代码片段----内核链表使用一例

Makefile

CC=gcc


main:main.o


clean:
    $(RM) *.o main

.PHONY:clean

main.c

#include "list.h"
#include <stdio.h>


typedef struct 
{
    unsigned long gp;  // (group<<3)|(pnum&0x7)
    unsigned long on;  // on or off
    unsigned long delay;
    unsigned long count;
    struct  list_head p;
}GPIO_NODE;

int main(int argc, const char *argv[])
{

    GPIO_NODE *a1;
    GPIO_NODE *a2;
    GPIO_NODE *a3;
    GPIO_NODE *a4;
    struct list_head *q = NULL;
    struct list_head *q1 = NULL;
    GPIO_NODE *a5;

    LIST_HEAD(gpio_list);

    a1 = (GPIO_NODE *)malloc(sizeof(GPIO_NODE));
    a2 = (GPIO_NODE *)malloc(sizeof(GPIO_NODE));
    a3 = (GPIO_NODE *)malloc(sizeof(GPIO_NODE));
    a4 = (GPIO_NODE *)malloc(sizeof(GPIO_NODE));

    a1->gp = 1;
    a1->on = 1;
    a1->delay = 1;
    a1->count = 1;

    a2->gp = 2;
    a2->on = 2;
    a2->delay = 2;
    a2->count = 2;

    a3->gp = 3;
    a3->on = 3;
    a3->delay = 3;
    a3->count = 3;


    a4->gp = 4;
    a4->on = 4;
    a4->delay = 4;
    a4->count = 4;

    list_add_tail(&(a1->p), &gpio_list);
    list_add_tail(&(a2->p), &gpio_list);
    list_add_tail(&(a3->p), &gpio_list);
    list_add_tail(&(a4->p), &gpio_list);

    list_for_each_safe(q, q1, &gpio_list) {
        a5 = list_entry(q, GPIO_NODE, p); 
        if(a5->gp > 3)
        {
            printf("a5->gp = %d
", a5->gp);
            printf("a5->on = %d
", a5->on);
            printf("a5->delay = %d
", a5->delay);
            printf("a5->count = %d
", a5->count);

            if (!list_empty(&gpio_list))
            {
                list_del(q);
                printf("free node %d
", a5->gp);
                free(a5);
            }
        }
    }

    list_for_each_safe(q, q1, &gpio_list)
    {
        a5 = list_entry(q, GPIO_NODE, p);

        printf("a5->gp = %d
", a5->gp);
        printf("a5->on = %d
", a5->on);
        printf("a5->delay = %d
", a5->delay);
        printf("a5->count = %d
", a5->count);

        if (!list_empty(&gpio_list))
        {
            list_del(q);
            printf("free node %d
", a5->gp);
            free(a5);
        }
    }


    return 0;
}

list.h

http://files.cnblogs.com/pengdonglin137/list.rar

参考：http://blog.csdn.net/xnwyd/article/details/7359373

Linux内核链表的核心思想是：在用户自定义的结构A中声明list_head类型的成员p，这样每个结构类型为A的变量a中，都拥有同样的成员p，如下：

struct A{

int property;

struct list_head p;

}

其中，list_head结构类型定义如下：

struct list_head {

struct list_head *next,*prev;

};

list_head拥有两个指针成员，其类型都为list_head，分别为前驱指针prev和后驱指针next。

假设：

（1）多个结构类型为A的变量a1...an，其list_head结构类型的成员为p1...pn

（2）一个list_head结构类型的变量head，代表头节点

使：

（1）head.next= p1 ; head.prev = pn

（2）p1.prev = head，p1.next = p2;

（3）p2.prev= p1 , p2.next = p3;

…

（n）pn.prev= pn-1 , pn.next = head

以上，则构成了一个循环链表。

因p是嵌入到a中的，p与a的地址偏移量可知，又因为head的地址可知，所以每个结构类型为A的链表节点a1...an的地址也是可以计算出的，从而可实现链表的遍历，在此基础上，则可以实现链表的各种操作。

