#include   "stdio.h"
  #include   "stdlib.h"
  #include   "string.h"
  struct   line{   
      char   text[81];   
      int   num;                 /*行號*/
      struct line *next;     /*指向下一個輸入項(xiàng)目的指針   */
      struct line *prior;    /*指向前一個項(xiàng)目的指針   */
  };
    
  struct line *start;      /*指向表中第一個項(xiàng)目的指針   */
  struct line *last;       /*指向表中最后一個項(xiàng)目的指針   */
  struct line *find(int),*dls_store(struct   line   *);
     
  void   patchup(int,int),delete_text(),list(),save(char   *),load(char   *);
     
  menu_select();   
  enter(int   linenum);   
    
  void   main(int   argc,char   *argv[])   
  {   
      char   s[80],choice,fname[80];   
      int   linenum=1;   
      start=NULL;   
      last=NULL;   
      if(argc==2)   load(argv[1]);/*讀取命令行上的文件   */
      do{   
         choice=menu_select();
         switch(choice)
         {
          case   1:printf("\tlinenum :");
          gets(s);
          linenum=atoi(s);
          enter(linenum);
          break;
          case   2:delete_text();
          break;
          case   3:list();
          break;
          case   4:printf("\tfilename :");
          gets(fname);
          save(fname);
          break;
          case   5:printf("\tfilename :");
          gets(fname);
          load(fname);
          break;
          case   6:exit(0);
          }
       }while(1);

  }   
    
  /*   顯示菜單，供用戶選擇   */   
  menu_select()   
  {   
      char   s[80];   
      int   c;   
      printf("\t\t1.Enter\n");
      printf("\t\t2.Delete a line\n");
      printf("\t\t3.Display a line\n");
      printf("\t\t4.Save the file\n");
      printf("\t\t5.Open the file\n");
      printf("\t\t6.Quit\n");
      do{   
       printf("\n\n\t\t Please choice a num :");
       gets(s);
       c=atoi(s);
      }while(c<0||c>6);
      return(c);   
  }   
    
  /*將文本插在指定行端部*/
  enter(int   linenum)   
  {   
      struct   line   *info;   
      for(;;)
      {   
        info=(struct   line  *)malloc(sizeof(struct   line));
        if(!info)
       {
        printf("\t!   內(nèi)存不夠！\n");
        return(NULL);
       }
      printf("%d:",linenum);   
      gets(info->text);   
      info->num=linenum;   
      if(*info->text)
       {
        if(find(linenum))   patchup(linenum,1);
        if(*info->text)   start=dls_store(info);
       }
      else   break;   
      linenum++;   
      }   
      return(linenum);   
  }   
    
  /*當(dāng)文本內(nèi)容插在文件中間時其下面的內(nèi)容的行號必須增加1，而     */   
  /*刪除時，被刪除的文本后面的行號必須減1   */   
  void   patchup(int   n,int   incr)   
  {   
      struct   line   *i;   
      i=find(n);   
      while(i){   
      i->num=i->num+incr;
      i=i->next;
      }
  }   
  /*按行號排序后插入   */   
  struct   line   *dls_store(struct   line   *i)   
  {   
      struct   line   *old,*p;   
      if(last==NULL)
      {
       i->next=NULL;
       i->prior=NULL;
       last=i;
       return(i);
      }
      p=start;   
      old=NULL;   
      while(p)
      {
        if(p->num)
        {
         old=p;
         p=p->next;
        }
        else
        {
          if(p->prior)
          {
            p->prior->next=i;
            i->next=p;
            p->prior=i;
            return   start;
          }
          i->next=p;
          i->prior=NULL;
          p->prior=i;
          return(i);
        }
      }
      old->next=i;
      i->next=NULL;
      i->prior=old;
      last=i;
      return   start;
  }   
    
  /*刪除一行   */   
  void   delete_text()   
  {   
      struct   line   *info;   
      char   s[80];   
      int   linenum;   
      printf("\tlinenum :");
      gets(s);   
      linenum=atoi(s);   
      info=find(linenum);   
      if(info)
      {
        if(start==info)
        {
          start=info->next;
          if(start)   start->prior=NULL;
          else       last=NULL;
        }
        else
        {
        info->prior->next=info->next;
        if(info!=last)
        info->next->prior=info->prior;
        else   last=info->prior;
        }
        free(info);
        patchup(linenum+1,-1);
      }
  }   
    
  /*查找一行文本     */   
  struct   line   *find(int   linenum)   
  {   
      struct   line   *info;   
      info=start;   
      while(info)
      {   
        if(linenum==info->num)   return(info);
        info=info->next;
      }   
      return(NULL);   
  }   
    
  /*顯示文本     */   
  void   list()   
  {   
      struct   line   *info;   
      info=start;   
      while(info)
      {   
        printf("%d:%s\n",info->num,info->text);
        info=info->next;
      }   
      printf("\n\n");   
  }   
    
  /*存文件   */   
  void   save(char   *fname)   
  {   
      struct   line   *info;   
      char   *p;   
      FILE   *fp;   
      if((fp=fopen(fname,"w"))==NULL)
      {   
        printf("\t Can't open the file !\n");
        exit(0);
      }   
      printf("\t Saving :\n");
      info=start;   
      while(info)
      {   
       p=info->text;
       while(*p)   putc(*p++,fp);
       putc('\n',fp);
       info=info->next;
      }
      fclose(fp);   
  }   
    
/*讀取文件   */
  void   load(char   *fname)   
  {   
      struct   line   *info,*temp;   
      char   *p;   
      FILE   *fp;   
      int   size,inct;   
      if((fp=fopen(fname,"r+"))==NULL)
        {
          printf("\t Can't open the file !\n");
          exit(0);
        }
      while(start)
        {
          temp=start;
          start=start->next;
          free(temp);
        }   
      printf("\n\t Reading...\n");
      size=sizeof(struct   line);
      start=(struct   line*)malloc(size);
      if(!start)
        {
           printf("\n\t內(nèi)存已經(jīng)用完 !");
           return;
        }   
      info=start;
      p=info->text;
      inct=1;
      while((*p=getc(fp))!=EOF)
        {
           p++;
           while((*p=getc(fp))!='\n')   p++;
           *p='\0';
           info->num=inct++;
           info->next=(struct   line*)malloc(size);
           if(!info->next)
            {
              printf("\n\t內(nèi)存已經(jīng)用完 !");
              return;
            }
            info->prior=temp;
            temp=info;
            info=info->next;
            p=info->text;
        }
        temp->next=NULL;
        last=temp;
        free(info);
        start->prior=NULL;
        fclose(fp);
  }