举例说，Linux核心名单（两）

使用列表

我认为最好的方式，成为熟悉的核心列表功能是看一些简单的例子，素材去更好的理解链表。

以下是一个样例。包括创建。加入。删除和遍历链表。

<span style="font-size:18px;">#include <stdio.h>
#include <stdlib.h>

#include "list.h"


struct kool_list{
  int to;
  struct list_head list;
  int from;
  };//自己定义欲链接的数据额结构，并包括双向链表结构

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);//初始化一个链表表头

  /* 向<span style="font-family: Arial, Helvetica, sans-serif;">mylist中加入元素</span><span style="font-family: Arial, Helvetica, sans-serif;"> */</span>
  for(i=5; i!=0; --i){
    tmp= (struct kool_list *)malloc(sizeof(struct kool_list));

    /* INIT_LIST_HEAD(&tmp->list); 
     *
     * this initializes a dynamically allocated list_head. we
     * you can omit this if subsequent call is add_list() or 
     * anything along that line because the next, prev
     * fields get initialized in those functions.
     */
    printf("enter to and from:");
    scanf("%d %d", &tmp->to, &tmp->from);

    /* add the new item 'tmp' to the list of items in mylist */
    list_add(&(tmp->list), &(mylist.list));//项链表中加入新的元素节点,tmp中的list
    /* you can also use list_add_tail() which adds new items to
     * the tail end of the list
     */
  }
  printf("\n");


  /* now you have a circularly linked list of items of type struct kool_list.
   * now let us go through the items and print them out
   */


  /* list_for_each() is a macro for a for loop. 
   * first parameter is used as the counter in for loop. in other words, inside the
   * loop it points to the current item's list_head.
   * second parameter is the pointer to the list. it is not manipulated by the macro.
   */
  printf("traversing the list using list_for_each()\n");
  list_for_each(pos, &mylist.list){//遍历链表，pos依次指向链表的元素

    /* at this point: pos->next points to the next item's 'list' variable and 
     * pos->prev points to the previous item's 'list' variable. Here item is 
     * of type struct kool_list. But we need to access the item itself not the 
     * variable 'list' in the item! macro list_entry() does just that. See "How
     * does this work?" below for an explanation of how this is done.
     */
     tmp= list_entry(pos, struct kool_list, list);//获得包括pos节点的数据结构<span style="font-family: Arial, Helvetica, sans-serif;">struct kool_list指针</span>

     /* given a pointer to struct list_head, type of data structure it is part of,
      * and it's name (struct list_head's name in the data structure) it returns a
      * pointer to the data structure in which the pointer is part of.
      * For example, in the above line list_entry() will return a pointer to the
      * struct kool_list item it is embedded in!
      */

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

  }
  printf("\n");
  /* since this is a circularly linked list. you can traverse the list in reverse order
   * as well. all you need to do is replace 'list_for_each' with 'list_for_each_prev'
   * everything else remain the same!
   *
   * Also you can traverse the list using list_for_each_entry() to iterate over a given
   * type of entries. For example:
   */
  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");


  /* now let's be good and free the kool_list items. since we will be removing items
   * off the list using list_del() we need to use a safer version of the list_for_each() 
   * macro aptly named list_for_each_safe(). Note that you MUST use this macro if the loop 
   * involves deletions of items (or moving items from one list to another).
   */
  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;
}</span>

几种常用的核心清单API实现。上述案件Linux核心名单（三）介绍。