/* cga.c: Copyright (c) 1989, 1990 William Jolitz. All rights reserved.
 * Written by William Jolitz 9/89
 * Redistribution and use in source and binary forms are freely permitted
 * provided that the above copyright notice and attribution and date of work
 * and this paragraph are duplicated in all such forms.
 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
 * Standalone driver for IBM PC Displays like CGA.
 */

typedef unsigned short u_short;
typedef unsigned char u_char;

#define   CRT_TXTADDR   Crtat
#define   COL      80
#define   ROW      25
#define   CHR      2

u_short *Crtat = ((u_short *)0xb8000); /* 0xb0000 for monochrome */
u_short   *crtat;
u_char   color = 0xe ;
int row;

sput(c) u_char c; {

   if (crtat == 0) {
      crtat = CRT_TXTADDR; bzero (crtat,COL*ROW*CHR);
   }
   if (crtat >= (CRT_TXTADDR+COL*ROW*CHR)) {
      crtat = CRT_TXTADDR+COL*(ROW-1); row = 0;
   }
   switch(c) {

   case '\t':
      do {
         *crtat++ = (color<<8)| ' '; row++ ;
      } while (row %8);
      break;
   case '\010':
      crtat--; row--;
      break;
   case '\r':
      bzero (crtat,(COL-row)*CHR) ; crtat -= row ; row = 0;
      break;
   case '\n':
      if (crtat >= CRT_TXTADDR+COL*(ROW-1)) { /* scroll */
         bcopy(CRT_TXTADDR+COL, CRT_TXTADDR,COL*(ROW-1)*CHR);
         bzero (CRT_TXTADDR+COL*(ROW-1),COL*CHR) ;
         crtat -= COL ;
      }
      crtat += COL ;
      break;
   default:
      *crtat++ = (color<<8)| c; row++ ;
      break ;
   }
}