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版权声明：本文为博主原创文章，未经博主允许不得转载。 摘要：将内核链表移植到应用程序中，实现创建，添加节点，遍历，删除的操作。 首先复习一下内核链表中经常使用的几个函数，在/include/Linux/list.h中。 创建链表：[html] view plain copy INIT_LIST_HEAD（） staticinline void INIT_LIST_HEAD(struct list_head *list) { list->next = list; list->prev = list; } 插入节点：[objc] view plain copy list_add（）在链表头插入 list_add_tail()在链表尾插入 staticinline void list_add(struct list_head *new, struct list_head *head) { __list_add(new, head, head->next); } staticinline void list_add_tail(struct list_head *new, struct list_head *head) { __list_add(new, head->prev, head); } 删除节点：[objc] view plain copy list_del() staticinline void list_del(struct list_head *entry) { __list_del(entry->prev, entry->next); entry->next = LIST_POISON1; entry->prev = LIST_POISON2; } 遍历链表：[objc] view plain copy list_for_each() #definelist_for_each(pos, head) \ for(pos = (head)->next; prefetch(pos->next), pos != (head); \ pos = pos->next) 取出节点：[objc] view plain copy list_entry() #definelist_entry(ptr, type, member) \ container_of(ptr,type, member) 移植过程中用到的其他函数： 1.malloc 函数原型：extern void *malloc(unsigned int num_bytes); 功能：分配字节长度为num_bytes内存，如果成功则返回指向内存起始地址的指针，否则返回null。 说明：这里声明为void *表示未确定类型的指针，这样使用的时候就可以强制转换为其他我们需要的任何类型的指针。 2.memset 函数原型：void *memset(void *s,int ch,seze_t n); 功能：将s指向的某一块内存中的前n个字节的内容全部填充为ch。一般用来对新申请的内存做初始化工作，ch一般都是填充0。我们在使用较大的结构体和数组的时候，都会使用其对分配到的内存清零。 3.sprintf 函数原型：int sprintf(char *buffer,const char *format，[arugument]…); 功能：把格式化的数据写入某个字符串中，返回值是字符串的长度。 移植步骤： 1.创建list.h 因为我们要写成一个app，里面用到很多内核链表的函数，都在list.h里面声明的，一开始这里我就偷懒把内核里面的list.h拷贝一份，放到我当前的工作目录下，命名为list.h，后来编译的时候提示找不到list.h里面加进去的那三个头文件，于是我又把position.h,这三个头文件注释掉了，但是提示LIST_POSITION1和LIST_POSITION2没有定义还有别的错误，于是利用grep查找，到源码目录下，把这部分拷贝到我们的list.h前面部分里面来就可以了。完整的list.c附在最后。[objc] view plain copy #ifndef _LINUX_LIST_H #define _LINUX_LIST_H #include#ifndef ARCH_HAS_PREFETCH #define ARCH_HAS_PREFETCH static inline void prefetch(const voidvoid *x){;} #endif #define LIST_POISON1 ((void *) 0x0) #define LIST_POISON2 ((void *) 0x0) #define container_of(ptr ,type,member)({ \ const typeof( ((type *)0)->member ) *__mptr = (ptr); \ (type *)( (charchar *)__mptr - offsetof(type,member) );}) 2.创建listapp.c添加头文件 这里我命名为listapp.c，因为我们要用到很多头文件，这里都添加进去，我添加的如下;[objc] view plain copy #include"list.h"//内核链表操作函数 #include//使用malloc分配内存 #include 3.创建球员信息结构体[objc] view plain copy structmember { charname[10]; intnum; intscore; intassists; structlist_head list; }; 4.main函数 主要思想是创建链表，分配内存，插入节点，遍历输出，删除节点。 编译成功后运行出现如下信息; 可以看到我们的链表操作是成功了，输出信息也与期望值一样，但是最后free的时候出现了core dump，这个问题查了下有几种解释，这里大概是数组操作越界，或者我们修改了mem区的指针信息，导致free释放内存的时候，释放到别的地方去了，这里不做深究了，留待之后结局。 最后附上list.h和listapp.c的代码，结束，如有不正确的地方还请指出，大家共同进步。 list.h如下[objc] view plain copy #ifndef _LINUX_LIST_H #define _LINUX_LIST_H #include//sprintf和printf #include //memset #ifndef ARCH_HAS_PREFETCH #define ARCH_HAS_PREFETCH static inline void prefetch(const voidvoid *x) {;} #endif #define LIST_POISON1 ((void *) 0x0) #define LIST_POISON2 ((void *) 0x0) #define container_of(ptr ,type,member) ({ \ const typeof( ((type *)0)->member ) *__mptr = (ptr); \ (type *)( (charchar *)__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. */ 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! */ #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(struct list_head *entry) { __list_del(entry->prev, entry->next); entry->next = LIST_POISON1; entry->prev = LIST_POISON2; } #else 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->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; } /* * 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 && ({ 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 listapp.c如下[objc] view plain copy #include"list.h"//内核链表操作函数 #include//使用malloc分配内存 #include //sprintf和printf #include //memset struct member { char name[100]; int num; int score; struct list_head list; }; struct list_head *pos;//遍历指针的pos，不断地指向链表中节点的指针域，需要是list_head指针类型 struct list_head member_list;//名为menber_list的链表 struct member *tmp;//存放遍历结果，为struct member类型 struct member *pmember;//member的成员 int main(void) { unsigned int i = 0; //循环变量的声明 INIT_LIST_HEAD(&member_list); //创建一个链表头，使其前向和后继指针都指向自己，传入参数必须为指针类型，所以取地址 pmember=malloc(sizeof(struct member)*4); memset(pmember,0,sizeof(struct member)*4);//为member成员分配内存，这里分配四个成员，并且对分配到的内存清零 /*给球员成员命名，编号，进球数*/ sprintf(pmember[1].name,"player %s","xu"); sprintf(pmember[2].name,"player %s","zeng"); sprintf(pmember[3].name,"player %s","le"); sprintf(pmember[4].name,"player %s","suo"); pmember[1].num=9; pmember[2].num=21; pmember[3].num=10; pmember[4].num=66; pmember[1].score=2; pmember[2].score=0; pmember[3].score=1; pmember[4].score=5; /*插入节点，list_add第一个参数是成员内部list的指针，第二个是刚才创建的链表头，这样就插入进去了*/ for(i=0;i<4;i++) { list_add(&(pmember[i+1].list),&member_list); printf("###num %d player add sucess!###\n",i+1); } /*遍历链表，并开始输出球员信息*/ printf("###start list_for_each player information###\n"); list_for_each(pos,&member_list) { tmp=list_entry(pos,struct member,list);//第一个参数为pos，第二个要给进去我们定义的球员信息结构体，最后是结构内部的list名 printf("play %d name %s score %d\n",tmp->num,tmp->name,tmp->score); } /*最后删除节点*/ for(i=0;i<4;i++) { list_del(&(pmember[i+1].list)); printf("### num %d has deleted###\n",i+1); } /*释放分配得内存*/ free(pmember); }