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c简单数据结构-循环双向链表
基于linux的数据域在节点外面的链表
#include "list.h"
/*
* 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 void __list_add(struct gxlist_head *new_node, struct gxlist_head *head, struct gxlist_head *head_next)
{
head_next->prev = new_node;
new_node->next = head_next;
new_node->prev = head;
head->next = new_node;
}
/**
* 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.
*/
void gxlist_add(struct gxlist_head *new_node, struct gxlist_head *head)
{
__list_add(new_node, 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.
*/
void gxlist_add_tail(struct gxlist_head *new_node, struct gxlist_head *head)
{
__list_add(new_node, 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 void __list_del(struct gxlist_head *prev_head, struct gxlist_head *next_head)
{
next_head->prev = prev_head;
prev_head->next = next_head;
}
/**
* 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.
*/
void gxlist_del(struct gxlist_head *entry)
{
__list_del(entry->prev, entry->next);
}
/**
* list_del_init - deletes entry from list and reinitialize it.
* @entry: the element to delete from the list.
*/
void gxlist_del_init(struct gxlist_head *entry)
{
__list_del(entry->prev, entry->next);
GX_INIT_LIST_HEAD(entry);
}
/**
* list_empty - tests whether a list is empty
* @head: the list to test.
*/
int gxlist_empty(struct gxlist_head *head)
{
return head->next == head;
}
struct gxlist_head *gxlist_get(struct gxlist_head *head)
{
struct gxlist_head *first = head->next;
if (first != head) {
__list_del(first->prev, first->next);
return first;
}
return 0;
}
/**
* list_splice - join two lists
* @list: the new list to add.
* @head: the place to add it in the first list.
*/
void gxlist_splice(struct gxlist_head *list, struct gxlist_head *head)
{
struct gxlist_head *first = list->next;
if (first != list) {
struct gxlist_head *last = list->prev;
struct gxlist_head *at = head->next;
first->prev = head;
head->next = first;
last->next = at;
at->prev = last;
}
}#ifndef _LIST_H_
#define _LIST_H_
typedef struct gxlist_head
{
struct gxlist_head *next, *prev;
} Head;
#define GX_LIST_HEAD_INIT(name) { &(name), &(name) }
#define GX_LIST_HEAD(name) \
struct gxlist_head name = GX_LIST_HEAD_INIT(name)
#define GX_INIT_LIST_HEAD(ptr) do { \
(ptr)->next = (ptr); (ptr)->prev = (ptr); \
} while (0)
void gxlist_add (struct gxlist_head *newnode, struct gxlist_head *head);
void gxlist_add_tail(struct gxlist_head *newnode, struct gxlist_head *head);
void gxlist_del (struct gxlist_head *entry);
void gxlist_del_init(struct gxlist_head *entry);
int gxlist_empty (struct gxlist_head *head );
void gxlist_splice (struct gxlist_head *list, struct gxlist_head *head);
struct gxlist_head *gxlist_get(struct gxlist_head *head);
#define gxlist_entry(ptr, type, member) \
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))
#define gxlist_for_each(pos, head) \
for (pos = (head)->next; pos != (head); \
pos = pos->next)
#endif如何使用linux的双向通用链表
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include "list.h"
typedef struct node {
struct gxlist_head list_node;//这里使用的时结构体而不是结构体指针
//如果写指针的话还要给节点分配内存，太麻烦。
char *name;
} Node;
typedef struct list {
Head head;
int node_num;
} List;
Node* node_create(char *name){
Node *node = (Node*)malloc(sizeof(Node));
if (node) {
node->name = name;
}
return node;
}
List* list_create(void)
{
List *list = (List*)malloc(sizeof(List));
if (list) {
GX_INIT_LIST_HEAD(&list->head);
list->node_num = 0;
}
return list;
}
int list_add_node(List *list, char *name)
{
Node *new_node = node_create(name);
gxlist_add(&new_node->list_node, &list->head);
list->node_num++;
return 0;
}
int list_del_node(List *list, char *name)
{
int ret = -1;
struct gxlist_head *pos;
Node *node = NULL;
gxlist_for_each(pos, &list->head){//注意这个宏的使用
node = gxlist_entry(pos, Node, list_node);
if (strncmp(node->name, name, 20) == 0){
ret = 0;
break;
}
}
if (ret == 0) {
gxlist_del(&node->list_node);
free(node);
list->node_num--;
}
return ret;
}
int list_print(List *list)
{
struct gxlist_head *pos;
Node *node;
gxlist_for_each(pos, &list->head){
node = gxlist_entry(pos, Node, list_node);
printf("%s\n", node->name);
}
return 0;
}
int list_destory(List *list)
{
struct gxlist_head *pos;
Node *node, *prev=NULL;
gxlist_for_each(pos, &list->head){
node = gxlist_entry(pos, Node, list_node);
if (prev)
free(prev);
prev = node;
}
free(node);
return 0;
}
int main()
{
List *list;
list = list_create();
list_add_node(list, "node one");
list_add_node(list, "node two");
list_add_node(list, "node three");
list_add_node(list, "node four");
list_print(list);
printf("\n");
list_del_node(list, "node two");
list_print(list);
printf("\n");
list_add_node(list, "node five");
list_print(list);
list_destory(list);
return 0;
}总结
- 使用的要点就是，自己的结构体（数据域包含链表节点）的定义
两个宏gxlist_entry, gxlist_for_each的理解和使用
. 通用链表宏
由结构体中某一个结构体成员的地址,结构体类型知道整个结构体的地址。`#define gx_list_entry(type, ptr, member) \ (type*)((char*)ptr - (unsigned long)&(((type *)0)->member))`
这个非常容易理解，结构体地址 = 成员地址 - 成员地址偏移
自己实现的通用链表，和linux里面经典的链表相比，最大的实现的区别是，linux链表中的每个节点只包
指针,要找到数据域的话，就通过链表的节点反向找到对应的包含链表节点和数据域的结构体。而自己实现
的每个节点包含指针域和数据域。