一、背景

list.h文件位于linux/include下，內核中鏈表的操作函數都在其中。它有許多關于鏈表的操作函數，所以我們可以嘗試將list.h拉到用戶態(tài)中來使用，這樣，我們在用戶態(tài)中若要用到鏈表就可以直接調用其中已經實現好的函數了。我這里將拉到用戶態(tài)的經過“改造”后的list.h文件代碼列出，然后舉一個簡單的例子來應用這個頭文件。當然，list.h中的函數非常多，應用也應該很廣泛，我這里只是簡單的示例其中較簡單的幾個函數。

二、用戶態(tài)下的list.h

/** @file list.h* @author PF* @date 2017/05/1** port from linux kernel list.h: https://github.com/torvalds/linux/raw/master/include/linux/list.h** Here is a recipe to cook list.h for user space program.* 1. copy list.h from linux/include/list.h* 2. remove* - #ifdef __KERNE__ and its #endif* - all #include line* - prefetch() and rcu related functions* 3. add macro offsetof() and container_of*/#ifndef LIST_H_ #define LIST_H_ (1)// import from include/linux/types.h struct list_head {struct list_head *next, *prev; };struct hlist_head {struct hlist_node *first; };struct hlist_node {struct hlist_node *next, **pprev; };// import from include/linux/poison.h/** Architectures might want to move the poison pointer offset* into some well-recognized area such as 0xdead000000000000,* that is also not mappable by user-space exploits:*/ #ifdef CONFIG_ILLEGAL_POINTER_VALUE # define POISON_POINTER_DELTA _AC(CONFIG_ILLEGAL_POINTER_VALUE, UL) #else # define POISON_POINTER_DELTA (0) #endif/** These are non-NULL pointers that will result in page faults* under normal circumstances, used to verify that nobody uses* non-initialized list entries.*/ #define LIST_POISON1 ((void *) 0x00100100 + POISON_POINTER_DELTA) #define LIST_POISON2 ((void *) 0x00200200 + POISON_POINTER_DELTA)// import from include/linux/stddef.h #undef offsetof #ifdef __compiler_offsetof #define offsetof(TYPE,MEMBER) __compiler_offsetof(TYPE,MEMBER) #else #define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER) #endif// import from include/linux/kernel.h /** * container_of - cast a member of a structure out to the containing structure * @ptr: the pointer to the member. * @type: the type of the container struct this is embedded in. * @member: the name of the member within the struct. * */ #define container_of(ptr, type, member) ({ \const typeof( ((type *)0)->member ) *__mptr = (ptr); \(type *)( (char *)__mptr - offsetof(type,member) );})/** 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_LISTstatic inline void __list_del_entry(struct list_head *entry) {__list_del(entry->prev, entry->next); }static inline void list_del(struct list_head *entry) {__list_del(entry->prev, entry->next);entry->next = LIST_POISON1;entry->prev = LIST_POISON2; }#else extern void __list_del_entry(struct list_head *entry); extern void list_del(struct list_head *entry); #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_head 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_head 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_last_entry - get the last 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_head within the struct.** Note, that list is expected to be not empty.*/ #define list_last_entry(ptr, type, member) \list_entry((ptr)->prev, type, member)/*** list_first_entry_or_null - 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_head within the struct.** Note that if the list is empty, it returns NULL.*/ #define list_first_entry_or_null(ptr, type, member) \(!list_empty(ptr) ? list_first_entry(ptr, type, member) : NULL)/*** list_next_entry - get the next element in list* @pos: the type * to cursor* @member: the name of the list_head within the struct.*/ #define list_next_entry(pos, member) \list_entry((pos)->member.next, typeof(*(pos)), member)/*** list_prev_entry - get the prev element in list* @pos: the type * to cursor* @member: the name of the list_head within the struct.*/ #define list_prev_entry(pos, member) \list_entry((pos)->member.prev, typeof(*(pos)), 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_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_head within the struct.*/ #define list_for_each_entry(pos, head, member) \for (pos = list_first_entry(head, typeof(*pos), member); \&pos->member != (head); \pos = list_next_entry(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_head within the struct.*/ #define list_for_each_entry_reverse(pos, head, member) \for (pos = list_last_entry(head, typeof(*pos), member); \&pos->member != (head); \pos = list_prev_entry(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_head 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_head 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_next_entry(pos, member); \&pos->member != (head); \pos = list_next_entry(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_head 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_prev_entry(pos, member); \&pos->member != (head); \pos = list_prev_entry(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_head 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_next_entry(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_head within the struct.*/ #define list_for_each_entry_safe(pos, n, head, member) \for (pos = list_first_entry(head, typeof(*pos), member), \n = list_next_entry(pos, member); \&pos->member != (head); \pos = n, n = list_next_entry(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_head 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_next_entry(pos, member), \n = list_next_entry(pos, member); \&pos->member != (head); \pos = n, n = list_next_entry(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_head 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_next_entry(pos, member); \&pos->member != (head); \pos = n, n = list_next_entry(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_head 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_last_entry(head, typeof(*pos), member), \n = list_prev_entry(pos, member); \&pos->member != (head); \pos = n, n = list_prev_entry(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_head 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_next_entry(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).*/#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_behind(struct hlist_node *n,struct hlist_node *prev) {n->next = prev->next;prev->next = n;n->pprev = &prev->next;if (n->next) {n->next->pprev = &n->next;} }/* after that we'll appear to be on some hlist and hlist_del will work */ static inline void hlist_add_fake(struct hlist_node *n) {n->pprev = &n->next; }/** Move a list from one list head to another. Fixup the pprev* reference of the first entry if it exists.*/ static inline void hlist_move_list(struct hlist_head *old,struct hlist_head *new) {new->first = old->first;if (new->first) {new->first->pprev = &new->first;}old->first = NULL; }#define hlist_entry(ptr, type, member) container_of(ptr,type,member)#define hlist_for_each(pos, head) \for (pos = (head)->first; pos ; pos = pos->next)#define hlist_for_each_safe(pos, n, head) \for (pos = (head)->first; pos && ({ n = pos->next; 1; }); \pos = n)#define hlist_entry_safe(ptr, type, member) \({ typeof(ptr) ____ptr = (ptr); \____ptr ? hlist_entry(____ptr, type, member) : NULL; \})/*** hlist_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 hlist_node within the struct.*/ #define hlist_for_each_entry(pos, head, member) \for (pos = hlist_entry_safe((head)->first, typeof(*(pos)), member);\pos; \pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))/*** hlist_for_each_entry_continue - iterate over a hlist continuing after current point* @pos: the type * to use as a loop cursor.* @member: the name of the hlist_node within the struct.*/ #define hlist_for_each_entry_continue(pos, member) \for (pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member);\pos; \pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))/*** hlist_for_each_entry_from - iterate over a hlist continuing from current point* @pos: the type * to use as a loop cursor.* @member: the name of the hlist_node within the struct.*/ #define hlist_for_each_entry_from(pos, member) \for (; pos; \pos = hlist_entry_safe((pos)->member.next, typeof(*(pos)), member))/*** hlist_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 &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(pos, n, head, member) \for (pos = hlist_entry_safe((head)->first, typeof(*pos), member);\pos && ({ n = pos->member.next; 1; }); \pos = hlist_entry_safe(n, typeof(*pos), member))#endif // LIST_H_

