數據結構教程 第十六課 串操作應用舉例

教學目的： 掌握文本編輯的基本原理及方法

教學重點： 簡單文本編輯

教學難點： 串的存儲管理

授課內容：

一、復習串的堆分配存儲表示

堆分配存儲表示

二、文本編輯基本原理

圖一

文本編輯可以用於源程序的輸入和修改（如圖一）,也可用於報刊和書籍的編輯排版以及辦公室的公文書信的起草和潤色（如圖二）。

圖二

可用於文本編輯的程序很多，功能強弱差別很大，但基本操作是一致的：都包括串的查找，插入和刪除等基本操作。

對用戶來講，一個文本（文件）可以包括若干頁，每頁包括若干行，每行包括若干文字。

對文本編輯程序來講，可把整個文本看成一個長字符串，稱文本串，頁是文本串的子串，行又是頁的子串。為簡化程序復雜程度，可簡單地把文本分成若干行。

例：下面的一段源程序可以看成一個文本串，

main(){

float a,b,max;

scanf("%f,%f",&a,&b);

if (a>b) max=a;

else max=b;

};

這個文本串在內存中的存儲映像可為：

m a i n ( ) { \n f l o a t a , b , m a x ; \n s c a n f ( " % f , % f " , & a , & b ) ; \n i f a > b m a x = a ; \n e l s e m a x = b ; \n } \n

在編輯時，為指示當前編輯位置，程序中要設立頁指針、行指針、字符指針，分別指示當前頁，當前行，當前字符。因此程序中要設立頁表、行表便於查找。

三、簡單行編輯程序例

源程序

#include <conio.h>
#include <string.h>
#include "keyscode.h"
#include "menu.h"

struct line{
  int charnum;
  char *base;
};

typedef struct line SequListElemType;

#include "sequlist.h"


#define MAXLINES 1000

int key;
int cureditline=0;
int curscrtopline=0;
int cureditcol=0;
int funckey;
int editwinx=2;
int editwiny=3;
int editwinlines=20;
int mainover=0;
FILE *curfile;

char filename[255]="test.txt";

SequList *Document;

char ascii(int k);
printdoc(int startfileline,int startscrline);
readdoc(FILE *fp);

editline(int curline,int maxcolnum)
{
  char s[2000];
  setscrcolor(BLUE,YELLOW);
  strcpy(s,Document->elem[curline].base);
  getstring(editwinx,editwiny+curline-curscrtopline,s,maxcolnum);
  free(Document->elem[curline].base);
  Document->elem[curline].base=(char *)malloc(strlen(s)+1);
  strcpy(Document->elem[curline].base,s);
}

printdoc(int startfileline,int startscrline)
{
  int i;
  int j;
  cursor_hide();
  i=startscrline;
  j=startfileline;
  setscrcolor(BLUE,YELLOW);
  gotoxy(editwinx,editwiny+startscrline);
  while(i<=editwinlines && i<Document->length)
    {
      clearscrline(editwinx,editwiny+i,78);
      putsxy(editwinx,editwiny+i++,Document->elem[j++ -1].base);
    }
  while(i<=editwinlines)
    clearscrline(editwinx,editwiny+i++,78);
  cursor_show();
}

getline(FILE *fp,char *l)
{
  int i=0;
  while(!feof(fp))
    if((l[i++]=fgetc(fp))=='\n')
      break;
  l[i-1]='\0';
}

closedoc(FILE *fp)
{

  int i;
  fclose(fp);
  for(i=0;i<Document->length;i++)
    free(Document->elem[i].base);
  SequListDestroy(Document);
}

readdoc(FILE *fp)
{
  char *newline;
  char s[20000];
  int linenum=0;
  struct line curline;
  if(!fp) return;
  while(!feof(fp))
    {
      getline(fp,s);
      linenum++;
      newline=(char *)malloc(strlen(s)+1);
      strcpy(newline,s);
      curline.base=newline;
      curline.charnum=strlen(newline);
      SequListInsert(Document,linenum,curline);
    }
}

char ascii(int k)
{
  char c;
  c=(k<<8)>>8;
  if(c>=32&&c<127)
    return c;
  else
    return 0;
}

insertchar(char *s,char c,int pos)
{
  int i;
  for(i=strlen(s)+1;i>pos;i--)
    s[i]=s[i-1];
  s[i]=c;
}
deletechar(char *s,int pos)
{
  int i;
  int j;
  j=strlen(s);
  for(i=pos;i<=j;i++)
    s[i]=s[i+1];
}
clearscrline(int x,int y,int num)
{
  int i;
  for(i=0;i<num;i++)
    putcxy(x+i,y,'');
}
getsindiag(int x,int y,int w,char *title,char *s)
{
  char buf[2000];
  gettext(x,y,x+w+2,y+2,buf);
  setscrcolor(LIGHTGRAY,BLACK);
  box(x,y,w+2,3);
  putsxy(x+3,y,title);
  getstring(x+1,y+1,s,w);
  puttext(x,y,x+w+2,y+2,buf);
}

insertnewline(int linenum)
{
  struct line  l;
  l.base=(char *)malloc(80);
  l.charnum=0;
  l.base[0]='\0';
  SequListInsert(Document,linenum,l);
}
deleteline(int linenum)
{
  SequListDelete(Document,linenum);
}

