Linux 链表实例应用程序

Linux 链表实例应用程序

/*********************************************************************
 *               
 * Filename:      pfile.c
 * Version:       1.0
 * Description:   Demo for Linux LIST utility
 * Compilation:   gcc –D__KERNEL__ -I/usr/src/linux/include pfile.c
 * Status:        Stable
 * Author:        Yang Shazhou<pubb@163.net>
 * Created at:    Thu Jul 15 13:50:33 2004
 * Modified at:   Thu Jul 15 14:39:03 2004
 * Modified by:   Yang Shazhou<pubb@163.net>
 *
 *     Copyright (c) 2004 Yang Shazhou, All Rights Reserved.
 *    
 *     This program is free software; you can redistribute it and/or
 *     modify it under the terms of the GNU General Public License as
 *     published by the Free Software Foundation; either version 2 of
 *     the License, or (at your option) any later version.
 *     www.bkjia.com
 *     This program is distributed in the hope that it will be useful,
 *     but WITHOUT ANY WARRANTY; without even the implied warranty of
 *     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
 *     GNU General Public License for more details.
 *
 *     You should have received a copy of the GNU General Public License
 *     along with this program; if not, write to the Free Software
 *     Foundation, Inc., 59 Temple Place, Suite 330, Boston,
 *     MA 02111-1307 USA
 *    
 ********************************************************************/
#include <linux/list.h>
#include <stdio.h>
#include <strings.h>

int main(int argc,char *argv[])
{
 LIST_HEAD(list);  //定义存放文件内容的链表
 FILE *fp;

 struct file_store {
  char c;
  struct list_head node;
 } *pstore;

 if(argc<2){
  printf("usage: pfile <filename> <[r]>\n");
  return -1;
 }
 if(!(fp=fopen(argv[1],"rb"))){
  printf("fopen(%s) error\n",argv[1]);
         return -1;
 }

 /* 读文件到链表 */
 while(1){
  if(!(pstore=(struct file_store *)malloc(sizeof(struct file_store))))
   break;
  pstore->c=fgetc(fp);
  if(feof(fp)){
   free(pstore);
   break;
  }
  list_add_tail(&pstore->node,&list);   //将本字符插入链表中
 }
 fclose(fp);

 /* 遍历链表，输出链表中的节点个数，即文件字符数 */
 int count=0;
 struct list_head *p;
 list_for_each(p,&list){
  count++;
 }
 printf("%s has altogether %d character(s)\n",argv[1],count);

 /* 根据命令行参数正向/反向遍历链表，输出链表中存放的字符，同时释放各节点 */
 if(argc>2 && !strcasecmp(argv[2],"r")){
  struct list_head *p;
  list_for_each_entry_reverse(pstore,&list,node){  //反向遍历，没有保护
   p=pstore->node.next;
   list_del(&pstore->node);
   putchar(pstore->c);
   free(pstore);
   /* 如果没有这一句，将报segmentation fault */
pstore=list_entry(p,struct file_store,node); //取数据项
  }
 }else{
  struct file_store *p;
  list_for_each_entry_safe(pstore,p,&list,node){  //正向遍历，有保护
   list_del(&pstore->node);
   putchar(pstore->c);
   free(pstore);
  }
 }

 return 0;
}