video.c

一个迷你操作系统gazos的源码

/*
GazOS Operating System
Copyright (C) 1999  Gareth Owen <[e-mail]>

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.

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 "video.h"
#include "io.h"

unsigned char *VIDEO_MEMORY = (char *)0xB8000;

void kprint(char *string)		/* Print text to the screen	*/
{
   unsigned int curchar, vidmem_off, i;

   outportb(0x3d4, 0x0e);		/* Get cursor Y position	*/
   vidmem_off = inportb(0x3d5);
   vidmem_off <<= 8;
   outportb(0x3d4, 0x0f);		/* And add cursor X position	*/
   vidmem_off += inportb(0x3d5);
   vidmem_off <<= 1;

   while((curchar=*string++))		/* Loop through the string	*/
   {
      switch(curchar)			/* Is it a special character ?  */
      {
         case '\n':			/* Newline found		*/
            vidmem_off = (vidmem_off/160)*160 + 160;
            break;

         case '\r':			/* Carriage return found	*/
            vidmem_off = (vidmem_off/160)*160;
            break;

	case '\t':
	    vidmem_off += 8;
	    break;
	 
	case 8:/* Delete */
	    vidmem_off-=2;
	    VIDEO_MEMORY[vidmem_off] = 0x20;
	    break;

         default:			/* Normal character             */
            VIDEO_MEMORY[vidmem_off++] = curchar;
            VIDEO_MEMORY[vidmem_off++] = 0x07;
            break;
      }

      if(vidmem_off >= 160*25)		/* Are we off-screen ?		*/
      {
         for(i = 0; i < 160*24; i++)	/* Scroll the screen up		*/
         {
            VIDEO_MEMORY[i] = VIDEO_MEMORY[i+160];
         }
         for(i = 0; i < 80; i++)	/* Empty the bottom row		*/
         {
            VIDEO_MEMORY[(160*24)+(i*2)] = 0x20;
            VIDEO_MEMORY[(160*24)+(i*2)+1] = 0x07;
         }
         vidmem_off -= 160;		/* We're on the bottom row	*/
      }
   }

   vidmem_off >>= 1;			/* Set the new cursor position  */
   outportb(0x3d4, 0x0f);
   outportb(0x3d5, vidmem_off & 0x0ff);
   outportw(0x3d4, 0x0e);
   outportb(0x3d5, vidmem_off >> 8);
}

void cls(void)				/* Clear the screen		*/
{
   unsigned int i;

   for(i = 0; i < (80*25); i++)         /* Fill the screen with         */
   {					/* background color		*/
      VIDEO_MEMORY[i*2] = 0x20;
      VIDEO_MEMORY[i*2+1] = 0x07;
   }

   outportb(0x3d4, 0x0f);		/* Set the cursor to the	*/
   outportb(0x3d5, 0);			/* upper-left corner of the	*/
   outportw(0x3d4, 0x0e);		/* screen			*/
   outportb(0x3d5, 0);
}

void printlong(unsigned long i)  /* Convert a dword to a string  */
{
   unsigned char backstr[11], j=0, l=0, m=0;
   unsigned char str[255];

   do					/* Convert string one digit at	*/
   {					/* a time			*/
      backstr[j++] = (i % 10) + '0';	/* Put a digit in backstr	*/
      i /= 10;				/* Next digit			*/
   }					/* And continue until there are */
   while(i);				/* no more digits left		*/

   backstr[j] = '\0';			/* End of the string		*/

   for(l=j-1; m<j; l--)			/* Backstr is backwards (last   */
   {					/* digit first.)  Now we flip   */
      str[m++] = backstr[l];		/* it around...			*/
   }					/* ... and it's ready !!!	*/

   str[j] = '\0';			/* Put the string end on it	*/

   kprint(str);
}