linux内核链表
一、链表代码
下面链表代码并不完整，完整代码可以到github上linux内核下载，网址linux/include at master · torvalds/linux · GitHub，在linux目录路径为 linux-master\include\linux\list.h
注：下面链表代码只能在linux环境运行，windows运行不了
/** Copy from linux/list.h*/#ifndef _GCP_MISC_LIST_H_
#define _GCP_MISC_LIST_H_#ifdef __cplusplus
extern "C" {
#endif#include <stddef.h>#define LIST_POISON1 NULL
#define LIST_POISON2 NULL#define container_of(ptr, type, member) \({ \const typeof(((type *)0)->member) *__mptr = (ptr); \(type *)((char *)__mptr - offsetof(type, member)); \})struct list_head {struct list_head *prev;struct list_head *next;
};#define LIST_HEAD_INIT(name) \{ &(name), &(name) }#define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)/*** init_list_head - Initialize a list_head structure* @list: list_head structure to be initialized.** Initializes the list_head to point to itself. If it is a list header,* the result is an empty list.*/
static inline void init_list_head(struct list_head *list) {list->prev = list;list->next = list;
}static inline void __list_add(struct list_head *new_entry, struct list_head *prev,struct list_head *next) {next->prev = new_entry;new_entry->next = next;new_entry->prev = prev;prev->next = new_entry;
}/*** list_add - add a new_entry entry after the specified head* @new_entry: new_entry entry to be added* @head: list head to add it after** Insert a new_entry entry after the specified head.* This is good for implementing stacks.*/
static inline void list_add(struct list_head *new_entry, struct list_head *head) {__list_add(new_entry, head, head->next);
}/*** list_add_tail - add a new_entry entry before the specified head* @new_entry: new_entry entry to be added* @head: list head to add it before** Insert a new_entry entry before the specified head.* This is useful for implementing queues.*/
static inline void list_add_tail(struct list_head *new_entry, struct list_head *head) {__list_add(new_entry, head->prev, head);
}static inline void __list_del(struct list_head *prev, struct list_head *next) {prev->next = next;next->prev = prev;
}/*** 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;
}static inline void __list_splice(struct list_head *list, struct list_head *head) {struct list_head *first = list->next;struct list_head *last = list->prev;struct list_head *at = head->next;first->prev = head;head->next = first;last->next = at;at->prev = last;
}
/*** 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_splice - join two lists* @list: the new_entry list to add.* @head: the place to add it in the first list.*/
static inline void list_splice(struct list_head *list, struct list_head *head) {if (!list_empty(list))__list_splice(list, head);
}
/*** list_replace - replace old entry by new_entry one* @old : the element to be replaced* @new_entry : the new_entry element to insert** If @old was empty, it will be overwritten.*/
static inline void list_replace(struct list_head *old, struct list_head *new_entry) {new_entry->next = old->next;new_entry->next->prev = new_entry;new_entry->prev = old->prev;new_entry->prev->next = new_entry;
}/*** list_replace_init - replace old entry by new one and initialize the old 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_init(struct list_head *old, struct list_head *new_entry) {list_replace(old, new_entry);init_list_head(old);
}
/*** 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_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_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_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_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_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))#ifdef __cplusplus
}
#endif#endif /* _GCP_MISC_LIST_H_ */
二、简单演示
#include <stdio.h>
#include <stdlib.h>
#include "list.h"typedef struct node{int id;struct list_head list
} Node;int main() {struct list_head list_node_head;init_list_head(&list_node_head); // 初始化链表for(int i = 0; i < 10; i ++){Node* newNode = (Node*)malloc(sizeof(Node));newNode->id = i;list_add(&newNode->list, &list_node_head); // 添加节点}Node* currentNode, *nextNode; // 临时变量list_for_each_entry(currentNode, &list_node_head, list){ // 遍历节点printf("Node ID: %d\n", currentNode->id); }list_for_each_entry_safe(currentNode, nextNode, &list_node_head, list) { // 释放内存list_del(¤tNode->list);free(currentNode);}return 0;
}三、详细解释
linux内核链表是其他结构体中来包含struct list_head来实现的，巧妙的运用了宏和链表元素list_head在结构体内的位置关系构。
1.该宏通过struct list_head在结构体的相对位置来确定节点头位置。
比如这样的结构体
struct node{
int id;
struct list_head list
} ; list_node_head->list，通过list与id相对位置关系来得出struct node的地址，最后 获取id的值。
#define container_of(ptr, type, member) \({ \const typeof(((type *)0)->member) *__mptr = (ptr); \(type *)((char *)__mptr - offsetof(type, member)); \})2.链表初始化，两种初始化方式
#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->prev = list;list->next = list;
}3.遍历
/**
* @pos 是临时指针，记录遍历节点的，类型：你定义的结构体，如举例的 Node 结构体
* @head 是头指针，类型：struct list_head
* @member 是在结构体中，struct list_head 的名称，如举例中Node结构体的list
*/#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(currentNode, &list_node_head, list)
内容不过多说，大家自己看英文注释，都很清楚。