and avoid clear of screen and change of attribute bytes...

[unix-history] / usr / src / sys / i386 / stand / cga.c

/*-
* Copyright (c) 1990 The Regents of the University of California.
* All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* William Jolitz.
*
* %sccs.include.redist.c%
*
*      @(#)cga.c       7.3 (Berkeley) %G%
*/

#include "param.h"

#define COL             80
#define ROW             25
#define CHR             2
#define MONO_BASE       0x3B4
#define MONO_BUF        0xB0000
#define CGA_BASE        0x3D4
#define CGA_BUF         0xB8000

static u_char   att = 0x7 ;
u_char *Crtat = (u_char *)CGA_BUF;

static unsigned int addr_6845 = CGA_BASE;
cursor(pos)
int pos;
{
       outb(addr_6845,14);
       outb(addr_6845+1,pos >> 8);
       outb(addr_6845,15);
       outb(addr_6845+1,pos&0xff);
}

sput(c)
u_char c;
{

       static u_char *crtat = 0;
       unsigned cursorat; u_short was;
       u_char *cp;

       if (crtat == 0) {

               /* XXX probe to find if a color or monochrome display */
               was = *(u_short *)Crtat;
               *(u_short *)Crtat = 0xA55A;
               if (*(u_short *)Crtat != 0xA55A) {
                       Crtat = (u_char *) MONO_BUF;
                       addr_6845 = MONO_BASE;
               }
               *(u_short *)Crtat = was;

               /* Extract cursor location */
               outb(addr_6845,14);
               cursorat = inb(addr_6845+1)<<8 ;
               outb(addr_6845,15);
               cursorat |= inb(addr_6845+1);

               if(cursorat <= COL*ROW) {
                       crtat = Crtat + cursorat*CHR;
                       att = crtat[1]; /* use current attribute present */
               } else  crtat = Crtat;

               /* clean display */
               for (cp = crtat; cp < Crtat+ROW*COL*CHR; cp += 2) {
                       cp[0] = ' ';
                       cp[1] = att;
               }
       }

       switch (c) {

       case '\t':
               do
                       sput(' ');
               while ((int)crtat % (8*CHR));
               break;

       case '\010':
               crtat -= CHR;
               break;

       case '\r':
               crtat -= (crtat - Crtat) % (COL*CHR);
               break;

       case '\n':
               crtat += COL*CHR ;
               break;

       default:
               crtat[0] = c;
               crtat[1] = att;
               crtat += CHR;
               break ;
       }

#ifndef SMALL
       /* implement a scroll */
       if (crtat >= Crtat+COL*ROW*CHR) {
               /* move text up */
               bcopy(Crtat+COL*CHR, Crtat, COL*(ROW-1)*CHR);

               /* clear line */
               for (cp = Crtat+ COL*(ROW-1)*CHR;
                       cp < Crtat + COL*ROW*CHR ; cp += 2)
                       cp[0] = ' ';

               crtat -= COL*CHR ;
       }
#endif

       cursor((crtat-Crtat)/CHR);
}