linux下双向链表的实现

操作系统：ubuntu10.04


前言：
    在开发中，经常需要使用到链表，因此参考linux内核的链表的实现。

一，源码

#ifndef __LIST_H__
#define __LIST_H__

#ifdef __cplusplus
extern "C" {
#endif

/* Define to prevent recursive inclusion
-------------------------------------*/
#include "types.h"


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
 */
/* prev <=> new <=> next */
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;
}



/**
 * 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.
 */
 /* head <=> lastest <=> ... <=> third <=> second <=> first */
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.
 */
 /* first <=> second <=> third <=> ... <=> lastest <=> head */
static    inline void    list_add_tail(struct list_head *new,
                                struct list_head *head)
{
    __list_add(new,head->prev,head);
}




#define LIST_POISON1 ((void *) 0x00100100)
#define LIST_POISON2 ((void *) 0x00200200)


/*
 * 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
 */
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.
 */
static    inline void    list_del(struct list_head *entry)
{

    __list_del(entry->prev,entry->next);
    entry->next = LIST_POISON1;
    entry->prev = LIST_POISON2;
}




/**
 * 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);
}


/**
 * 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    offsetof(TYPE,MEMBER)    ((size_t)&((TYPE*)0)->MEMBER)
#define    container_of(ptr,type,member)     ({ \
            const typeof(((type *)0)->member) *__mptr = (ptr);\
            (type*)((char *)__mptr - offsetof(type,member));})


/**
 * 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.
 *
 * 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; 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    -    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))




#ifdef __cplusplus
}
#endif

#endif

二，测试
    1，测试代码

/*
 * list begin
 */

typedef    struct _test_list
{
    char                name[20];
    int                    age;
    struct list_head    list;
}test_list_t;

struct list_head        t_list        = LIST_HEAD_INIT(t_list);

static    void    _item_init(char * name,int    age)
{
    test_list_t    *item = (test_list_t*)malloc(sizeof(test_list_t));

    strcpy(item->name,name);
    item->age = age;

    list_add(&item->list,&t_list);
}

static    void    _item_destroy()
{
    test_list_t            *entry     = NULL;
    struct list_head    *temp    = NULL;
    struct list_head    *item    = NULL;

    printf("destroy\n");
    list_for_each_safe(item,temp,&t_list)
    {
        entry = list_entry(item, struct _test_list, list);
        list_del(item);
        printf("next : %p\t prev : %p\n",entry->list.next,entry->list.prev);
        printf("name : %s\t age : %d\n",entry->name,entry->age);
        free(entry);
        printf("delete\n");
        entry = NULL;
    }
}

static    void    _item_display()
{
    test_list_t    *entry = NULL;

    printf("display\n");
    list_for_each_entry(entry, &t_list, list)
    {
        printf("name : %s\t age : %d\n",entry->name,entry->age);
    }
}

static    void    list_oper(void)
{
    _item_init("wo",10);
    _item_init("shi",20);
    _item_init("zhong",30);
    _item_init("guo",40);
    _item_init("ren",50);

    _item_display();

    _item_destroy();

}

void    test_list()
{
    list_oper();
}

/*
 * list end
 */

    2，测试结果
    

    3，注意事项
        a，在删除时，要注意指针问题。
            建议使用 list_for_each_safe，而不是 list_for_each_entry。