下面是从linux内核中移植出来的简单链表，list.h和list.c:

list.h:

#ifndef _INIT_LIST_H_
#define _INIT_LIST_H_

#ifndef offsetof
/* Offset of member MEMBER in a struct of type TYPE. */
#define offsetof(TYPE, MEMBER) ((size_t) &((TYPE *)0)->MEMBER)
#endif

struct listnode
{
    struct listnode *next;
    struct listnode *prev;
};

#define node_to_item(node, container, member)
    (container *) (((char*) (node)) - offsetof(container, member))

#define list_declare(name)
    struct listnode name = {
        .next = &name,
        .prev = &name,
    }

#define list_for_each(node, list)
    for (node = (list)->next; node != (list); node = node->next)

#define list_for_each_reverse(node, list)
    for (node = (list)->prev; node != (list); node = node->prev)

void list_init(struct listnode *list);
void list_add_tail(struct listnode *list, struct listnode *item);
void list_remove(struct listnode *item);

#define list_empty(list) ((list) == (list)->next)
#define list_head(list) ((list)->next)
#define list_tail(list) ((list)->prev)

#endif

list.c：

#include "list.h"

void list_init(struct listnode *node)
{
    node->next = node;
    node->prev = node;
}

void list_add_tail(struct listnode *head, struct listnode *item)
{
    item->next = head;
    item->prev = head->prev;
    head->prev->next = item;
    head->prev = item;
}

void list_remove(struct listnode *item)
{
    item->next->prev = item->prev;
    item->prev->next = item->next;
}

测试代码list_test.c:

#include<stdio.h>
#include<stdlib.h>
#include "list.h"

#define STUDENT_FREE_MEMORY

//声明链表节点
typedef struct {
    int id;
    char *name;
    struct listnode _list;
}student;

//遍历函数指针
typedef void (*student_foreach_fun)(student *stu,void *data);


//声明链表
static list_declare(student_list);

//添加节点
int student_add(struct listnode *list,student *stu)
{
    list_init(&stu->_list);
    list_add_tail(list,&stu->_list);
}

//删除节点，释放节点空间
int student_del(struct listnode *list,int id)
{
    struct listnode *node;
    student *stu;
    list_for_each(node,list){
        stu = node_to_item(node,student,_list);
        if(id == stu->id){
            printf("list_del, id:%d,name:%s
",stu->id,stu->name);
            list_remove(node);
#ifdef STUDENT_FREE_MEMORY
            //释放节点空间
            free(stu);
            stu = NULL;
#endif
            return 1;

        }

    }

    return 0;
}

//节点遍历
void student_foreach(struct listnode *list,student_foreach_fun fun,void *data)
{
    struct listnode *node;
    student *stu;
    list_for_each(node,list){
        stu = node_to_item(node,student,_list);
        fun(stu,data);
    }

}

//打印节点信息
void student_print(student *stu,void *data)
{
    printf("id:%d,name:%s
",stu->id,stu->name);
}

int main()
{
    int i,len;
    student *stu;
    char *stu_name[]={"tonny","andy","michael","leslie","john"};


    len = sizeof(stu_name)/sizeof(stu_name[0]);
    //添加节点
    for(i=0;i<len;i++){
        stu = calloc(1,sizeof(student));
        stu->id = i + 1;
        stu->name = stu_name[i];

        student_add(&student_list,stu);
    }

    //打印所有节点
    student_foreach(&student_list,student_print,(void *)0);

    //删除节点
    student_del(&student_list,1);
    student_foreach(&student_list,student_print,(void *)0);

    //删除节点
    student_del(&student_list,5);
    student_foreach(&student_list,student_print,(void *)0);

    return 0;


}

Makefile:

TARGET=list_test
SRC=list_test.c list.c
#SRC=$(wildcard *.c)
OBJ=$(SRC:.c=.o)
CFLAGS=-g -Wall -o

$(TARGET):$(SRC)
    gcc $(SRC) $(CFLAGS) $(TARGET)
clean:
    rm $(OBJ) $(TARGET)