三、一個簡單的例子

#include <stdio.h> #include <stdlib.h> #include "list.h"struct kool_list{int to;struct list_head list;int from; };int main(int argc, char **argv){struct kool_list *tmp;struct list_head *pos, *q;unsigned int i;struct kool_list mylist;INIT_LIST_HEAD(&mylist.list);for(i=5; i!=0; --i){tmp= (struct kool_list *)malloc(sizeof(struct kool_list));printf("enter to and from:");scanf("%d %d", &tmp->to, &tmp->from);list_add(&(tmp->list), &(mylist.list));}printf("\n");printf("traversing the list using list_for_each_entry()\n");list_for_each_entry(tmp, &mylist.list, list)printf("to= %d from= %d\n", tmp->to, tmp->from);printf("\n");printf("deleting the list using list_for_each_safe()\n");list_for_each_safe(pos, q, &mylist.list){tmp= list_entry(pos, struct kool_list, list);printf("freeing item to= %d from= %d\n", tmp->to, tmp->from);list_del(pos);free(tmp);}return 0; }

這個例子中我使用了list.h作頭文件，這樣我就可以使用其中的函數了，先創(chuàng)建了一個結構體作為頭結點，然后使用list_add函數添加了5個結點，再用三種遍歷方式輸出結果。從這個例子中也可以看出list_add添加結點的特點。

REF

http://blog.csdn.net/hty46565/article/details/71532022

https://www.cnblogs.com/hummersofdie/p/3727703.html

轉載于:https://www.cnblogs.com/muahao/p/8109733.html

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