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2012-06-20 17:00:44

list.h

#ifndef __LIST_H
#define __LIST_H

/* This file is from Linux Kernel (include/linux/list.h)
* and modified by simply removing hardware prefetching of list items.
* Here by copyright, credits attributed to wherever they belong.
* Kulesh Shanmugasundaram (kulesh [squiggly] isis.poly.edu)
*/


/*
* 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;
};

/*
 *init the head node,point to itself
 */

#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!
*/

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.
*/

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.
*/

static inline void list_del(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
    entry->next = (void *) 0;
    entry->prev = (void *) 0;
}

/**
* 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_empty – tests whether a list is empty
* @head: the list to test.
*/

static inline int list_empty(struct list_head *head)
{
    return head->next == head;
}

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_splice – join two lists
* @list: the new 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_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);
        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) \
((type *)((char *)(ptr)-(unsigned long)(&((type *)0)->member)))

/**
* list_for_each - iterate over a list
* @pos: the &struct list_head to use as a loop counter.
* @head: the head for your list.
*/

#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 counter.
* @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 counter.
* @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 counter.
* @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_entry_safe – iterate over list of given type safe against removal of list entry
* @pos: the type * to use as a loop counter.
* @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))

#endif

测试代码listtest.c

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

struct kool_list
{
    int to;
    struct list_head list;
    int from;
};

int main(int argc, char **argv)
{
    struct kool_list *tmp;
    struct list_head *pos, *q;
    unsigned int i;

    struct kool_list mylist;
    INIT_LIST_HEAD(&mylist.list); /*初始化链表头*/

    /* 给mylist增加元素 */
    for(i=5; i!=0; --i)
    {
        tmp= (struct kool_list *)malloc(sizeof(struct kool_list));

        /* 或者INIT_LIST_HEAD(&tmp->list); */
        printf("enter to and from:");
        scanf("%d %d", &tmp->to, &tmp->from);

        list_add(&(tmp->list), &(mylist.list));
        /* 也可以用list_add_tail() 在表尾增加元素*/
    }
    printf("\n");

    printf("traversing the list using list_for_each()\n");
    list_for_each(pos, &mylist.list)
    {
    /* 在这里 pos->next 指向next 节点, pos->prev指向前一个节点.这里的节点是
        struct kool_list类型. 但是,我们需要访问节点本身,

        而不是节点中的list字段,宏list_entry()正是为此目的。*/


        tmp= list_entry(pos, struct kool_list, list);

        printf("to= %d from= %d\n", tmp->to, tmp->from);

    }
    printf("\n");
    /* 因为这是循环链表,也可以以相反的顺序遍历它,
     *为此,只需要用'list_for_each_prev'代替'list_for_each',

     * 也可以调用list_for_each_entry() 对给定类型的节点进行遍历。
     * 例如:
     */

    printf("traversing the list using list_for_each_entry()\n");
    list_for_each_entry(tmp, &mylist.list, list)
    printf("to= %d from= %d\n", tmp->to, tmp->from);
    printf("\n");

    /*现在,我们可以释放 kool_list节点了.我们本可以调用 list_del()删除节点元素,

     * 但为了避免遍历链表的过程中删除元素出错,因此调用另一个更加安全的宏 list_for_each_safe(),

     */


    printf("deleting the list using list_for_each_safe()\n");
    list_for_each_safe(pos, q, &mylist.list)
    {
        tmp= list_entry(pos, struct kool_list, list);
        printf("freeing item to= %d from= %d\n", tmp->to, tmp->from);
        list_del(pos);
        free(tmp);
    }

    return 0;
}


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