getstring(int x,int y,char *s,int num)
{
  int k;
  int n;
  char c;
  int curpos=0;
  int thisover=0;
  cursor_show();
/*  putsxy(x,y,s); */
  gotoxy(x,y);
  while(!thisover)
    {
      if(k=bioskey(1))
       { switch(k){
	   case KEYEsc:
	   case KEYReturn:
	   case KEYUp:
	   case KEYDown:
	   case KEYAlt_x:
	   case KEYCtrl_y:
	     return;
	     break;
	   default:
	     bioskey(0);
	   }
       }
      else
	continue;
      switch(k){
	case KEYHome:
	  curpos=0;
	  gotoxy(x+curpos,y);
	  break;
	case KEYEnd:
	  curpos=strlen(s);
	  gotoxy(x+curpos,y);
	  break;
	case KEYReturn:
	  thisover=1;
	  break;
	case KEYLeft:
	  if(curpos) curpos--;
	  gotoxy(x+curpos,y);
	  break;
	case KEYRight:
	  if(curpos<num) curpos++;
	  gotoxy(x+curpos,y);
	  break;
	case KEYDelete:
	  if(curpos<strlen(s))
	   {
	     deletechar(s,curpos);
	     cursor_hide();
	     clearscrline(x,y,num);
	     putsxy(x,y,s);
	     gotoxy(x+curpos,y);
	     cursor_show();
	   }
	  break;
	case KEYBackspace:
	  if(curpos)
	    {
	      deletechar(s,curpos-1);
	      curpos--;
              cursor_hide();
	      clearscrline(x,y,num);
	      putsxy(x,y,s);
	      gotoxy(x+curpos,y);
	      cursor_show();
	    }
	  break;
	case KEYEsc:
	  return;
	default:
	  c=ascii(k);
	  if (c&&strlen(s)<num)
	    {
	      insertchar(s,c,curpos);
	      cursor_hide();
	      clearscrline(x,y,num);
	      curpos++;
	      putsxy(x,y,s);
	      gotoxy(x+curpos,y);
	      cursor_show();
	    }
	break;
      }
    }
}

dofunc(int itemno)
{
   switch(itemno)
    {
      case 0:
	 break;
      case 1:  /*Open file*/
	 getsindiag(3,4,50,"Open file Name",filename);
	 if(curfile=fopen(filename,"r+"))
	   {
	     readdoc(curfile);
	     printdoc(1,0);
	   }
	 break;
      case 3:
	mainover=1;
	break;
      case 21:
	showmessagew();
      default:
	break;
    }
}


main()
{ int i;
  char c;

  char  *mainmenuitem[10]={"File","Edit    ","Help"};
  char  *submenu1[10]={"New","Open","Save","Exit to system"};
  char  *submenu2[10]={"Copy","Cut","Paste   "};
  char  *submenu3[20]={"HelpContent","About"};

  initmenu(MAINMENU_V,3,&mainmenu,mainmenuitem);
  initmenu(SUBMENU_H,4,&submenu[0],submenu1);
  initmenu(SUBMENU_H,3,&submenu[1],submenu2);
  initmenu(SUBMENU_H,2,&submenu[2],submenu3);
  for(i=0;i<3;i++)
    addsubmenu(&mainmenu,i,&submenu[i]);
  definemenupos(3,1,&mainmenu);
  cursor_hide();
  showmenu(&mainmenu);
  showmainw(1,2,80,23);
  showmessagew();

  SequListInit(&Document,MAXLINES);
  insertnewline(1);
  setscrcolor(BLUE,YELLOW);
  while(!mainover)
  {
    if(key=bioskey(1))
      {if(!ascii(key))
	biOSkey(0);
      }
    else
      continue;
    switch(key){
	case KEYBackspace:
	case KEYDelete:
	case KEYHome:
	case KEYEnd:
	case KEYReturn:
	  if(cureditline-curscrtopline<editwinlines)
	    cureditline++;
	  else
	    {
	       curscrtopline++;
	       printdoc(curscrtopline+1,editwiny);
	    }
	  insertnewline(cureditline+1);
	  printdoc(curscrtopline+1,0);
	  gotoxy(editwinx,editwiny+cureditline);
	  editline(cureditline,78);
	  break;
	case KEYUp:
	  if (cureditline>0)
	    {
	      cureditline--;
	      gotoxy(editwinx,editwiny+cureditline);
	      editline(cureditline,78);
	    }
	  break;
	case KEYDown:
	  if (cureditline<Document->length-1)
	    {
	      cureditline++;
	      gotoxy(editwinx,editwiny+cureditline);
	      editline(cureditline,78);
	    }
	  break;
	case KEYCtrl_y:
	  deleteline(cureditline+1);
	  if(Document->length==0)
	    insertnewline(cureditline+1);
	  if(cureditline>=Document->length)
	    insertnewline(cureditline+1);
	  printdoc(cureditline+1,cureditline-curscrtopline);
	  gotoxy(editwinx,editwiny+cureditline);
	  editline(cureditline,78);
	  break;
	case KEYLeft:
	case KEYRight:
          break;
	case KEYCtrl_s:
	  break;
	case ESC:
	   cursor_hide();
	   dofunc(getmenuitem());
	   break;
	case KEYAlt_x:
	  mainover=1;
	  break;
	default:
	  gotoxy(editwinx,editwiny+cureditline-curscrtopline);
	  editline(cureditline,78);
	  break;
    }
  }
  closedoc(curfile);
  setscrcolor(BLACK,WHITE);
  clrscr();
  cursor_show();
}