursor.* @pos:	the &struct hlist_node to use as a loop cursor.* @member:	the name of the hlist_node within the struct.*/
#define hlist_for_each_entry_continue(tpos, pos, member)		 \for (pos = (pos)->next;						 \pos && ({ prefetch(pos->next); 1;}) &&			 \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = pos->next)/*** hlist_for_each_entry_from - iterate over a hlist continuing from current point* @tpos:	the type * to use as a loop cursor.* @pos:	the &struct hlist_node to use as a loop cursor.* @member:	the name of the hlist_node within the struct.*/
#define hlist_for_each_entry_from(tpos, pos, member)			 \for (; pos && ({ prefetch(pos->next); 1;}) &&			 \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = pos->next)/*** hlist_for_each_entry_safe - iterate over list of given type safe against removal of list entry* @tpos:	the type * to use as a loop cursor.* @pos:	the &struct hlist_node to use as a loop cursor.* @n:		another &struct hlist_node to use as temporary storage* @head:	the head for your list.* @member:	the name of the hlist_node within the struct.*/
#define hlist_for_each_entry_safe(tpos, pos, n, head, member)		 \for (pos = (head)->first;					 \pos && ({ n = pos->next; 1; }) &&				 \({ tpos = hlist_entry(pos, typeof(*tpos), member); 1;}); \pos = n)#endif